WO2022237319A1 - 一种漏电流检测电路、方法及漏电流检测器 - Google Patents

一种漏电流检测电路、方法及漏电流检测器 Download PDF

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Publication number
WO2022237319A1
WO2022237319A1 PCT/CN2022/081474 CN2022081474W WO2022237319A1 WO 2022237319 A1 WO2022237319 A1 WO 2022237319A1 CN 2022081474 W CN2022081474 W CN 2022081474W WO 2022237319 A1 WO2022237319 A1 WO 2022237319A1
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Prior art keywords
leakage current
auxiliary winding
signal
current
switch tube
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Ceased
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PCT/CN2022/081474
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English (en)
French (fr)
Chinese (zh)
Inventor
雷健华
张勇波
马辉
秦赓
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Shenzhen Poweroak Newener Co Ltd
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Shenzhen Poweroak Newener Co Ltd
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Priority to JP2022558381A priority Critical patent/JP7476341B2/ja
Priority to EP22773383.9A priority patent/EP4113144B1/en
Priority to US17/944,396 priority patent/US11668762B2/en
Publication of WO2022237319A1 publication Critical patent/WO2022237319A1/zh
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/40—Testing power supplies
    • G01R31/42—AC power supplies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the present application relates to the technical field of inverter leakage current detection, for example, to a leakage current detection circuit, method and leakage current detector.
  • the power conversion equipment (such as an inverter) needs to have residual current (leakage current) detection or monitoring protection Function.
  • Embodiments of the present application provide a leakage current detection circuit, method and leakage current detector, which improve the sensitivity of leakage current detection and reduce the cost of leakage current detection.
  • a technical solution adopted in the embodiment of the present application is to provide a leakage current detection circuit, the leakage current detection circuit includes a main winding, an auxiliary winding, a detection module and a signal output module;
  • the main winding is used to connect with the leakage current detection terminal of the device under test, the main winding is coupled with the auxiliary winding, and the auxiliary winding is respectively connected with the signal output module and the detection module;
  • the signal output module is used to output positive and negative pulse signals alternately, so that the auxiliary winding is in a preset state
  • the detection module is configured to detect the current signal of the auxiliary winding when the auxiliary winding is in the preset state, and detect the leakage current of the device under test according to the current signal.
  • the signal output module includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube and a first control unit;
  • the first end of the first switch tube and the first end of the second switch tube are used to connect to a power supply, and the second end of the first switch tube passes through the detection module and the first end of the auxiliary winding connected, the second end of the first switching tube is also connected to the first end of the fourth switching tube, the second end of the second switching tube is respectively connected to the second end of the auxiliary winding and the first
  • the first ends of the three switch tubes are connected, the second end of the third switch tube and the second end of the fourth switch tube are used for grounding, and the first control unit is connected with the first switch tube and the The control terminals of the second switch tube, the third switch tube, and the fourth switch tube are connected;
  • the first control unit is used to control the on-off states of the first switch tube, the second switch tube, the third switch tube, and the fourth switch tube, so as to output the alternating positive and negative pulses signal, wherein the on-off state of the first switching tube is the same as that of the third switching tube, the on-off state of the second switching tube is the same as that of the fourth switching tube, and the first switching tube and the The second switch tube is turned on alternately.
  • the detection module includes a sampling resistor, an operational amplifier and a second control unit;
  • the first end of the auxiliary winding is connected to the signal output module through the sampling resistor, the two input terminals of the operational amplifier are connected to both ends of the sampling resistor, and the output terminal of the operational amplifier is connected to the The second control unit is connected.
  • the detection module is further configured to obtain leakage current information according to the current signal and the duty cycle of the pulse signal, so as to detect the leakage current of the device under test;
  • the detection module is also used to judge whether the current signal is greater than a preset current, and output a leakage current alarm signal when the current signal is greater than the preset current.
  • another technical solution adopted in the embodiment of the present application is: to provide a leakage current detection method, which is applied to the leakage current detection circuit in any of the above-mentioned embodiments, and the method includes: providing the auxiliary winding inputting alternating positive and negative pulse signals, so that the auxiliary winding is in a preset state;
  • the leakage current of the device under test is detected.
  • inputting alternating positive and negative pulse signals to the auxiliary winding so that the auxiliary winding is in a preset state includes:
  • the parameter information includes the magnetic core cross-sectional area and the number of coil turns of the auxiliary winding
  • the alternating positive and negative pulse signals are input to the auxiliary winding, so that the auxiliary winding is in the preset state, wherein the duty cycle of the pulse signal is the calculated first duty cycle.
