George White wrote in a message to Jonathan De Boyne Pollar:
 GW> In a switching regulator the controlling element is a compound 
 GW> of two devices, a transistor, FET or thyristor used as a switch 
 GW> and an inductor. 
Except that you can do this sort of thing with no inductors,  using 
capacitors as charge storage devices.  Look at the ICL7660 (?) chip for an 
example (I hope I'm remembering that number right) or any number of Maxim 
parts,  that are designed to do this on small basis.
 GW> The variation of the on/off ratio of the switch, in conjunction 
 GW> with the inductor is used to control the amount of charge (== 
 GW> power) transferred from the supply to the load. 
Aren't there also units which vary the frequency,  rather than the pulse 
width?  I seem to remember both kinds being mentioned in the literature.

 GW> I have some old Cromemco "boat anchor" system boxes here using 
 GW> linear supplies. The transformer alone is about the same size 
 GW> as a standard PC power supply 
And one hell of a lot heavier!
 GW> (and they are mostly empty space these days). 
For airflow.
 GW> The smoothing capacitors are enormous, they take up even more 
 GW> space than the transformer. The requlation was done on the S100 
 GW> cards, so for an output capability around that of a current PC 
 GW> it uses several times as much space and dissapates many times 
 GW> the amount of power.
Yep,  but they sure were a lot quieter!
This is drifting a bit off the topic here,  but if you like we can take it up 
in the fido ELECTRONICS echo...
email: roy.j.tellason%tanstaaf@frackit.com 
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