Current transformer sampling electricity-taking self-switching circuit capable of stably taking electricity

Abstract

The invention relates to a current transformer sampling electricity-taking self-switching circuit capable of taking electricity stably. The current transformer sampling electricity-taking self-switching circuit comprises a current transformer serving as an input end and a rectifier bridge coupled with the current transformer. The fault current sampling circuit is coupled with a power supply circuit of a direct-current power supply of a voltage-regulator tube and is coupled with an MOS (Metal Oxide Semiconductor) tube of the fault current sampling circuit, and when the voltage of the direct-current power supply is greater than the voltage of the voltage-regulator tube, a high level is output to enable the MOS tube to be switched on, so that the fault current sampling circuit is switched on for sampling; the mutual inductor electricity taking circuit is provided with a capacitor, the mutual inductor electricity taking circuit is coupled with the MOS tube, under the condition that the voltage of the direct-current power supply is lower than the voltage of the voltage-regulator tube, the control unit changes the conducting state of the triode according to the voltage of the capacitor, then the capacitor is switched between charging and discharging, and high level is output to the MOS tube; the problem that the mutual inductance sampling precision is reduced due to the fact that the capacitor is continuously switched between the charging state and the discharging state is avoided, electricity taking abnormity of the capacitor is prevented, and the capacitor can output enough voltage.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic circuits, and in particular relates to a current transformer sampling power-taking self-switching circuit capable of stably taking power. Background Art

[0002] In the existing circuit breaker design, the current transformer plays an important role in the operation of the entire circuit breaker. Its main function is to monitor the corresponding current. When it detects that the normal value of the current is deviated, the current transformer will take corresponding measures, such as disconnecting the circuit breaker or transmitting the fault current to the server.

[0003] The applicant applied for patent number "CN202110291196.4" in 2021. The patent name is "A self-switching circuit for current transformer sampling and power supply". The main problems to be solved are divided into the following two: how to realize the two-way switching of the self-power supply circuit and the external power supply circuit and how to achieve the technical effect of reading the secondary current signal during the two-way switching process. In order to solve the above two problems, the patent first uses a rectifier bridge to rectify the sinusoidal current for reading and calculating the current signal. When a DC power supply is supplied, the OR gate and the BOOST boost chip are used to cooperate with each other for driving, and the corresponding high level is output to make the MOS tube turn on, thereby controlling the flow direction of the AC full-bridge rectifier wave, and realizing the secondary current signal reading when there is external power. When there is no DC power supply, the OR gate and the BOOST boost chip are used to cooperate with each other for driving, and the corresponding low level is output to cut off the MOS tube, thereby controlling the current flow to the switching circuit to allow the capacitor to draw power from the mutual inductor, and then flow into the sampling module after drawing power, realizing the secondary current signal reading when there is no external power. When the capacitor voltage reaches the feedback voltage of the boost chip, the MOS tube is turned on. At this time, the fault current acquisition circuit flows in the same direction as when there is a DC power supply, and the AC full-bridge rectifier wave flows into the sampling resistor in the same way. When the capacitor voltage is lower than the feedback voltage of the boost chip, the capacitor draws power from the transformer again, resulting in a continuous switching between the power-drawing and discharging states.

