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MOSFET h-bridge


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#1 robotjosh

robotjosh

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Posted 31 January 2006 - 04:54 AM

Hello all,

I am a student and trying to design a medium power h-bridge, and this question has me stumped.

If using synchronous rectification, how do the recirculation FETs conduct? The attached image shows how synchronous rectification is done in an h-bridge. The problem is, 3-lead FETs are designed to conduct positive current drain-to-source only. But during the off PWM cycle, when current is recirculating through the motor, one FET is always conducting source-to-drain. Is this possible? It seems to be a common way to brake a motor, turning both high or low side FETs on. When turned on, can FETs actually conduct positive current source-to-drain though the FET element and not the body diode?

Thanks in advance,

Josh

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