Apparatus and methods for testing the life of a leakage current protection device Number:7,522,064 from the United States Patent and Trademark Office (PTO) owispatent

Title: Apparatus and methods for testing the life of a leakage current protection device

Abstract: An apparatus for testing the life of a leakage current protection device, comprising a microcontroller unit, at least one of a first fault detector and a second fault detector, at least one of an audio alarm and a visual alarm, a power supply circuit. In operation, the first fault detector and/or the second fault detector receive at least one signal from the leakage current protection device, and generate at least one DC voltage corresponding to the at least one signal to be received by the MCU. The MCU compares the at least one DC voltage with a predetermined threshold value to determine whether a fault exists in the leakage current protection device, and activates the alarm circuit if at least one fault exists.

Patent Number: 7,522,064 Issued on 04/21/2009 to Zhang,   et al.

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Inventors:	Zhang; Feng (Shanghai, CN), Chen; Hongliang (Shanghai, CN), Wang; Fu (Yueqing Zhejiang, CN), Chen; Wusheng (Yueqing Zhejiang, CN), Zhang; Yulin (Shanghai, CN), Song; Huaiyin (Yueqing Zhejiang, CN)
Assignee:	General Protecht Group, Inc. (Zhejiang, CN)
Appl. No.:	11/588,016
Filed:	October 26, 2006

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Foreign Application Priority Data

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Dec 27, 2005 [CN]			2005 1 0132844

Current U.S. Class:	340/638
Current International Class:	G08B 21/00 (20060101)
Field of Search:	340/638,635,653,657,384.1 361/42 324/500

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References Cited [Referenced By]

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Primary Examiner: Nguyen; Phung
Attorney, Agent or Firm: Morris Manning Martin LLP Xia, Esq.; Tim Tingkang

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Claims

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What is claimed is:

1. An apparatus for testing the life of a leakage current protection device, wherein the leakage current protection device has a first input, a second input, a third input, a first output, a second output, a third output, a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output, a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output, and a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output, comprising: (i) a microcontroller unit (MCU) having a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input; (ii) a fault detection circuit having an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively; (iii) an alarm circuit having an input that is electrically coupled to the second output of the MCU, and a power supply input; and (iv) a power supply circuit having an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the power supply input of the alarm circuit, wherein, in operation, the fault detection circuit receives at least one signal from the second output and the third output of the leakage current protection device, and generates at least one DC voltage corresponding to the at least one signal to be received by at least one of the first input and second input of the MCU, and the MCU compares the at least one DC voltage with a predetermined threshold value to determine whether a fault exists in the leakage current protection device, and activates the alarm circuit if at least one fault exists.

2. The apparatus of claim 1, wherein the fault detection circuit comprises at least one of a first fault detector electrically coupled to the self-sustained oscillation circuit and a second fault detector electrically coupled to the trip coil circuit.

3. The apparatus of claim 2, wherein the first fault detector comprises a coupling and frequency selective processing circuit adapted for receiving an oscillation signal generated by the self-sustained oscillation circuit, filtering the oscillation signal, converting the filtered oscillation signal into a first DC voltage, and providing the first DC voltage to the second input of the MCU.

4. The apparatus of claim 3, wherein the MCU is programmed such that if the first DC voltage is greater than a first predetermined threshold value, no fault exists in the leakage current protection device, and if the first DC voltage is less than the first predetermined threshold value, at least one fault exists in the leakage current protection device.

5. The apparatus of claim 2, wherein the second fault detector comprises: (i) a power grid signal synchronization monitoring circuit adapted for generating a series of pulse signal that is synchronized with an AC power source grid; and (ii) a trip circuit detection circuit adapted for receiving and sending the series of pulse signal to a switching device, which has an anode, a gate, and a cathode, to set the switching device into a conductive state during the period when the voltage of the pulse signal is high, detecting a second DC voltage between the gate and the cathode of the switching device while the switching device is in the conductive state, and providing the second DC voltage to the first input of the MCU.

6. The apparatus of claim 5, wherein the MCU is programmed such that if the second DC voltage is greater than a second predetermined threshold value, no fault exists in the trip coil circuit of the leakage current protection device, and if the second DC voltage is less than the second predetermined threshold value, at least one fault exists in the leakage current protection device.