[0004] However, a technical problem was discovered in the later technical practice of the patent, that is, in the process of sampling the secondary current signal, the capacitor will switch back and forth between the power supply and discharge state due to the decrease in voltage after discharge, resulting in a decrease in the accuracy of the mutual inductance sampling, and it is also easy to cause abnormal power supply of the capacitor, and then the capacitor cannot output enough voltage. Therefore, designing a current transformer sampling power supply self-switching circuit that can maintain normal capacitor power supply after switching to the transformer power supply, and accurately sample the secondary current signal when the transformer power supply is taken has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, a DC power supply; A current transformer as the input end of the circuit, and a rectifier bridge coupled to the current transformer; A fault current sampling circuit for collecting secondary current signals, the input end of which is coupled to the rectifier bridge; The fault current sampling circuit includes a chargeable and dischargeable energy storage capacitor; a sampling module for sampling a secondary current signal and a MOS tube that is forward-conducted at a high level; the fault current sampling circuit can be specifically divided into two power-taking circuits and a DC circuit that can be switched on and off with each other, the MOS tube in the DC circuit is in a forward-conducting state, the AC full-bridge rectified wave passing through the rectifier bridge can directly flow into the sampling module through the turned-on MOS tube, and finally flow back to the rectifier bridge to form a loop, the MOS tube in the power-taking circuit is in a forward-cutoff state, the AC full-bridge rectified wave passing through the rectifier bridge passes through the energy storage capacitor and charges the energy storage capacitor, then flows into the sampling module, and finally flows back to the rectifier bridge to form a loop; A voltage boost switching circuit for controlling the switching between the DC circuit and the power taking circuit, wherein the input end of the voltage boost switching circuit is coupled to the DC power supply and the energy storage capacitor, and the output end of the voltage boost switching circuit is coupled to the MOS tube; the voltage boost switching circuit is provided with a driving voltage, and when the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the input voltage of the voltage boost switching circuit is made greater than the driving voltage, and after data collection and data conversion, the voltage boost switching circuit outputs a high level to the MOS tube, and the MOS tube is forward-conducted, and the fault current sampling circuit is controlled to switch to the DC circuit; The voltage boost switching circuit includes a BOOST boost chip, a transistor, and an OR gate circuit; the input end of the BOOST boost chip is coupled to a DC power supply and an energy storage capacitor respectively, the output end of the BOOST boost chip is coupled to the transistor, the transistor is coupled to the input end of the OR gate circuit, and the output end of the OR gate circuit is coupled to the MOS tube; when the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the DC power supply inputs electric energy to the BOOST boost chip, and the BOOST boost chip outputs a high level, which is transmitted to the OR gate circuit through the transistor, and the OR gate circuit outputs a high level to the MOS tube, driving the MOS tube to conduct, at this time, the secondary sinusoidal wave current of the current transformer is first rectified into an AC full-bridge rectified wave through a rectifier bridge, and then passes through the turned-on MOS tube and a sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows through the rectifier bridge to the current transformer, completing the DC loop of the fault current sampling circuit.

[0006] When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the OR gate circuit outputs a low level to the MOS tube, so that the MOS tube is cut off, and the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave by the rectifier bridge. The AC full-bridge rectified wave flows to the energy storage capacitor for charging, and then flows back to the sampling module and the rectifier bridge to the current transformer. The control unit outputs a low level and switches the fault sampling circuit to a power-taking circuit. When the voltage of the energy storage capacitor after charging is greater than the feedback voltage of the BOOST boost chip, the control unit outputs a high level to the triode to turn it on, the capacitor performs a discharge operation, the BOOST boost chip outputs a high level to the OR gate circuit, and the OR gate circuit outputs a high level to drive the MOS tube to turn on. At this time, the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave through the rectifier bridge, and then passes through the turned-on MOS tube and the sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows back to the rectifier bridge to the current transformer, switching the fault current sampling circuit to a DC circuit; When the capacitor is continuously discharged and the capacitor voltage is less than the feedback voltage of the BOOST chip, the control unit outputs a low level to the transistor, the transistor is turned off to disconnect the BOOST chip from the OR gate circuit, the MOS tube loses the input high level and is forward cut off, the capacitor draws power from the current transformer again and performs charging operation, thereby repeatedly switching between the charging state and the discharging state.

[0007] The sampling module includes a sampling resistor, a signal conditioning unit and a sampling unit. When the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, one end of the DC power supply outputs a voltage and is grounded after passing through a voltage-dividing resistor, and the other end outputs a voltage to the input end of the BOOST boost chip. At this time, the voltage at the input end of the BOOST boost chip is greater than the feedback voltage of the BOOST boost chip, and the BOOST boost chip outputs a high level, which is transmitted through a triode to the input end of an OR gate circuit. The OR gate circuit outputs a high level to the gate of the MOS tube according to logic, and the MOS tube is forward-conducted. At this time, the secondary sinusoidal current of the input current transformer is rectified by a rectifier bridge, and directly passes through the source and drain of the MOS tube in the on state to flow to the sampling resistor. The voltage signal at both ends of the sampling resistor enters the signal conditioning unit, and then enters the sampling unit, and finally flows back to the rectifier bridge and the current transformer to form a loop.

