CN212572390U

CN212572390U - Isolated Buck conversion device with input protection

Info

Publication number: CN212572390U
Application number: CN202021556237.5U
Authority: CN
Inventors: 蒋燕君; 蒋汉聂; 孔丽萍; 谷嘉炜; 许程涛; 周凌宜; 郑舒元; 杨鸿伟
Original assignee: Zhejiang Shuren University
Current assignee: Zhejiang Shuren University
Priority date: 2020-07-31
Filing date: 2020-07-31
Publication date: 2021-02-19
Anticipated expiration: 2030-07-31

Abstract

An isolated Buck conversion device with input protection comprises a Buck conversion main circuit with input and output electrical isolation, an auxiliary power supply circuit for supplying power to the Buck conversion main circuit and a drive circuit, an isolation drive circuit for isolating and amplifying PWM signals to drive a field effect tube, and an input over-voltage and under-voltage protection circuit for preventing abnormal operation of the device caused by overhigh or overlow input voltage, wherein the Buck conversion main circuit is respectively connected with an input voltage positive end and an output voltage positive end, the auxiliary power supply circuit is respectively connected with the input voltage positive end, the Buck conversion main circuit and the isolation drive circuit, the isolation drive circuit is respectively connected with the auxiliary power supply circuit, the Buck conversion main circuit and a microcontroller PWM output port, and the input over-voltage and under-voltage protection circuit is respectively connected with a relay coil and the input voltage positive end. The utility model provides a take input protection's isolated form Buck conversion equipment realizes the dual isolation of input and output side and control and drive side, and output voltage is stable, and the ripple coefficient is little, has high reliability.

Description

Isolated Buck conversion device with input protection

Technical Field

The utility model relates to an isolated form Buck conversion equipment of area input protection.

Background

With the increasing application of DC-DC converters in power electronic systems, the technology of switching power supplies is developing towards high efficiency, high reliability, high integration level, etc. Buck conversion circuits are generally classified into non-isolated and isolated types. The non-isolated Buck conversion circuit is relatively simple in structure, high in reliability and high in efficiency, but due to the fact that the conversion circuit is not electrically isolated, once the circuit fails, no barrier exists between input and output, crosstalk can be caused, and the fault range is enlarged. The isolated Buck conversion circuit is relatively complex in structure, the fault rate can be relatively increased, the efficiency can be influenced, and in addition, if the Buck conversion circuit is deviated from the normal working voltage in the use process, the Buck conversion circuit can be caused to work abnormally, and even the Buck conversion circuit is broken down due to faults. Although the main circuit of the isolated Buck conversion circuit is electrically isolated, no electrical isolation is performed between the control circuit and the drive circuit, so that faults caused by the drive side circuit can affect the control side circuit, and damage to a microcontroller chip can be caused.

Disclosure of Invention

In order to overcome the defect that prior art exists, the utility model provides a take input protection's isolated form Buck conversion equipment realizes the dual isolation of input and output side and control and drive side, and output voltage is stable, and the ripple coefficient is little, has high reliability.

The utility model discloses the design that adopts the voltage transformation function to realizing is:

an isolated Buck conversion device with input protection comprises a Buck conversion main circuit with input and output electrical isolation, an auxiliary power supply circuit for supplying power to the Buck conversion main circuit and a drive circuit, an isolation drive circuit for isolating and amplifying PWM signals to drive a field effect tube, and an input over-voltage and under-voltage protection circuit for preventing abnormal operation of the device caused by overhigh or overlow input voltage, wherein the Buck conversion main circuit is respectively connected with an input voltage positive end and an output voltage positive end, the auxiliary power supply circuit is respectively connected with the input voltage positive end, the Buck conversion main circuit and the isolation drive circuit, the isolation drive circuit is respectively connected with the auxiliary power supply circuit, the Buck conversion main circuit and a microcontroller PWM output port, and the input over-voltage and under-voltage protection circuit is respectively connected with a relay coil and the input voltage positive end.

Further, the input overvoltage and undervoltage protection circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a first triode, a first operational amplifier, a second operational amplifier and a relay.

