METOHD FOR SAFELY MANAGING ELECTRIC MOTOR ACTIVATION AND DEACTIVATION, AND CORRESPONDING APPLIANCE

Abstract

 A washing and/or drying appliance (100) is proposed. The appliance comprises:
an electric load (205),
a driving arrangement (210,215,C) for driving the electric load (205), the driving arrangement (210,215,C) having first (T_205,IN1) and second (T_205,IN2) terminals coupleable, respectively, to a line terminal (T_L) and to a neutral terminal (T_N) providing a reference voltage (V_CC),
an inrush current limiting device (R_FUSE;R_NTC) and a switching device (RL;RL₁) between the reference terminal (T_N) and the second terminal (T_205,IN2) of the driving arrangement (210,215,C), the switching device (RL;RL₁) being operable in first or second states preventing or allowing, respectively, an electric current to flow through the inrush current limiting device (R_FUSE,R_NTC), and
a sensing network (R_PD) for sensing the first or second states of the switching device (RL;RL₁) and for providing a corresponding state signal (S_STATE;S*_STATE), the sensing network (R_PD) having a first terminal (T_RPD,1), and a second terminal (T_RPD,2) coupled to a reference terminal providing a further reference voltage (GND) lower than the reference voltage (V_CC), wherein, during sensing:
in the first state of the switching device (RL;RL₁) the reference terminal (T_N) and the first terminal (T_RPD,1) of the sensing network (R_PD) being coupled to each other such that the first terminal (T_RPD,1) of the sensing network (R_PD) receives the reference voltage (V_CC) and the state signal (S_STATE;S*_STATE) takes a first level (S_STATE,H) equal to the reference voltage (V_CC), in the second state the state signal (S_STATE, S*_STATE) taking a second level (S_STATE,I;S_STATE,L) lower than the first level (S_STATE,H).

Description

Field of the invention

[0001] The present invention generally relates to electric appliances, such as washing, drying, washing/drying, dishwashing appliances, both for domestic and professional use. More particularly, the present invention relates to a circuit and a method for safely managing activation/deactivation of electric motors in such appliances.

Background of the invention

[0002] Nowadays most of electric appliances, hereinafter appliances, make use of electric motors. In case of a laundry washing appliance, a laundry washing/drying appliances and a laundry drying appliance, the electric motor is intended to rotate a rotatable drum (i.e. the rotatable container arranged inside the appliance wherein a laundry load is placed/housed in order to be washed and/or dried).

[0003] In order to activate/deactivate the electric motor, the appliance typically comprises electrically-operated switching devices and a power conversion/driving system for converting an AC supply voltage into a DC supply voltage allowing driving of the electric motor.

[0004] According to known solutions, the power conversion/driving system comprises a rectifying arrangement and a bulk capacitor for providing said DC supply voltage, and a driving arrangement, fed with said DC supply voltage, for driving the electric motor (e.g., for controlling activation/deactivation thereof). Due to inherently low input resistance exhibited by the power conversion/driving system, especially when the bulk capacitor is initially discharged, large surge currents (or inrush currents) may arise, which are very stressful to power conversion/driving system.

[0005] Inrush current limiting devices (e.g. including negative temperature coefficient (NTC) thermistor or resistor) connected between the AC power supply and the power conversion/driving system and electrically-operated switching devices in parallel with the inrush current limiting devices, are often used to mitigate the inrush current during starting.

Summary of invention

[0006] The Applicant has realized that the known solutions are not satisfactory for modem requirements.

[0007] Indeed, each switching device which the known solutions makes use of is prone to errors (e.g., absence of switching), thus impairing appliance operation. Some known solutions provide sensing arrangements for sensing the switching state of the switching devices, however these sensing arrangements provide high-voltage sensing (as typically based on sensing provision/absence of the AC supply voltage through the switching device), which translates into power consumptions not compatible with nowadays restrictive powers saving requirements.

[0008] Due to high power consumption of the sensing arrangement, only some of the switching devices are typically sensed (low sensing activity), thus exposing the appliance to reliability issues when failures of the non-sensed switching devices arise.

[0009] Low sensing activity also involves that some critical procedures (such as electric motor activation and deactivation procedures) are handled by the appliance in a manner not oriented to avoid safety risks for the user.

[0010] One or more aspects of the present invention are set out in the independent claims, with advantageous features of the same invention that are indicated in the dependent claims.

[0011] An aspect of the present invention relates to a washing and/or drying appliance. The appliance comprises:

an electric load,

a driving arrangement for driving the electric load, the driving arrangement having first and second terminals coupleable, respectively, to a line terminal and to a neutral terminal providing a reference voltage,

an inrush current limiting device and a switching device between the reference terminal and the second terminal of the driving arrangement, the switching device being operable in first or second states preventing or allowing, respectively, an electric current to flow through the inrush current limiting device, and

a sensing network for sensing the first or second states of the switching device and for providing a corresponding state signal, the sensing network having a first terminal, and a second terminal coupled to a reference terminal providing a further reference voltage lower than the reference voltage. During sensing, in the first state of the switching device the reference terminal and the first terminal of the sensing network being coupled to each other such that the first terminal of the sensing network receives the reference voltage and the state signal takes a first level equal to the reference voltage, in the second state the state signal taking a second level lower than the first level.

[0012] According to an embodiment of the present invention, in the second state of the switching device the reference terminal and the first terminal of the sensing network are coupled to each other with interposition of the inrush current limiting device, whereby the second level of the state signal is between the first the reference voltage and the further reference voltage according to a partition between the inrush current limiting device and the sensing network.

[0013] According to an embodiment of the present invention, in the second state of the switching device the first terminal of the sensing network is electrically floating, whereby the second level of the state signal is at the further reference voltage by pull-down action of the sensing network.

[0014] According to an embodiment of the present invention, the switching device has a first contact electrically coupled, during sensing, to the sensing network, a second contact coupled to the second terminal of the driving arrangement, and a third contact electrically coupled to the reference terminal and contacting the first or second contacts in first or second states, respectively, of the switching device.

[0015] According to an embodiment of the present invention, the switching device has a first contact electrically floating, a second contact, and a third contact electrically coupled to the reference terminal and contacting the first or second contacts in first or second states, respectively, of the switching device. The appliance also comprises a further switching device operable in first or second states electrically coupling the second contact of the switching device to the first terminal of the sensing network or to the second terminal of the driving arrangement, respectively.

[0016] According to an embodiment of the present invention, the first terminal of the sensing network is coupled, during sensing, to the second contact of the switching device, in the second state of the further switching device the state signal taking a third level equal to the further reference voltage.

[0017] According to an embodiment of the present invention, the sensing network is a resistive network.

[0018] According to an embodiment of the present invention, the appliance further comprises a filtering arrangement for suppressing disturbances from the state signal.

[0019] According to an embodiment of the present invention, the inrush current limiting device is a fusible resistor or a negative temperature coefficient thermistor.

[0020] According to an embodiment of the present invention, the electric load is an electric motor, for example a "Variable-Frequency Drive" motor or a Brushless DC motor

[0021] According to an embodiment of the present invention, the appliance is a laundry washing appliance intended to perform only laundry washing operations, or a laundry drying appliance intended to perform only laundry drying operations, or a laundry washing/drying appliance intended to perform both laundry washing and laundry drying operations.

[0022] According to an embodiment of the present invention, the appliance further comprises a mechanical door-lock device for mechanically locking an appliance door thereby preventing door opening when the electric load is activated.

[0023] Another aspect of the present invention relates to a method for operating a washing and/or drying appliance. The appliance comprises:

an electric motor and a driving arrangement for driving it, the driving arrangement being coupleable to a line terminal and to a neutral terminal providing a reference voltage,

between the neutral terminal and the driving arrangement, an inrush current limiting device and a switching device, the switching device being operable between first and second states allowing and preventing, respectively, an electric current to flow through the inrush current limiting device, and

a sensing arrangement configured for sensing the first or second states of the switching device and for providing a corresponding state signal, in the first state of the switching device the state signal taking a first level equal to the reference voltage, and in the second state of the switching device the state signal taking a second level lower than the first level.

[0024] The method comprises, under the control of a control unit of the appliance and in response to a motor activation request:

if the state signal takes the second level, feeding the driving arrangement with a first electric current limited by the inrush current limiting device, and

if communication between the electric motor and the driving arrangement is active, operating the switching device into the second state thereby allowing a second electric current not limited by the inrush current limiting device to be fed to the driving arrangement, and activating the electric motor.

