CN204376516U - A kind of self-powered super capacitor energy-storing power supply detected for line fault - Google Patents

Abstract

The utility model discloses a self-powered supercapacitor energy storage power supply for line fault detection, comprising a rectifier circuit connected between a current transformer and a fault detection device and used to provide power output, a pre-charging and bypass switch circuit, and The pre-charging and bypass switch circuits are connected to the bidirectional controllable switch circuit used to control the charging and discharging of the supercapacitor, and the charging and discharging control circuit connected to the bidirectional controllable switching circuit and used to control the opening and closing of the bidirectional controllable switching circuit, Connected with the charge and discharge control circuit and the bidirectional controllable switch circuit for energy storage is a super capacitor, connected between the pre-charge and bypass circuit and the reference circuit for overvoltage protection control and drive overvoltage control and drive circuit, the input end of the reference circuit is connected to the precharge and bypass switch circuit, and the output end is connected to the charge and discharge control circuit and the overvoltage control and control drive circuit. The utility model can run stably for a long time in the line fault detection.

Description

A self-powered supercapacitor energy storage power supply for line fault detection

technical field

The utility model belongs to the field of line fault detection, in particular to a self-powered supercapacitor energy storage power supply for line fault detection.

Background technique

At present, the DC power supply used in transmission line fault detection usually has the following methods: ①Directly use lithium battery pack or storage battery as the power supply of the line fault detection device; ②Use solar panels and batteries for power supply; Power is taken from the primary cable line, supplemented by battery or lithium battery energy storage to achieve uninterrupted power supply. However, these traditional methods have problems in applications requiring long life and high reliability. Method ① is purely powered by lithium batteries or batteries, which can reduce the size of the line fault detection device and be put into use quickly and conveniently. However, the service life of lithium batteries and batteries is short, and the performance of lithium batteries and batteries is greatly affected by the ambient temperature. Method ② uses solar panels and batteries, which can meet the long-term work without external power supply, and is environmentally friendly and energy-saving. However, the size of the line fault detection device is greatly increased by solar panels and batteries, and the conversion of solar panels Efficiency is greatly affected by factors such as weather, climate, and environment, while the battery itself has a short service life, and its charge and discharge performance is affected by temperature. Method ③ uses the current transformer to take power from the primary cable line, and supplements it with battery or lithium battery energy storage to achieve uninterrupted power supply. Compared with method ①②, this method takes into account the size and service life of the fault detection device. It is the first two methods. It is unmatched by readers and is currently the most common way to use it.

However, the current of the high-voltage bus on the primary side of the current transformer is very small during normal operation. Even if there is a line fault that generates an instantaneous high current, the battery or lithium battery cannot obtain enough power due to the problem that the charging and discharging current of the battery and lithium battery cannot be too large. The energy will be in the state of discharge for a long time, and there are defects such as short service life, low power density, and discharge performance affected by temperature.

Therefore, for applications that require long life and high reliability, there are some limitations in using traditional methods ①②③ for power supply.

Utility model content

The purpose of the utility model is to provide a self-powered supercapacitor energy storage power supply for line fault detection, so as to solve the problems existing in the existing self-power supply for line fault detection.

In order to achieve the above object, the utility model adopts the following technical solutions:

A self-powered supercapacitor energy storage power supply for line fault detection, including a rectifier circuit, a pre-charge and bypass switch circuit connected to the rectifier circuit for providing power output and overvoltage protection, and a pre-charge and bypass switch circuit The two-way controllable switch circuit used for energy storage charging and discharging connected to the switch circuit in two directions, the charge and discharge control circuit used to control the on-off of the bidirectional switch tube connected to the two-way controllable switch circuit, and the two-way controllable switch circuit The supercapacitor used for charging energy storage is connected, the overvoltage control and control driving circuit used for overvoltage control and its control driving is connected with the precharging and bypass switch circuit, and the overvoltage control and its control driving circuit and The reference circuit used to generate the reference voltage connected to the charge and discharge control circuit.

Preferably, the input end of the rectification circuit is connected to a current transformer.

