Re: Synchronous rectifier


supermos@xxxxxxxxx wrote:
Thank you for your reply!

I have said that the comparator is a zero-crossing detector. So it is
used to compare Vds with zero, but in fact there are some offset
voltage in the input of the comparator. Thus the comparator point is
actually +/- several mili volts. If the comparator point is positive
several milivolts, there will be a large delay when turning off the
MOSFET; a negative several milivolts will cause oscillation under
light/zero load. Now you may understand it is very hard to have a
hysteresis for such a comparator and in fact a hyteresis here is of no
use.

This is for a VRM.

this article has some ideas
http://www.edn.com/article/CA216166.html

.

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