[0025] According to an embodiment of the present invention, the appliance further comprises a mechanical door-lock device for mechanically locking an appliance door thereby preventing door opening when the electric motor is activated. The method further comprises enabling mechanical door locking, said feeding the driving arrangement with a first electric current limited by the inrush current limiting device being performed if mechanical door locking is enabled.

[0026] According to an embodiment of the present invention, the appliance further comprises a further switching device operable in first or second states electrically coupling the switching device to the sensing arrangement or to the driving arrangement, respectively, in the first state of the further switching device the state signal taking the first or second levels according to the first or second states, respectively, of the switching device. Said enabling mechanical door locking if the state signal takes the second level comprises:

operating the switching device in the first state,

if the state signal takes the first level, operating the switching device in the second state, and

if the state signal takes the second level, performing said enabling mechanical door locking.

[0027] According to an embodiment of the present invention, in the second state of the further switching device the state signal takes a third level lower than the first and second levels. The method further comprises, after said enabling mechanical door locking:

if mechanical door locking is enabled, operating the further switching device in the second state, and

performing said operating the switching device into the second state if communication between the electric motor and the driving arrangement is active and if the state signal takes the third level.

[0028] According to an embodiment of the present invention, the method further comprises, in response to a motor deactivation request:

if motor deactivation has occurred, operating the further switching device into the first state, and

if the state signal takes the second level, operating the switching device into the first state and disenabling mechanical door locking.

[0029] According to an embodiment of the present invention, the method further comprises, in response to a motor deactivation request:

if motor deactivation has occurred, operating the switching device into the first state, and

if the state signal takes the first level and if a predefined time period has passed since motor deactivation request, disenabling mechanical door locking.

Brief description of the annexed drawings

[0030] These and other features and advantages of the present invention will be made apparent by the following description of some exemplary and non limitative embodiments thereof; for its better intelligibility, the following description should be read making reference to the attached drawings, wherein:

Figure 1 shows a perspective view of an appliance wherein the present invention may be applied;

Figure 2 schematically shows a portion of a circuit system of the appliance according to an embodiment of the present invention;

Figures 3 and 4 show simplified flowcharts of respective procedures implemented by the circuit system of Figure 2 according to an embodiment of the present invention;

Figure 5 schematically shows a portion of a circuit system of the appliance according to another embodiment of the present invention, and

Figures 6 and 7 show simplified flowcharts of respective procedures implemented by the circuit system of Figure 5 according to an embodiment of the present invention.

Detailed description of preferred embodiments of the invention

[0031] Referring now to the drawings, Figure 1 schematically shows an appliance 100, for example for domestic use (i.e., a household appliance), wherein the present invention may be applied. The appliance 100 may for example be a laundry washing appliance intended to perform only laundry washing operations (i.e., without laundry drying operations), a laundry drying appliance intended to perform only laundry drying operations (i.e., without laundry washing operations), or a laundry washing/drying appliance intended to perform both laundry washing and laundry drying operations (as generically illustrated in the figure, and to which reference will be made in the following by way of a non-limiting example only).

[0032] The appliance 100 preferably comprises a substantially parallepiped-shaped cabinet 105, which encloses an inner compartment.

[0033] In the exemplarily considered appliance 100 (which is intended to perform both laundry washing and laundry drying operations), the inner compartment accommodates a tub (not visible), adapted to be filled with washing water, and a (e.g., perforated) rotatable drum 110 mounted therein (in either a horizontal or vertical orientation) adapted to house the laundry to be treated (i.e., the laundry to be washed and/or dried, in the example at issue). Anyway, according to the considered appliance (and, hence, according to the treatment the appliance is intended/designed to perform), the inner compartment may accommodate, instead of the tub and the rotatable drum 110, any suitable treatment chamber (e.g., a rotatable, non-perforated drum in case of a laundry drying appliance).

[0034] The inner compartment (i.e., the rotatable drum 110) is accessible through an access door 115 (shown in a closed configuration), preferably provided on a front panel 105_F of the cabinet 105 for loading/unloading the laundry.

[0035] The inner compartment also accommodates, not visible in such a figure, a number of well-known electronic, electro-hydraulic and/or electro-mechanical components, which form (as a whole) a circuit system allowing operation of the appliance 100.

[0036] Hereinafter, reference will be also made to Figure 2, which schematically shows a portion of a circuit system 200 according to an embodiment of the present invention. In the following, in order to take into account possible circuit system variants, all falling within the scope of the present invention, the term coupling will be used for denoting both direct and indirect coupling (unless explicitly referring to direct coupling, when relevant for the present invention).

[0037] The circuit system 200 comprises one or more electric loads, such has the electric load 205, for example an electric motor for drum rotation. Preferably, although not necessarily, the electric motor 205 is a "Variable-Frequency Drive" (VFD) motor or a Brushless DC motor, so that control of drum rotation speed (e.g., according to an actual laundry load, and/or to an actual amount of washing water within the rotatable drum 110) is possible. However, as will be understood from the following description, the present invention may be applied for any electric load (for example, an electric heater, a drain or recirculation pump, a fan).

[0038] In the considered embodiment, the circuit system 200 also comprises a driving arrangement, generally configured for driving the electric motor 205. In order to achieve that, the driving arrangement preferably comprises a motor module 210, powered between first V_DC1 and second V_DC2 DC supply voltages, for controlling activation and deactivation of the electric motor 205, as well as a power conversion arrangement for providing said DC supply voltages V_DC1, V_DC2 according to an AC supply voltage selectively received from supply (e.g., line) T_L and reference (e.g., neutral) T_N terminals of an AC power supply.

[0039] Preferably, the power conversion module comprises a rectifying circuit (e.g., a diodes bridge) 215, having two input terminals T_215,IN1,T_215,IN2 (selectively coupleable to the line T_L and neutral T_N terminals, respectively) for receiving the AC supply voltage and two output terminals T_215,OUT1,T_215,OUT2 for providing pulsed DC voltages (deriving from full-wave rectification of the AC supply voltage), and a smoothing (or bulk) capacitor C, whose terminals T_C1,T_C2 are electrically coupled to the output terminals T_215,OUT1,T_215,OUT2, respectively, of the rectifying circuit 215 for smoothing the pulsed DC voltages into said DC supply voltages V_DC1,V_DC2. By virtue of the considered implementation, the input terminals T_215,IN1,T_215,IN2 of the rectifying circuit 215 also represent, by the logical viewpoint, input terminals of the driving arrangement as a whole (although the motor module 210, typically provided as a dedicated printed circuit board, is structurally separated from the power conversion module 215,C), the driving arrangement 210,215,C being thus selectively coupleable to the line T_L and neutral T_N terminals by means of the input terminals T_215,IN1,T_215,IN2, respectively.

[0040] The circuit system 200 also comprises an AC-DC conversion circuit (denoted by the reference CC in the figure) comprising transforming, rectifying and regulating components for receiving the AC supply voltage and providing one or more further DC voltages, such as a lower reference, or ground, voltage GND (e.g., 0V), and an upper reference voltage Vcc (e.g., a 5V DC voltage with respect to the ground voltage GND) for powering electronic components of the appliance 100 (as mentioned in the following). As visible in the figure, the neutral terminal T_N is preferably set at the upper reference voltage Vcc (so as to allow proper driving of power components of the appliance 100, e.g. triacs, not shown).

[0041] An inrush current limiting device R_NTC (better discussed in the following) is provided between the neutral terminal T_N and the input terminal T_205,IN2 of the rectifying circuit 215 (i.e., of the driving arrangement 210,215,C) in order to limit large peak surge currents, or inrush currents, flowing through (thus electrically stressing) the rectifying arrangement 215 and the bulk capacitor C (especially when the bulk capacitor C is initially discharged).

[0042] Selective coupling between line T_L and neutral T_N terminals and the rectifying circuit 215 is achieved by means of a number of electrically-operated switching devices. As illustrated, a safety switch (e.g., a door switch) SW_L is provided between the line terminal T_L and the input terminal T_215,IN1 of the rectifying arrangement 215, whereas a switching arrangement is provided between the neutral terminal T_N and the input terminal T_215,IN2 of the rectifying arrangement 215.

