Switching Regulators for Poets -or- They Told Me I Couldn’t Leave the Last Page Blank
Linear Technology App Note #25 (PDF) — Jim Williams’ first cartoon, along with some great advice on designing switched-mode power supplies! Kent Lundberg has a great analysis of this appnote on his excellent Reading Jim Williams blog too.
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App note 25 changed my life when I first read it in 1999. It was my first power supply for an embedded system. The input was between 48 – 250VDC and the output requirement was for 1A at 5V. The other requirements were no custom magnetics and no heat sinks since this was a sealed unit.
Sadly, I ignored all his advice in favor of "simpler" systems.
Oh the fires I started. 2 weeks of slavish work and I learned how easily the efficiencies of SMPSs can be lost in anything. Literally anything. Caps were a favorite. Tantalums are especially pretty while ablaze.
A senior engineer finally took up the mantel. He used custom magnetics and 30A FETs to prevent heat build up. Today, I think I could bang this out in a day. Understanding the true nature of the beast is key, and very few other documents make that clear.