Fixing conmutation for high voltage switching with power mosfet

Thread Starter


Joined Jan 30, 2019
Hello everyone, and thnaks for reading. I have an issue with a charge circuit for a capacitor as load. I want to switch approximately 400 V DC to charge a 1000 uf 600 V capacitor. I'm using a power mosfet for this application. I need it to charge instantly as soon as it turns on, or in a few milliseconds. The problem is that to do that i saturate the mosfet and then turn it off using a 10V signal to Gate source to drive the mosfet, it works the first time, as soon as I send the signal it charges, but the problem is that the capacitor gets damaged and all the terminals get shorted. The mosfet is a IRPF460, it is a 500V, 20 A and 0.27 ohm mosfet, i choose it because it seems to be the correct for this application. I put a 10 A fuse next to the mosfet to verify if it was being damaged by some inrush current but it wasn't because ass soon as I turn on the mosfet the fuse didn't pop and the current i measure was not above 5.5 A, and the mosfet brokedown anyway. THe only think that could be causing the problem is the conmutation therefore, the problem must be in Gate-Source or the driving part. Another think that called my atenttion is that if i apply almost 8 V to Gate-Source the capacitor charges but only to a half of the voltage with a single pulse of a button., and the mosfet does not suffer any damage. The driving signal for the mosfet will be a pulse that can go from 55 ms to 1 sec. so it has to charge the cap within these times too. I looked for snubber circuits that can handle this but the ones i found were parallel to the mosfet and would get 400 V as soon as the power supply is conected, so i would need components to deal with this and i dont have them. Even if i would get them i dont know if it would work. THis circuit will have another part to discharge the capacitor, but first i need the charge to work. I would like to know if i can implement some kind of snubber for Gate-Source or what can i do to avoid damaging the mosfet and switching the voltage needed. I think the mosfet could be leavin the safe operating area SOA when switching. Please I need help. Thank you all, again.

This is my circuit: