Circuit protection device with automatic fault monitoring and detection function

A circuit protection device with self fault detection function comprises a ground fault protection unit and a self fault detection unit, the ground fault protection unit can achieve the ground fault detection and protection function for AC power source power circuit and electrical appliance. The self fault detection unit is provided with two delay circuits which can achieve the fault detection at an early stage of power-on and periodically fault detection function. The ground fault protection circuit and the self fault detection unit can operate in time sharing, and achieve self fault detection without interruption of power supply. The self fault detection unit and the ground fault protection unit are separated from high impedance. Any fault occurred on any element in the self fault detection unit may not impair the protection ability of the ground fault protection unit.

The present application claims the priority benefit of Chinese Application No. 201510206672.2, filed Apr. 27, 2015, which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an electrical circuit protection technology field, and in particular, it relates to an electrical circuit protection device for automatic monitoring and detecting operation faults, more specifically, a leakage or residual current protection device or a ground-fault circuit interrupter device. The circuit protection device can automatically detect the operation condition, and send alarming signal in case of operation fault.

BACKGROUND OF THE INVENTION

The leakage current protection device, or ground fault circuit interrupter, is used to detect the ground fault current in electronics, instruments, devices, equipments and electrical systems that are powered by electric grid as well as power supply system. When the ground fault current exceeds specified limit, the circuit protection device will automatically shut down the power supply and so as to protect human being and properties. In actual application, the leakage current protection device or ground fault circuit interrupter may partly or wholly malfunction, and the protection function of the ground fault circuit interrupter thereby malfunction, and the users may not be aware of the situation, thus safety risk may occur.

To solve the problems above, some leakage current protection devices are designed according to IEC 61008-1, IEC 61009-1, GB 6829.1 standards and have a test button, but require a user to manually depress the test button periodically, once a month, to test whether the circuit protection function is working properly. For one aspect, it increases user's workload, and for another, the periodic test must cut down the power supply, and cause inconvenience to user. For the third, if the user does not periodically test the circuit, or the circuit protection device malfunctions during two periodic test periods (such as one month), and safety risk may occur.

To solve the problems above, some ground fault circuit interrupters designed according to UL 943 standard are provided with a self fault detection unit to periodically detect and diagnose the working condition of the ground fault circuit interrupter. However, the circuit and structure of the self fault detection device is too complex, and the manufacturing is difficult, the cost of product is too high, or the practicality is low, which results in the decreased reliability of the original circuit protection function of the circuit protection device due to the additional self detection circuit, and safety risk may occur.

SUMMARY OF THE INVENTION

The present invention is the extension of patent CN 101295609B, to provide a circuit protection device with automatic fault detection function. The contents described in patent CN101295609B will be quoted in the present application. The technical problem to be solved by the present invention is to provide a self fault detection circuit at the early stage of power-on for the circuit protection device. The other technical problem to be solved by the present invention is to provide a periodic self fault detection circuit for the circuit protection device. The further technical problem to be solved by the present invention is to supply a self fault detection circuit without interruption of power for load terminals of the circuit protection device. The still another technical problem to be solved by the present invention is to supply a self fault detection circuit without impairing the safety protection function of the protection circuit for the circuit protection device.

To solve the technical problems above, the technical scheme adopted in the present invention is as follows:

A circuit protection device with an automatic fault detection function, comprises a ground fault protection unit1and a self fault detection unit2, wherein the ground fault protection unit1can achieve the ground fault protection function; wherein the self fault detection unit2automatically detects the operation condition of the ground fault protection unit1, and achieves the self fault detection function. The ground fault protection unit1comprising: a ground fault detection circuit101, an AC power source path102and a solenoid driving circuit104, wherein the ground fault detection circuit101is used to detect the ground fault current generated on the AC power source path102, and drive the solenoid driving circuit104to activate, and disconnect or connect the electrical path of the AC power source path102. The self fault detection unit2comprises an self-test circuit201, a measurement and control circuit202and an alarming circuit203, wherein the self-test circuit201generates ground fault current used for fault self detection to the ground fault protection unit1under the control of the measurement and control circuit202, the measurement and control circuit202detects the fault signal from the ground fault protection unit1, and determine the operation condition of the ground fault protection unit1, and send an alarming signal via the alarming circuit203.

