CN111641237A - Battery pack self-balancing circuit - Google Patents

Abstract

The invention relates to an autonomous balancing circuit of a battery pack, comprising a battery voltage detection circuit, a bidirectional energy storage charging circuit and a controller. The battery voltage detection circuit includes n voltage detection units that are connected with each single battery in one-to-one correspondence; the voltage detection unit includes a voltage detection NMOS tube; the bidirectional energy storage charging circuit includes an energy storage transformer, an energy transfer NMOS tube, and n and each single The charging and discharging units are connected in one-to-one correspondence with the main batteries; the energy storage transformer includes a primary coil and n secondary coils which are arranged in a one-to-one correspondence with each single battery, and the charging and discharging unit includes a charging and discharging PMOS tube; The tube, the energy transfer NMOS tube, and the charge and discharge PMOS tube are connected. The invention can realize the energy transfer without loss, so as to achieve the purpose of battery balance, and has simple structure and high efficiency.

Description

Battery pack self-balancing circuit

technical field

The invention belongs to the field of battery management (BMS), in particular to an autonomous balancing circuit of a battery pack.

Background technique

Lithium batteries (battery packs) are an important part of lithium battery products such as electric vehicles, power tools, and rechargeable vacuum cleaners. How to prolong their service life is a problem that has always plagued lithium battery product developers, and the root cause of this problem is multiple series connection The lower battery is not balanced. For the problem of battery imbalance, corresponding solutions are required.

In the current lithium battery balance design of battery packs, passive balance management methods are mostly adopted. Generally, the batteries with higher voltage are discharged by means of resistance discharge, and the electricity is released in the form of heat, so that the electricity of the whole system is limited by the battery with the least capacity. A battery with a high voltage will be 100% wasted in the form of heat, which is not allowed for a large capacity battery pack. There is also an active equalization scheme based on the capacitance method, that is, a super capacitor is connected in parallel with each battery, and then the capacitor can be connected in parallel to the battery itself or the adjacent battery by switching. When a certain battery is too high, first connect the capacitor in parallel to the battery with high voltage, and then switch the capacitor to the adjacent battery after the capacitor voltage is the same as the battery voltage, and the capacitor charges the battery to realize capacity transfer. Capacitors do not consume energy and can achieve transfer without energy loss. However, this method is complex to control, requires a huge switch array, is difficult to develop, has low efficiency, and the cost of supercapacitors is relatively high.

It can be seen that the problems of the existing battery pack equalization solution are: 1. waste of energy; 2. complex structure; 3. low efficiency. Therefore, it is necessary to design an efficient, simple, and lossless battery pack equalization scheme.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an autonomous balancing circuit of a battery pack that can transfer energy without loss, has a simple structure and has high efficiency.

To achieve the above object, the technical scheme adopted in the present invention is:

An autonomous balancing circuit for a battery pack is connected to a battery pack including n single cells, where n is a positive integer, and the battery pack autonomous balancing circuit includes:

a battery voltage detection circuit, which is used to detect the voltage of each of the single cells; the battery voltage detection circuit includes n voltage detection units connected to each of the single cells in a one-to-one correspondence; the The voltage detection unit includes a voltage detection NMOS tube, the gate of the voltage detection NMOS tube is connected to a detection control signal, the drain of the voltage detection NMOS tube is connected to the positive electrode of the corresponding single battery, and the voltage detection NMOS tube is connected to the positive electrode of the single battery. The source of the NMOS tube outputs a voltage detection signal;

A bidirectional energy storage charging circuit, the bidirectional energy storage charging circuit is used to realize bidirectional energy transfer; the bidirectional energy storage charging circuit includes an energy storage transformer, an energy transfer NMOS tube and n one-to-one connection with each of the single cells The charging and discharging unit; the energy storage transformer includes a primary coil and n secondary coils which are arranged in a one-to-one correspondence with each of the single cells, one end of the primary coil is connected to the positive electrode of the battery pack, and the primary coil is connected to the positive electrode of the battery pack. The other end of the energy transfer NMOS tube is connected to the drain of the energy transfer NMOS tube, the source of the energy transfer NMOS tube is connected to the negative electrode of the battery pack, and the gate of the energy transfer NMOS tube is connected to the energy transfer control signal; the charging The discharge unit includes a charge and discharge PMOS tube, the gate of the charge and discharge PMOS tube is connected to a charge and discharge control signal, the source of the charge and discharge PMOS tube is connected to one end of the corresponding secondary coil, and the charge and discharge The drain of the PMOS tube is connected to the positive electrode of the corresponding single battery, and the negative electrode of the single battery is connected to the other end of the corresponding secondary coil;