[0043] According to the exemplary illustrated embodiment, the switching arrangement comprises a (e.g., electromagnetic) relay RL₁ having bypass functions (thus, referred to as bypass relay RL₁ hereinafter) electrically coupled to the neutral terminal T_N, and a (e.g., electromagnetic) relay RL₂ having safety functions (thus, referred to as safety relay RL₂ hereinafter) provided between the bypass relay RL₁ and the input terminal T_215,IN2 of the rectifying circuit 215 (the bypass RL₁ and safety RL₂ relays being assumed preferably structurally similar to each other).

[0044] For the purposes of the present disclosure, the bypass RL₁ and safety RL₂ relays comprise respective contacts C_A,RL1,C_B,RL1,C_C,RL1 and C_A,RL2,C_B,RL2,C_C,RL2, as well as a coil of wire wrapped around an iron core. A central contact of each relay, e.g. the contact C_B,RL1,C_B,RL2, is movable with respect to the other, or fixed, (mechanically separated and electrically insulated) side contacts of the same relay (i.e. the side contacts C_A,RL1,C_C,RL1 and C_A,RL2,C_C,RL2, respectively). In absence of current across the coil (relay de-energization), the central contact C_B,RL1,C_B,RL2 of each relay RL₁,RL₂ is electrically coupled to a respective side contact, e.g. the contact C_A,RL1,C_A,RL2 (and an air gap, and hence electrical insulation, is established between the central contact C_B,RL1,C_B,RL2 and the opposite side contact C_C,RL1,C_C,RL2). When instead an electric current is passed through the coil (relay energization), a magnetic field is generated that activates movement of the central contact C_B,RL1,C_B,RL2 from the side contact C_A,RL1,C_A,RL2 to the respective side contact C_C,RL1,C_C,RL2 (until mechanical and electrical contacting is established therebetween). Thus, in the considered embodiment, the bypass RL₁ and safety RL₂ relays are in a first, de-energized, state wherein the central contacts C_B,RL1,C_B,RL2 contact the side contacts C_A,RL1,C_A,RL2, respectively, and are operable in a second, energized, state wherein the central contacts C_B,RL1,C_B,RL2 contact the side contacts C_C,RL1,C_C,RL2, respectively.

[0045] In the exemplary illustrated embodiment, the side contact C_A,PL1 of the bypass relay RL₁ is floating, whereas the central contact C_B,RL1 of the bypass relay RL₁ is electrically coupled to the neutral terminal T_N (so as to contact the side contact C_A,RL1 or the side contact C_C,RL1 in the de-energized or energized states, respectively, of the bypass relay RL₁). The side C_A,RL2,C_C,RL2 and central C_B,RL2 contacts of the safety relay RL₂ are instead electrically coupled to the input terminal T_215,IN2 of the rectifying arrangement 215, to a sensing arrangement 220 (as discussed in the following) and to the side contact C_C,RL1 of the bypass relay RL₁, respectively. In other words, in the de-energized state of the safety relay RL₂, the side contact C_C,RL1 of the bypass relay RL₁ is electrically coupled to the sensing arrangement 220 (through the side C_A,RL2 and central C_B,RL2 contacts of the safety relay RL₂), and in the energized state of the safety relay RL₂ the side contact C_C,RL1 of the bypass relay RL₁ is electrically coupled to the input terminal T_215,IN2 of the rectifying circuit 215, whereas the bypass relay RL₁ in the energized state identifies said first configuration of the switching arrangement (i.e., electric current being prevented from flowing through the inrush current limiting device R_NTC) and the bypass relay RL₁ in the de-energized states identifies said second configuration of the switching arrangement (i.e., electric current being allowed to flow through the inrush current limiting device R_NTC).

[0046] The door switch SW_L can be switched between an opened, or off, condition electrically decoupling the line terminal T_L and the input terminal T_215,IN2 of the rectifying arrangement 215 from each other thereby preventing, in door-opened configuration, energization of the electric motor 205 (and/or of any other electric loads downstream the door switch SW_L), and a closed, or on, condition. When the door switch SW_L is instead in the closed condition, electrical coupling between the line terminal T_L and the input terminal T_215,IN2 of the rectifying arrangement 215 is established, and mechanical lock of the door 115 is commanded (e.g., by means of a proper door-lock command, not shown, provided to a proper mechanical door-lock device, also not shown). Preferably, such a mechanical lock is provided to prevent opening of the door for safety reasons, e.g. when the electric motor 205 is activated, when washing or rinsing water is provided within the tub, when a dangerous temperature in the inner compartment is detected, or when the drum 110 is still rotating.

[0047] Thus, when the door switch SW_L is in the opened condition, no activation of the electric motor 205 arises (regardless of the bypass RL₁ and safety RL₂ relays states, either energized or de-energized states), and when the door switch SW_L is in the closed condition, energization of the electric motor 205 can take place only upon energization of the safety relay RL₂ (thus allowing the AC supply voltage from the line T_L and neutral T_N terminals to be fed across the input terminals T_215,IN1,T_215,IN1 of the rectifying arrangement 215).

[0048] The inrush current limiting device R_NTC may be a fusible resistor or, as in the exemplary considered embodiment, a negative temperature coefficient (NTC) thermistor electrically coupled in parallel with the bypass relay RL₁. According to the exemplary illustrated embodiment, the NTC thermistor R_NTC is electrically coupled between the central C_B,RL1 and side C_C,RL1 contacts of the bypass relay RL₁.

[0049] Basically, the NTC thermistor R_NTC is a resistive component whose resistance decreases as its temperature increases. During startup, with the door switch SW_L in the closed condition, the bypass relay RL₁ in the de-energized state and the safety relay RL₂ in the energized state (so that the neutral terminal T_N is electrically coupled to the input terminal T_215,IN2 of the rectifying arrangement 215 through the NTC thermistor R_NTC and the safety relay RL₂, i.e. the central C_B,RL2 and side C_C,RL2 contacts thereof), the temperature of the NTC thermistor R_NTC is cold and its resistance is high, and a relatively low starting current is allowed to flow therethrough. As operation continues, the temperature of the NTC thermistor R_NTC increases (due to starting current flowing therethrough) and its resistance decreases, thereby an increasing amount of starting current is allowed to flow therethrough. After startup completing or preset time elapsing, the bypass relay RL₁ is operated into the energized state (i.e., central contact C_B,RL1 of the bypass relay RL₁ being moved into contact with the side contact C_C,RL1 thereof), thus bypassing (i.e., substantially short-circuiting) the NTC thermistor R_NTC and allowing a working current (substantially depending on the AC supply voltage and on the experienced impedance) to be fed to the rectifying arrangement 215 (through the bypass relay RL₁, i.e. the central C_B,RL1 and side C_C,RL1 contacts thereof, and the safety relay RL₂, i.e. the central C_B,RL2 and side C_C,RL2 contacts thereof).

[0050] As mentioned above, the circuit system 200 also comprises a sensing arrangement 220, selectively coupleable to the side contact C_A,RL2 of the safety relay RL₂. Broadly speaking, the sensing arrangement 220 is configured for sensing the first or second states (i.e., the energized or de-energized states) of the bypass relay RL₁, as well as the energized or de-energized states of the safety relay RL₂ (being the sensing allowed/prevented based on the de-energized/energized state of the safety relay RL₂), and for providing a corresponding signal S_STATE (hereinafter, state signal). As better discussed herebelow, by virtue of the considered circuit system 200 implementation, the state signal S_STATE may advantageously take three different levels according to the bypass RL₁ and safety RL₂ relays states, namely a low level S_STATE,L equal to the lower reference voltage GND, a high level S_STATE,H equal to the upper reference voltage V_CC, and an intermediate level S_STATE,L between the low S_STATE,L and high S_STATE,H levels.

[0051] In order to achieve that, the sensing arrangement 220 comprises a sensing network, for example a (e.g., resistive) pull-down network R_PD (schematically represented as a single resistor in the figure, and referred to as pull-down resistor in the following), having a first terminal T_RPD,1 providing the state signal S_STATE and adapted to be electrically coupled to the side contact C_C,RL2 of the safety relay RL₂ (and hence, to the side contact C_C,RL1 of the bypass relay RL₁) and a second terminal T_RPD,2 receiving the lower reference voltage GND.

