On Fri, 6 May 2005, Russell McMahon wrote:

>> I'd like to design for my own use a 5A laboratory power supply, and
>> control it digitally, via a DAC (not a digital potentiometer, since
>
>> ...it, and the more I'd rather prefer (intuitively/instinctively at least)
>> a boosted opamp solution instead.
>
> For a lab supply I like the idea of a power supply that sucks as well as 
> blows so boosted op-amp sounds good.

Except the current limiting becomes interesting in this configuration. 
Usually you want adjustable current limiting (different for sink & 
source).

> Consider using a DC coupled amplifier designed for audio amplifier solutions. 
> Lowish cost for the power.

Yes but see above. I have put a few hours into lab work related to this 
and it is not so easy imho. Relatively wideband audio amps will 
oscillate easily when used with a reactive load (f.ex. small dc motor or 
solenoid). The funny things that must be done to obtain adjustable 
current limiting do not help at all with this. I could not make a 
'simple' circuit that satisfies all the requirements from existing 
(integrated) audio amps.

Instead, I used a 'classic' linear power supply scheme and a separate 
'class A' adjustable sink (adjustable only in current but shunt type 
voltage regulation can be added easily). The main features were the 
heatsinks ... my supply was max 100W (3A @ 30V).

Peter
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