The ground fault detection circuit101, comprises a ground fault current sensor150, a grounded neutral sensor160, a first DC power source180and a ground fault detection chip170, wherein the ground fault detection chip170is used to detect the ground fault signal output from the ground fault current sensor150and the grounded neutral sensor160, and output a trip signal to trigger the solenoid driving circuit104. The first DC power source180is connected to the input terminals of AC power source, and generate direct current to power the ground fault detection chip170, the cathode of the first DC power source180acts as the internal logic ground (GND) of the circuit protection device.

The AC power source path102comprises a first and a second AC power source terminals (T1, T2) for connecting AC power source, load terminals26,27and/or power receptacles34A/34B for connecting with load, a magnetic switch88of electrical path for connecting or disconnecting first and second AC power source terminals T1, T2, and load terminals26,27, and/or power receptacles34A/34B. The first and second AC power source terminals T1, T2are connected with the moving contacts of the magnetic switch88through conductors91,92, and load terminals26,27and/or power receptacles34A/34B are connected with the static contacts of the magnetic switch88.

The solenoid driving circuit104comprises a diode143, a trip coil142, a silicon controlled rectifier (SCR)141, a resistance146, a capacitor147and a rectifier diode188, wherein the anode of the diode143is connected with the first AC power source terminal T1, the cathode of the diode143is connected with the anode of the SCR141through the trip coil142, the cathode of the SCR141is connected with GND, the anode of the rectifier diode188is connected with GND, and the cathode of the rectifier diode188is connected with the second AC power source terminal T2, the control pole of the SCR141is connected with an output end of the ground fault detection chip170via the resistance146, and the capacitor147is connected between the control pole of the SCR141and GND, and the trip coil142is used to drive the magnetic switch88.

The ground fault protection unit1further comprises a manual test circuit103, the manual test circuit103is used to manually trigger and generate a ground fault current on the AC power source path102, and the manual test circuit103comprises the ground fault test switch35and A resistance131which are serially connected, and the manual test circuit103is connected between the first and the second AC power source terminals T1, T2.

The self-test circuit201comprises a ground fault resistance215, a rectifier diode189and a self-test triode211, wherein the collector of the self-test triode211is connected, through the ground fault resistance215, with the conductor92which passes through the grounded neutral sensor160and the ground fault current sensor150, the conductor92is connected with the second AC power source terminal T2, and the emitter of the self-test triode211is connected with the first AC power source terminal T1after passing through the rectifier diode189.

The measurement and control circuit202comprises: a first fault signal input circuit branch240, used to transmit the condition signal of the trip coil142in real time; a second fault signal input circuit branch250, used to transmit the operation condition signal of the ground fault detection circuit101and the SCR141; a detection chip263, which is used to receive and detect in real time the output signals from the first fault signal input circuit branch240and the second fault signal input circuit branch250, and start periodically fault self detection process, and determine the operation condition of the ground fault protection unit1, and send the operation condition signal to the alarming circuit203; and a second DC power source270, wherein its output V2is used to supply DC power to the self fault detection unit2, and the cathode of the second DC power source270is connected with GND.

The input end of the first fault signal input circuit branch240is further connected between the anode of the SCR141and the trip coil142, its output voltage VB1is connected with the detection chip263, the first fault signal input circuit branch240comprises at least one capacitor242, AC power source is connected with the diode143and the trip coil142, and then to a resistance241, and the capacitor242is charged, so as to raise voltage on the capacitor242, and then raise the VB1. The first fault signal input circuit branch240forms a delay circuit, when the diode143and the trip coil142have no fault, the VB1will be increased from 0V to a preset reference voltage VH1during predetermined time period TR1. When the diode143and/or the trip coil142is disconnected, the VB1will be decreased to a preset reference voltage VL1during predetermined time period, wherein VH1is smaller than the V2, and VL1is smaller than or equal to VH1.

