Electric vehicle battery insulation resistance detection circuit and battery pack

Abstract

The utility model belongs to the technical field of lithium ion batteries, and particularly relates to an electric automobile battery insulation resistance detection circuit and a battery pack, which comprise a high-voltage switch peripheral circuit module, a front-end sampling chip, a communication module and an MCU module, the high-voltage switch peripheral circuit module is connected with the battery pack, and when the high-voltage switch peripheral circuit module works, the high-voltage switch is repeatedly switched between a closed state and an open state, so that the circuit state is periodically changed; the front-end sampling chip is connected with the peripheral circuit module of the high-voltage switch, and periodically performs voltage acquisition on voltage detection points in the peripheral circuit module; the communication module transmits voltage information acquired by the front-end sampling chip to the MCU module; and the MCU module processes the acquired voltage information to obtain a battery pack insulation resistance value. According to the device, the system circuit design is simplified, electrical isolation between the MCU and high voltage is realized by using a high-precision sampling chip, the circuit reliability is improved, and the purpose of saving the cost is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium-ion batteries, and in particular relates to an insulation resistance detection circuit and a battery pack for an electric vehicle battery. Background Art

[0002] Increasing energy depletion has led to a growing emphasis on new energy technologies, particularly in the automotive sector. Power batteries, the core energy source, are also gaining widespread adoption, and battery management systems play an irreplaceable role in ensuring safe and reliable vehicle operation. Electric vehicle battery packs operate at high voltage, and leakage or human contact can pose significant safety risks and threaten life. Therefore, insulation testing of electric vehicle battery packs is crucial.

[0003] For example, a Chinese patent discloses a battery pack online insulation detection method and detection circuit, application number: 202210290081.8. The method steps include: S1, turning on the MOS transistor Q1 in the online insulation detection circuit, and then disconnecting the relay switches K1, K2, and K3 to separate the battery pack from the overall battery; S2, closing the relay switch K1; S3, turning on the MOS transistor Q2 in the online insulation detection circuit, and first controlling the MOS transistor Q4 to turn on and the MOS transistor Q5 to turn off, then controlling the MOS transistor Q4 to turn off and the MOS transistor Q5 to turn on, and finally controlling the MOS transistors Q4 and Q5 to turn on simultaneously. After each driving action of the MOS transistors Q4 and Q5, the voltage across the sampling resistor is collected and stored; S4, based on each collected voltage, a total collected voltage is calculated as the independent variable of the battery pack equivalent resistance calculation model; S5, substituting the independent variable into the battery pack equivalent resistance to ground calculation model to obtain the equivalent resistance to ground of the positive and negative electrodes of the battery pack. The disadvantages of this patent are that the entire system requires multiple switches and MOS tubes, the logic control is relatively complex, and the cost is too high.

[0004] Another example is a Chinese patent application numbered 201910217981.8, which discloses an insulation detection circuit for an electric vehicle power battery. The circuit includes a power battery. The positive electrode of the power battery, Pack+, outputs a voltage signal V1 through an optocoupler relay U1, which then transmits it to the input of a follower circuit and a differential amplifier circuit. The negative electrode of the power battery, Pack-, outputs a voltage signal V2 through an optocoupler relay U2, which then transmits it to the input of the differential amplifier circuit. The output voltage signals Vin1 and Vin2 of the follower circuit and the differential amplifier circuit are then sent to a data processing unit after passing through analog-to-digital converters. The data processing unit calculates the insulation resistance of the positive and negative electrodes based on the voltage signals Vin1 and Vin2. The patent has the following disadvantages: the entire detection circuit requires components such as a differential amplifier circuit, a digital-to-analog converter, and a processing unit. This results in a complex circuit, lacks high-voltage isolation, poses a risk of damaging the MCU and the entire system, and is prohibitively expensive. Utility Model Content

[0005] The purpose of the utility model is to provide an electric vehicle battery insulation resistance detection circuit and a battery pack, so as to solve the problems of potential safety hazards and low production capacity in the prior art.

