Leakage protection circuit with self-checking function

Abstract

The application provides a leakage protection circuit with self-checking function, which comprises a switch module, a leakage protection module and a self-checking module. The switch module is coupled to a power supply line. The leakage protection module is coupled to the power supply line and the switch module respectively, detects a leakage signal on the power supply line and controls the switch module based on the leakage signal. The self-checking module comprises an analog leakage unit, a loop detection unit, a clock unit and an indication unit. The analog leakage unit is electrically connected to the power supply line, generates an analog leakage current signal on the power supply line to trigger the leakage protection module. The loop detection unit and the switch module work in two opposite half cycles of alternating current respectively. The clock unit provides a trigger signal for the analog leakage unit at the initial power-on time to complete power-on self-checking and then performs periodic self-checking. The indication unit indicates the result of each self-checking. When a failure of the leakage protection module is detected, the self-checking module provides an alarm indication and controls the switch module to perform forced tripping.

Description

TECHNICAL FIELD

[0001] The present application relates to the electrical field, and particularly relates to a leakage protection circuit with self-checking function. BACKGROUND

[0002] At present, more and more household or industrial electrical appliances are used in various fields. In order to use electricity safely, people install leakage protectors at the output end of the power grid or at the input end of some household electrical appliances. Once leakage occurs at the output end of the power grid, the leakage protector will cut off the switch coupled between the input end and the output end of the power grid, and the load will be powered off, thereby ensuring the safety of use.

[0003] The leakage protection products commonly used at present are all equipped with a manual TEST button. Every 4-6 weeks, a person needs to press the TEST button to ensure that the tripping device of the leakage protector can normally trip under the condition of leakage (the electrical structure is determined to be normal by detecting the mechanical structure). In fact, few people will press the TEST button regularly. In this case, once the leakage protection circuit fails, it will bring great hidden dangers to the safety of using electricity. Often, people are shocked to find that the leakage protector has been broken. SUMMARY

[0004] The present application is provided in order to overcome the problem that the leakage protection products cannot automatically detect whether the leakage protection circuit is working normally. The present application provides a leakage protection circuit with self-checking function.

[0005] In order to achieve the above-mentioned purpose, the present application provides a leakage protection circuit with self-checking function. The circuit includes a switch module, a leakage protection module and a self-checking module. The switch module is coupled to the input end and the output end of the power supply line. The leakage protection module is coupled to the power supply line and the switch module, respectively, detects the leakage signal on the power supply line and controls the switch module based on the leakage signal. The self-checking module includes an analog leakage unit, a loop detection unit, a clock unit and an indication unit. The analog leakage unit is electrically connected to the power supply line, generates an analog leakage current signal on the power supply line to trigger the leakage protection module, and then the loop detection unit works and completes self-checking of the leakage protection circuit once. The loop detection unit and the switch module work in two opposite half cycles of alternating current, respectively. The clock unit provides a trigger signal for the analog leakage unit at the initial power-on moment to complete power-on self-checking, and then periodically provides a trigger signal for the analog leakage unit to perform periodic self-checking. The indication unit indicates the result of each self-checking. When the leakage protection module failure is detected, the self-checking module provides an alarm indication, and controls the switch module to perform forced tripping.

[0006] According to the embodiment of the present application, the clock unit comprises a phase detector, a timer and a latch; the phase detector edge triggers the analog leakage unit to generate analog leakage; the leakage protection module detects the analog leakage, the latch latches the leakage signal detected by the leakage protection module and triggers with delay, and the loop detection unit resets through the thyristor conduction to complete a self-check.

[0007] According to the embodiment of the present application, the timer is enabled after the first self-check is successfully completed, periodically triggers the analog leakage unit to perform periodic self-check.

[0008] According to the embodiment of the present application, the latch latches the analog leakage signal triggered by the analog leakage unit, and triggers with delay to the leakage signal at the falling edge of the phase detector.

