CN103532197B - Based on power battery equalization circuit and the implementation method of boosting inverter and Sofe Switch - Google Patents

Abstract

The invention discloses a power battery pack equalization circuit based on boost conversion and soft switching and its realization method. The equalization circuit mainly includes a microcontroller, a switch module, a BOOST boost conversion module and an LC resonant circuit. The battery cell number corresponding to the cell voltage and the lowest cell voltage, gate the battery cell with the highest and lowest voltage anywhere in the battery pack to the balance bus; at the same time, the microcontroller sends a pair of PWM signals with complementary states to control LC resonant circuit makes it work alternately in charging and discharging states. The invention effectively overcomes the problem that it is difficult to realize the zero voltage difference of battery cells due to the conduction voltage drop of the power electronic device; increases the equalization current and reduces the equalization time; realizes zero current switch equalization and reduces energy waste; It effectively improves the inconsistency between battery cells and improves the equalization efficiency.

Description

Power battery pack equalization circuit and implementation method based on boost conversion and soft switching

technical field

The invention relates to a new energy vehicle power control technology, in particular to a power battery pack equalization circuit based on boost conversion and soft switching and an implementation method.

Background technique

At present, lithium-ion batteries are widely used in pure electric vehicles, hybrid electric vehicles, electric motorcycles and UPS uninterruptible power supplies due to their high energy density and low self-discharge rate. Since the voltage of lithium-ion battery cells is only 2.5-3.6V, in order to meet the power drive requirements of electric vehicles, it is generally necessary to use battery cells in series to increase the voltage level. However, during the production process of the battery cell, due to the process and other reasons, there are differences in the capacity and internal resistance of the same batch of batteries; It can also cause an imbalance in battery capacity. Therefore, during the charging and discharging process of the power battery, the voltage of some monomers will be high, and the voltage of some monomers will be low. If the power battery is in this inconsistent state for a long time, it will not only affect the service life of the battery, but also easily cause battery damage and even explosion. In order to eliminate the unevenness of the battery cells, the battery needs to be balanced. At present, there are mainly two types of equilibrium: energy dissipative and energy non-dissipative.

The energy dissipation type achieves balance by connecting a resistor in parallel to each single battery in the battery pack to perform discharge shunting. Energy non-dissipative circuits use capacitors and inductors as energy storage elements, use common power conversion circuits as topological foundations, and adopt decentralized or centralized structures to realize unidirectional or bidirectional charging schemes.

The structure of the energy dissipation circuit is simple, and a resistor is connected in parallel to each single battery in the battery pack to perform discharge shunting, so as to achieve balance, and there are problems of energy waste and thermal management. Energy non-dissipative circuits use capacitors and inductors as energy storage elements, use common power conversion circuits as topological basis, and adopt decentralized or centralized structures to realize one-way or two-way charging schemes. There are complex circuit structures, large volumes, and cost High, long equalization time, high switching loss and other disadvantages.

Chinese invention patent application (Application No. 201010572115.X) discloses a circuit for balancing battery cells in a battery pack by using balancing resistors, which mainly includes a controller, a resistor switching circuit and a balancing resistor. The invention firstly determines the remaining power of each battery cell according to the collected voltage value, and then controls the resistance switching circuit to connect the balance resistor in parallel with the battery cell with higher power to discharge the battery cell, thereby realizing the battery cell power balance . In essence, this circuit limits the high voltage of the battery cell through energy consumption, which is only suitable for static equalization, and there are problems of energy waste and heat management.

Chinese invention patent application (Application No. 201210595724.6) proposes a capacitive battery equalization circuit. In this circuit, two adjacent batteries share a capacitor. When the capacitor is connected in parallel with a battery cell with a higher voltage, the battery charges the capacitor; When a capacitor is connected in parallel with a lower voltage cell, the capacitor charges the battery. After the capacitor is charged and discharged, energy is transferred from the battery cell with higher voltage to the battery cell with lower voltage, so that its voltage is equal. However, when the number of battery cells in series is large, the required balancing capacitors and field effect transistors and their driving circuits are large, resulting in a large circuit size, and when the batteries with the highest and lowest voltages are adjacent to multiple cells, this " The equalization method of drumming and passing flowers will greatly reduce the equalization efficiency.

