CN219779834U - BMS direct-current power supply circuit of lithium iron phosphate battery management system - Google Patents

Abstract

The utility model relates to a Battery Management System (BMS) direct current power supply circuit of a lithium iron phosphate battery, which comprises an input rectifying and control circuit, a DC-DC conversion circuit, a primary output follow current and voltage reduction circuit and a secondary output rectifying and voltage reduction circuit, wherein the input rectifying and control circuit is connected with a battery output voltage, the input rectifying and control circuit is respectively and electrically connected with the DC-DC conversion circuit and the primary output follow current and voltage reduction circuit, the DC-DC conversion circuit is respectively and electrically connected with the primary output follow current and voltage reduction circuit and the secondary output rectifying and voltage reduction circuit, the primary output follow current and voltage reduction circuit outputs a primary 12V direct current power supply, and the secondary output rectifying and voltage reduction circuit outputs a secondary 5V direct current power supply. The secondary 5V direct current power supply is output through the treatments of rectifying and reducing the voltage of 48V-70 output by the battery, voltage transformation, rectifying and filtering and the like, and meanwhile, the primary 12V direct current power supply is output through the primary output follow current and voltage reduction circuit, so that the method has the characteristics of simplicity, low cost, high precision, follow current output, overvoltage protection, stability, reliability and the like.

Description

BMS direct-current power supply circuit of lithium iron phosphate battery management system

Technical Field

The utility model relates to the technical field of electronic circuits, in particular to a Battery Management System (BMS) direct current power supply circuit of a lithium iron phosphate battery.

Background

Lithium iron phosphate batteries are now widely used in the fields of communications, automobiles, medical treatment, electricity, etc., where use in the field of communications is more common. Compared with the original lead-acid battery, the lithium iron phosphate battery has the characteristics of smaller volume, higher energy density, strict charge and discharge management according to the voltage and current threshold value and the like. The battery management system BMS is an important component of the lithium iron phosphate battery, can intelligently, efficiently and stably manage the technical parameters such as voltage, charge and discharge current, capacity and the like of each battery cell of the lithium iron phosphate battery, and simultaneously establishes RS485 communication and an upper computer for data exchange and setting. In order to complete the functions of the battery management system BMS, the performance index of the direct current power supply is high, and the common low-power direct current power supply cannot meet the requirements.

Disclosure of Invention

The utility model aims to solve the technical problem of providing a BMS direct current power supply circuit of a lithium iron phosphate battery management system aiming at the defects of the prior art.

The technical scheme for solving the technical problems is as follows: the utility model provides a lithium iron phosphate battery management system BMS direct current power supply circuit, includes input rectification and control circuit, DC-DC conversion circuit, primary output freewheel and buck circuit and secondary output rectification and buck circuit, input rectification and control circuit inserts battery output voltage, input rectification and control circuit's output respectively with DC-DC conversion circuit and primary output freewheel and buck circuit's input electricity is connected, DC-DC conversion circuit's output respectively with primary output freewheel and buck circuit and secondary output rectification and buck circuit's input electricity is connected, primary output freewheel and buck circuit output primary 12V direct current power supply, secondary output rectification and buck circuit output secondary 5V direct current power supply.

The beneficial effects of the utility model are as follows: according to the lithium iron phosphate battery management system BMS direct current power supply circuit, 48V-70 voltage output by a battery is subjected to rectification, voltage reduction, voltage conversion, rectification, filtering and other treatments through the input rectification and control circuit, the DC-DC conversion circuit and the secondary output rectification and voltage reduction circuit, the output secondary 5V direct current power supply supplies power for the RS485 communication circuit of the battery management system, and meanwhile, the primary 12V direct current power supply is output through the primary output freewheel and voltage reduction circuit to supply power for the control circuit of the battery management system, so that the lithium iron phosphate battery management system BMS direct current power supply circuit has the characteristics of simplicity, low cost, high precision, freewheel output, overvoltage protection, stability, reliability and the like.

