CN211606124U - Balanced charge-discharge protection circuit of lithium battery pack - Google Patents

Abstract

The utility model discloses a lithium battery pack balanced charging and discharging protection circuit, which comprises a control circuit, a main circuit and N shunting discharging branches, wherein each shunting discharging branch comprises a switch and a resistor which are connected in series in sequence; the main circuit comprises N lithium batteries, an MOS (metal oxide semiconductor) tube charging control switch and an MOS tube discharging control switch which are sequentially connected in series, the anode of the first lithium battery is anode BAT +, the cathode of the Nth lithium battery is connected with the source electrode of the MOS tube discharging control switch, the drain electrode of the MOS tube discharging control switch is connected with the drain electrode of the MOS tube charging control switch, the source electrode of the MOS tube charging control switch is cathode BAT-, and a shunt discharging branch is connected with the two ends of each lithium battery in parallel. The utility model discloses an above-mentioned circuit, the protection of charging overvoltage, discharge undervoltage, overcurrent, short circuit can be realized to each section lithium cell homoenergetic, and has realized the problem of whole group battery equalizing charge in the charging process.

Description

A lithium battery pack balanced charge and discharge protection circuit

technical field

The utility model relates to the field of protection circuits, in particular to a lithium battery pack balanced charge and discharge protection circuit.

Background technique

At present, the application of lithium batteries is becoming more and more popular. In the process of charging and discharging, there are occasional overcharge and overdischarge, each battery cannot be charged and discharged evenly, and even overheating and short circuit cause combustion and explosion. In order to use safety and improve battery efficiency, it is very important to It is necessary to research groups of lithium batteries connected in series to avoid overcharging and overdischarging, and it is necessary to have an effective device for energy balance.

When charging a group of lithium batteries in series, ensure that each battery is charged equally, otherwise the performance and life of the entire group of batteries will be affected during use. Commonly used equalizing charging techniques include constant shunt resistance equalizing charging, on-off shunt resistance equalizing charging, average battery voltage equalizing charging, switched capacitor equalizing charging, buck converter equalizing charging, inductor equalizing charging and other methods. However, the existing single-cell lithium battery protection chips do not have equalizing charge control function; the equalizing charge control function of multi-cell lithium battery protection chips requires an external central processing unit (CPU), through serial communication with the protection chip (such as I2C bus) It increases the complexity and design difficulty of the protection circuit, reduces the efficiency and reliability of the system, and also increases the power consumption of the management battery itself.

Utility model content

The technical problem to be solved by the utility model is to realize the balanced charging of the whole group of batteries, and the purpose is to provide a balanced charge-discharge protection circuit of the lithium battery group, and each section of the lithium battery can realize charging overvoltage, discharge undervoltage, overcurrent and short circuit. protection, and the problem of balanced charging of the entire battery pack is realized during the charging process.

The utility model is realized through the following technical solutions:

A lithium battery pack balanced charge and discharge protection circuit, comprising a control circuit, a main circuit and N shunt and discharge branches, each shunt and discharge branch includes switches and resistors connected in series in sequence; the main circuit includes N sections in series in series Connected lithium battery, MOS tube charging control switch and MOS tube discharge control switch, the positive pole of the first lithium battery is the positive pole BAT+, the negative pole of the Nth lithium battery is connected to the source of the MOS tube discharge control switch, and the MOS tube discharge control switch The drain of the MOS tube charging control switch is connected to the drain of the MOS tube charging control switch, the source of the MOS tube charging control switch is the negative electrode BAT-, and a shunt discharge branch is connected in parallel at both ends of each lithium battery; the control circuit includes N single-cell lithium batteries. Battery protection chip, OR gate, AND gate and N over-current detection protection resistors. The single-cell lithium battery protection chip is connected to the single-cell lithium battery one-to-one. The VDD port of each lithium battery protection chip is connected to the positive pole of the corresponding lithium battery. , the VSS port of each lithium battery protection chip is connected to the negative electrode of the corresponding lithium battery, the VM port of each lithium battery protection chip is connected to one end of an overcurrent detection protection resistor, and the other end of the overcurrent detection protection resistor is connected to a single cell lithium battery The negative pole of the single-cell lithium battery corresponding to the battery protection chip, the CO ports of the N single-cell lithium battery protection chips are connected to the same end of the OR gate, and the other end of the OR gate is connected to the gate of the MOS tube charging control switch, and the N single-cell lithium batteries The DO port of the protection chip is connected to the same end of the AND gate, and the other end of the AND gate is connected to the gate of the MOS tube discharge control switch. The CO port of each single-cell lithium battery protection chip is also connected to the moving end of the switch on the corresponding shunt discharge branch.

In this solution, each cell of lithium battery can realize the protection of charging overvoltage, discharging undervoltage, overcurrent and short circuit. A single cell lithium battery protection chip is used to protect the group of lithium batteries in any number of series, and the whole constitutes a balanced charging system. The functional battery pack protection circuit uses the lithium battery protection chip to control the on-off of the shunt and discharge branch switch devices to achieve the problem of balanced charging of the entire battery pack. The protection circuit has perfect protection functions, stable work, high cost performance, and small balanced charging errors. 50mV or less. This design scheme is different from the traditional method of realizing balanced charging at the charger end, which reduces the cost of designing and applying the lithium battery pack charger, thereby improving the cost performance of the protection circuit.

