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how can protect mosfet switch in flyback as switch

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how can protect mosfet switch in flyback as switch (wit uc3842)

Hello
here is my circuit for my fly back smps.
1302778300_1371891717.jpg

but after i start my circuit the (10k ohm resistor) and my mosfet getting so hot(mosfet is worse than resistor).i connected a parallel diode (By150) with DS of mosfet (such as mosfet intersenic diode) but it burn as my circuit has been started.
now how can i protect my mosfet more better than above circuit?
 

You say it's a SMPS, where's the power output? As shown all energy stored in the inductor will be burned in the RCD snubber and switch transistor.
 

Thanks FVM for your response.
yes it is a simple smps but i didn't draw the other part of schematic, i have only problem in this part of circuit
freq:70 khz
input voltage 320 volt dc
output :24volt dc
 

yes it is a simple smps but i didn't draw the other part of schematic, i have only problem in this part of circuit
Click to expand...
The problem is most likely transformer leakage inductance, in so far I don't agree with the statement. What's the transformer windings ratio, did you measure leakage inductance?
 

Drawing only part of a schematic always leaves questions. Please show the rest of the circuit.

What is the voltage at U1, pin 7, the Vcc voltage?

Such a large snubber capacitor for C2 will tend to absorb much of the energy in L1 which is not desirable.

Is the rest of the circuit operating normally? Is the output voltage regulated?
 

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