MOSFET switching Gate Drive Voltage less than Load Voltage

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Hi,

Can a mosfet be drived with a 10-12V gate pulses while it is
switching only 7.2V or less. What effect will this have on the driver
circuity. BTW the power supply for the control IC is different from the
load supply.
Control IC: TL494 (Mode-0)
MOSFET: IRF540

Please advise. Thanks

kishore.

 

[Fritz Schlunder]

Hi,

Can a mosfet be drived with a 10-12V gate pulses while it is
switching only 7.2V or less.

You betcha.

What effect will this have on the driver
circuity.

Very little. The low drain voltage during switching will result in reduced
impact due to the miller capacitance. As a consequence the effective gate
charge that must be supplied/sunk by the gate driver during switching
transitions will be slightly less than if you were switching a higher
voltage. This is normally considered benficial since it means you will need
a slightly wimpier gate driver circuit for a given switching speed, but the
impact is fairly minimal.

 

[mook Johnson]

Just make sure your two supplies share a common ground at the source. If
they are isolated, you could use a gate drive transformer.

Also it your 7.2 volt signal has a high source impedance, you might pickup
swtching noise that jumps through the gate causing spikes in the switching
edges of the drain signal.