CN102496976A - Equalization charging device of series connected lithium batteries - Google Patents

Abstract

The utility model relates to a series lithium battery equalizing charging device, which relates to a battery charging device. Provided is a series lithium battery balance charging device which introduces a public energy pool structure and can better solve the balance problem of series lithium battery packs. A multi-coil transformer, an energy conversion circuit, a voltage detection circuit and a control unit are provided; the energy conversion circuit is respectively connected to the coil group of the multi-coil transformer and the two ends of each single battery of the series battery pack, and the control signal input of the energy conversion circuit connected to the control signal output terminal of the control unit; the detection voltage input terminal of the voltage detection circuit is connected to the two ends of the single cells of the series battery pack in parallel, and the detection voltage output terminal of the voltage detection circuit is connected to the detection voltage input terminal of the control unit .

Description

Balanced charging device for lithium batteries in series

technical field

The invention relates to a battery charging device, in particular to a series lithium battery equalizing charging device.

Background technique

Due to the advantages of high energy density, long service life, and high voltage, lithium-ion batteries have become the first choice for energy storage power supplies that require high electrical performance, reliability, and safety, and have attracted much attention. The voltage of a lithium battery cell is about 3-4V. In order to meet the needs of high-power vehicles, the power battery must connect the cells in series. However, the chemical conditions of each cell may be different, such as the voltage, internal resistance, and capacity of the battery. There are differences in parameters such as charging and receiving capacity, cycle life, etc. Repeated charging and discharging cycles will also make this difference worse, and eventually cause serious inconsistencies in capacity and voltage between the batteries connected in series, thus affecting the performance and capacity of the entire battery pack in series. Seriously reduce battery life. The balance between the single cells of the series battery pack has become a key technology that restricts the development of power lithium batteries.

At present, there are two general equalization strategies: energy-consuming equalization and non-energy-consuming equalization, and non-energy-consuming equalization includes energy transfer and energy conversion. The energy-consumption equalization method is simple to control, but requires high-power resistors, high-current power switches, high energy consumption, and an auxiliary heat treatment device. The non-energy balance control method, whether it is transfer or conversion, has a large number of control switches, large current and voltage stress, and complex control logic. In the Chinese invention patent application CN1275829A, a battery equalization circuit is disclosed, which does not need to measure the voltage of each battery, but balances the battery pack composed of two adjacent series batteries, and connects a switch circuit between the two batteries. A resonant circuit is connected between the common node of the battery and the switch circuit, and the resonant circuit is alternately connected in parallel with the first and second batteries by the switch circuit, so that the DC component passes through the resonant circuit as a function of the charge imbalance between the first and second batteries. The flow between them, however, is achieved through a resonant circuit, so a resonant coil and an iron core need to be provided, resulting in an increase in the weight and volume of the balanced circuit. In view of the above reasons, there is no ideal equalization technique for series-connected battery packs that can be used in practice.

Contents of the invention

The purpose of the present invention is to provide a series lithium battery equalization charging device that introduces a common energy pool structure and can better solve the problem of series lithium battery equalization for the above-mentioned shortcomings of the existing series lithium battery pack equalization method.

The present invention is provided with multi-coil transformer, energy conversion circuit, voltage detection circuit and control unit; Said energy conversion circuit is respectively connected with the coil group of multi-coil transformer and the two ends of each monomer battery of series battery pack, the control of energy conversion circuit The signal input terminal is connected to the control signal output terminal of the control unit; the detection voltage input terminal of the voltage detection circuit is connected to the two ends of the single cells of the series battery pack in parallel, and the detection voltage output terminal of the voltage detection circuit is connected to the detection voltage of the control unit input.

The multi-coil transformer is composed of an iron core and at least two sets of coils, and the multiple sets of coils are coupled to each other through magnetic hinges to form a common magnetic energy pool.