One end of the first resistor is connected with a power supply VCC _2, the other end of the first resistor is connected with the cathode of the first diode and the inverting terminal of the first operational amplifier, the anode of the first diode is connected with a power supply ground GND, one end of the second resistor is connected with the power supply VCC _2, the other end of the second resistor is respectively connected with the cathode of the second diode and the inverting terminal of the second operational amplifier, the anode of the second diode is connected with the power supply ground GND, one end of the third resistor is connected with the positive end of the input voltage, the other end of the third resistor and one end of the fourth resistor are simultaneously connected with the inverting terminal of the first operational amplifier and the inverting terminal of the second operational amplifier, the power supply terminal of the first operational amplifier is connected with the power supply VCC _2, the grounding terminal of the first operational amplifier is connected with the power supply ground, the power supply terminal of the second operational amplifier is connected with the other end of the fourth resistor, and is connected to a power ground GND, the output end of the first operational amplifier and the output end of the second operational amplifier are connected with one end of a fifth resistor, the other end of the fifth resistor is connected with one end of a sixth resistor, the cathode of a third diode and the anode of a fourth diode respectively, the other end of the sixth resistor is connected with a power VCC _2, the anode of the third diode is connected with the power ground GND, the cathode of the fourth diode is connected with one end of a seventh resistor, the other end of the seventh resistor is connected with the base of the first triode, the cathode of the fifth diode is connected with 4 pins of a relay and is connected to the power VCC _2, the anode of the fifth diode is connected with one end of an eighth resistor, the other end of the eighth resistor is connected with the collector of the first triode and the 5 pins of the relay respectively, the emitter of the first triode is connected with the power ground GND, and a pin 1 of the relay is connected with a pin 1 of a direct current input interface of the Buck conversion main circuit and is connected to the positive end of input voltage, a pin 2 of the relay is connected with one end of a seventh capacitor, one end of an eighth capacitor, the positive end of a ninth capacitor, one end of an eighteenth resistor, one end of a tenth capacitor and a pin 1 of the high-frequency transformer of the Buck conversion main circuit, and pins 3 of the relay are suspended.

Still further, the isolation driving circuit comprises a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, a third capacitor, a sixth diode, a seventh diode, a phase inverter chip, a high-speed optical coupler chip and a driving chip.

14 feet of phase inverter chip are connected with power VCC _1, 1 foot of phase inverter chip is connected with microcontroller PWM delivery outlet, 2 feet of phase inverter chip with 3 feet of high-speed opto-coupler chip are connected, 7 feet of phase inverter chip connect power ground GND _1, the one end and the power VCC _1 of ninth resistance are connected, the other end of ninth resistance with 2 feet of high-speed opto-coupler chip are connected, 8 feet of high-speed opto-coupler chip with the one end of tenth resistance is connected, and is connected to power VCC _2, the other end of tenth resistance respectively with 6 feet of high-speed opto-coupler chip, 12 feet of driver chip are connected, 5 feet of high-speed opto-coupler chip with 13 feet of driver chip are connected, and are connected to power ground GND, 9 feet of driver chip are connected with power VCC _2, 1 foot of driver chip respectively with the positive pole of sixth diode, One end of an eleventh resistor is connected, the cathode of the sixth diode and the other end of the eleventh resistor are connected with the gate of the field effect transistor of the Buck conversion main circuit, 2 pins of the driving chip are connected with one end of the first capacitor and one end of the third capacitor and are connected to a power Ground (GND), 3 pins of the driving chip are connected with the other end of the first capacitor and are connected to a power supply VCC _2, 5 pins of the driving chip are connected with one end of the second capacitor, 6 pins of the driving chip are connected with the other end of the second capacitor and the cathode of the seventh diode respectively, and the anode of the seventh diode is connected with the other end of the third capacitor.

Still further, the auxiliary power supply circuit comprises a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a fourth capacitor, a fifth capacitor, a sixth capacitor, an eighth diode, a ninth diode, a twelfth diode, an eleventh diode, a second triode, a third triode, a first inductor, a voltage stabilizing chip and a DC-DC module power supply.