7. The apparatus of claim 1, wherein the MCU sends an alarm signal to the alarm circuit when the MCU determines that at least one fault exists, and the alarm circuit receives the alarm signal and generates an alarm.

8. The apparatus of claim 7, wherein the alarm circuit comprises at least one of an audio alarm circuit for generating an audible alarm and a visual alarm circuit for generating a visible alarm.

9. A method for testing the life of a leakage current protection device, wherein the leakage current protection device has a first input, a second input, a third input, a first output, a second output, a third output, a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output, a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output, and a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output, comprising the steps of: (i) providing a testing device having: (A) a microcontroller unit (MCU) having a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input; (B) a fault detection circuit having an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively; (C) an alarm circuit having an input that is electrically coupled to the second output of the MCU, and a power supply input; and (D) a power supply circuit having an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the alarm circuit, (ii) processing at least one signal from the second output and the third output of the leakage current protection device and providing at least one DC voltage to be received at least one of the first input and the second input of the MCU; (iii) comparing the value of the DC voltage to a predetermined threshold value by the MCU to determine whether a fault exists in the leakage current protection device, wherein the MCU is programmed such that if the DC voltage is greater than the predetermined threshold value, no fault exists in the leakage current protection device, and if the DC voltage is less than the predetermined threshold value, a fault exists in the leakage current protection device; and (iv) activating the alarm circuit by the MCU if a fault exists in the leakage current protection device to generate an alarm to alert users of the leakage current protection device.

10. The method of claim 9, wherein the processing signal step further comprising the steps of: (i) receiving a oscillation signal generated by a self-sustained oscillation circuit, wherein the self-sustained oscillation signal reflects the intrinsic frequency characteristics of the leakage current detection circuit; (ii) filtering the oscillation signal by a coupling and frequency selective processing circuit; (iii) converting the filtered oscillation signal into a first DC voltage; and (iv) providing the first DC voltage to the second input of the MCU.

11. The method of claim 9, wherein the processing signal step further comprising the steps of: (i) generating a series of pulse signal that is synchronized with an AC power source grid by a power grid signal synchronization monitoring circuit; (ii) receiving and sending the series of pulse signal to a switching device which has a anode, a cathode and a gate, by a trip circuit detection circuit; (iii) setting the switching device in a conductive state during the period when the voltage of the pulse signal is high; (iv) detecting a second DC voltage across the gate and the cathode of the switching device, while the switching device is in a conductive state; and (v) providing the second DC voltage to the first input of the MCU.

12. The method of claim 9, wherein the activating the alarm circuit step further comprising at least of one of following steps: (i) activating an audio alarm circuit for generating an audible alarm; and (ii) activating a visual alarm circuit for generating a visible alarm.

13. An leakage current protection device with life testing, comprising: (i) a leakage current protection device having: (A) a first input; (B) a second input; (C) a third input; (D) a first output; (E) a second output; (F) a third output; (G) a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output; (H) a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output; and (I) a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output; (ii) a microcontroller unit (MCU) having a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input; (iii) a fault detection circuit having an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively; (iv) an alarm circuit having an input that is electrically coupled to the second output of the MCU, and a power supply input; and (v) a power supply circuit having an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the alarm circuit, wherein, in operation, the fault detection circuit receives at least one signal from the second output and the third output of the leakage current protection device, and generates at least one DC voltage corresponding to the at least one signal to be received by at least one of the first input and second input of the MCU, and the MCU compares the at least one DC voltage with a predetermined threshold value to determine whether a fault exists in the leakage current protection device, and activates the alarm circuit if at least one fault exists.

14. The apparatus of claim 13, wherein the fault detection circuit comprises at least one of a first fault detector electrically coupled to the self-sustained oscillation circuit and a second fault detector electrically coupled to the trip coil circuit.

15. The apparatus of claim 14, wherein the first fault detector comprises a coupling and frequency selective processing circuit adapted for receiving an oscillation signal generated by the self-sustained oscillation circuit, filtering the oscillation signal, converting the filtered oscillation signal into a first DC voltage, and providing the first DC voltage to the second input of the MCU.

