High power adjustable switching power supply (SMPS) 3-60V 40A


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I'm looking for some help on this SMPS Circuit,


I've built the circuit on a PCB and everything works fine Voltage regulation etc...

But as soon as I attach a load (A 60 Watt 12V Light Bulb) in this case the IGBTs short out and die, all 3 legs are shorted together.

I tried with 600v Mosfets as well but the same still happens.

Any Help would be much appreciated.



  • SMPS.jpg
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This is a two switch converter to my believe it is very immune to shoot trough. Your problem is very odd. It would be of much help if you could post some oscilloscope shots at least at idle. without anything to view I cannot imagine what is happening.
IGBTs blowing as soon as you attach a load could be the transistors exceeding their voltage rating or they are not switched off properly between each cycle or the dead time is not sufficient.

Try conducting tests with cheaper mosfets until you settle out with the problem as the short occurs too quickly to see it. I suggest you put a current limiter such as a 100w bulb with the high voltage rail so that in the event of a short it will save the fets. This may bring the case of cutting a trace on the pcb to do it.

You will be needing to scope out the gates and even the transformer primary. For safety if you have space put a one or two turn coupling loop around the trafo so that you can attach the scope safely without blowing it. With this you will have the chance to see what is happening.

Good luck