Protect MOSFETs in heavy-duty inductive switch-mode circuits

摘要

The MOSFET power switch is commonly the most vulnerable part of a new switched-mode high-power circuit. One threat for this device is exceeding the value of the maximum allowed pulse current. You cannot exceed this limit, even for pulse durations as short as 10 nsec. You could still thermally damage the MOSFET with a high duty cycle even when the drain-to-source current has a value between the peak and the dc ratings. The FET might eventually enter self-oscillations at a frequency, which might be an order of magnitude higher than your planned operating repetition rate. To protect the FET, you can limit the duty cycle by ac coupling the FET-driver circuit.