  • the method also includes:
  • the leakage current information is obtained according to the re-obtained current signal and the adjusted duty ratio, so as to detect the leakage current of the device under test.
  • the reverse adjustment of the duty ratio of the pulse signal according to the direction information includes:
  • the method also includes:
  • the method further includes:
  • the self-test of the leakage current detection circuit is performed.
  • the leakage current detector includes the leakage current detection circuit described in any of the above embodiments, and/or The leakage current is detected by using the leakage current detection method described in any one of the above embodiments.
  • the embodiment of the present application provides a leakage current detection circuit, a method and a leakage current detector, the leakage current detection circuit includes a main winding, an auxiliary winding, a detection module and a signal output module, and the leakage current detection circuit is used to detect The leakage current of the device is detected, wherein the main winding is used to connect with the leakage current detection terminal of the device under test, the main winding is coupled to the auxiliary winding, and the auxiliary winding is respectively connected to the signal output module connected to the detection module, the signal output module is used to output positive and negative pulse signals alternately, so that the auxiliary winding is in a preset state, at this time, if there is a leakage current on the main winding, it is coupled to the The leakage current of the auxiliary winding is superimposed on the positive and negative alternating pulse signals, so that the current signal detected by the detection module is larger than the current signal detected when the positive and negative alternating pulse signals are not applied, thereby improving the leakage current.
  • FIG. 1 is a schematic structural diagram of a leakage current detection circuit provided in an embodiment of the present application
  • 2a-2c are waveform diagrams of undetected leakage current in a leakage current detection circuit provided by an embodiment of the present application
  • FIG. 3 is a waveform diagram when a leakage current is detected in a leakage current detection circuit provided in an embodiment of the present application
  • FIG. 4 is a schematic diagram of a circuit structure of a leakage current detection circuit provided in an embodiment of the present application.
  • FIG. 5 is a flow chart of a leakage current detection method provided in an embodiment of the present application.
  • 6a-6d are waveform diagrams of current signals corresponding to different duty ratios in the leakage current detection circuit provided by the embodiment of the present application;
  • FIGS. 7a-7c are diagrams for adjusting the measured output value of the auxiliary winding in the leakage current detection circuit provided by the embodiment of the present application.
  • FIG. 1 is a schematic structural diagram of a leakage current detection circuit provided by an embodiment of the present application.
  • the leakage current detection circuit 1 is used to detect the leakage current of the device to be tested.
  • the leakage current detection circuit 1 includes a main winding 11, Auxiliary winding 12 , detection module 13 and signal output module 14 .
  • the main winding 11 is used to connect with the leakage current detection terminal of the device under test, the main winding 11 is coupled with the auxiliary winding 12, and the auxiliary winding 12 is respectively connected with the detection module 13 and the signal output Module 14 is connected.
  • the signal output module 14 is used to output positive and negative pulse signals alternately, so that the auxiliary winding 12 is in a preset state;
  • the detection module 13 is used to detect the current signal of the auxiliary winding 12 when the auxiliary winding 12 is in the preset state, and detect the leakage current of the device under test according to the current signal.
  • the main winding 11 is connected to a leakage current detection terminal of the device under test, for example, it may be a leakage current detection terminal of a DC-AC module.
  • the main winding 11 and the auxiliary winding 12 may be inductance components, which are divided into the common mode inductance of the main winding 11 and the auxiliary inductance of the auxiliary winding 12, and the common mode inductance Coupled with the auxiliary inductance, for example, through an iron core, to detect the leakage current of the device under test.
  • the alternating positive and negative pulse signals refer to inputting a positive pulse signal in the first sequence, inputting a negative (reverse) pulse signal in the second sequence, inputting a positive pulse signal in the third sequence, and inputting a positive pulse signal in the fourth sequence.
  • a negative pulse signal is input, which circulates sequentially, and continuously outputs the pulse signal, wherein the direction of the positive pulse signal is opposite to that of the negative pulse signal.
  • the auxiliary winding 12 has a first end and a second end, and The auxiliary winding 12 inputs the positive pulse signal, the positive pulse signal flows in from the first end, and flows out from the second end; the negative pulse signal is input to the auxiliary winding 12, so The negative pulse signal flows in from the second end and flows out from the first end, wherein the positive pulse signal and the negative pulse signal may be electrical signals.
  • the alternating positive and negative pulse signals are output through the signal output module 14 , so that the auxiliary winding 12 is in the preset state.
