A series lithium battery charging balance circuit

Abstract

The present invention discloses a series lithium battery charging balancing circuit, which includes a battery pack composed of N cells connected in series, a voltage sampling circuit for collecting the voltages of each cell in the battery pack, a DC-DC power module, a DC-DC output control circuit, a switch combination circuit, a switch driving circuit, and an MCU control unit. The DC-DC power module, the switch combination circuit, and the battery pack are connected in sequence. The voltage sampling circuit is connected to the MCU control unit. The MCU control unit, the DC-DC output control circuit, and the DC-DC power module are connected in sequence. The MCU control unit, the switch driving circuit, and the switch combination circuit are connected in sequence. The present invention can not only effectively monitor the voltages of each cell in the battery pack, charge the entire battery pack or part of the cells or even a single cell, solve the problem of balanced charging of each cell in the battery pack, and avoid the need to screen each cell due to individual differences.

Description

Technical Field

[0001] The present invention relates to the technical field of battery charging, and particularly to a series lithium battery charging balancing circuit. Background Art

[0002] In recent years, more and more lithium-ion batteries have been applied to medical, automotive, and consumer electronics. For different loads, it is often necessary to connect lithium batteries in series and parallel to meet the output requirements of different voltages and currents. However, due to the individual differences of each cell in the lithium battery pack formed by series and parallel connections, and external influences such as inconsistent working temperatures, after long-term operation, there will be significant differences among the cells, with inconsistent capacities. The inconsistent capacities of each cell can easily lead to a situation where some cells can be fully charged while some cannot (i.e., undercharging) during charging, which seriously affects the performance and service life of the lithium battery pack. Summary of the Invention

[0003] The purpose of the present invention is to provide a series lithium battery charging balancing circuit.

[0004] The technical solution for achieving the purpose of the present invention is: a series lithium battery charging balancing circuit, including a battery pack formed by N cells connected in series, a voltage sampling circuit for collecting the voltages of each cell in the battery pack, a DC-DC power module, a DC-DC output control circuit, a switch combination circuit, a switch driving circuit, and an MCU control unit. The DC-DC power module, the switch combination circuit, and the battery pack are connected in sequence. The voltage sampling circuit is connected to the MCU control unit. The MCU control unit, the DC-DC output control circuit, and the DC-DC power module are connected in sequence. The MCU control unit, the switch driving circuit, and the switch combination circuit are connected in sequence. Among them, the N cells in the battery pack are successively represented by C i (i = 1, 2, 3,..., N), N is a natural integer not less than 2, and both ends of the battery pack are output terminals;

[0005] The switch combination circuit includes 2N + 1 switches, and the 2N + 1 switches are successively represented by K j (j = 1, 2, 3,..., 2N + 1). Any cell C in the battery pack n is connected in parallel with three series-connected switches (K 2n-1 , K 2n , K 2n+1 ), n is any natural integer not greater than N;

[0006] Both ends of the DC-DC power module are connected in parallel with all the series-connected switches K 2m (m = 1, 2, 3,..., N);

[0007] The MCU control unit is used to receive the voltages of each battery cell collected by the voltage sampling circuit; control the switch driving circuit to drive the switch combination circuit by the switch driving circuit so that the switches in the switch combination circuit are switched accordingly; control the DC-DC output control circuit to drive the DC-DC power module by the DC-DC output control circuit to output the corresponding voltage.

[0008] When the subscripts of the above-mentioned battery cells C i are the same, they are the same battery cell; when the subscripts of the switches K j are the same, they are the same switch.

[0009] Further, the DC-DC output control circuit is a PWM circuit. Among them, the PWM circuit can be an off-the-shelf PWM chip or a PWM circuit built in and carried by the MCU control unit. The output waveform of the PWM circuit is controlled by the MCU control unit to switch the output of the DC-DC power module. Among them, when using the PWM circuit carried by the MCU control unit, since the MCU control unit is usually an HT66F0185 or STM32 series chip, from a macroscopic structure perspective, the DC-DC power module is directly connected to the MCU control unit. In addition, the DC-DC output control circuit of the present invention can also be a driving circuit that drives the MOS transistor switch in the DC-DC power module, such as driving chips like UCC27321, UCC37323, MD1211, etc.