[0052] Preferably, as illustrated, a filtering arrangement (e.g., a low pass filter) F_LP is provided for suppressing possible disturbances from (i.e., associated with) the state signal S_STATE- anyway, as should be readily understood, embodiments are possible wherein the filtering arrangement F_LP is not provided, in which case the state signal S_STATE may be directly taken from the first terminal T_RPD,1 of the pull-down resistor R_PD.

[0053] As mentioned above, the safety relay RL₂ is operable in a first, energized, state electrically coupling the side contact C_C,RL1 of the bypass relay RL₁ to sensing arrangement 220 (i.e., to the pull-down network R_PD) or in a second, de-energized, state electrically coupling the side contact C_C,RL1 of the bypass relay RL₁ to the input terminal T_215,IN2 of the driving arrangement 210,215,C, respectively. Preferably, as illustrated, the actual sensing start is controlled by means of an electrically-operated switching device (e.g., a MOS transistor) 225 between the side terminal C_C,RL2 of the safety relay RL₂ and the first terminal T_RPD,1 of the pull-down resistor R_PD- with the sensing start that may take place, as herein exemplary considered, according to closed/opened states of the MOS transistor 225 controlled according to corresponding values of a control signal S₂₂₅.

[0054] During sensing, the following configurations of the bypass RL₁ and safety RL₂ relays states may be discriminated (and signaled, through the respective high S_STATE,H, low S_STATE,L or intermediate S_STATE,I levels of the state signal S_STATE):

Bypass relay RL₁ in the energized state and safety relay RL₂ in the de-energized state.

[0055] In this configuration, the NTC thermistor R_NTC is short-circuited (bypassed) by the bypass relay RL₁, thus the first terminal T_RPD,1 of the pull-down resistor R_PD and the neutral terminal T_N are both at the upper reference voltage V_CC. Otherwise stated, the neutral terminal T_N and the first terminal T_RPD,1 of the pull-down resistor R_PD are coupled to each other such that the first terminal T_RPD,1 of the pull-down resistor receives the upper reference voltage V_CC In other words, a direct coupling (unless unavoidable parasitic components - such as wires, contacts C_B,RL1,C_C,RL1 and MOS transistors 225 parasitic resistances) is established between the neutral terminal T_N and the pull-down resistor R_PD. Thus, the state signal S_STATE takes the high level S_STATE,H.

Safety relay RL₂ in the energized state (bypass relay RL₁ either in the energized or de-energized states).

[0056] In this configuration, the central contact C_B,RL2 of the safety relay RL₂ is electrically coupled to the side contact C_C,RL2, the side contact coupled to the sensing arrangement 220 (i.e., the side contact C_A,RL2) being instead floating (i.e., no direct or indirect coupling between the neutral terminal T_N and the pull-down resistor R_PD takes place). As a result of that, by effect of the pull-down resistor R_PD, the first terminal T_RPD,1 of the pull-down resistor R_PD is pulled-down to the lower reference voltage GND. Thus, the state signal S_STATE takes the low level S_STATE,L.

Bypass RL₁ and safety RL₂ relays in the de-energized state

[0057] In this configuration, the neutral terminal T_N and the first terminal T_RPD,1 of the pull-down resistor R_PD are coupled to each other with interposition of the NTC thermistor R_NTC. Thus, no direct coupling between the neutral terminal T_N and the pull-down resistor R_PD takes place, and a conductive path is generated from the neutral terminal T_N and the pull-down resistor R_PD through the NTC thermistor R_NTC and the safety relay RL₂ (i.e., the central C_B,RL2 and side C_C,RL2 contacts thereof). As a result of that, the upper reference voltage V_CC at the neutral terminal T_N experiences a partition between the NTC thermistor R_NTC and the pull-down resistor R_PD (omitting possible resistive effects of the bypass RL₁ and safety RL₂ relays and/or of the transistor 225). Hence, the state signal S_STATE takes the intermediate level S_STATE,I (whose value depends on NTC thermistor R_NTC and pull-down resistor R_PD sizing, not limiting for the present invention).

[0058] As better discussed in the following, when the state signal S_STATE takes levels different from the expected one in a current (expected) bypass RL₁ and safety RL₂ relays configuration, other problems to the bypass relay RL₁ or to the safety relay RL₂ or to the NTC thermistor R_NTC or to the circuit system may also be inferred (such as contacts and/or resistors wear).

[0059] The circuit system 200 further comprises a control unit 230, for example a microcontroller/microprocessor. As conceptually represented in the figure, the control unit 230 is configured to receive the state signal S_STATE (or, in the considered example, a filtered version thereof) from the sensing arrangement 220 (i.e., the first terminal T_RPD,1 of the pull-down resistor R_PD) and standard error/control messages MSG from the motor module 210, and, accordingly, to control the door switch SW_L, the bypass RL₁ and safety RL₂ relays and the MOS transistor 225 (e.g., by means of respective control signals S_SWL,S_RL1,S_RL2,S₂₂₅) and to command motor module 210 (and, hence, electric motor 205) activation/deactivation (e.g., by means of command signals S_COMM). The control unit 230 is herein assumed to be capable of commanding mechanical lock of the door (by means of the door lock command), and determining whether such a mechanical lock has taken place correctly.

[0060] The illustrated circuit system 200 allows achieving a low-voltage sensing, which makes it highly power-saving and reliable. Moreover, the circuit system 200 makes use of a single sensing arrangement for sensing the states of both bypass RL₁ and safety RL₂ relays, thus some critical procedures (such as electric motor activation and deactivation procedures, discussed below) may be handled by the appliance 100 in a manner totally oriented to avoid safety risks for the user, while substantially unaffecting power consumption.

[0061] Figure 3 shows a simplified flowchart of a motor activation procedure 300, carried out under the control of the control unit 230 in response to a motor activation request, according to an embodiment of the present invention. Broadly speaking, the motor activation procedure 300 is aimed at activating the electric motor 205 if, from a default configuration wherein the bypass RL₁ and safety RL₂ relays are both in the de-energized state (i.e., the state signal S_STATE takes the intermediate level S_STATE,I), mechanical door locking is enabled, the starting current (i.e., the electric current limited by the NTC thermistor R_NTC) is correctly fed to the driving arrangement 205,210,C, communication between the electric motor 205 and the driving arrangement 205,210,C is active, and the working current is allowed to be fed to the driving arrangement 205,210,C (i.e., bypass relay RL₁ in the de-energized state and safety relay RL₂ in the energized state). In addition, as better discussed herebelow, the motor activation procedure 300 also performs check phases aimed at evaluating bypass relay RL₁, safety relay RL₂ or NTC thermistor R_NTC failures.

[0062] The motor activation procedure 300 starts by operating the bypass relay RL₁ into the energized state (action block 305), and by checking (decision block 310) whether S_STATE=S_STATE,H - which means that bypass relay RL₁ energization has taken place correctly, the safety relay RL₂ is in the de-energized state (as expected from the last motor deactivation procedure), and no malfunction affect the NTC resistor R_NTC.

[0063] In the negative case (exit branch N of the decision block 310), the motor activation procedure 300 ends without that motor activation takes place (activity block 360), possibly by displaying an error code and/or emitting a sound alarm signal indicative of detected or inferred errors. Among the inferable errors, a low level S_STATE,L of the state signal S_STATE (instead of the expected high level S_STATE,L) may denote NTC thermistor R_NTC open-circuit or undesired energized state the safety relay RL₂, an intermediate level S_STATE,L of the state signal S_STATE (instead of the expected high level S_STATE,H) may denote a bypass relay RL₁ energization failure, whereas a level different from the high S_STATE,H, intermediate S_STATE,I and low S_STATE,L levels may denote a generic error of the sensing arrangement 220.

[0064] Otherwise (exit branch Y of the decision block 310), the motor activation procedure 300 continues by operating the bypass relay RL₁ into the de-energized state (activity block 315) and by checking (decision block 320) whether S_STATE=S_STATE,I (i.e., whether the bypass RL₁ and safety RL₂ relays are both in the de-energized state and no malfunction affect the NTC resistor R_NTC).