a controller, which is configured to control the voltage detection NMOS transistor, the energy transfer NMOS transistor, and the charge/discharge PMOS transistor to balance the voltage of the battery pack according to the voltage control of each of the single cells; the control The controller is connected to the source of each of the voltage detection NMOS tubes for receiving the voltage detection signal; the controller is respectively connected to the gate of each of the voltage detection NMOS tubes and the gate of the energy transfer NMOS tube , The gates of the charge and discharge PMOS transistors are connected to each other, and are used to output the detection control signal, the energy transfer control signal, and the charge and discharge control signal of each channel.

The voltage detection unit further includes a first resistor and a second resistor, the drain of the voltage detection NMOS transistor is connected to the anode of the corresponding single cell through the first resistor, and the gate of the voltage detection NMOS transistor The controller is connected via the second resistor.

The sources of each of the voltage detection NMOS transistors are connected in common and then connected to the controller.

The source of the voltage detection NMOS transistor is grounded through a grounding resistor.

A filter capacitor is connected in parallel with both ends of the grounding resistor.

The bidirectional energy storage charging circuit further includes an electrolytic capacitor, and the electrolytic capacitor is connected in parallel with both ends of the battery pack.

The charging and discharging unit further includes a third resistor and a fourth resistor, the third resistor is connected between the gate and the source of the charging and discharging PMOS tube, and the gate of the charging and discharging PMOS tube passes through the Four resistors connect the controller.

The charging and discharging unit further includes a fuse, and the drain of the charging and discharging PMOS tube is connected to the positive electrode of the single battery through the fuse.

The charging and discharging unit further includes a capacitor connected in parallel to both ends of the single battery.

The method for realizing the balance of the battery pack controlled by the battery pack autonomous balancing circuit is as follows:

The controller obtains the voltage of each of the single cells through each of the voltage detection units of the battery voltage detection circuit, calculates the voltage average value, and then selects the voltage with the largest difference between the voltage and the voltage average value. the single cell and determine that the voltage of the selected single cell is lower or higher than the voltage average value, and if the selected single cell voltage is lower than the voltage average value, perform bottom equalization method, if the voltage of the selected single cell is higher than the average value of the voltage, perform a top equalization method;

The bottom equalization method is as follows: the controller first controls the energy transfer NMOS transistor to be turned on, so that the battery pack charges the primary coil of the energy storage transformer, and then the controller controls the energy transfer NMOS transistor. Turn off, and control the charging and discharging PMOS transistor corresponding to the selected single battery to be turned on, so that the energy on the primary coil of the energy storage transformer is transferred to the selected single battery corresponding to the single battery. on the secondary coil, and charges the selected single cell;

The top equalization method is as follows: the controller first controls the charging and discharging PMOS transistors corresponding to the selected single cells to be turned on, so that the selected single cells are their corresponding secondary coils. After charging, the controller controls the charging and discharging PMOS transistor corresponding to the selected single battery to be turned off, and controls the energy transfer NMOS transistor to be turned on, so that the selected single battery corresponds to the charging and discharging PMOS transistor. The energy on the secondary coil is transferred to the primary coil and charges the battery pack.

Due to the application of the above-mentioned technical solutions, the present invention has the following advantages compared with the prior art: the present invention can realize the transfer of energy without loss, thereby achieving the purpose of battery balance, and has a simple structure and high efficiency.

Description of drawings

FIG. 1 is a schematic diagram of the self-balancing circuit of the battery pack of the present invention.

Detailed ways

The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

Embodiment 1: The battery pack (lithium battery pack) includes n (n is a positive integer greater than or equal to 2) single cells connected in series. The battery pack in this embodiment includes 6 single cells, B1~B6 respectively. . For this battery pack, the following battery pack self-balancing circuit is designed.

The battery pack self-balancing circuit includes a battery voltage detection circuit, a bidirectional energy storage charging circuit and a controller (MCU).

