Battery management system and emergency charging circuit thereof

Abstract

The invention discloses an emergency charging circuit and system of a battery management system. The circuit comprises a constant current module and an electricity supplement control switch. The constant current module provides a constant electricity supplementing current; the input end of the constant current module is connected with a common connection point of a charging and discharging switch tube of the BMS; and an output loop of the charging control switch is connected in series between the negative electrode of the charging end and the output end of the constant current module, and a control loop is connected with a controller of the BMS. When the controller does not send out a disconnection signal, the charging control switch is switched on by default, a constant-current bypass charging path which bypasses the charging switch tube and passes through the circuit from the negative electrode of the charging end to the common connection point is automatically formed, and the problem that the battery cannot be charged after being subjected to over-discharge'deadlock 'is effectively solved. According to the invention, fault safety type automatic wakeup is realized, and the charging process is safe, intelligent and reliable.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and more specifically to an emergency power replenishment circuit for a battery management system and a battery management system including the circuit. Background Technology

[0002] During use or storage, lithium battery packs may experience excessive voltage drops due to self-discharge or minor loads, even falling below the undervoltage lockout threshold of their protection board. Once the battery voltage is too low, the main charging switch in the battery management system will fail to conduct properly due to insufficient drive voltage, resulting in a "lockdown" state that prevents conventional chargers from charging the battery. In such cases, it is often necessary to disassemble the battery pack for individual cell activation or use special equipment, a cumbersome process that poses safety hazards.

[0003] Existing technologies include some pre-charging or wake-up circuits, but these typically require the system controller to be in normal working order to trigger and cannot automatically activate when the system is completely powered off or experiences a deep fault. Therefore, there is an urgent need for a circuit solution that can automatically and safely provide emergency power to the battery even when the battery management system's main controller fails or there is no control signal. Summary of the Invention

[0004] (a) Purpose of the invention To address the aforementioned technical problems, this invention aims to provide an emergency charging circuit and system for a battery management system. This circuit can automatically establish a safe, constant-current bypass charging path when the system's main controller fails or does not issue a command, providing an initial wake-up current for over-discharged batteries, breaking the "deadlock" state, and thus restoring the battery's normal rechargeability. Simultaneously, this circuit should be reliably shut off during normal system operation without affecting the main circuit function.

[0005] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an emergency power replenishment circuit for a battery management system, configured to be connected to the battery management system, and comprising: The constant current module includes an input terminal and an output terminal, wherein the input terminal is electrically connected to the common connection point of the charging switch and the discharging switch of the battery management system; A charging control switch includes a control circuit and a controlled output circuit; the control circuit is used to be electrically connected to the controller of the battery management system to receive a disconnection control signal; the first terminal of the output circuit is electrically connected to the output terminal of the constant current module, and the second terminal of the output circuit is used to be electrically connected to the negative terminal of the charging terminal of the battery management system. The charging switch and the discharging switch are connected in series between the negative terminal of the charging terminal and the negative terminal of the battery terminal, and the connection node of the two constitutes the common connection point. When the disconnection control signal is not received, the output circuit remains on, thereby forming a bypass power supply path from the negative terminal of the charging terminal through the power supply control switch, the constant current module to the common connection point.

[0006] Furthermore, the constant current module may include a constant current diode.

[0007] Furthermore, the constant current module includes a constant current source circuit composed of discrete components.

[0008] Furthermore, it also includes a first indicator light, which is connected in parallel with the constant current module.

[0009] Furthermore, the emergency power supply circuit also includes a voltage setting module, which is connected in series with the constant current module to set a power supply limit voltage threshold. When the battery voltage is higher than this threshold, the bypass power supply path is automatically disconnected due to the cutoff of the voltage setting module.

[0010] Furthermore, the voltage setting module is one of a TVS diode, a Zener diode, or a voltage reference source.

[0011] Furthermore, it also includes a second indicator light, which is connected in parallel with the series circuit of the constant current module and the voltage setting module.

[0012] Furthermore, the power supply control switch includes a normally closed solid-state relay.

[0013] In a second aspect, the present invention provides a battery management system, including a controller, a charging switch, a discharging switch, and an emergency power replenishment circuit as described above; The signal output terminal of the controller is electrically connected to the control circuit of the power supply control switch. The charging switch and the discharging switch are connected in series between the negative terminal of the charging terminal and the negative terminal of the battery terminal, and their common connection point is electrically connected to the constant current module. The second terminal of the solid-state relay output circuit of the emergency power supply circuit is electrically connected to the negative terminal of the charging terminal.

[0014] Furthermore, the controller is configured to continuously send the disconnect control signal to the charging control switch to cut off the bypass charging path when the battery management system is operating normally.

