Power protection circuit for rechargeable battery

Abstract

The utility model discloses a power supply protection circuit for a rechargeable battery. The power supply protection circuit comprises a power supply bus, a discharge switch unit and a current-limiting resistor, wherein the discharge switch unit and the current-limiting resistor are connected in series on the power supply bus; the short-circuit protection circuit comprises a voltage detection unit and a comparison unit; the input end of the voltage detection unit is connected with the two ends of the current-limiting resistor. The two input ends of the comparison unit are connected with the controller and the output end of the voltage detection unit respectively so as to receive the real-time voltage detected by the voltage detection unit and the reference voltage output by the controller, and the controller provides the pre-configuration and adjustment functions of the reference voltage; the output end of the comparison unit is connected with the discharge switch circuit so as to control the discharge switch unit to be in an open state or a closed state according to the magnitude relation between the real-time voltage and the reference voltage. According to the power supply protection circuit, the protection threshold value can be dynamically adjusted according to the capacitance value or the inductance characteristic of the capacitive, inductive or resistive load, and the contradiction that power-on cannot be ensured due to short circuit caused by parameter solidification in a traditional scheme is avoided.

Description

Technical Field

[0001] This utility model relates to the field of short circuit protection technology, and in particular to a power protection circuit for rechargeable batteries. Background Technology

[0002] With the rapid development of lithium battery technology, the types of loads it supplies are becoming increasingly diversified, mainly including three categories: capacitive loads (such as inverters, energy storage devices, and portable speakers), inductive loads (such as electric vehicles and lawnmower motors), and resistive loads (such as heating wires and soldering irons). Among these, capacitive loads pose a significant challenge to the short-circuit protection performance of the battery management system (BMS): load devices, such as inverters, can have built-in capacitors as high as 30,000-50,000 μF, and the peak current generated at power-on can reach 2,000-3,000 A. This instantaneous high current can easily trigger malfunctions in traditional protection circuits and even damage the discharge switch MOS device, thereby threatening battery safety.

[0003] Currently, mainstream short-circuit protection solutions mainly rely on analog front-end (AFE) chips or external hardware operational amplifiers. The former triggers MOS shutdown protection by setting a preset current threshold and delay time, while the latter achieves protection by detecting the current signal in real time and comparing it with a fixed reference value. However, both solutions have significant drawbacks: firstly, the threshold and delay parameters of the AFE chip are fixed and cannot dynamically adapt to the characteristics of loads with different capacitance values; secondly, the reference voltage of the hardware operational amplifier solution cannot be configured at the client end, making it difficult to balance protection sensitivity with the power-on requirements of capacitive loads. Especially when dealing with large-capacity capacitive loads, traditional solutions often fall into the dilemma of "false triggering of protection" and "surge current impacting the MOS," which may ultimately lead to battery system failure or safety hazards. Utility Model Content

[0004] The purpose of this invention is to provide a power protection circuit for rechargeable batteries that can dynamically adjust protection parameters to cope with various complex application scenarios, thereby solving the above-mentioned technical problems.

[0005] To achieve the above objectives, this utility model provides a power protection circuit for rechargeable batteries, comprising:

[0006] The power bus has one end connected to the main electrode of the battery to be protected, and the other end used to connect to the load.

[0007] A discharge switch unit and a current-limiting resistor are connected in series on the power bus;

[0008] A short-circuit protection circuit includes a voltage detection unit and a comparison unit; the input terminal of the voltage detection unit is connected to both ends of the current-limiting resistor and is used to detect the voltage across the current-limiting resistor.

[0009] The two input terminals of the comparison unit are respectively connected to the output terminals of the controller and the voltage detection unit to receive the real-time voltage detected by the voltage detection unit and the reference voltage output by the controller, and the controller provides the pre-configuration and adjustment function of the reference voltage;

[0010] The output terminal of the comparison unit is connected to the discharge switch circuit to control the discharge switch unit to be in an open or closed state according to the relationship between the real-time voltage and the reference voltage. In the open state, the discharge circuit on the power bus is disconnected, and in the closed state, the discharge circuit on the power bus is connected.

[0011] Preferably, the controller is also connected to the output terminals of the discharge switch unit and the comparison unit, so that the controller can lock the discharge switch unit in an open or closed state according to the output of the comparison unit.