[0009] According to the embodiment of the present application, the analog leakage unit comprises a switch tube and a resistance element electrically connected to the live wire of the power supply line, and the switch tube is controlled by the phase detector to trigger the analog leakage unit to work.

[0010] According to the embodiment of the present application, the phase detector takes power from the live wire of the alternating current through a diode and a current limiting resistor, and triggers the analog leakage unit in the positive half cycle of the live wire.

[0011] According to the embodiment of the present application, the loop detection unit is coupled to the anode of the thyristor through a rectifier diode; after the delay trigger of the latch, the thyristor is turned on in the negative half cycle of the live wire of the alternating current, the loop detection unit is reset, which is a symbol of completing a self-check of the leakage protection circuit, and the timer starts to work to perform periodic self-check.

[0012] According to the embodiment of the present application, the leakage protection module comprises:

[0013] A current sensing transformer coupled to the power supply line;

[0014] A leakage protection chip electrically connected to the current sensing transformer;

[0015] A thyristor electrically connected to the leakage protection chip;

[0016] A switch driving element connected to the output end of the leakage protection chip and coupled to the switch module and the thyristor respectively.

[0017] According to the embodiment of the present application, the indicating unit is composed of an LED driver and an ALARM driver; the LED driver is coupled to the light-emitting diode through a current-limiting resistor; the ALARM driver is coupled to the buzzer; when the self-checking starts each time, the LED driver controls the light-emitting diode to light up, and the light-emitting diode is turned off after the self-checking is passed; the single blinking of the light-emitting diode indicates that the leakage protection module is working normally; once the leakage protection module fails, the LED driver will control the light-emitting diode to blink at a fixed frequency, and at the same time, the ALARM driver controls the buzzer to alarm, warning the user that the leakage protection module fails.

[0018] According to the embodiment of the present application, the outputs of the loop detection units are connected to the control electrodes of the thyristors and the indicating unit respectively. Once the leakage protection module fails, the loop detection units cannot be normally reset, the loop detection units output high-level signals to the control electrodes of the thyristors, the thyristors are turned on, the solenoid generates a large current, and the switch module is forcibly tripped. At the same time, the indicating unit continuously outputs an alarm signal, warning the user that the leakage protection module fails.

[0019] In summary, the leakage protection circuit with self-checking function provided by the present application is provided with an analog leakage unit, a loop detection unit, a clock unit and an indicating unit in the self-checking module. Since the loop detection unit and the switch module work in opposite half cycles, the leakage signal generated by the analog leakage unit on the power supply line does not affect the normal work of the switch module. The analog leakage signal is only used to detect whether the leakage protection chip and the current sensing transformer in the leakage protection module work normally. The loop detection unit is used to detect whether the SCR works normally. The clock unit triggers the analog leakage unit at the initial power-on moment, and the first self-checking is completed at the initial power-on moment, ensuring that the leakage protection module can work normally after power-on. Then, the clock unit starts timing and triggers the analog leakage unit periodically to generate an analog leakage signal to perform self-checking on the leakage protection module. The indicating unit indicates the result of each self-checking. When any element in the leakage protection module fails, the loop detection unit cannot be normally reset, that is, the self-checking of all elements in the leakage protection module is realized. When the leakage protection module fails is detected, the self-checking module provides an alarm indication, and controls the switch module to perform forced tripping.

[0020] In order to make the above and other objects, features and advantages of the present application more apparent, a preferred embodiment will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The circuit principle diagram of the leakage protection circuit with self-checking function provided by the embodiment of the present application is shown.

