tl431 feedback
here's my design, I got some problems.....
My topology is full bridge phase shift
Vin=48-96V, N1/N2=5:26, Vo=200V,
When I boost my input to about 36V, the feebback path starts work. But the circuit become odd. The Vo can keep 200V but this is a on off control, which means phase shift on off alternatively. When I boost the Vin further to about 40V, the feedback is no problem (phase shift is fixed).
Also, when R6=1k, it become on off, which is PWM on off and fails to boost Vin further.....
My guess is that the problem of ramp signal or R6......
One more, if I don't add C2, the control can't work......is this value proper?