  • the preset state may refer to the state when the auxiliary winding 12 is in critical saturation, or refers to the magnetic amplification state of the auxiliary winding 12, or refers to when the auxiliary winding 12 is in a state of The state in which the amount of voltage change is the largest when the applied voltage is changed.
  • the signal output module 14 inputs the alternating positive and negative pulse signals to the auxiliary winding 12, and the detection module 13 detects positive and negative alternating current or voltage signals, and the effective value of the positive current is equal to the effective value of the negative current within one cycle.
  • the detection module 13 collects that the effective value of the current within one cycle is zero. That is, when the detection module 13 detects that the current signal is zero, it means that there is no leakage current fault in the device under test.
  • the auxiliary winding 12 when there is a leakage current flowing in the main winding 11, the auxiliary winding 12 will generate a corresponding induced current, and the generated induced current is superimposed with the alternating positive and negative pulse signals, and the detection module 13
  • the detected current information of the auxiliary winding 12 will shift to one side, as shown in Figure 3, when the leakage current is positive, the forward voltage or forward current collected by the detection module 13 will increase , the negative voltage or negative current decreases, and the effective value of the current or voltage detected in one cycle increases, so that the detection of leakage current can be realized, and the sensitivity of leakage current detection can be improved; and there is no need to use high-cost leakage current sensors , reducing the cost of leakage current detection.
  • FIG. 4 is a circuit structure diagram of a leakage current detection circuit provided in an embodiment of the present application.
  • the signal output module 14 includes a first switching tube Q1 , a second switching tube Q2 , a third switching tube Q3 , a fourth switching tube Q4 and a first control unit.
  • the first end of the first switching tube Q1 and the first end of the second switching tube Q2 are used to connect to a power supply, and the second end of the first switching tube Q1 passes through the detection module 13 and the auxiliary winding 12, the second end of the first switching tube Q1 is also connected to the first end of the fourth switching tube Q4, and the second end of the second switching tube Q2 is respectively connected to the auxiliary winding 12 is connected to the first end of the third switching tube Q3, the second end of the third switching tube Q3 and the second end of the fourth switching tube Q4 are used for grounding, and the first The control unit is respectively connected to the control terminals of the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4.
  • the first control unit is used to control the on-off states of the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4, so as to output the positive Negative alternating pulse signal, wherein the on-off state of the first switching tube Q1 is the same as that of the third switching tube Q3, the on-off state of the second switching tube Q2 is the same as that of the fourth switching tube Q4, And the first switching transistor Q1 and the second switching transistor Q2 are turned on alternately.
  • the first control unit is used to output a PWM signal to control the on-off of the first switching tube Q1, the second switching tube Q2, the third switching tube Q3 and the fourth switching tube Q4 state; for example, periodically and alternately output the first signal PWM1A and the second signal PWM1B, wherein the first signal PWM1A is used to control the on-off state of the first switch Q1 and the third switch tube Q3, the The second signal PWM1B is used to control the on-off state of the second switching tube Q2 and the fourth switching tube Q4, and the on-off state refers to an on-off state or an off-state. Referring to FIGS.
  • the alternating positive and negative pulse signals include a first signal PWM1A and a second signal PWM1B.
  • the first signal PWM1A corresponds to the positive voltage VCC
  • the second signal PWM1B corresponds to the negative voltage -VCC.
  • the current on the auxiliary winding 12 will be changed by periodically outputting the pulse signal, thereby generating an induced magnetic field
  • the VCC voltage is relatively small, such as 5V or 12V, so the auxiliary The induced electromotive force generated on the winding 12 is also small, and the influence on the main winding 11 can be ignored.
  • the first control unit controls the first switch tube Q1 and the third switch tube Q3 to be turned on
  • the electrical signal output by the power supply passes through the first switch tube Q1 to the The detection module 13, then flows from the detection module 13 to the auxiliary winding 12, and finally flows into the first control unit through the third switch tube Q3.
  • the first control unit controls the second switching tube Q2 and the fourth switching tube Q4 to be turned on
  • the electrical signal output by the power supply is from the power supply to the auxiliary winding 12 through the second switching tube Q2 , and then enter the first control unit from the auxiliary winding 12 through the detection module 13 .
  • alternating positive and negative pulse signals can be input to the auxiliary winding 12 .
  • the detection module 13 includes a sampling resistor R1, an operational amplifier U1 and a second control unit.