One end of the twelfth resistor and an emitter of the second triode are respectively connected with a positive terminal of an input voltage, the other end of the twelfth resistor and one end of the thirteenth resistor are simultaneously connected with a cathode of the eighth diode, a collector of the second triode is connected with one end of the fourteenth resistor, a base of the second triode is connected with one end of the fifteenth resistor, the other end of the fifteenth resistor is connected with a collector of the third triode, the other end of the thirteenth resistor is connected with a base of the third triode, an emitter of the third triode and a cathode of the ninth diode are simultaneously connected with one end of the sixteenth resistor, the other end of the fourteenth resistor, an anode of the ninth diode, a positive terminal of the sixth capacitor, one end of the first inductor and a positive terminal of the fourth capacitor are simultaneously connected with pin 1 of the voltage stabilizing chip, the anode of the eighth diode, the other end of the sixteenth resistor and the negative end of the sixth capacitor are connected with the anode of the twelfth diode and are connected to a power ground GND, the other end of the first inductor is connected with one end of the seventeenth resistor, the other end of the seventeenth resistor and the cathode of the twelfth diode are simultaneously connected with the cathode of the eleventh diode, the anode of the eleventh diode is connected with the 5 pin of the high-frequency transformer of the Buck conversion main circuit, the 2 pin of the voltage stabilizing chip and the negative end of the fourth capacitor are connected with the 2 pin of the DC-DC module power supply and are connected to the power ground GND, the 3 pin of the voltage stabilizing chip is connected with the positive end of the fifth capacitor, the negative end of the fifth capacitor is connected with the 1 pin of the DC-DC module power supply and is led out as a power VCC _2 end, and the 4 pin of the DC-DC module power supply is connected with the power ground GND _1, and 6 pins of the DC-DC module power supply are led out as a VCC _1 end of the power supply.

Still further, the Buck conversion main circuit comprises an eighteenth resistor, a nineteenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a fourteenth capacitor, a fifteenth capacitor, a second inductor, a twelfth diode, a thirteenth diode, a fourteenth diode, a high-frequency transformer, a field effect transistor, a direct current input interface and a direct current output interface.

The other end of the seventh capacitor, the other end of the eighth capacitor, the negative terminal of the ninth capacitor, the other end of the eighteenth resistor, the other end of the tenth capacitor, and one end of the nineteenth resistor are connected to pin 2 of the dc input interface and to the power ground GND, the other end of the nineteenth resistor is connected to the cathode of the twelfth diode, the anode of the twelfth diode and pin 3 of the high-frequency transformer are connected to the drain of the fet, the source of the fet is connected to pin 6 of the high-frequency transformer and to the power ground GND, pin 12 of the high-frequency transformer is connected to the anode of the thirteenth diode, the cathode of the thirteenth diode and the cathode of the fourteenth diode are connected to one end of the second inductor, the other end of the second inductor, the positive terminal of the eleventh capacitor, and one end of the twelfth capacitor, One end of a thirteenth capacitor, one end of a fourteenth capacitor and one end of a fifteenth capacitor are connected to pin 1 of the dc output interface and are connected to the positive end of the output voltage, and pin 11 of the high-frequency transformer, the anode of the fourteenth diode, the negative end of the eleventh capacitor, the other end of the twelfth capacitor, the other end of the thirteenth capacitor, the other end of the fourteenth capacitor and the other end of the fifteenth capacitor are connected to pin 2 of the dc output interface and are connected to the power ground GND _ 2.

The utility model has the advantages that:

the utility model adopts the isolated Buck conversion device with input protection, the output voltage is stable, and the ripple factor is small; the high-frequency transformer is adopted to realize voltage conversion between input and output and electrical isolation of the input and output sides, so that electrical crosstalk between the primary side and the secondary side is avoided; the output side of the high-frequency transformer is connected with an LC filter, so that high-frequency clutter can be effectively filtered, and smooth direct current with smaller ripples can be obtained at the output end; the auxiliary power supply circuit is adopted to realize the power supply of the Buck conversion main circuit and the driving circuit, wherein a voltage stabilizing chip L7812CV provides a +12V auxiliary power supply VCC _2, a DC-DC module power supply B1205S2W provides a +5V auxiliary power supply VCC _1, the isolation between the two is realized, and the guarantee is provided for the effective isolation between the control side and the driving side; the high-speed optocoupler is adopted to realize the electrical isolation between the driving circuit and the control circuit, and the driving chip is adopted to realize the amplification of the PWM signal;

the input overvoltage and undervoltage protection circuit realizes the monitoring of the input voltage of the main circuit, prevents the input voltage from influencing the normal work of the Buck conversion main circuit abnormally, and ensures that the high-frequency transformer can be always in a high-efficiency working range. The protection circuit utilizes the characteristics of the double-limit comparator, when the input voltage is between the lower limit voltage and the upper limit voltage (the threshold voltage can be adjusted according to requirements), the overvoltage and undervoltage protection circuit outputs low level, and the main circuit works normally; when the input voltage is lower than the lower limit voltage or higher than the upper limit voltage, the overvoltage and undervoltage protection circuit outputs high level, the triode Q1 is conducted, the relay K acts, the voltage input of the main circuit is cut off, the protection of the system is realized, and the system has high reliability and safety.

