Switching power supply

Iam working on flyback with 200-500 volt input and 300 volt output with 100watts power out put iam using uc3842 ic, i designed transformer to assure itwont saturate when vlotage is above 400v everyrhing almost work fine ,but under this voltage (output voltage also under desire voltage) it has a strange drain waveform(double pulse to switch for turn on in a very short (1us)time in relative to working frequency (100khz)),i also try to fix compensating with ti aplication note, but no idea i will post images from my oscilloscope, what is problem? Thanks for reply

by Asr36928
March 20, 2021
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1 Answer

Answer by febb

You probably need to use or tune RC filter required to connect Isense resistor to Isense chip pin to prevent false spikes caused by switching MOSFET. It is described in UC3842 datasheet in details.

+1 vote
by febb
April 10, 2021
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