Re: Variable Bench Switch Mode Power Supply


"legg" <legg@xxxxxxxxxxxxxxx> wrote in message
news:6sq464h7bpmlsj03p71bqti1ubih0et4c0@xxxxxxxxxx
On Wed, 25 Jun 2008 06:04:52 +0100, "Scrim" <spam@xxxxxxxx> wrote:

That'll be a 'no' then, I guess!
What about less ambitious but still widely variable switch mode designs?

Scrim

"Scrim" <spam@xxxxxxxx> wrote in message
news:rBN7k.62343$Nn.14877@xxxxxxxxxxxxxxxx
Have any designs for widely variable switch mode power supplies suitable
for use as bench power supplies been published? I've been looking at
some
comercially available supplies but they're still way too pricey. Ideally
I'd like a supply that does 0-100V at 20A or 2KW with a constant current
mode. Going right down to 0V isn't essential and a maximum of 60V and
1KW
would still be great.

Scrim

By the time you get involved in designing at the 2KW power level, you
should have enough sense to realize that it's a lot easier, and makes
more sense, to address the specific requirement. At that power level,
the power supply itself is a major portion of the design.

There's nothing to stop you hacking into the control circuitry of
fixed-output designs, to produce output variations that are either
voltage or current regulated. You will discover the limitations of the
devices involved, when you do.

These limitations are sometimes addressed commercially through
modularization - where for a specific application, modules with
varying characteristics are selected and applied in series or
parallel. For example, flyback converters give good voltage range
compliance, forward converters give good current range control and
linear variations can provide noise-critical performance.

Switchers are generally not good at regulating around zero voltage or
zero current, unless they are configured for bipolar output
voltage/current or can dissipate/store returned load energy.

RL

Thanks for that. I'm really after a variable supply though for general lab
use where I need from milliamps to tens of amps. Usually an amp or two
suffices but recently I wanted to test several Peltier devices and needed a
supply of unknown high current capability at between 8 and 28 volts. Mainly
I was wondering if any of the hobby magazines had published a switch mode
bench supply design.

Scrim


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