  • the first end of the auxiliary winding 12 is connected to the signal output module 14 through the sampling resistor, the two input terminals of the operational amplifier U1 are connected to the two ends of the sampling resistor, and the output terminals of the operational amplifier Connected to the second control unit.
  • the second control unit and the first control unit are the same control module, that is, the CPU in FIG. 4 .
  • the detection module 13 further includes a filter, the first end of the filter is connected to the output end of the operational amplifier U1, and the second end of the filter is connected to the second control unit. .
  • the magnetic core saturation duration of the auxiliary winding 12 is very short, so a filter is provided after the auxiliary winding 12, thereby filtering out the transient caused by the induced current. state spikes to avoid misjudgment by the second control unit.
  • the detection module 13 is further configured to obtain leakage current information according to the current signal and the duty cycle of the pulse signal, and detect the leakage current of the device under test. Specifically, since positive and negative alternating pulse signals are applied to both ends of the auxiliary winding 12, the current signal measured by the detection module 13 is not equal to the actual leakage current signal, and the actual leakage current signal is the same as The duty ratio of the applied pulse signal has a certain proportional relationship, so the leakage current value can be calculated according to the duty ratio and the measured current signal. Further, a functional relational expression between the current signal and the leakage current information is obtained, and the leakage current information is calculated according to the relational expression. The relational expression can be obtained by calculation, or can be obtained by fitting a functional relational expression or a graph through specific experimental data.
  • the detection module 13 is also used to determine whether the current signal is greater than a preset current, and output a leakage current alarm signal when the current signal is greater than the preset current.
  • the detection standard when the actual leakage current value of the device under test is greater than 30mA, it indicates that a leakage fault occurs in the device under test. , then it can be judged by judging whether the measured current signal is greater than the preset current to reduce the calculation load of the processor.
  • the preset current can be customized according to the actual needs of the user; or after the leakage current detection circuit 1 is built, an analog 30mA current signal can be measured on the main winding 11, and the current signal detected at this time can be recorded. And use this current signal as the preset current.
  • the alarm signal may be a signal light, and when the detection module 13 detects that there is a leakage current in the device under test, the signal light becomes bright to generate the alarm signal.
  • the first control unit and the second control unit may be the same CPU, or two CPUs. It only needs to meet the above circuit design requirements.
  • An embodiment of the present application provides a leakage current detection circuit
  • the leakage current detection circuit includes a main winding, an auxiliary winding, a detection module and a signal output module
  • the leakage current detection circuit is used to detect the leakage current of the device under test
  • the main winding is connected to the leakage current detection terminal of the device under test
  • the main winding is coupled to the auxiliary winding
  • the auxiliary winding is respectively connected to the signal output module and the detection module
  • the The signal output module is used to output positive and negative pulse signals alternately, so that the auxiliary winding is in a preset state.
  • the leakage current coupled to the auxiliary winding is consistent with the positive and negative Alternate pulse signals are superimposed, so that the current signal detected by the detection module is larger than the current signal detected when the positive and negative alternating pulse signals are not applied, thereby improving the sensitivity of leakage current detection and eliminating the need to use a more sensitive detection equipment, reducing the cost of testing.
  • FIG. 5 is a flow chart of a leakage current detection method provided in an embodiment of the present application. As shown in FIG. 5, the method is executed by the above leakage current detection circuit, and includes the following steps:
  • the preset state of the auxiliary winding means that the auxiliary winding is in a near-saturation state
  • the near-saturation state means that by periodically outputting positive and negative pulse signals alternately, changing the The direction of the current, so that the auxiliary winding is in a state of near saturation.
  • the pulse signal includes a duty cycle of the pulse signal.
  • the parameter information of the auxiliary winding and the variation of the magnetic induction intensity when the auxiliary winding is in a critical saturation state are acquired, wherein the parameter information includes the magnetic core cross-sectional area and the number of coil turns of the auxiliary winding, and then according to The parameter information and the variation of the magnetic induction intensity are calculated to obtain a first duty cycle of the pulse signal, and at this time, the duty cycle of the pulse signal is the calculated first duty cycle D.
  • the expression for calculating the duty cycle is:
  • Ts is the cycle time
  • Ton is the applied voltage time
  • ⁇ B is the variation of magnetic induction intensity
  • U L is the voltage applied to the auxiliary winding
  • Ton is the time of applying the voltage
  • Ae is the cross-sectional area of the magnetic core
  • Ns is the number of coil turns of the auxiliary winding
  • the f s is the switching frequency
  • the variation of the magnetic induction intensity should be selected according to 1.2-1.5 times of the maximum magnetic induction intensity B max of the magnetic core material. Since the auxiliary winding is applied with alternating positive and negative pulse signals, the auxiliary winding is in a state close to saturation, thereby improving the accuracy of leakage current detection.