Chinese invention patent application (application number 201310278475.2) proposes a power battery zero-current switch active equalization circuit and its implementation method, which can judge the highest and lowest voltage battery cells in the battery pack in real time, and perform zero-current switch equalization on them. And each equalization is for the two battery cells with the largest voltage difference in the battery pack to perform peak shaving and valley filling, which greatly improves the equalization efficiency and effectively reduces the inconsistency between the battery cells. However, due to the conduction voltage drop of the used power electronic devices, it is difficult to achieve zero voltage difference between battery cells, and the equalization current is very small, and the equalization time is long.

The open circuit voltage of a lithium-ion battery is relatively flat when the SOC is between 30% and 70% (SOC is the state of charge of the battery, and when SOC=100%, it means that the battery is fully charged), even if the SOC differs greatly, its corresponding The voltage difference is also very small, so the traditional equalization method balances the current is small, and because of the conduction voltage drop of the power electronic device, it is difficult to achieve zero voltage difference between the battery cells, and because the power electronic device works in a hard switch state , the switching loss is high.

Contents of the invention

The purpose of the present invention is to solve the above problems, and propose a power battery pack equalization circuit based on boost conversion and soft switching and its implementation method. The equalization circuit can realize zero current switch equalization current and overcome the voltage difference between battery cells problems, reduce energy waste, and improve balance efficiency.

In order to achieve the above object, the present invention adopts the following technical solutions:

A power battery pack equalization circuit based on boost conversion and soft switching, including a microcontroller, a switch module, a BOOST boost conversion module and an LC resonant circuit, and the microcontroller is connected to the switch module, the LC resonant circuit and the BOOST boost conversion module , the BOOST step-up conversion module is connected to the LC resonant circuit, and the LC resonant circuit is connected to the switch module through the balanced bus; wherein,

The microcontroller includes an analog-to-digital conversion module, a drive circuit and a general-purpose IO terminal;

The analog-to-digital conversion module is connected to the battery cell and the BOOST step-up conversion module, and is used to convert the voltage signal of the battery cell into a digital signal, thereby determining the battery cell with the highest and lowest voltage;

The pulse width modulation PWM signal output end of the drive circuit is connected to the BOOST step-up conversion module for generating a control drive signal;

The general-purpose IO terminal is connected to the switch module, and is used to decode the battery number corresponding to the highest cell voltage and the lowest cell voltage determined by the microcontroller, and the switch module controls the battery cell with the highest and lowest voltage at any position in the battery pack Body gated to the EQ bus.

The BOOST step-up conversion module includes an inductor L _b , a MOS transistor M _b , a diode D _b and a large capacitor C _b .

The LC resonant circuit includes four MOS transistors, _four diodes and an LC circuit, wherein MOS transistors M1 and _M2 are driven by _one PWM ₊ signal, and MOS transistors M3 and M4 are driven by another PWM- signal whose state is reversed drive, the diodes D ₁ -D ₄ play the role of reverse current limiting.

The balanced bus includes a balanced bus I and a balanced bus II, the switch module includes a switch module I and a switch module II, the balanced bus I is connected to the BOOST boost conversion module and the switch module I; the balanced bus II is connected to the switch module II and the LC resonance circuit.

The LC resonant circuit alternately changes between two states of charging and discharging under the drive of two complementary PWM signals.

The charging state is that the LC resonant circuit is connected in parallel with the BOOST step-up conversion module.

The discharge state is that the LC resonant circuit is connected in parallel with the battery cell with the lowest voltage.

When the frequency of the PWM signal is equal to the natural resonant frequency of the LC resonant circuit, the equalizing circuit performs zero-current switching equalization on the two battery cells with the largest voltage difference in the battery pack.