The second fault signal input circuit branch250, its input end is connected with the anode of the SCR141, its output voltage VB2is connected to the detection chip263, the second fault signal input circuit branch250comprises a capacitor252, the second DC power source270, charges the capacitor252through the resistance253, and/or charges the capacitor252by the detection chip263via the diode268, and make the voltage on the capacitor252raise, so that the VB2is raised. When the SCR141becomes conductive, the charge on the capacitor252are released by the SCR141via the diode251, and so that the VB2is decreased. The second fault signal input circuit branch250forms the other delay circuit, when the SCR141becomes non-conductive, the VB2will be increased to the preset reference voltage VH2. When the SCR141becomes conductive, the VB2will be decreased to a preset reference voltage VL2, wherein VH2is smaller than the V2and VL2is smaller than or equal to VH2.

The detection chip263further detects the VB1, and controls the charge current of the capacitor252. When the VB1is greater than the VH1, or the VB1is decreased from VH1to a value greater than or equal to the VL1, the capacitor252is charged with a lower rate, so that the VB2is increased slowly from the VL2to a value greater than the VH2during predetermined time period TR21. When the VB1is smaller than VL1, or during the VB1is increased from a value smaller than VL1to a value smaller than or equal to VH1, the capacitor252is charged in a higher rate, so that the VB2is increased from a value smaller than VL2to a value greater than VH2during a predetermined time period TR22(TR22is less than TR21).

The output of the detection chip263is connected with a base pole of the self-test triode211via a resistance218, when the VB2is greater than the VH2, or during the process when the VB2is gradually decreased from a value greater than VH2to a value greater than or equal to the VL2, the output VOUT of the detection chip263is high level, so that the self-test triode211becomes conductive. When the VB2is smaller than VL2, or during the process the VB2is increased from a value smaller than VL2to a value smaller than or equal to VH2, the output VOUT of the detection chip263is at a low level, and the self-test triode211becomes non-conductive.

When the output VOUT of the detection chip263is transferred to a high level from a low level, the measurement and control circuit202starts a self fault detection process. During the self detection process, the ground fault detection circuit101triggers the SCR141to become conductive, and the VB2is decreased from a value greater than VH2to a value smaller than the VL2, the output VOUT of the detection chip263is transferred from a high level to a low level, and the self fault detection process is completed.

At the initial stage of power-on, the measurement and control circuit202carries out one or several self fault detection process according to the predetermined time period TR22during the preset time period TR1. If the ground fault protection unit1has no fault, the measurement and control circuit202sends the prompt signal “System ok”, and the alarming circuit203flashes one time or several times.

Alternatively, the measurement and control circuit202carries out one or several self fault detection process periodically, the periodic time is equal to the time period TR21. If the ground fault protection unit1has no fault, the measurement and control circuit202sends the prompt signal “System ok” during each self fault detection process, and the alarming circuit203flashes one time.

The self fault detection process above is used during the initial stage of power-on, and it is a self detection with a high frequency, and it is only performed during the short time period TR1at the initial stage of power-on. During the time period TR1, the self fault detection process is performed for one time or several times with time interval of TR22.

The self fault detection process above is also used during the normal operation, which is a self detection process with lower frequency, and performed repeatedly according to predetermined time period, the time interval is TR21, TR21is much greater than TR22. When the ground fault protection unit1malfunctions, the device exits the periodic self detection with a low frequency, and enters the self detection with a high frequency.

Further, during the self fault detection process, when faults occur to the ground fault detection circuit101and/or the SCR141, and the SCR141becomes non-conductive, the self fault detection process cannot be completed normally, the measurement and detection circuit202sends alarming signal “System Fault”, and the alarming circuit203sends continuous red flicker, or rapid flicker.

When the trip coil142is disconnected, the measurement and control circuit202will continuously perform the self fault detection process according to a predetermined time period TR22, and send alarming signal “System fault”, and the alarming circuit203will flicker rapidly with red light.

When the anode of the SCR141is short to the ground, the measurement and control circuit202will not start the self fault detection periodically, the alarming circuit203will not flicker periodically, or the alarming circuit203flashes rapidly, and send the alarming signal “System fault”.

The diode251in the second fault signal input circuit branch250plays the unilateral conductive role in the circuit, when it is at positive conductive cycle, it supplies the electric path to release the charge in the capacitor252. When it becomes non-conductive, it can achieve the high impedance between the trip coil142and the second ground fault signal input circuit branch250. The total resistance of the resistance241of the first fault signal input circuit branch240is greater than 1 MΩ, and used to achieve the high impedance separation between the ground fault protection unit1and the self fault detection unit2.

