(19)
(11)EP 2 546 665 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
21.02.2018 Bulletin 2018/08

(21)Application number: 11007589.2

(22)Date of filing:  16.09.2011
(51)Int. Cl.: 
G01R 31/02  (2006.01)
G01R 31/04  (2006.01)

(54)

Electronic device, and open circuit detecting system, detecting method thereof

Elektronisches Gerät und Leitungsbrucherkennungssystem, zugehöriges Erkennungsverfahren

Dispositif électronique et système de détection de circuit ouvert et son procédé de détection


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 24.05.2011 CN 201110136822

(43)Date of publication of application:
16.01.2013 Bulletin 2013/03

(73)Proprietor: TPK Touch Solutions Inc.
Taipei City 114 Taiwan (TW)

(72)Inventors:
  • Chiu, Jui-Jung
    Zhudong Township Hsinchu County 310 (TW)
  • Li, Yi-Kun
    Hsinchu City 300 (TW)

(74)Representative: 2K Patentanwälte Blasberg Kewitz & Reichel 
Partnerschaft mbB Schumannstrasse 27
60325 Frankfurt am Main
60325 Frankfurt am Main (DE)


(56)References cited: : 
WO-A1-2012/110152
US-A- 6 130 530
US-A- 6 098 027
US-A1- 2008 157 782
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The present disclosure relates generally to circuit detection technology, and more particularly, to an electronic device, a system and a method for determining an open circuit status of an object circuit.

    DESCRIPTION OF THE RELATED ART



    [0002] There exist two systems to detect an open circuit status of an object circuit, namely an alternating current ("AC") detecting system and a direct current ("DC") detecting system.

    [0003] An alternating current detecting system for detecting an open circuit is illustrated in FIG. 1. An object circuit under test is equivalent to an equivalent resistor and an equivalent capacitor connected to the resistor in series. In order to determine if the object circuit is electrically open or not, an AC source is connected between one end of the object circuit and the ground. The other end of the object circuit is connected to one end of a detecting module. This detection system has a physical ground loop. An AC signal generated by the AC source is transmitted to the detecting module through the object circuit. Thus, the detecting module can determine the status of the object circuit based on the AC signal's frequency or magnitude.

    [0004] A direct current detecting system for detecting an open circuit is illustrated in FIG. 2. An object circuit under test can be represented as an equivalent resistor. To determine the status of the object circuit, a DC signal generated by a DC source is applied to one end of the object circuit. The other end of the object circuit is connected to one end of a detecting module. The other end of the DC source and the other end of the detecting module are also connected to the ground. This detection system has a physical ground loop. The detecting module can determine whether the object circuit is open through acquiring the current of the DC signal or the voltage of the DC signal.

    [0005] A typical detecting system has a physical ground loop. Various wires within the system may affect the detecting system. As a result, a detection system may not always determine the true status of the object circuit. The equivalent resistance generated by wires in an alternating current detecting system may be large. According to the formula V(noise) = I(noise)*Z(line), a weak noise (I(noise)) will become a large interfering signal (V(noise)) while it flows through the resistor (Z(line)). One solution to this problem is adding a filter module. However, only specific frequencies can be filtered by the filter module. While filters are useful for eliminating unwanted frequencies from a given signal, some desired frequencies in the signal may also be removed from the signal thus causing a loss of desired features. Furthermore, if the capacitance in the object circuit is low, the frequency of the AC signal must be increased. This increase in frequency will result in a potential degradation of an AC signal due to the parasitic capacitance and loop impedance. An extra compensating circuit may be needed to eliminate these undesired effects.

    [0006] On the other hand, the long thin grounding wires in a DC system reduce the voltage as well as increase the system noise. In order to ensure a high degree of accuracy, the voltage amplitude and the level of sampling resolution must be increased in these systems.

    [0007] Patent documents US 6130530 A, US 6098027 A and US 2008157782 A1 disclose open circuit detection systems. Here, the open circuit detection systems are connected to two ends of a circuit. However, these systems are not suitable for testing circuits that do not have two openings.

    SUMMARY OF THE INVENTION



    [0008] It is an object of the present invention to provide an enhanced open circuit detecting system for determining an open circuit status of an object circuit by using certain features of the object circuit and performing this determination in spite of the noise generated by various circuit elements and their interactions with each other. It is a further object of the present invention to provide a corresponding method for detecting an open circuit status of an object circuit and to provide an electronic device comprising such an open circuit detecting system.

    [0009] These problems are solved by an open circuit detecting system as claimed by claim 1, by a method for detecting an open circuit status of an object circuit as claimed by claim 5 and by an electronic device as claimed by claim 9. Further advantageous embodiments are the subject-matter of the dependent claims.

    [0010] An open circuit detecting system according to the present invention is configured to connect to an object circuit for obtaining an electrical signal through a virtual ground induced by characteristic impedance of a parasitic capacitor and for determining whether the object circuit is in an open circuit state according to the electrical signal. The electrical signal obtained by the open circuit detecting system indicates that the capacitance of the parasitic capacitor in normal circuit is greater than the capacitance of the parasitic capacitor in an open circuit status. The open circuit detecting system according to the present invention thus includes a test unit, a stray-capacitance boosting unit, a sampling unit, and a signal processing unit; wherein the sampling unit is a sampling resistor, the signal processing unit comprises an inverter, a comparator connected to the inverter, and an "AND" gate connected to the comparator, one end of the test unit is connected to a power supply, and the other end of the test unit is connected to a first input of the stray-capacitance boosting unit, a second input of the stray-capacitance boosting unit is connected to the object circuit, an output of the stray-capacitance boosting unit is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the ground, an input of the inverter is connected to the common point of the stray-capacitance boosting unit and the sampling resistor, an output of the inverter is connected to a negative terminal of the comparator, a positive terminal of the comparator is configured to receive a reference voltage, an output of the comparator is connected to a first input of the "AND" gate, a second input of the "AND" gate is configured to receive a gate pulse, an output of the "AND" gate is used to output several number of pulses corresponding to the capacitance of the parasitic capacitor, wherein the open circuit detecting system acquires an electrical signal from the object circuit and based on said electrical signal it is determined whether the object circuit is in a normal circuit status or in an open circuit status by determining the capacitance of the parasitic capacitor, wherein the capacitance of the parasitic capacitor in a normal circuit status is greater than the capacitance of the parasitic capacitor in an open circuit status.

