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building a power supply need suggestions on parts


Right, I found a heavy gem at a car boot sale: a 12V 200VA transformer. so I'm planning to use it to build a nice powerful bench power supply with a switch mode regulator.

to ensure I get a good 15V out of it I may well use a doubling rectifier with very large caps but I'm yet to measure the output. I could also do a low voltage  high current output/regulator using a full wave rectifier.

Any suggestions on switchmode regs that can handle 12V 20A and maybe a 5V 40A ?

I'm also looking to make each output current regulated as well so that the max current can be set, now I can do high side current sensing but how do I integrate the current control into the SMPS feedback

For a voltage source, current feedback control can be an inner loop of the voltage controller.
The voltage regulator generates a current reference, and the current controller generates the duty-cycle.
Both controllers have limited output.
That's what is usually done in variable voltage supplies with variable current limit. They can act as both voltage sources (until the current limit is reached) and current sources (until the voltage reference is reached), following the limit which comes first.

You're already using a big iron core transformer, what's wrong with linear regulation? Switch mode is so noisy.

Mr J:
I've used a copy of astron's circuit in the past. Cheap, easy, simple. The iron transformer already has a huge loss, go linear :)


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