A pre-discharge detection circuit suitable for a battery protection board

Abstract

The utility model discloses a kind of pre-discharge detection circuits suitable for battery protection board, including battery T, current detection resistance module, discharge MOS control circuit, charging MOS control circuit, pre-discharge loop, output terminal P+, output terminal P-, electrical equipment, control module, electrical equipment has capacitive load, further including pre-discharge completion detection circuit, the negative pole B- of battery T is connected current detection resistance module, current detection resistance module is connected charging MOS control circuit by discharge MOS control circuit, discharge MOS control circuit, charging MOS control circuit are connected pre-discharge loop, charging MOS control circuit connects pre-discharge completion detection circuit, output terminal P+ is connected the positive pole B+ of battery T, pre-discharge completion detection circuit is used to detect whether pre-discharge loop is full of electricity to capacitive load.The utility model aims at different capacitive load, this circuit can detect whether battery charges to external capacitor is completed, with good practicability.

Description

Technical Field

[0001] This utility model relates to a pre-discharge detection circuit suitable for battery protection boards. Background Technology

[0002] The number of electronic products using lithium batteries is increasing daily, expanding from early digital products to various categories such as transportation and robots. However, the protection functions of general-purpose BMS (Battery Management System) cannot cover all the actual application scenarios of all types of batteries. Especially when the load power is high, the interface of the electrical equipment often has a large capacitive load. When the battery comes into contact with the load, it is close to an external short circuit, which can easily trigger the short circuit protection and cause the battery to stop outputting power. Therefore, some BMSs have added a pre-discharge function, such as... Figure 1 Module 6 works by first activating pre-discharge to charge the external capacitor the moment the battery contacts the load. Once the capacitor is fully charged, the battery output function is activated, thus avoiding false triggering of the short-circuit protection caused by contact arcing. However, this pre-discharge circuit has obvious drawbacks. Because the equivalent capacitance values ​​of different loads vary, the activation time of the corresponding pre-discharge circuit needs to be adjusted accordingly, resulting in poor compatibility and a narrow range of applications. Utility Model Content

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pre-discharge detection circuit suitable for battery protection boards.

[0004] To achieve the above objectives, this utility model is implemented through the following technical solution:

[0005] A pre-discharge detection circuit for a battery protection board includes a battery T, a current sensing resistor module, a discharge MOS control circuit, a charging MOS control circuit, a pre-discharge circuit, an output terminal P+, an output terminal P-, a power device, and a control module. The power device has a capacitive load. The circuit also includes a pre-discharge completion detection circuit. The negative terminal B- of the battery T is connected to the current sensing resistor module. The current sensing resistor module is connected to the charging MOS control circuit via the discharge MOS control circuit. Both the discharge MOS control circuit and the charging MOS control circuit are connected to the pre-discharge circuit. The charging MOS control circuit is connected to the pre-discharge completion detection circuit. The pre-discharge completion detection circuit is connected between the output terminals P+ and P-. The power device is also connected between the output terminals P+ and P-. The output terminal P+ is connected to the positive terminal B+ of the battery T. The current sensing resistor module, the discharge MOS control circuit, the charging MOS control circuit, the pre-discharge circuit, and the pre-discharge completion detection circuit are all connected to the control module. The pre-discharge completion detection circuit is used to detect whether the pre-discharge circuit has fully charged the capacitive load.

[0006] Preferably, the pre-discharge completion detection circuit includes resistors R29, R30, R31, and R32, capacitor C10, diode D8, Zener diode D9, isolation optocoupler U1, isolation optocoupler U2, and power supply VCC. One end of resistor R30 is connected to the control module, and the other end of resistor R30 is connected to the anode of isolation optocoupler U1. The cathode of isolation optocoupler U1 is connected to ground signal GND. The collector of isolation optocoupler U1 is connected to the positive terminal B+ of battery T through resistor R32. The emitter is connected to the anode of the isolation optocoupler U2, the cathode of the isolation optocoupler U2 is connected to the positive terminal of diode D8, the negative terminal of diode D8 is connected to the output terminal P- through Zener diode D9, the emitter of the isolation optocoupler U2 is connected to ground signal GND, the collector of the isolation optocoupler U2 is connected to the power supply VCC through resistor R29, the collector of the isolation optocoupler U2 is connected to one end of resistor R31, the other end of resistor R31 is connected to the control module, and the other end of resistor R31 is connected to ground signal GND through capacitor C10.

