Cascade lithium battery low power consumption circuit

Abstract

The utility model relates to the technical field of lithium battery protection, in particular to a cascade lithium battery low-power-consumption circuit, which comprises at least one group of battery protection control units, more than two groups of battery protection control units are connected in a cascade mode, and each group of battery protection control units is composed of a battery module and a protection control circuit. The protection control circuit comprises a voltage sampling module, a driving control module and a battery protection chip U1; the driving control module comprises a charging control circuit and a discharging control circuit, all the discharging control circuits before the last stage comprise optical couplers U2, and the discharging control end DOUT of the battery protection chip U1 is connected to the grounding connection end VSS of the battery protection chip U1 through a current limiting resistor R17, a photodiode of the optical couplers U2 and an energy storage capacitor C19 in sequence; the master control circuit comprises a charging loop and a discharging loop; the final-stage discharge control circuit comprises an MOS tube Q2; and an under-voltage locking module is arranged at the output end of the master control circuit and comprises an optical coupler U4.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery protection technology, and in particular to a low-power circuit for cascaded lithium batteries. Background Technology

[0002] With the widespread application of lithium batteries in energy storage systems, electric vehicles and other fields, the design of protection circuits for multi-cell cascaded lithium battery packs faces severe challenges. Traditional cascaded lithium battery protection circuits usually rely on dedicated protection chips (such as BQ77216) to achieve undervoltage, overvoltage and overtemperature protection, but in practical applications, they have the following defects: (1) When the battery pack enters the undervoltage protection state, the discharge control terminal (DOUT) of the protection chip needs to continuously output a high level to drive the optocoupler, resulting in a small current of about 500-1000 microamps discharging the battery pack. If the battery is stored after the battery undervoltage protection is reached and is not maintained in time, the presence of the small current during long-term storage will accelerate the battery capacity loss and even cause irreversible damage. (2) Traditional circuits lack a stable locking function after undervoltage protection, and the protection state is easily switched repeatedly due to voltage fluctuations and other reasons, affecting the reliability of the system. Utility Model Content

[0003] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0004] Design a low-power cascade lithium battery circuit, including at least one set of battery protection control units, wherein two or more sets of battery protection control units are connected in a cascade manner. Each set consists of a battery module composed of multiple battery packs connected in series and a corresponding protection control circuit. The protection control circuit includes a voltage sampling module, a drive control module, and a battery protection chip U1. The drive control module includes a charging control circuit and a discharging control circuit. The charging control circuit includes an optocoupler U3, which is connected to the charging control terminal COUT of the battery protection chip U1 through a current-limiting resistor R18. All discharging control circuits before the last stage include optocouplers U2. The discharging control terminal DOUT of the battery protection chip U1 is connected to the ground connection terminal VSS of the battery protection chip U1 in sequence through a current-limiting resistor R17, the photodiode of the optocoupler U2, and an energy storage capacitor C19.

[0005] It also includes a master control circuit for receiving protection signals from the battery protection control unit, which includes a charging circuit connected between the battery module and the charger and a discharging circuit connected between the battery module and the load. The charging control circuit and the discharging control circuit are respectively connected to the signal input terminals of the charging circuit and the discharging circuit.

[0006] The final stage discharge control circuit includes a MOSFET Q2, whose gate is connected to the discharge control terminal DOUT of the battery protection chip U1 through a current-limiting resistor R17, and whose drain and source are connected to the signal input terminal of the main control circuit, respectively.

[0007] The output terminal of the main control circuit is equipped with an undervoltage lockout module, which includes an optocoupler U4. The collector of the transistor of the optocoupler U4 is connected between the positive terminal of the battery module and the resistor R20 through the resistor R21, and the emitter is connected to the signal input terminal of the discharge circuit. The anode of the photodiode of the optocoupler U4 is connected to the output terminal of the discharge circuit through the resistor R30, and the cathode is connected to the negative discharge terminal of the battery module.