Preferably, the source of the MOS tube charge control switch is connected to the anode of the diode D1, the drain of the MOS tube charge control switch is connected to the cathode of the diode D1, the source of the MOS tube discharge control switch is connected to the anode of the diode D2, and the MOS tube discharge control switch is connected to the anode of the diode D2. The drain is connected to the cathode of diode D2.

Preferably, the value of N is a positive integer greater than or equal to 2.

A lithium battery pack balanced charge and discharge protection circuit, comprising lithium battery protection chips U1-U4, NAND gate U5, MOS transistors T1-T4, optocoupler U9-U12, optocoupler U15-U18, triode U21-U24, The OD ends of the lithium battery protection chips U1-U4 are sequentially connected to one end of the resistor R17, one end of the resistor R19, one end of the resistor R21 and one end of the resistor R23, the other end of the resistor R17, the other end of the resistor R19, the other end of the resistor R21 and the other end of the resistor R23 in sequence. Connect to port 1 of optocoupler U9, port 1 of optocoupler U10, port 1 of optocoupler U11, and port 1 of optocoupler U12; the OC terminals of the lithium battery protection chips U1-U4 are sequentially connected to one terminal of resistor R18 , One end of resistor R20, one end of resistor R22 and one end of resistor R24, the other end of resistor R18, the other end of resistor R20, the other end of resistor R22 and the other end of resistor R24 are connected to port 1 of optocoupler U15, port 1 of optocoupler U16, Port 1 of the optocoupler U17 and port 1 of the optocoupler U18; resistor R9 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U1, and the VCC terminal of the lithium battery protection chip U1 is also connected to the resistor R3 and the GND terminal. One end of the capacitor C3, the other end of the resistor R3 is connected to the R+ end, and the other end of the capacitor C3 is connected to the GND end of the lithium battery protection chip U1, the port 2 of the photocoupler U9 and the port 2 of the photocoupler U15; the lithium battery protection chip U2 A resistor R10 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U2. The VCC terminal of the lithium battery protection chip U2 is also connected to one end of the resistor R4 and one end of the capacitor C4, and the other end of the resistor R4 is connected to the port 2 of the optocoupler U9 and the optocoupler U15. Port 2, the other end of the capacitor C4 is connected to the GND terminal of the lithium battery protection chip U2, the port 2 of the photocoupler U10 and the port 2 of the photocoupler U16 at the same time; the CS terminal and the GND terminal of the lithium battery protection chip U3 are connected in series Resistor R11, the VCC end of the lithium battery protection chip U3 is also connected to one end of the resistor R5 and one end of the capacitor C5, the other end of the resistor R5 is connected to the port 2 of the photocoupler U10 and the port 2 of the photocoupler U16 at the same time, and the other end of the capacitor C5 is connected at the same time The GND terminal of the lithium battery protection chip U3, the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17; the resistance R12 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U4, and the The VCC end is also connected to one end of the resistor R6 and one end of the capacitor C6, the other end of the resistor R6 is connected to the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17 at the same time, and the other end of the capacitor C6 is also connected to the GND end of the lithium battery protection chip U4, The common connection terminal of the resistor R26 and the capacitor C7, the other end of the resistor R26 is also connected to the port 12 of the NAND gate U5, and the other end of the capacitor C7 is connected to the port 4 of the optocoupler U9 and the optocoupler port 4 of the NAND gate U15; the port 1 of the NAND gate U5 is connected to the port 11, the port 10 and the port 13 of the NAND gate U5 are connected, the resistor R28 is connected in series between the ports 7 and 8 of the NAND gate U5, and the NAND gate Ports 5, 6, and 7 of U5 are connected, and ports 8 and 9 of NAND gate U5 are connected. Port 8 of NAND gate U5 is also connected to one end of resistor R29, and the other end of resistor R29 is connected to the drains of MOS transistors T1 and T2 at the same time. The port 3 of the NOT gate U5 is also connected to one end of the resistor R27, the other end of the resistor R27 is connected to the gates of the MOS transistors T1 and T2 at the same time, the port 14 of the NAND gate U5 is also connected to one end of the resistor R25, and the other end of the resistor R25 is also connected to the photoelectric coupling. Port 2 of U9 and U15, resistor R30 and resistor R31 are connected in series, the floating end of resistor R30 is connected to port 3 of photocoupler U18, and the floating end of resistor R31 is connected to the source of MOS transistors T3 and T4 at the same time, resistor R30 and resistor The common connection terminal of R31 is connected to the gates of the MOS transistors T3 and T4 at the same time; the drains of the MOS transistors T1-T4 are all connected, and the sources of the MOS transistors T1-T2 are connected to the port 5 of the NAND gate and the lithium battery protection chip U4 at the same time. Port GND, port 2 of the optocoupler U18 and port 2 of the optocoupler U12; the port 4 of the optocoupler U9 is connected to the port 4 of the optocoupler U15, and the port 3 of the optocoupler U9 is connected to the optocoupler U10 The port 4 of the optocoupler U15 is connected to the port 4 of the optocoupler U16, the port 3 of the optocoupler U10 is connected to the port 4 of the optocoupler U11, and the port 3 of the optocoupler U16 is connected to the optocoupler Port 4 of U17 is connected, port 3 of photocoupler U11 is connected to port 4 of photocoupler U12, port 3 of photocoupler U17 is connected to port 4 of photocoupler U18; between the emitter and collector of transistor U21 Resistor R1 and resistor RA3 are connected in series in sequence, and resistor R2 and resistor R7 are connected in series between the emitter and base of transistor U21; resistor RA4 is connected in series between the base of transistor U21 and the collector of transistor U22, and the base and transistor of transistor U21 are connected in series. Resistor R8 is connected in series between the emitters of U22, resistors R13 and R14 are connected in series between the emitter and base of the transistor U22; resistors RA5 are connected in series between the base of the transistor U22 and the collector of the transistor U23, and the base and the base of the transistor U22 are connected in series. A resistor R15 is connected in series between the emitters of the transistor U23, resistors R16 and R35 are connected in series between the emitter and the base of the transistor U23, and a resistor RA6 is connected in series between the base of the transistor U23 and the collector of the transistor U24, and the base of the transistor U23 is connected in series. Resistor R32 is connected in series with the emitter of transistor U24, resistors R33 and R34 are connected in series between the emitter and base of transistor U24, and the base of transistor U24 is also connected to port 2 of optocoupler U12, and the common connection of R1 and RA3 terminal, U21 base and common connection of RA4 The terminal, the base electrode of U22 and the common connection end of RA5, the base electrode of U23 and the common connection end of RA6 are sequentially connected to port 4, port 3, port 2, and port 1 of the interface P1.

