Power Factor Correction in LED lighting using CUK converter

  CUK converter operation in PFC 

The system detail consist of rectifier diode D1,D2,D3 & D4 which provide the dc input to the cuk converter, C_F is the filter capacitor which smoothen the DC output of the rectifier & reduces the ripple in the voltage. The cuk converter consist of primary inductor L₁, MOSFET Switch S₁, fly-back capacitor Cc, Diode D_S, Secondary inductor L₂, output capacitor C_o & this converter is driving 27W LED. The each component of cuck converter works as follow

1.       When S₁ is turned ON, the inductor L₁ start charging & in starting phase it opposes the flow of current, it act as the high resistance component but after sometimes, its impendence decreases & current I_L1 starts rising.

2.      Now the S₁ is turned off, due to sudden drop in current the polarity of the L₁ reverses, it induces the flyback voltage V_L1, the voltage in inductor is in same direction as of source, therefore added voltage, the flyback capacitor C_C act as a short circuit because of decreasing current from the L₁ & D_S become forward bias & It completes its circuit.

3.      Now S₁ is turned on again, the C_C already charge, therefore it start discharging through S₁ & it provides the power to the load. Simultaneously L₂ stores the energy, provided by the C_C.

Now the S₁ is turned off again, as the L₁ is already charged which tries to charge the C_C again though the D_S. Inductor L₂ is also already charged, its polarity reverses & it also provides the power to the load through the D_S.