driving a mosfet

[rednwhite]

looking to drive a mosfet at 50-100KHz with a duty cycle of 0.350 which will need to vary, any ideas how to do this.

I have thought about a 555 but can it be done/should it be done with a PIC, completely new to PICs

Any other Ideas

Ted

 

[indulis]

Yes, you can do it with a 555 but the frequency will vary as you change the voltage on the "control pin" or you could use a "PWM" IC. A PIC will work as well.

 

[rednwhite]

any ideas on which PWM ICs? or which PIC to use, and where to get any ideas for the code? also I would prefer to go down the PIC route as I need a PIC for other parts of the circuit so should I use assembler code or high level language?

 

[MikeMl]

At that frequency, a 555 is ok to create the pulse train, but not to drive the gate of a large MOSFET directly without an intervening gate driver... You will need a high-current gate driver if the pulse train comes out of a PIC, too...

 

[rednwhite]

Yeah, I was thinking of using a UC1706 as the gate drive circuit?

 

[shortbus=]

Here is a simple PWM generator; RMCybernetics - DIY Homemade Power Pulse Controller

Substitute your mosfet for the one in the schematic.

 

[MikeMl]

Here is a simple PWM generator; RMCybernetics - DIY Homemade Power Pulse Controller[/url]

Substitute your mosfet for the one in the schematic.

This is a very poor excuse for a high-frequency PWM MOSFET controller. The gate drive is much too whimpy to minimize dissipation in the FET (gate current sourced by 2.2K resistor, sunk by a very slow opamp) . Witness the large heat sink that the FET is mounted on. Very naive design.

 

[peufeu]

This is a very poor excuse for a high-frequency PWM MOSFET controller. The gate drive is much too whimpy to minimize dissipation in the FET (gate current sourced by 2.2K resistor, sunk by a very slow opamp) . Witness the large heat sink that the FET is mounted on. Very naive design.

Yeah definitely. You can get good low-side MOSFET drivers at $0.60 from digikey, look in the appropriate category. No excuse !
You can generate the PWM with the PWM peripheral in your microcontroller, and feed that to a proper driver.
UC1706 looks fine.

 

[shortbus=]

This is a very poor excuse for a high-frequency PWM MOSFET controller. The gate drive is much too whimpy to minimize dissipation in the FET (gate current sourced by 2.2K resistor, sunk by a very slow opamp) . Witness the large heat sink that the FET is mounted on. Very naive design.

Yes, but, the circuit can be used to drive the UC1706 driver or another driver chip. The circuit I referenced is a good simple PWM circuit.