Preferably, diodes Q1, Q3, Q4 and Q2 are connected in series between the drains and sources of the MOS transistors T1-T4, and the anodes of the diodes Q1, Q3, Q4 and Q2 are all connected to the source of the MOS transistors.

Compared with the prior art, the utility model has the following advantages and beneficial effects: each cell of the lithium battery can realize the protection of charging overvoltage, discharge undervoltage, overcurrent and short circuit, and a single cell lithium battery protection chip is used to protect any The battery pack protection circuit with balanced charging function is formed as a whole for protection by groups of lithium batteries connected in series. The lithium battery protection chip is used to control the on-off of the shunt and discharge branch switch devices to realize the problem of balanced charging of the whole group of batteries. The protection circuit The protection function is perfect, the work is stable, the cost performance is high, and the equalization charging error is small, below 50mV. This design scheme is different from the traditional method of realizing balanced charging at the charger end, which reduces the cost of designing and applying the lithium battery pack charger, thereby improving the cost performance of the protection circuit.

Description of drawings

The accompanying drawings described herein are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the present application, and do not constitute a limitation to the embodiments of the present invention. In the attached image:

Fig. 1 is the circuit diagram of the utility model;

Fig. 2 is the circuit diagram of the charging process of the circuit of Fig. 1;

Fig. 3 is the circuit diagram of the shunt equalization process of the circuit of Fig. 1;

Fig. 4 is the circuit diagram of the discharge process of the circuit of Fig. 1;

Fig. 5 is a partial circuit diagram of a specific 12V lithium battery pack protection circuit with balanced charging capability based on the principle of Fig. 1;

FIG. 6 is another part of the circuit diagram of the specific 12V lithium battery pack protection circuit with balanced charging capability based on the principle of FIG. 1 , and FIG. 5 and FIG. 6 form a complete circuit diagram.

The marks in the attached drawings and the corresponding parts names:

1. Lithium battery; 2. Resistor; 3. Switch; 4. Overcurrent detection and protection resistor; 5. The omitted lithium battery protection chip and circuit connection part; 6. Single-cell lithium battery protection chip; 7. OR gate; 8. AND gate; 9, charge control switch device; 10, discharge control switch device; 11, control circuit; 12, main circuit; 13, shunt discharge branch.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present utility model clearer, the present utility model will be described in further detail below in conjunction with the embodiments and the accompanying drawings. The invention is not intended to limit the present invention.

Example 1:

