PWM signal from SG3525

[kriitish]

Hello Friends,
I am designing a Full Bridge SMPS with IGBT, SG3525 and IR2112. While it is working the output PWM signal goes to zero immediately after sometime when seen through oscilloscope. The input pin have 2.5V(IN+) and I set to 1.5V using POT(IN-) connected to the pin 16(5.1V). When I switch ON all the supply, the PWM is present for sometime and immediately goes to zero. I don't know what is happening and I couldn't find any solution from internet.

Please anyone clear my doubt.

Regards,
BALAKRISHNAN Naveen Krishnan

 

[KX36]

schematic?

 

[sivankls]

at a glance seems to be instability, increase reference at Non inv input around 2.5 Volts then bring the Inv pin to the same, the feedback will be then in loop.pls post the schematic here..