I'm low-side driving a 24V, 1.2A DC solenoid with a 30V MOSFET. I'd like to protect the MOSFET with a zener diode across the source and drain (cathode to drain, anode to source). If I select, say, a 27V zener, how do I spec the power rating? Is there a way to calculate how much current will be flowing through it when the MOSFET shuts off and the flyback voltage rises above 27V? My MOSFET and (randomly selected) 500 mW zener work fine when driving a 24V, .8A solenoid, but using the 1.2A solenoid fries the zener. Thanks for any tips.
Joined: Tue. Apr 1, 2003
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