mosfet based ups and inverter circuit.

mosfet gate driver circuits using transistors

I tried low side N channel mosfet circuit and it works perfectly. I dont understand why the high side circuit doesnt work.

mc34063 + pmosfet

no one explained me that in simple terms

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As I said, you didn't even mention, that you planned a high side switch. You only did in another thread, as I was aware just today.

The secret of high-side N-MOSFET behaviour lays in the parameter Vgs,th (gate-source threshold voltage). To turn the MOSFET on, the threshold voltage must applied between gate and source. Assume it to be 3V, then node 3 can't approach node more than 3 V in your above test circuit. If you look at the respective data sheet, you'll find the on-state resistance (Rds,on) as a function of Vgs. If the treshold voltage is e.g. 3 V, Rds,on can be further reduced by raising Vgs to 10 or 12 V. Logic level FET's fully turn on with only 5V Vgs.

The problem with wizpic circuit is that the transistors dissipate lot of energy.

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I don't think so. The only permanent current is drawn by R1 - in off-state, when the bootstrap capacitor is reloaded. I think the circuit is fine, I once designed a similar driver for a SMPS lab demonstration circuit.

drive circuit for back to back mosfet

ok i got it. the voltage across the drain-source (across the mosfet) is applied to gate-source(Vgs). So it like applying 3v and not 12v.

so what is the solution to drive such systems. is it only bootstrapped driver..

what if the load is capacitive (or in a H bridge high side mosfet).

I have to use another H-bridge to charge the bootstrap capacitor. (use 2 transistor to charge and 2 to place it across gate-source)

I don't think so. The only permanent current is drawn by R1 - in off-state, when the bootstrap capacitor is reloaded. I think the circuit is fine, I once designed a similar driver for a SMPS lab demonstration circuit.

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I tried the 2 transistor ckt. There will be a point (in the input signal ie square wave) where both top and bottom transistor will conduct so it results in dissipation.

n mosfet driver

here it is