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What is Reverse Transfer Capacitance?

I am designing a power supply using a standard buck topology with synchronous FETs.

I'm trying to minimize power in the drivers of the gate of the FETs, some of the datasheets say minimize the gate charge of the control fet. Some say to minimize the reverse transfer capacitance.

Can you just assume Q=CV and then figure out what the driver impedance is and estimate power lost through the equivalent output resistor in the gate driver? I'm sure it is more complicated than that, but can anyone provide some insight for me?

Thanks,

Jeff

Reply to
Jeff Mucha
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Short answer, google for Miller Capacitance or Miller Effect. Depending on circuit configuration, a FET's (or triode vacuum tube's) input capacitance may be multiplied many times.

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Reply to
Ben Bradley

Reverse transfer capacitance is the equivalent internal capacitance between the drain and gate. Current through this capacitance must be supplied by the driver circuit. It is equal to C dv/dt, where dv/dt is the rate of change of the drain voltage during switching. Since you want to make dv/dt as high as possible, to minimize switching losses, the required current throught the reverse transfer capacitance can be very large (Amperes!) It is often much larger than the current required to charge the gate capacitance. This is what makes driver circuit design so tricky.

Reply to
Jon

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