The Output Adjustable Flyback Converter

A high voltage step-up DC power supply using adjustable flyback conversion.

Vin = 220Vac +-10% @ 50/60Hz
Vout =0~600Vdc @ 0.25A
Switching Frequency: 70~100KHz

Design Guidelines:
DCM mode, output power is 200W

The input RMS current in worse condition with discontinuous current mode may be calculated as:

If the optimum operating duty cycle is set at D=0.35, then input peak current can be found as:

Therefore the voltage sensing limit voltage level from the FAN7554 data sheet is 1.5V