Drawings

Fig. 1 is an electrical schematic diagram of the present invention.

Fig. 2 is a circuit diagram of the input over-voltage and under-voltage protection circuit of the present invention.

Fig. 3 is a circuit diagram of the isolation driving circuit of the present invention.

Fig. 4 is a circuit diagram of the auxiliary power supply circuit of the present invention.

Fig. 5 is a circuit diagram of the Buck converter main circuit of the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, an isolated Buck converter with input protection includes a Buck converter main circuit with input and output electrical isolation, an auxiliary power circuit for supplying power to the Buck converter main circuit and the drive circuit, an isolation drive circuit for isolating and amplifying a PWM signal to drive a field effect transistor, and an input over-voltage and under-voltage protection circuit for preventing abnormal operation of the device due to over-high or over-low input voltage.

As shown in fig. 2, the input over-voltage and under-voltage protection circuit: one end of a first resistor R1 is connected to the power supply VCC _2, the other end of the first resistor R1 is connected to the cathode of the first diode D1 and the inverting terminal of the first operational amplifier U1, the operational amplifier is an operational amplifier for short, the anode of the first diode D1 is connected to the power supply ground GND, one end of a second resistor R2 is connected to the power supply VCC _2, the other end of the second resistor R2 is connected to the cathode of the second diode D2 and the inverting terminal of the second operational amplifier U2, the anode of the second diode D2 is connected to the power supply ground GND, one end of a third resistor R3 is connected to the positive input voltage terminal VIN, the other end of the third resistor R3 and one end of a fourth resistor R4 are connected to the inverting terminal of the first operational amplifier U1 and the inverting terminal of the second operational amplifier U2, the other end of the first operational amplifier U1 is connected to the power supply VCC _2, the ground terminal of the first operational amplifier U1, the other end of the second operational amplifier U2 is connected to the power supply ground U2, and is connected to the power ground GND, the output terminal of the first operational amplifier U1 and the output terminal of the second operational amplifier U2 are connected to one end of a fifth resistor R5, the other end of the fifth resistor R5 is connected to one end of a sixth resistor R6, the cathode of a third diode D3 and the anode of a fourth diode D4, respectively, the other end of the sixth resistor R6 is connected to the power VCC _2, the anode of a third diode D3 is connected to the power ground GND, the cathode of a fourth diode D4 is connected to one end of a seventh resistor R7, the other end of the seventh resistor R7 is connected to the base of the first transistor Q1, the cathode of a fifth diode D5 is connected to the 4-pin of the relay K and to the power VCC _2, the anode of a fifth diode D5 is connected to one end of an eighth resistor R8, the other end of an eighth resistor R8 is connected to the collector of the first transistor Q1 and the emitter of the relay K, respectively, the emitter of the first transistor Q1, the pin 1 of the relay K is connected with the pin 1 of the direct current input interface J1 of the Buck conversion main circuit and is connected to an input voltage positive terminal VIN, the pin 2 of the relay K is connected with one end of a seventh capacitor C7, one end of an eighth capacitor C8, the positive terminal of a ninth capacitor C9, one end of an eighteenth resistor R18, one end of a tenth capacitor C10 and the pin 1 of the high-frequency transformer T of the Buck conversion main circuit, and the pin 3 of the relay K is suspended.