According to the present invention, the first AC power source terminal T1is connected with the phase line of the AC power source, and the second AC power source terminal T2is connected with the neutral line of the AC power source, or the first AC power source terminal T1is connected with the neutral line of the AC power source, and the second AC power source terminal T2is connected with the phase line of the AC power source.

The waveform of the AC power source is periodical alternative wave, and includes two half waves: for the first half wave of AC power source, during the first half wave, the electric potential of the first AC power source terminal T1is higher than the one of the second AC power source terminal T2. For the second half wave of AC power source, during the second half wave, the electric potential of the first AC power source terminal T1is lower than the one of the second AC power source terminal T2.

When the phase line of the AC power source is connected with the first AC power source terminal T1, and the neutral line of the AC power source is connected with the second AC power source terminal T2, the first half wave of the AC power source is positive half wave of the AC power source. When the phase line of the AC power source is connected with the second AC power source terminal T2, and the neutral line of the AC power source is connected with the first AC power source terminal T1, the first half wave of the AC power source is negative half wave of the AC power source. The second half wave of the AC power source and the first half wave of the AC power source is at the two different half wave of the periodic wave of the AC power source.

The solenoid driving circuit104is a unilateral conductive circuit, during the first half wave of the AC power source, when the SCR141is conducted, the trip coil142can generate sufficient high trip current to disconnect the magnetic switch88, and achieve the ground fault protection function. During the second half wave of the AC power source, no matter whether the SCR141is conductive or not, the trip coil142cannot generate the trip current, the magnetic switch88cannot be triggered.

The self-test circuit201according to the present invention is a unilateral conductive circuit, during the second half wave of the AC power source, when the self-test triode211becomes conductive, the self-test circuit201can generate ground fault current for self fault detection in the AC power source path102. During the first half wave of the AC power source, no matter whether the self-test triode211is conductive or not, the self-test circuit201will be under non-conductive condition, so no ground fault current can be generated.

During any time of AC power source periodic wave, the measurement and control circuit202according to the present invention can make the self-test triode211conductive, and achieve the self fault detection function without selecting phase and interrupting power supply.

The circuit protection device with self fault detection function according to the present invention, the ground fault protection unit can achieve the ground fault detection and protection function for AC power source power circuit and home appliance. The self fault detection unit is provided with two delay circuits which can achieve the fault detection at early stage of power-on and periodically fault detection function. The ground fault protection circuit and self fault detection unit can operate in time sharing, and achieve self fault detection without interruption of power supply. The self fault detection unit and the ground fault protection unit are separated from high impedance. Any fault occurred on any element in the self fault detection unit may not impair the protection ability of the ground fault protection unit. The simply, economic, and high efficiency of the circuit solve the inconvenience of manual detection and eliminate safety risk.

EMBODIMENTS OF THE INVENTION

The following is a detailed description for the present invention according to the attached drawings and embodiment, and the following embodiment is not limited to the present invention.

FIG. 1is a structural schematic diagram showing a circuit protection device with self fault detection function according to an embodiment of the present invention. The circuit protection device includes a ground fault protection unit1and a self fault detection unit2.

Wherein, the ground fault protection unit1includes a ground fault detection circuit101, an AC power source path102, a manual test circuit103, and a solenoid driving circuit104. The ground fault detection circuit101, the AC power source path102and the solenoid driving circuit104form a ground fault protection circuit which can operate independently. The manual test circuit103simulates a ground fault current which is used to test the ground fault protection function.

The self fault detection unit2includes a self-test circuit201, a measurement and control circuit202and an alarming circuit203. The self fault detection unit2and the ground fault protection unit1form a closed loop control system, and the ground fault protection unit1is the object to be detected by the self fault detection unit2, to achieve the self fault detection function. The process is as follows: under the control of the measurement and control circuit202, the self-test circuit201generates a ground fault current for self fault detection to the ground fault protection unit1, the measurement and control circuit202detects the fault condition feedback signal from the ground fault protection unit1, and determines whether the ground fault protection unit1is working properly, and sends alarming signals via the alarming circuit203.

FIG. 2shows an AC power source wiring diagram, and shows a wiring way of the AC power source in the AC power source path102as illustrated inFIG. 1, wherein the phase line L of the AC power source is connected with the AC power source terminal T1, and the neutral line N of the AC power source is connected with the AC power source terminal T2.