A method for implementing the above-mentioned power battery equalization circuit based on boost conversion and soft switching, comprising the following steps:

(1) Obtain the voltage of the single cell: the microcontroller obtains the voltage of each single cell of the power battery by means of the analog-to-digital conversion module, so as to determine the highest single cell voltage and the lowest single cell voltage and the corresponding battery cell number;

(2) Judgment voltage: The microcontroller calculates the maximum cell voltage difference based on the obtained highest and lowest battery cell voltages. If the difference is greater than the battery equalization threshold, the equalization circuit is activated;

(3) Strobe battery: The microcontroller decodes the battery cell numbers corresponding to the highest cell voltage and the lowest cell voltage through the decoding circuit, and the control switch module decodes the battery cell numbers corresponding to the highest cell voltage and the lowest cell voltage. body strobe to the equalization bus;

(4) Energy transfer: the microcontroller controls the BOOST boost conversion module to boost the voltage of the battery cell with the highest voltage to a higher voltage, and at the same time controls the LC resonant circuit to work alternately in the charging and discharging states, thereby realizing The constant delivery of energy.

In the step (4), when the LC resonant circuit is connected in parallel with the BOOST boost conversion module, the BOOST boost conversion module charges the LC resonant circuit, and when the LC resonant circuit is connected in parallel with the battery cell with the lowest voltage, the LC resonant circuit charges The charging of the battery cell, along with the charge and discharge of the LC resonant circuit, realizes the transfer of energy from the battery cell with higher voltage to the battery cell with lower voltage.

Working principle of the present invention is:

According to the battery cell number corresponding to the highest cell voltage and the lowest cell voltage, the microcontroller controls the switch module through the decoding of the general IO terminal, and selects the battery cell with the highest and lowest voltage anywhere in the battery pack to the balance bus Then, the microcontroller controls the BOOST step-up conversion module to boost the voltage of the battery cell with the highest voltage to a higher voltage, which overcomes the difficulty in realizing the zero voltage difference of the battery cell due to the conduction voltage drop of the power electronic device. The problem; at the same time, the microcontroller sends a pair of state-complementary PWM signals to control the LC resonant circuit, making it alternately work in two states of charging and discharging. In particular, when the PWM frequency sent by the microcontroller is equal to the natural resonant frequency of the LC resonant circuit, zero-current switch equalization can be achieved, and each equalization is performed on the two battery cells with the largest voltage difference in the battery pack. Filling the valley greatly improves the balance efficiency.

The beneficial effects of the present invention are:

(1) Effectively overcome the problem that it is difficult to achieve zero voltage difference of battery cells due to the conduction voltage drop of power electronic devices;

(2) Increased equalization current and reduced equalization time;

(3) Realize zero-current switching balance and reduce energy waste;

(4) The inconsistency between battery cells is effectively improved, and the equalization efficiency is improved.

Description of drawings

Fig. 1 is the composition schematic diagram of the present invention;

Fig. 2 is the working principle diagram of LC resonant circuit charging of the present invention;

Fig. 3 is the LC resonant circuit discharge working principle diagram of the present invention;

Fig. 4 is the charge-discharge current waveform diagram of the present invention;

Fig. 5 is an equilibrium effect diagram of the power battery of the present invention in a static state;

Fig. 6 is an equilibrium efficiency diagram of the power battery of the present invention in a static state.

Among them, 1. Switch module I; 2. Balance bus II; 3. Battery monomer; 4. Balance bus I; 5. Microcontroller; 6. BOOST step-up conversion module; 7. LC resonant circuit; 8. Drive circuit ; 9. Multi-channel strobe switch; 10. Voltage detection circuit; 11. Switch module II.

detailed description:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a power battery pack equalization circuit based on boost conversion and soft switching includes a microcontroller 5, a switch module, a BOOST boost conversion module 6 and an LC resonant circuit 7, and the microcontroller 5 is connected to the switch module , LC resonant circuit 7 and BOOST step-up conversion module 6, BOOST step-up conversion module 6 is connected to LC resonant circuit 7, and LC resonant circuit 7 is connected to switch module II11 through a balanced bus; wherein,

