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Having just designed and built a 0-50VDC 0-5A fully regulated LINEAR 
power supply I can quite rightly say that any work in this power range 
and above, serious consideration has to be given to getting the wasted 
heat out of the system.

The power supply in question was designed for a magnet ramp supply, so 
noise was a serious consideration and therefore a switching supply was 
out of the question. The DC input voltage was 65VDC.

The final design used an OPA541 pwr opamp as the series pass regulator, 
being driven by an ultra-stable, low-noise reference. Three MJ15003's in 
parallel were used as the pass elements. Current regulation was achieved 
using a fully floating/high side P-Channel MOSFET regulator. The unit 
was tested in abuse conditions to destruction several times. The two 
major concerns were the amount of latent heat that had to be removed and 
load dump due to the switching and disconnection of two very large 
electro magnets. This necessitated forced air cooling, both feed and 
drag fans at either end of the system and active surge clamping on the 
output to protect the power supply.

For your application a similar configuration with an appropriate number 
of pass elements should be do-able.

Nino.

Vasile Surducan wrote:
> On 9/19/05, Dave King <KingDWS@shaw.ca> wrote:
> 
>>>>>>Input range is 20-48 and required
>>>>>>output is 12vdc @ 10Amps with a max of say 15-20A.
>>>
>>>Can you tighten up that spec?  15-20A for how long?  With what
>>>sort of behavior on the output voltage?  Otherwise, you're looking
>>>at a 12V@20A power supply, which is twice the nominal 12V@10A...
>>
>>I need 10 amps (prob 99%)  but it should be capable of higher peaks
>>without letting the smoke out. The input voltage is going to be from 20-48
>>and not steady. I have no control over that one. I did look at telcom stuff
>>but the input seems pretty fixed around 48.
>>
>>Switching type is the only way to go on this as far as I can tell. It would
>>be
>>nice to keep the efficiency pretty high 
> 
> 
>   this will produce a high output noise, of course
> 
> 
>>and the heat low. 
> 
> 
>   360W of switching will not be low heat at all, so think to forced air cooling.
> 
> I caught myself 
> 
>>looking
>>at Romans circuit the other night wondering if a few different bits might
>>make
>>it work. 
> 
> 
> Nothing much appreciated than a good joke. Take a look on some
> schematics about how are designed PC power supplies. Then try to
> compute the switching circuitry for
> much higher current and lower input voltage. You need at least two
> power switching devices working in push-pull fashion. 20V and 400W
> means 20A switched. So you need some low Rds devices, else will be
> 0.1ohm Rds x 20Ax20A = 40W dissipated by one device. Also rectifiers
> must be carefully chosen, as well as coil designs. Avoiding core
> saturation is must at this power. If it's the first time for you, be
> prepared for a long and difficult project.
> 
> success,
> Vasile
> 

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