[0065] In the negative case (exit branch N of the decision block 320), the motor activation procedure 300 ends without that motor activation takes place (activity block 360), possibly by displaying an error code and/or emitting a sound alarm signal indicative of detected or inferred errors. Among the inferable errors, a high level S_STATE,H of the state signal S_STATE (instead of the expected intermediate level S_STATE,I) may denote NTC thermistor R_NTC short-circuit or bypass relay RL₁ de-energization failure, a low level S_STATE,L of the state signal S_STATE (instead of the expected intermediate level S_STATE,I) may denote NTC thermistor R_NTC open-circuit or undesired energized state the safety relay RL₂, whereas a level different from the high S_STATE,H, intermediate S_STATE,I and low S_STATE,L levels may denote, as before, a generic error of the sensing arrangement 220. Undesired energized state of the safety relay RL₂ is the least likely error that could affect the circuit system 200 at decision blocks 310 and 320 (indeed, as better understood from the following description, safety relay RL₂ de-energization state is ensured before ending each motor deactivation procedure).

[0066] Back to decision block 320, if instead the state signal S_STATE takes the intermediate level S_STATE,L (exit branch Y of the decision block 320), the motor activation procedure 300 continues by switching the door switch SW_L into the closed configuration (by means of the signal S_SWL, so that electrical coupling between the line terminal T_L and the input terminal T_215,IN2 of the rectifying arrangement 215 is established), and by providing the door lock command to the mechanical lock of the door (activity block 325), thereafter correct door locking is checked at the decision block 330.

[0067] If mechanical lock of the door has failed, exit branch N of the decision block 330, the motor activation procedure 300 ends (activity block 360), as the possibility of opening the door 115 when the electric motor 105 is activated is not prevented. Otherwise, exit branch Y of the decision block 330, it meaning that the electric motor 105 can be activated without risks for any user accidentally tenting to open the door 115, the motor activation procedure 300 goes on by operating the safety relay RL₂ into the energized stated (activity block 335) - thereby allowing the AC supply voltage to be fed across the input terminals T_205,IN1,T_205,IN2 of the rectifying arrangement 215 and a limited inrush current (i.e., the inrush current limited by the NTC thermistor R_NTC) to softly charge the bulk capacitor C at the DC supply voltages V_DC1,V_DC2 - and by checking (decision block 340) whether safety relay RL₂ energization has taken place correctly - i.e., whether S_STATE=S_STATE,L indicating that the bypass RL₁ and safety RL₂ relays are in the de-energized and energized states, respectively, and no malfunction affects the NTC thermistor R_NTC.

[0068] In the negative case (exit branch N of the decision block 340), the motor activation procedure 300 ends (activity block 360), possibly by displaying proper error codes and/or emitting alarm signals indicative of the detected error.

[0069] In the positive case (exit branch Y of the decision block 340), another check is performed for determining (decision block 345) correct, active and functioning communication between the electric motor 205 and the motor module 210 by means of the standard error/control messages MSG. If correct, active and functioning communication between the electric motor 205 and the motor module 210 is determined (exit branch Y of the decision block 345), the bypass relay RL₁ is operated into the energized state (activity block 350) - so that the working current substantially depending on the AC supply voltage and on the experienced impedance is entirely fed to the rectifying arrangement 215) - and motor module 210 activation (and, hence, electric motor 205 correct and safe activation) is commanded by means of the command signals S_COMM (activity block 355), otherwise (exit branch N of the decision block 345) the motor activation procedure 300 ends (activity block 360) possibly by displaying proper error codes and/or emitting alarm signals indicative of the detected error. As visible in the figure, the motor activation procedure 300 ends in any case after electric motor 205 activation.

[0070] Turning now to Figure 4, it shows a simplified flowchart of a motor deactivation procedure 400 carried out by the control unit 230 in response to a motor deactivation request, according to an embodiment of the present invention. Broadly speaking, the motor deactivation procedure 400 is aimed at disenabling mechanical door locking only if, upon motor deactivation has occurred, the safety relay RL₂ is operated into the de-energized state (i.e., state signal S_STATE taking the intermediate level S_STATE,I, so that no electric current is allowed to flow to the driving arrangement 210,215,C any longer), and the bypass relay RL₁ is operated into the de-energized state (for consistency with a following motor activation procedure, wherein, as discussed above, the bypass RL₁ and safety RL₂ relays in the de-energized states represent the preferred default starting configuration for inferring failures).

[0071] The motor deactivation procedure 400 starts by commanding, by means of the command signals S_COMM, deactivation of the electric motor 205 (activity block 405) in response to the motor deactivation request, and by operating the safety relay RL₂ into the de-energized state (action block 420) as soon as the electric motor 205 has stopped or, anyway, after a predefined time interval has elapsed from the command signals S_COMM. This is conceptually represented in the figure by loop connection between a decision block 410 (wherein electric motor 205 stopping is checked) and a decision block 415 (wherein predefined time interval elapsing is checked). Briefly, the motor deactivation procedure 400 keeps running the decision blocks 410,415 as long as the electric motor 205 has not stopped (exit branch N of the decision block 410) and the predefined time interval has not elapsed (exit branch N of the decision block 415). Instead, if (i.e., as soon as) the electric motor 205 has stopped (exit branch Y of the decision block 410), or the predefined time interval has elapsed without that the electric motor 205 has stopped (exit branch Y of the decision block 415), the safety relay RL₂ is operated into the de-energized state (activity block 420). As should be understood, elapsing of the predefined time interval might mean that communication between the electric module 205 and the motor module 210 is temporary or permanently prejudiced (in which case the motor module 210 may not have deactivated the electric motor 205, or may not have received confirmation about electric motor 205 stopping), so that operating the safety relay RL₂ into the de-energized state allows safely interrupting electric motor 205 powering in any case.

[0072] The motor deactivation procedure 400 goes on by checking (decision block 425) whether the bypass relay RL₂ de-energization has taken place correctly and the bypass relay RL₁ is energized, as expected - i.e., whether the bypass RL₁ and safety RL₂ relays are in the energized and de-energized states, respectively, namely whether S_STATE=S_STATE,H.

[0073] In the negative case (exit branch N of the decision block 425), meaning that safe interruption of electric motor 205 powering is not possible, emergency procedures, not shown, are invoked (possibly, by displaying an error code and/or emitting a sound alarm signal indicative of the detected error), thereafter the motor deactivation procedure 400 ends (activity block 440). Preferably, the motor deactivation procedure 400 ends by displaying proper error codes and/or emitting alarm signals indicative of detected or inferred errors. Similarly to the above, among the inferred errors, a low level S_STATE,L of the state signal S_STATE (instead of the expected high level S_STATE,L) may denote safety relay RL₂ de-energization failure, an intermediate level S_STATE,L of the state signal S_STATE (instead of the expected high level S_STATE,H) may denote undesired de-energized state the bypass relay RL₁, whereas a level different from the high S_STATE,H, intermediate S_STATE,I and low S_STATE,L levels may denote, as before, a generic error of the sensing arrangement 220.

[0074] If instead the state signal S_STATE takes the high level S_STATE,H (exit branch Y of the decision block 425), the motor deactivation procedure 400 goes on by operating the bypass relay RL₁ into the de-energized state (activity block 430), and by disenabling mechanical door locking (activity block 435) -preferably, while switching on the door switch SW_L by means of the control signal S_SWL, so as to cause electrical decoupling between the line terminal T_L and the input terminal T_215,IN2 of the rectifying arrangement 215), thereafter the motor deactivation procedure 400 ends (activity block 440).

[0075] As mentioned above, bypass relay RL₁ de-energization, altough not necessary, is advantageously carried out for consistency with a following motor activation procedure (such as the motor activation procedure 300 discussed in the foregoing) providing the de-energized state of both bypass RL₁ and safety RL₂ relays as default starting configuration for inferring failures - anyway, nothing prevents from carrying out bypass relay RL₁ de-energization at the start of the motor activation procedure 300. For the same reasons, as illustrated, no check of whether bypass relay RL₁ de-energization has taken place correctly is carried out after the activity block 430 (this check being indeed carried out at the start of the motor activation procedure following the motor de-activation procedure 400), although this should not be construed limitatively.

[0076] Turning now to Figure 5, it schematically shows a portion of a circuit system 500 of the appliance 100 according to another embodiment of the present invention. The circuit system 500 is similar to the circuit system 200, reason why, in the following, same or similar elements will not be discussed again for the sake of conciseness.