[0008] Preferably, the voltage sampling module consists of multiple sampling resistors and multiple filter capacitors connected in series with each of them. One end of each sampling resistor is connected to the positive terminal of the corresponding battery pack, and the other end is input to the sampling terminal of the battery protection chip U1. Each filter capacitor is connected in parallel to both ends of the corresponding battery pack, and the filtered battery voltage is input to the sampling terminal of the battery protection chip U1.

[0009] Preferably, the output terminal of the optocoupler U3 of the first group of battery protection control units is directly connected to the charging control circuit, the output terminal of the optocoupler U2 is directly connected to the discharging control circuit, a terminal J5 is connected to the output terminal of the protection control circuit, and multiple terminals J3 are connected to the input terminal of the main control circuit. Each subsequent group of battery protection control units is connected to the input terminal J3 through the output terminal J5.

[0010] Preferably, each battery module consists of 3-16 battery packs, and each battery pack consists of multiple parallel individual cells.

[0011] Preferably, the sampling terminals V1 to V15 of the battery protection chip U1 are connected to the positive terminals of each battery pack BT1 to BT15 respectively through resistors R1 to R15, and the sampling terminal V16 is shorted to the sampling terminal V15.

[0012] Preferably, the power supply terminal VDD of the battery protection chip U1 is connected to the positive terminal of the battery pack BT15 through a current-limiting resistor R19 and a filter capacitor C16, and the other end of C16 is connected to the negative terminal of the battery pack BAT1 together with the ground connection terminal VSS of the battery protection chip U1.

[0013] Preferably, the charging circuit includes a charging MOSFET Q3, a Zener diode ZD2, and resistors R20 and R22. One end of resistor R20 is connected to the positive terminal of the battery module, and the other end is connected to the cathode of Zener diode ZD2. The anode of Zener diode ZD2 is connected to the negative terminal of the corresponding battery module. The gate of the charging MOSFET Q3 is connected to the cathode of Zener diode ZD2 through resistor R22, the source is connected to the negative terminal of the battery module, and the drain is connected to the negative terminal of the battery module.

[0014] Preferably, the discharge circuit includes discharge MOSFETs Q7 to Q10, voltage divider resistors R24 to R27, and Zener diode ZD1. The gates of the discharge MOSFETs Q7 to Q10 are connected to the Zener diode ZD1 through the corresponding voltage divider resistors R24 to R27. The sources are connected to the negative terminal of the battery module, and the drains are connected to the negative discharge terminal output by the battery module. A resistor R23 connected in parallel with the Zener diode ZD1 is connected to the output terminal of the discharge control circuit and the input terminal of the discharge circuit.

[0015] The beneficial effects of this utility model are as follows:

[0016] 1. This invention increases the rated voltage of the battery pack by increasing the number of battery cascades. When the battery pack operates at high power, the output current decreases, and the internal temperature of the battery itself decreases, ensuring normal operation of the battery pack. Furthermore, the high-voltage design reduces the current demand during high-power output, reduces battery temperature rise, avoids false triggering of over-temperature protection, and improves energy transfer efficiency.

[0017] 2. Through the collaborative design of energy storage capacitor C19 and optocoupler U2, when the battery pack enters the undervoltage protection state, the high-level signal output by the discharge control terminal DOUT of chip U1 charges energy storage capacitor C19 through current limiting resistor R17. During the charging process, optocoupler U2 transmits the protection signal to the main control circuit. The main control circuit cuts off the discharge circuit according to the above signal, thereby realizing the undervoltage protection function. During the charging process of the energy storage capacitor, there will be no discharge phenomenon at the discharge output terminal of battery protection chip U1, current limiting resistor R17, diode of optocoupler U2 to the reference ground terminal of this battery module, and no current power consumption to drive optocoupler U2 will be generated, thereby maintaining the low power consumption state of the protection circuit and extending the storage life of the battery in the undervoltage protection state.

[0018] 3. The last stage battery module in the series adopts a MOSFET isolation design. Since the MOSFET is voltage driven, there is no current power consumption issue.