The microcontroller 5 includes an analog-to-digital conversion module, a drive circuit 8 and a general-purpose IO end;

The analog-to-digital conversion module is used to convert the voltage signal of the battery cell 3 into a digital signal, thereby determining the battery cell 3 with the highest and lowest voltage;

The pulse width modulation PWM signal output terminal of the drive circuit 8 is connected to the BOOST step-up conversion module 6 for generating a control drive signal;

The general-purpose IO terminal is connected to the switch module for decoding the number of the battery cell 3 corresponding to the highest cell voltage and the lowest cell voltage determined by the microcontroller 5, and the control switch module converts the highest and lowest voltage of any position in the battery pack The battery cell 3 is gated to the balance bus.

The BOOST boost conversion module 6 includes an inductor L _b , a MOS transistor M _b , a diode D _b and a large capacitor C _b . The BOOST boost conversion module 6 is used to output a higher voltage to achieve large current balance and zero voltage difference between the battery cells 3. Specifically, the microcontroller 5 sends a PWM signal to drive the BOOST boost conversion module 6. MOS tube, and adopt the closed-loop PID control method to adjust the duty cycle of the PWM, so that the BOOST step-up conversion module 6 outputs a stable and higher voltage.

The balanced bus includes a balanced bus I4 and a balanced bus II2, and the switch module includes a switch module I1 and a switch module II11. The balanced bus I4 is connected to the BOOST step-up conversion module 6 and the switch module I1;

LC resonant circuit 7 includes four MOS transistors, _four diodes and an LC circuit, wherein MOS transistors M1 and _M2 are driven by _one PWM ₊ signal, M3 and M4 are driven by another PWM- signal whose state is reversed, and the diode D ₁ -D ₄ play the role of reverse current limiting. Driven by the pair of complementary PWM signals, the LC resonant circuit 7 alternately works in two states of charging and discharging. Charging is connected in parallel with the BOOST step-up conversion module 6 connected to the balanced bus I4, and discharged is connected to the connected and balanced bus II2. The battery cells 3 with the lowest voltage connected are connected in parallel. In particular, when the frequency of the PWM signal sent by the microcontroller 5 is equal to the natural resonant frequency of the LC resonant circuit 7, zero-current switch equalization is realized, and each equalization is aimed at the two battery cells 3 with the largest voltage difference in the battery pack The equalization efficiency is greatly improved, and at the same time, the inconsistency between the battery cells 3 is effectively improved by means of the BOOST boost conversion module 6 .

A method for implementing the above-mentioned power battery equalization circuit based on boost conversion and soft switching, comprising the following steps:

(1) Obtain the voltage of the battery cell 3: the microcontroller 5 obtains the voltage of each cell of the power battery by means of the analog-to-digital conversion module, so as to determine the highest cell voltage and the lowest cell voltage and the corresponding battery cell 3 number;

(2) Judging the voltage: the microcontroller 5 calculates the maximum cell voltage difference based on the obtained highest and minimum battery cell voltages, and starts the balancing circuit if the difference is greater than the battery balancing threshold;

(3) Strobe battery: the number of the battery cell 3 corresponding to the highest cell voltage and the lowest cell voltage determined by the microcontroller 5 through the decoding circuit, and the control switch module selects the battery cell number corresponding to the highest cell voltage and the lowest cell voltage The monomer is strobed to the balanced bus;

(4) Energy transfer: the microcontroller 5 controls the BOOST step-up conversion module 6 to boost the voltage of the battery cell 3 with the highest voltage to a higher voltage, and at the same time controls the LC resonant circuit 7 to make it work alternately between charging and discharging. State, so as to realize the continuous transfer of energy.

In step (4), when the LC resonant circuit 7 is connected in parallel with the BOOST step-up conversion module 6, the BOOST step-up conversion module 6 charges the LC resonant circuit 7, and when the LC resonant circuit 7 is connected in parallel with the battery cell 3 with the lowest voltage, The LC resonant circuit 7 charges the battery cells 3 , and with the charging and discharging of the LC resonant circuit 7 , the energy is transferred from the battery cells 3 with higher voltage to the battery cells 3 with lower voltage.