Based on the technical scheme, the utility model can also be improved as follows:

further: the input rectifying and controlling circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2, a diode D1, a triode Q2 and a triode Q3, wherein the positive electrode of the diode D1 is electrically connected with the positive output end of a battery, the resistor R2 and the capacitor C1 are sequentially connected in series between the negative electrode of the diode D1 and primary ground, the resistor R1 is connected with the resistor R2 in parallel, the public end of the resistor R2 and the capacitor C1 is electrically connected with the emitter of the triode Q2, the base electrode of the triode Q2 is electrically connected with the resistor R3, the base electrode of the triode Q2 is electrically connected with the collector of the triode Q1 through the resistor R4, the negative output end of the battery is electrically connected with primary ground, the base electrode of the triode Q1 is electrically connected with the control signal of an external controller R5, the base electrode of the triode Q1 is electrically connected with the emitter of the triode Q2, the base electrode of the triode Q2 is electrically connected with the output end of the triode Q3, the base electrode of the triode Q2 is electrically connected with the collector of the triode Q3, and the output end of the triode Q2 is electrically connected with the input end of the triode Q3.

The beneficial effects of the above-mentioned further scheme are: after the voltage output by the battery is rectified and filtered through the diode D1 and the capacitor C1, the triode Q2 and the triode Q3 are controlled to be conducted in sequence according to the controller and output to the input ends of the DC-DC conversion circuit, the primary output follow current and the voltage reduction circuit, and the resistor R1 and the resistor R2 play a role in input current limiting.

Further: the primary output freewheeling and voltage reducing circuit comprises a resistor R6, a resistor R7, a capacitor C3, a diode D3, a zener diode Z1, a zener diode Z2, a transient voltage suppression diode TVS1, a transient voltage suppression diode TVS2, a triode Q4 and a MOS transistor Q5, wherein one output end of the input rectifying and control circuit is electrically connected with a collector of the triode Q4 through the resistor R7, the capacitor C3 is electrically connected between the collector of the triode Q4 and the primary ground, the collector of the triode Q4 is electrically connected with a cathode of the zener diode Z2, the anode of the zener diode Z2 is grounded in the primary, the emitter of the triode Q4 is grounded in the primary ground, the base of the triode Q4 is electrically connected with the anode of the zener diode Z1 through the resistor R6, the cathode of the triode Z1 outputs a primary +12V direct current power supply, one output end of the input rectifying and control circuit is electrically connected with the primary ground, the collector of the zener diode Z1 is electrically connected with the primary MOS power supply, and the primary MOS transistor Q5 is connected with the primary voltage of the primary MOS transistor Q2, and the primary MOS transistor Q4 is connected with the primary voltage of the primary MOS transistor Q5.

The beneficial effects of the above-mentioned further scheme are: the MOS tube Q5 is driven to be conducted by the rectified and filtered battery voltage, and a 12V direct current power supply is output in a step-down mode, so that power is supplied to a battery management system BMS control circuit, after the controller of the battery management system BMS control circuit is electrified, the battery voltage is controlled to be connected to a step-down power supply chip U1 in a DC-DC conversion circuit, after high-frequency step-down DC-DC conversion, the 12V continuous direct current power supply is rectified and output through a diode D3, and the first-stage power supply outputs a follow current function.

Further: the DC-DC conversion circuit comprises a resistor R8, a resistor R9, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a diode D2, a transformer T1 and a step-down power supply chip U1, wherein the input end of the step-down power supply chip U1 is electrically connected with the other output end of the input rectifying and control circuit, the grounding end of the step-down power supply chip U1 is grounded, the output end of the step-down power supply chip U1 is electrically connected with the cathode of the diode D2, the anode of the diode D2 is grounded, the output end of the step-down power supply chip U1 is electrically connected with one end of a primary coil of the transformer T1, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 are connected in parallel between the other end of the primary coil of the transformer T1 and the primary ground, the cathode of the D3 is electrically connected with the anode of the diode D3, the cathode of the D3 is electrically connected with a primary +12V direct current power supply, the output end of the step-down power supply chip U1 is electrically connected with the two ends of the feedback circuit, and the two ends of the feedback circuit are connected with the two ends of the primary coil of the transformer T1 in parallel.