[0010] Further, the switch driving circuit is either a PWM circuit or a MOS transistor switch driving circuit. Among them, the PWM circuit can be an off-the-shelf PWM chip or a PWM circuit built in and carried by the MCU control unit. When using the PWM circuit carried by the MCU control unit, since the MCU control unit is usually an HT66F0185 or STM32 series chip, from a macroscopic structure perspective, the switch combination circuit is directly connected to the MCU control unit; the MOS transistor switch driving circuit can be an off-the-shelf switch driving chip, such as UCC27321, UCC37323, MD1211, etc., or a MOS transistor switch driving circuit controlled by the input signal of the free MCU control unit.

[0011] The series lithium battery charging balance circuit of the present invention can not only effectively monitor the voltages of each battery cell in the battery pack, charge the entire battery pack, or part of the battery cells, or even a single battery cell, solve the problem of balanced charging of each battery cell in the battery pack, avoid the need to screen each battery cell due to individual differences, greatly simplify the cumbersome manufacturing processes of various products, improve the service life of the products, and reduce the safety risks in product use; moreover, when the battery pack discharges, the charging current is directly sent out from the discharge end of the battery pack, and it does not pass through any switch in the switch combination circuit, which can greatly reduce the circuit loss and the risk brought by the stress borne by the circuit switch device, better avoid the problem of device damage, does not affect the ultra-high power output of the battery pack, and can achieve the large current output of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic structural diagram of the series lithium battery charging balance circuit of the present invention;

[0013] Figure 2 is a circuit diagram of the switch combination circuit and the battery pack of the series lithium battery charging balance circuit of the present invention;

[0014] Figure 3 is a circuit diagram of the switch driving circuit driving a single switch in the series lithium battery charging balance circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The following will give a detailed description of the preferred embodiments of the series lithium battery charging balance circuit of the present invention with reference to the accompanying drawings:

[0016] As Figure 1 and Figure 2 shown, a series lithium battery charging balance circuit includes a battery pack 10 composed of N battery cells connected in series, a voltage sampling circuit 1 for collecting the voltages of each battery cell in the battery pack 10, a DC-DC power module 2, a DC-DC output control circuit 3, a switch combination circuit 4, a switch driving circuit 5, and an MCU control unit 6. The DC-DC power module 2, the switch combination circuit 4, and the battery pack 10 are connected in sequence. The voltage sampling circuit 1 is connected to the MCU control unit 6. The MCU control unit 6, the DC-DC output control circuit 3, and the DC-DC power module 2 are connected in sequence. The MCU control unit 6, the switch driving circuit 5, and the switch combination circuit 4 are connected in sequence. Among them,

[0017] The N battery cells in the battery pack 10 are sequentially represented by C i (i = 1, 2, 3,..., N), N is a natural integer not less than 2, and the two ends of the battery pack 10 are provided with a discharge end 101;

[0018] The switch combination circuit 4 includes 2N + 1 switches, and the 2N + 1 switches are sequentially represented by K j(j = 1, 2, 3, ……, 2N + 1) represents any battery cell C of the battery pack 10 n The two ends are connected in parallel with three switches (K 2n-1 , K 2n , K 2n+1 ) connected in series, and n is any natural integer not greater than N;

[0019] The two ends of the DC - DC power module 2 are connected in parallel with all the switches K 2m (m = 1, 2, 3, ……, N) connected in series;

[0020] The MCU control unit 6 is used to receive the voltages of each battery cell of the battery pack 10 collected by the voltage sampling circuit 1; control the switch driving circuit 5 to make the switch driving circuit 5 drive the switch combination circuit 4 so that the corresponding switches in the switch combination circuit 4 are switched; control the DC - DC output control circuit 3 to make the DC - DC output control circuit 3 drive the DC - DC power module 2 to output the corresponding voltage.

