Driving Circuit of Turnable Motor in Microwave Oven

Abstract

 The present invention relates in general to a driving circuit of a turntable motor in microwave oven, and more particularly to a driving circuit for driving a turntable motor which is operated at a low voltage. Advantageously, a low-voltage turntable motor is smaller and more cost effective than in the prior art. The driving circuit includes: voltage changing means for transforming a commonly used AC power supply into a low level voltage, such as a transformer (143). Optionally, the driving circuit also comprises control means (180) for generating a control signal according to a key signal generated from key input means (170); and switching means (150) for selectively supplying the low level voltage generated from the voltage changing means (143) according to the control signal generated from the control means (180).

Description

[0001] The present invention relates in general to a driving circuit of a turntable motor in microwave oven, and more particularly to a driving circuit for driving a turntable motor which is operated at a low voltage.

[0002] Generally, microwave ovens utilize microwaves when cooking foods. In other words, when the microwaves are applied to food molecules in the food, frictional heat is generated therefrom. As a result, the food is heated by the frictional heat.

[0003] The microwaves are generated by a magnetron which performs an oscillating operation at a fundamental frequency. Figures 7 and 8 show such a microwave oven performing a cooking operation by heating the food with the microwaves generated by the magnetron as shown in this drawings, where the microwave oven includes a magnetron 20, a high voltage transformer 10 (hereinafter referred to as HVT) connected to the magnetron 20 for applying a high voltage to the magnetron 20, a lamp for lighting an inside of a cooking chamber 40, a turntable motor 50 for rotating the food (not shown) so that the food can be evenly cooked during the operation of the magnetron 20, a fan motor 80 for cooling the magnetron 20 and circulating air in the cooking chamber 40 during the operation of the magnetron 20, a relay 120 and a relay 130 being turned on/off to control an alternating current (referred to hereinafter as AC) power supply to a lamp (not shown), a turntable motor 50 and a fan motor 80 and the like. A switch 110 is provided for stopping the operation of the magnetron 20 when a door (not shown) is open.

[0004] However, there is a problem in the conventional microwave oven according to the prior art thus constructed, in that the turntable motor driving circuit is designed only for receiving a commonly used AC power supply, thereby enforcing an unnecessary large size turntable motor, so that production costs are rising and power consumption is increased as well.

[0005] EP-A-0,244,845 (Litton Systems) discloses a microwave oven having a combined transformer and motor which produces a low voltage from a secondary winding. The low voltage is used to power operation elements such as a clock display and user control switches.

[0006] The present invention is provided to address the aforementioned problem, and it is an aim of the present invention to provide a driving circuit for a turntable motor in a microwave oven, wherein the turntable motor is not large and costly as in the prior art.

[0007] According to a first aspect of the present invention there is provided a driving circuit of a turntable motor in a microwave oven, the circuit comprising: voltage changing means for transforming a commonly used AC power supply into a low level voltage.

[0008] In one embodiment, preferably the voltage changing means consists of a tap mounted at a stator coil of a fan motor.

[0009] In another embodiment, preferably the voltage changing means is a low-voltage transformer for generating a low level voltage after receiving a commonly used AC power supply from outside.

[0010] Preferably, the low voltage generated from the voltage changing means is about 21 volts.

[0011] Preferably, the circuit further comprises: control means for generating a control signal according to a key signal generated from a key input means; and switching means for selectively supplying the low level voltage generated from the voltage changing means to the turntable motor, according to the control signal generated from the control means. Suitably, the control means generates a control signal for stopping the turntable motor when the user pushes a cooking end button equipped at the key input means, or when a predetermined cooking time elapses, so that a predetermined low voltage generated from the voltage changing means is not supplied to the turntable motor.

[0012] Also according to this aspect of the present invention there is provided a driving circuit for a turntable motor in a microwave oven for receiving a cooking command to thereby cook the food, the circuit comprising: voltage changing means for transforming a commonly used AC power supply into a low level voltage; control means for generating a control signal to switching means according to a key signal generated from key input means; and switching means for selectively supplying a low level voltage generated from the voltage changing means according to the control signal generated from the control means.

[0013] According to a second aspect of the present invention there is provided a microwave oven, comprising: a driving circuit including voltage changing means for transforming a commonly used AC power supply into a low level voltage; and a turntable motor arranged to be driven by the low level voltage from the driving circuit.

[0014] By way of example, specific embodiments of the present invention will now be described with reference to the accompanying drawings in which:-

Figure 1 is a block diagram for illustrating a driving circuit of a turntable motor in a microwave oven according to the present invention;

Figure 2 is a circuit diagram for illustrating an embodiment of the present invention;

Figure 3 is a circuit diagram between a fan motor and a turntable motor;

Figure 4 is a sectional view for illustrating a partially broken fan motor;

Figure 5 is a sectional view for illustrating a partially broken fan motor and a turntable motor connected at both ends thereof to a fan motor;

Figure 6 is a circuit diagram for illustrating another embodiment of the present invention;

Figure 7 is a sectional view of a microwave oven according to the prior art; and

Figure 8 is a circuit diagram for illustrating a motor driving circuit according to the prior art.

[0015] A driving circuit of a turntable motor in the microwave oven according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0016] Figure 1 is a block diagram for illustrating a driving circuit of a turntable motor in the microwave oven.

[0017] As shown in Figure 1, the block diagram consists of voltage transforming means 140 for transforming a commonly used AC power supply input from outside to a predetermined low level voltage.

[0018] Control means 180 which receives a key signal from key input means 170 and generates a control signal to switching means 150.