FIG. 3shows another AC power source wiring diagram, and shows another wiring way of the AC power source in the AC power source path102as illustrated inFIG. 1, wherein the phase line L of the AC power source is connected with the AC power source terminal T2, and the neutral line N of the AC power source is connected with the AC power source terminal T1.

As shown inFIGS. 2 and 3, the AC power source is connected between the terminal T1and terminal T2of the AC power source. The waveform of the AC power source is periodical alternative wave, such as sine wave, each periodic wave includes two half waves: for the first half wave of AC power source, when the AC power source is connected between the terminal T1and T2of the AC power source, during the first half wave, the electric potential of the AC power source terminal T1is higher than the one of the AC power source terminal T2, i.e. generates a positive voltage between the terminals T1and T2of the AC power source. For the second half wave of AC power source, when the AC power source is connected between the terminals T1and T2of the AC power source, during the second half wave, the electric potential of the AC power source terminal T1is lower than the one of the AC power source terminal T2, i.e. generates a negative voltage between the terminals T1and T2of the AC power source.

As the wiring ways of AC power source in the AC power source path102, the first half wave of the above AC power source can be positive half wave or negative wave of AC power source: when the phase line of the AC power source is connected with the AC power source terminal T1, the neutral line of the AC power source is connected with the AC power source terminal T2, the first half wave of the AC power source is at the positive half wave of the AC power source (at the time, the electrical potential of the phase line is higher than one of the neutral line). When the phase line of the AC power source is connected with the AC power source terminal T2, the neutral line of the AC power source is connected with the AC power source terminal T1, the first half wave of AC power source is at the negative half wave of the AC power source (at the time, the electrical potential of the phase line is lower than one of the neutral line). At same time, the second half wave of the AC power source and the first half wave of the AC power source are at the two different half wave of the periodic wave of the AC power source, and the second half wave of AC power source can be negative or positive half wave of the AC power source.

FIG. 4shows a schematic diagram of circuit according to an embodiment of the present invention, wherein the wiring way of the AC power source is shown inFIG. 3. The ground fault detection circuit101comprises a ground fault current sensor150, a grounded neutral sensor160, a first DC power source180and a ground fault detection chip170and its peripheral circuits. The output of the ground fault current sensor150and the grounded neutral sensor160are connected with the ground fault detection chip170.

The first DC power source180comprises a resistance184, a rectifier bridge181, a resistance182and a capacitor183, the output anode V1of the first DC power source180(185inFIG. 4) is connected with the ground fault chip170(175nFIG. 4), the cathode of the first DC power source180acts as the logic ground (GND) inside the ground fault protection unit1and the self fault detection unit2.

The AC power source path102comprises AC power source terminals T1, T2, load terminals26,27, power receptacles34A/34B, conductors91and92, and a magnetic switch88. The one end of the conductor91is connected with the AC power source terminal T1, and the other end of the conductor91is connected with the moving contact98A of the magnetic switch88passing through the ground fault current sensor150and the grounded neutral sensor160. The one end of the conductor92is connected with the AC power source terminal T2, and the other end of the conductor92is connected with the moving contact99A of the magnetic switch88passing through the ground fault current sensor150and the grounded neutral sensor160. The static contacts (98B,98C,99B,99C) of the magnetic switch88are respectively connected with wiring the terminals of load terminals (26,27) and power receptacles (34A/34B). When the magnetic switch88is closed, AC power source is connected with the load terminals and power receptacles via the magnetic switch88. When the magnetic switch88is disconnected, the terminals T1, T2of the AC power source is disconnected with the load terminals and power receptacles.

The solenoid driving circuit104includes a diode143, a trip coil142, a SCR141, a resistance146, a capacitor147and a diode188in the rectifier bridge181. The AC power source terminal T1is connected with the anode of the diode143, the cathode of the diode143is connected with the anode of the SCR141via the trip coil142, the cathode of the SCR141is connected with GND, and the anode of the diode188in the rectifier bridge181is connected with GND, and the cathode of the diode188is connected with the AC power source terminal T2. The control pole of the SCR141is connected with the output177of the ground fault detection chip170via the resistance146. As the unilateral conductive function of the diode143and the diode188, the magnetic driving circuit loop is also unilateral conductive. The process is: when the output177of the ground fault detection chip170is at high level, the SCR141becomes conductive, during the first half wave of the AC power source, the diode143and the diode188become conductive, the trip coil142can trip, so that the magnetic switch88breaks off. During the second half wave of the AC power source, the diode143and the diode188become non-conductive, the trip coil142cannot trip, so that the magnetic switch88has no action.

