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Had run into a very serious field failure issue a decade ago due to IXYS FETs used in a phase-shifted ZVS bridge topology. Eventually, the problem was tracked to failure of the FETs' body diode when the unit operated at higher ambient temperature.
I had small hills of dead MOSFETs and the directly attached controllers. When the first power MOSFETs emerged in 1979, I blew-up so many that I almost wrote them off. They had some real issues with D-S voltage overstress. They have come a long way since.
I tell customers that at least 50% of the design effort is the layout and routing by someone who knows what they are doing. Layer stackup is very critical for multiple layer designs. Yes, a solid design is required. But the perfect design goes down in flames with a bad layout. It is best in one of his early books that you have to "think RF" when doing a layout.
I have been designing power supplies for over 15 years now. We do mostly off line custom designs ranging from 50 to 500W. Often used in demanding environments such as offshore and shipping. I think we are the lucky ones who got the chance to learn designing power supplies using the simple topologies like a flyback or a forward converter. If we wanted to make something fancy we used a push-pull or a half bridge.
I never just put power to a first prototype and see what happens. Smoke and loud sounds are the most likely result and then you just know that something was not perfect. So how would you test the next prototype sample?
After that he certainly never forgot this key lesson: never attempt to measure FET current by putting a current probe in its source--- put it on the drain side. It was that simple. The same unit never exploded after that, just to complete the story.
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