[0006] To achieve the above-mentioned purpose, the present utility model provides the following technical solutions: an electric vehicle battery insulation resistance detection circuit, comprising a high-voltage switch peripheral circuit module, a front-end sampling chip, a communication module and an MCU module;

[0007] The high-voltage switch peripheral circuit module is connected to the battery pack. When the high-voltage switch peripheral circuit module is in operation, the high-voltage switch will repeatedly switch between closed and open states, thereby periodically changing the circuit state.

[0008] The front-end sampling chip is connected to the high-voltage switch peripheral circuit module, and periodically collects voltages at voltage detection points in the peripheral circuit module, collecting voltage values ​​before and after the high-voltage switch is closed;

[0009] The communication module transmits the voltage information collected by the front-end sampling chip to the MCU module; the MCU module processes the collected voltage information to obtain the insulation resistance value of the battery pack. This patent replaces the detection circuit composed of components such as the differential amplifier circuit, digital-to-analog converter, and processing unit with a high-precision sampling chip (AFE) and a single switch, simplifying the system circuit design. The use of a high-precision sampling chip achieves electrical isolation between the MCU and the high voltage, increasing circuit reliability and achieving cost savings.

[0010] Preferably, the high-voltage switch peripheral circuit module includes resistors R1, R2, R3, R4, and a high-voltage switch K1. The resistors R1, R2, R3, and R4 are connected in series, with one end of resistor R1 connected to the positive electrode of the battery pack and one end of resistor R4 connected to the negative electrode of the battery pack. One end of the high-voltage switch K1 is connected between resistors R1 and R2, and the other end of the high-voltage switch K1 is connected to the negative electrode of the battery pack. The area between resistors R2 and R3 is grounded, and a front-end sampling chip is connected between resistors R3 and R4. This high-voltage switch peripheral circuit has a simple structure, using only four resistors and one high-voltage switch, which simplifies circuit design and control logic, saving manufacturing costs.

[0011] Preferably, in order to obtain simplified calculations later, the software calculation process is simplified, and thus the resistor R1 is set to be equal to the resistor R2 and equal to 1000k, with a resistance error of ±10%.

[0012] Preferably, the resistance of the resistor R3 is 1990k, and the resistance error is ±10%.

[0013] Preferably, the resistance of the resistor R4 is 2000k-resistance R3, but not less than 1k.

[0014] Preferably, the voltage information Ux collected by the front-end sampling chip is 0-5V.

[0015] Preferably, the communication module adopts daisy chain communication.

[0016] Preferably, the communication module adopts CAN communication.

[0017] Preferably, the front-end sampling chip is a BQ7963x chip from TI, an MC33771 chip from NXP, or an LTC2950 chip from ADI.

[0018] The utility model also discloses a battery pack, comprising the electric vehicle battery insulation resistance detection circuit, wherein the high-voltage switch peripheral circuit module is connected between the total positive and total negative batteries inside the battery pack.

[0019] The beneficial effects of the present invention are as follows: compared with the prior art, the patented high-precision sampling chip (AFE) and the structure of a single switch, and only one high-voltage switch required in the entire insulation detection circuit, simplify the circuit design, reduce the complexity of software development, and save the design cost of the detection solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a circuit principle diagram of the utility model;

[0021] Figure 2This is a circuit diagram of the peripheral circuit module of the medium and high voltage switch of the utility model;

[0022] Figure 3 It is the equivalent circuit diagram of the non-closed high-voltage switch K1 in the high-voltage switch peripheral circuit module;

[0023] Figure 4 It is the equivalent circuit diagram of the closed high-voltage switch K1 in the high-voltage switch peripheral circuit module;

[0024] Figure 5 This is a schematic diagram of a battery pack provided in this embodiment. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0026] like Figure 1 As shown, an electric vehicle battery insulation resistance detection circuit includes a high-voltage switch peripheral circuit module 1, a front-end sampling chip 2, a communication module 3, and an MCU module 4. In this solution, the communication module adopts daisy chain communication. Other communication methods, such as CAN communication, can also be adopted. The daisy chain communication method is used as an example below. Specifically, the battery pack is connected to the high-voltage switch peripheral circuit module, and the high-voltage switch peripheral circuit module is connected to the front-end sampling chip. The voltage at the corresponding voltage detection point in the high-voltage switch peripheral circuit module is sampled before and after the high-voltage switch is closed. The front-end sampling chip is then connected to the daisy chain communication, and the daisy chain communication is connected to the MCU module. The collected voltage signal is converted into the battery pack insulation resistance value through a calculation formula to complete the insulation resistance detection.