The manual test circuit103includes a ground fault test switch35and a resistance131which are coupled in turn, one end of the manual test circuit103is connected with the AC power source terminal T1and the other end of the manual test circuit103is connected with the AC power source terminal T2.

The ground fault protection function of the ground fault protection unit1is achieved by means of the ground fault detection circuit101, the solenoid driving circuit104and the magnetic switch88. The process is as follows: when the ground fault test switch35is turned on manually, or when any ground fault such as electrical leakage, electric shock occurs on load circuit and appliance, a ground fault current will be generated on the AC power source path102. When the ground fault current on the AC power source path102exceeds the operating current to trip, the output177of the ground fault detection chip170is at a high level, and the SCR141becomes conductive via the resistance146. As described above, during the first half wave of the AC power source (at this time, the diodes143and188become conductive), the trip coil142and the magnetic switch88operate, and the magnetic switch88in AC power source path102breaks off, and thereby disconnect the AC power source terminals T1, T2and the load terminals26,27and the power receptacles34A/34B, and achieve the ground fault protection function.

The measurement and control circuit202includes a second DC power source270, a fault signal input circuit branch240, a fault signal input branch250, a diode268, a detection chip263and an auxiliary circuit (resistance261,262). The auxiliary circuit outputs VIH and VIL to the detection chip263, and the detection chip263generates internal reference voltages VH1, VL1, VH2, and VL2based on VIH and VIL. Wherein, VH1is smaller than V2(the output of the DC power source270), and VL1is smaller than or equal to VH1. VH2is smaller than V2, and VL2is smaller than or equal to VH2. VH1, VL1, VH2and VL2can also be generated directly by the detection chip263, and in this case the auxiliary circuit can be omitted. In this embodiment, VH1and VH2are equal to VIH, and VL1and VL2are equal to VIL.

The DC power source270includes a resistance271, a diode272, a capacitor273, and a stabilivolt274. Its output anode V2(275inFIG. 4) is connected with terminal V2in the self fault detection unit2, and the output cathode is connected with GND.

The fault signal input circuit branch240includes resistances241,243and a capacitor242. The end of the capacitor242is connected with an IN1pin (266inFIG. 4) of the detection chip263, and the other end of the capacitor242is connected with GND. The anode of SCR141is connected with the IN1pin of the detection chip263via the resistance241, and the resistance243is connected in parallel with the capacitor242. When the trip coil142and the diode143have no fault, the capacitor242is charged by AC power source through the diode143, the trip coil142and the resistance241, so that the VB1on the capacitor242increases from 0V to over VIH (or VH1) during a predetermined time period TR1, such as 5 seconds. When the trip coil142and/or the diode143is disconnected, the VB1will decreases to smaller than VIL (or VL1) during a predetermined time period, such as 1 second. The detection chip263determines if the trip coil142and the diode143is disconnected by detection of VB1.

The fault signal input circuit branch250includes a diode251, a resistance253and a capacitor252. One end of the capacitor252is connected with an IN2pin (267inFIG. 4) of the detection chip263, and the other end of the capacitor252is connected with GND. The DC power source V2is connected with the IN2pin of the detection chip263via the resistance253, the cathode of the diode251is connected with the anode of the SCR141and the anode of the diode251is connected with the IN2pin of the detection chip263. The capacitor252is charged via the resistance253by means of the DC power source V2, and/or the capacitor252is charged via the pin VS3of the detection chip263and a diode268, and/or the capacitor252is charged via the other pin of the detection chip263. The charge in the capacitor252is released by means of the SCR141and the diode251. When the SCR141becomes non-conductive, the voltage VB2on the capacitor252will be raised to over VIH (or VH2). When the SCR141becomes conductive, the VB2will be reduced to smaller than VIL (or VL2), until the current passing through the SCR141is smaller than minimum available current value, the SCR141becomes non-conductive. The fault condition of the ground fault detection circuit101and the solenoid driving circuit104is detected by the detection chip263by detecting VB2.

