Low-side circuit of lithium battery protection board of electric vehicle

Abstract

The invention relates to the technical field of lithium batteries, in particular to an electric vehicle lithium battery protection board low-side circuit compatible with an integrated services digital network and CAN communication. The device comprises a control template, a charging and discharging control circuit, a communication circuit and an acquisition circuit. The circuit is characterized in that the charging and discharging control circuit comprises a three-terminal fuse FUSE1, one fuse terminal of the three-terminal fuse FUSE1 is connected with a source electrode of a charging MOS of the charging and discharging control circuit, and the other fuse terminal of the three-terminal fuse FUSE1 is connected with a charging port P- / C-of the battery. The control end of the three-terminal fuse FUSE1 is used for being connected with the positive electrode B + of the lithium battery through the first switching circuit, when the lithium battery breaks down, the control module controls the first switching circuit to be switched on, voltage difference is generated between the control end of the three-terminal fuse and the fuse end, and the three-terminal fuse is fused. The circuit is low in cost, the protection plate cannot be damaged, and personal and property safety cannot be affected.

Description

Technical Field

[0001] The invention relates to the technical field of lithium batteries, in particular to a low-side circuit of a lithium battery protection board of an electric vehicle which is compatible with one-line communication and CAN communication. Background Art

[0002] GB43854-2024 "Safety Technical Specifications for Lithium-ion Batteries for Electric Bicycles" will be officially implemented on November 1, 2024. The specification requires that the battery pack must adopt a double protection design and can only be charged after successful mutual recognition with the charger.

[0003] At present, in traditional BMS systems, three-terminal fuses are generally used in the positive circuit. In the low-side solution, it is necessary to add a positive power line on the protection board, which will increase the cost. At the same time, locking the positive and negative power lines on the protection board at the same time will inevitably cause contact ignition to damage the protection board, and may even affect personal and property safety. Therefore, the existing BMS system with three-terminal fuses adopts a high-side solution. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-side circuit of a lithium battery protection board for an electric vehicle. The low-side circuit has a low cost and will not damage the protection board or affect personal and property safety.

[0005] In order to solve the above problems, the following technical solutions are provided: The low-side circuit of the electric vehicle lithium battery protection board of the present invention comprises: Control templates; A charge and discharge control circuit is adapted to be connected with a lithium battery. The control template is adapted to be connected with the charge and discharge control circuit. The control template is used to control the MOS of the charge and discharge control circuit to turn on or off, thereby realizing the charge and discharge of the lithium battery. Communication circuit, used to adapt and connect with the control template to achieve external communication; A collection circuit, adapted to be connected to the control template, for collecting status information of the lithium battery and transmitting the status information to the control template; Its characteristic is that the charge and discharge control circuit contains a three-terminal fuse FUSE1, one fuse end of the three-terminal fuse FUSE1 is connected to the source of the charging MOS of the charge and discharge control circuit, the other fuse end of the three-terminal fuse FUSE1 is connected to the charging port P- / C- of the battery, and the control end of the three-terminal fuse FUSE1 is used to be connected to the positive electrode B+ of the lithium battery through the first switch circuit. When the lithium battery fails, the control module controls the first switch circuit to be turned on, a voltage difference is generated between the control end and the fuse end of the three-terminal fuse, and the three-terminal fuse is blown; The first switch circuit includes a MOS tube Q31, the drain of the MOS tube Q31 is connected to the control end of the three-terminal fuse, and the source of the MOS tube Q31 is used to connect to the positive electrode B+ of the lithium battery; the gate of the MOS tube Q31 is respectively connected to one end of the capacitor C2, one end of the resistor R59 and one end of the resistor R58, the other ends of the capacitor C2 and the resistor R59 are used to connect to the positive electrode B+ of the lithium battery, and the other end of the resistor R58 is connected to the collector of the transistor Q32; the base of the transistor Q32 is respectively connected to one end of the resistor R56 and one end of the resistor R57, the other end of the resistor R56 is connected to the control module for receiving the FUSE-Control signal generated by the control module, and the other end of the resistor 57 and the emitter of the transistor Q32 are grounded; when the lithium battery fails, the FUSE-Control signal is high, the MOS tube Q31 is turned on, a voltage difference is generated between the control end and the fuse end of the three-terminal fuse, and the three-terminal fuse is blown.

