In my SMPS board input is DC. When I am giving supply to SMPS board, upto 75V input, voltage at Vcc pin is zero and supply current is around 0.15 mA. At 80V, voltage at Vcc pin is 5.27V(mean) (max 5.6V) and supply current is 1.2mA but Vcc voltage is not building up. Further when I am increasing voltage more than turn on threshold supply current almost remains same around 1.2-1.3 mA and voltage at Vcc pin is remaining 5.27V(mean) (max 5.6V). Vcc is not building and IC is not turning on.
Questions
1) At start up at 80V, IC drawing 1mA current but Vcc is not building upto 14V. it remains at 5.27V means. What is the reason?
2) What will be the voltage profile at Vcc pin a) input voltage 80V - Input turn on threshold voltage( more that 80V)
Modification 1:
In above situation I have removed pull up resistor at COMP pin
Observations:
1) At 80V High voltage startup generator will start and upto 15V will build up at Vcc pin. Then high voltage generator will stops and Vcc voltage fall upto 5V (Vccrest) and again high voltage generator will start. Same process will repeat as we increase the supply voltage upto Turn on threshold input supply voltage.
2) At Turn on threshold voltage, IC will works like short circuit behavior similar to attached waveform. As we increase the voltage above to the Turn on threshold, IC works in short circuit behavior. But here SS pin voltage is not verified as 5V mention.
Please don't consider starting part in waveform. please refer below part
3) For very short time, Gate pulses coming, around 1V is generating at output
Questions
1) At above Turn threshold supply input voltage, why Vcc voltage is not staying above Vccoff(10V). It is discharging upto 5V as shown in above waveform.