Preferably, the rectifier circuit is composed of a rectifier bridge, and the precharge and its bypass switch circuit are connected after the rectifier circuit; the precharge and its bypass switch circuit includes a diode D1, a bypass enhanced PMOS switch tube Q2, and a voltage dividing sampling resistor R3 , voltage sampling resistor R4, electrolytic capacitor C1; the V+ terminal and V- terminal of the rectifier bridge are connected in parallel to the bypass enhanced PMOS switch tube Q2; the V+ terminal of the rectifier bridge is connected to the anode of the diode D1, and the cathode of the diode D1 is connected to the electrolytic capacitor C1 The positive end of the electrolytic capacitor C1 is connected in parallel between the cathode of the diode D1 and the ground; a set of voltage sampling resistor R3 and a voltage dividing sampling resistor R4 are connected in parallel after the diode D1; The voltage VCC at both ends of the capacitor C1 is provided to the bidirectional controllable switch circuit, the overvoltage control and its driving circuit, the charge and discharge control circuit and the reference circuit, and also provides the output voltage VO to the fault detection device.

Preferably, the bidirectional controllable switch circuit includes an enhanced PMOS switch tube Q1, a drive resistor R1 and a triode VT1; the source S of the switch tube Q1 is connected to the positive terminal of the electrolytic capacitor C1, the drain D is connected to the positive terminal of the supercapacitor, and the gate The pole G is connected to the collector of the triode VT1, the drive resistor R1 is connected between the gate and source of the switch tube Q1, the emitter of the triode VT1 is connected to the ground; the negative terminal of the supercapacitor is grounded.

Preferably, the overvoltage control and its drive control circuit include an overvoltage detection control circuit and a drive circuit; the overvoltage detection control circuit is composed of a resistor R2 and a resistor R5 voltage divider sampling circuit connected in parallel to the two ends of the electrolytic capacitor C1; the drive circuit includes Integrated operational amplifier U1, resistor R7 and resistor R9; the integrated operational amplifier U1 feeds back the output terminal to the inverting input terminal through resistor R7 to form negative feedback, and resistor R2 and resistor R5 are connected to both ends of the supercapacitor in parallel, and the supercapacitor is collected by voltage division The voltage V2 at both ends is given to the non-inverting terminal of the integrated operational amplifier U1, and is compared with the reference voltage Vref to form a driving control signal for the PMOS switch tube Q2.

Preferably, the charging and discharging control circuit includes integrated operational amplifier U2, resistor R6, resistor R8, resistor R10, resistor R11, resistor R13, diode D3, diode D4, capacitor C3 and integrated operational amplifier U4; integrated operational amplifier U2 and integrated operational amplifier Resistor R8 and capacitor C2, resistor R11 and capacitor C3 feed back from their respective output terminals to integrated op amp U2 and the inverting input of integrated op amp U4 to form negative feedback, and the non-inverting input of integrated op amp U2 is divided Voltage sampling resistor R3 and voltage dividing sampling resistor R4 divide the voltage V1; the reverse end of the integrated op amp U2 is input from the reference reference voltage Vref through the resistor R10, and the input of the non-inverting end of the integrated op amp U4 is also the voltage V1 , and the reverse terminal input is the voltage V2 obtained by dividing the resistance R2 and the resistance R5 connected in parallel at both ends of the supercapacitor; the cathode of the diode D4 is connected to the output terminal of the integrated operational amplifier U2, and the anode of the diode D4 is connected to the integrated operational amplifier through the resistor R6. The output terminal of the amplifier U4 is connected, the anode of the diode D3 is connected to the anode of the diode D4, and the cathode of the diode D3 is connected to the base of the triode VT1 in the main circuit to provide a driving signal.

Preferably, the reference circuit includes a reference U3, a current-limiting resistor R12 and a capacitor C4; the cathode of the reference U3 is connected to the positive terminal of the electrolytic capacitor C1 in the pre-charging circuit and the bypass switch circuit through the current-limiting resistor R12, the anode is grounded, and the reference terminal and The cathode is connected to output the reference reference voltage Vref of the entire power supply, and the reference terminal is filtered to the ground through a capacitor C4.

