The Output Adjustable Flyback Converter

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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

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Content sourced from Zen Schematics

Circuit:Simon Oh