[0008] When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the working state of the OR gate circuit is controlled by the control unit and the boost chip. When the voltage of the energy storage capacitor is lower than the driving voltage, after data collection and data conversion, the control unit outputs a low level to the transistor, and the transistor works in a non-conducting state. The voltage boost switching circuit outputs a low level to the MOS tube, and the MOS tube is forward cutoff, controlling the fault current sampling circuit to switch to a power-taking circuit; at this time, the energy storage capacitor will draw power from the current transformer and gradually increase the capacitor voltage; when the voltage of the energy storage capacitor is greater than the driving voltage of the voltage boost switching circuit, the energy storage capacitor will discharge the voltage boost switching circuit. At this time, the transformer power-taking circuit will The voltage boost switching circuit is subjected to data acquisition and data conversion, the control unit outputs a high level, the transistor works in the on state, the high level output by the BOOST boost chip is transmitted to the OR gate circuit via the transistor, and the OR gate circuit outputs a high level to the MOS tube, thereby driving the MOS tube of the fault current sampling circuit to be forward-conducted, so that the fault current sampling circuit is switched and maintained in the DC circuit; when the voltage of the energy storage capacitor after discharge gradually decreases and is less than the driving voltage, and the control unit outputs a low level to the transistor, the fault current sampling circuit is switched to the power-taking circuit, and the energy storage capacitor takes power from the mutual inductor again, so that in the absence of DC power supply, the energy storage capacitor remains in one of the self-powering state and the discharge state and can switch back and forth.

[0009] After adopting the above technical solution, the main problem that this patent needs to solve is how to achieve that after the external power supply circuit is switched to the self-power circuit, the capacitor will not frequently switch between the charging and discharging states and affect the technical effect of collecting the secondary current signal. In order to solve the above problems, the present invention first uses a rectifier bridge to rectify the sinusoidal current for reading and calculating the current signal. When the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the OR gate and the BOOST boost chip are used to cooperate with each other for driving, and the corresponding high level is output to make the MOS tube conduct, thereby controlling the flow direction of the AC full-bridge rectifier wave, and realizing the secondary current signal reading when there is external power. When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the OR gate, the BOOST boost chip and the control unit are used to cooperate with each other to drive the triode to be non-conductive, and the corresponding low level is output to make the MOS tube cut off, thereby controlling the current flow to the switching circuit to allow the capacitor to draw power from the mutual inductor, and then flow into the sampling module after drawing power, realizing the secondary current signal reading when there is no external power. When the capacitor voltage reaches the feedback voltage of the boost chip, the triode is turned on to output a high level to the MOS tube for conduction. At this time, the flow direction of the fault current acquisition circuit is the same as when there is power from the DC power supply, and the AC full-bridge rectifier wave flows into the sampling resistor in the same way. When the capacitor voltage changes and switches between the power supply and discharge states, the control unit needs to change the level of the output to the transistor. The capacitor will not directly switch between the self-power supply state and the discharge state, making the charging and discharging of the capacitor more stable, avoiding continuous switching of the capacitor between the charging and discharging states, which leads to a decrease in the accuracy of mutual inductance sampling, and at the same time preventing the capacitor from having power supply abnormalities, so that the capacitor can output sufficient voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Shown is the schematic diagram of the patented circuit design. DETAILED DESCRIPTION

[0011] DC power supply V1, signal conditioning unit M2, sampling resistor R3, sampling unit M1, MOS tube Q2, BOOST boost chip N2, OR gate circuit N1, transistor Q1, voltage regulator Z1, rectifier bridge D1, energy storage capacitor C1.