Compared with the prior art, the utility model has the following beneficial effects: in the utility model, after the circuit breaks down, the circuit will generate an instantaneous large current, and the electric energy obtained by the current transformer from the circuit will charge the pre-charging circuit through the rectifier circuit, and then charge the supercharging circuit. Capacitor charging. The supercapacitor has stored enough energy in a short period of time. When the line fault causes a trip and power failure, the supercapacitor can be reversely discharged through the pre-charging circuit to provide enough power to maintain the normal operation of the external detection circuit. Usually during a line fault (only a few tens of mS), the supercapacitor has stored enough energy to provide the required power to the fault detection circuit. In this way, in the case of no need for external power supply, a simple and stable analog circuit is used to realize the charge and discharge control of the pre-charging circuit and the super capacitor, which can overcome the existing problems in the existing line fault detection self-power supply, and improve the efficiency of line fault detection. Sensing plays an important role in self-powered power applications. Under normal circumstances, the line current is small, and the self-powered supercapacitor energy storage power supply and line fault detection device for line fault detection can be in a dormant state.

A self-powered supercapacitor energy storage power supply for line fault detection in the utility model has many advantages such as large storage energy, large charging current, fast speed, long cycle life, high power density, good ultra-low temperature characteristics, and environmental protection. On the basis of method ③, it is proposed that the instantaneous high current generated by the line fault can realize the fast charging and energy storage of the supercapacitor. Compared with batteries and lithium batteries, supercapacitors have the advantages of lower series equivalent resistance, longer service life, wider temperature operating range, wider voltage variation range, and maintenance-free.

In the utility model, when the output line fails, the current flowing through the line increases rapidly, and the current transformer takes power and passes through the rectification circuit to make the voltage of the pre-charging circuit rise to the preset value quickly, and VCC can be provided externally, and then The bidirectional controllable switch circuit turns on the supercapacitor to start charging and storing energy. After the line fault causes the switch to trip, the supercapacitor starts to discharge to provide the required power for the pre-charging circuit and other detection equipment. In the case of no need to provide an external power supply, it can run stably for a long time in line fault detection, and realize the self-power supply requirement for line fault detection.

Description of drawings

Figure 1 is a schematic block diagram of a self-powered power supply for fault detection;

Fig. 2 is a schematic diagram of a fault detection self-powered power supply circuit.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

Please refer to shown in Fig. 1, a kind of self-powered supercapacitor energy storage power supply that the utility model is used for line fault detection, the self-powered power supply circuit of fault detection is to be connected between current transformer and supercapacitor, comprises rectification circuit 1 1. The pre-charge and bypass switch circuit 2 connected to the rectifier circuit 1 is used to provide power output and overvoltage protection. The control switch circuit 3, the charging and discharging control circuit 5 connected with the bidirectional controllable switch circuit 3 for controlling the on-off of the bidirectional switch tube, and the supercapacitor connected with the bidirectional controllable switch circuit 3 for charging and storing energy 7. The overvoltage control and control drive circuit 4 connected with the pre-charging and bypass switch circuit 2 for overvoltage control and its control drive, and the overvoltage control and its control drive circuit 4 and the charge and discharge control circuit 5. A reference circuit 6 connected to generate a reference voltage. The precharge circuit and bypass switch circuit 2 provide VCC to the bidirectional controllable switch circuit 3, overvoltage control and drive circuit 4, charge and discharge control circuit 5, and reference circuit 6, and also provide output voltage to the external fault detection device.

When the line fails, the current flowing through the line increases rapidly, and the electric energy obtained from the line through the transformer passes through the rectifier circuit 1 and becomes DC to charge the pre-charging and bypass switch circuit 2, and the voltage of the pre-charging circuit rises. When it reaches the preset value, the charge and discharge control circuit 5 acts to make the bidirectional controllable switch circuit 3 conduct to charge and store the energy for the supercapacitor 7 . When the line short-circuit fault causes a trip and power failure, the voltage of the pre-charge and its bypass switch circuit 2 drops, and the super capacitor 7 is used as a backup power supply to discharge the pre-charge circuit 2 through the bidirectional controllable switch circuit 3, to the reference circuit 6 and other fault detection Circuit power supply. The over-voltage control and its control drive circuit 4 are used to drive the pre-charging bypass switch circuit 2 to prevent damage to the supercapacitor 7 due to excessively high charging voltage.