[0015] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: Fail-safe and automatic wake-up: The core lies in using normally closed solid-state relays as the power replenishment control switch. When the BMS system is not powered on, the controller malfunctions, or there is no active intervention, the relay output circuit remains conductive by default, and an emergency power replenishment path is automatically established. Once an external charger is connected, it can automatically replenish the over-discharged battery with a small current, achieving "passive wake-up" and fundamentally solving the problem of deep undervoltage lock-up.

[0016] Safe and reliable charging: The constant current source technology limits the charging current, effectively avoiding potential safety hazards such as overheating, short circuits, and explosions during the charging process. At the same time, the small current charging causes minimal damage to the chemical system of the battery cell, avoiding secondary damage.

[0017] Automatic Diagnosis and Protection: A charging voltage threshold is set by adding a TVS diode and Zener diode voltage setting module. Charging automatically stops when the battery voltage reaches this threshold. LED indicator lights are also added to monitor and diagnose the charging status, ensuring effective supervision of the entire charging process.

[0018] Intelligent management: When the system is working normally, the controller will continuously send signals to disconnect the emergency circuit so as not to affect the charging and discharging performance of the main circuit.

[0019] Economy and Convenience: The circuit structure is simple, with minimal cost increase. The emergency power supply module can be integrated as an independent module with various BMS topologies without requiring additional power. Even when the battery pack has zero voltage, the emergency power supply module can still function normally when connected to an external charger, eliminating the need for complex isolated power supply modules. Users or maintenance personnel can simply connect a regular charger for automatic repair without disassembly, greatly improving the user experience and after-sales maintenance efficiency. Attached Figure Description

[0020] Figure 1 This is a block diagram of the battery management system of the present invention.

[0021] Figure 2 This is a schematic diagram of the emergency power replenishment circuit in an embodiment of the present invention (the constant current module uses a constant current diode).

[0022] Figure 3 for Figure 2 A schematic diagram of the bypass power supply path for the emergency power supply circuit. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 See Figure 1 and Figure 2This embodiment provides an emergency power supply circuit 100, including a constant current diode DI1, a TVS diode TVS1, and a normally closed solid-state relay SSR. The specific connection relationships are as follows: The constant current diode DI1 has an anode and a cathode. The first terminal of the bidirectional TVS diode TVS1 is connected to the anode of the constant current diode DI1, and the second terminal (K) is used to connect to the common connection point CS_D of the BMS. The control circuit (pins 1, 2) of the normally closed solid-state relay SSR is used to connect to the controller MCU of the BMS. In its output circuit (pins 3, 4), pin 3 is connected to the cathode of the constant current diode DI1, and pin 4 is used to connect to the negative charging terminal P- of the BMS.

[0025] In a BMS, the charging switch (including parallel QC1, QC2 and other MOSFETs) and the discharging switch (including parallel QD1, QD2 and other MOSFETs) are connected in series between the negative terminal P- of the charging terminal and the negative terminal B- of the battery terminal. The connection node is the common connection point CS_D.

[0026] Among them, the constant current diode DI1 serves as a constant current module, used to provide an approximately constant replenishment current to the emergency power replenishment circuit.

[0027] Working principle: When the battery is severely depleted (e.g., less than 6V), the BMS loses power and cannot function properly. Because of the power loss, the controller MCU fails to send a high-level disconnect signal to the SSR, and the SSR's output circuit (3-4) remains in the default on state. If an external charger is connected between the positive terminals P+ and P- at this time, a bypass charging path for emergency power replenishment is formed: P+ → Battery (including cells BT2, BT1, etc. connected in series) → Body diode of the discharge switch → CS_D → TVS1 → DI1 (anode → cathode) → SSR (pins 4 → 3) → P-, as shown below. Figure 3 As shown by the arrow path. Since the charging switch and discharging switch are turned off due to the low battery voltage, the current bypasses the charging switch and flows through the body diode of the discharging switch to the negative terminal B- of the battery, thereby providing a constant and safe wake-up charging current for batteries BT1 and BT2.

[0028] Changing the specifications of the constant current diode can alter the magnitude of the emergency power supply current.

[0029] When the battery voltage reaches the BMS startup voltage (e.g., greater than 6V), the BMS starts normally. The controller MCU continuously sends a disconnect signal to the SSR to cut off the bypass, and the system switches to the normal charging and discharging mode.

[0030] TVS diode TVS1 is the preferred design. TVS diode TVS1 acts as a voltage setting module, used to set a charging voltage threshold. Specifically, the charging voltage = charger voltage - TVS diode voltage. When the battery pack voltage rises to the charging voltage threshold, the bidirectional TVS diode TVS1 automatically turns off due to insufficient forward voltage, thus automatically disconnecting the bypass charging path.