The battery voltage detection circuit is used to detect the voltage of each single cell. The battery voltage detection circuit includes n voltage detection units which are connected with each single battery in a one-to-one correspondence, and each voltage detection unit has the same structure. The voltage detection unit mainly includes a voltage detection NMOS tube, the gate of the voltage detection NMOS tube is connected to the detection control signal, the drain of the voltage detection NMOS tube is connected to the positive pole of the corresponding single battery, and the source output voltage of the voltage detection NMOS tube detection signal. The voltage detection unit further includes a first resistor and a second resistor, the drain of the voltage detection NMOS transistor is connected to the anode of the corresponding single battery through the first resistor, and the gate of the voltage detection NMOS transistor is connected to the controller through the second resistor. In the battery voltage detection circuit, the sources of each voltage detection NMOS transistor can be connected in common and then connected to the controller. After the common connection, the source of the voltage detection NMOS tube is grounded after the grounding resistor, and the two ends of the grounding resistor are connected in parallel with a filter capacitor.

In this embodiment, the voltage detection unit corresponding to the single battery B1 includes a voltage detection NMOS transistor Q1, a first resistor R1, and a second resistor R4. The gate of the voltage detection NMOS transistor Q1 is connected to the second resistor R4 and connected to the detection control signal V1_CHECK, and the drain of the voltage detection NMOS transistor Q1 is connected to the positive electrode of the single battery B1 through the first resistor R1. The voltage detection unit corresponding to the single battery B2 includes a voltage detection NMOS transistor Q3, a first resistor R4, and a second resistor R8. The gate of the voltage detection NMOS transistor Q2 is connected to the second resistor R8 and connected to the detection control signal V2_CHECK, and the drain of the voltage detection NMOS transistor Q2 is connected to the positive electrode of the single battery B2 through the first resistor R5. The voltage detection unit corresponding to the single battery B3 includes a voltage detection NMOS transistor Q5, a first resistor R9, and a second resistor R13. The gate of the voltage detection NMOS transistor Q5 is connected to the second resistor R13 and connected to the detection control signal V3_CHECK, and the drain of the voltage detection NMOS transistor Q5 is connected to the anode of the single battery B3 through the first resistor R9. The voltage detection unit corresponding to the single battery B4 includes a voltage detection NMOS transistor Q7, a first resistor R13, and a second resistor R16. The gate of the voltage detection NMOS transistor Q7 is connected to the second resistor R16 and connected to the detection control signal V4_CHECK, and the drain of the voltage detection NMOS transistor Q7 is connected to the positive electrode of the single battery B4 through the first resistor R13. The voltage detection unit corresponding to the single battery B5 includes a voltage detection NMOS transistor Q9, a first resistor R17, and a second resistor R20. The gate of the voltage detection NMOS transistor Q9 is connected to the second resistor R20 and connected to the detection control signal V5_CHECK, and the drain of the voltage detection NMOS transistor Q9 is connected to the anode of the single battery B5 through the first resistor R17. The voltage detection unit corresponding to the single battery B6 includes a voltage detection NMOS transistor Q12, a first resistor R21, and a second resistor R25. The gate of the voltage detection NMOS transistor Q12 is connected to the second resistor R25 and connected to the detection control signal V6_CHECK, and the drain of the voltage detection NMOS transistor Q12 is connected to the positive electrode of the single battery B6 through the first resistor R21. The source of the voltage detection NMOS transistor Q1, the source of the voltage detection NMOS transistor Q3, the source of the voltage detection NMOS transistor Q5, the source of the voltage detection NMOS transistor Q7, the source of the voltage detection NMOS transistor Q9, the voltage detection NMOS transistor Q12 The sources of BAT_ADC are connected together to form a node BAT_ADC, and the controller connects to this node to obtain a voltage detection signal, which is grounded through a grounding resistor R22, and the two ends of the grounding resistor R22 are connected in parallel with a filter capacitor C7.

