SMPS -- "safety and the 5 cent zener"

[jackinnj]

that's about 0.04 Euro --

Sanjaya Maniktala's (one of the head engineers at Nat Semi) book "Switching Power Supply Design and Optimization" just reached my doorstep via Amazon -- this will surely become a reference book like Pressman et. al.

In the final chapter he discusses reliability, testing and safety -- something which I seem to harp on, but especially important in the case of SMPS (and all you folks who would like to build off-line switcheres)

[Eva]

The 5 cent zener or rectifier that works at 100ºC near its dissipation limit and causes a $500 fault when it blows???

[jackinnj]

Sanjaya discusses a situation in which at startup an input pulse on the drain of the switching fet charges the gate ! the result, several hundred words later, is catastrophic failure with breakdown of the isolation supposedly provided by the optocoupler. The example comes from the type of situations in which UL (Underwriter's Laboratory in the US -- the standard bearer for insurance companies) smashes a component to see what happens.


I innocently thought well of my voltage dividers on power supply error amplifiers to be pretty stiff -- until Sanjaya demonstrated what actually happens (and can happen) with the error amp.

The book is expensive, but very, very well written.