As shown in Figure 2, the circuit diagram of the utility model fault detection self-power supply circuit is provided; the whole circuit is divided into 7 parts: rectifier circuit 1, pre-charging and bypass switch circuit 2, bidirectional controllable switch circuit 3, overvoltage control and its Control drive circuit 4 , charge and discharge control circuit 5 , reference circuit 6 , supercapacitor 7 . The specific connection is: the current transformer takes the electric energy from the line and passes through the rectifier bridge BRIGER1, and connects a bypass enhanced NMOS switch Q2 (such as IRF640), connects a diode D1 in series, and connects a group of diodes in parallel after the diode D1 The voltage-dividing sampling resistor R3, the voltage-dividing sampling resistor R4 and another electrolytic capacitor C1 form the pre-charging and bypass switching circuit 2 . The pre-charging and bypass switch circuit 2 supplies external power supply VCC to the integrated operational amplifiers U1, U2, U4 and the reference U3 (TL431). After the pre-charging and bypass switch circuit 2, an enhanced PMOS (such as IRF9540) switch tube Q1 is connected in series, and a set of voltage sampling resistors R2 and R5 are connected behind the switch tube Q1, between the gate and source of the switch tube Q1 A drive resistor R1 is connected between them, the source S of the switch tube Q1 is connected to the positive terminal of the electrolytic capacitor C1, the drain D is connected to the positive terminal of the supercapacitor 7 (sc), and the negative terminal of the supercapacitor 7 is grounded; the enhanced PMOS switch The gate of the transistor Q1 is connected to the collector of an NPN (for example, 8050) transistor VT1 , and the emitter of the transistor VT1 is grounded. This part forms the bidirectional controllable switch circuit 3 . The base drive signal of the transistor VT1 is provided by parallel connection of the output of the integrated operational amplifier U2 (eg LM358) and the output of the integrated operational amplifier U4 (eg LM358). The integrated operational amplifier U2 and the integrated operational amplifier U4 are respectively composed of resistor R8, capacitor C2, resistor R11, and capacitor C3 from their respective output terminals to the inverting input terminal of the integrated operational amplifier to form negative feedback. The input of the non-inverting terminal of the integrated operational amplifier U2 is The voltage V1 divided by the voltage-dividing sampling resistor R3 and the voltage-dividing sampling resistor R4 in the main circuit, the reverse input is the reference reference voltage Vref, the input of the non-inverting terminal of the integrated operational amplifier U4 is also the voltage V1, and the input of the reverse terminal The voltage V2 is obtained by dividing the voltage by the voltage dividing resistors R2 and R5 in the main circuit; the cathode of the diode D4 is connected to the output terminal of the integrated operational amplifier U2, the anode is connected to the output terminal of the integrated operational amplifier U4 through the resistor R6, and the output terminal of the diode D3 The anode is connected to the anode of the diode D4, and the cathode of the diode D3 is connected to the base of the NPN transistor VT1 in the main circuit to provide a driving signal. This part is the charge and discharge control circuit 5. The integrated operational amplifier U1 (such as LM358) feeds back from the output terminal to the inverting input terminal through the resistor R7 to form a negative feedback. The input of the non-inverting terminal is V2 obtained by sampling the main circuit and connected with resistors R2 and R5. The input of the negative terminal is It is the reference reference voltage Vref, and the output terminal provides the driving signal of the NMOS switch tube Q2 in the main circuit. This part constitutes the overvoltage control and control driving circuit 4 . The VCC provided by the pre-charging circuit is connected to the cathode of the reference U3 (TL431) through a series connection of a current limiting resistor R12, the anode of the reference U3 is grounded, and the reference terminal is returned to the anode terminal as the output terminal of the reference voltage, outputting Vref, and the other reference The terminal is connected to the ground through a capacitor C4 for filtering, and this part is the reference circuit 6 . The positive terminal of the supercapacitor 7 is connected to the drain of the enhanced switch tube Q1, and the negative terminal is connected to the ground, which is the energy storage power supply for the entire line fault detection self-power supply. The above are the seven components of the self-powered power supply for fault detection.

