Most of UPS use so many op amps to have square wave converting sawtooth triangular, etc .......
why they use op amp for that producing simple square wave??

 

One more ques. at post #1 , the transistor at transformer the base of transistor are shorted directly. Will this not cause any problem at high freq.??
can't we use V be multipliers there.....??

 

One more ques. at post #1 , the transistor at transformer the base of transistor are shorted directly. Will this not cause any problem at high freq.??
can't we use V be multipliers there.....??

Care to show a schematic? I didn't understand what you were trying to say.

A class D will use a much higher frequency to modulate a 50 or 60 Hz sine wave. The important thing to understand however, the modulating frequency doesn't need to go throw the transformer, at that point only the 50/60 Hz matters.