[0077] Specifically, according to the considered embodiment, the circuit system 500 comprises, as above, the electric motor 205, the motor module 210 (powered between the first V_DC1 and second V_DC2 DC supply voltages), the power conversion arrangement for (selectively) providing said DC supply voltages V_DC1, V_DC2 according to the AC supply voltage selectively received from the line T_L and neutral T_N terminals of the AC power supply, and the sensing arrangement 220.

[0078] The power conversion arrangement comprises, as before, the rectifying arrangement 215, whose input terminals T_215,IN1,T_215,IN2 are selectively coupleable to the line T_L and neutral T_N terminals, respectively, for receiving the AC supply voltage and whose output terminals T_215,OUT1,T_215,OUT2 provide pulsed DC voltages, and a smoothing (or bulk) capacitor C, whose terminals T_C1,T_C2 are electrically coupled to the output terminals T_215,OUT1,T_215,OUT2, respectively, of the rectifying arrangement 215 for smoothing the pulsed DC voltages into said DC supply voltages V_DC1,V_DC2.

[0079] Selective reception of the AC supply voltage from line T_L and neutral T_N terminals is achieved by means of a number of electrically-operated switching devices, comprising, as above, a door switch SW_L provided between the line terminal T_L and the input terminal T_215,IN1 of the rectifying arrangement 215, and a switching arrangement provided between the neutral terminal T_N and the input terminal T_215,IN2 of the rectifying arrangement 215. Differently from the above, the switching arrangement comprises a single (e.g., electromagnetic) relay RL having both bypass and safety functions (thus, referred to as bypass/safety relay hereinafter), and electrically coupled between the neutral terminal T_N and the input terminal T_215,IN2 of the rectifying arrangement 215. The use of a single relay RL makes the circuit system 500 more simple and cheap than the circuit system 200.

[0080] The bypass/safety relay RL, e.g. structurally similar to the bypass RL₁ and safety RL₂ relays, comprises side (fixed) contacts C_A,RLC_C,RL electrically coupled to a sensing arrangement 520 and to the input terminal T_215,IN2 of the rectifying arrangement 215, respectively, and a central contact C_B,RL, movable with respect to the side contacts C_A,RLC_C,RL, electrically coupled to the neutral terminal T_N. In the considered example, the bypass/safety relay RL is herein assumed, in the de-energized state (i.e., in absence of current across the coil), with the central contact C_B,RL electrically coupled to a respective side contact (e.g. the side contact C_A,RL), and, in the energized state (i.e., in presence of an electric current across the coil)with the central contact C_B,RL electrically coupled to the other side contact (i.e., the side contact C_C,RL).

[0081] In order avoid (in the off condition of the door switch SW₁) large peak surge currents, or inrush currents, flowing through (thus electrically stressing) the door switch SW_L, the rectifying arrangement 215 and the bulk capacitor C (especially when the bulk capacitor C is initially discharged), the circuit system 500 also comprises an inrush current limiting device, for example a NTC thermistor (as before) or, as in the exemplary considered embodiment, a fusible resistor R_FUSE electrically coupled in parallel with the bypass/safety relay RL for mitigating the inrush current experienced during startup. According to the exemplary illustrated embodiment, the fusible resistor R_FUSE is electrically coupled between the central C_B,RL and side C_C,RL contacts of the bypass/safety relay RL (and, hence, between the neutral terminal T_N and the input terminal T_215,IN2 of the rectifying arrangement 215).

[0082] Basically, a fusible resistor is a standard resistor by the electrical viewpoint, and if further designed to open without flames when overloaded (thus, sometimes also referred to as flameproof resistor). The use of the fusible resistor R_FUSE instead of the NTC thermistor R_NTC makes the circuit system 500 cheaper than the circuit system 200, and ensures a constant starting current to be fed to the rectifying arrangement during startup.

[0083] Thus, by proper sizing of the fusible resistor R_FUSE, during startup (door switch SW_L in the on condition and bypass/safety relay RL in the de-energized state) the neutral terminal T_N is electrically coupled to the input terminal T_215,IN2 of the rectifying arrangement 215 through the fusible resistor R_FUSE, and a fixed starting current (depending on fusible resistor R_FUSE resistance) is allowed to flow therethrough. After startup completing or preset time elapsing, the bypass/safety relay RL is operated into the energized state (i.e., central contact C_B,RL thereof moved to the side contact C_C,RL), thus bypassing (i.e., substantially short-circuiting) the fusible resistor R_FUSE and allowing a working current (substantially depending on the AC supply voltage and on the experienced impedance) to be fed to the rectifying arrangement 215 (through the bypass/safety relay RL, i.e. the central C_B,RL and side C_C,RL contacts thereof).

[0084] The sensing arrangement 520 comprises, similarly to the sensing arrangement 220, the pull-down resistor R_PD, whose first terminal T_RPD,1 is adapted to be electrically coupled to the side terminal C_A,RL of the bypass/safety relay RL (e.g., as above, by means of the MOS transistor 225, or other electrically-operated switching device) and whose second terminal T_RPD,2 is configured to receive the lower reference voltage GND, and, preferably, the filtering arrangement F_LP.

[0085] The sensing arrangement 520, when coupled to the side contact C_A,RL of the bypass/safety relay RL (MOS transistor 225 in the on condition), is intended to sense the (energized or de-energized) state of the bypass/safety relay RL and to provide a corresponding state signal S*_STATE. As better discussed herebelow, by virtue of the considered circuit system 500 implementation, the state signal S*_STATE may take two different levels according to the bypass/safety relay RL state, namely the low S_STATE,L and high S_STATE,H levels.

[0086] During sensing, the following bypass/safety relay RL states may be discriminated (and signaled, through the respective high S_STATE,H or low S_STATE,L levels of the state signal S*_STATE):

Bypass/safety relay RL in the energized state

[0087] In this state, the fusible resistor R_FUSE is short-circuited (bypassed) by the bypass/safety relay RL. The central terminal C_B,RL of the bypass/safety relay RL is electrically coupled to the side terminal C_C,RL, the side terminal coupled to the sensing arrangement 520 (i.e., the side terminal C_A,RL2) being instead floating. As a result of that, by effect of the pull-down resistor R_PD, the first terminal T_RPD,1 of the pull-down resistor R_PD is pulled down to the lower reference voltage GND. Thus, the state signal S*_STATE takes the low level S_STATE,L.

Bypass/safety relay RL in the de-energized state

[0088] In this state, the first terminal T_RPD,1 of the pull-down resistor R_PD and the neutral terminal T_N are both at the upper reference voltage V_CC (as being directly coupled to each other). Thus, the state signal S*_STATE takes the high level S_STATE,H.

[0089] As better discussed in the following procedures, errors to the bypass/safety relay RL or to the fuse resistor R_FUSE may also be inferred when the state signal S*_STATE takes a level different from the expected one.

[0090] The circuit system 500 further comprises a control unit 530, similar to the control unit 230, configured to receive the state signal S*_STATE from the sensing arrangement 520 and the standard error/control messages MSG from the motor module 210, and, accordingly, to control the door switch SW_L, the bypass/safety relay RL and the MOS transistor 225 (e.g., by means of respective control signals S_SWL,S_RL,S₂₂₅) and to command motor module 210 (e.g., by means of the command signals S_COMM). As for the control unit 230, the control unit 530 is herein assumed to be capable of commanding mechanical lock of the door 115 (by means of the door lock command), and determining whether such a mechanical lock has taken place correctly.

[0091] Figures 6 and 7 show simplified flowcharts of respective procedures implemented by the circuit system of Figure 5 according to an embodiment of the present invention.

[0092] With reference first to Figure 6, it shows a motor activation procedure 600 carried out under the control of the control unit 530 in response to a motor activation request, according to an embodiment of the present invention. Broadly speaking, the motor activation procedure 600 is aimed at activating the electric motor 205 if, from a default configuration wherein the bypass/safety RL is in the de-energized state (i.e., the state signal S_STATE takes the high level S_STATE,H), mechanical door locking is enabled, the starting current (i.e., the electric current limited by the fuse resistor R_FUSE) is correctly fed to the driving arrangement 205,210,C, communication between the electric motor 205 and the driving arrangement 205,210,C is active, and the working current is allowed to be fed to the driving arrangement 205,210,C (i.e., bypass/safetyrelay RL in the energized state). In addition, as better discussed herebelow, the motor activation procedure 600 also performs check phases aimed at evaluating bypass/safety relay RL or fuse resistor R_FUSE.