The detection chip263detects the voltage VB1of the capacitor242, and controls the charge current of the capacitor252. When the VB1is greater than VIH, or during the VB1value reducing from a value greater than VIH to a value greater than or equal to VIL, the fault signal input circuit branch250and/or the detection chip263forms a charge circuit. As described above, with the lower charge current I1to the capacitor252, the capacitor252is charged with a lower rate, so that the voltage VB2on the capacitor252is increased to a value greater than VIH from a value smaller than VIL during a predetermined time period TR21, such as 60 seconds. When VB1is smaller than the VIL, or during VB1is gradually increased to a value smaller than or equal to VIH from a value smaller than VIL, the internal charge circuit is formed by the fault signal input circuit branch250, and/or the charge circuit is formed by the pins of detection chip263. As described above, with the greater charge current I2to the capacitor252, the capacitor252is charged with a high rate, so that the voltage VB2on the capacitor252is increased to a value greater than VIH from a value smaller than VIL during a predetermined time period TR22, such as 1 second, wherein, TR22is smaller than TR21, and I2is greater than I1.

The voltage VB2on the capacitor252is detected by the detection chip263, when VB2value is smaller than VIL, or VB2value is gradually increased from a value smaller than VIL to a value smaller than or equal to VIH, the output VOUT (265inFIG. 4) of the detection chip263is at low level. When VB2value is greater than VIH, or VB2value is gradually reduced from a value greater than VIH to a value greater than or equal to VIL, the output VOUT of the detection chip263is at high level.

The self-test circuit201comprises a resistance218, a self-test triode211, a ground fault resistance215, a resistance184and a diode189in the bridge rectifier181. The base of the self-test triode211is connected with the output VOUT of the detection chip263via the resistance218. The collector of the self-test triode211is connected via the ground fault resistance215with the conductor92passing through the ground fault current sensor150and the grounded neutral sensor160. The emitter of the self-test triode211is connected with the GND. The emitter of the self-test triode211is connected with the AC power source terminal T1passing through the diode189and resistance184.

During the full cycle of AC power source, including positive half wave and negative half wave, the circuit described in patent CN101295609B generates randomly the ground fault current for self fault detection without selection of phase, i.e. during the positive half wave or negative half wave of AC power source, generating the ground fault current for self fault detection.

The present invention is optimized according to the patent CN101295609B: during any time of full cycle of AC power source, the detection chip263makes the self-test triode211conductive via the resistance263. The self-test circuit201is also provided with at least one diode189, with the unilateral conductive function, the diode189can make the self-test circuit201generate the ground fault current for self fault detection only during the second half wave of AC power source.

The circuit protection device designed according to the present invention can achieve the self fault detection function without power interruption. The method is: the ground fault detection unit1and the self fault detection unit2operate in time sharing mode, so that the solenoid driving circuit104becomes conductive during the first half wave of AC power source and becomes non-conductive during the second half wave of AC power source. The self-test circuit201becomes conductive during the second half wave of AC power source, and becomes non-conductive during the first half wave of AC power source. The detection process is as follows: the detection chip263outputs at a high level and makes the self-test triode211in the self-test circuit201become conductive, during the second half wave of AC power source (at this time, the diode189becomes conductive), the ground fault current is generated by the self-test circuit201and flows though the AC power source102, and makes SCR141become conductive. During the time period, as the solenoid driving circuit104is in cut-off state, and cannot make the trip coil142and the magnetic switch88trigger, thereby the self fault detection function can be achieved without power interruption.

The ground fault protection unit1according to the present invention is divided into two parts for fault detection. The first part performs the periodic detection for the ground fault detection circuit101and the SCR141. The second part performs the real-time detection for the diode143and the trip coil142.