[0019] 4. Implement an undervoltage lockout circuit in the output section of the main control circuit. Once the circuit is undervoltage protected, the protection state will be locked to ensure the stability of the protection state and avoid repeated switching caused by malfunctions due to voltage fluctuations. The protection can only be released after the battery pack is charged to the normal supply voltage, allowing the battery module to continue to supply power normally. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall circuit connection structure of this utility model;

[0021] Figure 2 This is a circuit connection diagram of the battery protection control unit of this utility model;

[0022] Figure 3 This is the overall control circuit connection diagram of this utility model;

[0023] Figure 4 This is the circuit connection diagram of the final-stage battery protection control unit of this utility model;

[0024] Figure 5 This is a schematic diagram of the overall circuit connection structure of multiple cascaded battery protection control units; Detailed Implementation

[0025] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0026] Example 1

[0027] A low-power circuit for cascaded lithium batteries, such as Figures 1 to 3 As shown, it includes a set of battery protection control units, which consists of a battery module composed of 15 battery packs connected in series and a protection control circuit. Each battery pack consists of multiple parallel individual cells. A set of battery modules can provide an output voltage of 54V. The drive control module includes a charging control circuit and a discharging control circuit to realize signal isolation control for charging and discharging. The charging control circuit includes an optocoupler U3, which is connected to the charging control terminal COUT of the battery protection chip U1 through a current-limiting resistor R18. The discharging control circuit includes an optocoupler U2, and the discharging control terminal DOUT of the battery protection chip U1 is connected to the ground connection terminal VSS of the battery protection chip U1 in sequence through a current-limiting resistor R17, the photodiode of the optocoupler U2, and the energy storage capacitor C19.

[0028] When the battery module enters undervoltage protection mode, the discharge control terminal DOUT of the battery protection chip U1 outputs a high-level signal, which charges the energy storage capacitor C19 through R17 and the photodiode of the optocoupler U2. After charging is complete, the optocoupler U2 transmits the protection signal of the battery module to the main control circuit to cut off the discharge circuit and maintain a low-power state. The charging process of the energy storage capacitor C19 only generates transient current when the undervoltage protection is triggered. After charging is complete, it discharges through the discharge circuit: the discharge control terminal DOUT of the battery protection chip U1, diode D2, energy storage capacitor C19, and reference ground.

[0029] It also includes a master control circuit for receiving protection signals from the battery protection control unit. This circuit includes a charging circuit connected between the battery module and the charger, and a discharging circuit connected between the battery module and the load. The charging control circuit and the discharging control circuit are respectively connected to the signal input terminals of the charging circuit and the discharging circuit. Specifically, the collector of the phototransistor of optocoupler U3 is directly connected to the cathode of Zener diode ZD2, and the emitter is directly connected to the anode of Zener diode ZD2. The collector of the phototransistor of optocoupler U2 is directly connected to resistor R23, and the emitter is directly connected to the negative terminal of the battery module. During use... Figure 1 Simply short-circuit pins 1 and 2 of the middle terminal J4.

[0030] The output of the main control circuit is equipped with an undervoltage lockout module, which includes an optocoupler U4. The collector of the transistor in optocoupler U4 is connected between the positive terminal of the battery module and resistor R20 through resistor R21, and the emitter is connected to the cathode of the Zener diode ZD1. The anode of the photodiode in optocoupler U4 is connected to the output of the discharge circuit through resistor R30, and the cathode is connected to the negative terminal of the battery module. The undervoltage lockout module locks the protection state after triggering undervoltage protection until the battery pack is charged to the preset voltage and then unlocked.

[0031] The voltage sampling module consists of sampling resistors R1 to R15 and filter capacitors C1 to C15. One end of the sampling resistors R1 to R15 is connected to the positive terminal of battery packs BT1 to BT15 respectively, and the other end is input to the sampling terminal of battery protection chip U1. The filter capacitors C1 to C15 are connected in parallel to the two ends of battery packs BT1 to BT15 respectively, and the filtered battery voltage is input to the sampling terminal of battery protection chip U1.

[0032] The sampling terminals V1 to V15 of the battery protection chip U1 are connected to the positive terminals of each cell BT1 to BT15 respectively through resistors R1 to R15. The sampling terminal V16 is shorted to the sampling terminal V15. The power supply terminal VDD of the battery protection chip U1 is connected to the positive terminal of the battery pack BT15 through the current limiting resistor R19 and the filter capacitor C16. The other end of C16 is connected to the negative terminal of the battery pack BAT1 together with the ground connection terminal VSS of the battery protection chip U1.