The energy conversion circuit is provided with a MOS switch drive circuit, a rectifier diode and a ballast inductor, and the MOS switch drive circuit is connected with the rectifier diode and the ballast inductor; the input terminal of the MOS switch drive circuit is connected to the control signal output of the control unit end connection.

The energy conversion circuit cooperates with the multi-coil transformer to convert the energy in the high-energy single battery into magnetic field energy and store it in the public energy pool, and also convert the magnetic field energy in the public energy pool into electric field energy and inject it into the low-energy monomer battery.

The voltage detection unit is used to detect the voltage of the single battery as a basis for judging the energy level of the single battery.

The control unit is composed of a microprocessor and a logic circuit, and the microprocessor is connected with the logic circuit for overall control.

The present invention is based on a magnetic field public energy pool formed by a multi-coil transformer, which converts the energy of a single battery with high energy into magnetic field energy and stores it in the magnetic field public energy pool, and at the same time converts the magnetic field energy in the magnetic field public energy pool into electric field energy Injected into single cells with low energy. This solves the problem of many switching elements and many transformers in the usual non-energy-consumption equalization technology.

The present invention adopts the balance control technology of energy public pool type, and the so-called public energy pool is a public magnetic field energy pool for storing magnetic field energy formed by multi-coil group transformers. The balance charging transfer device is composed of a multi-coil transformer, an energy conversion circuit, a voltage detection circuit and a control unit. After the energy conversion circuit is connected to the corresponding coil group in the multi-coil transformer, it is connected to both ends of the corresponding single battery, and the voltage detection circuit is connected to the two ends of the single battery. The control unit is connected to the voltage detection circuit and the MOS switch drive circuit. connect.

Description of drawings

Fig. 1 is a block diagram of the structural composition of the embodiment of the present invention.

Fig. 2 is a schematic diagram of the circuit principle of the embodiment of the present invention.

FIG. 3 is a schematic diagram of the principle of an equalization unit and a driving circuit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the principle of a voltage detection circuit according to an embodiment of the present invention.

In the figure, each mark is: 1 is a multi-coil transformer, D1, D2...Dn are rectifier diodes, L1, L2...Ln are ballast inductors, Q1, Q2...Qn form a switching circuit, B1, B2...Bn form a battery pack in series.

Detailed ways

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

Referring to Fig. 1, the embodiment of the present invention is provided with multi-coil transformer 1, energy conversion circuit 2, voltage detection circuit 3 and control unit 4; The two ends of each single battery are connected, the control signal input end of the energy conversion circuit 1 is connected with the control signal output end of the control unit 4; At both ends, the detection voltage output terminal of the voltage detection circuit 3 is connected to the detection voltage input terminal of the control unit 4 .

The multi-coil transformer 1 is composed of an iron core and at least two sets of coils, and the multiple sets of coils are coupled to each other through magnetic hinges to form a common magnetic energy pool.

The energy conversion circuit 2 is provided with a MOS switch drive circuit, a rectifier diode and a ballast inductor, and the MOS switch drive circuit is connected with the rectifier diode and the ballast inductor; the input terminal of the MOS switch drive circuit is connected to the control signal of the control unit output connection.

The energy conversion circuit 2 cooperates with the multi-coil transformer 1 to convert the energy in the high-energy single battery into magnetic field energy and store it in the public energy pool, and also convert the magnetic field energy in the public energy pool into electric field energy and inject it into the low-energy battery. in a single battery.

The voltage detection unit 3 is used to detect the voltage of the single battery as a basis for judging the energy level of the single battery.

The control unit 4 is composed of a microprocessor and a logic circuit, and the microprocessor is connected with the logic circuit for overall control.

