With that range of output voltages you may be able to buy one -- many
'fixed' output supplies will allow some adjustment, you may be able to
find a 15V supply that'll squeak down to 11, or a 12V supply that'll go
over that range.
--
Tim Wescott
Wescott Design Serviceshttp://
www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it
says.
See details athttp://
www.wescottdesign.com/actfes/actfes.html
I found something thats nice, but not AC/DC..its the National LM25576
buck regulator which I can just put an off the shelf 24V supply in
front of, and its meant to be adjustable in my voltage output range,
and they have the online webbench which built the entire circuit for
me and i bought an unassembled kit from!
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I would suggest looking at some of the Linear Technology parts, and using
their "jigs", which are reference circuits for each of their switching
regulators or other parts. Examine the waveforms carefully, both during
startup and after the output becomes stable. Play with inductor values,
frequencies, and various combinations of input voltages and output loads.
Then, when you have a better understanding, you can order some parts and
actually build a circuit. You can make it work on a perfboard, especially
if the frequency is 50 kHz or less, but a real PCB is better, and layout is
all-important and non-trivial. You need to understand how a couple inches
of copper can act as a significant resistance and inductance that can cause
instability and inefficient operation. There are tradeoffs regarding MOSFET
size and RdsOn and gate charge and switching losses due to the gate driver.
I have learned a lot with my recent design of a 12 VDC to 50 VDC at 40 watt
switcher, and my latest batch of PC boards still have some problems that
are caused by a combination of suboptimal layout, thinner tracks than
specified, and inefficiency caused by inadequate gate drive that did not
show up in the simulation. I added a hefty gate driver and boosted the
efficiency from about 75% to near 90%. The simulation showed about 93% or
better.
Your project requires working with AC mains voltages, which can be
dangerous not only in terms of shock, but also because of the amount of
power that can be supplied to an overloaded component, which can cause an
explosion that could put out an eye or cause other bodily harm. Wear
goggles and use a low current circuit breaker or fuse to limit the power.
Enclose the higher power circuitry in some sort of enclosure.
If you go with a front-end supply of 24 VDC, you will be a lot safer than
working directly on the mains. You can get a wall-wart computer supply very
cheaply, and then build the rest of the design as you need.
Good luck,
Paul