[0019] The switching means 150 for selectively supplying a predetermined low level voltage to turntable motor driving means 160 according to a control signal generated from the control means 180.

[0020] Next, operation effect of a driving circuit of a turntable motor in the microwave oven according to the present invention thus constructed will be described.

[0021] When an electric power is applied from an electric power supply (not shown), and a user then pushes a cooking start button equipped at the key input means 170, and a cooking start command is output from the key input means 170 to the control means 180 where the control means serves to generate a control signal to the switching means 150.

[0022] According to the control signal, the switching means 150 serves to execute switching operations so as to supply a predetermined low level voltage generated from the voltage transforming means 140 to the turntable motor driving means 160.

[0023] Therefore, the turntable motor is rotated according to the turntable motor driving means 160 to which a predetermined low voltage is applied from the voltage transforming means 140.

[0024] Next, when the user pushes a cooking end button equipped at the key input means 170 or when a predetermined cooking time elapses, the control means 180 then generates a control signal to the switching means 150 so that a predetermined low level voltage generated from the voltage transforming means 140 may not be supplied to the turntable motor driving means 160.

[0025] Therefore, the predetermined low level voltage is not supplied to the turntable motor driving means 160, and the turntable 60 is not rotated any more.

[0026] Figure 2 through Figure 5 are circuit diagrams for illustrating an embodiment of the present invention.

[0027] The embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] Referring to the Figure 2, the commonly used AC power supply Vin is applied from outside to a fan motor 141 according to the control signal generated from the control means 180.

[0029] Successively, a predetermined low level voltage is supplied to the turntable motor 161 through a low voltage output terminal 144, and thereby the turntable motor 161 is rotated.

[0030] Meanwhile, as is known in Figure 3, as a tap or tapping 146 is connected to a stator coil 145, an output voltage generated from a tap terminal 146 is transformed to a predetermined low level voltage VL, and it is supplied to the turntable motor 161.

[0031] Furthermore, as is known in Figure 5, the commonly used AC power supply (not shown) is applied to the stator coil 145 through an input terminal 142, 143 from outside, and a predetermined low level voltage which is transformed by the low voltage output terminal 144 is applied to the turntable motor through the low voltage output terminal 144.

[0032] Next, operational effect of a driving circuit of turntable motor in a microwave oven according to the present invention thus constructed will now be described in detail. When the user pushes a cooking start button equipped at the key input means 170 and a cooking start command is output from the key input means 170 to the control means 180, the control means generates a control signal to thereby turn on a relay RY.

[0033] Meanwhile, as the tap 146 is connected to the stator coil 145, an output voltage generated from the tap terminal 146, that is a low level voltage VL, is applied to the turntable motor 161, and the turntable motor 161 is driven to rotate.

[0034] Next, when the user pushes a cooking end button equipped at the key input means 170 or when a predetermined cooking time elapses, the control means 180 then generates a control signal to the switching means 150 so that a predetermined low level voltage generated from the voltage transforming means 140 may not be supplied to the turntable motor 161 and the fan motor 141.

[0035] Furthermore, Figure 6 is a circuit diagram for illustrating another embodiment of the present invention.

[0036] Referring to the Figure 6, the commonly used AC power supply is transformed to a predetermined low level voltage by the low-voltage transformer 143.

[0037] Subsequently, a low level voltage VL transformed by the low-voltage transformed 143 is selectively applied to the turntable motor 161 according to a switching operation of the relay RY controlled by a control signal generated from the control means 180.

[0038] Successively, the turntable motor which receives a low level voltage from the low-voltage transformer 143 is driven to rotate.

[0039] Next, when the user pushes a cooking end button or when a predetermined cooking time elapses, the control means 180 then generates a control signal to the switching means such as relay RY so that a predetermined low level voltage generated from the low-voltage transformer 143 may not be supplied to the turntable motor 161, and subsequently the turntable motor 161 is to be stopped.

[0040] As apparent from the above, there is an advantage in a driving circuit of a turntable motor in the microwave oven according to the embodiment of the present invention, in that a turntable motor is driven to be rotated at a low level voltage which is transformed by voltage transforming means, and in that production costs can be cut down, and also in that consumed AC power can be decreased.

[0041] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0042] All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0043] Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0044] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A driving circuit of a turntable motor (161) in a microwave oven, the circuit comprising:

voltage changing means (143) for transforming a commonly used AC power supply into a low level voltage.

2. The circuit as defined in claim 1, wherein the voltage changing means consists of a tap (146) mounted at a stator coil (145) of a fan motor.

3. The circuit as defined in claim 1, wherein the voltage changing means is a low-voltage transformer (143) for generating a low level voltage (V_L) after receiving a commonly used AC power supply (V_in) from outside.

4. The circuit in accordance with claim 1, 2 or 3, wherein the low level voltage generated from the voltage changing means is about 21 volts.

5. The circuit as defined in any preceding claim, wherein the circuit further comprises:

control means (180) for generating a control signal according to a key signal generated from a key input means (170) ; and

switching means (150) for selectively supplying the low level voltage generated from the voltage changing means to the turntable motor (161) according to the control signal generated from the control means.

6. The circuit as defined in claim 5, wherein the control means (180) generates a control signal for stopping the turntable motor (161) when the user pushes a cooking end button equipped at the key input means (170), or when a predetermined cooking time elapses, so that a predetermined low voltage generated from the voltage changing means (143, 145 or 146) is not supplied to the turntable motor.

7. A microwave oven, comprising:

a driving circuit including voltage changing means (143 or 145, 146) for transforming a commonly used AC power supply into a low level voltage; and

a turntable motor (161) arranged to be driven by the low level voltage from the driving circuit.

Drawing