  • the leakage current detection circuit can determine the demand for the variation of the magnetic induction intensity, through the relationship between the pulse duty cycle and the magnetic core material and the number of turns of the auxiliary winding coil, the required The magnetic core material and the coil turns of the auxiliary winding meet the requirements, and then the magnetic core material and the coil turns of the auxiliary winding with the best cost performance are selected to reduce circuit design costs.
  • the leakage current detection circuit can determine the demand for the variation of the magnetic induction intensity and the magnetic core material, through the relationship between the duty cycle of the pulse and the number of turns of the auxiliary winding coil, It is determined that the number of coil turns of the auxiliary winding meets the requirements, and then the number of coil turns of the auxiliary winding with the best cost performance is selected, so as to reduce the cost of circuit design.
  • the first duty ratio can also be determined according to the following method:
  • the sensitivity of leakage current detection can be improved by applying a positive and negative pulse signal whose duty cycle is the first duty cycle to the auxiliary winding alternately.
  • the current signal of the auxiliary winding is detected by the detection module, and the current signal includes the direction and magnitude of the current. Specifically, by obtaining the current signal flowing out of the auxiliary winding, the current signal is performing amplification, filtering the amplified current signal, and finally inputting it to the second control unit. Wherein, by amplifying the current signal, the sensitivity of the leakage current detection can be improved, however, the amplified current signal will produce a transient peak, at this time, by filtering the transient peak, it can be Misjudgment by the second control unit is reduced.
  • U L is the voltage on the auxiliary winding
  • the L is the inductance
  • d i is the current increment on the auxiliary winding
  • d t is the time increment on the auxiliary winding.
  • the first control unit changes the direction of the current on the auxiliary winding by controlling the signal output module to periodically output positive and negative pulse signals, so that the voltage on the auxiliary winding Also changed.
  • the signal output module inputs positive and negative alternating pulse signals to the auxiliary winding, and the detection module detects positive and negative alternating current or voltage signals, and within one cycle
  • the effective value of the positive current is equal to the effective value of the negative current, and at this time, the effective value of the current collected by the detection module within one cycle is zero.
  • the generated induced current is superimposed with alternating positive and negative pulse signals, and the current information of the auxiliary winding detected by the detection module will be sent to a side offset, when the leakage current is positive, the positive voltage or positive current collected by the detection module increases, the negative voltage or negative current decreases, and the effective current or voltage is detected within one cycle
  • the value becomes larger, so that the detection of leakage current can be realized, and the sensitivity of leakage current detection can be improved; and there is no need to use a high-cost leakage current sensor, which reduces the cost of leakage current detection.
  • the way of detecting the leakage current of the device under test may be to judge whether the current signal is greater than the preset current, when the current signal is greater than The preset current outputs a leakage current alarm signal.
  • the actual leakage current value of the device under test is greater than 30mA, it indicates that a leakage fault occurs in the device under test. , then it can be judged by judging whether the measured current signal is greater than the preset current to reduce the calculation load of the processor.
  • the preset current can be customized according to the actual needs of the user; it is also possible to measure the simulated 30mA current signal in the main winding after the leakage current detection circuit is built, record the current signal detected at this time, and The current signal is used as the preset current.
  • the method of detecting the leakage current of the device under test according to the current signal may be to obtain leakage current information according to the current signal and the duty cycle of the pulse signal, The leakage current of the device under test is detected. Specifically, since positive and negative alternating pulse signals are applied to both ends of the auxiliary winding, the current signal actually measured by the detection module is not equal to the actual leakage current signal, and the actual leakage current signal is different from the applied pulse signal.
  • the duty cycle of the signal has a certain proportional relationship, so the leakage current value can be calculated according to the duty cycle and the measured current signal. Further, the functional relational expression between the current signal and the leakage current information is obtained, and the leakage current information is calculated according to the relational expression.
  • the relational expression can be obtained by calculation, or can be obtained by fitting the functional relational expression or graph through specific experimental data.
  • the leakage current detection method further includes range extension. Since the transient current peak generated when the auxiliary winding is saturated is easily filtered out, the measurement range will be reduced, so the auxiliary winding measurement output is close to positive and negative balance by reversely adjusting the duty cycle, thereby reducing The influence of magnetic core saturation on the measurement results improves the detection accuracy and realizes the expansion of the measurement range.