[0012] like Figure 1 As shown, in order to solve the above technical problems, a DC power supply; A current transformer as the input end of the circuit, and a rectifier bridge D1 coupled to the current transformer; A fault current sampling circuit for collecting secondary current signals, the input end of which is coupled to the rectifier bridge D1; The fault current sampling circuit includes a chargeable and dischargeable energy storage capacitor C1; a sampling module for sampling a secondary current signal and a MOS tube Q2 that is forward-conducted at a high level; the fault current sampling circuit can be specifically divided into two power-taking circuits and a DC circuit that can be switched on and off with each other, the MOS tube Q2 in the DC circuit is in a forward-conducting state, the AC full-bridge rectified wave passing through the rectifier bridge can directly flow into the sampling module through the turned-on MOS tube, and finally flow back to the rectifier bridge D1 to form a loop, the MOS tube Q2 in the power-taking circuit is in a forward-cutoff state, the AC full-bridge rectified wave passing through the rectifier bridge D1 passes through the energy storage capacitor C1 and charges the energy storage capacitor C1, then flows into the sampling module, and finally flows back to the rectifier bridge D2 to form a loop; A voltage boost switching circuit for controlling the switching between the DC circuit and the power taking circuit, wherein the input end of the voltage boost switching circuit is coupled to the DC power supply V1 and the energy storage capacitor C1, and the output end of the voltage boost switching circuit is coupled to the MOS tube Q2; the voltage boost switching circuit is provided with a driving voltage, and when the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the input voltage of the voltage boost switching circuit is made greater than the driving voltage, and after data collection and data conversion, the voltage boost switching circuit outputs a high level to the MOS tube Q2, and the MOS tube Q2 is forward-conducted, and the fault current sampling circuit is controlled to switch to the DC circuit; The voltage boost switching circuit includes a BOOST boost chip N2, a transistor Q1, and an OR gate circuit N1; the input end of the BOOST boost chip N2 is coupled to a DC power supply V1 and an energy storage capacitor C1 respectively, the output end of the BOOST boost chip N2 is coupled to the transistor Q1, the transistor Q1 is coupled to the input end of the OR gate circuit N1, and the output end of the OR gate circuit N1 is coupled to the MOS tube Q2; when the voltage of the DC power supply V1 is greater than the voltage of the voltage regulator tube Z1, the DC power supply V1 inputs electrical energy to the BOOST. The OST boost chip N2 is used, and the BOOST boost chip N2 outputs a high level, which is transmitted through the transistor Q1 to the OR gate circuit N1. The OR gate circuit N1 outputs a high level to the MOS tube Q2, driving the MOS tube Q2 to turn on. At this time, the secondary sinusoidal current of the current transformer is first rectified into an AC full-bridge rectified wave through the rectifier bridge D1, and then passes through the turned-on MOS tube Q2 and the sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows through the rectifier bridge D1 to the current transformer, completing the DC circuit of the fault current sampling circuit.

[0013] When there is no DC power supply V1 or its voltage is lower than the voltage of the voltage regulator tube Z1, the OR gate circuit N1 outputs a low level to the MOS tube Q2, so that the MOS tube Q2 is turned off, and the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave by the rectifier bridge D1, and the AC full-bridge rectified wave flows to the energy storage capacitor C1 for charging, and then flows back to the sampling module and the rectifier bridge D1 to the current transformer, and the control unit outputs a low level to switch the fault sampling circuit to the power supply circuit; When the voltage of the energy storage capacitor C1 is greater than the feedback voltage of the BOOST boost chip N2 after being charged, the control unit outputs a high level to the transistor Q1 to turn it on, and the capacitor performs a discharge operation. The BOOST boost chip N2 outputs a high level to the OR gate circuit N1, and the OR gate circuit N1 outputs a high level to drive the MOS tube Q2 to turn on. At this time, the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave through the rectifier bridge D1, and then passes through the turned-on MOS tube Q2 and the sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows back to the rectifier bridge to the current transformer, switching the fault current sampling circuit to a DC circuit; When the capacitor is continuously discharged and the capacitor voltage is less than the feedback voltage of the BOOST boost chip N2, the control unit outputs a low level to the transistor Q1. The transistor Q1 is not turned on to disconnect the BOOST boost chip N2 from the OR gate circuit N1. The MOS tube Q2 loses the input high level and is forward cut off. The capacitor draws power from the current transformer again and performs a charging operation, thereby repeatedly switching between the charging state and the discharging state.

[0014] The sampling module includes a sampling resistor R3, a signal conditioning unit M2 and a sampling unit M1. When the voltage of the DC power supply V1 is greater than the voltage of the voltage regulator tube Z1, one end of the DC power supply V1 outputs a voltage and is grounded after passing through a voltage divider resistor, and the other end outputs a voltage to the input end of the BOOST boost chip N1. At this time, the voltage at the input end of the BOOST boost chip N1 is greater than the feedback voltage of the BOOST boost chip N1, and the BOOST boost chip N1 outputs a high level, which is transmitted through the triode Q1 to the input end of the OR gate circuit N1. The OR gate circuit N1 outputs a high level to the gate of the MOS tube Q2 according to the logic, and the MOS tube Q2 is forward-conducted. At this time, the secondary sinusoidal current of the input current transformer is rectified by the rectifier bridge D1, and directly passes through the source and drain of the MOS tube Q2 in the on state to flow to the sampling resistor R3. The voltage signal at both ends of the sampling resistor R3 enters the signal conditioning unit M2, and then enters the sampling unit M1, and finally flows back to the rectifier bridge D1 and the current transformer to form a loop.