The bidirectional energy storage charging circuit is used to realize bidirectional energy transfer. The bidirectional energy storage charging circuit includes an energy storage transformer, an energy transfer NMOS tube, and n charging and discharging units with the same structure that are connected to each single battery in a one-to-one correspondence. The energy storage transformer includes a primary coil and n secondary coils which are arranged in a one-to-one correspondence with each single cell. One end of the primary coil is connected to the positive electrode of the battery pack, the other end of the primary coil is connected to the drain of the energy transfer NMOS tube, the source of the energy transfer NMOS tube is connected to the negative electrode of the battery pack, and the gate of the energy transfer NMOS tube is connected to the energy transfer control signal . The bidirectional energy storage charging circuit also includes an electrolytic capacitor, and the electrolytic capacitor is connected in parallel with both ends of the battery pack.

The charge and discharge unit mainly includes a charge and discharge PMOS tube, the gate of the charge and discharge PMOS tube is connected to the charge and discharge control signal, the source of the charge and discharge PMOS tube is connected to one end of the corresponding secondary coil, and the drain of the charge and discharge PMOS tube is connected to The positive poles of the corresponding single cells are connected to each other, and the negative poles of the single cells are connected to the other ends of the corresponding secondary coils. The charging and discharging unit further includes a third resistor and a fourth resistor, the third resistor is connected between the gate and the source of the charging and discharging PMOS tube, and the gate of the charging and discharging PMOS tube is connected to the controller through the fourth resistor. The charging and discharging unit also includes fuses and capacitors. The drain of the charge and discharge PMOS tube is connected to the positive electrode of the single battery through the fuse, and the capacitor is connected in parallel with both ends of the single battery.

In this embodiment, the energy storage transformer TR1 includes one primary coil and six secondary coils. One end of the primary coil of the energy storage transformer TR1 is connected to the positive electrode B+ of the battery pack, the other end of the primary coil is connected to the drain of the energy transfer NMOS transistor Q11, the source electrode of the energy transfer NMOS transistor Q11 is connected to the negative electrode B- of the battery pack, and the energy transfer NMOS The gate Q11 of the tube is connected to the energy transfer control signal S7.

The charging and discharging unit corresponding to the single battery B1 includes a charging and discharging PMOS transistor Q2, a third resistor R2, a fourth resistor R3, a fuse F1 and a capacitor C1. The source of the charge and discharge PMOS transistor Q2 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS transistor Q2 is connected to the positive electrode of the single battery B1 through the fuse F1, and the negative electrode of the single battery B1 is connected to the corresponding secondary coil. The other end of the third resistor R2 is connected between the gate and the source of the charge and discharge PMOS transistor Q2, the gate of the charge and discharge PMOS transistor Q2 is connected to one end of the fourth resistor R3 to access the energy transfer control signal S1, and the capacitor C1 It is connected in parallel at both ends of the single battery B1. The charging and discharging unit corresponding to the single battery B2 includes a charging and discharging PMOS transistor Q4, a third resistor R6, a fourth resistor R7, a fuse F2 and a capacitor C2. The source of the charge and discharge PMOS tube Q4 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS tube Q4 is connected to the positive pole of the elevator battery B2 through the fuse F2, and the negative pole of the elevator battery B2 is connected to the other side of the corresponding secondary coil. One end, the third resistor R6 is connected between the gate and the source of the charge and discharge PMOS transistor Q4, the gate of the charge and discharge PMOS transistor Q4 is connected to one end of the fourth resistor R7 to access the energy transfer control signal S2, and the capacitor C2 is connected in parallel with Both ends of elevator battery B2. The charging and discharging unit corresponding to the single battery B3 includes a charging and discharging PMOS transistor Q6, a third resistor R10, a fourth resistor R11, a fuse F3 and a capacitor C3. The source of the charge and discharge PMOS transistor Q6 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS transistor Q6 is connected to the positive electrode of the single battery B3 through the fuse F3, and the negative electrode of the single battery B3 is connected to the corresponding secondary coil. The other end of the third resistor R10 is connected between the gate and the source of the charge and discharge PMOS transistor Q6, and the gate of the charge and discharge PMOS transistor Q6 is connected to one end of the fourth resistor R11 to access the energy transfer control signal S3, and the capacitor C3 It is connected in parallel at both ends of the single battery B3. The charging and discharging unit corresponding to the single battery B4 includes a charging and discharging PMOS transistor Q8, a third resistor R14, a fourth resistor R15, a fuse F4 and a capacitor C5. The source of the charge and discharge PMOS transistor Q8 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS transistor Q8 is connected to the positive electrode of the single battery B4 through the fuse F4, and the negative electrode of the single battery B4 is connected to the corresponding secondary coil. The other end of the third resistor R14 is connected between the gate and the source of the charge and discharge PMOS transistor Q8, and the gate of the charge and discharge PMOS transistor Q8 is connected to one end of the fourth resistor R15 to access the energy transfer control signal S4, and the capacitor C5 Connected in parallel at both ends of the single battery B4. The charging and discharging unit corresponding to the single battery B5 includes a charging and discharging PMOS transistor Q10, a third resistor R18, a fourth resistor R19, a fuse F5 and a capacitor C6. The source of the charge and discharge PMOS transistor Q10 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS transistor Q10 is connected to the positive electrode of the single battery B5 through the fuse F5, and the negative electrode of the single battery B5 is connected to the corresponding secondary coil. The other end of the third resistor R18 is connected between the gate and the source of the charge and discharge PMOS transistor Q10, the gate of the charge and discharge PMOS transistor Q10 is connected to one end of the fourth resistor R19 to access the energy transfer control signal S5, the capacitor C6 It is connected in parallel at both ends of the single battery B5. The charging and discharging unit corresponding to the single battery B6 includes a charging and discharging PMOS transistor Q13, a third resistor R23, a fourth resistor R24, a fuse F6 and a capacitor C8. The source of the charge and discharge PMOS transistor Q13 is connected to one end of the corresponding secondary coil, the drain of the charge and discharge PMOS transistor Q13 is connected to the positive electrode of the single battery B6 through the fuse F6, and the negative electrode of the single battery B6 is connected to the corresponding secondary coil. The other end of the third resistor R23 is connected between the gate and the source of the charge and discharge PMOS transistor Q13, the gate of the charge and discharge PMOS transistor Q13 is connected to one end of the fourth resistor R24 to access the energy transfer control signal S6, the capacitor C8 It is connected in parallel at both ends of the single battery B6.