The beneficial effects of the above-mentioned further scheme are: the voltage output by the battery is connected to the input end of the step-down power supply chip U1 after input rectification and filtration, the primary winding of the transformer T1, the capacitor C4, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 form a primary working main loop of the self-excited DC-DC conversion circuit to step down and output, meanwhile, the primary winding of the transformer T1, the capacitor C4, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 form an LC resonance circuit, the resonance frequency of the LC resonance circuit corresponds to the working frequency of the step-down power supply chip U1, the higher primary working efficiency of the DC-DC conversion circuit is achieved, the LC filtering function is achieved, and the diode D2 plays a role in preventing the polarity of the output power supply from reversing.

Further: the secondary output rectifying and voltage reducing circuit comprises a rectifying and filtering circuit and a voltage reducing circuit, wherein two input ends of the rectifying and filtering circuit are respectively and correspondingly and electrically connected with two output ends of the DC-DC conversion circuit, the output end of the rectifying and filtering circuit is electrically connected with the input end of the voltage reducing circuit, and the output end of the voltage reducing circuit outputs a secondary 5V direct current power supply.

The beneficial effects of the above-mentioned further scheme are: the rectification and filtering circuit is used for rectifying and filtering the voltage output by the DC-DC conversion circuit, then the voltage is reduced and converted by the voltage reducing circuit, a 5V direct current power supply is output, the power is supplied to the RS485 communication circuit of the battery management system, and the primary output follow current and voltage reducing circuit and the secondary output rectification and voltage reducing circuit are isolated through the transformer T1 and are not affected by each other.

Further: the rectification filter circuit comprises a diode D4, a capacitor C9, a capacitor C10 and a resistor R10, wherein the positive electrode of the diode D4 is electrically connected with one output end of the DC-DC conversion circuit, the capacitor C9, the capacitor C10 and the resistor R10 are connected in parallel between the negative electrode of the diode D4 and the other output end of the DC-DC conversion circuit, the other output end of the DC-DC conversion circuit is grounded, and the negative electrode of the diode D4 is electrically connected with the input end of the voltage reduction circuit.

The beneficial effects of the above-mentioned further scheme are: after the battery voltage is subjected to DC-DC conversion, the secondary winding of the transformer T1 is subjected to rectification and filtering through a diode D4, a capacitor C9, a capacitor C10, a capacitor C11 and a capacitor C12, clutter components in signals are filtered, and the output voltage is smoother.

Further: the step-down circuit comprises a regulated power supply chip U2, a capacitor C11, a capacitor C12 and a resistor R11, wherein the input end of the regulated power supply chip U2 is electrically connected with the output end of the rectifying and filtering circuit, the grounding end of the regulated power supply chip U2 is grounded, the capacitor C11, the capacitor C12 and the resistor R11 are connected in parallel between the output end of the regulated power supply chip U2 and the secondary ground, and the output end of the regulated power supply chip U2 outputs a secondary 5V direct current power supply.

The beneficial effects of the above-mentioned further scheme are: and the regulated power supply chip U2 is used for performing buck conversion, and then filtering is performed through the capacitor C11, the capacitor C12 and the resistor R11, so that a 5V direct current power supply is output, and the power is supplied to a RS485 communication circuit of the battery management system.

Drawings

Fig. 1 is a schematic structural diagram of a BMS dc power supply circuit of a lithium iron phosphate battery management system according to an embodiment of the present utility model;

FIG. 2 is a schematic diagram of an input rectifying and control circuit according to an embodiment of the present utility model;

FIG. 3 is a schematic diagram of a primary output freewheeling and buck circuit according to an embodiment of the present utility model;

FIG. 4 is a schematic diagram of a DC-DC converter circuit according to an embodiment of the utility model;

fig. 5 is a circuit diagram of a secondary output rectifying and voltage-reducing circuit according to an embodiment of the utility model.

Detailed Description

The principles and features of the present utility model are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the utility model and are not to be construed as limiting the scope of the utility model.