[0012] Preferably, the voltage detection unit includes an operational amplifier, the non-inverting and inverting inputs of which are respectively connected to the two ends of the current-limiting resistor, and the output of the operational amplifier is connected to the input of the comparison unit.

[0013] Preferably, a feedback resistor is provided between the output terminal and the inverting terminal of the operational amplifier.

[0014] Preferably, the output terminal of the operational amplifier is further provided with a first RC filter circuit.

[0015] Preferably, the comparison unit includes a voltage comparator, the two input terminals of which are respectively connected to the controller and the voltage detection unit, and the output terminal of which is connected to the discharge switch unit.

[0016] Preferably, the output of the voltage comparator is further provided with a second RC filter circuit.

[0017] Preferably, it also includes a power supply unit, the input of which is connected to the battery, and the output of which is connected to the controller and the short-circuit protection circuit.

[0018] Compared with the prior art, the power protection circuit disclosed in the above-mentioned technical solution of this utility model includes a short-circuit protection circuit composed of a voltage detection unit and a comparison unit. The voltage detection unit detects the real-time voltage across the current-limiting resistor on the power bus and transmits it to the comparison unit. The comparison unit outputs a control signal based on the comparison between the real-time voltage and the reference voltage provided by the controller, thereby controlling the state of the discharge switch unit and thus meeting the safety current requirements on the power bus during power-on or discharge. Since the controller provides an adjustable reference voltage, the protection threshold can be dynamically adjusted according to the capacitance or inductance characteristics of capacitive, inductive, or resistive loads, avoiding the contradiction of "protecting against short circuits but not against power-on" caused by the fixed parameters in traditional solutions. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the power protection circuit in an embodiment of this utility model.

[0020] Figure 2 This is a schematic diagram of the short-circuit protection circuit in an embodiment of this utility model. Detailed Implementation

[0021] To explain in detail the technical content, structural features, objectives and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0022] This embodiment discloses a power protection circuit for rechargeable batteries to protect the load circuit of the rechargeable battery from overcurrent surges during power-on or discharge. Figure 1 and Figure 2 The power protection circuit includes a power bus L, a discharge switch unit 3, a current limiting resistor 2, and a short-circuit protection circuit 1.

[0023] The power bus L serves as the main channel for power transmission, connecting the battery BT to the load and enabling power to be transferred from the battery BT to the load. The power bus L uses copper wire, which has excellent conductivity and can carry a large current. One end of the power bus L is connected to the main electrode of the battery BT to be protected, and the other end is connected to the load via an interface.

[0024] Discharge switch unit 3 is connected in series on the power bus L to control the on / off state of the discharge current on the power bus L. Discharge switch unit 3 uses a metal-oxide-semiconductor field-effect transistor (MOSFET). Upon receiving a control signal, discharge switch unit 3 can quickly switch its switching state to achieve circuit on / off control. Additionally, charging switch unit 4 can be connected in series on the power bus L.

[0025] The current-limiting resistor 2 is connected in series with the power bus L and in series with the discharge switch unit 3. The current-limiting resistor 2 is a precision resistor that can withstand a large current. The function of the current-limiting resistor 2 is to generate a voltage drop when current flows through it. This voltage drop is proportional to the current flowing through it. By detecting the voltage across the current-limiting resistor 2, the magnitude of the current in the circuit can be indirectly measured.

[0026] The short-circuit protection circuit 1 includes a voltage detection unit 10 and a comparison unit 11. The input terminal of the voltage detection unit 10 is connected to the current-limiting resistor 2 and is used to detect the voltage across the current-limiting resistor 2.

[0027] The two input terminals of the comparison unit 11 are connected to the output terminals of the controller MCU and the voltage detection unit 10, respectively, to receive the real-time voltage VX detected by the voltage detection unit 10 and the reference voltage DAC output by the controller MCU. The controller MCU provides the pre-configuration and adjustment functions of the reference voltage DAC.

[0028] The output of comparator unit 11 is connected to the discharge switch circuit to control the discharge switch unit 3 to be in an open or closed state based on the relationship between the real-time voltage VX and the reference voltage DAC. In the open state, the discharge circuit on the power bus L is disconnected. In the closed state, the discharge circuit on the power bus L is connected.