[0007] Preferably, the power supply VCC is 3.3V.

[0008] Preferably, the current sensing resistor module is used to detect the magnitude and direction of the current in the charging and discharging circuit, and to calculate the charge and abnormal current protection.

[0009] Preferably, the discharge MOS control circuit is used to control the on / off state of the discharge circuit.

[0010] Preferably, the charging MOS control circuit is used to control the on / off state of the charging circuit.

[0011] Preferably, the pre-discharge circuit is used to charge the capacitive load.

[0012] The beneficial effects of this utility model are as follows: This utility model has a simple function and low cost. It can effectively solve the problem of false short circuit protection when lithium batteries are connected to capacitive loads. For different capacitive loads, this circuit can detect whether the battery has completed charging the external capacitor, and then switch from pre-discharge to normal discharge. Actual verification shows that this circuit can work normally and realize the set function, and has good practicality. Attached Figure Description

[0013] Figure 1 This is a circuit schematic diagram of existing technology;

[0014] Figure 2 This is the circuit schematic diagram of this utility model;

[0015] Figure 3 The circuit diagram for the detection circuit to complete the pre-discharge. Detailed Implementation

[0016] The technical solution of this utility model will be further described below with reference to the accompanying drawings:

[0017] like Figure 2 , Figure 3 As shown, a pre-discharge detection circuit suitable for a battery protection board includes a battery T, a current sensing resistor module 3, a discharge MOS control circuit 4, a charging MOS control circuit 5, a pre-discharge circuit 6, an output terminal P+, an output terminal P-, a power-consuming device 8, and a control module 9. The power-consuming device 8 has a capacitive load. The circuit also includes a pre-discharge completion detection circuit 7. The negative terminal B- of the battery T is connected to the current sensing resistor module 3. The current sensing resistor module 3 is connected to the charging MOS control circuit 5 through the discharge MOS control circuit 4. Both the discharge MOS control circuit 4 and the charging MOS control circuit 5... The pre-discharge circuit 6 is connected, the charging MOS control circuit 5 is connected to the pre-discharge completion detection circuit 7, the pre-discharge completion detection circuit 7 is connected between the output terminal P+ and the output terminal P-, and the electrical device 8 is also connected between the output terminal P+ and the output terminal P-. The output terminal P+ is connected to the positive terminal B+ of the battery T. The current sensing resistor module 3, the discharge MOS control circuit 4, the charging MOS control circuit 5, the pre-discharge circuit 6, and the pre-discharge completion detection circuit 7 are all connected to the control module 9. The pre-discharge completion detection circuit 7 is used to detect whether the pre-discharge circuit 6 has fully charged the capacitive load.

[0018] like Figure 2 , Figure 3 As shown, the pre-discharge completion detection circuit 7 includes resistors R29, R30, R31, and R32, capacitor C10, diode D8, Zener diode D9, isolation optocoupler U1, isolation optocoupler U2, and power supply VCC. One end of resistor R30 is connected to the control module 9, and the other end of resistor R30 is connected to the anode of isolation optocoupler U1. The cathode of isolation optocoupler U1 is connected to ground signal GND. The collector of isolation optocoupler U1 is connected to the positive terminal B+ of battery T through resistor R32. The output of isolation optocoupler U1... The emitter of the optocoupler U2 is connected to the anode, the cathode of the optocoupler U2 is connected to the anode of the diode D8, the cathode of the diode D8 is connected to the output terminal P- through the Zener diode D9, the emitter of the optocoupler U2 is connected to the ground signal GND, the collector of the optocoupler U2 is connected to the power supply VCC through the resistor R29, the collector of the optocoupler U2 is connected to one end of the resistor R31, the other end of the resistor R31 is connected to the control module 9, and the other end of the resistor R31 is connected to the ground signal GND through the capacitor C10.