As shown in fig. 1, the BMS DC power supply circuit of the lithium iron phosphate battery management system includes an input rectifying and control circuit, a DC-DC conversion circuit, a primary output freewheeling and voltage reducing circuit, and a secondary output rectifying and voltage reducing circuit, where the input rectifying and control circuit is connected to the battery output voltage, the output ends of the input rectifying and control circuit are electrically connected to the input ends of the DC-DC conversion circuit and the primary output freewheeling and voltage reducing circuit, and the output ends of the DC-DC conversion circuit are electrically connected to the input ends of the primary output freewheeling and voltage reducing circuit and the secondary output rectifying and voltage reducing circuit, and the primary output freewheeling and voltage reducing circuit outputs a primary 12V DC power supply, and the secondary output rectifying and voltage reducing circuit outputs a secondary 5V DC power supply.

According to the lithium iron phosphate battery management system BMS direct current power supply circuit, 48V-70 voltage output by a battery is subjected to rectification, voltage reduction, voltage conversion, rectification, filtering and other treatments through the input rectification and control circuit, the DC-DC conversion circuit and the secondary output rectification and voltage reduction circuit, the output secondary 5V direct current power supply supplies power for the RS485 communication circuit of the battery management system, and meanwhile, the primary 12V direct current power supply is output through the primary output freewheel and voltage reduction circuit to supply power for the control circuit of the battery management system, so that the lithium iron phosphate battery management system BMS direct current power supply circuit has the characteristics of simplicity, low cost, high precision, freewheel output, overvoltage protection, stability, reliability and the like.

In one or more embodiments of the present utility model, as shown in fig. 2, the input rectifying and controlling circuit includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2, a diode D1, a transistor Q2, and a transistor Q3, wherein the positive electrode of the diode D1 is electrically connected to the positive output terminal of the battery, the resistor R2 and the capacitor C1 are sequentially connected in series between the negative electrode of the diode D1 and the primary ground, the resistor R1 is connected in parallel with the resistor R2, the common terminal of the resistor R2 and the capacitor C1 is electrically connected to the emitter of the transistor Q2, the base of the transistor Q2 is electrically connected to the emitter of the transistor Q3 through the resistor R4, the emitter of the transistor Q1 is electrically connected to the negative output terminal of the battery, the negative output terminal of the battery is electrically connected to the primary ground, the transistor Q1 is electrically connected to the output terminal of the transistor Q3 through the emitter of the transistor 3, and the output terminal of the transistor Q3 is electrically connected to the output terminal of the transistor Q3. After the voltage output by the battery is rectified and filtered through the diode D1 and the capacitor C1, the triode Q2 and the triode Q3 are controlled to be conducted in sequence according to the controller and output to the input ends of the DC-DC conversion circuit, the primary output follow current and the voltage reduction circuit, and the resistor R1 and the resistor R2 play a role in input current limiting.

In one or more embodiments of the present utility model, as shown in fig. 3, the primary output freewheeling and buck circuit includes a resistor R6, a resistor R7, a capacitor C3, a diode D3, a zener diode Z1, a zener diode Z2, a transient voltage suppression diode TVS1, a transient voltage suppression diode TVS2, a transistor Q4, and a MOS transistor Q5, wherein an output terminal of the input rectifying and control circuit is electrically connected to a collector of the transistor Q4 through the resistor R7, a collector of the transistor Q4 is electrically connected to a primary ground, a collector of the transistor Q4 is electrically connected to a cathode of the zener diode Z2, an anode of the zener diode Z2 is grounded, an emitter of the transistor Q4 is grounded, a base of the transistor Q4 is electrically connected to an anode of the zener diode Z1 through the resistor R6, a cathode of the transistor Z1 outputs a primary +12v dc power supply, a collector of the transistor Q4 is electrically connected to a drain of the transistor Q5, a collector of the transistor Q1 is electrically connected to a primary input terminal of the transistor Q5, and a drain of the transistor Q5 is electrically connected to a primary ground. The MOS tube Q5 is driven to be conducted by the rectified and filtered battery voltage, and a 12V direct current power supply is output in a step-down mode, so that power is supplied to a battery management system BMS control circuit, after the controller of the battery management system BMS control circuit is electrified, the battery voltage is controlled to be connected to a step-down power supply chip U1 in a DC-DC conversion circuit, after high-frequency step-down DC-DC conversion, the 12V continuous direct current power supply is rectified and output through a diode D3, and the first-stage power supply outputs a follow current function.