The controller is used to control the voltage detection NMOS tube, the energy transfer NMOS tube, and the charge and discharge PMOS tube respectively to balance the voltage of the battery pack according to the voltage control of each single cell. The controller is connected to the source of each voltage detection NMOS tube for receiving the voltage detection signal; the controller is respectively connected to the gate of each voltage detection NMOS tube, the gate of the energy transfer NMOS tube, and the gate of each charge and discharge PMOS tube are connected to each other, and are used to output various detection control signals, energy transfer control signals, and charge and discharge control signals.

In the above scheme, the battery voltage detection circuit mainly uses the voltage division principle to detect. When the voltage of a single battery needs to be detected, it is only necessary to set the gate of the corresponding voltage detection NMOS tube to a high level, and then the NMOS can be detected in the voltage. The source of the tube, that is, a voltage on the mountain at BAT_ADC, the ADC port of the controller can calculate the voltage of the single battery by reading the voltage of BAT_ADC. The filter capacitor C7 connected in parallel at BAT_ADC can effectively filter out clutter and improve the detection accuracy.

The bidirectional energy storage charging circuit is a flyback power supply circuit, in which the electrolytic capacitor C5 is connected in parallel with the battery pack to play the role of energy storage filtering. When the battery pack needs to be charged or discharged, it is only necessary to turn on the corresponding charge and discharge PMOS tube.

The method of battery pack self-balancing circuit control to achieve battery pack balance is:

The controller scans each single cell, obtains the voltage of each single cell through each voltage detection unit of the battery voltage detection circuit, calculates the voltage average value, and then selects the single cell with the largest difference between the voltage and the voltage average value. Bx and judge that the voltage of the selected single battery Bx is lower or higher than the voltage average value. If the voltage of the selected single battery Bx is lower than the voltage average value, the voltage of the single battery Bx must be increased. In the bottom equalization method, if the voltage of the selected single cell is higher than the voltage average value, the voltage of the single cell Bx must be lowered, and then the top equalization method is performed.

The bottom equalization method is as follows: the controller first controls the energy transfer NMOS transistor Q11 to turn on, so that the battery pack charges the primary coil of the energy storage transformer TR1, and then the controller controls the energy transfer NMOS transistor Q11 to turn off, and controls the selected single battery. The charge and discharge PMOS transistor corresponding to Bx is turned on, so that the energy on the primary coil of the energy storage transformer TR1 is transferred to the secondary coil corresponding to the selected single battery Bx, and the selected single battery Bx is charged. In application, the switching frequency of the energy transfer NMOS transistor Q11 should be above 25KHZ to avoid whistling noise in the energy storage transformer TR1. This cycle of control until all single cell voltages reach the equilibrium target.