[0027] like Figure 2 As shown, specifically, the high-voltage switch peripheral circuit module includes resistor R1, resistor R2, resistor R3, resistor R4 and high-voltage switch K1. The resistors R1, R2, R3 and R4 are connected in series. One end of resistor R1 is connected to the positive electrode of the battery pack, and one end of resistor R4 is connected to the negative electrode of the battery pack. One end of the high-voltage switch K1 is connected between resistor R1 and resistor R2, and the other end of the high-voltage switch K1 is connected to the negative electrode of the battery pack. Resistors R2 and R3 are grounded, and the front-end sampling chip is connected between resistors R3 and R4. In the figure, K1 is the high-voltage switch of the insulation detection circuit, and resistors R1, R2, R3 and R4 are the voltage divider resistors of the insulation detection circuit. It should be noted that the voltage collected by the front-end sampling chip is the voltage on resistor R4. The voltage on resistor R4 is U1, and the battery pack voltage is U, U xis the sampling voltage of the front-end sampling chip, Ri so+ and Ri so- are the insulation resistance to be measured. In this patent, resistor R1 = resistor R2 = 1000k, resistor R3 = 1990k, resistor R4 = 10k, point P is the reference point of the positive electrode of the battery pack to the ground, and point N is the reference point of the negative electrode of the battery pack to the ground.

[0028] See also Figure 2 This patent will explain in detail the working principle of insulation resistance detection. The specific implementation steps are:

[0029] Step 1: The high-voltage switch K1 in the high-voltage switch peripheral circuit module is not closed. Figure 3 The equivalent circuit diagram of , according to the resistor voltage division and series-parallel relationship, can obtain formula 1-formula 5:

[0030]

[0031] U P1 -U N1 =U (Formula 3)

[0032]

[0033] Among them, R P1 is the equivalent resistance of the positive electrode of the battery pack to the ground reference point, R N1 is the equivalent resistance of the negative electrode of the battery pack to the ground reference point, U P1 is the voltage of the positive electrode of the battery pack to the ground reference point, U N1 is the voltage of the negative pole of the battery pack to the ground reference point, and U1 is the sampling voltage of the front-end sampling chip.

[0034] Step 2: Close the high-voltage switch K1 in the high-voltage switch peripheral circuit module, refer to Figure 4 The equivalent circuit diagram of , according to the resistor voltage division and series-parallel relationship, can obtain formula 6-formula 10:

[0035]

[0036] U P2 -U N2 =U (Formula 8)

[0037]

[0038] Among them, R P2 is the equivalent resistance of the positive electrode of the battery pack to the ground reference point, R N2 is the equivalent resistance of the negative electrode of the battery pack to the ground reference point, U P2 is the voltage of the positive electrode of the battery pack to the ground reference point, U N2 is the voltage of the negative pole of the battery pack to the ground reference point, and U2 is the sampling voltage of the front-end sampling chip.

[0039] After completing steps 1 and 2, the insulation resistances Ri so+ and Ri so- to be measured can be calculated by combining formulas 1 to 10, as shown in formulas 11 and 12:

[0040]

[0041] This utility model controls the states of two switching devices separately, causing the voltage value of U1 to vary. The insulation resistance value can be calculated using the above formula. In this solution, only one switch controls the circuit state. Turning switch K1 on and off generates the voltages required for calculations in Formulas 11 and 12, and calculates the required insulation detection resistance values, Ri so+ and Ri so-. This solution utilizes an AFE + MCU insulation detection solution, requiring only one high-voltage switch in the entire insulation detection circuit. This simplifies circuit design, reduces software development complexity, and saves design costs for the detection solution.