As shown in fig. 4, in one or more embodiments of the present utility model, the DC-DC conversion circuit includes a resistor R8, a resistor R9, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a diode D2, a transformer T1, and a buck power chip U1, where an input end of the buck power chip U1 is electrically connected to another output end of the input rectifying and control circuit, a ground terminal of the buck power chip U1 is connected to a primary ground, an output end of the buck power chip U1 is electrically connected to a negative electrode of the diode D2, an anode of the diode D2 is connected to a primary ground, an output end of the buck power chip U1 is electrically connected to one end of a primary coil of the transformer T1, the capacitor C5, the capacitor C6, the capacitor C7, and the capacitor C8 are connected in parallel between the other end of the primary coil of the transformer T1 and the primary ground, a positive electrode of the diode D3 is electrically connected to a ground terminal of the buck power chip, a positive electrode of the buck power chip V12 is connected to the negative electrode of the buck power chip V1 and a feedback circuit is connected to the two ends of the primary winding of the transformer T1, and the feedback circuit is connected to the two ends of the primary winding of the transformer T1 in parallel. The voltage output by the battery is connected to the input end of the step-down power supply chip U1 after input rectification and filtration, the primary winding of the transformer T1, the capacitor C4, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 form a primary working main loop of the self-excited DC-DC conversion circuit to step down and output, meanwhile, the primary winding of the transformer T1, the capacitor C4, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 form an LC resonance circuit, the resonance frequency of the LC resonance circuit corresponds to the working frequency of the step-down power supply chip U1, the higher primary working efficiency of the DC-DC conversion circuit is achieved, the LC filtering function is achieved, and the diode D2 plays a role in preventing the polarity of the output power supply from reversing.

Here, the step-down power supply chip U1 adopts a step-down chip of model XL 7005A.

In one or more embodiments of the present utility model, as shown in fig. 5, the secondary output rectifying and voltage-reducing circuit includes a rectifying and filtering circuit and a voltage-reducing circuit, two input ends of the rectifying and filtering circuit are respectively and electrically connected to two output ends of the DC-DC conversion circuit, an output end of the rectifying and filtering circuit is electrically connected to an input end of the voltage-reducing circuit, and an output end of the voltage-reducing circuit outputs a secondary 5V DC power supply. The rectification and filtering circuit is used for rectifying and filtering the voltage output by the DC-DC conversion circuit, then the voltage is reduced and converted by the voltage reducing circuit, a 5V direct current power supply is output, the power is supplied to the RS485 communication circuit of the battery management system, and the primary output follow current and voltage reducing circuit and the secondary output rectification and voltage reducing circuit are isolated through the transformer T1 and are not affected by each other.

Specifically, as shown in fig. 5, in one or more embodiments of the present utility model, the rectifying and filtering circuit includes a diode D4, a capacitor C9, a capacitor C10, and a resistor R10, where an anode of the diode D4 is electrically connected to one output terminal of the DC-DC conversion circuit, the capacitor C9, the capacitor C10, and the resistor R10 are connected in parallel between a cathode of the diode D4 and the other output terminal of the DC-DC conversion circuit, and the other output terminal of the DC-DC conversion circuit is grounded to a secondary terminal, and a cathode of the diode D4 is electrically connected to the input terminal of the step-down circuit. After the battery voltage is subjected to DC-DC conversion, the secondary winding of the transformer T1 is subjected to rectification and filtering through a diode D4, a capacitor C9, a capacitor C10, a capacitor C11 and a capacitor C12, clutter components in signals are filtered, and the output voltage is smoother.

Specifically, as shown in fig. 5, in one or more embodiments of the present utility model, the voltage reducing circuit includes a regulated power supply chip U2, a capacitor C11, a capacitor C12 and a resistor R11, an input end of the regulated power supply chip U2 is electrically connected to an output end of the rectifying and filtering circuit, a ground end of the regulated power supply chip U2 is grounded, the capacitor C11, the capacitor C12 and the resistor R11 are connected in parallel between the output end of the regulated power supply chip U2 and the secondary ground, and an output end of the regulated power supply chip U2 outputs a secondary 5V dc power supply. And the regulated power supply chip U2 is used for performing buck conversion, and then filtering is performed through the capacitor C11, the capacitor C12 and the resistor R11, so that a 5V direct current power supply is output, and the power is supplied to a RS485 communication circuit of the battery management system.