[0019] like Figure 2 , Figure 3As shown, the power supply VCC is 3.3V. Current sensing resistor module 3 is used to detect the magnitude and direction of the current in the charging and discharging circuit, and to calculate the charge level and provide abnormal current protection. Discharge MOS control circuit 4 is used to control the on / off state of the discharge circuit. Charging MOS control circuit 5 is used to control the on / off state of the charging circuit. Pre-discharge circuit 6 is used to charge capacitive loads.

[0020] like Figure 3 As shown, U1 and U2 are isolation optocouplers, used to isolate the negative terminal B- of battery T from the negative output terminal P- of battery T, and to detect changes in the output voltage P- and feed them back to the control module 9; R30 and R32 are current-limiting resistors used to control the conduction current of the optocouplers; R29 is a pull-up resistor to ensure that MCU_PRE_VOL maintains a stable 3.3V when U2 is not conducting; D8 is a general diode to prevent reverse current from flowing back to the P- terminal; D9 is a Zener diode, used to regulate voltage when the battery is connected to the device 8, first through... Figure 2 The pre-discharge circuit 6 limits the current to charge the external capacitive load. As the voltage of the external capacitive load increases, the P- voltage gradually decreases until it is below about 34V. At this point, D9 conducts in reverse, the U2 optocoupler conducts, and the MCU_PRE_VOL voltage changes from 3.3V to 0V. The control module 9 can then determine that the pre-discharge process is complete.

[0021] Circuit connection relationships:

[0022] like Figure 2 B+ and B- are the positive and negative terminals of battery T, serving as the current input / output ports; P+ and P- are the output ports, connecting to external electrical equipment 8; the current sensing resistor module 3 is used to detect the magnitude and direction of the current in the charging and discharging circuit, and to calculate the charge and abnormal current protection; the discharge MOS control circuit 4 is used to control the on / off state of the discharge circuit; the charging MOS control circuit 5 is used to control the on / off state of the charging circuit.

[0023] The operation process of the pre-discharge completion detection circuit 7 is as follows:

[0024] When the device connected to the battery is a capacitive load, the capacitor is equivalent to a short circuit the instant the battery is connected to the device, triggering the BMS short-circuit protection. To avoid this abnormal short circuit, such as... Figure 2As shown, before battery use, control module 9 keeps the main discharge MOSFET of discharge MOS control circuit 4 disconnected, and the MCU_DET_EN output in pre-discharge completion detection circuit 7 is high, turning on optocoupler U1. At the same time, Q1 in the pre-discharge circuit of pre-discharge circuit 6 is turned on. When the battery contacts the capacitive load, the battery discharge current discharges through the external capacitor and the pre-discharge resistors R13~R22 of pre-discharge circuit 6. The pre-discharge resistors can limit the current in this circuit and avoid triggering short circuit protection by large current. During the charging process of the external capacitor, the voltage of P- gradually decreases from the highest point VP (total cell voltage). When the P- voltage drops below (VP-34V), D9 conducts in reverse, optocoupler U2 turns on, and the MCU's IO port MCU_PRE_VOL detects that the voltage changes from 3.3V to 0V, thus recognizing that the external capacitor has been fully charged. Then, control module 9 turns on the discharge MOSFET of discharge MOS control circuit 4, disconnects the pre-discharge circuit of pre-discharge circuit 6, disconnects optocoupler U1 in pre-discharge completion detection circuit 7, and the battery starts to output normally. The highest point voltage value of the total cell voltage is VP.

[0025] When the BMS contains a pre-discharge circuit, combined with Figure 3 The MCU can determine whether the pre-discharge process is complete and switch the discharge current from the pre-discharge circuit to the main discharge circuit in a timely manner.

[0026] Figure 3 The pre-discharge completion detection circuit 7 utilizes the characteristic that the P- voltage gradually decreases when the external capacitor is charged during battery pre-discharge. It uses two optocouplers U1, U2 and D9 to achieve the pre-discharge process detection function.

[0027] In this scheme, the voltage regulation value of diode D9 is a key parameter for determining the completion of pre-discharge, and it can be adjusted according to different battery voltages;

[0028] The resistance values ​​of R29, R30, and R31 in the pre-discharge completion detection circuit 7 can be adjusted according to the actual situation; the selection of optocouplers U1 and U2 can be based on the actual application.