[0021] In the series lithium - battery charging balance circuit of the present invention, through the setting of the switch combination circuit 4, the charging form of the battery cells in the battery pack 10 can be adjusted and changed, such as all the battery cells being charged in series, or consecutive partial battery cells being charged together, or a single battery cell being charged separately. Taking the battery pack 10 composed of four series - connected battery cells as an example, the following table lists the existing charging situations and the switching states of the corresponding switches in the switch combination circuit 4.

[0022]

[0023] In the above table, √ represents closed and × represents open.

[0024] In the series lithium - battery charging balance circuit of the present invention, through the control of the switch combination circuit 4, the conversion of different charging situations can be achieved. Among them, the switch driving circuit 5 that drives the switch combination circuit 4 is controlled by the MCU control unit 6, and the MCU control unit 6 can adjust the states of the switches in the switch combination circuit 4 through the control of the switch driving circuit 5.

[0025] The series lithium battery charging balancing circuit of the present invention, the switch driving circuit 5 is either a PWM circuit or a MOS transistor switch driving circuit. Among them, the PWM circuit can be an off-the-shelf PWM chip, or a PWM circuit built in and carried by the MCU control unit 6. When using the PWM circuit carried by the MCU control unit 6, since the MCU control unit 6 is usually a chip of the HT66F0185 or STM32 series, in terms of the macroscopic structure, the switch combination circuit 4 is directly connected to the MCU control unit 6. The MOS transistor switch driving circuit can be an off-the-shelf switch driving chip, such as UCC27321, UCC37323, MD1211, etc., or a MOS transistor switch driving circuit controlled by the input signal of the MCU control unit 6, such as Figure 3 shown, which gives a MOS transistor switch driving circuit controlled by the input signal of the MCU control unit 6. In this circuit, the transistors Q1 and Q2 are controlled by the input signal of the MCU control unit 6, so that the MOS transistor Q3 obtains the ability to drive each switch in the switch combination circuit 4 from VCC, and then controls the switch combination circuit 4. Since the driving circuit of the driving switch is the structure of a conventional circuit, the present invention will not elaborate too much on it.

[0026] The series lithium battery charging balancing circuit of the present invention, under different charging conditions, especially when the number of charged battery cells changes, it is often required that the output voltage of the DC-DC power module 2 be adjusted accordingly. For example, when the charging voltage of one battery cell is 4.2V, when charging two battery cells, it is required that the output voltage of the DC-DC power module 2 be 8.4V; when charging three battery cells, it is required that the output voltage of the DC-DC power module 2 be 12.6V; when charging four battery cells, it is required that the output voltage of the DC-DC power module 2 be 16.8V.

[0027] The series lithium battery charging balancing circuit of the present invention, the DC-DC power module 2 is a DC-DC power module with adjustable output voltage. The MCU control unit 6 controls the DC-DC output control circuit 3 to drive the DC-DC power module 2 to output the corresponding voltage.

[0028] The series lithium battery charging balance circuit of the present invention, the DC-DC output control circuit 3 is any one of a PWM circuit or a MOS transistor switch driving circuit. Among them, the PWM circuit can be an off-the-shelf PWM chip, or a PWM circuit built in and self-contained in the MCU control unit 6. By controlling the output waveform of the PWM circuit through the MCU control unit 6, the output of the DC-DC power module 2 is switched. When using the PWM circuit self-contained in the MCU control unit 6, since the MCU control unit 6 is usually a chip of the HT66F0185 or STM32 series, in terms of the macroscopic structure, the DC-DC power module 2 is directly connected to the MCU control unit 6. In addition, the DC-DC output control circuit 3 of the present invention can also be a driving circuit for driving the MOS transistor switch in the DC-DC power module 2, such as driving chips like UCC27321, UCC37323, MD1211, etc.

