Hi sir , I m working with ucc28070 interleaved pfc ic with following specification
1) pwm frequency ----- 75Khz
2)out put power ------- 2500W
3)efficiency ----------- 95%
4)input voltage range ---- 180V-265V
As per TI application note SLUA479B i did the calculation i found i required an Duty cycle of 0.3637 . As per the formula i put all parameter its giving me negative value kindly suggest on the same issue.
Also i did the calculations for 0.75 % duty cycle and 75 KHz frequency and 2500W output power and kept frequency dithering disable by connecting pin 1 to V ref (6 V) and pin 2 to GND and first do the DC testing , as i get and 75 KHz PWM waveform @ MOSFET Gate to Source , by giving an 0.75 V VSense( pin no 4) and Vin AC(pin no 5)less than 0.75 .
When i start with actual ckt as my out put voltage feedback goes above 0.75 as per the IC Specification my PFC should be Enable but its didn't happen. My SS (pin 17) gets on and off .
kindly suggest on same issue also.