16. The apparatus of claim 15, wherein the MCU is programmed such that if the first DC voltage is greater than a first predetermined threshold value, no fault exists in the leakage current protection device, and if the first DC voltage is less than the first predetermined threshold value, at least one fault exists in the leakage current protection device.

17. The apparatus of claim 14, wherein the second fault detector comprises: (i) a power grid signal synchronization monitoring circuit adapted for generating a series of pulse signal that is synchronized with an AC power source grid; and (ii) a trip circuit detection circuit adapted for receiving and sending the series of pulse signal to a switching device, which has an anode, a gate, and a cathode, to set the switching device into a conductive state during the period when the voltage of the pulse signal is high, detecting a second DC voltage between the gate and the cathode of the switching device while the switching device is in the conductive state, and providing the second DC voltage to the first input of the MCU.

18. The apparatus of claim 17, wherein the MCU is programmed such that if the second DC voltage is greater than a second predetermined threshold value, no fault exists in the trip coil circuit of the leakage current protection device, and if the second DC voltage is less than the second predetermined threshold value, at least one fault exists in the leakage current protection device.

19. The apparatus of claim 13, wherein the MCU sends an alarm signal to the alarm circuit when the MCU determines that at least one fault exists, and the alarm circuit receives the alarm signal and generates an alarm.

20. The apparatus of claim 19, wherein the alarm circuit comprises at least one of an audio alarm circuit for generating an audible alarm and a visual alarm circuit for generating a visible alarm.

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Description

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CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Chinese Patent Application No. 200510132844.2, filed on Dec. 27, 2005, entitled "Intelligent Life Testing Methods and Apparatus for Leakage Current Protection Device" by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG, the disclosure of which is incorporated herein by reference in its entirety.

This application is related to four co-pending U.S. patent applications, entitled "Intelligent Life Testing Methods and Apparatus for Leakage Current Protection Device with Indicating Means," by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG, Ser. No. 11/588,017; "Intelligent Life Testing Methods and Apparatus for Leakage Current Protection," by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG; Ser. No. 11/588,163; "Intelligent Life Testing Methods and Apparatus for Leakage Current Protection," by Wusheng CHEN, Fu WANG, and Lianyun WANG, Ser. No. 11/588,046; and "Intelligent Life Testing Methods and Apparatus for Leakage Current Protection," by Feng ZHANG, Hongliang CHEN, Fu WANG, Wusheng CHEN, Yulin ZHANG and Huaiyin SONG, Ser. No. 11/588,048, respectively. The above identified co-pending applications were filed on the same day that this application was filed, and with the same assignee as that of this application. The disclosures of the above identified co-pending applications are incorporated herein by reference in their entireties.

FIELD OF THE PRESENT INVENTION

The present invention generally relates to real time detection of fault of a leakage current protection device. More particularly, the present invention relates to apparatus and methods for testing the life of a leakage current protection device.

BACKGROUND OF THE PRESENT INVENTION

Leakage current protection can be divided into two categories according to their functionalities: ground fault circuit interrupter (hereinafter "GFCI") and arc fault circuit interrupter (hereinafter "AFCI"). In order to achieve the goal of leakage current protection, a leakage current protection device used for appliances comprises at least two components: a trip mechanism and a leakage current detection circuit. The trip mechanism comprises a silicon controlled rectifier (hereinafter "SCR"), trip coil, and trip circuit interrupter device. The leakage current detection circuit comprises induction coils, a signal amplifier and a controller.

The operating principle of a GFCI used for appliances is as follows. In a normal condition, the electric current on a hot wire of an electrical socket should be the same as the electric current on a neutral wire in the same electrical socket. When a leakage current occurs, there exists a current differential between the hot wire and the neutral wire of the electrical socket. The inductive coil of the leakage current protection device monitors the current differential and transfers the current differential into a voltage signal. The voltage signal is then amplified by the signal amplifier and sent to the controller. If the current differential exceeds a predetermined threshold, the controller sends a control signal to the trip circuit interrupter to cut off the connection between the AC power and the appliance to prevent damage caused by the leakage current.