The working principle of the self-powered supercapacitor energy storage power supply for line fault detection: for the self-powered supercapacitor energy storage power supply for line fault detection of the utility model, when the line fails, before the trip and power failure are caused, the power flow through the line The current increases rapidly, and the electric energy from the line is obtained through the current transformer. After the full-wave rectification BRIGR1, the pre-charging and bypass switch circuit 1 is charged through the diode D1. At this time, the voltage at both ends of the electrolytic capacitor C1 rises; At the beginning of charging, the voltage V1 obtained by sampling the non-inverting terminal of the integrated operational amplifier U2 is lower than the reference reference voltage Vref of the negative terminal, and the input voltage V1 of the non-inverting terminal of the integrated operational amplifier U4 is higher than the input voltage V2 of the inverting terminal, so the integrated operational amplifier U2 The output voltage decreases, and the output voltage of the integrated operational amplifier U4 increases. At this time, the diode D4 is first turned on, and the anode potential of the diode D3 is pulled down, so that the transistor NPN works in the cut-off state, the PMOS switch Q2 is not turned on, and the supercapacitor is not charged. , when the voltage value of the pre-charging circuit exceeds the preset value, the voltage V1 of the non-inverting terminal of the integrated operational amplifier U2 is higher than the reference voltage Vref of the negative terminal, and the voltage V1 of the non-inverting terminal of the integrated operational amplifier U4 is higher than the voltage V2 of the inverting terminal. The output voltage of the integrated operational amplifier U2 rises, and the output voltage of the integrated operational amplifier U4 also increases. At this time, the diode D4 is cut off, the diode D3 is turned on, the triode VT1 works in the amplification region (then it will work in the saturation region), and the PMOS switch Q2 Start to gradually turn on and start charging the supercapacitor. With the conduction of the PMOS switch Q2, the supercapacitor is connected, so that the source potential VCC of the PMOS is pulled down. At this time, the output voltage of the integrated operational amplifier U2 decreases, and the voltage of the integrated operational amplifier U4 increases, and the diode D4 will appear. When the anode of the diode D3 is connected, the anode potential of the diode D3 is pulled down, and the clamping position is about 1V. At this time, VT1 will work in the cut-off area, and the switch tube Q1 will not be turned on. In this way, the voltage across the electrolytic capacitor C1 of the pre-charging circuit will rise, which will re-enable the integration The output voltage of operational amplifier U2 rises, the output voltage of U4 rises, diode D4 does not conduct, diode D3 conducts, triode VT1 will work in the saturation region, switch tube Q1 will be turned on again, and charge the supercapacitor. The bidirectional controllable switch circuit is in a dynamic charging process. In addition, U1 forms an operational amplifier to form an overvoltage protection circuit. At this time, the output voltage is not enough to drive the switch tube Q2 to conduct. The voltage of the pre-charging circuit and the supercapacitor continues to rise. When the voltage across the supercapacitor rises above the preset value, the sampling voltage V2 will be higher than the reference voltage Vref. At this time, the output voltage of the integrated operational amplifier rises, and U1 at this time The rise of the output voltage turns on the NMOS switch Q2, short-circuits the circuit behind the switch Q2, and protects the supercapacitor, thereby realizing overvoltage protection. When a line fault causes the switch to trip, it is necessary to provide energy to the fault detection circuit, which will inevitably cause the potential of the electrolytic capacitor C1 of the pre-charging circuit to drop, and the super capacitor starts to reversely discharge the pre-charging circuit to provide enough energy to the fault detection circuit .

Claims (7)