Embodiment one:

Take 6 battery cells 3 as an example, and assume that B ₁ is the battery cell 3 with the highest voltage, and B ₄ is the battery cell 3 with the lowest voltage.

The microcontroller 5 of the equalization circuit uses digital signal processing DSP (TMS320F28335), which has high-precision AD sampling and PWM output; the multi-channel strobe switch 9 uses CD4051, which is a single 8-channel digital control analog electronic switch with A, B and C Three binary control inputs and There are 4 inputs in total, with low on-resistance and very low cut-off leakage current; the voltage detection circuit 10 uses Linear Technology's LTC6802 dedicated voltage measurement chip to measure the voltage of each battery in the battery pack in real time.

Switch module I1 and switch module II11 use relays with a pair of normally open contacts, the model of which is HJR1-2CL-05V, in Figure 1 (S _x , Q _x ) or (S′ _x , Q′ _x ) is a pair Normally open switch. Microcontroller 5 controls its conduction or closure through a multiplex strobe switch 9CD4051.

The BOOST step-up conversion module 6 is composed of an inductor L _b , a MOS transistor M _b , a diode D _b and a large capacitor C _b . The BOOST boost conversion module 6 mainly works in two states of charging and discharging: when the MOS tube is turned on, the battery cell 3 starts to charge the inductor L _b , and as the inductor current increases, the energy stored in the inductor increases; when the MOS transistor When the tube M _b is disconnected, the battery and the inductor L _b start to discharge the capacitor through the diode D _b , and the voltage across the capacitor rises, and the voltage is higher than the input voltage at this time. In short, the boost process is an energy transfer process of an inductor. When charging, the inductor absorbs energy, and when discharging, the inductor releases energy. If the capacitance is large enough, a continuous current can be maintained at the output during discharge. The size of the output voltage of the BOOST boost conversion module 6 can be adjusted by controlling the duty cycle of the conduction of the MOS tube. The present invention uses a closed-loop PID controller to control the duty cycle of the conduction of the MOS tube to keep the output voltage of the BOOST boost conversion module 6 at Around 7.5V.

The LC resonant circuit 7 is composed of four MOS transistors M ₁ -M ₄ , four diodes D ₁ -D ₄ and an inductor L and a capacitor C circuit. Among them, M ₁ , M ₂ , D ₁ , D ₂ and L and C form a charging circuit; M ₃ , M ₄ , D ₃ , D ₄ and L and C form a discharging circuit. _The source of M1 and the negative pole of D2 are respectively connected to the positive and negative poles of capacitor _Cb in the BOOST step-up conversion module _{6 ;} the negative pole of _D3 and the source of M4 are respectively connected to the positive and negative poles of the balanced bus II2. Diodes D ₁ -D ₄ function as isolation. MOS transistors M ₁ -M ₄ are driven by a pair of complementary PWM signals from the microcontroller 5DSP, where M ₁ and M ₂ are driven by one PWM+ signal, and M ₃ and M ₄ are driven by another complementary PWM- signal . When M ₁ and M ₂ are turned on, and M ₃ and M ₄ are turned off, the LC resonant circuit and 7 work in a charging state; when M ₃ and M ₄ are turned on, and M ₁ and M ₂ are turned off, the LC resonant circuit 7 Work in discharge state. In this way, energy can be transferred from the battery cell 3 with the highest voltage to the battery cell 3 with the lowest voltage through the continuous charging and discharging of the LC resonant circuit 7, especially when the PWM frequency sent by the microcontroller 5 is equal to that of the LC quasi-resonant circuit When the natural resonant frequency of 7 is achieved, zero current switching equalization is achieved.