[0022] Figure 2The diagram shown is a logic block diagram of a leakage current protection circuit with self-test function provided in an embodiment of the present invention. Detailed Implementation

[0023] Example

[0024] like Figure 1 As shown, the leakage current protection circuit with self-test function provided in this embodiment includes a switch module 10, a leakage current protection module 20, and a self-test module 30. The switch module 10 is coupled to the input terminal INPUT and the output terminal OUTPUT of the power supply line. The leakage current protection module 20 is coupled to both the power supply line and the switch module 10, detecting leakage current signals on the power supply line and controlling the switch module 10 based on these signals. The self-test module 30 includes a simulated leakage current unit 31, a loop detection unit 32, a clock unit 33, and an indicator unit 34. The simulated leakage current unit 31 is electrically connected to the power supply line, generating a simulated leakage current signal on the power supply line to trigger the leakage current protection module 20. Subsequently, the loop detection unit 32 operates and completes a self-test of the leakage current protection circuit. The loop detection unit 32 and the switch module 10 operate in two opposite half-cycles of the AC power supply. The clock unit 33 provides a trigger signal to the simulated leakage current unit 31 at the initial power-on moment to complete the power-on self-test, and then periodically provides trigger signals to the simulated leakage current unit 31 to perform periodic self-tests. The indicator unit 34 indicates the result of each self-test. When the leakage current protection module 20 malfunctions, the self-test module 30 can automatically trip and control the indicator unit 34 to enter the alarm mode.

[0025] like Figure 1 As shown, the switch module 10 includes a switch SW1 connecting the input terminal INPUT and the output terminal OUTPUT for controlling the on / off state of the power connection. The leakage current protection module 20 includes a leakage current sensing transformer ZCT1 coupled to the power supply line, a leakage current protection chip IC1 electrically connected to the leakage current sensing transformer (specifically, IC1 is composed of pins 1, 2, 3, 14, 15, and 16 of the chip LT6971V), a silicon controlled rectifier (SCR), and a switch driving component. In this embodiment, the switch driving component is a solenoid SOL connected to the live wire. However, the present invention does not impose any limitations on this.

[0026] The power supply line passes through the leakage current induction transformer ZCT1. When the fire line (L) and zero line (N) current is balanced, no current imbalance will be generated on the leakage current induction transformer ZCT1. When there is a current imbalance on the power supply line passing through the leakage current induction transformer ZCT1, that is, there is a leakage signal, the leakage current induction transformer ZCT1 will generate a corresponding voltage signal. The rectifier bridge BR is coupled to the power supply line and the leakage protection chip IC1 respectively, for taking power on the power supply line to supply power to the leakage protection chip IC1. The leakage protection chip IC1 is coupled to the leakage current induction transformer ZCT1, for detecting whether the leakage current induction transformer ZCT1 generates a corresponding voltage change, and then driving the silicon controlled rectifier SCR to be turned on. When the silicon controlled rectifier SCR is turned on, a larger current change will be generated on the coil of the switch driving component (for example, the solenoid SOL), thereby disconnecting the switch SW1, and realizing leakage protection.

[0027] The leakage protection circuit with self-checking function provided in the embodiment adds a self-checking module 30 on the basis of the switch module 10 and the leakage protection module 20. The self-checking module 30 does not affect the normal work of the leakage protection module 20 and the switch module 10. The self-checking module 30 performs self-checking on the leakage protection module 20 at initial power-on, and then performs periodic self-checking on the leakage protection module 20, to ensure the safety of each component in the leakage protection module 20 in initial use and subsequent use. The structure of the self-checking module in the leakage protection circuit provided in the embodiment will be described in detail below in combination with Figure 1 、 Figure 2 .