    [0011] In a preferred embodiment, the test unit is configured to generate a burst pulse for charging the parasitic capacitor, and the sampling unit is configured to discharge the charged parasitic capacitor.

    [0012] In a preferred embodiment, the rising edge of the burst pulse is before the falling edge of the burst pulse.

    [0013] In a preferred embodiment, the stray-capacitance boosting unit is an Insulated Gate Bipolar Transistor, a triode, or a Darlington Transistor.

    [0014] In a preferred embodiment, the signal processing unit is configured to convert the electrical signal into several numbers of pulses corresponding to the capacitance of the parasitic capacitor.

    [0015] A method for detecting open circuit includes the steps of: acquiring an electrical signal through a virtual ground induced by characteristic impedance of a parasitic capacitor; and determining whether the object circuit is open according to the electrical signal.

    [0016] In a preferred embodiment, the electrical signal indicates the capacitance of the parasitic capacitor in normal circuit is greater than the capacitance of the parasitic capacitor in open circuit.

    [0017] A method for detecting open circuit according to the present invention using the open circuit detecting system as outlined above, wherein a parasitic capacitor exists between the object circuit and ground, said parasitic capacitor having a characteristic impedance, which represents all the parasitic capacitance that exists between conductors, conductors or components and ground, or the capacitance that exists between components, comprises the steps of: acquiring an electrical signal corresponding to the parasitic capacitor that exists between the object circuit and ground, said parasitic capacitor having a characteristic impedance, which represents all the parasitic capacitance that exists between conductors, conductors or components and ground, or the capacitance that exists between components; and determining whether the object circuit is in an open circuit status or in a normal circuit status according to the electrical signal by determining the capacitance of the parasitic capacitor; wherein the capacitance of the parasitic capacitor in a normal circuit status is greater than the capacitance of the parasitic capacitor in an open circuit status.

    [0018] In a preferred embodiment, the step of testing includes: generating a burst pulse for charging the parasitic capacitor, and discharging the parasitic capacitor though a sampling unit to generate the electrical signal.

    [0019] In a preferred embodiment, the method further includes the steps of: converting the electrical signal into an identification signal; and determining whether the object circuit is open according to the identification signal.

    [0020] An electronic device according to the present invention includes an object circuit and an open circuit detecting system as outlined above.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0021] The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. In the drawings:
    FIG. 1
    is a functional block diagram of a an alternating current detecting system according to the prior art for detecting an open circuit status of an object circuit;
    FIG. 2
    is a functional block diagram of a direct current detecting system according to the prior art for detecting an open circuit status of an object circuit;
    FIG. 3
    is a functional block diagram of a first embodiment of an open circuit detecting system serving for a better understanding of the present invention;
    FIG. 4
    is a functional block diagram of a second embodiment of an open circuit detecting system serving for a better understanding of the present invention;
    FIG. 5
    is a functional block diagram of a third embodiment of an open circuit detecting system according to the present invention;
    FIG. 6
    is a circuit diagram of the third embodiment of an open circuit detecting system according to the present invention;
    FIG. 7
    is a sequence diagram of an open circuit detecting system according to the present invention;
    FIG. 8
    is a flowchart of the first embodiment of an open circuit detecting method according to the present invention; and
    FIG. 9
    is a flowchart of a second embodiment of an open circuit detecting method according to the present invention.

    DETAILED DESCRIPTION



    [0022] The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to "an" or "one" embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

    [0023] Referring to FIG. 3, a first embodiment of an open circuit detecting system 110 is illustrated serving for a better understanding of the present invention.

    [0024] One end of the open circuit detecting system 110 is connected to the ground, and the other end of the open circuit detecting system 110 is connected to an object circuit 120. The open circuit detecting system 110 is a circuit or device with the function of detecting an open circuit status of the object circuit 120.

    [0025] The object circuit 120 is a circuit or device under test in which an open circuit may exist. In a normal circuit status, one end of the object circuit 120 is connected to the open circuit detecting system 110. A parasitic capacitor 130 having a characteristic impedance exists between the object circuit 120 and ground. The parasitic capacitor 130 is the capacitance that exists between conductors of the circuit, conductors or components and ground, or the capacitance that exists between components. For the convenience of description, the parasitic capacitor 130 is intended to represent all the parasitic capacitance of the object circuit 120.

    [0026] According to the laws of physics, the capacitance is proportional to the length of conductors in a circuit. The parasitic capacitor 130 in a normal circuit is greater than the parasitic capacitor 130 in open circuit, since the conductor in a normal circuit is longer than the conductor in an open circuit. When the capacitance is determined, the status of the circuit could be determined by an experienced person or a machine. Therefore, the open circuit detecting system 110 is arranged for inducing an electrical signal and the electrical signal is used for determining whether the capacitance of the parasitic capacitor 130 is in a normal circuit status, i.e. is greater than the capacitance of the parasitic capacitor 130 in open circuit.

    [0027] Working on a specific frequency, the parasitic capacitor 130 is connected to a virtual ground by a characteristic impedance. In other words, the parasitic capacitor 130 is not connected to ground in reality, but the potential difference between the parasitic capacitor 130 and ground is zero. The open circuit detecting system 110 begins to work under the reference potential and provides the electrical signal which indicates that the circuit status of the object circuit 120 is an open circuit status.

    [0028] Referring to FIG. 4, a second embodiment of an open circuit detecting system 210 is illustrated serving for a better understanding of the present invention. A parasitic capacitor 230 exists, which is the capacitance that exists between conductors of the circuit, between conductors and ground, between components and ground, or between components. For the convenience of description, the parasitic capacitor 230 is intended to represent all the parasitic capacitor of an object circuit 220.

