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I need a basic circuit diagram for a variable DC power supply, can anybody help?
Hi there.
I'm building a variable lab power supply witch is 70 Volts and 35 Amps output AC
I have found my 4 diodes and capacitor that can handle this power for my rectifier circuit for my DC current, however its been a wile since I've made any power supply's.
I've been trying to find a basic circuit to get my variable resistor working so that I can control the voltage from 1 volt all the way up to 70 volts smoothly, also I'll be pushing 35 amps through it and its important that I don't lose to much current wile achieving this.
My power supply is pretty much done apart from my voltage regulator.
If anybody could help me out with a few simple circuits I'd be very grateful.
Thanks in advance
70 volts 35 amp is a huge amount of energy. It's certainly not trivial to build a voltage regulator for these specs and even if you do, the ripple voltage under load is gonna be horrible.
Most linear voltage regulator go up to 35 volts max and about 1.5 amp.
A switched mode regulator could be possible, but that would be fairly complex and you would have to find exotic and expensive power transistor able to switch 35 amps under load.
There is no reason why a lab power supply should do 70 volts 35 amps. Most lab power supply are 25 volts and 1 or 2 amps and that's plenty.
I recommend a more 'traditional' design. Probably something like that:
http://www.aaroncake.net/circuits/supply.asp
However, if for some reason you really need 70 volts and 35 amps. One solution would be to use a variac (variable transformer) able to push 35 amps and a suitable rectifier and filter capacitor(s).
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