[0029] This utility model has a simple function and low cost. It can effectively solve the problem of false short circuit protection when lithium batteries are connected to capacitive loads. For different capacitive loads, the circuit can detect whether the battery has completed charging the external capacitor, and then switch from pre-discharge to normal discharge. Practical verification has shown that this circuit can work normally and achieve the set function, and has good practicality.

[0030] It should be noted that the above examples are only one specific embodiment of this utility model. Obviously, this utility model is not limited to the above embodiments and can have many variations. In short, all variations that can be directly derived or conceived by those skilled in the art from the content disclosed in this utility model should be considered within the protection scope of this utility model.

Claims

1. A pre-discharge detection circuit suitable for a battery protection board, comprising a battery T, a current sensing resistor module (3), a discharge MOS control circuit (4), a charging MOS control circuit (5), a pre-discharge circuit (6), an output terminal P+, an output terminal P-, an electrical device (8), and a control module (9), wherein the electrical device (8) has a capacitive load, characterized in that, It also includes a pre-discharge completion detection circuit (7), the negative terminal B- of the battery T is connected to the current sensing resistor module (3), the current sensing resistor module (3) is connected to the charging MOS control circuit (5) through the discharge MOS control circuit (4), the discharge MOS control circuit (4) and the charging MOS control circuit (5) are both connected to the pre-discharge circuit (6), the charging MOS control circuit (5) is connected to the pre-discharge completion detection circuit (7), the output terminal P+ and the output terminal P- are connected to the pre-discharge completion detection circuit (7), the output terminal P+ and the output terminal P- are also connected to the electrical equipment (8), the output terminal P+ is connected to the positive terminal B+ of the battery T, the current sensing resistor module (3), the discharge MOS control circuit (4), the charging MOS control circuit (5), the pre-discharge circuit (6) and the pre-discharge completion detection circuit (7) are all connected to the control module (9), the pre-discharge completion detection circuit (7) is used to detect whether the pre-discharge circuit (6) has fully charged the capacitive load.

2. The pre-discharge detection circuit suitable for a battery protection board according to claim 1, characterized in that, The pre-discharge completion detection circuit (7) includes resistors R29, R30, R31, and R32, capacitor C10, diode D8, Zener diode D9, isolation optocoupler U1, isolation optocoupler U2, and power supply VCC. One end of resistor R30 is connected to the control module (9), and the other end of resistor R30 is connected to the anode of isolation optocoupler U1. The cathode of isolation optocoupler U1 is connected to ground signal GND. The collector of isolation optocoupler U1 is connected to the positive terminal B+ of battery T through resistor R32. The emitter is connected to the anode of the isolation optocoupler U2, the cathode of the isolation optocoupler U2 is connected to the positive terminal of the diode D8, the negative terminal of the diode D8 is connected to the output terminal P- through the Zener diode D9, the emitter of the isolation optocoupler U2 is connected to the ground signal GND, the collector of the isolation optocoupler U2 is connected to the power supply VCC through the resistor R29, the collector of the isolation optocoupler U2 is connected to one end of the resistor R31, the other end of the resistor R31 is connected to the control module (9), and the other end of the resistor R31 is connected to the ground signal GND through the capacitor C10.

3. The pre-discharge detection circuit suitable for a battery protection board according to claim 2, characterized in that, The power supply VCC is 3.3V.

4. The pre-discharge detection circuit suitable for a battery protection board according to claim 1, characterized in that, The current sensing resistor module (3) is used to detect the magnitude and direction of the current in the charging and discharging circuit, and to calculate the power and abnormal current protection.

5. The pre-discharge detection circuit suitable for a battery protection board according to claim 1, characterized in that, The discharge MOS control circuit (4) is used to control the on / off state of the discharge circuit.

6. The pre-discharge detection circuit suitable for a battery protection board according to claim 1, characterized in that, The charging MOS control circuit (5) is used to control the on / off state of the charging circuit.

7. The pre-discharge detection circuit suitable for a battery protection board according to claim 1, characterized in that, The pre-discharge circuit (6) is used to charge the capacitive load.

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