    [0029] According to the laws of physics, the capacitance is proportional to the length of conductors in a circuit. The parasitic capacitor 230 in a normal circuit status is greater than the parasitic capacitor 230 in an open circuit, since the conductor in a normal circuit is longer than the conductor in open circuit. When the capacitance is determined, the status of the circuit could be determined out by an experienced person or a machine. Therefore, the open circuit detecting system 210 is arranged for inducing an electrical signal and the electrical signal is used for determining whether the capacitance of the parasitic capacitor 230 in a normal circuit status, i.e. is greater than the capacitance of the parasitic capacitor 230 in open circuit. In a normal circuit status, one end of the open circuit detecting system 210 is connected to the ground, and the other end of the open circuit detecting system 210 is connected to the object circuit 220.

    [0030] The open circuit detecting system 210 is a circuit or device with the function of detecting an open circuit status. The open circuit detecting system 210 includes a test unit 212 connected to the object circuit 220, a sampling unit 214 connected to the test unit 212, and a signal processing unit 216 connected to the sampling unit 214.

    [0031] The test unit 212 is used for testing the capacitance of the parasitic capacitor 230. The test unit 212 tests the capacitance of the parasitic capacitor 230 by charging the parasitic capacitor 230 or a resonance circuit including the parasitic capacitor 230. If the test unit 212 provides the same testing signals, charging time constants or discharging time constants in an open circuit status and a normal circuit status are different because of different magnitude of the parasitic capacitor.

    [0032] The sampling unit 214 reflects the state of the parasitic capacitor 230. The sampling unit 214 may be a sampling resistor or another circuit with sampling function. The electrical signal which can be easily observed is sampled by the sampling unit 214. As to the object circuit 220, the charging time constant in an open circuit status is smaller than the charging time constant in a normal circuit status. When the capacitance is determined, the status of the circuit could be determined by an experienced person or a machine. Likewise, the parasitic capacitor 230 discharges though the sampling unit 214 after being charged by the test unit 212. The electrical signal which can be easily observed is sampled by the sampling unit 214. As to the object circuit 220, the parasitic capacitor 230 in a normal circuit status is greater than the parasitic capacitor 230 in an open circuit status. When the capacitance is determined, the status of the circuit can be determined by an experienced person or a machine. Similarly, resonance frequencies vary in different resonance circuits including different parasitic capacitors, identical resistors and identical inductors. The sampling unit 214 obtains a resonance signal from the resonance circuit including the test unit 212 and the parasitic capacitor 230. When the capacitance is determined, the status of the circuit can be determined by an experienced person or a machine.

    [0033] To implement an automation, the signal processing unit 216 is added to convert the electrical signal into an identification signal which can be easily recognized by machines. "AND", "OR", "NOT" and comparison operations or combinations with other signals are performed by the signal processing unit 216 to convert the electrical signal obtained from the sampling unit 214 into the identification signal which can be easily recognized by machines. The identification signal is sent to a computer, a digital signal processor (DSP), an advanced RISC machine and so on for computing or displaying a result based on the identification signal obtained.

    [0034] Working on a specific frequency, the parasitic capacitor 230 is connected to a virtual ground by a characteristic impedance. In other words, the parasitic capacitor 230 is not connected to ground in reality, but a potential difference between the parasitic capacitor 230 and ground is zero. The open circuit detecting system 210 begins to work after receiving a reference potential. The open circuit detecting system 210 checks the object circuit 220 to find out whether the status of the object circuit 220 is an open circuit status. The test unit 212 begins to test the capacitance of the parasitic capacitor 230 by charging the parasitic capacitor 230 or the resonant circuit including the parasitic capacitor 230. As to the object circuit 220, the parasitic capacitor 230 in a normal circuit status is greater than the parasitic capacitor 230 in an open circuit status. The sampling unit 214 provides the electrical signal when the parasitic capacitor 230 discharges through the sampling unit 214. Preferably, the electrical signal can be easily observed or processed by a machine. To implement automation, the signal processing unit 216 converts the electrical signal into the identification signal which can be easily recognized by machines. "AND", "OR", "NOT" functions, comparison operations or combinations with other signals are performed by the signal processing unit 216 to convert the electrical signal obtained from the sampling unit 214 into the identification signal which can be easily recognized by machines. The identification signal may be sent to a computer for computing or displaying, thus the status of the object circuit 220 can be provided by a computer.

    [0035] Referring to FIG. 5 and FIG 6, a third embodiment of an open circuit detecting system 310 according to the present invention is illustrated. One end of the open circuit detecting system 310 is connected to ground. A parasitic capacitor 330 exists between the object circuit 320 and ground. The parasitic capacitor 330 is the capacitance that exists between conductors of the circuit, between conductors and ground, between components and ground, or between components and has no physical reality. For the convenience of description, the parasitic capacitor 330 is intended to represent all the parasitic capacitance in the object circuit 320. The detecting relates only to the parasitic capacitor 330, for the convenience of description, the object circuit 320 is omitted in FIG. 6. Furthermore, the parasitic capacitor 330 has its own resistance, and therefore, an equivalent capacitor and an equivalent resistor are connected in series in FIG. 6 for representing the parasitic capacitor 330.

    [0036] The open circuit detecting system 310 is a circuit or device with the function of detecting an open circuit status. The open circuit detecting system 310 includes a test unit 312, a stray-cap booster unit 313 connected to the test unit 312 and the parasitic capacitor 330, a sampling unit 314 connected to the stray-cap booster unit 313, and a signal processing unit 316 connected to the sampling unit 314.

    [0037] The test unit 312 serves for generating a burst pulse. One end of the test unit 312 is connected to a power supply, and the other end of the test unit 312 is connected to a first input of the stray-capacitance boosting unit 313. The test unit 312 is electrically connected to the parasitic capacitor 330 though the stray-capacitance boosting unit 313. Therefore, the test unit 312 charges the parasitic capacitor 330 though the stray-capacitance boosting unit 313.

