Hi
I want to build the high voltage smps with the output voltage at about 30KV and maximum current= 20mA with L6599
VCC(L6599_PIN 12)=15.3 volt , It supplied from one 15volt transformer.

I have a problem for driving high side mosfet(IRFP460 or IRF840) .

The gate resistor is 47 ohm , boot strap capacitor is about 100nF . The wave form of the low side mosfet's gate source is good (50% duty cycle and the clean square wave form- 15volts range) but the wave form of the high side mosfet's gate source is not good( 20% duty cycle, very noisy wave form- 10 volts range) . It makes the high side mosfet get too hot and burned after some minutes( even if it doesnt connect to the high voltage transformer ).

I attach the schematic of my circuit and the wave form of the high side mosfet's gate source.
http://www.4shared.com/rar/irjIdaA3ce/L6599_LLC.html

Please help me for improving high side mosfet's gate source

Regards
Hamed.