[0006] Wherein, the communication circuit contains a one-line circuit, and the one-line circuit contains an isolation optocoupler U7 and an isolation optocoupler U6; the cathode of the diode end of the isolation optocoupler U7 and the emitter of the transistor end of the isolation optocoupler U6 are both connected to the ground C- of the external circuit, the anode of the diode end of the isolation optocoupler U7 is connected to one end of the resistor R106, the collector of the transistor end of the isolation optocoupler U6 and the other end of the resistor R106 are both connected to one end of the external resistor, the other end of the external resistor is connected to a 5V power supply, and one end of the external resistor connected to the resistor R106 forms a YXT signal; the isolation optocoupler The collector of the transistor end of U7 is respectively adapted to be connected with one end of the resistor R104 and the control module, the other end of the resistor R104 is connected to a 3.3V power supply, the collector of the transistor end of the isolation optocoupler U7 sends a YXT_R signal to the control module, and the emitter of the transistor end of the isolation optocoupler U7 is grounded; the positive electrode of the diode end of the isolation optocoupler U6 is connected to one end of the resistor R95, the other end of the resistor R95 is connected to a 3.3V power supply, and the negative electrode of the diode end of the isolation optocoupler U6 is adapted to be connected with the control module, for receiving the YXT_T signal generated by the control module.

[0007] The communication circuit includes a CAN communication circuit, and the control module implements CAN communication through the CAN communication circuit.

[0008] The control module contains a main control unit and a sub-control unit. The main control unit is powered by an auxiliary power supply module, and the sub-control unit is powered by the acquisition circuit. Both the main control unit and the sub-control unit are used to receive acquisition signals from the signal acquisition circuit. The main control unit is adaptively connected to the sub-control unit. When the main control unit is working, the main control unit sends an interrupt signal to the sub-control unit, and the sub-control unit is in a sleep state. The main control unit receives the acquisition signal. When the lithium battery stops standing for 24 hours, the main control unit enters a sleep state, the auxiliary power supply circuit is disconnected, the sub-control unit is in an awake state, and the sub-control unit receives the acquisition signal.

[0009] The CAN communication circuit is adaptably connected to the sub-control unit, and the sub-control unit is adaptably connected to the auxiliary power supply circuit. The CAN communication circuit sends a CAN_test signal to the sub-control unit. When the charger is not connected, the CAN_test signal is high, the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is low, and the auxiliary power supply circuit does not work; when the charger is connected, the CAN_test signal is low, the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is high, the auxiliary power supply circuit works, and the main control unit is powered on and enters a working state.

[0010] The CAN communication circuit includes an isolation optocoupler U2 and a chip U3 of model CA-IS2062W; the transistor collector of the isolation optocoupler U2 is connected to one end of a resistor R19, the other end of the resistor R19 is connected to a power supply VCC, and the transistor collector of the isolation optocoupler U2 forms the CAN_test signal; a resistor R26 is connected in series between the CANH pin and the CANL pin of the chip U3, and the CANH pin and the CANL pin of the chip U3 are used to be connected to a charger to realize CAN communication; the CANH pin of the chip U3 is connected to one end of a resistor R23, the other end of the resistor R23 is respectively connected to the positive electrode of the diode end of the isolation optocoupler U2, and the negative electrode of the diode end of the isolation optocoupler U2 is connected to the CANL pin of the chip U3.

[0011] The anode of the diode of the isolation optocoupler U2 is connected to the cathode of the diode D3 , and the cathode of the diode of the isolation optocoupler U2 is connected to the anode of the diode D3 .

[0012] The auxiliary power supply module contains a chip U1, the input end of the chip U1 is connected to the positive electrode B+ of the lithium battery through the second switch circuit, and the output end of the chip U1 is adapted to be connected to the main control unit for powering the main control unit; the main control unit and the sub-control unit are both connected to the second switch circuit, and the PWR-1 signal is used to control the second switch circuit. When the PWR-1 signal is at a high level, the second switch circuit is in an on state, and the chip U1 is powered to power the main control unit. The main control unit generates a high-level PWR signal to control the second switch circuit to be in an on state, and at the same time, the main control unit generates an interrupt signal to control the sub-control unit to be in a sleep state. When the lithium battery stops standing for a preset time, the main control unit enters a sleep state, the PWR signal and the interrupt signal disappear, the second switch circuit is in a disconnected state, and the sub-control unit starts.