[0015] When there is no DC power supply V1 or its voltage is lower than the voltage of the voltage regulator tube, the working state of the OR gate circuit N1 is controlled by the control unit and the boost chip N2. When the voltage of the energy storage capacitor C1 is lower than the driving voltage, after data collection and data conversion, the control unit outputs a low level to the transistor Q1, and the transistor Q1 works in a non-conducting state. The voltage boost switching circuit outputs a low level to the MOS tube Q2, and the MOS tube Q2 is forward cutoff, controlling the fault current sampling circuit to switch to a power-taking circuit; at this time, the energy storage capacitor C1 will draw power from the current transformer and gradually increase the capacitor voltage; when the voltage of the energy storage capacitor C1 is greater than the driving voltage of the voltage boost switching circuit, the energy storage capacitor C1 will discharge the voltage boost switching circuit. At this time, the transformer power-taking circuit will The voltage boost switching circuit performs data acquisition and data conversion, the control unit outputs a high level, the transistor Q1 works in the on state, the high level output by the BOOST boost chip N2 passes through the transistor Q1 to the OR gate circuit N1, and the OR gate circuit N1 outputs a high level to the MOS tube Q2, thereby driving the MOS tube Q2 of the fault current sampling circuit to be forward-conducted, so that the fault current sampling circuit switches and remains in the DC circuit; when the voltage of the discharged energy storage capacitor C1 gradually decreases and is less than the driving voltage, and the control unit outputs a low level to the transistor Q1, the fault current sampling circuit switches to the power-taking circuit, and the energy storage capacitor C1 takes power from the mutual inductor again, so that when there is no DC power supply V1, the energy storage capacitor C1 remains in one of the self-powering state and the discharge state and can switch back and forth.

[0016] The main problem that this patent needs to solve is how to achieve that after the external power supply circuit is switched to the self-powered circuit, the capacitor will not frequently switch between the charging and discharging states and affect the technical effect of collecting the secondary current signal. In order to solve the above problems, this patent first uses the rectifier bridge D1 to rectify the sinusoidal current for reading and calculating the current signal. When the voltage of the DC power supply V1 is greater than the voltage of the voltage regulator Z1, the OR gate and the BOOST boost chip N1 are used to cooperate with each other to drive and output the corresponding high level to turn on the MOS tube Q2, thereby controlling the flow direction of the AC full-bridge rectifier wave and realizing the secondary current signal reading when there is external power. When there is no DC power supply V1 or its voltage is lower than the voltage of the voltage regulator Z1, the OR gate and the BOOST boost chip N1 are used. 1 cooperates with the control unit to drive, so that the transistor Q1 is not conducting, and the corresponding low level is output to cut off the MOS tube Q2, so as to control the current flow to the switching circuit to allow the capacitor to draw power from the mutual inductor, and then flow into the sampling module after drawing power, so as to realize the secondary current signal reading in the case of no external power. When the capacitor voltage reaches the feedback voltage of the boost chip, the transistor Q1 is turned on and outputs a high level to the MOS tube Q2 for conduction. At this time, the fault current acquisition circuit flows in the same way as when there is power from the DC power supply V1, and the AC full-bridge rectifier wave flows into the sampling resistor in the same way. When the capacitor voltage changes and switches between the power-drawing and discharge states, the control unit needs to change the level output to the transistor Q1, and the capacitor will not directly switch between the self-power-drawing state and the discharge state, making the charging and discharging of the capacitor more stable, avoiding the continuous switching of the capacitor in the charging and discharging state, resulting in a decrease in the accuracy of the mutual inductance sampling, and at the same time preventing the abnormal power-drawing of the capacitor, so that the capacitor can output sufficient voltage.