[0029] The series lithium battery charging balance circuit of the present invention, through the control of the MCU control unit 6, can realize the conversion of different charging forms of the battery cells in the battery pack 10, greatly improving the charging flexibility. For example, at the initial stage of charging, usually all the battery cells in the battery pack 10 can be connected in series for charging together. After the voltage sampling circuit 1 detects that the voltage of any battery cell reaches the preset value in the MCU control unit 6, the MCU control unit 6 can control the switch driving circuit 5 to adjust the switch states of the switches in the switch combination circuit 4. For example, the consecutive battery cells whose voltage values have not reached the preset value can be charged together, or the battery cells whose voltage values have not reached the preset value can be charged one by one individually, so that the voltage of all the battery cells in the battery pack 10 can reach the preset value, thereby making the charging of each battery cell in the battery pack 10 more balanced, and preventing the situation that some battery cells cannot be fully charged (under-voltage) due to the individual differences of the battery cells.

[0030] The series lithium battery charging balance circuit of the present invention can not only effectively monitor the voltage of each battery cell in the battery pack 10, charge the entire battery pack 10 or part of the battery cells or even a single battery cell, solve the problem of balanced charging of each battery cell in the battery pack 10, and avoid the need to screen each battery cell due to individual differences, which greatly simplifies the cumbersome manufacturing processes of various products, improves the service life of the products, and reduces the safety risks in product use; and when the battery pack 10 discharges, the charging current is directly sent out from the discharge end 101 of the battery pack 10, and it does not pass through any switch in the switch combination circuit 4, which can greatly reduce the circuit loss and the risk brought by the stress borne by the circuit switch devices, preferably avoid the problem of device damage, and does not affect the ultra-high power output of the battery pack to the outside, and can realize the large current output of the battery pack.

[0031] For the series lithium battery charging balance circuit of the present invention, the MCU control unit 6 can usually adopt chips of series such as HT66F0185 or STM32.

[0032] The present invention is not limited to the embodiments described. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as falling within the protection scope of the present invention.

Claims

1. A series lithium battery charging balance circuit, characterized in that: It includes a battery pack formed by connecting N battery cells in series, a voltage sampling circuit for collecting the voltages of each battery cell in the battery pack, a DC-DC power module, a DC-DC output control circuit, a switch combination circuit, a switch driving circuit, and an MCU control unit. The DC-DC power module, the switch combination circuit, and the battery pack are connected in sequence. The voltage sampling circuit is connected to the MCU control unit. The MCU control unit, the DC-DC output control circuit, and the DC-DC power module are connected in sequence. The MCU control unit, the switch driving circuit, and the switch combination circuit are connected in sequence. Among them, the N battery cells in the battery pack are successively represented by C i where i = 1, 2, 3, ……, N, and N is a natural integer not less than 2. The two ends of the battery pack are output terminals; The switch combination circuit includes 2N + 1 switches, and the 2N + 1 switches are sequentially represented by K j , where j = 1, 2, 3,..., 2N + 1. Any battery cell C of the battery pack n has both ends connected in parallel with three sequentially connected switches K 2n-1 , K 2n , K 2n+1 , and n is any natural integer not greater than N; Both ends of the DC-DC power module are connected in parallel with all switches K connected in series, where m = 1, 2, 3, ……, N; 2m where m = 1, 2, 3, ……, N; The MCU control unit is used to receive the voltages of each battery cell collected by the voltage sampling circuit; control the switch drive circuit to drive the switch combination circuit by the switch drive circuit so that each switch in the switch combination circuit is switched accordingly; control the DC-DC output control circuit to drive the DC-DC power module by the DC-DC output control circuit to output a corresponding voltage.

2. The series lithium battery charging balance circuit according to claim 1, characterized in that: The DC-DC output control circuit is a PWM circuit.

3. The series lithium battery charging balance circuit according to claim 1, wherein: The switch drive circuit is either a PWM circuit or a MOS transistor switch drive circuit.

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