Re: What Driver Voltage to Drive a Mosfet? (SMPS app)

On Tue, 31 Jul 2007 00:07:53 +0100, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:



D from BC wrote:

My power mosfet has an absolute gate spec of 30VDC.
Most of the Mosfet data*** gate behavior graphs only go to 10V.

Is there a drive voltage that'll provide low switching loss?
Looks like there's a 6V to 30V range to choose from.

As others have said, the trick is to turn it on *FAST*. Age proportion of the
losses are during turn-on and turn-ff as opposed to conduction.

So... what you *should* be asking (given a sensible choice of voltage drive) is
gate CURRENT ! The more amps the better.

Graham

I'm picturing driving a mosfet like this..

+----Rsource---+
| |
| |
Vdriver Cgate
| |
| |
+--------------+

V is from the mosfet driver rail voltage.
Rsource is mostly internal mosfet driver resistance.

Here's my confusing thing...

Given that the mosfet driver can change state fast with currents up to
14A peak and the objective to fast charge/discharge the gate for low
Pds switching loss ...It kinda looks like one should make V (the
mosfet driver rail) as high as possible for the fastest charging.


D from BC
.

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