First, the microcontroller 5 obtains the voltage of each cell of the power battery by means of the analog-to-digital conversion module, thereby determining the highest cell voltage, the lowest cell voltage and the corresponding battery cell 3 number, and judging whether the maximum voltage difference is greater than the battery equalization threshold , if it is greater than , start the equalization circuit, and pass the decoding chip CD4051 to select the (S′ ₂ , Q′ ₂ ) of the switch module I1 and the (S ₅ , Q ₅ ) of the switch module II11 and keep it in the conduction state until this time After the equalization is completed, the battery cell B ₁ with the highest voltage and the battery cell B ₄ with the lowest voltage are gated to the equalization bus I4 and the equalization bus II2 respectively.

In the balanced state, the microcontroller 5 is controlled by a PID controller, and the BOOST step-up conversion module 6 boosts the voltage of the battery cell B ₁ with the highest voltage to about 7.5V.

At the same time, the LC resonant circuit 7 is controlled to work alternately in two states of charging and discharging, so as to realize the continuous transfer of energy.

As shown in FIG. 2 , when M ₁ and M ₂ are turned on, M ₃ and M ₄ are turned off, and the LC resonant circuit 7 is connected in parallel with the BOOST step-up conversion module 6 . C _b , inductance L and capacitor C form a resonant circuit. At this time, when charging, the resonant current i is positive, and the voltage V _c across the capacitor C begins to rise until the resonant current i becomes negative. It can be seen from Figure 3 that V _c The lagging resonant current i is a quarter cycle, and the waveforms are all sine waves. _At this moment, since M3 and M4 are in the off state and the battery cell B4 is open, the current i _B4 flowing into B4 is zero; and because the microcontroller ₅ controls the output voltage of the BOOST step _- up conversion module ₆ to stabilize at 7.5 V is about V, so the resonant current i flowing into the LC is the current flowing out _of the battery cell B1, and it is specified that the current is positive when the current flows out of the battery cell, so B1 and B4 shown in state _I as shown in Figure ₄ can be obtained current waveform.

As shown in Figure ₃ , when M3 and M4 are turned _on , M1 and _M2 are turned off, and the LC resonant circuit ₇ is connected in parallel with the lowest voltage battery cell B4 through the switch module I1 and the switch module II11 _. B ₄ , L and C form a resonant circuit. When discharging at this time, the resonant current i is negative, and the voltage V _c across the capacitor C begins to drop until the resonant current becomes positive. Because the BOOST boost conversion module 6 is in an open circuit state, the current i _B1 flowing out of the battery cell B ₁ is zero; at the same time, the resonant current i is the charging current of B ₄ at this moment, so the B shown in state II in Figure 4 can be obtained ₁ and B ₄ current waveforms.

As shown in Figure 5 and Figure 6, when the initial voltage of the battery cell is B ₀ =3.098V, B ₁ =3.112V, B ₂ =3.079V, B ₃ =2.975V, B ₄ =3.036V, B ₅ = 3.083V, B ₆ =3.1V, B ₇ =2.853V, it only takes about 3000s for the equalization circuit to make the maximum voltage difference of the battery cells in the battery pack close to 0, and the measured equalization efficiency is as high as 98.6%.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (7)

1. A power battery pack equalization circuit based on boost conversion and soft switching is characterized in that: the BOOST BOOST conversion circuit comprises a microcontroller, a switch module, a BOOST BOOST conversion module and an LC resonance circuit, wherein the microcontroller is connected with the switch module, the LC resonance circuit and the BOOST BOOST conversion module; wherein,

the microcontroller comprises an analog-to-digital conversion module, a driving circuit and a general IO end;

the analog-to-digital conversion module is connected with the single battery and the BOOST conversion module and is used for converting voltage signals of the single battery into digital signals so as to determine the single battery with the highest voltage and the lowest voltage;

the Pulse Width Modulation (PWM) signal output end of the driving circuit is connected with a BOOST conversion module and used for generating a control driving signal;

the general IO end is connected with the switch module and used for decoding battery numbers corresponding to the highest monomer voltage and the lowest monomer voltage determined by the microcontroller and controlling the switch module to gate the battery monomers with the highest voltage and the lowest voltage at any position in the battery pack to the balance bus;

