SMPS with multiple output

Thread Starter


Joined Oct 17, 2006
Hi guys,

I am trying to design a SMPS with the following outputs:

I can not figure out what is the best topology I could use for this power supply. Does the Half Bridge topology work for this type of power supply. Please help or guide me to the best web site, which I could found some sample circuits. Thank you very much for your help.



Joined Jun 30, 2006
You'd probably need a custom solution for that. It's a hell of a lot of power.

You could build five independant powersupplies.

Input range would be 10-25 volts, not sure of current requirements, this can be raw from a transformer of suitable rating.

5V 15A

8V 5A

15V 3A

-15V 3A
not sure

18V 1A


Joined Oct 14, 2005
I assume it is an off-line switcher? If so, then either flyback/forward or half bridge topologies are suitable, although with higher power half-bridge does have advantages of distributing the load to two switches instead of one. However, the cost would be higher and the transformer design is more elaborate.

I would probably go with flyback, just to keep things simple.

If you want to see some example circuits of off-line switchers, I found that the onsemi site is quite excellent. There are many application notes and design examples on their AC-DC offline controllers.

You'd probably also need a PFC for that.


Joined Jan 10, 2006
How about modifying an ATX or AT computer PSU by rewinding all but the 5 volt windings on the Output transformer. Not sure which line the regulator ref is taken from (possibly the 12 volt) so modifying the divider to give the proper ref from the new 15 volt line would probably also be required.