[0013] The second switch circuit includes a MOS tube Q9 and a transistor Q12; the source of the MOS tube Q9 is respectively connected to one end of the fuse FUSE2, one end of the resistor R36 and the cathode of the diode ZD1, the other end of the fuse FUSE2 is used to be connected to the positive electrode B+ of the lithium battery, the other end of the resistor R36 and the anode of the diode ZD1 are connected to the gate of the MOS tube Q9; the gate of the MOS tube Q9 is connected to one end of the resistor R39, the other end of the resistor R39 is connected to the collector of the transistor Q12, the base of the transistor Q12 is respectively connected to one end of the resistor R42 and one end of the resistor R43, the other end of the resistor R43 and the emitter of the transistor Q12 are both grounded, the other end of the resistor R42 is respectively connected to the cathode of the diode D5 and the cathode of the diode D6, the anode of the diode D5 is used to receive the PWR signal, and the anode of the diode D5 is used to receive the PWR-1 signal.

[0014] The above solution has the following advantages: 1. The three-terminal fuse circuit of the present invention is located on the negative pole loop, so there is no need to add a positive pole power line, which greatly reduces the cost. At the same time, the protection board does not effectively lock the positive pole power line, thereby completely avoiding the situation where the positive and negative pole power lines contact and ignite to cause damage to the protection board, and thus will not affect the safety of people and property.

[0015] 2. The one-line circuit used in the present invention ensures that once the protection is triggered to shut down the charging and discharging MOS, the battery end and the system end can no longer communicate directly. At the same time, the one-line circuit can be used to realize charging after successful mutual recognition with the charger. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural topology diagram of the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Figure 2It is a schematic diagram of an auxiliary power supply circuit in a low-side circuit of a lithium battery protection board for an electric vehicle of the present invention; Figure 3 It is a circuit diagram of a control template in a low-side circuit of a lithium battery protection board for an electric vehicle of the present invention; Figure 4 It is a schematic diagram of the first part of the acquisition circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Figure 5 It is a schematic diagram of the second part of the acquisition circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Figure 6 It is a schematic diagram of the third part of the acquisition circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Figure 7 It is a schematic diagram of a one-wire circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Figure 8 It is a schematic diagram of a CAN communication circuit in a low-side circuit of a lithium battery protection board for an electric vehicle of the present invention; Fig. 9 It is a schematic diagram of the first part of the charge and discharge control circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Fig.10 It is a schematic diagram of the second part of the charge and discharge control circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention and a connection schematic diagram of the three-terminal fuse; Fig.11 It is a schematic diagram of the Internet of Things communication circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; Fig.12 It is a schematic diagram of a CRG signal detection circuit in a low-side circuit of a lithium battery protection board of an electric vehicle of the present invention; Fig.13 It is a schematic diagram of the ON signal and ACC signal detection circuit in the low-side circuit of the electric vehicle lithium battery protection board of the present invention; DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0018] like Figure 1-13As shown, the low-side circuit of the electric vehicle lithium battery protection board of the present invention includes an auxiliary power supply circuit, a control template, a charge and discharge control circuit, a communication circuit, and an acquisition circuit. The auxiliary power supply circuit is connected to the control template and the positive electrode B+ of the lithium battery, and the auxiliary power supply circuit converts the voltage of the lithium battery into a 3.3V voltage for use by the control module. The control template is connected to the lithium battery and the charge and discharge control circuit, and the control template controls the MOS of the charge and discharge control circuit to turn on or off to realize the charge and discharge of the lithium battery. The communication circuit is adapted to be connected to the control template to realize external communication. The acquisition circuit is connected to the control template, and the acquisition circuit collects the status information of the lithium battery and transmits the status information to the control template.

[0019] like Figure 2 As shown, in some possible embodiments, the auxiliary power supply module contains a chip U1 of model H6203L, and the chip U1 contains peripheral circuits that drive it to work. The auxiliary power supply circuit supplies power to the entire protection board circuit. The battery voltage B+ and B- are converted into 5V through the DC-DC step-down constant voltage and constant current controller H6203L, and the 5V voltage is used to power the CAN communication circuit and the Internet of Things communication circuit. At the same time, the 5V voltage is converted into a 3.3V voltage through LDO to power the single-chip microcomputer. The specific structure of the auxiliary power supply module is as follows Figure 2 As shown, it belongs to the prior art and will not be described here in detail.