    [0038] The stray-capacitance boosting unit 313 is configured for amplifying charging and discharging effects. It may be an Insulated Gate Bipolar Transistor, a transistor, a Darlington Transistor or other circuit with an amplifying function. The first input of the stray-capacitance boosting unit 313 is connected to the test unit 312, a second input of the stray-capacitance boosting unit 313 is connected to the parasitic capacitor 330, and an output of the stray-capacitance boosting unit 313 is connected to the common point of the sampling unit 314 and the signal processing unit 316. In an exemplary embodiment, the stray-capacitance boosting unit 313 is a transistor, the first input of the stray-capacitance boosting unit 313 is an emitter of the transistor, the second input of the stray-capacitance boosting unit 313 is a base of the transistor, and the output of the stray-capacitance boosting unit 313 is a collector of the transistor. A burst pulse generated by the test unit 312 charges the parasitic capacitor 330 via the emitter of the transistor and the base of the transistor. The emitter-base junction is forward biased until the voltage of the parasitic capacitor 330 rises up to a preset voltage. Working in the linear region of the transistor, the transistor is in active mode, thus charging and discharging effects are amplified. A discharge current flows through the sampling unit 314 and then forms a voltage signal.

    [0039] The sampling unit 314 reflects the state of the parasitic capacitor 330. The sampling unit 314 can be a sampling resistor or other circuits with sampling function. One end of the sampling unit 314 is connected to the common point of the stray-capacitance boosting unit 313 and the signal processing unit 316, and the other end of the sampling unit 314 is connected to ground. The discharge current of the parasitic capacitor 330 flows from the stray-capacitance boosting unit 313 to ground via the sampling unit 314, and the voltage signal is sampled from the common point of the stray-capacitance boosting unit 313 and the sampling unit 314. At last, the voltage signal is sent to the signal processing unit 316.

    [0040] The signal processing unit 316 includes an inverter 3162, a comparator 3164 connected to the inverter 3162 and an "AND" gate 3166 connected to the comparator 3164.

    [0041] An input of the inverter 3162 is connected to the common point of the stray-capacitance boosting unit 313 and the sampling unit 314, and an output of the inverter 3162 is connected to a negative terminal of the comparator 3164. The inverter 3162 inverts the voltage signal provided by the sampling unit 314. The inverter 3162 has a relatively high input impedance so that it has an insignificant effect on the voltage signal.

    [0042] A reference voltage is applied to a positive terminal of the comparator 3164, the negative terminal of the comparator 3164 is connected to the output of the inverter 3162. When the voltage at the positive terminal is higher than the voltage at the negative terminal, that is, the reference voltage is higher than the output voltage of the inverter 3162, the output voltage of the comparator 3164 is high-level. Otherwise, the output voltage of the comparator 3164 is low-level.

    [0043] A first input of the "AND" gate 3166 is connected to the comparator 3164, a second input of the "AND" gate 3166 is used to receive gate pulses. Only the first input of the "AND" gate 3166 and the second input of the "AND" gate 3166 are both high-level, an output of the "AND" gate 3166 is high-level. That is, when the first input of the "AND" gate 3166 is high-level, the output of the "AND" gate 3166 outputs gate pulses. Otherwise, when the first input of the "AND" gate 3166 is low-level, the "AND" gate 3166 will not output any signal.

    [0044] A sequence diagram is combined below to describe the function of this embodiment of the open circuit detecting system 310 according to the present invention.

    [0045] Referring to FIG. 7, working on the specific frequency, the parasitic capacitor 330 is connected to a virtual ground by a characteristic impedance. In other words, the parasitic capacitor 330 is not connected to ground in reality, but the potential difference between the parasitic capacitor 130 and the ground is zero. The open circuit detecting system 310 begins to work under the reference potential. The open circuit detecting system 310 begins to determine whether the circuit status is an open circuit status.

    [0046] The test unit 312 generates a burst pulse 4 10. The burst pulse 410 is a square wave signal having a rising edge before the failing edge. When the burst pulse 410 is high-level, the inverter 3162, the comparator 3164 and the "AND" gate are enabled. The burst pulse 410 charges the parasitic capacitor 330. Because the equivalent resistor is low, the charging process is finished in a short time. The discharge current is amplified by the stray-capacitance boosting unit 313 and flows to the sampling unit 314. Then, the discharge current forms the voltage signal at the sampling unit 314. The voltage signal is changed into an inverter output signal 420 by the inverter 3162. The inverter output signal 420 is sent to the negative terminal of the comparator 3164 and compared with a reference voltage 402 sent to the positive terminal of the comparator 3164. When the reference voltage 402 at the positive terminal of the comparator 3164 is higher than the voltage of the inverter output signal 420 at the negative terminal of the comparator 3164, the output voltage of the comparator 3164 is high-level, otherwise, the output voltage of the comparator 3164 is low-level.

    [0047] An "AND" operation between the output signal of the comparator 3164 and the gate pulses is performed. When the output of the comparator 3164 is high-level, the output of the "AND" gate 3166 outputs gate pulses. Otherwise, when the output of the comparator 3164 is low-level, the "AND" gate 3166 will not output any signal. As mentioned above, the parasitic capacitor 330 in a normal circuit status is greater than the parasitic capacitor 330 in an open circuit status; for the convenience of description, the parasitic capacitor 330 in a normal circuit status is called a "big capacitor". On the contrary, the parasitic capacitor 330 in an open circuit status is called a "small capacitor". Because of the discharging characteristics of the capacitor, the inverter output signal 420 rises up slowly. A signal line 422 of the big capacitor in the inverter output signal 420 rises up more slowly than a signal line 424 of the small capacitor in the inverter output signal 420. Thus, the duty ratio of a big capacitor comparator output signal 430 is greater than a small capacitor comparator output signal 440. An "AND" operation between the output signal of the comparator 3164, which is sent to the first input of the "AND" gate 3166, and gate pulses 450, which are sent to the second input of the "AND" gate 3166, is performed. Because the duty ratio of the big capacitor comparator output signal 430 is greater than the duty radio of the small capacitor comparator output signal 440, the number of pulses of a big capacitor "AND" gate output signal 460 is larger than that of a small capacitor "AND" gate output signal 470. The number of pulses is sent to the processor, such as a computer, digital signal processor (DSP), a advanced RISC machines or the like, for computing or displaying.