[0028] In the embodiment, the self-checking module 30 includes an analog leakage unit 31, a loop detection unit 32, a clock unit 33, and an indication unit 34. The clock unit 33 takes power from the fire line through the diode D2 and the current limiting resistor R12. The clock unit 33 includes a phase detector 331, a timer 332, and a latch 333. The Phase pin at the input end of the clock unit 33 is a half-wave signal with a period of the power grid frequency. The clock unit 33 triggers the analog leakage unit 31 and the indication unit 34 through the phase detector 331, the analog leakage unit 31 starts to work, and simulates leakage. The leakage protection module 20 detects the simulated leakage current signal, the self-checking module 30 latches the leakage signal and closes the analog leakage unit 31, and the loop detection unit 32 starts to work. Then the self-checking module 30 starts the latch 333, and outputs a high level at the SCR pin in the negative half cycle of the fire line, the SCR is turned on, and the loop detection unit 32 is reset. The loop detection unit 32 detects the reset state, opens the timer 332 to time, and performs periodic self-checking. The indication unit 34 indicates the result of each self-checking.

[0029] Specifically, the analog leakage unit 31 includes a transistor Ql, the collector of which is connected to the live wire through a diode Dl and a resistor R4, and the base of which is connected to the analog leakage trigger 311 through a resistor R5. Here, only the live wire is taken as an example, but the application is not limited to the use of the live wire. The loop detection unit 32 is coupled to the anode of the SCR through a rectifier diode D4, and when the SCR is turned on, the SCRT pin level of the loop detection unit 32 will be clamped at 1.2V by the rectifier diode D4 and the SCR.

[0030] The following will take the working principle of the self-checking module 30 as an example, in which the switch module 10 works in the positive half cycle of the live wire of the alternating current, and the loop detection unit 32 works in the negative half cycle of the live wire. However, the application is not limited to this. In other embodiments, the switch module can be arranged to work in the negative half cycle of the live wire of the alternating current, and the loop detection unit 32 can work in the positive half cycle of the alternating current.

[0031] At the initial moment of power-up, when the phase detector 331 detects that the Phase pin level reaches the internal operational amplifier reference level V+, (the internal bandgap reference REF = 1.25V), the clock unit 33 triggers the analog leakage unit 31 and the indication unit 34 through the rising edge of the phase detector 331, at this time, the analog leakage unit 31 creates an analog leakage in the positive half cycle of the live wire of the alternating current. At the same time, the latch 333 starts to work and enters the latching state, which will latch the next SCR control electrode output. In the same live wire positive half cycle, the leakage protection module 20 detects the analog leakage current signal, the self-checking module 30 closes the analog leakage unit 31, and at the same time, the loop detection unit 32 starts to work, and the SCRT pin establishes the reference REF2 for loop detection (here, REF2 = 3.5V). In the same live wire positive half cycle, when the phase detector 331 detects that the Phase pin level is lower than the internal operational amplifier reference level V+ (1.25V, which is very close to the zero-crossing point of the live wire), the clock unit 33 triggers the latch 333 through the falling edge of the phase detector 331, and the latch 333 exits the latching state and enters the timing state, with a timing time of 3ms. That is, in the negative half cycle of the same live wire cycle, the SCR control electrode output is high, the SCR is turned on, the SCRT pin of the loop detection unit 32 detects the low level 1.2V, and the loop detection unit 32 is reset (lower than 2.5V to reset), which represents that the leakage protection module 20 works normally. At the same time of the reset of the loop detection unit 32, the SCR control electrode high level will be closed to avoid the SCR on state lasting to the next live wire positive half cycle. After the reset of the loop detection unit 32, the timer 332 will be enabled to perform periodic self-checking.

[0032] Because the loop detection unit 32 and the switch module 10 work in opposite half cycles, that is, the leakage signal made by the analog leakage detection unit 31 on the power supply line does not affect the normal work of the switch module 10, the analog leakage signal is used to detect whether the leakage protection chip IC1 and the current induction transformer ZCT1 work normally. The loop detection unit 32 is only used to detect whether the SCR works normally, and the SCR is turned on in the negative half cycle of the live wire to avoid the work of the switch module 10. However, the present application does not make any limitation on this.

