throbscottle
Well-Known Member
I'm in the last 1% of my hybrid psu design, and think I have found out a problem that must affect many variable bench psu's.
So, take an adjustable psu with an emitter follower output, connect a capacitor across the output, turn up the voltage, quickly turn down the voltage. Suddenly the emitter of the output transistor is now at a much higher voltage than it's base, possibly exceeding its vbe and killing it.
So I think that's why I keep blowing output transistors anyway. Does the theory hold water? Does it affect all variable psu's? Or is it a nasty trick I have uncovered because the pre-regulator lowers the collector voltage when the output is turned down?
So, take an adjustable psu with an emitter follower output, connect a capacitor across the output, turn up the voltage, quickly turn down the voltage. Suddenly the emitter of the output transistor is now at a much higher voltage than it's base, possibly exceeding its vbe and killing it.
So I think that's why I keep blowing output transistors anyway. Does the theory hold water? Does it affect all variable psu's? Or is it a nasty trick I have uncovered because the pre-regulator lowers the collector voltage when the output is turned down?