[0033] The charging circuit includes a charging MOSFET Q3, a Zener diode ZD2, and resistors R20 and R22. One end of resistor R20 is connected to the positive terminal of the battery module, and the other end is connected to the cathode of Zener diode ZD2. The anode of Zener diode ZD2 is connected to the corresponding charging negative terminal of the battery module. The gate of charging MOSFET Q3 is connected to the cathode of Zener diode ZD2 through resistor R22. The source is connected to the charging negative terminal of the battery module, and the drain is connected to the negative terminal of the battery module.

[0034] The discharge circuit includes discharge MOSFETs Q7 to Q10, voltage divider resistors R24 to R27, and Zener diode ZD1. The gates of discharge MOSFETs Q7 to Q10 are connected to Zener diode ZD1 through the corresponding voltage divider resistors R24 to R27. The sources are connected to the negative terminal of the battery module, and the drains are connected to the negative discharge terminal output by the battery module. A resistor R23 connected in parallel with Zener diode ZD1 is connected at the output terminal of the discharge control circuit and the input terminal of the discharge circuit.

[0035] Zener diodes ZD2 and ZD1 are used to limit the driving voltage of charging MOSFET Q3 and discharging MOSFETs Q7 to Q10, respectively.

[0036] The working process of this utility model:

[0037] (1) Normal charging and discharging process

[0038] Battery protection chip U1 monitors the voltage of each cell in real time through resistors R1 to R15. If overvoltage or undervoltage is detected, the corresponding MOSFET performs the following actions:

[0039] During normal charging, in this embodiment, an 18V voltage is applied across resistor R22. The battery protection chip U1 detects that the cell voltage is normal, and its charging control terminal COUT outputs a low level. The optocoupler U3 is cut off, and the charging MOSFET Q3 is turned on. The current flows through R20 and ZD2 to provide a driving voltage for the charging MOSFET Q3, and the charging circuit is normally connected.

[0040] During normal discharge, the battery protection chip U1 detects that the output voltage is normal, and its discharge control terminal DOUT outputs a low level. The optocoupler U2 is cut off, and the discharge MOSFETs Q7 to Q10 are turned on under the 18V driving voltage provided by the Zener diode ZD1, so that the battery module discharges normally.

[0041] (2) Overvoltage and undervoltage protection triggering stage

[0042] When overvoltage protection occurs, i.e., when the battery charging voltage reaches the overvoltage protection value, the charging control terminal COUT of U1 outputs a high level, driving the optocoupler U3 to conduct. Then, the Zener diode ZD2 is reverse-broken and conducts. At this time, the voltage across R22 drops to 0V due to the clamping effect of ZD2. The gate voltage of the N-channel charging MOSFET Q3 is pulled low, causing MOSFET Q3 to be turned off. The charging circuit of the battery module is disconnected, i.e., the charging of the battery pack stops, and the battery pack enters the overvoltage protection state.

[0043] During undervoltage protection, when the battery discharge voltage is less than or equal to the undervoltage protection value, the discharge control terminal DOUT of U1 outputs a high level, charging the energy storage capacitor C19 through the current-limiting resistor R17. This drives the optocoupler U2 to conduct, pulling down the drive voltage VGS of the discharge MOSFETs Q7 to Q10. When the drive voltage VGS is lower than its turn-on voltage, the discharge MOSFETs Q7 to Q10 are turned off, thus shutting off the discharge circuit. During the charging process of the energy storage capacitor C19, the battery pack implements the undervoltage protection function. In this embodiment, charging of the energy storage capacitor C19 stops when it reaches 7V. At this time, the battery pack will not discharge through the current-limiting resistor R17, the photodiode of the optocoupler U2, or the reference ground terminal. In this way, the undervoltage protection function is achieved, and the battery pack will not continuously consume approximately 500-1000 microamps of current in the undervoltage state.

