Power MOSFETs are difficult to apply to short-circuit protection of lithium batteries in electric vehicles

(1) Large short circuit current

In an electric vehicle, the voltage of the lithium iron phosphate battery is generally 36V or 48V, and the short-circuit current varies with the capacity of the battery, the internal resistance, the parasitic inductance of the line, and the contact resistance at the time of the short circuit, and is usually several hundred or even thousands of amperes.

(2) Short circuit protection time should not be too short

In the application process, in order to prevent the transient overload, the short circuit protection circuit is malfunctioned. Therefore, the short circuit protection circuit has a certain delay. And due to the error of the current sense resistor, the current detection signal and the delay of the system response. Generally, the short-circuit protection time is set to 200μs to 1000μs according to different applications. This requires the power MOSFET to work safely at this time under high short-circuit current, which also increases the design difficulty of the system.