Hello everyone,

I design a simple flyback converter and assemby in PCB. My transformer etd29, primary indutance around 400uH and 40Turn, secondary is 9Turn. But when I drive UC3845 around 10V y applying external voltage from power supply not from line. There is some oscillaiton in PWM signal, as you can see in my attachment. Can any body commet this issue?

 

Post the schematic.

 

Post your pcb works too please..

 

Post your pcb works too please..

I can, but it will help ??

 

Yes cos sometimes the circuit diagram doesn't match the pcb works!!