quickie +24v and +48v supply from one dual-secondary TX

I think C1 and C2 should be larger values... I'd say 100uF as a minimum.

regards, Jack

C1 C2 do not make it a voltage doubler. I think you are thinking of plans where that winding is center-tapped or grounded in some way.

Transformer voltage not specified.

Assuming 24VAC each winding, C5 charges to 35VDC, 200 ohms dropping to 24V Zener gives 55ma max in the +24V output. Zener watts (at no load) is 24V*55mA 1.32 Watts, an awkward value. Maximum load current is 55mA.

Now for +48V, just do the same thing: build a +24V supply. But don't ground the negative rail: connect it to the first supply's +24V point.

There is another way to do it that will give ~20% better iron utilization (not an issue at this power level) and saves four rectifiers, or saves 6 rectifiers with somewhat worse iron utilization, but requires thinking upside down.

How about a single transformer to make the two voltages like this:



regards, Jack

[quote author="buttachunk"]are c1 and c2 neccessary in this configuration if you use a second winding ? if so, they can be 35v caps since they are not doubling voltage, right ?[/quote]
If you have two secondaries on the transformer then you do not need C1 and C2. All the filter caps need to be 50v or higher... preferably 63v or 100v.

regards, Jack

I don't see that working, even the revised version. The only reference to ground is 'backwards' through the bridge for the 24V supply. Unless I'm misreading it, that's not going to work. Bad ju-ju, daddy.

If you look at what has become known as the 9K PSU (It's not an SSL design BTW,- it's one that I came up with for the 9K project... I know that a few people are under the impression that it might be SSL copyright, but no!) and just build the +18V half of the ±18V supply (scaling it up accordingly), and build the +48V part, you've got what you need.

You have to start with a current path to/from (depending on your current philosophy... let's not get into the religion aspects here! :wink: ) ground AT THE SOURCE. Otherwise, it's like connecting a light bulb to a battery with one wire... you need two for the bulb to light up.

In the second version, the voltage won't ever build up sufficiently, because there's not enough peak potential at the windings. If you have a 30V peak potential, the bridge diodes won't ever forward charge to more than 29-point-something volts.

Looking at the second version, you have to ground the center tap of the secondary and LOSE the ground connection at the negative end of the bridge. Then if the transformer is something like 22-0-22V, you're in business.

Keith

multistage charge pump..

:thumb:

There's a 24/48V PSU in this thread: http://www.groupdiy.com/index.php?topic=6372

I don't know if anybody has built that one, but it looks like it should work.