[0093] The motor activation procedure 600 starts by checking (decision block 605) whether S*_STATE=S_STATE,H - it meaning that bypass/safety relay RL is in the de-energized state (as expected from the last motor deactivation procedure), and no malfunction affect the fuse resistor R_FUSE.

[0094] In the negative case (exit branch N of the decision block 605), the motor activation procedure 600 ends without that motor activation takes place (activity block 640), possibly by displaying an error code and/or emitting a sound alarm signal indicative of detected or inferred errors. Among the inferable errors, a low level S_STATE,L of the state signal S*_STATE (instead of the expected high level S_STATE,H) may denote fuse resistor R_FUSE short-circuit or undesired bypass/safety relay RL energized state, whereas a level different from the high S_STATE,H and low S_STATE,L levels may denote a generic error of the sensing arrangement 520.

[0095] Otherwise (exit branch Y of the decision block 605), the motor activation procedure 600 goes on by enabling mechanical door locking (activity block 610), thereafter correct door locking is checked at the decision block 615.

[0096] If mechanical lock of the door has failed, exit branch N of the decision block 615, the motor activation procedure 600 ends (activity block 640), as the possibility of opening the door 115 when the electric motor 205 is activated is not prevented. Otherwise, exit branch Y of the decision block 615, it meaning that the electric motor 205 can be activated without risks for any user accidentally tenting to open the door 115, the motor activation procedure 600 goes on by determining (decision block 620) correct, active and functioning communication between the electric motor 205 and the motor module 210 by means of the standard error/control messages MSG.

[0097] If correct, active and functioning communication between the electric motor 205 and the motor module 210 is determined (exit branch Y of the decision block 620), the bypass/safety relay RL is operated into the energized state (activity block 625) - so that the working current substantially depending on the AC supply voltage and on the experienced impedance is entirely fed to the rectifying arrangement 215). Otherwise, the motor activation procedure 600 ends without that motor activation takes place, possibly by displaying an error code and/or emitting a sound alarm signal indicative of the detected error. Preferably, the error detected in this case may be either fusible resistor R_FUSE opening (so that the motor module 210, being not powered, is not able to provide the standard error/control messages MSG to the control unit 530) or motor module 210 malfunctioning.

[0098] Then, decision block 630, the motor activation procedure 600 checks wether bypass/safety relay RL energization has taken place correctly - i.e., whether S*_STATE=S_STATE,L. In the affirmative case (exit branch Y of the decision block 630), motor module 210 activation (and, hence, electric motor 205 correct and safe activation) is commanded by means of the command signals S_COMM (activity block 635), thereafter the motor activation procedure 600 ends (activity block 640).

[0099] If instead bypass/safety relay RL energization has not taken place correctly (exit branch N of the decision block 630), the motor activation procedure 600 ends (activity block 640) without motor activation, possibly by displaying proper error codes and/or emitting alarm signals indicative of detected or inferred errors. Among the inferable errors, a level different from the high S_STATE,H and low S_STATE,L levels may denote, as before, a generic error of the sensing arrangement 520.

[0100] Turning now to Figure 7, it shows a simplified flowchart of a motor deactivation procedure 700 carried out under the control of the control unit 530 in response to a motor deactivation request, according to an embodiment of the present invention. Broadly speaking, the motor deactivation procedure 700 is aimed at disenabling mechanical door locking if motor deactivation has occurred, and if, after operating the bypass/safety relay RL into the energized state, the state signal S*_STATE takes the high level S_STATE,H and if a predefined time period has passed since motor deactivation request.

[0101] The motor deactivation procedure 700 starts by commanding, by means of the command signals S_COMM, deactivation of the electric motor 205 (activity block 705) in response to the motor deactivation request, and by operating the bypass/safety relay RL into the de-energized state (action block 720) as soon as the electric motor 205 has stopped or, anyway, after a predefined time interval has elapsed from the motor deactivation request (or, alternatively, from transmission of the command signals S_COMM). This is conceptually represented in the figure by loop connection between a decision block 710 (wherein electric motor 205 stopping is checked) and a decision block 715 (wherein predefined time interval elapsing is checked). Briefly, the motor deactivation procedure 700 keeps running the decision blocks 710,715 as long as the electric motor 205 has not stopped (exit branch N of the decision block 710) and the predefined time interval has not elapsed (exit branch N of the decision block 715). Instead, if (i.e., as soon as) the electric motor 205 has stopped (exit branch Y of the decision block 710), or the predefined time interval has elapsed without that the electric motor 205 has stopped (exit branch Y of the decision block 715), the bypass/safety relay RL is operated into the de-energized state (activity block 720). As discussed above, elapsing of the predefined time interval might mean that communication between the electric module 205 and the motor module 210 is temporary or permanently prejudiced (in which case the motor module 210 may not have deactivated the electric motor 205, or may not have received confirmation about electric motor 205 stopping), so that operating the bypass/safety relay RL into the de-energized state allows safely interrupting electric motor 205 powering in any case. Indeed, bypass/safety relay RL de-energization causes intervention of the fusible resistor R_FUSE, and hence unpowering the motor module 210 (in fact, the inrush current through the fusible resistor R_FUSE is not sufficient to keep the electric motor 205 powered).

[0102] The motor deactivation procedure 700 goes on by checking (decision block 725) whether the bypass/safety relay RL de-energization has taken place correctly - i.e., whether S*_STATE=S_STATE,H.

[0103] In the negative case (exit branch N of the decision block 425), the motor deactivation procedure 700 ends (activity block 740) without door unlocking (so as to prevent the user from opening the door 115 in a not safe condition of the appliance 100), preferably by displaying proper error codes and/or emitting alarm signals indicative of detected or inferred errors. Similarly to the above, among the inferred errors, a level different from the high S_STATE,H and low S_STATE,L levels may denote a generic error of the sensing arrangement 520.

[0104] If instead the state signal S*_STATE takes the high level S_STATE,H (exit branch Y of the decision block 725), the motor deactivation procedure 700 goes on by disenabling mechanical door locking (activity block 735) - preferably, while switching off the door switch SW_L by means of the control signal S_SWL, so as to cause electrical decoupling between the line terminal T_L and the input terminal T_215,IN2 of the rectifying arrangement 215) - after a safety time interval (e.g., from bypass/safety relay RL de-energization) has elapsed(decision block 730), thereafter the motor deactivation procedure 700 ends (activity block 740).

[0105] Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the invention described above many logical and/or physical modifications and alterations. More specifically, although the invention has been described with a certain degree of particularity with reference to preferred embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible. In particular, different embodiments of the invention may even be practiced without the specific details (such as the numeric examples) set forth in the preceding description for providing a more thorough understanding thereof; on the contrary, well known features may have been omitted or simplified in order not to obscure the description with unnecessary particulars.

Claims

1. Washing and/or drying appliance (100) comprising:

an electric load (205),

a driving arrangement (210,215,C) for driving the electric load (205), the driving arrangement (210,215,C) having first (T_205,IN1) and second (T_205,IN2) terminals coupleable, respectively, to a line terminal (T_L) and to a neutral terminal (T_N) providing a reference voltage (V_CC),

an inrush current limiting device (R_FUSE;R_NTC) and a switching device (RL;RL₁) between the reference terminal (T_N) and the second terminal (T_205,IN2) of the driving arrangement (210,215,C), the switching device (RL;RL₁) being operable in first or second states preventing or allowing, respectively, an electric current to flow through the inrush current limiting device (R_FUSE,R_NTC), and

a sensing network (R_PD) for sensing the first or second states of the switching device (RL;RL₁) and for providing a corresponding state signal (S_STATE;S*_STATE), the sensing network (R_PD) having a first terminal (T_RPD,1), and a second terminal (T_RPD,2) coupled to a reference terminal providing a further reference voltage (GND) lower than the reference voltage (V_CC), wherein, during sensing:

in the first state of the switching device (RL;RL₁) the reference terminal (T_N) and the first terminal (T_RPD,1) of the sensing network (R_PD) being coupled to each other such that the first terminal (T_RPD,1) of the sensing network (R_PD) receives the reference voltage (V_CC) and the state signal (S_STATE;S*_STATE) takes a first level (S_STATE,H) equal to the reference voltage (V_CC), in the second state the state signal (S_STATE, S*_STATE) taking a second level (S_STATE,I;S_STATE,L) lower than the first level (S_STATE,H).

