It stands to reason you can only regulate one output! If you examine commercial SMPS they normally use one of two solutions:

Rely on the ratio of the secondary windings and regulate only one critical rail

Or

Have the other secondaries of a larger voltage and use linear regs for regulation.


So, use one of the above tdchniques or use three separate psus.


That didn't take much thinking did it?

Also, where does an 8051 enter this discussion? Methinks this should reside on the Char board.