As shown in Figures 1-6, the utility model includes a lithium battery pack balanced charge and discharge protection circuit, including a control circuit 11, a main circuit 12 and N shunt discharge branches 13, each shunt discharge branch 13 includes a sequential The switch 3 and the resistor 2 connected in series; the main circuit 12 includes N lithium batteries 1, MOS tube charging control switch 9 and MOS tube discharge control switch 10 connected in series in sequence, and the positive pole of the first lithium battery is the positive pole BAT+, The negative electrode of the Nth lithium battery is connected to the source of the MOS tube discharge control switch 10, the drain of the MOS tube discharge control switch 10 is connected to the drain of the MOS tube charge control switch 9, and the source of the MOS tube charge control switch 9 is the negative electrode BAT- , both ends of each lithium battery 1 are connected in parallel with a shunt discharge branch; the control circuit 11 includes N single-cell lithium battery protection chips 6, OR gates 7, AND gates 8 and N overcurrent detection protection resistors 4, The single-cell lithium battery protection chip 6 is connected to the single-cell lithium battery 1 one-to-one, the VDD port of each lithium battery protection chip 6 is connected to the positive pole of the corresponding lithium battery 1, and the VSS port of each lithium battery protection chip 6 is connected to the corresponding cell. The negative electrode of lithium battery 1, the VM port of each lithium battery protection chip 6 is connected to one end of an overcurrent detection protection resistor 4, and the other end of the overcurrent detection protection resistor 4 is connected to the single cell lithium battery corresponding to the single-cell lithium battery protection chip 6. The negative electrode of the battery 1, the CO ports of the N single-cell lithium battery protection chips 6 are all connected to the same end of the OR gate 7, and the other end of the OR gate 7 is connected to the gate of the MOS tube charging control switch 9, and the N single-cell lithium battery protection chips 6 The DO ports are all connected to the same end of the AND gate 8, and the other end of the AND gate 8 is connected to the gate of the MOS tube discharge control switch 10, and the CO port of each single-cell lithium battery protection chip 6 is also connected to the switch on the corresponding shunt discharge branch 13 at the same time. the moving end. In each single-cell lithium battery in Figure 1, CO is the charge control pin, DO is the discharge control pin, VM is the discharge overcurrent and short circuit detection pin VM, VDD is the battery positive terminal VDD, and VSS is the battery negative terminal. Mark 5 is the omitted lithium battery protection chip and circuit connection part, OR gate 7 is the charging overvoltage protection signal after being isolated by the optocoupler to form a parallel relationship to drive the gate of the MOS transistor used for charging control in the main circuit, and the gate 8 is the discharge undervoltage The over-current short-circuit protection signal is isolated by the optocoupler and forms a series relationship to drive the MOS gate for discharge control in the main circuit.

The source of the MOS tube charge control switch 9 is connected to the anode of the diode D1, the drain of the MOS tube charge control switch 9 is connected to the cathode of the diode D1, the source of the MOS tube discharge control switch 10 is connected to the anode of the diode D2, and the MOS tube discharge control switch The drain of 10 is connected to the cathode of diode D2.

The value of N is a positive integer greater than or equal to 2.

When the lithium battery pack is charged, the positive and negative poles of the external power supply are connected to the positive and negative poles of the battery pack BAT+ and BAT- respectively, and the charging current flows through the positive pole BAT+ of the battery pack, the single-cell lithium batteries 1 to N in the battery pack, the discharge control switch, The charging control switch, the negative electrode BAT- of the battery pack, and the current flow are shown in Figure 2.

The charging overvoltage protection control signal of the single-cell lithium battery protection chip on the control circuit is isolated by the optocoupler and then output in parallel to provide the gate voltage for the conduction of the charging switch device 9 in the main circuit; During the charging process, the overvoltage protection state is entered first, and the shunt discharge branch connected in parallel with the positive and negative terminals of the single-cell lithium battery is controlled by the overvoltage protection signal to discharge 13, and at the same time, the corresponding single lithium battery connected in series in the charging circuit is isolated. out of the charging circuit.

When the lithium battery is charged in series, the influence of the capacity difference of the single cell is ignored, and the battery with the smaller internal resistance is generally charged first. At this time, the corresponding overvoltage protection signal controls the switching device of the shunt discharge branch to close, and a shunt resistor 2 is connected in parallel at both ends of the primary battery. According to the PNGV (the Partnership for a New Generation of Vehicles) equivalent circuit model of the battery, the shunt branch resistance is equivalent to the load of a single-cell lithium battery that is fully charged first, and the battery discharges through it to maintain the battery terminal voltage in a fully charged state. within a very small area nearby. Assuming that the first lithium battery is charged first and enters the overvoltage protection state, the current flow in the main circuit and the shunt discharge branch is shown in Figure 3. When all single-cell batteries are charged and enter the over-voltage protection state, the voltages of all single-cell lithium batteries are equal within the error range, and the charging protection control signals of each protection chip become low, which cannot be provided by the charging control switch device in the main circuit. The gate is biased to turn it off, and the main circuit is disconnected, that is, the balanced charging is realized, and the charging process is completed.

When the battery pack is discharged, the external load is connected to the positive and negative terminals of the battery pack BAT+ and BAT- respectively, and the discharge current flows through the negative pole BAT- of the battery pack, the charge control switch device, the discharge control switch device, and the single-cell lithium battery N in the battery pack. ~1 and the positive pole of the battery pack BAT+, the current flows as shown in Figure 4. In the control circuit part of the system, the discharge under-voltage protection, over-current and short-circuit protection control signals of the single-cell lithium battery protection chip are isolated by the optocoupler and then output in series to provide the gate voltage for the conduction of the discharge switching device in the main circuit; once the battery pack In the discharge process, when encountering special situations such as single-cell lithium battery under-voltage, over-current and short-circuit, the corresponding single-cell lithium battery discharge protection control signal becomes low and cannot provide gate bias for the discharge control switching device in the main circuit. It is turned off and the main circuit is disconnected, that is, the discharge use process is ended.

