Arfa Daily wrote:



What I've never really understood, is what supposed advantages IGBTs have
over FETs. A while ago, I had the misfortune to work on a switcher that
was in a Yammy powered speaker. It used a pair of IGBTs that were about
eight quid apiece from memory. Much like the OP's induction heater, it
would run fine for a while, and then the stupid things would just destroy
themselves again - and I mean violently, legs actually blown off, and all
that good stuff. I mend a lot of switch mode power supplies, and for the
most part, their failure modes and what needs to be done to obtain a
reliable fix, hold no mysteries for me. But after about the fourth set of
devices that I put in the Yammy, along with just about every other
component in the surrounding area, I gave up on it. Many switchers of
similar size and ratings, use an almost identical topology, but with a
pair of FETs. Typically a couple of quid apiece, and in my estimation,
*much* more robust. So with power FETs rated to 800 volts and staggering
amounts of amps being readily available almost for pence, why would anyone
actually design with IGBTs ?
Below 400 V there is probably no benefit to an IGBT. At 400 V and above,
MOSFETs start to show a higher on-resistance. The higher the breakdown
voltage, the higher the on resistance. IGBTs have a constant Vce drop of
about 2V or better, up to several times continuous rated current. That
starts to look real good in serious power devices like motor drives.

IGBTs in an audio amp sounds really odd to me, I'll bet a set of
FETs could have been dropped into it perfectly.

Jon