Bootstrapping a MOSFET

You can either buy a dedicated high side driver, which will include circuitry to generate a higher voltage source to drive your gate, or use a P-channel MOSFET - they cost more than their N-channel equivalents, but they do allow a simpler circuit.

Inventing your own high-side driver is a waste of time and ingenuity. You should have better things to do than re-inventing the wheel.

-- Bill Sloman, Nijmegen

You don't need much to drive the high side Mosfet, it takes very little = current, only the voltage level is more important. Remember Mosfet dies = so easily, I burned out over 35 of them already. They Suck big time!!

I have some experience with LM5035 half-bridge controller with active rectification. Controller has internal mosfet driver for both - high and low side MOSFET. Some additional features are also very nice. I used this for DC/DC converters up to 150W output power with maximum efficiency up to 96% for 3.3V output voltage. If you do not fixed already your controller, strongly recommend this one. Of course it depends for what kind of applications you are looking for. This one is dedicated for ATCA power supply, but it seams to be nice also for AC/DC solution as well.

Janusz

International rectifier do half bridge drivers, look on their website

Have you considered using fets that do not require voltages beyond what you have now for the gate?

In any case, there exist gate driver IC's for doing this how ever, you may want to research this a bit because the charge pumped variety could dissipate before the desired cycle and thus cause wave deformations and heating in the fet. Using a inverter type driver would be the best bet. Be it one you make your self (simple buck boost) or a ready made unit.

The last time I did this I made a high freg mini onboard buck boost inductive unit via a dual op-amp with feed back compensation. it worked perfectly to generate the additional bias voltage I needed. if you have a spare ADC input on a uC and spare output, you could PWM a circuit to do the same thing. We did that with a PIC project where we needed some higher control voltages.

International rectifier do half bridge drivers, look on their website

Agreed, take a look at the IR2110. should solve most high side driver problems uder 600V.

Wow, the 2110 will work perfectly. Thank you all for your advice!