    [0048] Referring to FIG. 8, a first embodiment of a method for detecting an open circuit status according to the present invention is illustrated.

    [0049] Step S810 represents acquiring an electrical signal corresponding to a characteristic impedance of the parasitic capacitor. In other words, the parasitic capacitor is not connected to the ground in reality, but the potential difference between the parasitic capacitor and ground is zero. The open circuit detecting system begins to work under the reference potential and provides the electrical signal which indicates that the circuit status of the object circuit is an open status. Because the parasitic capacitor cannot be directly observed, the parasitic capacitor is charged for generating the electrical signal which can be easily observed.

    [0050] Step S820 represents determining whether the object circuit is an open circuit status, according to the electrical signal. When the electrical signal is determined, the status of the circuit could be determined by an experienced person or a machine. More specifically, the electrical signal indicates the capacitance of the parasitic capacitor in a normal circuit status is greater than the capacitance of the parasitic capacitor in an open circuit status.

    [0051] Referring to FIG.9, a third embodiment of a method for detecting an open circuit status according to the present invention is illustrated.

    [0052] Step S910 represents connecting a parasitic capacitor to a virtual ground, in correspondence to the characteristic impedance of the parasitic capacitor. Working on a specific frequency, the parasitic capacitor is connected to a virtual ground by characteristic impedance. In other words, the parasitic capacitor is not connected to ground in reality, but the potential difference between the parasitic capacitor and ground is zero.

    [0053] Step S920 represents testing the capacitance of the parasitic capacitor and generating an electrical signal representing the capacitance of the parasitic capacitor. Because the parasitic capacitor cannot be directly observed, the parasitic capacitor is charged for generating the electrical signal which can be easily observed.

    [0054] Step S930 represents converting the electrical signal into an identification signal. To implement automation, a signal processing unit is added to convert the electrical signal into an identification signal. "AND", "OR", "NOT" functions and comparison operations or combinations with other signals can be used in the converting process.

    [0055] In step S940, it is determined whether the status of the object circuit is an open circuit status, according to the identification signal. Preferably, the identification signal is sent to the computer for computing or displaying after the identification signal was obtained. At last, the status of the object circuit is determined. As described above, the capacitance of the parasitic capacitor in a normal circuit status is greater than the capacitance of the parasitic capacitor in an open circuit status.

    [0056] The open circuit detecting system and method as set forth above can be used in electronic devices, such as mobile phones, laptop computers, personal digital assistants, etc. If the open circuit detecting system is incorporated in an electronic device, the object circuit can be any other part of the electronic device. The open circuit detecting system is connected to the object circuit for acquiring an electrical signal through a virtual ground induced by a characteristic impedance of a parasitic capacitor and determining whether the object circuit is in an open circuit status or not electrically connected to the open circuit detecting system according to the electrical signal. The electrical signal obtained by the open circuit detecting system indicates that the capacitance of the parasitic capacitor in a normal circuit status is greater than that if the object circuit is in an open status internally or not electrically connected to the open circuit detecting system. Taking a mobile phone with a touch panel as an example, the open circuit detecting system may be integrated in a chip and the object circuit may be a flex-cable or conductive trace on glass. If the flex-cable or conductive trace on glass is open internally or not electrically connected to the chip, the parasitic capacitor will be smaller than that in a normal state.

    [0057] Step S920 represents testing the capacitance of the parasitic capacitor and generating an electrical signal representing the capacitance of the parasitic capacitor. For the parasitic capacitor cannot be directly observed, the parasitic capacitor is charged for generating the electrical signal which is easy to be observed.

    [0058] Step S930 represents converting the electrical signal into an identification signal. To realize automation, a signal processing unit is added to convert the electrical signal into the identification signal. "AND", "OR", "NOT" and comparison operations or combining with the other signal can be used in the converting process.

    [0059] In step S940, it is determined that whether the object circuit is open according to the identification signal. Preferably, the identification signal is sent to the computer for computing or displaying after the identification signal was obtained. At last, the state of the object circuit is found out. As described above, the capacitance of the parasitic capacitor in normal circuit is greater than the capacitance of the parasitic capacitor in open circuit.

    [0060] The open circuit detecting system and method can be used in electronic devices, such as mobile phones, laptop computers, personal digital assistants, etc. If the open circuit detecting system is incorporated in an electronic device, the object circuit can be any other parts of the electronic device. The open circuit detecting system is connected to the object circuit for getting an electrical signal through a virtual ground induced by characteristic impedance of a parasitic capacitor and determining whether the object circuit is open or not electrically connected to the open circuit detecting system according to the electrical signal. The electrical signal obtained by the open circuit detecting system indicates that the capacitance of the parasitic capacitor in normal circuit is greater than that if the object circuit is open internally or not electrically connected to the open circuit detecting system. Taking a mobile phone with a touch panel as an example, the open circuit detecting system may be integrated in a chip and the object circuit may be a flex-cable or conductive trace on glass. If the flex-cable or conductive trace on glass is open internally or not electrically connected to the chip, the parasitic capacitor will be smaller than that in normal state.

    [0061] Although the invention has been described in language specific to structural features and/or methodological acts, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as sample forms of implementing the claimed invention.