2. Washing and/or drying appliance (100) according to Claim 1, wherein in the second state of the switching device (RL₁) the reference terminal (T_N) and the first terminal (T_RPD,1) of the sensing network (R_PD) are coupled to each other with interposition of the inrush current limiting device (R_NTC), whereby the second level (S_STATE,I) of the state signal (S_STATE) is between the first the reference voltage (V_CC) and the further reference voltage (GND) according to a partition between the inrush current limiting device (R_NTC) and the sensing network (R_PD).

3. Washing and/or drying appliance (100) according to Claim 1, wherein in the second state of the switching device (RL) the first terminal (T_RPD,1) of the sensing network (R_PD) is electrically floating, whereby the second level (S_STATE,L) of the state signal (S_STATE) is at the further reference voltage (GND) by pull-down action of the sensing network (R_PD).

4. Washing and/or drying appliance (100) according to Claim 3, wherein the switching device (RL) has a first contact (C_A,RL) electrically coupled, during sensing, to the sensing network (R_PD), a second contact (C_C,RL) coupled to the second terminal (T_205,IN2) of the driving arrangement (210,215,C), and a third contact (C_B,RL) electrically coupled to the reference terminal (T_N) and contacting the first (C_A,RL) or second (C_C,RL) contacts in first or second states, respectively, of the switching device (RL).

5. Washing and/or drying appliance (100) according to Claim 1 or 2, wherein the switching device (RL₁) has a first contact (C_A,RL1) electrically floating, a second contact (C_C,RL1), and a third contact (C_B,RL1) electrically coupled to the reference terminal (T_N) and contacting the first (C_A,RL1) or second (C_C,RL1) contacts in first or second states, respectively, of the switching device (RL₁), and wherein
the appliance (100) also comprises a further switching device (RL₂) operable in first or second states electrically coupling the second contact (C_C,RL1) of the switching device (RL₁) to the first terminal (T_RPD,1) of the sensing network (R_PD) or to the second terminal (T_215,IN2) of the driving arrangement (210,215,C), respectively.

6. Washing and/or drying appliance (100) according to Claim 5, wherein the first terminal (T_RPD,1) of the sensing network (R_PD) is coupled, during sensing, to the second contact (C_C,RL1) of the switching device (RL₁), and wherein in the second state of the further switching device (RL₂) the state signal (S_STATE) takes a third level (S_STATE,L) equal to the further reference voltage (GND).

7. Washing and/or drying appliance (100) according to any of the preceding Claims, wherein the sensing network (R_PD) is a resistive network (R_PD).

8. Washing and/or drying appliance (100) according to any of the preceding Claims, further comprising a filtering arrangement (F_LP) for suppressing disturbances from the state signal (S_STATE, S*_STATE).

9. Washing and/or drying appliance (100) according to any of the preceding Claims, wherein the inrush current limiting device (R_FUSE;R_NTC) is a fusible resistor (R_FUSE) or a negative temperature coefficient thermistor (R_NTC).

10. Washing and/or drying appliance (100) according to any of the preceding Claims, wherein the electric load (205) is an electric motor, for example a "Variable-Frequency Drive" motor or a Brushless DC motor

11. Washing and/or drying appliance (100) according to any of the preceding Claims, wherein the appliance is a laundry washing appliance intended to perform only laundry washing operations, or a laundry drying appliance intended to perform only laundry drying operations, or a laundry washing/drying appliance intended to perform both laundry washing and laundry drying operations.

12. Washing and/or drying appliance (100) according to any of the preceding Claims, wherein the appliance (100) further comprises a mechanical door-lock device for mechanically locking an appliance door (120) thereby preventing door opening when the electric load (205) is activated.

13. Method (300,400;600,700) for operating a washing and/or drying appliance (100), the appliance (100) comprising:

an electric motor (205) and a driving arrangement (205,210,C) for driving it, the driving arrangement (210,215,C) being coupleable to a line terminal (T_L) and to a neutral terminal (T_N) providing a reference voltage (V_CC),

between the neutral terminal (T_N) and the driving arrangement (210,215,C), an inrush current limiting device (R_FUSE;R_NTC) and a switching device (RL;RL₁), the switching device (RL;RL₁) being operable between first and second states allowing and preventing, respectively, an electric current to flow through the inrush current limiting device (R_FUSE,R_NTC), and

a sensing arrangement (220) configured for sensing the first or second states of the switching device (RL;RL₁) and for providing a corresponding state signal (S_STATE;S*_STATE), in the first state of the switching device (RL;RL₁) the state signal (S_STATE;S*_STATE) taking a first level (S_STATE,H) equal to the reference voltage (V_CC), and in the second state of the switching device (RL;RL₁) the state signal (S_STATE, S*_STATE) taking a second level (S_STATE,I;S_STATE,L) lower than the first level (S_STATE,H),

the method comprising, under the control of a control unit (230,530) of the appliance (100) and in response to a motor activation request:

if (310;605) the state signal (S_STATE;S*_STATE) takes the second level (S_STATE,I;S_STATE,L), feeding (335,340;615) the driving arrangement (205,210,C) with a first electric current limited by the inrush current limiting device (R_FUSE;R_NTC), and

if (345;620) communication between the electric motor (205) and the driving arrangement (205,210,C) is active, operating (350;625) the switching device (RL,RL₁) into the second state thereby allowing a second electric current not limited by the inrush current limiting device (R_FUSE;R_NTC) to be fed to the driving arrangement (205,210,C), and activating (355;635) the electric motor (205).

14. Method (300,400;600,700) according to Claim 13, wherein the appliance (100) further comprises a mechanical door-lock device for mechanically locking an appliance door (120) thereby preventing door opening when the electric motor (205) is activated, wherein the method (300,400;600,700) further comprises enabling (325;610) mechanical door locking, and wherein said feeding (335,340;615) the driving arrangement (205,210,C) with a first electric current limited by the inrush current limiting device (R_FUSE;R_NTC) is performed if (330;615) mechanical door locking is enabled.

15. Method (300) according to Claim 14, wherein the appliance (100) further comprises a further switching device (RL₂) operable in first or second states electrically coupling the switching device (RL₁) to the sensing arrangement (220) or to the driving arrangement (205,210,C), respectively, in the first state of the further switching device (RL₂) the state signal (S_STATE) taking the first (S_STATE,H) or second (S_STATE,I) levels according to the first or second states, respectively, of the switching device (RL₁), and wherein said enabling (325) mechanical door locking if (310;605) the state signal (S_STATE) takes the second level (S_STATE,I) comprises:

operating (305) the switching device (RL₁) in the first state,

if (310) the state signal (S_STATE) takes the first level (S_STATE,I), operating (315) the switching device (RL₁) in the second state, and

if (320) the state signal (S_STATE) takes the second level (S_STATE,I), performing said enabling (325;610) mechanical door locking.

16. Method (300) according to Claim 15, wherein in the second state of the further switching device (RL₂) the state signal (S_STATE) takes a third level (S_STATE,L) lower than the first (S_STATE,H) and second (S_STATE,I) levels, the method further comprising, after said enabling (325;610) mechanical door locking:

if (330) mechanical door locking is enabled, operating (335) the further switching device (RL₂) in the second state, and

performing said operating (350) the switching device (RL₁) into the second state if (345) communication between the electric motor (205) and the driving arrangement (205,210,C) is active and if (340) the state signal (S_STATE) takes the third level (S_STATE,L).

17. Method (400) according to Claim 14, 15 or 16, further comprising, in response to a motor deactivation request:

if (410,415) motor deactivation has occurred, operating (420) the further switching device (RL₂) into the first state, and

if the state signal (S_STATE) takes the second level (S_STATE,I), operating (430) the switching device (RL₁) into the first state and disenabling (435) mechanical door locking.

18. Method (700) according to Claim 14, further comprising, in response to a motor deactivation request:

if (710,715) motor deactivation has occurred, operating (720) the switching device (RL) into the first state, and

if the state signal (S_STATE) takes the first level (S_STATE,H) and if (730) a predefined time period has passed since motor deactivation request, disenabling (735) mechanical door locking.

Drawing