Power supply voltages

Thread Starter


Joined Oct 30, 2006
Can someone PLEASE explain how you get a positive voltage coming into a power supply and then how you get both a negative and a positive voltage coming out? ALL THE HELP WOULD BE COOL! THANKS


Joined Apr 20, 2004

I'm going to guess you're talking about a switched mode power supply. The positive DC voltage is used to drive current through the primary windings of a transformer. A solid sate device controls the current so it becomes, in effect, a high frequency AC drive.

The secondary of the transformer is electrically isolated from the primary side. Therefore, the output can be referenced to circuit ground such that it is producing voltage outputs that are true AC - they swing positive and negative with respect to circuit ground. Thus, you can produce positive and negative DC voltages by rectification.