Electronics > Beginners
LAB POWER SUPPLY
MarkF:
Multiple transformers:
Alternately, you could use a half-wave bridge rectify.
However with the same value capacitors, the output current would be less
because of the increased ripple.
glinjik:
Thank you that looks good the transformers put 19v to for the 12v so 7v to play with the 19v I want could be on a single transformer that just leaves the smps to be modded to supply neg ? Any ideas?
rdl:
Just build two separate 12 volt supplies. It gives you the most options.
rstofer:
Totally separate supplies creates an issue with switching. Can the project accept one rail going high before the others by some relatively long period of time. It's pretty clear the FPGAs don't tolerate this kind of thing because they invented power management chips for this very reason.
I would want the isolation that is provided by a transformer design. In my view, transformerless is out of the question.
When you pick a preregulation DC voltage, consider the implications on the lower voltage regulators. The preregulated voltage for a 19V supply is probably close to 24V, maybe as little as 22V. Then think about the poor 3.3V regulator dropping 19V at 1A => 19 Watts. Can the regulator handle it? This is a bigger problem with 30V supplies but still worth thinking about.
That's why commercial supplies have transformers with multiple output taps.
For Op Amps, I would definitely prefer +-15V over +-12V because the older op amps just can't get within 3V of the rail and the signal swings are usually +-10V. Many of the older analog computers use +-10V for their signal swing and +-15V for the rails. The Comdyna GP-6 is an example:
https://oldcomputermuseum.com/comdyna_gp6.html
glinjik:
So the way im thinking 1 transformer 12v+-, 1 transformer 19v+ and the smps 0-6v all separated on their own boards with their own output terminals no common ground except 240v
the first step is to get this smps adjustable to 1 volt or so fist gonna upgrade the caps there only 10v so im thinking 16v caps and double the resistance of the pot
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