I want to convert (and isolate) a 9V, 12V or 15VAC (60Hz) power supply to a +/- 15VDC supply and I’m not sure what kind of transformer to use. The output current of each rail is <500ma. Needs to be PC mount.
I want to ask a couple of clarifying questions.
Are you looking for 3 different options? One for 9VAC, one for 12VAV and 1 for 15VAC that would each give an output that is a Positive and a Negative of the respective voltage in DC?
By PC mount are you looking for a Through hole or surface mount option that will go on a board?
Is the output current for each rail you have listed the output current available or the output current you need. If it is the output needed do you know the available current?
My overall design need is to convert a single voltage such as 15VDC supplied by something like:
1939-1251-ND (digikey PN)
to a +/- 15VDC to be (linearly) regulated down to +/-12VDC to power an audio circuit. My original thought was to just use a boost buck to get my -15VDC from the power supply, but unfortunately that supply connects its output ground to the safety ground on the IEC input jack and I’m getting an audio ground loop. So instead I thought I’d use an 15VAC supply and a center tap iso transformer to get +/-15VDC to regulate down.
The circuit requires about 350ma-400ma from each rail. The input current from the supply listed is 1.6A
Through hole is probably best.
Instead of using this wall supply could you just take the wall power to an AC/DC convertor that would put out a +15 / -15 like these.
Yes, and that may be the direction I go. The one problem with using AC in is extra certification requirements for international distribution. Using low V AC/DC makes certification much easier which is why I thought about going with the desktop supply. So I wanted to investigate both options. It seems there is little need for doing the low voltage to low voltage option in general, so I may be out of luck and have to go with your suggestion afterall. The other option is to use the desktop/wall supplies that have 2 prong, but then there is the AC side blade style problem. Still, I’m leaning more and more toward just biting the bullet with the AC certification requirement.
Another option might be a wall wart that puts out a + and - voltage such as PCM50UD08-ND. Comes with a cost though.
Yes, cost is prohibitive though. My other option is this:
which uses an input cord that can be international, but a little harder to find than the standard computer type IEC connector used in the 3 prong solution.
So I guess I’ll either go with that 2 prong AC input or just bite the bullet and go with the onboard AC to DC convertor and get the extra certification. Design wise, that last option is certainly the easiest.