[0020] like Figure 3 As shown, in some possible embodiments, the control module includes a main control unit and a sub-control unit. The main control unit is a GD32E303C8TB chip U4 and a peripheral circuit for driving the chip U4. The sub-control unit is a HR7P153P4SA chip IC1B and a peripheral circuit for driving the chip IC1B. The specific structure is as follows Figure 4 As shown, it belongs to the prior art and will not be described here in detail.

[0021] like Figure 3 , Fig. 9 and Fig.10 As shown in FIG. 1 , in some possible embodiments, the charge and discharge control circuit includes a charge and discharge MOS and a three-terminal fuse FUSE1. The specific structure of the charge and discharge MOS is as follows: Figure 3As shown, it belongs to the prior art and will not be repeated here. One fuse end of the three-terminal fuse FUSE1 is connected to the source of the charging MOS of the charge and discharge control circuit, and the other fuse end of the three-terminal fuse FUSE1 is connected to the charging port P- / C- of the battery. The control end of the three-terminal fuse FUSE1 is used to connect to the positive electrode B+ of the lithium battery through the first switch circuit. When the lithium battery fails, the chip U4 controls the first switch circuit to turn on, and the control end of the three-terminal fuse and the fuse end generate a voltage difference, and the three-terminal fuse is blown. The first switch circuit includes a MOS tube Q31, the drain of the MOS tube Q31 is connected to the control end of the three-terminal fuse, and the source of the MOS tube Q31 is used to connect to the positive electrode B+ of the lithium battery. The gate of the MOS tube Q31 is respectively connected to one end of the capacitor C2, one end of the resistor R59 and one end of the resistor R58, and the other ends of the capacitor C2 and the resistor R59 are used to connect to the positive electrode B+ of the lithium battery, and the other end of the resistor R58 is connected to the collector of the transistor Q32. The base of transistor Q32 is connected to one end of resistor R56 and one end of resistor R57 respectively, and the other end of resistor R56 is connected to pin 25 of chip U4 to receive the FUSE-Control signal generated by chip U4. The other end of resistor 57 and the emitter of transistor Q32 are grounded. When the lithium battery fails, the FUSE-Control signal is high, the MOS tube Q31 is turned on, a voltage difference is generated between the control end and the fuse end of the three-terminal fuse, and the three-terminal fuse is blown. Specifically, the three-terminal fuse circuit is connected between the S pole of the BMS charging MOS and the charging port of the battery. When the BMS is normal, FUSE-Control outputs a low level, the C pole and the E pole of NPN transistor Q32 are disconnected, the S pole and the G pole voltage of PMOS Q31 are the same as B+, the D pole and the S pole of PMOS Q31 are disconnected, there is no voltage difference between the control end and the fuse end of the three-terminal fuse, the three-terminal fuse will not be blown, and the BMS works normally. When the BMS is abnormal, FUSE-Control outputs a high level, the C and E poles of the NPN transistor Q32 are turned on, the S-G pole voltage of the PMOS Q31 is greater than the turn-on voltage of the PMOS Q31, the D and S poles of the PMOS Q31 are turned on, the control end of the three-terminal fuse is B+, and there is a voltage difference with the fuse end, the three-terminal fuse blows, and the protection purpose is achieved.