For an AFCI used for appliances, in a normal condition, the electric current on a hot wire of an electrical socket should be the same as the electric current on a neutral wire in the same electrical socket, and the variation of both the electric current is same. When an arc fault occurs due to aging or damages of the AFCI device, the current or voltage between the hot wire and the neutral wire of the electrical socket exhibits a series of repeated pulse signals. The inductive coil of the arc fault protection device detects the pulse signals and converts the pulse signals to a voltage signal. The voltage signal is amplified by the signal amplifier and sent to the controller. If the amplitude of the pulse signals or the their occurring frequency exceed certain predetermined threshold, the controller sends a control signal to the trip circuit interrupter to cut off the connection between the AC power and the appliance to prevent further damage caused by the arc fault.

Leakage current protection devices have been widespreadly used because of their superior performance. However, the leakage protection devices may fail to provide such leakage current protection, if they are installed improperly and/or they are damaged due to aging. If a faulty controller can not output a correct control signal, or a trip mechanism fails to cut off the connection between the AC power and the appliance, the leakage current protection device will not be able to provide the leakage current protection, which may cause further damages or accidents. Although most leakage current protection devices are equipped with a manual testing button, usually, users seldom use the manual testing button. Therefore, the leakage current protection devices need an additional circuit to automatically detect malfunctions, faults or the end of the life of such devices. The great relevance would be gained if a leakage current protection device is capable of automatically detecting a fault therein or its end of the life, and consequently alerting a user to take an appropriate action including repairing or replacing the leakage current detection circuit.

Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.

SUMMARY OF THE PRESENT INVENTION

In one aspect, the present invention relates to an apparatus for testing the life of a leakage current protection device. The leakage current protection device has a first input, a second input, a third input, a first output, a second output, a third output, a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output, a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output, and a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output. In one embodiment, the apparatus comprises: (i) a microcontroller unit (MCU), (ii) a fault detection circuit, (iii) an alarm circuit, and (iv) a power supply circuit.

The MCU has a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input. The fault detection circuit has an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively. The alarm circuit has an input that is electrically coupled to the second output of the MCU, and a power supply input. The power supply circuit has an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the power supply input of the alarm circuit.

When this apparatus is in operation, the fault detection circuit receives at least one signal from the second output and the third output of the leakage current protection device, and generates at least one DC voltage corresponding to the at least one signal. The at least one DC voltage is received by at least one of the first input and second input of the MCU. The MCU compares the at least one DC voltage with a predetermined threshold value to determine whether a fault exists in the leakage current protection device. The alarm circuit is activated if at least one fault exists.

In one embodiment, the fault detection circuit has at least one of a first fault detector electrically coupled to the self-sustained oscillation circuit and a second fault detector electrically coupled to the trip coil circuit.

The first fault detector has a coupling and frequency selective processing circuit. The coupling and frequency selective processing circuit receives an oscillation signal generated by the self-sustained oscillation circuit, filters the oscillation signal, converts the filtered oscillation signal into a first DC voltage, and provides the first DC voltage to the second input of the MCU. The MCU is programmed such that if the first DC voltage is greater than a first predetermined threshold value, no fault exists in the leakage current protection device, and if the first DC voltage is less than the first predetermined threshold value, at least one fault exists in the leakage current protection device.

The second fault detector comprises: (i) a power grid signal synchronization monitoring circuit, (ii) a trip circuit detection circuit. The power grid signal synchronization monitoring circuit generates a series of pulse signal that is synchronized with an AC power source grid. The trip circuit detection circuit receives and sends the series of pulse signal to a switching device, which has an anode, a gate, and a cathode. The series of pulse signal sets the switching device into a conductive state during the period when the voltage of the pulse signal is high. A second DC voltage is measured between the gate and the cathode of the switching device while the switching device is in the conductive state. The second DC voltage is electrically coupled to the first input of the MCU. The MCU is programmed such that if the second DC voltage is greater than a second predetermined threshold value, no fault exists in the trip coil circuit of the leakage current protection device, and if the second DC voltage is less than the second predetermined threshold value, at least one fault exists in the leakage current protection device.

If the MCU determines that at least one fault exists, the MCU sends an alarm signal to the alarm circuit. The alarm circuit receives the alarm signal and generates an alarm. The alarm circuit comprises at least one of an audio alarm circuit for generating an audible alarm and a visual alarm circuit for generating a visible alarm.