[0044] At the same time, the output voltage is 0V, so the current at the photodiode terminal of the resistor R30 connected to the battery pack output and the optocoupler U4 is also 0A; the transistor of the optocoupler U4 is cut off, causing the driving terminals of the discharge MOSFETs Q7, Q8, Q9, and Q10 to lose their voltage source and be cut off, thereby shutting off the discharge circuit and locking the battery pack undervoltage state to ensure the stability of the protection state and avoid malfunctions caused by voltage fluctuations.

[0045] (3) Protection Release Phase

[0046] When the external charger charges the battery pack, the battery pack voltage continuously increases. At this time, the transistor of optocoupler U4 is triggered to conduct, and the battery protection chip U1 is deprotected, so that the driving voltage of the discharge MOSFETs Q7-Q10 is restored and they conduct, and the discharge circuit is reconnected, allowing the battery pack to output normally.

[0047] Example 2

[0048] A low-power circuit for cascaded lithium batteries, such as Figures 1 to 5As shown, the difference from Embodiment 1 is that it includes two or more cascaded battery protection control units, each of which consists of a battery module composed of 15 battery packs connected in series and a protection control circuit. The two cascaded battery modules are used to provide a high voltage output with a rated voltage of 108V or higher. Terminal J5 is connected to the output end of the protection control circuit, and multiple terminals J3 are connected to the input end of the main control circuit. Each battery protection control unit after the second group is connected to the input terminal J3 through the output terminal J5, and outputs the protection signal of the battery module through the output terminal J5. After logical judgment, the charging and discharging of the battery pack is performed globally.

[0049] The final-stage discharge control circuit includes a MOSFET Q2, whose gate is connected to the discharge control terminal DOUT of the battery protection chip U1 via a current-limiting resistor R17. Its drain and source are connected to the signal input terminals of the main control circuit. Specifically, the collector of the phototransistor in the optocoupler U3 is connected to pin 1 of terminal J5, and its emitter is connected to pin 2 of terminal J5. The drain of the MOSFET Q2 is connected to pin 3 of terminal J5, and its source is connected to pin 4 of terminal J5. The cathode and anode of the Zener diode ZD2 are connected to pins 1 and 2 of terminal J3, respectively. The negative terminal of the battery module is connected to pin 4 of J3. The cathode of the Zener diode ZD1 is connected to pin 3 of J3. Figure 2 Pin 2 of J6 and Figure 1 The two pins of J4 are connected accordingly. Figure 2 Pin 1 of J7 and Figure 3 The connection of pin 2 of J8, Figure 3 pin 1 of J8 in Figure 1 The connection of pin 1 of J4, Figure 2 and Figure 3 Terminal J5 in Figure 1 Connect the corresponding terminal J3, and so on, to cascade multiple sets of battery protection control units.

[0050] During undervoltage protection, the charging control terminal COUT of U1 outputs a high level, turning on the MOSFET Q2. Because the MOSFET is voltage-driven, there is no circuit from the gate to the source or drain, and no current flows through resistor R17 to discharge. Therefore, the battery pack will not discharge, and thus there will be no current consumption in the undervoltage state. In this application, the battery protection chip U1 uses the BQ77216 model.

[0051] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A low power consumption circuit for a series connected lithium battery, characterized by The application relates to a battery protection control unit, which comprises at least one group of battery protection control units, wherein two or more groups of battery protection control units are connected in a cascade mode, each group being composed of a battery module composed of a plurality of battery groups connected in series and a corresponding protection control circuit, the protection control circuit comprising a voltage sampling module, a driving control module and a battery protection chip U1; the driving control module comprises a charging control circuit and a discharging control circuit, the charging control circuit comprises an optical coupler U3, the optical coupler U3 is connected to a charging control end COUT of the battery protection chip U1 through a current-limiting resistor R18, all the discharging control circuits before the last stage comprise an optical coupler U2, a discharging control end DOUT of the battery protection chip U1 is sequentially connected to a ground connection end VSS of the battery protection chip U1 through a current-limiting resistor R17, a photodiode of the optical coupler U2 and an energy storage capacitor C19; The application further comprises a general control circuit for receiving protection signals of the battery protection control units, which comprises a charging loop connected between the battery module and a charger and a discharging loop connected between the battery module and a load, and the charging control circuit and the discharging control circuit are respectively connected to signal input ends of the charging loop and the discharging loop; The last-stage discharging control circuit comprises an MOS tube Q2, the gate of the MOS tube Q2 is connected to the discharging control end DOUT of the battery protection chip U1 through a current-limiting resistor R17, and the drain and the source are respectively connected to signal input ends of the general control circuit; An under-voltage lock module is arranged at an output end of the general control circuit, which comprises an optical coupler U4, the collector of the transistor of the optical coupler U4 is connected to the positive pole of the battery module through a resistor R21 and the resistor R20, the emitter is connected to a signal input end of the discharging loop, the anode of the photodiode of the optical coupler U4 is connected to an output end of the discharging loop through a resistor R30, and the cathode is connected to a discharging negative pole of the battery module.