    Claims

    1. An open circuit detecting system (310) for determining an open circuit status of an object circuit (320), wherein during the determination of the open circuit status of the object circuit (320) one end of the open circuit detection system (310) is connected to a ground and a parasitic capacitor (330) exists between the object circuit (320) and ground, said parasitic capacitor (330) having a characteristic impedance, which represents all the parasitic capacitance that exists between conductors, conductors or components and ground, or the capacitance that exists between components, characterized by comprising:

    a test unit (312), a stray-capacitance boosting unit (313), a sampling unit (314), and a signal processing unit (316); wherein

    the sampling unit (314) is a sampling resistor,

    the signal processing unit (316) comprises an inverter (3162), a comparator (3164) connected to the inverter (3162), and an "AND" gate (3166) connected to the comparator (3164),

    one end of the test unit (312) is connected to a power supply,

    the other end of the test unit (312) is connected to a first input of the stray-capacitance boosting unit (313), a second input of the stray-capacitance boosting unit (313) is connected to the object circuit (320),

    an output of the stray-capacitance boosting unit (313) is connected to one end of the sampling resistor,

    the other end of the sampling resistor is connected to ground,

    an input of the inverter (3162) is connected to the common point of the stray-capacitance boosting unit (313) and the sampling resistor,

    an output of the inverter (3162) is connected to a negative terminal of the comparator (3164),

    a positive terminal of the comparator (3164) is configured to receive a reference voltage,

    an output of the comparator (3164) is connected to a first input of the "AND" gate (3166),

    a second input of the "AND" gate (3166) is configured to receive a gate pulse, and

    an output of the "AND" gate is configured to output several number of pulses corresponding to the capacitance of the parasitic capacitor; and wherein the open circuit detecting system (310) is configured to acquire an electrical signal from the object circuit (320) and based on said electrical signal to determine whether the object circuit (320) is in a normal circuit status or in an open circuit status by determining the capacitance of the parasitic capacitor (330), wherein

    the capacitance of the parasitic capacitor (330) in a normal circuit status is greater than the capacitance of the parasitic capacitor (330) in an open circuit status.


     
    2. The open circuit detecting system as claimed in claim 1, wherein the test unit (312) is configured to generate a burst pulse for charging the parasitic capacitor (330), and the sampling unit (314) is configured to discharge the charged parasitic capacitor (330).
     
    3. The open circuit detecting system (310) as claimed in claim 2, wherein the rising edge of the burst pulse is before the falling edge of the burst pulse.
     
    4. The open circuit detecting system (310) as claimed in any of the preceding claims, wherein the stray-capacitance boosting unit (313) is an Insulated Gate Bipolar Transistor, a triode, or a Darlington Transistor.
     
    5. A method for detecting an open circuit status of an object circuit (320) using the open circuit detecting system (310) as claimed in any of claims 1 to 4, comprising the steps of:

    acquiring an electrical signal corresponding to the parasitic capacitor (330) that exists between the object circuit (320) and ground, said parasitic capacitor (330) having a characteristic impedance, which represents all the parasitic capacitance that exists between conductors, conductors or components and ground, or the capacitance that exists between components; and

    determining whether the object circuit (320) is in an open circuit status or in a normal circuit status according to the electrical signal by determining the capacitance of the parasitic capacitor (330); wherein

    the capacitance of the parasitic capacitor (330) in a normal circuit status is greater than the capacitance of the parasitic capacitor (330) in an open circuit status.


     
    6. A method for detecting open circuit using the open circuit detecting system (310) s claimed in any of claims 1 to 4, wherein a parasitic capacitor (330) exists between the object circuit (320) and ground, said parasitic capacitor (330) having a characteristic impedance, which represents all the parasitic capacitance that exists between conductors, conductors or components and ground, or the capacitance that exists between components;
    said method comprising the steps of:

    testing the capacitance of the parasitic capacitor (330) and generating an electrical signal representing the capacitance of the parasitic capacitor (330); and

    determining whether the object circuit is in an open circuit status or in a normal circuit status according to the electrical signal; wherein

    the capacitance of the parasitic capacitor (330) in a normal circuit status is greater than the capacitance of the parasitic capacitor (330) in an open circuit status.


     
    7. The method as claimed in claim 6, wherein the step of testing comprises:

    generating a burst pulse for charging the parasitic capacitor (330), and

    discharging the parasitic capacitor (330) though a sampling unit (314) to generate the electrical signal.


     
    8. The method as claimed in claim 6, wherein the step of determining comprising:

    converting the electrical signal into an identification signal; and

    determining whether the object circuit is in the open circuit status according to the identification signal.


     
    9. An electronic device, comprising:

    an object circuit (130, 230, 330); and

    an open circuit detecting system (330) as claimed in any of claims 1 to 4.


     


    Ansprüche

    1. System (310) zur Erkennung eines offenen Schaltkreiszustandes einer Objektschaltung (320), wobei während der Bestimmung des offenen Schaltkreiszustandes der Objektschaltung (320) ein Ende des Systems (310) zur Erkennung des offenen Schaltkreiszustandes mit einer Masse verbunden ist und eine parasitäre Kapazität (330) zwischen der Objektschaltung (320) und Masse vorhanden ist, wobei die parasitäre Kapazität (330) einen Wellenwiderstand aufweist, der die gesamte parasitäre Kapazität bzw. Streukapazität darstellt, die zwischen Leitern, Leitern oder Bauelementen und Masse vorhanden ist, oder die Kapazität darstellt, die zwischen Bauelementen vorhanden ist,
    gekennzeichnet durch:

    eine Prüfeinheit (312), eine Streukapazitätserhöhungseinheit (313), eine Abtasteinheit (314) und eine Signalverarbeitungseinheit (316); wobei

    die Abtasteinheit (314) ein Abtastwiderstand ist,

    die Signalverarbeitungseinheit (316) einen Wechselrichter (3162), einen Komparator (3164), der mit dem Wechselrichter (3162) verbunden ist, und ein "UND"-Gate (3166) umfasst, das mit dem Komparator (3164) verbunden ist, wobei

    ein Ende der Prüfeinheit (312) mit einer Spannungsversorgung verbunden ist,

    das andere Ende der Prüfeinheit (312) mit einem ersten Eingang der Streukapazitätserhöhungseinheit (313) verbunden ist und ein zweiter Eingang der Streukapazitätserhöhungseinheit (313) mit der Objektschaltung (320) verbunden ist,

