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Gate drive transformer drive with no bad resonance?

cupoftea

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Hi,
We all know that in say a Full Bridge SMPS, driven by gate drive transformers, “one” should best not effect sudden shutdown by simply suddenly stopping the gate drive pulse train….to do so would inflict severe resonance within the L’s and C’s of the gate drive transformer circuit, and potentially result in shoot through current. This resonance cannot be damped out, to do so would simply render the gate drive ineffective.

As such, what is needed is either a new type of Full Bridge controller, or additional extra circuitry..

What is needed, is a way of telling the controller that whatever the voltage that its error amplifier output is at, this must be reasonably slowly reduced to zero, so that gate drive duty cycle goes steadily to zero over some cycles, rather than straight to zero.

This may be done by switching a voltage onto the output divider, which is just above the demand voltage, and that has an RC time constant, such that it relatively smoothly raises it thus. It sounds like work for an opamp getting switched in as such. Easy to do , but you end up with a handful of components….are there any modules/chips out there that do this?
 

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