[0033] In the embodiment, the clock unit 33 takes power from the live wire of the power grid, and the frequency cycle of the power grid determines the frequency of the periodic self-check, that is, the timing time of the timer 332. Assuming that the power supply line is the national standard power frequency of 50 Hz, that is, the cycle is 20 ms, so the self-check cycle is T=2 15 ×20 ms, about 11 minutes. However, the present application does not make any limitation on this.

[0034] In the embodiment, the indication unit 34 is composed of an LED driver 341 and an ALARM driver 342. The LED driver 341 is coupled to the light-emitting diode LED1 through the current-limiting resistor R6. The ALARM driver 342 is coupled to the buzzer ALARM1. When the self-check starts each time, the LED driver 341 controls the light-emitting diode LED1 to light up, and the light-emitting diode LED1 is extinguished after the self-check passes. The single blinking of the light-emitting diode LED1 indicates that the leakage protection module 20 works normally. Once the leakage protection module 20 fails, such as the current induction transformer ZCT1, the leakage protection chip IC1 or the silicon controlled rectifier SCR fails, the LED driver 341 will control the light-emitting diode LED1 to blink at a frequency of 2 Hz, and at the same time, the ALARM driver 342 controls the buzzer to alarm, warning the user that the leakage protection module 20 fails.

[0035] In the embodiment, the output of the loop detection unit 32 is connected to the control electrode of the silicon controlled rectifier SCR and the indication unit 34 through an OR gate. Once the leakage protection module 20 fails, such as the current induction transformer ZCT1, the leakage protection chip IC1 or the silicon controlled rectifier SCR fails, although the triode Q1 is turned on and there is a leakage current on the power supply line, the silicon controlled rectifier SCR will not be turned on, at this time, the loop detection unit 32 cannot be normally reset, the loop detection unit 32 outputs a high-level signal to the control electrode of the silicon controlled rectifier SCR, turns on the silicon controlled rectifier SCR, controls the SOL to generate a large current, forcibly trips the switch module 10. At the same time, the indication unit 34 will continuously output an alarm signal, warning the user that the leakage protection module 20 fails, and the type of failure needs to be analyzed in time to ensure the safety of power use.

[0036] In summary, the leakage protection circuit with self-checking function provided by the present application sets an analog leakage unit, a loop detection unit, a clock unit and an indication unit in the self-checking module. Since the loop detection unit and the switch module work in opposite half cycles, the leakage signal generated by the analog leakage unit on the power line does not affect the normal work of the switch module, and the analog leakage signal is used to detect whether the leakage protection chip and the current induction transformer work normally. The loop detection unit is only used to detect whether the thyristor works normally, and the thyristor is turned on in the negative half cycle of the live wire to avoid the work of the switch module. The clock unit triggers the analog leakage unit at the initial power-on time, and the first self-checking is completed at the initial power-on time to ensure that the leakage protection module can work normally after power-on. Then the timer starts timing, and the analog leakage unit is triggered periodically to generate an analog leakage signal to perform self-checking on the leakage protection module. The indication unit indicates the result of each self-checking. When any element in the leakage protection module fails, the loop detection unit cannot be normally reset, that is, the self-detection of all elements in the leakage protection module is realized. When the leakage protection module fails is detected, the self-checking module provides an alarm indication, and controls the switch module to perform forced tripping.

[0037] Although the present application has been disclosed by the preferred embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make some changes and modifications without departing from the spirit and scope of the present application, and therefore the protection scope of the present application shall be subject to the scope required by the claims.

