Driving Power MOSFETs with a 5V Trigger

[GlenS]

Hi,

I'm new here and not sure if this is the appropriate forum for my question. I'm trying to drive a power MOSFET (2SK3746) but I'm having trouble getting it to switch 'on' consistently because my trigger is a 5V trigger from a BJT and the drain voltage is 1300V above source. To fix this I need to switch a (separate) 20V power supply to the gate of the power MOSFET using the 5V input. I know that if I try to switch the rail by adding another MOSFET in a source-follower I will get a voltage which is the drain current, id, of the switching MOSFET times the output resistance RL, which will be almost-but-not-quite my 5V input voltage.

Can anyone suggest a way I can (quickly, i.e. ns) use the 5V trigger to switch a 20V rail? Or even where I might look for such a circuit?

Thanks

 

[marcusl]

So you have a p-channel MOSFET sitting at +1300V and you need to pull its gate from +1300 to +1295 to turn it on?

 

[GlenS]

No, I have an N-channel, enhancement mode power MOSFET with drain at 1300V, gate at 0V and source at 0V. I need to drive the gate to 20 V (above source) as fast as possible to switch the drain to 0V. It's for a Marx bank.

 

[marcusl]

You want a power Mosfet driver. Most operate only to 10V, but some higher voltage devices are available. See, e.g.,
http://www.onsemi.com/pub_link/Collateral/NCP5111-D.PDF
where you would use only the low side drive.

I'm sure there are other vendors, too.

 

[GlenS]

Perfect, thanks very much.

 

[famousken]

You can also use a gate drive transformer. this will be of benefit in a marx circuit because you only need one driver for the transformer and the individual windings take care of both isolating each section and you do not have to worry about bootstrapping mosfet drivers.