    ein Ausgang der Streukapazitätserhöhungseinheit (313) mit einem Ende des Abtastwiderstandes verbunden ist,

    das andere Ende des Abtastwiderstandes mit Masse verbunden ist,

    ein Eingang des Wechselrichters (3162) mit einem gemeinsamen Anschluss der Streukapazitätserhöhungseinheit (313) und dem Abtastwiderstand verbunden ist,

    ein Ausgang des Wechselrichters (3162) mit einen Minus-Anschluss des Komparators (3164) verbunden ist,

    ein Plus-Anschluss des Komparators (3164) für den Empfang einer Referenzspannung ausgelegt ist,

    ein Ausgang des Komparators (3164) mit einem ersten Eingang des "UND"-Gates (3166) verbunden ist,

    ein zweiter Eingang des "UND"-Gates (3166) ausgelegt ist, um mehrere Impulse entsprechend der Kapazität der parasitären Kapazität auszugeben; und wobei

    das System (310) zum Erkennen eines offenen Schaltkreiszustandes ausgelegt ist, um ein elektrisches Signal von dem Objektschaltkreis (320) zu erfassen und auf der Grundlage des elektrischen Signals zu bestimmen, ob sich der Objektschaltkreis (320) in einem normalen Schaltkreiszustand oder in einem offenen Schaltkreiszustand befindet, indem die Kapazität der parasitären Kapazität (330) bestimmt wird, wobei

    die Kapazität der parasitären Kapazität (330) in einem normalen Schaltkreiszustand größer ist als die Kapazität der parasitären Kapazität (330) in einem offenen Schaltkreiszustand.


     
    2. System zur Erkennung eines offenen Schaltkreiszustandes nach Anspruch 1, wobei die Prüfeinheit (312) ausgelegt ist, um einen Burst-Impuls zum Aufladen der parasitären Kapazität (330) zu erzeugen, und wobei die Abtasteinheit (314) ausgelegt ist, um die aufgeladene parasitäre Kapazität (330) zu entladen.
     
    3. System zur Erkennung eines offenen Schaltkreiszustandes (310) nach Anspruch 2, wobei die ansteigende Flanke des Burst-Impulses vor der abfallenden Flanke des Burst-Impulses liegt.
     
    4. System (310) zur Erkennung eines offenen Schaltkreiszustandes nach einem der vorhergehenden Ansprüche, wobei die Streukapazitätserhöhungseinheit (313) ein Bipolartransistor mit isoliertem Gate, eine Triode oder ein Darlingtontransistor ist.
     
    5. Verfahren zum Erkennen eines offenen Schaltkreiszustandes eines Objektschaltkreises (320) unter Verwendung des Systems (310) zur Erkennung eines offenen Schaltkreiszustandes nach einem der Ansprüche 1 bis 4, mit den Schritten:

    Erfassen eines elektrischen Signals, das der parasitären Kapazität (330) entspricht, die zwischen dem Objektschaltkreis (320) und Masse vorhanden ist, wobei die parasitäre Kapazität (330) einen Wellenwiderstand aufweist, der die gesamte parasitäre Kapazität bzw. Streukapazität darstellt, die zwischen Leitern, Leitern oder Bauelementen und Masse vorhanden ist, oder die Kapazität darstellt, die zwischen Bauelementen vorhanden ist; und

    Bestimmen, ob sich der Objektschaltkreis (320) in einem offenen Schaltkreiszustand oder in einem normalen Schaltkreiszustand befindet, und zwar entsprechend dem elektrischen Signal durch Bestimmen der Kapazität der parasitären Kapazität (330); wobei

    die Kapazität der parasitären Kapazität (330) in einem normalen Schaltkreiszustand größer ist als die Kapazität der parasitären Kapazität (330) in einem offenen Schaltkreiszustand.


     
    6. Verfahren zur Erkennung eines offenen Schaltkreiszustandes unter Verwendung des Systems (310) zur Erkennung eines offenen Schaltkreiszustandes nach einem der Ansprüche 1 bis 4, wobei eine parasitäre Kapazität (330) zwischen der Objektschaltung (320) und Masse vorhanden ist, wobei die parasitäre Kapazität (330) einen Wellenwiderstand aufweist, der die gesamte parasitäre Kapazität bzw. Streukapazität darstellt, die zwischen Leitern, Leitern oder Bauelementen und Masse vorhanden ist, oder die Kapazität darstellt, die zwischen Bauelementen vorhanden ist,
    wobei das Verfahren die Schritte aufweist:

    Prüfen der Kapazität der parasitären Kapazität (330) und Erzeugen eines elektrischen Signals, das die Kapazität der parasitären Kapazität (330) darstellt; und

    Bestimmen entsprechend dem elektrischen Signal, ob sich der Objektschaltkreis in einem offenen Schaltkreiszustand oder in einem normalen Schaltkreiszustand befindet; wobei

    die Kapazität der parasitären Kapazität (330) in einem normalen Schaltkreiszustand größer ist als die Kapazität der parasitären Kapazität (330) in einem offenen Schaltkreiszustand.


     
    7. Verfahren nach Anspruch 6, wobei der Schritt des Prüfens umfasst:

    Erzeugen eines Burst-Impulses zum Aufladen der parasitären Kapazität (330); und

    Entladen der parasitären Kapazität (330) durch eine Abtasteinheit (314) zur Erzeugung des elektrischen Signals.


     
    8. Verfahren nach Anspruch 6, wobei der Schritt des Bestimmens, umfasst:

    Umwandeln des elektrischen Signals in ein Identifikationssignal; und

    Feststellen entsprechend dem Identifikationssignal, ob sich der Objektschaltkreis in dem offenen Schaltkreiszustand befindet.


     
    9. Elektronische Vorrichtung, umfassend:

    einen Objektschaltkreis (130, 230, 330); und

    ein System (330) zur Erkennung eines offenen Schaltkreiszustandes nach einem der Ansprüche 1 bis 4.