Generally, the lithium battery adopts constant current-constant voltage charging control. During constant voltage charging, the charging current decreases approximately exponentially. The switching devices of the charging and discharging main circuit in the system can be selected according to the maximum working current and working voltage required by the external circuit. The single-cell lithium battery protection chip of the control circuit can be selected according to the voltage level and protection delay time of the single-cell lithium battery to be protected. The discharge branch resistance connected in parallel at both ends of a single cell can be calculated according to the charging voltage of the lithium battery charger, the parameters of the lithium battery and the discharge current. The equalizing current should be selected reasonably. If it is too small, the equalizing effect will not be obvious; if it is too large, the energy loss of the system will be large, the equalizing efficiency will be low, and the thermal management requirements of the lithium battery pack will be high. Generally, the current size can be designed between 50 and 100 mA. The shunt discharge branch resistance can be realized by using power resistance or resistance network. Generally, the resistance network is used to realize the shunt discharge branch resistance, which can effectively eliminate the influence of resistance deviation, and can also play a role in reducing thermal power consumption.

In this solution, each cell of lithium battery can realize the protection of charging overvoltage, discharging undervoltage, overcurrent and short circuit. A single cell lithium battery protection chip is used to protect the group of lithium batteries in any number of series, and the whole constitutes a balanced charging system. The functional battery pack protection circuit uses the lithium battery protection chip to control the on-off of the shunt and discharge branch switch devices to achieve the problem of balanced charging of the entire battery pack. The protection circuit has perfect protection functions, stable work, high cost performance, and small balanced charging errors. 50mV or less. This design scheme is different from the traditional method of realizing balanced charging at the charger end, which reduces the cost of designing and applying the lithium battery pack charger, thereby improving the cost performance of the protection circuit.

Example 2:

A lithium battery pack balanced charge and discharge protection circuit, comprising lithium battery protection chips U1-U4, NAND gate U5, MOS transistors T1-T4, optocoupler U9-U12, optocoupler U15-U18, triode U21-U24, The OD ends of the lithium battery protection chips U1-U4 are sequentially connected to one end of the resistor R17, one end of the resistor R19, one end of the resistor R21 and one end of the resistor R23, the other end of the resistor R17, the other end of the resistor R19, the other end of the resistor R21 and the other end of the resistor R23 in sequence. Connect to port 1 of optocoupler U9, port 1 of optocoupler U10, port 1 of optocoupler U11, and port 1 of optocoupler U12; the OC terminals of the lithium battery protection chips U1-U4 are sequentially connected to one terminal of resistor R18 , One end of resistor R20, one end of resistor R22 and one end of resistor R24, the other end of resistor R18, the other end of resistor R20, the other end of resistor R22 and the other end of resistor R24 are connected to port 1 of optocoupler U15, port 1 of optocoupler U16, Port 1 of the optocoupler U17 and port 1 of the optocoupler U18; resistor R9 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U1, and the VCC terminal of the lithium battery protection chip U1 is also connected to the resistor R3 and the GND terminal. One end of the capacitor C3, the other end of the resistor R3 is connected to the R+ end, and the other end of the capacitor C3 is connected to the GND end of the lithium battery protection chip U1, the port 2 of the photocoupler U9 and the port 2 of the photocoupler U15; the lithium battery protection chip U2 A resistor R10 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U2. The VCC terminal of the lithium battery protection chip U2 is also connected to one end of the resistor R4 and one end of the capacitor C4, and the other end of the resistor R4 is connected to the port 2 of the optocoupler U9 and the optocoupler U15. Port 2, the other end of the capacitor C4 is connected to the GND terminal of the lithium battery protection chip U2, the port 2 of the photocoupler U10 and the port 2 of the photocoupler U16 at the same time; the CS terminal and the GND terminal of the lithium battery protection chip U3 are connected in series Resistor R11, the VCC end of the lithium battery protection chip U3 is also connected to one end of the resistor R5 and one end of the capacitor C5, the other end of the resistor R5 is connected to the port 2 of the photocoupler U10 and the port 2 of the photocoupler U16 at the same time, and the other end of the capacitor C5 is connected at the same time The GND terminal of the lithium battery protection chip U3, the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17; the resistance R12 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U4, and the The VCC end is also connected to one end of the resistor R6 and one end of the capacitor C6, the other end of the resistor R6 is connected to the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17 at the same time, and the other end of the capacitor C6 is also connected to the GND end of the lithium battery protection chip U4, The common connection terminal of the resistor R26 and the capacitor C7, the other end of the resistor R26 is also connected to the port 12 of the NAND gate U5, and the other end of the capacitor C7 is connected to the port 4 of the optocoupler U9 and the optocoupler U Port 4 of 15; the port 1 and port 11 of the NAND gate U5 are connected, the port 10 and port 13 of the NAND gate U5 are connected, the resistor R28 is connected in series between the ports 7 and 8 of the NAND gate U5, and the NAND gate U5 The ports 5, 6 and 7 of the NAND gate U5 are connected to the ports 8 and 9 of the NAND gate U5. The port 8 of the NAND gate U5 is also connected to one end of the resistor R29, and the other end of the resistor R29 is connected to the drains of the MOS transistors T1 and T2 at the same time. The port 3 of the gate U5 is also connected to one end of the resistor R27, the other end of the resistor R27 is connected to the gates of the MOS transistors T1 and T2 at the same time, the port 14 of the NAND gate U5 is also connected to one end of the resistor R25, and the other end of the resistor R25 is connected to the photocoupler at the same time. Port 2 of U9 and U15, resistor R30 and resistor R31 are connected in series, the floating end of resistor R30 is connected to port 3 of photocoupler U18, the floating end of resistor R31 is connected to the source of MOS transistors T3 and T4, resistor R30 and resistor R31 The common connection terminals of MOS transistors T3 and T4 are connected at the same time; the drains of MOS transistors T1-T4 are connected, and the sources of MOS transistors T1-T2 are connected to the port 5 of the NAND gate and the port of the lithium battery protection chip U4 at the same time. GND, the port 2 of the optocoupler U18 and the port 2 of the optocoupler U12; the port 4 of the optocoupler U9 is connected to the port 4 of the optocoupler U15, and the port 3 of the optocoupler U9 is connected to the optocoupler U10. Port 4 is connected, port 3 of optocoupler U15 is connected to port 4 of optocoupler U16, port 3 of optocoupler U10 is connected to port 4 of optocoupler U11, port 3 of optocoupler U16 is connected to optocoupler U17 The port 4 of the optocoupler U11 is connected to the port 4 of the optocoupler U12, the port 3 of the optocoupler U17 is connected to the port 4 of the optocoupler U18; the emitter and the collector of the transistor U21 are connected in turn. Resistor R1 and resistor RA3 are connected in series, resistor R2 and resistor R7 are connected in series between the emitter and base of transistor U21; resistor RA4 is connected in series between the base of transistor U21 and the collector of transistor U22, the base of transistor U21 and transistor U22 The resistor R8 is connected in series between the emitters of the transistor U22, the resistors R13 and R14 are connected in series between the emitter and the base of the transistor U22; the resistor RA5 is connected in series between the base of the transistor U22 and the collector of the transistor U23, and the base and the transistor of the transistor U22 are connected in series. Resistor R15 is connected in series between the emitters of U23, resistors R16 and R35 are connected in series between the emitter and base of transistor U23; resistor RA6 is connected in series between the base of transistor U23 and the collector of transistor U24, the base of transistor U23 and the A resistor R32 is connected in series between the emitters of the transistor U24, resistors R33 and R34 are connected in series between the emitter and the base of the transistor U24, and the base of the transistor U24 is also connected to the port 2 of the optocoupler U12, and the common connection terminals of R1 and RA3 , U21 base and common connection terminal of RA4 , the common connection end of U22 base electrode and RA5, and the common connection end of U23 base electrode and RA6 are connected to port 4, port 3, port 2, and port 1 of interface P1 in turn.