For example, if the difference between the voltage of the single battery B3 and the average voltage is the largest and lower than the average voltage, the single battery B3 needs to be charged. First, the energy transfer NMOS transistor Q11 is controlled to be turned on, so that the battery pack charges the primary coil of the energy storage transformer TR1, and then the energy transfer NMOS transistor Q11 is controlled to be turned off, and the charge and discharge PMOS transistor Q6 corresponding to the single battery B3 is controlled to be turned on, so that the The energy on the primary coil of the energy storage transformer TR1 is transferred to the secondary coil corresponding to the unit battery B3 and charges the unit battery B3. This cycle of control until all single cell voltages reach the equilibrium target.

The top equalization method is as follows: the controller first controls the charging and discharging PMOS tube corresponding to the selected single battery Bx to conduct, so that the selected single battery Bx is charged to its corresponding secondary coil, and then the controller controls the selected single battery Bx. The charge and discharge PMOS tube corresponding to the bulk battery Bx is turned off, and the energy transfer NMOS tube Q11 is controlled to be turned on, so that the energy on the secondary coil corresponding to the selected single battery Bx is transferred to the primary coil and charges the battery pack.

For example, if the difference between the voltage of the unit cell B2 and the average voltage value is the largest and higher than the average value of the voltage, the unit battery B2 needs to be discharged. First, control the charging and discharging PMOS transistor Q4 corresponding to the single battery B2 to conduct, and the current flows from the single battery B2 to the secondary coil of the energy storage transformer TR1, so that the single battery B2 is charged to its corresponding secondary coil. Due to the existence of the self-inductance, the current increases linearly with time. Since the self-inductance is an inherent characteristic of the transformer, the conduction time of the charge and discharge PMOS transistor Q4 will determine the magnitude of the current, and the energy transferred from the single battery B2 is in the form of a magnetic field. get stored. Then control the charge and discharge PMOS transistor Q4 corresponding to the single battery B2 to turn off, and control the energy transfer NMOS transistor Q11 to turn on, so that the energy on the secondary coil corresponding to the single battery B2 is transferred to the primary coil, and the battery pack is charged. . This cycle of control until all battery voltages reach the equilibrium target.

The above-mentioned battery pack self-balancing circuit uses the transformer as the carrier of energy transfer, and does not consume energy during the period, so that the entire battery pack can achieve self-balancing, the entire circuit structure is simple, and the transfer efficiency is high.

The above-mentioned embodiments are only intended to illustrate the technical concept and characteristics of the present invention, and the purpose thereof is to enable those who are familiar with the art to understand the content of the present invention and implement them accordingly, and cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included within the protection scope of the present invention.

Claims (10)

1. The utility model provides a group battery is equalizer circuit independently, is connected with the group battery that includes n battery cell, and n is positive integer, its characterized in that: the battery pack autonomous equalization circuit comprises:

a battery voltage detection circuit for detecting a voltage of each of the unit batteries; the battery voltage detection circuit comprises n voltage detection units which are connected with the single batteries in a one-to-one correspondence manner; the voltage detection unit comprises a voltage detection NMOS tube, a grid electrode of the voltage detection NMOS tube is connected with a detection control signal, a drain electrode of the voltage detection NMOS tube is connected with a positive electrode of the single battery corresponding to the voltage detection NMOS tube, and a source electrode of the voltage detection NMOS tube outputs a voltage detection signal;

a bidirectional energy storage charging circuit for achieving bidirectional energy transfer; the bidirectional energy storage charging circuit comprises an energy storage transformer, an energy transfer NMOS (N-channel metal oxide semiconductor) tube and n charging and discharging units which are connected with the single batteries in a one-to-one correspondence manner; the energy storage transformer comprises a primary coil and n secondary coils which are arranged in one-to-one correspondence with the single batteries, one end of the primary coil is connected with the positive electrode of the battery pack, the other end of the primary coil is connected with the drain electrode of the energy transfer NMOS tube, the source electrode of the energy transfer NMOS tube is connected with the negative electrode of the battery pack, and the grid electrode of the energy transfer NMOS tube is connected with an energy transfer control signal; the charging and discharging unit comprises a charging and discharging PMOS tube, a grid electrode of the charging and discharging PMOS tube is connected with a charging and discharging control signal, a source electrode of the charging and discharging PMOS tube is connected with one end of the corresponding secondary coil, a drain electrode of the charging and discharging PMOS tube is connected with the anode of the corresponding single battery, and the cathode of the single battery is connected with the other end of the corresponding secondary coil;