[0022] like Figure 3 and Figure 7As shown, in some possible embodiments, the communication circuit contains a one-line circuit, and the one-line circuit contains an isolation optocoupler U7 and an isolation optocoupler U6. The cathode of the diode end of the isolation optocoupler U7 and the emitter of the transistor end of the isolation optocoupler U6 are both connected to the ground C- of the external circuit, the anode of the diode end of the isolation optocoupler U7 is connected to one end of the resistor R106, the collector of the transistor end of the isolation optocoupler U6 and the other end of the resistor R106 are both connected to one end of the external resistor, the other end of the external resistor is connected to a 5V power supply, and the end of the external resistor connected to the resistor R106 forms a YXT signal. The collector of the transistor end of the isolation optocoupler U7 is respectively connected to one end of the resistor R104 and the 12 pin of the chip U4, the other end of the resistor R104 is connected to a 3.3V power supply, the collector of the transistor end of the isolation optocoupler U7 sends a YXT_R signal to the chip U4, and the emitter of the transistor end of the isolation optocoupler U7 is grounded. The positive electrode of the diode end of the isolation optocoupler U6 is connected to one end of the resistor R95, and the other end of the resistor R95 is connected to a 3.3V power supply. The negative electrode of the diode end of the isolation optocoupler U6 is connected to the 13th pin of the chip U4, which is used to receive the YXT_T signal generated by the chip U4. The one-line circuit is a one-line protocol communication between the BMS and the outside. Two isolated optocouplers are used to ensure that once the protection is triggered to shut down the charging and discharging MOS, the battery end and the system end can no longer achieve direct communication. The working principle of the one-line circuit of this embodiment is: the external signal consists of a 5V and a 2.2K pull-up resistor. When the BMS is not connected to the one-line charger, there is no voltage at the diode end of the optocoupler U7, the transistor end is open, and the voltage received by the YXT-R end of the single-chip microcomputer is a high level of 3.3V. The single-chip microcomputer determines that the one-line charger is not connected. When the one-line charger is connected, there is voltage at the diode end of the optocoupler U7, the transistor end is short-circuited, and the voltage received by the YXT-R end of the single-chip microcomputer is a low level of 0V, and the single-chip microcomputer determines that the one-line charger is connected. The YXT-T pin of the single-chip microcomputer outputs a high-low level communication protocol. When the YXT-T pin of the single-chip microcomputer outputs a high level, there is no voltage at the diode end of the optocoupler U6, the transistor end is open, and the external YXT signal is high. When the YXT-T pin of the single-chip microcomputer outputs a low level, there is voltage at the diode end of the optocoupler U6, the transistor end is short-circuited, and the external YXT signal is low. The single-chip microcomputer output communication protocol can communicate with the one-line charger through a one-line communication. Among them, R106 is selected to ensure two points. One is that the external 5V passes through the external resistor, R106 and the ground C- of the external circuit of the optocoupler. The resistance value cannot be too large to prevent the loop current from being small and the optocoupler U7 from working. Second, the resistance value cannot be too small to ensure that after 5V passes through the external resistor and R106, the voltage of YXT is high when the main single-chip microcomputer outputs a high level, that is, the transistor end of U6 is disconnected. In this embodiment, R106 is 4.7K, and the models of the optocoupler U6 and the optocoupler U7 are LTV-217-CG.

[0023] like Figure 2 , Figure 3, Figure 4 , Figure 5 and Figure 6 As shown, the main control unit is powered by the auxiliary power supply module, and the sub-control unit is powered by the acquisition circuit. Both the main control unit and the sub-control unit are used to receive the acquisition signal of the signal acquisition circuit. The main control unit is adaptively connected to the sub-control unit. When the main control unit is working, the main control unit sends an interrupt signal to the sub-control unit, and the sub-control unit is in a sleep state. The main control unit receives the acquisition signal. When the lithium battery stops standing for 24 hours, the main control unit enters a sleep state, the auxiliary power supply circuit is disconnected, and the sub-control unit is in an awake state. The sub-control unit receives the acquisition signal. The auxiliary power supply module contains a chip U1. The input end of the chip U1 is connected to the positive pole of the lithium battery through a second switch circuit. The output end of the chip U1 is adaptively connected to the main control unit to power the main control unit. Both the main control unit and the sub-control unit are connected to the second switch circuit. The PWR-1 signal is used to control the second switch circuit. When the PWR-1 signal is at a high level, the second switch circuit is in an on state, and the chip U1 is powered to supply power to the main control unit. The main control unit generates a high-level PWR signal to control the second switch circuit to be in an on state. At the same time, the main control unit generates an interrupt signal to control the sub-control unit to be in a sleep state. When the lithium battery stops standing for a preset time, which is 24 hours in this embodiment, the main control unit enters a sleep state, the PWR signal and the interrupt signal disappear, the second switch circuit is in a disconnected state, and the sub-control unit starts.

