[sdiy] +15 -15 DC Power supply, adding +5 DC

Simon Brouwer simon.oo.o at xs4all.nl
Mon Nov 10 22:13:37 CET 2008

Cory Scott schreef:
> Hello
> So i have a +15 and -15 200ma power supply and now i need a +5 is 
> there any way i can build a small circuit on the side
> to get that +5 from the same transformer?
If you need more than 200 mA then this would be possible with a 
switching regulator such as LM2675 
Assuming efficiency of 80%, if you draw, for example, 200 mA at the 5V 
output, the circuit will take 83 mA at the +15V input (if you can 
connect it to the higher, unregulated positive voltage, even better).

A drawback of this approach is switching noise. It may not be that easy 
to keep it out of your audio circuits.

Vriendelijke groet, 
Simon Brouwer. 

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