Claims

1. A current transformer sampling power self-switching circuit capable of stably taking power, characterized in that: include, DC power supply; A current transformer as the input end of the circuit, and a rectifier bridge coupled to the current transformer; A fault current sampling circuit for collecting secondary current signals, the input end of which is coupled to the rectifier bridge; The fault current sampling circuit includes a chargeable and dischargeable energy storage capacitor; A sampling module for sampling a secondary current signal and a MOS tube that is forward-conducted at a high level; the fault current sampling circuit can be specifically divided into two power-taking circuits and a DC circuit that can be switched on and off with each other, the MOS tube in the DC circuit is in a forward-conducting state, and the AC full-bridge rectified wave passing through the rectifier bridge can directly flow into the sampling module through the turned-on MOS tube, and finally flow back to the rectifier bridge to form a loop, the MOS tube in the power-taking circuit is in a forward-cutoff state, and the AC full-bridge rectified wave passing through the rectifier bridge passes through the energy storage capacitor and charges the energy storage capacitor, then flows into the sampling module, and finally flows back to the rectifier bridge to form a loop; A voltage boost switching circuit for controlling the switching between the DC circuit and the power taking circuit, wherein the input end of the voltage boost switching circuit is coupled to the DC power supply and the energy storage capacitor, and the output end of the voltage boost switching circuit is coupled to the MOS tube; the voltage boost switching circuit is provided with a driving voltage, and when the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the input voltage of the voltage boost switching circuit is made greater than the driving voltage, and after data collection and data conversion, the voltage boost switching circuit outputs a high level to the MOS tube, and the MOS tube is forward-conducted, and the fault current sampling circuit is controlled to switch to the DC circuit; The voltage boost switching circuit includes a BOOST boost chip, an OR gate circuit, a DC power supply, a first resistor, a second resistor, a third resistor, a fourth resistor, a voltage regulator, a triode and a control unit; The output end of the DC power supply is coupled to the second input end and the second resistor in the OR gate circuit respectively after passing through the first resistor and the voltage regulator tube. The triode is coupled to the output end of the BOOST boost chip, the first input end of the OR gate circuit and the control unit respectively. The output end of the OR gate circuit is coupled to the MOS tube. The second input end of the OR gate circuit is coupled to the DC power supply, the first resistor, the voltage regulator tube and the second resistor respectively and grounded. The input end of the BOOST boost chip is coupled to the third resistor and the fourth resistor for voltage division respectively. When the voltage of the DC power supply is greater than the voltage regulator tube voltage, the high level is output through the first resistor to the second input end of the OR gate circuit and through the second resistor to the ground end, and the high level is output to the input end of the BOOST boost chip, and the high level is output at the output end of the BOOST boost chip, and then to the OR gate circuit through the triode, so that the OR gate circuit outputs a high level to the MOS tube, driving the MOS tube to conduct; When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the working state of the OR gate circuit is controlled by the control unit and the boost chip. When the voltage of the energy storage capacitor is lower than the driving voltage, after data collection and data conversion, the control unit outputs a low level to the transistor, and the transistor works in a non-conducting state. The voltage boost switching circuit outputs a low level to the MOS tube, and the MOS tube is forward cutoff, controlling the fault current sampling circuit to switch to a power-taking circuit; at this time, the energy storage capacitor will draw power from the current transformer and gradually increase the capacitor voltage; when the voltage of the energy storage capacitor is greater than the driving voltage of the voltage boost switching circuit, the energy storage capacitor will discharge the voltage boost switching circuit. At this time, the transformer power-taking circuit will The voltage boost switching circuit is subjected to data acquisition and data conversion, the control unit outputs a high level, the transistor works in the on state, the high level output by the BOOST boost chip is transmitted to the OR gate circuit via the transistor, and the OR gate circuit outputs a high level to the MOS tube, thereby driving the MOS tube of the fault current sampling circuit to be forward-conducted, so that the fault current sampling circuit is switched and maintained in the DC circuit; when the voltage of the energy storage capacitor after discharge gradually decreases and is less than the driving voltage, and the control unit outputs a low level to the transistor, the fault current sampling circuit is switched to the power-taking circuit, and the energy storage capacitor takes power from the mutual inductor again, so that in the absence of DC power supply, the energy storage capacitor remains in one of the self-powering state and the discharge state and can switch back and forth.

2. According to claim 1, a current transformer sampling power self-switching circuit capable of stable power supply, characterized in that: The voltage boost switching circuit includes a BOOST boost chip, a triode, and an OR gate circuit; The input end of the BOOST boost chip is coupled to the DC power supply and the energy storage capacitor respectively, the output end of the BOOST boost chip is coupled to the triode, the triode is coupled to the input end of the OR gate circuit, and the output end of the OR gate circuit is coupled to the MOS tube; when the voltage of the DC power supply is greater than the voltage of the voltage regulator tube, the DC power supply inputs electric energy to the BOOST boost chip, and the BOOST boost chip outputs a high level, which is transmitted to the OR gate circuit through the triode, and the OR gate circuit outputs a high level to the MOS tube, driving the MOS tube to turn on. At this time, the secondary sinusoidal wave current of the current transformer is first rectified into an AC full-bridge rectified wave through the rectifier bridge, and then passes through the turned-on MOS tube and the sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows through the rectifier bridge to the current transformer, completing the DC loop of the fault current sampling circuit.