The BMS direct-current power supply circuit of the lithium iron phosphate battery management system has the following advantages:

1. the self-excited DC-DC conversion circuit formed by the voltage-reducing power supply chip U1 (XL 7005A) and the transformer T1 has the characteristics of reduced cost, improved efficiency, simplicity and high efficiency. XL7005A is a high-frequency step-down DC-DC conversion chip with 150KHZ working frequency and 80V input voltage characteristic;

2. the 1.25V reference of the voltage reduction chip U1 (XL 7005A) adjusts the output voltage value of the power supply through resistor voltage division, so as to achieve the effect of accurate voltage stabilization of the output of the direct current power supply;

3. the primary winding of the transformer and the capacitor form an LC resonant circuit, the resonant frequency of the LC resonant circuit corresponds to the working frequency of the voltage reduction chip U1 (XL 7005A), so that the DC-DC conversion circuit achieves higher working efficiency and plays a role in output LC filtering.

4. The battery voltage is connected, then the bypass MOS tube Q5 is conducted to directly step down and output a 12V direct current power supply to supply power to the control circuit, and meanwhile, after a CPU chip of the control circuit is electrified, the DC-DC conversion circuit is connected to a work output 12V continuous direct current power supply, and the primary power supply outputs a follow current function. When the output voltage exceeds 16V, the bypass MOS transistor Q5 is closed, and the output overvoltage protection function is achieved. The primary output follow current and voltage reduction circuit and the secondary output rectifying and voltage reduction circuit are isolated by the transformer T1, and the primary output follow current and voltage reduction circuit and the secondary output rectifying and voltage reduction circuit are not affected by each other.

5. The circuit has the characteristics of simplicity, low cost, high output precision, follow current output, overvoltage protection, stable power supply and the like.

The direct-current power supply circuit of the lithium iron phosphate battery management system BMS has the characteristics of simplicity, low cost, high precision, stability, reliability and the like, and the circuit technical index meets the technical requirements of the lithium iron phosphate battery management system BMS specified by the state and is widely applied to the actual circuit of the lithium iron phosphate battery management system BMS.

The foregoing description of the preferred embodiments of the utility model is not intended to limit the utility model to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the utility model are intended to be included within the scope of the utility model.

Claims (7)

1. A lithium iron phosphate battery management system BMS direct current power supply circuit is characterized in that: the battery power supply comprises an input rectifying and control circuit, a DC-DC conversion circuit, a primary output follow current and voltage reduction circuit and a secondary output rectifying and voltage reduction circuit, wherein the input rectifying and control circuit is connected with the output voltage of a battery, the output end of the input rectifying and control circuit is respectively and electrically connected with the input ends of the DC-DC conversion circuit and the primary output follow current and voltage reduction circuit, the output end of the DC-DC conversion circuit is respectively and electrically connected with the input ends of the primary output follow current and voltage reduction circuit and the secondary output rectifying and voltage reduction circuit, the primary output follow current and voltage reduction circuit outputs a primary 12V direct current power supply, and the secondary output rectifying and voltage reduction circuit outputs a secondary 5V direct current power supply.

2. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 1, wherein: the input rectifying and controlling circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a capacitor C1, a capacitor C2, a diode D1, a triode Q2 and a triode Q3, wherein the positive electrode of the diode D1 is electrically connected with the positive output end of a battery, the resistor R2 and the capacitor C1 are sequentially connected in series between the negative electrode of the diode D1 and primary ground, the resistor R1 is connected with the resistor R2 in parallel, the common end of the resistor R2 and the capacitor C1 is electrically connected with the emitter of the triode Q2, the base of the triode Q2 is electrically connected with the resistor R3 through the resistor R4, the emitter of the triode Q1 is electrically connected with the collector of the triode Q1, the negative output end of the battery is electrically connected with primary ground, the base of the triode Q1 is electrically connected with the control signal output end of an external controller through the resistor R5, the base of the triode Q2 is electrically connected with the emitter of the triode Q3, the base of the triode Q2 is electrically connected with the collector of the triode Q3, and the input end of the triode Q2 is electrically connected with the DC 3, and the output end of the triode Q2 is electrically connected with the input end of the triode Q3.

3. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 1, wherein: the primary output freewheeling and voltage reducing circuit comprises a resistor R6, a resistor R7, a capacitor C3, a diode D3, a zener diode Z1, a zener diode Z2, a transient voltage suppression diode TVS1, a transient voltage suppression diode TVS2, a triode Q4 and a MOS transistor Q5, wherein one output end of the input rectifying and control circuit is electrically connected with a collector of the triode Q4 through the resistor R7, the capacitor C3 is electrically connected between the collector of the triode Q4 and the primary ground, the collector of the triode Q4 is electrically connected with a cathode of the zener diode Z2, the anode of the zener diode Z2 is grounded in the primary, the emitter of the triode Q4 is grounded in the primary ground, the base of the triode Q4 is electrically connected with the anode of the zener diode Z1 through the resistor R6, the cathode of the triode Z1 is connected with a primary +12V direct current power supply, one output end of the input rectifying and control circuit is electrically connected with the primary ground, the collector of the zener diode Z1 is electrically connected with the primary MOS transistor Q5, and the primary MOS transistor Q4 is electrically connected with the primary voltage of the primary MOS transistor Q5.

4. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 1, wherein: the DC-DC conversion circuit comprises a resistor R8, a resistor R9, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a capacitor C8, a diode D2, a transformer T1 and a step-down power supply chip U1, wherein the input end of the step-down power supply chip U1 is electrically connected with the other output end of the input rectifying and control circuit, the grounding end of the step-down power supply chip U1 is grounded, the output end of the step-down power supply chip U1 is electrically connected with the cathode of the diode D2, the anode of the diode D2 is grounded, the output end of the step-down power supply chip U1 is electrically connected with one end of a primary coil of the transformer T1, the capacitor C5, the capacitor C6, the capacitor C7 and the capacitor C8 are connected in parallel between the other end of the primary coil of the transformer T1 and the primary ground, the cathode of the D3 is electrically connected with the anode of the diode D3, the cathode of the D3 is electrically connected with a primary +12V direct current power supply, the output end of the step-down power supply chip U1 is electrically connected with the two ends of the feedback circuit, and the two ends of the feedback circuit are connected with the two ends of the primary coil of the transformer T1 in parallel.

5. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 1, wherein: the secondary output rectifying and voltage reducing circuit comprises a rectifying and filtering circuit and a voltage reducing circuit, wherein two input ends of the rectifying and filtering circuit are respectively and correspondingly and electrically connected with two output ends of the DC-DC conversion circuit, the output end of the rectifying and filtering circuit is electrically connected with the input end of the voltage reducing circuit, and the output end of the voltage reducing circuit outputs a secondary 5V direct current power supply.

6. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 5, wherein: the rectification filter circuit comprises a diode D4, a capacitor C9, a capacitor C10 and a resistor R10, wherein the positive electrode of the diode D4 is electrically connected with one output end of the DC-DC conversion circuit, the capacitor C9, the capacitor C10 and the resistor R10 are connected in parallel between the negative electrode of the diode D4 and the other output end of the DC-DC conversion circuit, the other output end of the DC-DC conversion circuit is grounded, and the negative electrode of the diode D4 is electrically connected with the input end of the voltage reduction circuit.

7. The lithium iron phosphate battery management system BMS direct current power supply circuit according to claim 5, wherein: the step-down circuit comprises a regulated power supply chip U2, a capacitor C11, a capacitor C12 and a resistor R11, wherein the input end of the regulated power supply chip U2 is electrically connected with the output end of the rectifying and filtering circuit, the grounding end of the regulated power supply chip U2 is grounded, the capacitor C11, the capacitor C12 and the resistor R11 are connected in parallel between the output end of the regulated power supply chip U2 and the secondary ground, and the output end of the regulated power supply chip U2 outputs a secondary 5V direct current power supply.