In another aspect, the present invention relates to a method for testing the life of a leakage current protection device. The leakage current protection device has a first input, a second input, a third input, a first output, a second output, a third output, a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output, a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output, and a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output. In one embodiment, the method comprises the step of (i) providing a testing device. This testing device has (1) a microcontroller unit (MCU) that has a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input, (2) a fault detection circuit that has an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively, (3) an alarm circuit that has an input that is electrically coupled to the second output of the MCU, and a power supply input, and (4) a power supply circuit that has an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the alarm circuit.

The method further comprises the steps of: (ii) processing at least one signal from the second output and the third output of the leakage current protection device and providing at least one DC voltage to be received at least one of the first input and the second input of the MCU, (iii) comparing the value of the DC voltage to a predetermined threshold value by the MCU to determine whether a fault exists in the leakage current protection device, (iv) activating the alarm circuit by the MCU if a fault exists in the leakage current protection device to generate an alarm to alert users of the leakage current protection device. The MCU is programmed such that if the DC voltage is greater than the predetermined threshold value, no fault exists in the leakage current protection device, and if the DC voltage is less than the predetermined threshold value, a fault exists in the leakage current protection device.

In one embodiment, the processing signal step further comprises the steps of: (i) receiving a oscillation signal generated by a self-sustained oscillation circuit which reflects the intrinsic frequency characteristics of the leakage current detection circuit, (ii) filtering the oscillation signal by a coupling and frequency selective processing circuit, (iii) converting the filtered oscillation signal into a first DC voltage, and (iv) providing the first DC voltage to the second input of the MCU.

In another embodiment, the processing signal step further comprises the steps of: (i) generating a series of pulse signal that is synchronized with an AC power source grid by a power grid signal synchronization monitoring circuit, (ii) receiving and sending the series of pulse signal to a switching device which has a anode, a cathode and a gate, by a trip circuit detection circuit, (iii) setting the switching device in a conductive state during the period when the voltage of the pulse signal is high, (iv) detecting a second DC voltage across the gate and the cathode of the switching device, while the switching device is in a conductive state, and (v) providing the second DC voltage to the first input of the MCU.

The activating the alarm circuit step of the method further includes at least of one of following steps: (i) activating an audio alarm circuit for generating an audible alarm, and (ii) activating a visual alarm circuit for generating a visible alarm.

In yet another aspect, the present invention relates to a leakage current protection device with life testing capacity. In one embodiment, the leakage current protection device with life testing capacity includes (i) a leakage current protection device, (ii) a microcontroller unit (MCU), (iii) a fault detection circuit, (iv) an alarm circuit, and (v) a power supply circuit.

In one embodiment, the leakage current protection device has a first, second and third input, a first, second and third output, a self-sustained oscillation circuit that is electro-magnetically coupled therebetween the first input and the second input, and electrically coupled to the third output, a reset circuit with an input that is electrically coupled to the third input, and an output that is electrically coupled to the first output, and a trip coil circuit with an input that is electrically coupled to the output of the reset circuit and the first output, and an output that is electrically coupled to the second output.

In one embodiment, the MCU has a first input, a second input, a first output that is electrically coupled to the third input of the leakage current protection device, a second output, and a power supply input. The fault detection circuit has an first input that is electrically coupled to the second output of the leakage current protection device, a second input that is electronically coupled to the third output of the leakage current protection device, a first output that is electrically coupled to the first input of the MCU, and a second output that is electrically coupled to the second input of the MCU, respectively. The alarm circuit has an input that is electrically coupled to the second output of the MCU, and a power supply input. The power supply circuit has an input that is electrically coupled to the first output of the leakage current protection device, and an output that is electrically coupled to the power supply input of the MCU and the alarm circuit.

When this device is in operation, the fault detection circuit receives at least one signal from the second output and the third output of the leakage current protection device, and generates at least one DC voltage corresponding to the at least one signal. The at least one DC voltage is received by at least one of the first input and second input of the MCU. The MCU compares the at least one DC voltage with a predetermined threshold value to determine whether a fault exists in the leakage current protection device. The alarm circuit is activated if at least one fault exists.

In one embodiment, the fault detection circuit includes at least one of a first fault detector electrically coupled to the self-sustained oscillation circuit and a second fault detector electrically coupled to the trip coil circuit.