The periodic detection process is as follows: when the voltage VB2on the capacitor252is increased from a value smaller than VIL to a value greater than VIH, the output VOUT of the detection chip263is at a high level (>2V), makes the self-test triode211in the self-test circuit201become conductive, and a ground fault simulated current is generated by the self-test circuit201. When no fault occurs in the ground fault detection circuit101and the SCR141and auxiliary circuit, the SCR141becomes conductive, the charge on the capacitor252are released rapidly via the diode251and the SCR141, the VB2is rapidly reduced to a value smaller than VIL. At this time, the VOUT is turned to a low level from a high level, the self-test triode211is non-conductive, the ground fault simulated current disappears, the SCR141releases the charge on the capacitor252until SCR141is non-conductive, the periodic detection process is completed. If no fault occurs in ground fault detection circuit101and the SCR141and its auxiliary circuit, a signal “System ok” is output by detection chip263. If any fault occurs at the ground fault detection101and/or the SCR141and its auxiliary circuit, the SCR141becomes non-conductive or short to ground. If the SCR141becomes non-conductive, the VB2keeps a value greater than VIH, and the periodic detection process will continue (no finish point), an alarm signal “System fault” is output by the detection chip263. When the SCR141is short to ground, the VB2will keep continuously at a value smaller than VIL, and the self fault detection unit2has no way to perform the subsequent self test, the alarm signal “System fault” is sent by detection chip263.

The periodic detection process as described above according to the present invention is performed for one time or several times at the early stage of power-on. When AC power source is connected with the AC power source terminals T1and T2, the VB1is increased gradually from 0V to a value smaller than or equal to VIH during a predetermined time period VB1, such as 5 seconds, during the time period, as described above, the capacitor252is charged with a high rate, the VB2is increased rapidly from a value smaller than VIL to a value greater than VIH, and the periodic detection process as described above is carried out for one time, and the detection process is completed. After that, the detection chip263detects continuously the VB1, if the VB1is still smaller than or equal to VIH, the process above is repeated again, until the VB1is greater than VIH, and the detection process at early stage of power-on is completed. The time taken during detection process at the early stage of power-on is determined according to the charge time TR1of the capacitor242, the interval time between two detection processes is determined according to the charge time TR22of the capacitor252.

After the detection process at the early stage of power-on, or after the periodic detection process last time, the capacitor252is charged with low rate, the VB2is increased from a value smaller than VIL to a value greater than VIH during a predetermined time period TR21, such as 60 seconds, and then the periodic detection process is carried out as described above, the charge in the capacitor252is released, the VB2is decreased, the SCR141is cut-off, and then the capacitor252is charged again, and repeated periodically. The interval time between two detection processes is determined according to the charge time TR21of the capacitor252.

The present invention is to perform the real-time detection for the trip coil142and the diode143. The process is as follows: when no fault occurs at the trip coil142and the diode143, the VB1is greater than VIH, the self fault detection unit2continues to periodically detect according to a predetermined time period. When the trip coil142and/or the diode143malfunctions due to broken circuit, as described above, the VB1is decreased to a value smaller than VIL, the self fault detection unit2starts the continuous no-ending periodic detection process same as the early stage of power-on, and the detection chip263sends alarm signal “System fault” to the alarming circuit203.

The alarming circuit203receives the alarm signal from the detection chip263, and sends the signal in form of sound or light to indicate the operation state of the circuit protection device. InFIG. 4, the alarm circuit203comprises one LED36B, if no fault occurs at the ground fault protection unit1, the LED in the alarm circuit203flashes one time or several times. If fault occurs at the ground fault protection unit1, the LED in the alarm circuit203flashes continuously or illustrated for long time, or not illustrated.

The self fault detection unit2and the ground fault protection unit1according to the present invention are separated from high impedance. Any fault occurred on any element in the self fault detection unit2may not impair the protection ability of the ground fault protection unit1. The method is as following: the fault signal input circuit branch240comprises at least one high impedance resistance, such as resistance241, and achieves the high impedance separation between the ground fault protection unit1and the fault signal input circuit branch240. The fault signal input circuit branch250comprises at least one unilateral conductive diode, such as the diode251, by means of reverse cut-off features of the diode251, and achieves the high impedance separation between the self fault detection unit2and the ground fault protection unit1.

It is to be understood that both the attached drawings and embodiments are intended to provide further explanation of the function, structure and principles of the present invention as claimed and not limited to the present invention. Also the objects of the present invention have been achieved. The above described embodiments may be modified without departing from the spirit or scope of the invention, thus, the present invention covers the scope described in the claims.