the balanced bus comprises a balanced bus I and a balanced bus II, the switch module comprises a switch module I and a switch module II, and the balanced bus I is connected with the BOOST conversion module and the switch module I; the equalizing bus II is connected with the switch module II and the LC resonant circuit;

the LC resonance circuit comprises four MOS tubes M₁、M₂、M₃And M₄Four diodes D₁、D₂、D₃And D₄An inductor L and a capacitor C, M₁、M₂、D₁、D₂L, C form a charging loop; m₃、M₄、D₃、D₄L, C form a discharge loop; m₁The source of the diode is connected with the anode of D1, the cathode of D1 is respectively connected with one end of L and the drain of M3, the other end of L is connected with the positive electrode of C, the negative electrode of C is respectively connected with the cathode of D4 and the drain of M2, the source of M2 is connected with the positive electrode of D2, the negative electrode of D2 is connected with the negative electrode of a BOOST conversion module capacitor, and M2 is connected with the negative electrode of₁The drain electrode of the BOOST conversion module capacitor is connected with the positive electrode of the BOOST conversion module capacitor, the source electrode of M3 is connected with the positive electrode of D3, the positive electrode of D4 is connected with the source electrode of M4, the drain electrode of M4 is connected with the negative electrode of an equalizing bus II, and D₃The negative electrode is connected with the positive electrode of the equalizing bus II, and the gates of M1, M2, M3 and M4 are connected with a driving circuit; wherein the MOS transistor M₁And M₂Driven by a PWM + signal, M₃And M₄Driven by another PWM signal with reverse state, four diodes D₁、D₂、D₃And D₄The reverse current limiting function is realized.

2. The power battery pack equalization circuit based on boost conversion and soft switching according to claim 1, wherein: the LC resonant circuit is driven by complementary PWM signals of the two states and alternately changes between a charging state and a discharging state.

3. The power battery pack equalization circuit based on boost conversion and soft switching according to claim 2, wherein: the charging state is that the LC resonance circuit is connected with the BOOST conversion module in parallel.

4. The power battery pack equalization circuit based on boost conversion and soft switching according to claim 2, wherein: the discharge state is that the LC resonance circuit is connected with the battery monomer with the lowest voltage in parallel.

5. The power battery pack equalization circuit based on boost conversion and soft switching according to claim 1, wherein: and when the frequency of the PWM signal is equal to the inherent resonant frequency of the LC resonant circuit, the equalizing circuit performs zero-current switching equalization on the two battery monomers with the maximum voltage difference in the battery pack.

6. The method for implementing the power battery pack equalization circuit based on the boost conversion and the soft switch as claimed in any one of claims 1 to 5, characterized in that: the method comprises the following steps:

(1) obtaining the voltage of the monomer: the microcontroller acquires the voltage of each monomer of the power battery by means of the analog-to-digital conversion module, so as to determine the highest monomer voltage, the lowest monomer voltage and the corresponding battery monomer number;

(2) judging the voltage: the microcontroller calculates the maximum monomer voltage difference according to the acquired highest and lowest cell voltages, and if the difference value is greater than a cell balancing threshold value, the balancing circuit is started;

(3) gating the battery: the microcontroller controls the switch module to gate the battery monomer corresponding to the highest monomer voltage and the lowest monomer voltage to the balance bus through the battery monomer number corresponding to the highest monomer voltage and the lowest monomer voltage determined by the decoding circuit;

(4) energy transfer: the microcontroller controls the BOOST conversion module to BOOST the battery monomer with the highest voltage to a higher voltage, and controls the LC resonance circuit to alternately work in a charging state and a discharging state, so that the continuous transmission of energy is realized.

7. An implementation method as claimed in claim 6, characterized in that: in the step (4), when the LC resonant circuit is connected in parallel with the BOOST conversion module, the BOOST conversion control mode is PID closed-loop control, the BOOST conversion module charges the LC resonant circuit, when the LC resonant circuit is connected in parallel with the battery cell with the lowest voltage, the LC resonant circuit charges the battery cell, and energy is transferred from the battery cell with higher voltage to the battery cell with lower voltage along with the charging and discharging of the LC resonant circuit.