     


    Revendications

    1. Un système de détection de circuit ouvert (310) pour déterminer un état de circuit ouvert d'un circuit objet (320), dans lequel durant la détermination de l'état de circuit ouvert du circuit objet (320) une extrémité du système de détection de circuit ouvert (310) est connecté à une terre et à une capacité parasite (330) et une capacité parasite (330) existe entre le circuit objet (320) et la terre, ladite capacité parasite (330) ayant une impédance caractéristique, qui représente toutes les capacités parasites existant entre les conducteurs, les conducteurs ou les composants et la terre, ou la capacité existant entre les composants,
    caractérisé par :

    une unité de test (312), une unité de stimulation de capacité parasite (313), une unité d'échantillonnage (314), et une unité de traitement de signal (316), dans laquelle

    l'unité d'échantillonnage (314) est une résistance d'échantillonnage,

    l'unité de traitement de signal (316) comporte un inverseur (3162), un comparateur (3164) connecté à l'inverseur (3162), et une porte « ET » (3166) connectée au comparateur (3164),

    une extrémité de l'unité de test (312) étant connectée à une alimentation électrique,

    l'autre extrémité de l'unité de test (312) étant connectée à une première entrée d'une unité de stimulation de capacité parasite (313), une seconde entrée de l'unité de stimulation de capacité parasite (313) étant connectée au circuit objet (320),

    une sortie de l'unité de stimulation de capacité parasite (313) étant connectée à une extrémité de la résistance d'échantillonnage,

    l'autre extrémité de la résistance d'échantillonnage étant connectée à la terre,

    une entrée de l'inverseur (3162) étant connectée au point commun de l'unité de stimulation de capacité parasite (313) et de la résistance d'échantillonnage,

    une sortie de l'inverseur (3162) étant connectée à une électrode négative du comparateur (3164),

    une électrode positive du comparateur (3164) étant configurée pour recevoir une tension de référence,

    une sortie du comparateur (3164) étant connectée à une première entrée de la porte « ET » (3166),

    une seconde entrée de la porte « ET » (3166) étant configurée pour recevoir une impulsion de porte, et

    une sortie de la porte « ET » étant configurée pour générer en sortie plusieurs impulsions correspondant à la capacitance de la capacité parasite ; et dans lequel

    le système de détection de circuit ouvert (310) est configuré pour acquérir un signal électrique du circuit objet (320) et de déterminer, sur la base dudit signal électrique, si le circuit objet (320) est dans un état de circuit normal ou dans un état de circuit ouverte en déterminant la capacité de la capacité parasite (330), dans lequel

    la capacité de la capacité parasite (330) en état de circuit normal est plus élevée que la capacité de la capacité parasite (330) en état de circuit ouvert.


     
    2. Le système de détection de circuit ouvert selon la revendication 1, dans lequel l'unité de test (312) est configurée pour générer une impulsion de salve pour charger la capacité parasite (330), et l'unité d'échantillonnage (314) est configurée pour décharger la capacité parasite (330) chargée.
     
    3. Le système de détection de circuit ouvert (310) selon la revendication 2, dans lequel le front montant de l'impulsion de salve est avant le front descendant de l'impulsion de salve.
     
    4. Le système de détection de circuit ouvert (310) selon l'une quelconque des revendications précédentes, dans lequel l'unité de stimulation de capacité parasite est un transistor bipolaire à porte isolée, une triode ou un transistor Darlington.
     
    5. Un procédé de détection d'un état de circuit ouvert d'un circuit objet (320) en utilisant le système de détection de circuit ouvert (310) tel que revendiqué dans l'une quelconque des revendications 1 à 4, comprenant les étapes :

    acquérir un signal électrique correspondant à la capacité parasite (330) existant entre un circuit objet (320) et la terre, ladite capacité parasite (330) ayant une impédance caractéristique, qui représente toutes les capacités parasites existantes entre les conducteurs, les conducteurs ou composants et la terre, ou la capacité existant entre les composants, et

    déterminer si le circuit objet (320) est dans un état de circuit ouvert ou dans un état de circuit normal en fonction du signal électrique en déterminant la capacité de la capacité parasite (330) ; dans lequel

    la capacité de la capacité parasite (330) en état de circuit normal est plus élevée que la capacité de la capacité parasite (330) en état de circuit ouvert.


     
    6. Un procédé de détection d'un circuit ouvert en utilisant le système de détection de circuit ouvert (310) tel que revendiqué dans l'une quelconque des revendications 1 à 4, dans lequel une capacité parasite (330) existe entre le circuit objet (320) et la terre, ladite capacité parasite (330) ayant une impédance caractéristique, qui représente toutes les capacités parasites existantes entre les conducteurs, les conducteurs ou composants et la terre, ou la capacité existant entre les composants, ledit procédé comprenant les étapes :

    tester la capacité de la capacité parasite (330) et générer un signal électrique représentatif de la capacité de la capacité parasite (330) ; et

    déterminer si le circuit objet est dans un état de circuit ouvert ou dans un état de circuit normal en fonction du signal électrique ; dans lequel

    la capacité de la capacité parasite (330) en état de circuit normal est plus élevée que la capacité de la capacité parasite (330) en état de circuit ouvert.


     
    7. Le procédé tel que revendiqué dans la revendication 6, dans lequel l'étape de test comporte :

    la génération d'une impulsion de salve pour charger ladite capacité parasite (330), et

    la décharge de la capacité parasite (330) au travers une unité d'échantillonnage (314) pour générer le signal électrique.


     
    8. Le procédé tel que revendiqué dans la revendication 6, dans lequel l'étape de détermination comporte :

    convertir le signal électrique en un signal d'identification ; et

    déterminer si le circuit objet est dans l'état de circuit ouvert en fonction du signal d'identification.


     
    9. Un dispositif électronique , comprenant :

    un circuit objet (130, 230, 330) ; et

    un système de détection de circuit ouvert (330) tel que revendiqué dans l'une quelconque des revendications 1 à 4.


     




    Drawing
























    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description