I want to control one universal dc motor (vacuum cleaner Motor 220V,8A) with AVR micro and one high power mosfet. So the power part schematic is here:


But the problem is here when input voltage going to near 220V the mosfet is breaking down. So as you can see (top of the photo) I have made one ac to dc converter without a transformer and only with one bridge rectifier and two cap (1th 660 uF2th 330 nF ), could be the problem form miss converting and harmonics in dc voltage which going to MOSFET (not complete DC which have some harmonics)?

I guess some part of this problem came from here!!!

My Mosfet is here:


So what could I do for it's protecting from inrush current which came back form motor solenoids, could I use zener diode in this high power (8A,220V) or there are better way?

Edited: According to its datasheet, does it have not any anti parallel fast diode, and how much protection it would have with this kind diodes?

I changed MOSFET to IRFP460 (20A 500V, 80A pulse drain current) So it's working in voltage below 180V AC (Auto-transformer) but in 220V AC It's Mosfet broken down, SO i guess there is some problem in the source power for drain of Mosfet, i Guess there is no enough DC Voltage, So the cap i used there are 1300 uF, Dose i need to increase it's amount for reaching Better DC voltage for power supply of Mosfet (drain-source)?

Another Que:

Somebody did say, you must use 7 X multiplier of your motor normally current Mosfet , which means i must use 8x7=56 A Mosfet for driving this kind DC motors, So dose it correct, any kind of this rules ?!!!

Thanks a lot.

  • 4
    \$\begingroup\$ I don't see any path for inductive or regenerative energy when the switch turns off. So that probably spikes your voltage on the drain and kills your FET. There are other possibilities as well, but I would start there. \$\endgroup\$
    – John D
    Jan 4, 2017 at 22:46
  • \$\begingroup\$ What is between the AVR and the FET (on 'PWM' connector)? \$\endgroup\$ Jan 4, 2017 at 22:53
  • \$\begingroup\$ what kind diode (zener or ... ) for what amount current is needed for mosfet protection needed? \$\endgroup\$ Jan 5, 2017 at 5:18
  • \$\begingroup\$ You need a serious amount of capacitance on that diode bridge rectifier output.. like tens of milliFarads at least. The motor needs a flyback diode as Jack Creasey pointed out. I would go for a 10A 400V diode at least. Why do you have an IGBT anyway? You probably want an N Channel MOSFET (standard metal oxide one.. not IGBT style) with 400V and 30-50A rating. Remember if the motor is rated at 8A, it probably pulls 50A pulse when it starts up. \$\endgroup\$
    – KyranF
    Jan 5, 2017 at 6:16

1 Answer 1


I'd suggest your problem is nothing to do with inrush current. You have no protection for the G20N50C, and are driving a highly inductive load. Put commutation protection across the motor:

enter image description here

What is the driving PWM schematic? I hope the R4_1G is not in any way defining the turn on charge timing for the G20N50C gate. For applications such as you have you need very fast gate charge and discharge times.


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