Diodes Q1, Q3, Q4 and Q2 are connected in series between the drains and sources of the MOS transistors T1-T4, and the anodes of the diodes Q1, Q3, Q4 and Q2 are all connected to the source of the MOS transistors.

The combination of Figure 5 and Figure 6 is a complete 12V lithium battery pack protection circuit with balanced charging capability. This embodiment is a specific implementation circuit scheme designed based on the design idea of Embodiment 1. Figures 5 and 6 The same network label represents the same signal, which means they are connected. The lithium battery protection chip U1-U4 is FS361A, the NAND gate U5 is HEF4011, the photocoupler is PC317, the transistor is AZ431, the diode is IRFB3607, and the resistance of R3-R6 is 510 ohms , the resistance of R9-R12 is 102 ohms, the resistance of R17-R24 is 103 ohms, the resistance of R26 and R27 is 105 ohms, the resistance of R30 and R31 is 105 ohms, the value of R25 is 510 ohms, and the value of C3-C7 is 0.1 U, the value of RA3-RA5 is 510 ohms, R1, R3, R15, and R32 are all 473 ohms, and R2, R13, R16, and R33 are 102 ohms.

The result of all outputs 'or' of OC in this scheme is used to control the charging control of the MOS tube, which are U15_1, U16_1, U17_1, U18_1 respectively. Refer to U15_1, U16_1, U17_1, U18_1 in Figure 6 as long as they are higher than the corresponding B2, B3, B4 ,B- When the voltage is high, the optocoupler can be turned on, and then R25_1 and R30_2 can be turned on. Referring to Figure 5, R30_2 is connected to R31_2 through a resistor R30. Referring to Figure 6, R31_2 controls the charging MOS tube. R25_1 is connected to the 14-pin VDD of the NAND gate HEF4011, which is always in a high level state.

In this scheme, the result of 'and' of all OD outputs is used to control the discharge control of the MOS tube. The OD outputs are U9_1, U10_1, U11_1, U12_1 respectively. Refer to U9_1, U10_1, U11_1, U12_1 in Figure 5 as long as they are higher than the corresponding B2, When the voltage of B3, B4, B- is high, the optocoupler can be turned on, and then R25_1 and U12_3 can be turned on. Referring to Fig. 5, U12_3 is connected to B- through resistor R26, and is low level. U12_3 is connected to pin 12 of HEF4011, pin 13 of HEF4011 is connected to U5_13, and U5_13 is connected to pin 10 of U5 as shown in Figure 6. Referring to the HEF4011 data sheet, U5 pin 10 is the NAND gate output of U5 pin 8 and U5 pin 9 input. Referring to the connection of U5 in Figure 6, its 8th and 9th pins are connected with B- (low level) through R28, so the 10th and 13th pins of U5 U5_13 are always high level. The 12-pin U12_3 of HEF4011 is low level, so the 11-pin output U5_1 of HEF4011 is low level. In the NAND gate loop of HEF4011 pins 1, 2 and 3, the 3rd pin output R27_1 is high level. Referring to Figure 6, the output pin of R27_1 controls the discharge MOS tube.

Each lithium battery can realize the protection of charging overvoltage, discharging undervoltage, overcurrent, and short circuit, and realize the problem of balanced charging of the whole group of batteries during the charging process. In the design, a single-cell lithium battery protection chip is used to protect the grouped lithium batteries of any number of series, and the whole battery pack protection circuit with balanced charging function is formed. The protection circuit has perfect protection function, stable operation, high cost performance, and balanced charging error. small, below 50mV.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention The protection scope of the utility model, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims (5)

1. A lithium battery pack balanced charge and discharge protection circuit, characterized in that it comprises a control circuit (11), a main circuit (12) and N shunt discharge branches (13), and each shunt discharge branch (13) is The main circuit (12) includes N lithium batteries (1), a MOS tube charging control switch (9) and a MOS tube discharge control switch ( 10), the positive pole of the first lithium battery is the positive pole BAT+, the negative pole of the Nth lithium battery is connected to the source of the MOS tube discharge control switch (10), and the drain of the MOS tube discharge control switch (10) is connected to the MOS tube charging control. The drain of the switch (9), the source of the MOS tube charging control switch (9) is the negative electrode BAT-, and both ends of each lithium battery (1) are connected in parallel with a shunt discharge branch; the control circuit (11) includes N A single-cell lithium battery protection chip (6), an OR gate (7), an AND gate (8), and N overcurrent detection protection resistors (4), a single-cell lithium battery protection chip (6) and a single-cell lithium battery (1 ) one-to-one connection, the VDD port of each lithium battery protection chip (6) is connected to the positive pole of the corresponding lithium battery (1), and the VSS port of each lithium battery protection chip (6) is connected to the corresponding lithium battery (1). Negative, the VM port of each lithium battery protection chip (6) is connected to one end of an overcurrent detection protection resistor (4), and the other end of the overcurrent detection protection resistor (4) is connected to the single-cell lithium battery protection chip (6). The negative pole of the single-cell lithium battery (1), the CO ports of the N single-cell lithium battery protection chips (6) are all connected to the same end of the OR gate (7), and the other end of the OR gate (7) is connected to the MOS tube charging control switch (9). ), the DO ports of the N single-cell lithium battery protection chips (6) are all connected to the same end of the AND gate (8), and the other end of the AND gate (8) is connected to the gate of the MOS tube discharge control switch (10). The CO ports of the single-cell lithium battery protection chips (6) are also connected to the moving terminals of the switches on the corresponding shunt discharge branches (13). 2. A lithium battery pack balanced charge-discharge protection circuit according to claim 1, wherein the source of the MOS tube charging control switch (9) is connected to the anode of the diode D1, and the MOS tube charging control switch (9) is connected to the anode of the diode D1. The drain is connected to the cathode of the diode D1, the source of the MOS tube discharge control switch (10) is connected to the anode of the diode D2, and the drain of the MOS tube discharge control switch (10) is connected to the cathode of the diode D2. 3 . The balanced charge-discharge protection circuit for a lithium battery pack according to claim 1 or 2 , wherein the value of N is a positive integer greater than or equal to 2. 4 . 4. A lithium battery pack balanced charge and discharge protection circuit, characterized in that it includes lithium battery protection chips U1-U4, NAND gate U5, MOS transistors T1-T4, photocouplers U9-U12, photocouplers U15-U18 , triode U21-U24, the OD end of the lithium battery protection chip U1-U4 is sequentially connected to one end of the resistor R17, one end of the resistor R19, one end of the resistor R21 and one end of the resistor R23, the other end of the resistor R17, the other end of the resistor R19, and the other end of the resistor R21 And the other end of the resistor R23 is connected to the port 1 of the photocoupler U9, the port 1 of the photocoupler U10, the port 1 of the photocoupler U11 and the port 1 of the photocoupler U12 in sequence; the OC of the lithium battery protection chip U1-U4 The terminals are sequentially connected to one end of resistor R18, one end of resistor R20, one end of resistor R22 and one end of resistor R24, the other end of resistor R18, the other end of resistor R20, the other end of resistor R22 and the other end of resistor R24 are connected to port 1 of photocoupler U15, photoelectric coupling port 1 of the photocoupler U16, port 1 of the photocoupler U17 and port 1 of the photocoupler U18; a resistor R9 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U1, and the VCC terminal of the lithium battery protection chip U1 also Connect one end of the resistor R3 and one end of the capacitor C3 at the same time, the other end of the resistor R3 is connected to the R+ end, and the other end of the capacitor C3 is connected to the GND end of the lithium battery protection chip U1, the port 2 of the optocoupler U9 and the port 2 of the optocoupler U15; A resistor R10 is connected in series between the CS terminal and the GND terminal of the lithium battery protection chip U2. The VCC terminal of the lithium battery protection chip U2 is also connected to one end of the resistor R4 and one end of the