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The off-the-line primary side regulation flyback LED lamp driver is proposed based on LED forward voltage tracking (VFT) and duty variation tracking (DVT) methods, which satisfy good line/load regulation, high power factor and TRIAC dimming possibility. This paper introduces that four derivative types (TYPE-I to IV) are possible to implement using supply voltage, MOSFET drain voltage and duty cycle signal with the four types of sensing circuits on the basis of VFT and DVT concepts. The load regulations of TYPE-I to IV show 0.89%, 0.51%, 0.43% and 0.56% [A/V], respectively. TYPEI to IV show ±8%, ±2%, ±2% and ±4% of line regulation over 180 to 260 VAC variation, respectively. Each type satisfies above 81% of efficiency when it delivers 6 to 12 W to the LED load at 220 VAC. The power factors of all types are above 0.9. The chip is implemented using 0.35 μm BCD process and occupies 0.76 mm2 .
Date of Publication: Dec. 2012