I am considering to use a center-tapped 12-0-12 (A-C-B) transformer for getting 12V and 24V simultaneously.

I tried to use one bridge across A and C to get 12V, and another across A and B to get 24V. But when the two negatives are connected, both outputs become 24V.

Any help shall be appreciated.

 

I assume that you want positive voltages, but this method will work to get ±12 and ±24 VDC.

You can ground one end of the winding, then use the center tap to drive a rectifier for your 12 volt output, then rectify the end of the winding to get 24 volts.

This only gives you half-wave rectification so you will need a larger capacitor for a given amount of ripple at a given load, and you won't be able to get as much current out of the transformer as with full wave rectification.

http://postimg.org/image/l28psk007/

You probably don't want all the outputs, so just leave off the diode and capacitor for each output you won't want.

 

Thanks for your response.

How about this circuit in terms of current drawing from the transformer?

 

I am not familiar with this arrangement, but it appears to be a fully wave voltage doubler. It will still subject the transformer to a high peak/average current and it might be better than the half wave rectifiers. In other words, I don't know. How about simulating the two configurations with SPICE and comparing them? That's one thing that SPICE is pretty good at doing.

 

Regarde...

 

I am not familiar with this arrangement, but it appears to be a fully wave voltage doubler. It will still subject the transformer to a high peak/average current and it might be better than the half wave rectifiers. In other words, I don't know. How about simulating the two configurations with SPICE and comparing them? That's one thing that SPICE is pretty good at doing.

With LTSpice, your configuration gives 12V and 24V whereas, my configuration gives 12V and 33V. With Falstad's java simulator both gives 12V and 24.

#12's last circuit almost similar to mine. seems to be better.

 

Regarde...

Thank you.

 

#12's last circuit almost similar to mine. seems to be better.

It's a matter of slowly stepping through the additions to be sure you got the grounds right.

I got some sort of brain failure looking at your circuit so I just backed up to basics.

 

Hi abuhafuss,

You do realize that if you half-wave rectify 12 vac for example and add a filter capacitor you will get roughly the peak AC voltage out minus the diode drop, (and ripple), correct ?

 

Hi abuhafuss,

You do realize that if you half-wave rectify 12 vac for example and add a filter capacitor you will get roughly the peak AC voltage out minus the diode drop, (and ripple), correct ?

Yes, I am getting 11.45V and 22.90V.