  • the direction information of the current signal is obtained, and then the direction information of the pulse signal is reversely adjusted according to the direction information.
  • duty cycle and then re-obtain the current signal of the auxiliary winding, and obtain the leakage current information according to the re-acquired current signal and the adjusted duty cycle, so as to measure the leakage current of the device under test to test.
  • the reverse adjustment of the duty cycle of the pulse signal includes reducing the duty cycle of the positive pulse signal and keeping the duty cycle of the negative pulse signal unchanged when the current signal is detected to be positive. , when it is detected that the current signal is negative, reduce the duty cycle of the negative pulse signal and keep the duty cycle of the positive pulse signal unchanged.
  • the duty cycle of the positive pulse signal PWM1A
  • PWM1B negative pulse information
  • Figures 7a-7c are diagrams for adjusting the measured output value of the auxiliary winding in the leakage current detection circuit provided by the embodiment of the present application, as shown in Figures 7a-7c, when the detected current signal exceeds the preset threshold, and When the current signal is negative, keep the duty cycle of the positive pulse signal (PWM1A) unchanged, and reduce the duty cycle of the negative pulse signal (PWM1B), so that the leakage current and the positive and negative pulse signals alternate, so that the auxiliary winding measurement output is close to Positive and negative balance, thereby reducing the influence of magnetic core saturation on the measurement results, can improve the detection accuracy and realize the expansion of the measurement range.
  • PWM1A positive pulse signal
  • PWM1B negative pulse signal
  • the duty ratio of the pulse signal is reversely adjusted, so that the duty ratio sized for the second duty cycle.
  • the duty ratio of the pulse signal is reversely adjusted, so that the duty ratio sized for the second duty cycle.
  • the first preset threshold is smaller than the second preset threshold
  • the second duty ratio is larger than the third duty ratio, that is, the duty ratios of the current signal and the pulse signal Inversely proportional, when the current signal is larger, the duty cycle of the pulse signal is smaller.
  • the second preset threshold, the third preset threshold, the second duty cycle and the third duty cycle can be designed according to the actual needs of users, or according to the specific
  • the leakage current detection circuit is designed through specific experimental data or simulation results; for example, by simulating various leakage currents on the main winding and adjusting the duty cycle of the pulse signal to obtain multiple sets of experimental data, through Analyzing the experimental data and then setting corresponding values of the second preset threshold, the third preset threshold, the second duty cycle, and the third duty cycle.
  • the above embodiment only lists the second preset threshold and the third preset threshold, and the user can set the fourth preset threshold, the fifth preset threshold, etc. according to actual needs, and then adjust the corresponding duty ratio .
  • the leakage current detection method further includes performing a self-test on the leakage current detection circuit.
  • a current input source is externally connected to the leakage current detection circuit, so that the circuit has a first current, wherein the first current is at least greater than 30 mA.
  • Obtain and record the first output value on the auxiliary winding at this time disconnect the external current input source, so that the first current in the leakage current detection circuit becomes zero, obtain the second output value on the auxiliary winding output value.
  • obtain the duty cycle of the alternating positive and negative pulse signals adjust the duty cycle of one of the pulse signals so that the difference between the first output value and the second output value is within a preset range, and The adjusted duty cycle is obtained, wherein the difference between the second output value and the first output value may be between 0-0.1.
  • the present application provides a leakage current detection method, which is applied to a leakage current detection circuit.
  • the method inputs positive and negative pulse signals alternately to the auxiliary winding to make the auxiliary winding in a preset state, and then When the winding is in the preset state, detect the current signal of the auxiliary winding, and finally detect the leakage current of the device under test according to the current signal, by setting the auxiliary winding in the preset state, so that when the main When there is a leakage current on the winding, the leakage current coupled to the auxiliary winding is superimposed on the alternating positive and negative pulse signals, thereby improving the sensitivity of leakage current detection, and without using a detection device with high sensitivity, reducing the detection cost. cost.
  • An embodiment of the present application also provides a leakage current detector, including any one of the above leakage current detection circuits, and/or adopting any one of the above leakage current detection methods to detect the leakage current, wherein the The leakage current detector changes the direction of the current through the signal output module, thereby increasing the sensitivity of the leakage current detector and reducing the cost of the leakage current detector.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
PCT/CN2022/081474 2021-11-08 2022-03-17 一种漏电流检测电路、方法及漏电流检测器 Ceased WO2022237319A1 (zh)

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