1. A self-powered supercapacitor energy storage power supply for line fault detection, characterized in that it comprises a rectifier circuit (1), a precharge for providing power output and overvoltage protection connected with the rectifier circuit (1) and a bypass switch circuit (2), a bidirectional controllable switch circuit (3) connected to the pre-charging and bypass switch circuit (2) for energy storage charging and discharging, and a bidirectional controllable switch circuit (3) The charge and discharge control circuit (5) connected to control the on-off of the bidirectional switch tube, the supercapacitor (7) connected to the bidirectional controllable switch circuit (3) for charging and storing energy, and the pre-charging and bypass The overvoltage control and control drive circuit (4) connected to the switch circuit (2) for overvoltage control and its control drive is connected to the overvoltage control and its control drive circuit (4) and the charge and discharge control circuit (5). A reference circuit (6) connected to generate a reference voltage. 2. A self-powered supercapacitor energy storage power supply for line fault detection according to claim 1, characterized in that the input end of the rectification circuit (1) is connected to a current transformer. 3. A kind of self-powered supercapacitor energy storage power supply that is used for line fault detection according to claim 1, is characterized in that, rectifier circuit (1) is made of rectifier bridge, precharge and its bypass switch circuit (2) Connected after the rectifier circuit (1); the pre-charging and bypass switch circuit (2) includes a diode D1, a bypass enhanced PMOS switch tube Q2, a voltage-dividing sampling resistor R3, a voltage-dividing sampling resistor R4, and an electrolytic capacitor C1; The V+ terminal and V- terminal of the bridge are connected in parallel to the bypass enhanced PMOS switch tube Q2; the V+ terminal of the rectifier bridge is connected to the anode of the diode D1, the cathode of the diode D1 is connected to the positive terminal of the electrolytic capacitor C1, and the electrolytic capacitor C1 is connected in parallel to the diode D1 Between the cathode and the ground; a group of voltage sampling resistor R3 and voltage dividing sampling resistor R4 are connected in parallel after the diode D1; the pre-charging and bypass switch circuit (2) provides the voltage VCC from both ends of the electrolytic capacitor C1 to the bidirectional The controllable switch circuit (3), the overvoltage control and its drive circuit (4), the charge and discharge control circuit (5) and the reference circuit (6) also provide the output voltage VO to the fault detection device. 4. A self-powered supercapacitor energy storage power supply for line fault detection according to claim 3, characterized in that the bidirectional controllable switch circuit (3) includes an enhanced PMOS switch tube Q1, a drive resistor R1 and a triode VT1; the source S of the switching tube Q1 is connected to the positive terminal of the electrolytic capacitor C1, the drain D is connected to the positive terminal of the supercapacitor (7), the gate G is connected to the collector of the triode VT1, and the driving resistor R1 is connected to the positive terminal of the switching tube Q1 Between the gate and the source, the emitter of the triode VT1 is connected to the ground; the negative end of the supercapacitor (7) is connected to the ground. 5. A kind of self-powered supercapacitor energy storage power supply for line fault detection according to claim 3, is characterized in that, overvoltage control and drive control circuit (4) thereof comprise overvoltage detection control circuit and drive circuit; The overvoltage detection control circuit is composed of resistor R2 and resistor R5, which are connected in parallel to the two ends of the electrolytic capacitor C1, and a voltage dividing sampling circuit; the driving circuit includes integrated operational amplifier U1, resistor R7 and resistor R9; the integrated operational amplifier U1 passes the resistor R7 to output Terminal feedback to the inverting input terminal to form negative feedback, resistor R2 and resistor R5 are connected to both ends of the super capacitor in parallel, and the voltage V2 at both ends of the super capacitor is collected by voltage division to the non-inverting terminal of the integrated operational amplifier U1, which is compared with the reference reference voltage Vref to form a A drive control signal for the PMOS switch Q2. 6. A self-powered supercapacitor energy storage power supply for line fault detection according to claim 5, characterized in that the charge and discharge control circuit (5) includes an integrated operational amplifier U2, a resistor R6, a resistor R8, and a resistor R10 , resistor R11, resistor R13, diode D3, diode D4, capacitor C3 and integrated operational amplifier U4; integrated operational amplifier U2 and integrated operational amplifier U4 are respectively fed back to The inverting input terminals of integrated operational amplifier U2 and integrated operational amplifier U4 constitute negative feedback, and the input of the non-inverting terminal of integrated operational amplifier U2 is the voltage V1 obtained by dividing the voltage by the sampling resistor R3 and the sampling resistor R4; the integrated operational amplifier U2 The negative terminal of the integrated operational amplifier U4 is input by the reference voltage Vref through the resistor R10, and the input of the non-inverting terminal of the integrated operational amplifier U4 is also the voltage V1, while the negative terminal input is divided by the resistor R2 and the resistor R5 connected in parallel at both ends of the supercapacitor. The voltage V2 obtained by pressing the diode D4; the cathode of the diode D4 is connected to the output terminal of the integrated operational amplifier U2, the anode of the diode D4 is connected to the output terminal of the integrated operational amplifier U4 through the resistor R6, the anode of the diode D3 is connected to the anode of the diode D4, and the anode of the diode D3 The cathode is connected to the base of the triode VT1 in the main circuit to provide a driving signal. 7. A kind of self-powered supercapacitor energy storage power supply that is used for line fault detection according to claim 6, is characterized in that, reference circuit (6) comprises reference U3, current-limiting resistor R12 and electric capacity C4; The negative electrode of reference U3 Connect the positive terminal of the electrolytic capacitor C1 in the pre-charging circuit and the bypass switch circuit (2) through the current limiting resistor R12, the anode is grounded, the reference terminal and the cathode are connected to output the reference reference voltage Vref of the entire power supply, and the reference terminal passes through a capacitor C4 to ground for filtering.