capacitor C4, and the other end of the resistor R4 is connected to the port 2 of the optocoupler U9 at the same time. and the port 2 of the photocoupler U15, the other end of the capacitor C4 is connected to the GND end of the lithium battery protection chip U2, the port 2 of the photocoupler U10 and the port 2 of the photocoupler U16 at the same time; the CS end of the lithium battery protection chip U3 A resistor R11 is connected in series with the GND terminal. The VCC terminal of the lithium battery protection chip U3 is also connected to one end of the resistor R5 and one end of the capacitor C5, and the other end of the resistor R5 is connected to the port 2 of the optocoupler U10 and the port 2 of the optocoupler U16. The other end of the capacitor C5 is simultaneously connected to the GND end of the lithium battery protection chip U3, the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17; the resistance R12 is connected in series between the CS end and the GND end of the lithium battery protection chip U4, The VCC end of the lithium battery protection chip U4 is also connected to one end of the resistor R6 and one end of the capacitor C6, the other end of the resistor R6 is connected to the port 2 of the photocoupler U11 and the port 2 of the photocoupler U17 at the same time, and the other end of the capacitor C6 is also connected to the lithium battery protection. The GND terminal of the chip U4, the common connection terminal of the resistor R26 and the capacitor C7, the other end of the resistor R26 is also connected to the port 12 of the NAND gate U5, and the other end of the capacitor C7 is connected to the port 4 of the optocoupler U9 and the optocoupler The port 4 of the combiner U15; the port 1 of the NAND gate U5 is connected to the port 11, the port 10 of the NAND gate U5 is connected to the port 13, the resistor R28 is connected in series between the ports 7 and 8 of the NAND gate U5, and the NAND The ports 5, 6 and 7 of the gate U5 are connected, the ports 8 and 9 of the NAND gate U5 are connected, the port 8 of the NAND gate U5 is also connected to one end of the resistor R29, and the other end of the resistor R29 is connected to the drains of the MOS transistors T1 and T2 at the same time. The port 3 of the NAND gate U5 is also connected to one end of the resistor R27, the other end of the resistor R27 is connected to the gates of the MOS transistors T1 and T2 at the same time, the port 14 of the NAND gate U5 is also connected to one end of the resistor R25, and the other end of the resistor R25 is also connected to the photoelectric The port 2 of the coupler U9 and U15, the resistor R30 and the resistor R31 are connected in series, the floating end of the resistor R30 is connected to the port 3 of the optocoupler U18, the floating end of the resistor R31 is connected to the source of the MOS transistors T3 and T4 at the same time, and the resistors R30 and The common connection terminal of the resistor R31 is connected to the gates of the MOS transistors T3 and T4 at the same time; the drains of the MOS transistors T1-T4 are all connected, and the sources of the MOS transistors T1-T2 are connected to the port 5 of the NAND gate and the lithium battery protection chip U4 at the same time port GND of the optocoupler U18 and port 2 of the optocoupler U12; the port 4 of the optocoupler U9 is connected to the port 4 of the optocoupler U15, and the port 3 of the optocoupler U9 is connected to the optocoupler Port 4 of U10 is connected, port 3 of optocoupler U15 is connected to port 4 of optocoupler U16, port 3 of optocoupler U10 is connected to port 4 of optocoupler U11, and port 3 of optocoupler U16 is connected to the optocoupler Port 4 of photocoupler U17 is connected to port 4 of photocoupler U11, port 3 of photocoupler U11 is connected to port 4 of photocoupler U12, port 3 of photocoupler U17 is connected to port 4 of photocoupler U18; Resistor R1 and resistor RA3 are connected in series in sequence, and resistor R2 and resistor R7 are connected in series between the emitter and base of transistor U21; resistor RA4 is connected in series between the base of transistor U21 and the collector of transistor U22, the base of transistor U21 and the A resistor R8 is connected in series between the emitters of the transistor U22, resistors R13 and R14 are connected in series between the emitter and the base of the transistor U22; a resistor RA5 is connected in series between the base of the transistor U22 and the collector of the transistor U23, and the base of the transistor U22 The resistor R15 is connected in series with the emitter of the transistor U23, the resistors R16 and R35 are connected in series between the emitter and the base of the transistor U23; the resistor RA6 is connected in series between the base of the transistor U23 and the collector of the transistor U24, and the base of the transistor U23 is connected in series. The resistor R32 is connected in series with the emitter of the transistor U24, the resistors R33 and R34 are connected in series between the emitter and the base of the transistor U24, and the base of the transistor U24 is also connected to the port 2 of the optocoupler U12, and the common of R1 and RA3. Connection, U21 base and common connection of RA4, U22 The base electrode and the common connection end of RA5, the base electrode of U23 and the common connection end of RA6 are sequentially connected to port 4, port 3, port 2, and port 1 of the interface P1. 5. A lithium battery pack balanced charge-discharge protection circuit according to claim 4, wherein diodes Q1, Q3, Q4 and Q2 are connected in series between the drains and sources of the MOS transistors T1-T4 in sequence, and the diodes The anodes of Q1, Q3, Q4 and Q2 are all connected to the source of the MOS transistor.

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