Lithium battery low-side discharge driving enhancement circuit

Abstract

The utility model discloses a low-side discharge driving enhancement circuit of a lithium battery, which belongs to the field of a battery management system (BMS), is arranged between a battery cathode (BAT-) of a battery protection board and a load ground (P-), and comprises a level conversion circuit, a discharge switch acceleration circuit and a surge absorption circuit. The level conversion circuit and the discharge switch acceleration circuit comprise a switching diode D1, an NPN triode Q1, a PNP triode Q2, an NPN triode Q3, an NPN triode Q4, a discharge NMOS tube Q5 and resistors R1-R9. The surge absorption circuit comprises a capacitor C1, a resistor R10 and a TVS tube D2. The circuit solves the problem that the driving capability of discharge driving provided by a battery management chip is insufficient, and realizes rapid switching control of a discharge MOS switching tube in a heavy load application scene.

Description

Technical Field

[0001] This utility model relates to the field of battery management system (BMS), specifically to a lithium battery low-side discharge drive enhancement circuit. Background Technology

[0002] A Battery Management System (BMS) is a system that monitors and manages batteries, especially lithium-ion battery packs. It collects and calculates parameters such as voltage, current, temperature, and State of Charge (SOC) to control the charging and discharging process, preventing overcharging, over-discharging, overcurrent, or overheating, thus extending battery life and protecting the battery. Specifically, the BMS controls the discharge MOSFET switch by simulating a front-end AFE chip. When the AFE chip detects abnormal conditions such as a short circuit, overcurrent, or undervoltage, it immediately turns off the discharge MOSFET via MOSFET drive, cutting off the load circuit and preventing further deterioration. Conversely, when the external abnormal condition disappears, it turns on the discharge MOSFET via MOSFET drive to restore the load discharge circuit.

[0003] In heavy-load applications, if the discharge MOSFET cannot turn off quickly and instantly in the event of overcurrent or short circuit, the large current will not only burn out the discharge MOSFET, but may also damage the battery protection board and other related components in the load circuit. Besides the requirement for rapid turn-off, the discharge MOSFET driver also requires rapid turn-on in various applications. Because the driving capability of the MOSFET driver circuit integrated on-chip in the analog front-end AFE chip is limited, it cannot meet the high requirements for discharge switching speed in these applications.

[0004] This invention aims to provide a lithium battery low-side discharge drive enhancement circuit, which effectively solves the problem of discharge MOSFET drive switching speed in heavy-load application scenarios. At the same time, it can reduce voltage and current spikes and glitches, indirectly improve EMI characteristics, and thus enhance the safety of the BMS system. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of insufficient driving capability of the discharge drive provided by the battery management chip, and to realize fast switching control of the discharge MOS switch in heavy-load application scenarios.

[0006] The technical solution of this utility model is to add a drive enhancement circuit to the low-side discharge drive port of the battery management chip. The drive circuit includes a level conversion circuit, a discharge switch acceleration circuit, and a surge absorption circuit.

[0007] A further technical solution includes a lithium battery low-side discharge drive enhancement circuit, comprising a switching diode D1, an NPN transistor Q1, a PNP transistor Q2, an NPN transistor Q3, an NPN transistor Q4, a discharge NMOS switch Q5, and resistors R1~R9. The emitters of transistors Q1, Q3, and Q4 are grounded. The bases of transistors Q1 and Q3 are connected to the DSG discharge control terminal output by the AFE analog front-end chip via resistors R2 and R1, respectively. The collector of transistor Q1 is connected to the emitter of transistor Q2 via resistor R3. The emitter of transistor Q2 is connected to a 12V independent power supply through a switching diode D1. The P and N terminals of the switching diode are connected to the 12V independent power supply and the emitter of transistor Q2, respectively. A resistor R4 is connected between the emitter and base of transistor Q2. The collector and emitter of transistor Q3 are connected to the base of transistor Q2 through a resistor R5. The collector and emitter of transistor Q2 are connected to the gate of discharge MOSFET Q5 through series resistors R6 and R9. The collector of transistor Q4 is connected to the gate of discharge MOSFET Q5 through resistors R7 and R9.

[0008] A further technical solution is a lithium battery low-side discharge drive enhancement circuit, which includes a capacitor C1, a resistor R10, and a TVS diode D2. The resistors C1 and R10 are connected in series and then connected across the source and drain of the discharge MOSFET Q5 to form an RC absorption circuit. At the same time, a TVS diode D2 is connected in parallel between the source and drain of the discharge MOSFET Q5.