[0042] like Figure 5 As shown, the utility model also discloses a battery pack, Figure 5 BATT_P and BATT_N are the total positive and negative of the batteries in the battery pack, that is, the corresponding Figure 2 When the detection circuit of the present invention is used, the high voltage switch K1 is in the open and closed states respectively, and the battery pack BATT_P point and N point are Figure 2 One end of the resistor R1 is connected to the BATT_N point Figure 2 One end of the resistor R4 is connected, so we can get Figure 3 and Figure 4 The corresponding two equivalent circuit diagrams are then obtained through the front-end sampling chip described in this patent Figure 3 and Figure 4 The voltages U1 and U2 on the resistor R4 are finally calculated by the MCU module using formulas 11 and 12 to obtain the required equivalent insulation resistance Ri so- and Ri so+ voltages.

[0043] It should be pointed out that this device can be used to transport semi-finished lithium batteries, provide vacuum or inert gas according to requirements, and select different accessories for combination to fully utilize space and improve work efficiency. For ordinary technicians in this technical field, without departing from the principles of this utility model, several improvements and modifications can be made, and these improvements and modifications should also be regarded as within the scope of protection of this utility model.

Claims

1. An electric vehicle battery insulation resistance detection circuit, characterized in that: Including high-voltage switch peripheral circuit module, front-end sampling chip, communication module and MCU module; The high-voltage switch peripheral circuit module is connected to the battery pack. When the high-voltage switch peripheral circuit module is in operation, the high-voltage switch will repeatedly switch between closed and open states, thereby periodically changing the circuit state. The front-end sampling chip is connected to the high-voltage switch peripheral circuit module, and periodically collects voltages at voltage detection points in the peripheral circuit module, collecting voltage values ​​before and after the high-voltage switch is closed; The communication module transmits the voltage information collected by the front-end sampling chip to the MCU module; The MCU module processes the collected voltage information to obtain the insulation resistance value of the battery pack.

2. The electric vehicle battery insulation resistance detection circuit according to claim 1, characterized in that: The high-voltage switch peripheral circuit module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4 and a high-voltage switch K1. The resistors R1, R2, R3 and R4 are connected in series, one end of the resistor R1 is connected to the positive electrode of the battery pack, one end of the resistor R4 is connected to the negative electrode of the battery pack, one end of the high-voltage switch K1 is connected between the resistor R1 and the resistor R2, the other end of the high-voltage switch K1 is connected to the negative electrode of the battery pack, the resistor R2 and the resistor R3 are grounded, and the resistor R3 and the resistor R4 are connected to the front-end sampling chip.

3. The electric vehicle battery insulation resistance detection circuit according to claim 2, characterized in that: The resistor R1 = resistor R2 = 1000k, and the resistance error is ±10%.

4. The electric vehicle battery insulation resistance detection circuit according to claim 2, characterized in that: The resistance of the resistor R3 is 1990k, and the resistance error is ±10%.

5. The electric vehicle battery insulation resistance detection circuit according to claim 2, characterized in that: The resistance of the resistor R4 is 2000k-resistance R3, but not less than 1k.

6. The electric vehicle battery insulation resistance detection circuit according to claim 2, characterized in that: The voltage information Ux collected by the front-end sampling chip is 0-5V.

7. The electric vehicle battery insulation resistance detection circuit according to claim 1 or 2, characterized in that: The communication module adopts daisy chain communication.

8. The electric vehicle battery insulation resistance detection circuit according to claim 1 or 2, characterized in that: The communication module adopts CAN communication.

9. The electric vehicle battery insulation resistance detection circuit according to claim 1 or 2, characterized in that: The front-end sampling chip adopts the BQ7963x chip of TI Company, the MC33771 chip or the MC33774 chip of NXP Company, or the LTC2950 chip of ADI Company.

10. A battery pack, characterized in that: The electric vehicle battery insulation resistance detection circuit comprises the circuit according to any one of claims 1 to 9, wherein the high-voltage switch peripheral circuit module is connected between the total positive of the batteries inside the battery pack and the total negative of the batteries inside the battery pack.

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