[0024] Specifically, the second switch circuit includes a MOS transistor Q9 and a transistor Q12. The source of the MOS transistor Q9 is respectively connected to one end of the fuse FUSE2, one end of the resistor R36 and the cathode of the diode ZD1, the other end of the fuse FUSE2 is used to be connected to the positive electrode B+ of the lithium battery, the other end of the resistor R36 and the anode of the diode ZD1 are connected to the gate of the MOS transistor Q9. The gate of the MOS transistor Q9 is connected to one end of the resistor R39, the other end of the resistor R39 is connected to the collector of the transistor Q12, the base of the transistor Q12 is respectively connected to one end of the resistor R42 and one end of the resistor R43, the other end of the resistor R43 and the emitter of the transistor Q12 are both grounded, the other end of the resistor R42 is respectively connected to the cathode of the diode D5 and the cathode of the diode D6, the anode of the diode D5 is used to receive the PWR signal, and the anode of the diode D5 is used to receive the PWR-1 signal.

[0025] like Figure 3 and Figure 8As shown, in some possible embodiments, the communication circuit contains a CAN communication circuit, and the control module realizes CAN communication through the CAN communication circuit. The CAN communication circuit is adapted to be connected with the sub-control unit, and the sub-control unit is adapted to be connected with the auxiliary power supply circuit. The CAN communication circuit sends a CAN_test signal to the sub-control unit. When the charger is not connected, the CAN_test signal is high, and the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is low, and the auxiliary power supply circuit does not work. When the charger is connected, the CAN_test signal is low, and the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is high, the auxiliary power supply circuit works, and the main control unit is powered and enters the working state. The CAN communication circuit includes an isolation optocoupler U2 and a chip U3 of model CA-IS2062W. The transistor end collector of the isolation optocoupler U2 is connected to one end of the resistor R19, and the other end of the resistor R19 is connected to the power supply VCC, and the transistor end collector of the isolation optocoupler U2 forms a CAN_test signal. A resistor R26 is connected in series between the CANH pin and the CANL pin of the chip U3. The CANH pin and the CANL pin of the chip U3 are used to connect to the charger to realize CAN communication. The CANH pin of the chip U3 is connected to one end of the resistor R23, and the other end of the resistor R23 is respectively connected to the positive electrode of the diode end of the isolation optocoupler U2, and the negative electrode of the diode end of the isolation optocoupler U2 is connected to the CANL pin of the chip U3. The positive electrode of the diode end of the isolation optocoupler U2 is connected to the negative electrode of the diode D3, and the negative electrode of the diode end of the isolation optocoupler U2 is connected to the positive electrode of the diode D3.

[0026] Specifically, the chip U3 of CA-IS2062W is an isolated CAN communication chip with a built-in isolated power supply. The electrical connections at both ends cannot interfere with each other, which improves the stability of the electrical part and circuit safety. The CAN communication circuit has a CAN wake-up function, and the specific operation is as follows: When the battery stops standing for 24 hours, the BMS enters low-power mode, the auxiliary power supply circuit is disconnected, and the main microcontroller GD32F303CCT6 supplies power to the auxiliary power supply circuit and does not work. The auxiliary microcontroller is powered by the 3.3V output of DVC1117, and the auxiliary microcontroller works. At this time, the charger is not connected to the battery pack, CANH and CANL have no voltage, the optocoupler U2 does not work, and the CAN-test detection voltage of one of the auxiliary microcontroller's detection pins is high. When the charger is connected, CANH and CANL have voltage, the optocoupler U2 works, the CAN-test detection voltage is low, the PWR-1 pin of the auxiliary microcontroller outputs a high level, the auxiliary power supply circuit works, and the main microcontroller works.

[0027] In this embodiment, the acquisition circuit has AFE temperature acquisition, voltage acquisition, and current acquisition functions. The chip U5 used is DVC1117 from Jiche, which acquires the voltage, temperature, and charge and discharge current of the battery pack. The acquired information is then sent to the chip U4 through IIC communication. The specific circuit structure is as follows: Figures 4 to 6 As shown, it belongs to the prior art and will not be described here in detail.

[0028] The communication circuit includes the IoT communication circuit, CRG signal detection circuit, ON signal and ACC signal detection circuit. The specific circuit structure is as follows: Fig.11 , Fig.12 and Fig.13 As shown, it belongs to the prior art and will not be described here in detail.

