LM5116 buck converter not working when output connected to 12 volt source

[smijesh]

Hi all
I have noticed an issue in my Buck converter, converter not turning on when output of the buck converter connected to a 12V DC source.
Vin 50V,
Vout 13V
I Out 10A
IC LM5116
By trail and error methode i fixed this issue by changing series gate resistance to 0E, it was 33E.
What could be the reason
similar schematic attached

 

[smijesh]

I have few observations during the tests
1) No load output voltage observed is 11VDC actual designed value is 13VDC, getting 13VDC only when light load connected
2) 13VDC output getting when below 4VDC applied to the output of Buck converter (controller not turning on when 12VDC applied on output)
3) Getting 13VDC with delay of 4-5 seconds when 1E gate series resistor connected and 12VDC applied to the output

 

[Easy peasy]

as we can't see your build - it makes it difficult to comment on how the layout and perhaps lack of de-coupling is creating RF that is affecting your control - also we don't know your exact control loop values - or if you are using the diode emulation mode - so you see - to many unknowns to make accurate comment ....