Half Bridge vs Full Bridge

Mar 01, 2006 2 Replies
T

Hello,



I am somewhat new at smps. I am designing a simple circuit to amplify a square wave 400hz signal to 340Vpp signal. Am I correct to assume that a half bridge drive circuit is for single rail only (ie positive swing) and that what i should use is a full bridge driving 4 MOSFETs?



Also I breadboarded a half-bridge circuit driving 2 MOSFETs. The rail voltage is rectified line from a variac so that i can ramp it up slowly. The output signal looks good until I reach about 80V. The the signal appears to saturate and its amplitude stays at about 60V and will not increase even with increasing rail voltage.



Thanks in advance.



Paul


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W

Obviously you're doing something wrong, but with so little detail in your post we can't give much useful advice.

Thanks, - Win
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C

A half bridge only fluxes the transformer in 1 direction and so uses less than it could. Your problem is probably that your bridge capacitors are not big enough and it would most likely to be cheaper to use a full bridge which drives the transformer in both directions than get large capacitors.

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