As shown in fig. 3, the isolation driving circuit: a pin 14 of an inverter chip U3 is connected with a power supply VCC _1, a pin 1 of an inverter chip U3 is connected with a PWM output port of the microcontroller, a pin 2 of an inverter chip U3 is connected with a pin 3 of a high-speed optical coupling chip U4, a pin 7 of an inverter chip U3 is connected with a power ground GND _1, one end of a ninth resistor R9 is connected with the power supply VCC _1, the other end of the ninth resistor R9 is connected with a pin 2 of the high-speed optical coupling chip U4, a pin 8 of the high-speed optical coupling chip U4 is connected with one end of a tenth resistor R10 and is connected to the power supply VCC _2, the other end of the tenth resistor R10 is connected with a pin 6 of the high-speed optical coupling chip U4 and a pin 12 of the driving chip U5, a pin 5 of the high-speed optical coupling chip U4 is connected with a pin 13 of the driving chip U5 and is connected to the power supply ground, a pin 9 of the driving chip 596U 8 is connected with the power supply VCC _2, a pin 1 of the driving chip U5, the cathode of the sixth diode D6 and the other end of the eleventh resistor R11 are both connected to the gate of the fet Q4 of the Buck converter main circuit, the 2 pin of the driving chip U5 is connected to one end of the first capacitor C1 and one end of the third capacitor C3, and is connected to the power ground GND, the 3 pin of the driving chip U5 is connected to the other end of the first capacitor C1 and is connected to the power VCC _2, the 5 pin of the driving chip U5 is connected to one end of the second capacitor C2, the 6 pin of the driving chip U5 is connected to the other end of the second capacitor C2 and the cathode of the seventh diode D7, and the anode of the seventh diode D7 is connected to the other end of the third capacitor C3.

As shown in fig. 4, the auxiliary power supply circuit: one end of a twelfth resistor R12 and an emitter of a second triode Q2 are respectively connected with an input voltage positive terminal VIN, the other end of the twelfth resistor R12 and one end of a thirteenth resistor R13 are simultaneously connected with a cathode of an eighth diode D8, a collector of a second triode Q2 is connected with one end of a fourteenth resistor R14, a base of the second triode Q2 is connected with one end of a fifteenth resistor R15, the other end of a fifteenth resistor R15 is connected with a collector of a third triode Q3, the other end of the thirteenth resistor R13 is connected with a base of the third triode Q3, an emitter of the third triode Q3 and a cathode of a ninth diode D9 are simultaneously connected with one end of a sixteenth resistor R16, the other end of the fourteenth resistor R14, an anode of a ninth diode D9, a positive terminal of a sixth capacitor C6, one end of a first inductor L1 and a positive terminal of a fourth capacitor C4 are simultaneously connected with a positive terminal of a voltage stabilizing chip U6, and an eighth diode D8, The other end of the sixteenth resistor R16 and the negative end of the sixth capacitor C6 are connected to the anode of the twelfth diode D10, and is connected to the power ground GND, the other end of the first inductor L1 is connected to one end of a seventeenth resistor R17, the other end of the seventeenth resistor R17 and the cathode of the twelfth diode D10 are simultaneously connected to the cathode of an eleventh diode D11, the anode of the eleventh diode D11 is connected to the pin 5 of the high-frequency transformer T of the Buck converter main circuit, the pin 2 of the regulator chip U6 and the negative end of the fourth capacitor C4 are connected to the pin 2 of the DC-DC module power supply U7, and is connected to the power ground GND, pin 3 of the voltage stabilizing chip U6 is connected to the positive terminal of the fifth capacitor C5, the negative terminal of the fifth capacitor C5 is connected to pin 1 of the DC-DC module power supply U7, and the terminal of the power supply VCC _2 is led out, 4 pins of the DC-DC module power supply U7 are connected with a power ground GND _1, and 6 pins of the DC-DC module power supply U7 are led out as the terminal of the power supply VCC _ 1.

As shown in fig. 5, the Buck conversion main circuit: the other end of the seventh capacitor C7, the other end of the eighth capacitor C8, the negative terminal of the ninth capacitor C9, the other end of the eighteenth resistor R18, the other end of the tenth capacitor C10, and one end of the nineteenth resistor R19 are connected to pin 2 of the dc input interface J1 and to the power ground GND, the other end of the nineteenth resistor R19 is connected to the cathode of the twelfth diode D12, the anode of the twelfth diode D12 and the 3-pin of the high-frequency transformer T are connected to the drain of the fet Q4, the source of the fet Q4 is connected to pin 6 of the high-frequency transformer T and to the power ground GND, the pin 12 of the high-frequency transformer T is connected to the anode of the thirteenth diode D13, the cathode of the thirteenth diode D13 and the cathode of the fourteenth diode D14 are connected to one end of the second inductor L8, the other end of the second inductor L6, the positive terminal of the eleventh capacitor C11, the positive terminal of the twelfth capacitor C12, and one end of the thirteenth capacitor C13, One end of a fourteenth capacitor C14 and one end of a fifteenth capacitor C15 are connected to pin 1 of the dc output interface J2 and to the positive output voltage terminal VOUT, and the other end of the high-frequency transformer T, the pin 11, the anode of the fourteenth diode D14, the negative terminal of the eleventh capacitor C11, the other end of the twelfth capacitor C12, the other end of the thirteenth capacitor C13, the other end of the fourteenth capacitor C14, and the other end of the fifteenth capacitor C15 are connected to pin 2 of the dc output interface J2 and to the power ground GND _ 2.