As shown in Figure 2, the energy conversion circuit is composed of a controllable MOS switch transistor Qi, a corresponding drive circuit A, a rectifier diode Di, and a ballast inductor Li. Figure 3 shows the equalization unit and drive circuit. In the figure, TR is a shared multi-coil transformer, and PWM is the PWM signal terminal controlled by the AVR single-chip microcomputer. Q1 is a switch tube. When the gate of Q1 is driven by PWM, the balance unit of the battery is used as a shunt balance unit, that is, the charging current of B1 is shunted. When the gate of Q1 does not add a control signal, the balance unit acts as a confluence In addition to the original charging current, the charging current of the unit, that is, the battery, also adds the current from the TR transformer. In the circuit, D1 is a rectifier diode, and the inductor acts as a ballast. The circuit parameters are designed as follows: the switch tube is IRLL2705, a high-current MOSFET switch tube started by low voltage. Optocoupler chooses high-speed optocoupler 6N137, diode chooses Schottky diode 1N5819, the inductance determines the size of the shunt or confluence current according to the capacity of the battery, and then chooses the size of the inductance, generally 1/10-1/ of the coil inductance 100.

A multi-coil transformer is a transformer containing multiple sets of coil windings. Through an energy conversion circuit, electric field energy can be converted into magnetic field energy, and magnetic field energy can also be converted into electric field energy. Each group of coil windings is correspondingly connected to a rectifier diode Di, a switch transistor and a ballast inductor Li, and is connected in parallel with the single battery Bi through the rectifier diode Di, switch transistor and ballast inductor Li. When the switching tube Qi is working, the energy of the single battery Bi connected in parallel with it is converted into magnetic field energy through the coil winding and stored in the multi-coil transformer. When the switching tube Qi is not working, the coil winding couples the magnetic field energy in the multi-coil transformer It comes out and turns into electric field energy, which is injected into the single battery connected in parallel with it through the rectifier diode Di. The ballast inductor converts the pulsating current into a smooth current.

The voltage detection unit connected in parallel at both ends of the single battery is composed of electronic components such as a switch array and an amplifier circuit. It detects the voltage of each single battery and sends the voltage signal to the control unit. See Figure 4, CD4051 is a single 8-channel digital control analog electronic switch, two CD4051s are misplaced and connected to the battery, the same address just selects the positive and negative terminals of the battery to output, and the output is sent to the amplifier circuit, which is converted into a voltage range of 2.5V for AD input . Considering economy and practicability, the four operational amplifiers LM324 are selected as operational amplifiers. Other circuit parameters are: resistance R1=R2=2MΩ, R3=R4=1MΩ, R5=50Ω; capacitance C=0.1 μF.

The control unit is composed of a microprocessor, and the higher-level ATmega16 in the AVR microcontroller is selected. It receives the voltage signal of each single battery sent from the voltage detection unit, judges which single battery has relatively high energy and which single battery has relatively low energy, and sends a switch signal to the drive circuit according to the judgment result, and the drive corresponds to the energy The switch tubes in the energy conversion circuit on some high single cells convert the energy of these single cells into magnetic field energy and store it in the multi-coil transformer. At the same time, the rest of the coil groups on the multi-coil transformer work in the working state of converting magnetic field energy into electric field energy, and transform the magnetic field energy into electric field energy and inject it into other single batteries with lower energy.

Claims (3)

1. The balanced charging device for lithium batteries in series is characterized in that a multi-coil transformer, an energy conversion circuit, a voltage detection circuit and a control unit are provided; The two ends of the battery are connected, and the control signal input end of the energy conversion circuit is connected with the control signal output end of the control unit; The detection voltage output terminal is connected to the detection voltage input terminal of the control unit. 2. The balanced charging device for series lithium batteries as claimed in claim 1, wherein the multi-coil transformer is composed of an iron core and at least 2 sets of coils, and the multiple sets of coils are coupled to each other through magnetic hinges to form a common magnetic field energy pool. 3. The balanced charging device for series lithium batteries as claimed in claim 1, wherein said energy conversion circuit is provided with a MOS switch drive circuit, a rectifier diode and a ballast inductor, and said MOS switch drive circuit is connected with a rectifier diode and a ballast inductor. Inductive connection; the input end of the MOS switch driving circuit is connected with the control signal output end of the control unit.

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