Linear PFC regulator for LED lighting with the multilevel current bypass circuit

This paper proposes a linear PFC regulator for LED lighting applications. The proposed circuit is small in size because the circuit structure consists of only semiconductors, ICs, and small resistors without any reactors and electrolytic capacitors. The current bypass circuit which is connected in parallel to the LED string consists of one MOSFET, two Zener diodes, and one resistor. The MOSFET is operated in an active state by a self-bias circuit. Thus, an external controller and high voltage gate drivers are not required. The proposed circuit is experimentally validated using 7.8W 5-string and 15W 10-string prototypes. From the experimental results with the 10-string prototype, the total harmonic distortion of the input current is 5.1%, and the power factor is 0.999. In addition, the power loss is analyzed at an efficiency of 91.6% for the prototype circuit.