some comments on linear power supplies: was : RE: [sdiy] Power Supply Design Questions

[Ingo Debus]

Czech Martin wrote:
> A voltage source actually is a short.
> Not to zero volt but to the voltage
> of the source. If you connect another
> voltage source to it, infinite current will
> flow, if the voltages are not exactly equal.

But when the rectifier starts conducting, the voltages are 
appoximately equal. But: at this moment the transformer voltage is 
rising. With a smaller cap this happens earlier than with a bigger 
cap, and then the transformer voltage (it's a sine) is steeper. This 
might compensate for the reduction of current caused by the smaller 
cap value a bit. I = C*dV/dt. Lower C but higher dV/dt.
So Tietze-Schenk might be right, and the peak current does indeed not 
depend on the cap value (or I just got Tietze-Schenk wrong here).

Heck, such a simple circuit but so difficult to understand.

Ingo