The first fault detector has a coupling and frequency selective processing circuit. The coupling and frequency selective processing circuit receives an oscillation signal generated by the self-sustained oscillation circuit, filters the oscillation signal, converts the filtered oscillation signal into a second DC voltage, and provides the second DC voltage to the second input of the MCU. The MCU is programmed such that if the second DC voltage is greater than a second predetermined threshold value, no fault exists in the leakage current protection device, and if the second DC voltage is less than the second predetermined threshold value, at least one fault exists in the leakage current protection device.

The second fault detector has: (i) a power grid signal synchronization monitoring circuit, (ii) a trip circuit detection circuit. The power grid signal synchronization monitoring circuit generates a series of pulse signal that is synchronized with an AC power source grid. The trip circuit detection circuit receives and sends the series of pulse signal to a switching device, which has an anode, a gate, and a cathode. The series of pulse signal sets the switching device into a conductive state during the period when the voltage of the pulse signal is high. A first DC voltage is measured between the gate and the cathode of the switching device while the switching device is in the conductive state. The first DC voltage is electrically coupled to the first input of the MCU. The MCU is programmed such that if the first DC voltage is greater than a first predetermined threshold value, no fault exists in the trip coil circuit of the leakage current protection device, and if the first DC voltage is less than the first predetermined threshold value, at least one fault exists in the leakage current protection device.

If the MCU determines that at least one fault exists, the MCU sends an alarm signal to the alarm circuit. The alarm circuit receives the alarm signal and generates an alarm. The alarm circuit includes at least one of an audio alarm circuit for generating an audible alarm and a visual alarm circuit for generating a visible alarm.

These and other aspects of the present invention will become apparent from the following description of the preferred embodiment taken in conjunction with the following drawings, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and benefits of the present invention will be apparent from a detailed description of preferred embodiments thereof taken in conjunction with the following drawings, wherein similar elements are referred to with similar reference numbers, and wherein:

FIG. 1A shows one block diagram of a leakage current protection device with life testing capacity according to one embodiment of the present invention.

FIG. 1B shows a more detailed diagram of a leakage current protection device with life test according to another embodiment of the present invention.

FIG. 2 shows a circuit diagram of apparatus for testing the life of a leakage current protection device according to one embodiment of the present invention.

FIG. 3 shows a power grid synchronized half wave signal measured from a power grid synchronization monitoring circuit 204 as shown in FIG. 2, according to one embodiment of the present invention.

FIG. 4 shows signal wave form from a self-sustained oscillator when the leakage current detection circuit, which has inductive coils L1 and L2, is working properly, according to one embodiment of the present invention.

FIG. 5 shows the interaction between the output of the MCU and the gate of the trip SCR SCR102 as shown in FIG. 2, when the trip coil and the trip SCR are working properly, according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Prior to a detailed description of the present invention(s), the following definitions are provided as an aid to understanding the subject matter and terminology of aspects of the present invention(s), and not necessarily limiting of the present invention(s), which are expressed in the claims. Whether or not a term is capitalized is not considered definitive or limiting of the meaning of a term. As used in this document, a capitalized term shall have the same meaning as an uncapitalized term, unless the context of the usage specifically indicates that a more restrictive meaning for the capitalized term is intended. A capitalized term within the glossary usually indicates that the capitalized term has a separate definition within the glossary. However, the capitalization or lack thereof within the remainder of this document is not intended to be necessarily limiting unless the context clearly indicates that such limitation is intended. The terms "unit" and "circuit" are interchangeable.

A switching device usually can be in two states: a conductive state and a non-conductive state. When the switching device is in the conductive state, a current is allowed to pass through. When the switching device is in the non-conductive state, no current is allowed to pass through.

Definitions/Glossary

AC: alternate current

AFCI: arc fault circuit interrupter.

GFCI: ground fault circuit interrupter.

KHz: kilo-hertz.

LED: light emitting diode.

MCU: MicroController Unit.

SCR: silicon controlled rectifier.

Descriptions

A key switching component of a trip mechanism of a leakage current protection device is usually an SCR. When leakage current or arc fault occurs, the conduction of current through the SCR must be guaranteed. Otherwise, the trip coil circuit will be broken and the trip mechanism will fail to operate properly.

In order to check whether the trip coil conducts current, the trip coil is tested to