[0009] The beneficial effects of this invention are as follows: The driving circuit effectively enhances the current driving capability through the transistor circuit, quickly completing the charging or discharging process of the gate charge. At the same time, it converts the high level of the discharge control signal (DSG) output by the AFE analog front-end chip into a +12V independent power supply to enhance the pull-up driving capability and effectively solve the problem of the switching speed of the discharge MOSFET drive in heavy-load application scenarios. Meanwhile, the TVS transistor and RC absorption circuit connected in parallel across the discharge MOSFET can protect the discharge MOSFET, suppress high-voltage surge impact, and reduce voltage and current spikes, indirectly improving EMI characteristics and thus enhancing the safety of the BMS system. Attached Figure Description

[0010] Figure 1 This is a circuit diagram of a lithium battery low-side discharge drive enhancement circuit according to the present invention. Detailed Implementation

[0011] The technical solution of this utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0012] This utility model is a lithium battery low-side discharge drive enhancement circuit, which is installed between the battery negative terminal (BAT- terminal) and the load ground (P- terminal) on the battery protection board. The drive circuit includes a level conversion circuit, a discharge switch acceleration circuit, and a surge absorption circuit.

[0013] like Figure 1 As shown, the lithium battery low-side discharge drive enhancement circuit includes a switching diode D1, an NPN transistor Q1, a PNP transistor Q2, an NPN transistor Q3, an NPN transistor Q4, a discharge NMOS transistor Q5, and resistors R1~R9. The emitters of transistors Q1, Q3, and Q4 are grounded. The bases of transistors Q1 and Q3 are connected to the DSG discharge control terminal output by the AFE analog front-end chip through resistors R2 and R1, respectively. The collector of transistor Q1 is connected to the emitter of transistor Q2 through resistor R3. The emitter of transistor Q2 is connected to a 12V independent power supply through a switching diode D1. The P and N terminals of the switching diode are connected to the 12V independent power supply and the emitter of transistor Q2, respectively. A resistor R4 is connected between the emitter and base of transistor Q2. The collector and emitter of transistor Q3 are connected to the base of transistor Q2 through a resistor R5. The collector and emitter of transistor Q2 are connected to the gate of discharge MOSFET Q5 through series resistors R6 and R9. The collector of transistor Q4 is connected to the gate of discharge MOSFET Q5 through resistors R7 and R9.

[0014] An RC snubber circuit consisting of a capacitor C1 and a resistor R10 connected in series is connected in parallel across the source and drain terminals of the discharge MOSFET Q5, and a TVS diode D2 is connected in parallel thereafter. This is used to protect the discharge MOSFET, suppress high voltage surge impacts, reduce voltage and current spikes, indirectly improve EMI characteristics, and thus improve the safety of the BMS system.

Claims

1. A lithium battery low-side discharge drive enhancement circuit, installed between the battery negative terminal (BAT-) and the load ground (P-), characterized in that, The circuit includes a level conversion circuit, a discharge switch acceleration circuit, and a surge absorption circuit. The level conversion circuit and the discharge switch acceleration circuit include a switching diode D1, an NPN transistor Q1, a PNP transistor Q2, an NPN transistor Q3, an NPN transistor Q4, a discharge NMOS transistor Q5, and resistors R1~R9. The emitters of transistors Q1, Q3, and Q4 are grounded. The bases of transistors Q1 and Q3 are connected to the DSG discharge control terminal output by the AFE analog front-end chip through resistors R2 and R1, respectively. The collector of transistor Q1 is connected to the emitter of transistor Q2 through resistor R3. The emitter of transistor Q2 is connected to a +12V independent power supply through the switching diode D1. The P and N terminals of the switching diode... The +12V independent power supply and the emitter of transistor Q2 are connected respectively. A resistor R4 is connected between the emitter and base of transistor Q2. The collector and emitter of transistor Q3 are connected to the base of transistor Q2 through a resistor R5. The collector and emitter of transistor Q2 are connected to the gate of discharge MOSFET Q5 through series resistors R6 and R9. The collector of transistor Q4 is connected to the gate of discharge MOSFET Q5 through resistors R7 and R9. The surge absorption circuit includes capacitor C1, resistor R10, and TVS diode D2. Resistors C1 and R10 are connected in series between the source and drain of discharge MOSFET Q5 to form an RC absorption circuit. At the same time, TVS diode D2 is also connected between the source and drain of discharge MOSFET Q5 to suppress voltage spikes.

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