the controller is used for controlling the voltage detection NMOS tube, the energy transfer NMOS tube and the charge and discharge PMOS tube respectively according to the voltage control of each single battery to balance the voltage of the battery pack; the controller is connected with the source electrode of each voltage detection NMOS tube and is used for receiving the voltage detection signal; the controller is respectively connected with the grid electrode of each voltage detection NMOS tube, the grid electrode of the energy transfer NMOS tube and the grid electrode of each charge-discharge PMOS tube and is used for outputting each detection control signal, each energy transfer control signal and each charge-discharge control signal.

2. The battery pack autonomous equalization circuit of claim 1, wherein: the voltage detection unit further comprises a first resistor and a second resistor, the drain electrode of the voltage detection NMOS tube is connected with the corresponding anode of the single battery through the first resistor, and the grid electrode of the voltage detection NMOS tube is connected with the controller through the second resistor.

3. The battery pack autonomous equalization circuit of claim 1, wherein: and the source electrodes of the voltage detection NMOS tubes are connected with the controller after being connected in common.

4. The battery pack autonomous equalization circuit of claim 3, wherein: and the source electrode of the voltage detection NMOS tube is grounded through a grounding resistor.

5. The battery pack autonomous equalization circuit of claim 4, wherein: and two ends of the grounding resistor are connected with a filter capacitor in parallel.

6. The battery pack autonomous equalization circuit of claim 1, wherein: the bidirectional energy storage charging circuit further comprises an electrolytic capacitor, and the electrolytic capacitor is connected in parallel to two ends of the battery pack.

7. The battery pack autonomous equalization circuit of claim 1, wherein: the charging and discharging unit further comprises a third resistor and a fourth resistor, the third resistor is connected between the grid electrode and the source electrode of the charging and discharging PMOS tube, and the grid electrode of the charging and discharging PMOS tube is connected with the controller through the fourth resistor.

8. The battery pack autonomous equalization circuit of claim 1, wherein: the charge and discharge unit further comprises a fuse, and the drain electrode of the charge and discharge PMOS tube is connected with the anode of the single battery through the fuse.

9. The battery pack autonomous equalization circuit of claim 1, wherein: the charge and discharge unit further comprises a capacitor connected in parallel at two ends of the single battery.

10. The battery pack autonomous equalization circuit of claim 1, wherein: the method for realizing the battery pack balance by the battery pack autonomous balancing circuit comprises the following steps:

the controller obtains the voltage of each single battery through each voltage detection unit of the battery voltage detection circuit and calculates a voltage average value, then selects the single battery with the largest difference value between the voltage and the voltage average value and judges that the voltage of the selected single battery is lower than or higher than the voltage average value, if the voltage of the selected single battery is lower than the voltage average value, a bottom equalization method is executed, and if the voltage of the selected single battery is higher than the voltage average value, a top equalization method is executed;

the bottom equalization method comprises the following steps: the controller firstly controls the energy transfer NMOS tube to be conducted so that the battery pack charges the primary coil of the energy storage transformer, then controls the energy transfer NMOS tube to be turned off, controls the charging and discharging PMOS tube corresponding to the selected single battery to be conducted, transfers the energy on the primary coil of the energy storage transformer to the secondary coil corresponding to the selected single battery, and charges the selected single battery;

the top equalization method comprises the following steps: the controller controls the conduction of the charging and discharging PMOS tubes corresponding to the selected single batteries to enable the selected single batteries to charge the secondary coils corresponding to the single batteries, then controls the disconnection of the charging and discharging PMOS tubes corresponding to the selected single batteries and controls the conduction of the energy transfer NMOS tubes to enable the energy on the secondary coils corresponding to the selected single batteries to be transferred to the primary coils and charge the battery pack.

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