3. According to claim 2, a current transformer sampling power self-switching circuit capable of stably drawing power, characterized in that: When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the OR gate circuit outputs a low level to the MOS tube, so that the MOS tube is cut off, and the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave by the rectifier bridge. The AC full-bridge rectified wave flows to the energy storage capacitor for charging, and then flows back to the sampling module and the rectifier bridge to the current transformer. The control unit outputs a low level and switches the fault sampling circuit to a power-taking circuit. When the voltage of the energy storage capacitor after charging is greater than the feedback voltage of the BOOST boost chip, the control unit outputs a high level to the triode to turn it on, the capacitor performs a discharge operation, the BOOST boost chip outputs a high level to the OR gate circuit, and the OR gate circuit outputs a high level to drive the MOS tube to turn on. At this time, the secondary sinusoidal current at the input end is first rectified into an AC full-bridge rectified wave through the rectifier bridge, and then passes through the turned-on MOS tube and the sampling module, and the transformer secondary current signal is calculated in the sampling module, and finally flows back to the rectifier bridge to the current transformer, switching the fault current sampling circuit to a DC circuit; When the capacitor is continuously discharged and the capacitor voltage is less than the feedback voltage of the BOOST chip, the control unit outputs a low level to the transistor to make it non-conductive, the MOS tube is forward-cut off, and the capacitor draws power from the current transformer again to perform charging operation.

4. According to claim 3, a current transformer sampling power self-switching circuit capable of stable power supply is characterized in that: The sampling module includes a sampling resistor, a signal conditioning unit and a sampling unit. When a DC power supply is supplied, one end of the DC power supply outputs a voltage and is grounded after passing through a voltage-dividing resistor, and the other end outputs a voltage to the input end of the BOOST boost chip. At this time, the voltage at the input end of the BOOST boost chip is greater than the feedback voltage of the BOOST boost chip. The BOOST boost chip outputs a high level to the input end of the OR gate circuit. The OR gate circuit outputs a high level to the gate of the MOS tube according to the logic, and the MOS tube is forward-conducted. At this time, the secondary sinusoidal current of the input current transformer is rectified by the rectifier bridge, and directly flows to the sampling resistor through the source and drain of the MOS tube in the on state. The voltage signal at both ends of the sampling resistor enters the signal conditioning unit, and then enters the sampling unit, and finally flows back to the rectifier bridge and the current transformer to form a loop.

5. According to claim 4, a current transformer sampling power self-switching circuit capable of stable power supply is characterized in that: When there is no DC power supply or its voltage is lower than the voltage of the voltage regulator tube, the voltage across the energy storage capacitor is less than the feedback voltage of the BOOST boost chip, or the gate circuit outputs a low level to the gate of the MOS tube, the MOS tube is cut off, and the AC full-bridge rectifier wave flows into the capacitor through the diode, then flows back to the sampling resistor, and finally flows back to the rectifier bridge to the current transformer. The control unit makes the transistor non-conductive; when the capacitor voltage is greater than the feedback voltage of the BOOST boost chip after power is taken, the capacitor starts to discharge. At this time, the capacitor acts as an internal power supply, and its output end is connected to the input end of the BOOST boost chip, so that the BOOST boost chip outputs a high level, and the control unit turns on the transistor, and the gate circuit The output is high level to the MOS tube until the MOS tube is turned on. At this time, the secondary sinusoidal current of the input current transformer is rectified by the rectifier bridge, and then flows directly to the sampling resistor through the MOS tube in the on state. The voltage signal at both ends of the sampling resistor enters the signal conditioning unit, and then enters the sampling unit, and finally flows back to the rectifier bridge and the current transformer to form a loop. When the discharge voltage gradually decreases to be less than the feedback voltage of the BOOST boost chip, the gate circuit outputs a low level to the MOS tube, and the MOS tube is cut off. The AC full-bridge rectified wave will flow into the capacitor through the diode, and then flow back to the sampling resistor, and finally flow back to the rectifier bridge to the current transformer, thereby repeatedly switching the charging state and the discharging state.

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