9VAC to +/- 15VDC - schematic, will this work?

[burningman]

I have tested this and it seems to work. Does anyone see any drawbacks/issues?
thanks, BM.

[zyxwyvu]

It looks fine to me, except you seem to have switched the In and Ground pins on the 7915.

[Thomeeque]

It looks fine to me, except you seem to have switched the In and Ground pins on the 7915.

Circuit is OK, symbol is wrong.. 79xx pinout is 1-COMMON, 2-IN, 3-OUT

[burningman]

Thanks for noticing that, I forgot to change the pinout. Can anyone identify any deficiencies in the circuit?

[JDoyle]

9V ac keeping a 15V voltage regulator above it's drop out voltage is a bit of a stretch, in my opinion.

[amptramp]

Each side is a half-wave voltage doubler.  You have 18 volts on each side driving the 15-volt regulator on each side.  Open circuit, the output will be 2.82 x the AC RMS voltage on each side or 25.38 volts to operate a 15 volt regulator.  I like this design!

[Taylor]

What sort of diodes would be used here? Would 1n4001 work?

I'm not too familiar with this kind of circuit, but is it possible to use the same 9v supply to feed this as I'm using for other (9v) circuits, simultaneously? Does it load down the supply or otherwise interfere with 9v effects connected to it?

[ryanuk]

Hi

Noticed this thread but the images are gone - anyone still have the schem for this power supply??

[sbm]

+1 Been looking for this as well.

[burningman]

I haven't had time to redraw my diagram - it's pretty sloppy.

Here's what I did:
I used one of the terminals from the 9VAC adapter as a single node for connecting together two doubling circuits (positive and negative). I used the second terminal from the 9VAC adapter as a common ground for both the positive and the negative rails.

The doubling circuit is conventional. You can find it in just about any academic textbook that talks about power supplies and voltage multipliers. The following is a great online source that explains the doubling action clearly:
http://www.play-hookey.com/ac_theory/ps_v_multipliers.html

The negative side of the doubler in my circuit is different from the positive in that the polarity of the capacitors and diodes is reversed in relation to ground. This makes sense when you consider that you are building a dual rail supply that is providing both positive an negative output, above and below the 0V ground potential.

Ignoring component values and extra smoothing on the input of the regulators, the power supply in the following link shows the polarity that I am using. http://www.clarkhuckaby.com/Images2/MxmFig06.GIF

I would highly recommend reading "Power Supply Projects" by RA Penfold. He provides a good run down of how to chose components values and why they are there in the first place.

A word of warning: Polarity counts with electrolytic caps - be careful. I would start off by reading about supplies in the links above, move on to testing a positive voltage doubler, and if you feel confident, move on to the dual rail supply. Just my two cents.

[Tonemonger]

I would highly recommend ALL of RA Penfolds books !