The Output Adjustable
Flyback Converter
Circuit :  Simon Oh
Email  :  Simon@SoftSwitching.com


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

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

fig 1


Design Guidelines
DCM mode, output power is 200W

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

eqn1


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

eqn2


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



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