[0029] The charge and discharge control circuit is that the MCU uses the AFE acquisition chip to output high and low levels of DSG and CHG, control the opening and closing of the charge and discharge MOS, and further control the charge and discharge function of the battery.

[0030] This solution is a low-side solution circuit for the lithium battery protection board. It adopts a dual protection design and charges after successful mutual recognition with the charger. It complies with the GB43854-2024 standard and protects the personal and property safety of end customers. It is low-cost, simple to assemble, reduces the locking of the power line on the BMS, and effectively prevents the power line from contacting and igniting during the battery assembly process to damage the protection board, thus protecting the personal and property safety of employees.

Claims

1. A low-side circuit of a lithium battery protection board for an electric vehicle, comprising: Control templates; A charge and discharge control circuit is adapted to be connected with a lithium battery. The control template is adapted to be connected with the charge and discharge control circuit. The control template is used to control the MOS of the charge and discharge control circuit to turn on or off, thereby realizing the charge and discharge of the lithium battery. Communication circuit, used to adapt and connect with the control template to achieve external communication; A collection circuit, adapted to be connected to the control template, for collecting status information of the lithium battery and transmitting the status information to the control template; Characterized in that the charge and discharge control circuit contains a three-terminal fuse FUSE1, one fuse end of the three-terminal fuse FUSE1 is connected to the source of the charging MOS of the charge and discharge control circuit, the other fuse end of the three-terminal fuse FUSE1 is connected to the charging port P- / C- of the battery, and the control end of the three-terminal fuse FUSE1 is used to be connected to the positive electrode B+ of the lithium battery through the first switch circuit. When the lithium battery fails, the control module controls the first switch circuit to be turned on, a pressure difference is generated between the control end and the fuse end of the three-terminal fuse FUSE1, and the three-terminal fuse FUSE1 is blown; The first switch circuit includes a MOS tube Q31, the drain of the MOS tube Q31 is connected to the control end of the three-terminal fuse FUSE1, and the source of the MOS tube Q31 is used to connect to the positive electrode B+ of the lithium battery; the gate of the MOS tube Q31 is respectively connected to one end of the capacitor C2, one end of the resistor R59 and one end of the resistor R58, the other ends of the capacitor C2 and the resistor R59 are used to connect to the positive electrode B+ of the lithium battery, and the other end of the resistor R58 is connected to the collector of the transistor Q32; the base of the transistor Q32 is respectively connected to one end of the resistor R56 and one end of the resistor R57, the other end of the resistor R56 is connected to the control module for receiving the FUSE-Control signal generated by the control module, and the other end of the resistor 57 and the emitter of the transistor Q32 are grounded; when the lithium battery fails, the FUSE-Control signal is high, the MOS tube Q31 is turned on, a voltage difference is generated between the control end and the fuse end of the three-terminal fuse FUSE1, and the three-terminal fuse FUSE1 is blown.

2. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 1, characterized in that: The communication circuit contains a one-line circuit, which contains an isolation optocoupler U7 and an isolation optocoupler U6; the cathode of the diode end of the isolation optocoupler U7 and the emitter of the transistor end of the isolation optocoupler U6 are both connected to the ground C- of the external circuit, the anode of the diode end of the isolation optocoupler U7 is connected to one end of the resistor R106, the collector of the transistor end of the isolation optocoupler U6 and the other end of the resistor R106 are both connected to one end of the external resistor, the other end of the external resistor is connected to a 5V power supply, and one end of the external resistor connected to the resistor R106 forms a YXT signal; the isolation optocoupler U7 The collector of the transistor end is respectively adapted to be connected with one end of the resistor R104 and the control module, the other end of the resistor R104 is connected to a 3.3V power supply, the collector of the transistor end of the isolation optocoupler U7 sends a YXT_R signal to the control module, and the emitter of the transistor end of the isolation optocoupler U7 is grounded; the positive electrode of the diode end of the isolation optocoupler U6 is connected to one end of the resistor R95, the other end of the resistor R95 is connected to a 3.3V power supply, and the negative electrode of the diode end of the isolation optocoupler U6 is adapted to be connected with the control module, for receiving the YXT_T signal generated by the control module.

3. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 1, characterized in that: The communication circuit includes a CAN communication circuit, and the control module implements CAN communication through the CAN communication circuit.

4. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 3, characterized in that: The control module contains a main control unit and a sub-control unit. The main control unit is powered by an auxiliary power supply module, and the sub-control unit is powered by the acquisition circuit. Both the main control unit and the sub-control unit are used to receive acquisition signals from the signal acquisition circuit. The main control unit is adaptively connected to the sub-control unit. When the main control unit is working, the main control unit sends an interrupt signal to the sub-control unit, and the sub-control unit is in a sleep state. The main control unit receives the acquisition signal. When the lithium battery stops standing for 24 hours, the main control unit enters a sleep state, the auxiliary power supply circuit is disconnected, the sub-control unit is in an awake state, and the sub-control unit receives the acquisition signal.

5. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 4, characterized in that: The CAN communication circuit is adaptably connected to the sub-control unit, and the sub-control unit is adaptably connected to the auxiliary power supply circuit. The CAN communication circuit sends a CAN_test signal to the sub-control unit. When the charger is not connected, the CAN_test signal is high, the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is low, and the auxiliary power supply circuit does not work; when the charger is connected, the CAN_test signal is low, the PWR-1 signal sent by the sub-control unit to the auxiliary power supply circuit is high, the auxiliary power supply circuit works, and the main control unit is powered on and enters a working state.

6. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 5, characterized in that: The CAN communication circuit includes an isolation optocoupler U2 and a chip U3 of model CA-IS2062W; the transistor collector of the isolation optocoupler U2 is connected to one end of a resistor R19, the other end of the resistor R19 is connected to a power supply VCC, and the transistor collector of the isolation optocoupler U2 forms the CAN_test signal; a resistor R26 is connected in series between the CANH pin and the CANL pin of the chip U3, and the CANH pin and the CANL pin of the chip U3 are used to be connected to a charger to realize CAN communication; the CANH pin of the chip U3 is connected to one end of a resistor R23, the other end of the resistor R23 is respectively connected to the positive electrode of the diode end of the isolation optocoupler U2, and the negative electrode of the diode end of the isolation optocoupler U2 is connected to the CANL pin of the chip U3.

7. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 6, characterized in that: The anode of the diode of the isolation optocoupler U2 is connected to the cathode of the diode D3 , and the cathode of the diode of the isolation optocoupler U2 is connected to the anode of the diode D3 .

8. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 5, characterized in that: The auxiliary power supply module contains a chip U1, the input end of the chip U1 is connected to the positive electrode B+ of the lithium battery through the second switch circuit, and the output end of the chip U1 is adapted to be connected to the main control unit for powering the main control unit; the main control unit and the sub-control unit are both connected to the second switch circuit, and the PWR-1 signal is used to control the second switch circuit. When the PWR-1 signal is at a high level, the second switch circuit is in an on state, and the chip U1 is powered to power the main control unit. The main control unit generates a high-level PWR signal to control the second switch circuit to be in an on state, and at the same time, the main control unit generates an interrupt signal to control the sub-control unit to be in a sleep state. When the lithium battery stops standing for a preset time, the main control unit enters a sleep state, the PWR signal and the interrupt signal disappear, the second switch circuit is in a disconnected state, and the sub-control unit starts.

9. The low-side circuit of the electric vehicle lithium battery protection board as claimed in claim 8, characterized in that: The second switch circuit includes a MOS tube Q9 and a transistor Q12; the source of the MOS tube Q9 is respectively connected to one end of the fuse FUSE2, one end of the resistor R36 and the cathode of the diode ZD1, the other end of the fuse FUSE2 is used to be connected to the positive electrode B+ of the lithium battery, the other end of the resistor R36 and the anode of the diode ZD1 are connected to the gate of the MOS tube Q9; the gate of the MOS tube Q9 is connected to one end of the resistor R39, the other end of the resistor R39 is connected to the collector of the transistor Q12, the base of the transistor Q12 is respectively connected to one end of the resistor R42 and one end of the resistor R43, the other end of the resistor R43 and the emitter of the transistor Q12 are both grounded, the other end of the resistor R42 is respectively connected to the cathode of the diode D5 and the cathode of the diode D6, the anode of the diode D5 is used to receive the PWR signal, and the anode of the diode D5 is used to receive the PWR-1 signal.

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