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

(1) High Short-Circuit Current In electric vehicles, lithium iron phosphate batteries typically operate at voltages of 36V or 48V. When a short circuit occurs, the current can reach several hundred to even thousands of amperes. This high current is influenced by factors such as battery capacity, internal resistance, parasitic inductance in the wiring, and contact resistance during the fault. Such conditions require robust protection mechanisms to prevent damage to the system. (2) Appropriate Delay for Short-Circuit Protection During normal operation, it's essential to avoid false triggering of the short-circuit protection due to transient overloads. Therefore, the protection circuit usually includes a delay mechanism. Additionally, the accuracy of the current-sensing resistor and the system's response time can affect the timing of the protection. As a result, the short-circuit protection time is generally set between 200μs and 1000μs, depending on the application. This requires power MOSFETs to handle high currents safely during this period, which increases the complexity of the overall design. Engineers must carefully balance speed, reliability, and safety when implementing these systems to ensure long-term performance and user safety.

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