The working process of the utility model is as follows:

the conversion of 48V DC voltage to 12V DC voltage will be described as an example. When the direct current is input, the auxiliary power circuit converts the input direct current into 12V direct current through related circuits such as L7812CV and the like, the DC-DC module power supply converts the 12V direct current into 5V direct current with isolation to be supplied to a driving chip, and meanwhile, the auxiliary power circuit reduces the voltage of the input direct current and supplies the reduced voltage to the Buck conversion main circuit through another path for use. If the direct current input voltage range is between 46V and 50V (the threshold voltage can be adjusted according to requirements), the low level is output by inputting the overvoltage and undervoltage protection circuit, the relay does not act, and the main circuit works normally. The microcontroller outputs a PWM signal, and controls the on and off of a switching tube in the Buck conversion main circuit after the PWM signal is isolated and amplified by the driving circuit. When the switching tube is switched on, 48V direct current input voltage supplies power to a primary coil winding of the high-frequency transformer, and current generates self-induced electromotive force at two ends of the winding; meanwhile, induced electromotive force is generated at two ends of a secondary coil winding of the high-frequency transformer under the action of the mutual inductance M, noise waves are filtered out through an LC filter, and 12V direct current is stably output.

To sum up, the utility model discloses a take input protection's isolated form Buck conversion equipment has realized the isolation step-down transform of high DC voltage to low DC voltage, adopts the input undervoltage protection circuit and keeps apart drive circuit simultaneously, has strengthened system interference immunity, has improved the security and the reliability of system. The utility model discloses output voltage is stable, and the ripple coefficient is little, and the reliability is high, and the security is strong, has certain using value.

Claims

1. An isolated Buck conversion device with input protection is characterized in that: the device comprises a Buck conversion main circuit with input and output electrical isolation, an auxiliary power supply circuit for supplying power to the Buck conversion main circuit and a drive circuit, an isolation drive circuit for isolating and amplifying PWM signals to drive a field effect tube, and an input over-under-voltage protection circuit for preventing abnormal operation of the device caused by overhigh or overlow input voltage, wherein the Buck conversion main circuit is respectively connected with an input voltage positive end and an output voltage positive end, the auxiliary power supply circuit is respectively connected with the input voltage positive end, the Buck conversion main circuit and the isolation drive circuit, the isolation drive circuit is respectively connected with the auxiliary power supply circuit, the Buck conversion main circuit and a microcontroller PWM output port, and the input over-under-voltage protection circuit is respectively connected with a relay coil and the input voltage positive end.

2. The isolated Buck conversion device with input protection of claim 1, wherein: the input overvoltage and undervoltage protection circuit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a first triode, a first operational amplifier, a second operational amplifier and a relay;

3. The isolated Buck conversion device with input protection according to claim 2, wherein: the isolation driving circuit comprises a ninth resistor, a tenth resistor, an eleventh resistor, a first capacitor, a second capacitor, a third capacitor, a sixth diode, a seventh diode, a phase inverter chip, a high-speed optocoupler chip and a driving chip;

4. An isolated Buck conversion device with input protection as claimed in claim 3, wherein: the auxiliary power supply circuit comprises a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a fourth capacitor, a fifth capacitor, a sixth capacitor, an eighth diode, a ninth diode, a twelfth polar tube, an eleventh diode, a second polar tube, a third polar tube, a first inductor, a voltage stabilizing chip and a DC-DC module power supply;

5. The isolated Buck converter device with input protection as claimed in claim 4, wherein: the Buck conversion main circuit comprises an eighteenth resistor, a nineteenth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a fourteenth capacitor, a fifteenth capacitor, a second inductor, a twelfth diode, a thirteenth diode, a fourteenth diode, a high-frequency transformer, a field effect tube, a direct current input interface and a direct current output interface;