[0029] The working principle of the power protection circuit in this embodiment is as follows:

[0030] The voltage detection unit 10 continuously monitors the voltages V1 and V2 across the current-limiting resistor 2 on the power bus L, and generates a real-time voltage VX based on the difference between V2 and V1. This real-time voltage VX is then transmitted to the comparison unit 11. The comparison unit 11 outputs a control signal VSCP based on the comparison between the real-time voltage VX and the reference voltage DAC provided by the controller MCU, thereby controlling the state of the discharge switch unit 3 to meet the safety current requirements on the power bus L during power-on or discharge. For example, when the real-time voltage VX is greater than the reference voltage DAC, the comparison unit 11 outputs a low level to control the discharge switch unit 3 to be in the open state, disconnecting the discharge circuit on the power bus L. When the real-time voltage VX is less than the reference voltage DAC, the comparison unit 11 outputs a high level to control the discharge switch unit 3 to be in the closed state, connecting the discharge circuit on the power bus L.

[0031] Because the controller MCU provides an adjustable reference voltage DAC, the protection threshold can be dynamically adjusted according to the capacitance or inductance characteristics of capacitive, inductive, or resistive loads. This avoids the contradiction of traditional solutions that "protect against short circuits but not against power-on" due to fixed parameters. For example, for inverters with capacitive loads up to 50,000 μF, lowering the reference voltage DAC threshold can prevent false triggering of the protection against a 3,000 A surge at power-on while maintaining sensitive response during short circuits. This configurable protection mechanism allows the battery BT management system to adapt to the power-on characteristics of different types of loads while ensuring short-circuit protection. Especially for large-capacity capacitive loads, it can prevent false triggering of protection and effectively prevent surge current from impacting MOS devices, thus improving the safety and reliability of the battery BT system.

[0032] Secondly, the voltage detection unit 10 directly monitors the voltage drop across the current-limiting resistor 2. Combined with the real-time comparison by the comparison unit 11, it can quickly identify abnormal currents (such as detecting a real-time voltage VX exceeding the reference voltage DAC) in the early stages of a short circuit, and directly control the discharge switch unit 3 to cut off the circuit. Compared to traditional solutions that rely on delay for judgment (such as the fixed delay of the AFE chip), the response speed is improved to the microsecond level.

[0033] Additionally, it should be noted that the value of the reference voltage DAC can be dynamically configured in the controller MCU. For example, when the controller MCU detects a load upon power-on, the reference voltage DAC can be configured to the preset maximum value. After successful power-on, it can be modified back to the preset normal value. This ensures the safety of the BMS and battery BT even under normal power-on conditions.

[0034] On the other hand, the controller MCU is also connected to the output terminals of the discharge switch unit 3 and the comparison unit 11, so that the controller MCU can lock the discharge switch unit 3 in the open or closed state according to the output signal ECK of the comparison unit 11.

[0035] In this embodiment, when the comparison unit 11 determines that the real-time voltage VX exceeds the reference voltage DAC (e.g., due to a short circuit or overcurrent), the controller MCU immediately locks the discharge switch unit 3 in the open state, forcibly cutting off the discharge circuit. After the fault is cleared, the controller MCU needs to be reset to restore conduction, thus avoiding false triggering or repeated oscillations.

[0036] On the other hand, the voltage detection unit 10 includes an operational amplifier U1, the non-inverting and inverting inputs of the operational amplifier U1 are respectively connected to the two ends of the current limiting resistor 2, and the output of the operational amplifier U1 is connected to the input of the comparison unit 11.

[0037] During operation, the non-inverting and inverting inputs of operational amplifier U1 receive voltages V1 and V2 across the current resistor, respectively, and amplify the difference between these voltages for output.

[0038] Specifically, the non-inverting terminal is connected to the high end of the current-limiting resistor 2 (closer to the main electrode side of the battery BT) via resistor R1. The inverting terminal is connected to the low end of the current-limiting resistor 2 (closer to the load side) via resistor R2.

[0039] Operational amplifier U1 features high input impedance and low offset voltage, enabling it to accurately detect minute voltage differences across current-limiting resistor 2.