Claims

1. An electric leakage protection circuit with self-checking function, characterized in that, The application relates to a leakage protection circuit, which comprises the following parts: a switch module coupled to the input end and the output end of a power supply line; a leakage protection module coupled to the power supply line and the switch module respectively, which detects a leakage signal on the power supply line and controls the switch module based on the leakage signal; a self-checking module, which comprises an analog leakage unit, a loop detection unit, a clock unit and an indicating unit, the analog leakage unit is electrically connected to the live wire of the power supply line, an analog leakage current signal is generated on the power supply line to trigger the leakage protection module, then the loop detection unit works and completes self-checking of the leakage protection circuit once; the loop detection unit and the switch module work in two opposite half cycles of alternating current respectively, the clock unit provides a trigger signal for the analog leakage unit at the initial power-on moment to complete power-on self-checking, and then periodically provides a trigger signal for the analog leakage unit to perform periodic self-checking; the indicating unit indicates the result of each self-checking; when the leakage protection module is detected to be faulty, the self-checking module provides an alarm indication and controls the switch module to execute forced tripping; the clock unit comprises a phase detector, a timer and a latch; the clock unit input end Phase bit is a half-wave signal with a power grid frequency as a period, the clock unit triggers the analog leakage unit through the phase detector edge to generate the analog leakage; after the leakage protection module detects the analog leakage, the self-checking module closes the analog leakage unit, the latch latches the leakage signal detected by the leakage protection module, and the loop detection unit establishes a reference REF2 to prepare for loop detection; when the phase detector detects that the Phase bit approaches the live wire zero-crossing point, the latch is triggered, the latch exits the latching state, enters the timing state to make the thyristor conduct, and the loop detection unit is reset through the thyristor conduction to complete the self-checking once.

2. The ground fault circuit interrupter with self-test function of claim 1, wherein, the timer is enabled after the first self-checking is successfully completed, periodically triggers the analog leakage unit, and performs periodic self-checking.

3. The ground fault circuit interrupter with self-test function of claim 1, wherein, the latch latches the analog leakage signal triggered by the analog leakage unit, and delays the leakage signal at the falling edge of the phase detector.

4. The ground fault circuit interrupter with self-test function of claim 1, wherein, the analog leakage unit comprises a switch tube and a resistance element electrically connected to the live wire of the power supply line, and the phase detector triggers the analog leakage unit to work to control the on-off of the switch tube.

5. The ground fault circuit interrupter with self-test function of claim 4, wherein, the phase detector takes power from the live wire of the alternating current through a diode and a current-limiting resistor, and triggers the analog leakage unit in the positive half cycle of the live wire.

6. The ground fault circuit interrupter with self-test function according to claim 1 or 3, characterized in that, the loop detection unit is coupled to the anode of the thyristor through a rectifier diode; after the delay trigger of the latch, the thyristor is turned on in the negative half cycle of the live wire of the alternating current, the loop detection unit is reset, and the self-checking of the leakage protection circuit is completed, and the timer starts to work to perform periodic self-checking.

7. The ground fault circuit interrupter with self-test function of claim 1, wherein, the leakage protection module comprises: a current induction transformer coupled to the power supply line; a leakage protection chip electrically connected to the current induction transformer; a thyristor electrically connected to the leakage protection chip; a switch driving element connected to the output end of the leakage protection chip and coupled to the switch module and the thyristor respectively.

8. The ground fault circuit interrupter with self-test function of claim 1, wherein, the indicating unit is composed of an LED driver and an ALARM driver. The LED driver is coupled to the LED through a current-limiting resistor; the ALARM driver is coupled to the buzzer; when each self-check begins, the LED driver controls the LED to light up, and the LED is turned off after the self-check is passed; the single blinking of the LED indicates that the leakage protection module is working properly; once the leakage protection module fails, the LED driver will control the LED to blink at a fixed frequency, and the ALARM driver controls the buzzer to alarm, warning the user that the leakage protection module has failed.

9. The ground fault circuit interrupter with self-test function of claim 1, wherein, The outputs of the loop detection units are respectively connected to the control electrodes of the thyristors and the indication unit; once the leakage protection module fails, the loop detection units cannot be normally reset, the loop detection units output high-level signals to the control electrodes of the thyristors, the thyristors are turned on, the solenoid generates a large current, and the switch module is forced to trip; at the same time, the indication unit continuously outputs an alarm signal, warning the user that the leakage protection module has failed.

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