[0031] In this application, the voltage setting module can also use devices or circuit modules such as Zener diodes and voltage reference sources. The maximum current allowed through its bypass charging path is limited by the constant current capability of the constant current diode (the constant current diode can output a constant current over a wide voltage range), i.e., the charging current.

[0032] In this application, the constant current diode limits the charging current to a safe range (e.g., 100mA-1000mA), providing slow and safe charging to the battery with a small current, avoiding thermal runaway or cell damage caused by large current surges. Charging gradually increases the battery voltage.

[0033] In specific embodiments, the constant current module can also be a constant current module composed of discrete components, such as transistor constant current circuits, Zener diode constant current circuits, operational amplifier constant current circuits, etc., which are commonly known. These circuits are low in cost and their working principle is exactly the same as that of Embodiment 1, but they can provide more accurate and stable compensation current.

[0034] Solid-state relays (SSRs) are the preferred power supply control switches due to their advantages such as convenient control, high isolation, and small size. Power supply control switches can also be conventionally designed using ordinary relays, contactors, or manual push-button switches.

[0035] Power supply diagnostics: In this embodiment, to check the charging status, an indicator light GLED is connected in parallel with the constant current diode DI1, and an indicator light RLED is connected in parallel with the constant current diodes DI1 and TVS1 connected in series.

[0036] When the indicator light GLED is lit, it means that the battery is being charged. Simultaneously, as the battery voltage gradually increases, the brightness of the GLED will gradually dim. If the GLED remains constantly lit, it indicates that the battery cell is damaged and cannot be restored by charging.

[0037] A lit RLED indicator light indicates a power supply malfunction. The status of the GLED indicator light can be used for troubleshooting.

[0038] Example 2 See Figure 1This embodiment provides a battery management system including the aforementioned emergency power supply circuit 100. The system includes a controller (MCU) 400, a charging switch 300, a discharging switch 200, and the emergency power supply circuit 100 as described in Embodiment 1. The controller MCU is programmed to always disconnect the SSR when the battery voltage returns to a safe level and the system is performing normal charging and discharging functions.

[0039] It should be noted that the above embodiments are only used to explain the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and scope defined by the claims should be included within the protection scope of the present invention.

Claims

1. An emergency power replenishment circuit for a battery management system, characterized in that, Configured to connect to the battery management system, and includes: The constant current module includes an input terminal and an output terminal, wherein the input terminal is electrically connected to the common connection point of the charging switch and the discharging switch of the battery management system; A charging control switch includes a control circuit and a controlled output circuit; the control circuit is used to be electrically connected to the controller of the battery management system to receive a disconnection control signal; the first terminal of the output circuit is electrically connected to the output terminal of the constant current module, and the second terminal of the output circuit is used to be electrically connected to the negative terminal of the charging terminal of the battery management system. The charging switch and the discharging switch are connected in series between the negative terminal of the charging terminal and the negative terminal of the battery terminal, and the connection node of the two constitutes the common connection point. When the disconnection control signal is not received, the output circuit remains on, thereby forming a bypass power supply path from the negative terminal of the charging terminal through the power supply control switch, the constant current module to the common connection point.

2. The emergency power supply circuit according to claim 1, characterized in that, The constant current module includes a constant current diode.

3. The emergency power supply circuit according to claim 1, characterized in that, The constant current module includes a constant current source circuit composed of discrete components.

4. The emergency power supply circuit according to claim 1, characterized in that, It also includes a first indicator light, which is connected in parallel with the constant current module.

5. The emergency power supply circuit according to claim 1, characterized in that, It also includes a voltage setting module, which is connected in series with the constant current module to set a charging limit voltage threshold. When the battery voltage is higher than this threshold, the bypass charging path is automatically disconnected due to the cutoff of the voltage setting module.

6. The emergency power supply circuit according to claim 5, characterized in that, The voltage setting module is one of a TVS diode, a Zener diode, or a voltage reference source.

7. The emergency power supply circuit according to claim 5, characterized in that, It also includes a second indicator light, which is connected in parallel with the series circuit of the constant current module and the voltage setting module.

8. The emergency power supply circuit according to claim 1, characterized in that, The power supply control switch includes a normally closed solid-state relay.

9. A battery management system, characterized in that, Includes a controller, a charging switch, a discharging switch, and an emergency power supply circuit as described in any one of claims 1 to 8; The signal output terminal of the controller is electrically connected to the control circuit of the power supply control switch. The charging switch and the discharging switch are connected in series between the negative terminal of the charging terminal and the negative terminal of the battery terminal, and their common connection point is electrically connected to the constant current module. The second terminal of the solid-state relay output circuit of the emergency power supply circuit is electrically connected to the negative terminal of the charging terminal.

10. The battery management system according to claim 9, characterized in that, The controller is configured to continuously send the disconnect control signal to the charging control switch to cut off the bypass charging path when the battery management system is working normally.

Images