[0040] In addition, a feedback resistor R3 is provided between the output terminal and the inverting terminal of operational amplifier U1. A first RC filter circuit is also provided at the output terminal of operational amplifier U1. For example, the resistance of this feedback resistor R3 is 10 kΩ, used to set the gain of operational amplifier U1, so that small voltage signals are amplified to a level suitable for subsequent processing. The feedback resistor R3 is a precision resistor with a small temperature coefficient, ensuring stability at different temperatures.

[0041] The first RC filter circuit consists of resistor R4 and capacitor C1, and is used to filter out high-frequency noise in the output signal of operational amplifier U1, thereby improving the stability and reliability of the signal.

[0042] On the other hand, the comparison unit 11 includes a voltage comparator U2. The two input terminals of the voltage comparator U2 are connected to the controller MCU and the voltage detection unit 10, respectively, and the output terminal of the voltage comparator U2 is connected to the discharge switch unit 3 and the controller MCU. The voltage comparator U2 has fast response characteristics and can complete the voltage comparison operation within microseconds, so as to respond to short circuit conditions in a timely manner.

[0043] It is worth noting that one input terminal of the voltage comparator U2, which is connected to the controller MCU, is equipped with voltage divider resistors R6 and R7.

[0044] The output of voltage comparator U2 is also equipped with a second RC filter circuit. The second RC filter circuit consists of resistor R5 and capacitor C2, which is used to filter out glitches and interference in the output signal of voltage comparator U2, prevent false triggering, and improve the anti-interference capability of the system.

[0045] In addition, such as Figure 1 The power protection circuit also includes a power supply unit 5. The input terminal of the power supply unit 5 is connected to the battery BT, and the output terminal of the power supply unit 5 is connected to the controller MCU and the short-circuit protection circuit 1. Specifically, the power supply unit 5 adopts a low-dropout linear regulator, which provides a stable operating voltage for the controller MCU and the short-circuit protection circuit 1, ensuring the normal operation of the protection circuit.

[0046] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the scope of the present utility model application shall still fall within the scope of the present utility model.

Claims

1. A power protection circuit for a rechargeable battery, characterized in that, include: The power bus has one end connected to the main electrode of the battery to be protected, and the other end used to connect to the load. A discharge switch unit and a current-limiting resistor are connected in series on the power bus; A short-circuit protection circuit includes a voltage detection unit and a comparison unit; the input terminal of the voltage detection unit is connected to both ends of the current-limiting resistor and is used to detect the voltage across the current-limiting resistor. The two input terminals of the comparison unit are respectively connected to the output terminals of the controller and the voltage detection unit to receive the real-time voltage detected by the voltage detection unit and the reference voltage output by the controller, and the controller provides the pre-configuration and adjustment function of the reference voltage; The output terminal of the comparison unit is connected to the discharge switch unit to control the discharge switch unit to be in an open or closed state according to the relationship between the real-time voltage and the reference voltage. In the open state, the discharge circuit on the power bus is disconnected, and in the closed state, the discharge circuit on the power bus is connected.

2. The power protection circuit according to claim 1, characterized in that, The controller is also connected to the output terminals of the discharge switch unit and the comparison unit, so that the controller can lock the discharge switch unit in an open or closed state according to the output of the comparison unit.

3. The power protection circuit according to claim 1, characterized in that, The voltage detection unit includes an operational amplifier, the non-inverting and inverting inputs of which are respectively connected to the two ends of the current-limiting resistor, and the output of the operational amplifier is connected to the input of the comparison unit.

4. The power protection circuit according to claim 3, characterized in that, A feedback resistor is provided between the output terminal and the inverting terminal of the operational amplifier.

5. The power protection circuit according to claim 3, characterized in that, The output of the operational amplifier is also provided with a first RC filter circuit.

6. The power protection circuit according to claim 1, characterized in that, The comparison unit includes a voltage comparator, the two input terminals of which are respectively connected to the controller and the voltage detection unit, and the output terminal of the voltage comparator is connected to the discharge switch unit.

7. The power protection circuit according to claim 6, characterized in that, The output of the voltage comparator is also equipped with a second RC filter circuit.

8. The power protection circuit according to claim 1, characterized in that, It also includes a power supply unit, the input of which is connected to the battery, and the output of which is connected to the controller and the short-circuit protection circuit.

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