2. The low power consumption circuit for a series connected lithium battery of claim 1, wherein: The voltage sampling module is composed of a plurality of sampling resistors and a plurality of filter capacitors corresponding to the sampling resistors in series, one end of each sampling resistor is respectively connected to the positive pole of the corresponding battery group, the other end is input to the sampling end of the battery protection chip U1, and each filter capacitor is respectively connected in parallel to the two ends of the corresponding battery group and inputs the filtered battery voltage to the sampling end of the battery protection chip U1.

3. The low power consumption circuit for a battery of series connected lithium cells as defined in claim 1, characterized in that: The output end of the optical coupler U3 of the first group of battery protection control units is directly connected to the charging control circuit, the output end of the optical coupler U2 is directly connected to the discharging control circuit, a terminal J5 is connected to the output end of the protection control circuit, a plurality of terminals J3 are connected to the input end of the general control circuit, and each group of battery protection control units after the first group is respectively connected to the input terminal J3 through the output terminal J5.

4. The low power consumption circuit for a battery of series connected lithium cells as defined in claim 1, characterized in that: Each battery module is composed of 3-16 battery groups, and each battery group is composed of a plurality of single cells connected in parallel.

5. The low power consumption circuit for a series connected lithium battery of claim 4, wherein: The sampling ends V1 to V15 of the battery protection chip U1 are respectively connected to the positive poles of the battery groups BT1 to BT15 through the resistors R1 to R15, and the sampling end V16 is short-circuited with the sampling end V15.

6. The low power consumption circuit for a battery of series connected lithium cells as defined in claim 4, wherein: The power supply end VDD of the battery protection chip U1 is connected to the positive pole of the battery pack BT15 through the current-limiting resistor R19 and the filter capacitor C16, and the other end of the C16 is connected to the negative pole of the battery pack BAT1 together with the ground connection end VSS of the battery protection chip U1.

7. The low power consumption circuit for a battery of series connected lithium cells as defined in claim 1, characterized in that: The charging circuit comprises a charging MOS tube Q3, a voltage stabilizing tube ZD2, resistors R20 and R22, one end of the resistor R20 is connected to the positive pole of the battery module, the other end is connected to the cathode of the voltage stabilizing tube ZD2, the anode of the voltage stabilizing tube ZD2 is connected to the charging negative pole of the corresponding battery module, the gate of the charging MOS tube Q3 is connected to the cathode of the voltage stabilizing tube ZD2 through the resistor R22, the source is connected to the charging negative pole of the battery module, and the drain is connected to the negative pole of the battery module.

8. The low power consumption circuit for a battery of series connected lithium cells as defined in claim 1, characterized by: The discharging circuit comprises discharging MOS tubes Q7 to Q10, voltage dividing resistors R24 to R27, and a voltage stabilizing tube ZD1, the gates of the discharging MOS tubes Q7 to Q10 are connected to the voltage stabilizing tube ZD1 through the corresponding voltage dividing resistors R24 to R27, the sources are commonly connected to the negative pole of the battery module, the drains are commonly connected to the discharging negative pole of the output of the battery module, and the resistor R23 connected in parallel with the voltage stabilizing tube ZD1 is connected between the output end of the discharging control circuit and the input end of the discharging circuit.

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