A High Power Factor LED Constant Current Drive Method with Variable On - time Control

With the gradual improvement of LED lighting industry standards, power factor requirements for LED light sources was put forward. Input current is required to follow input voltage changes to reduce harmonic pollution to the power grid. In this paper, a high power factor LED constant current drive method with variable on-time control is proposed. On the basis of the traditional constant on-time control drive mode, the PWM wave generation mode of the drive signal is changed by adding a time calculation unit and a multiplier unit. The original drive signal is obtained by comparing the output signal of the error amplifier with the sawtooth wave. In the drive mode proposed in the paper, the output signal of the error amplifier is multiplied by the function of the on-time and off-time, and then the drive signal is generated by the comparator. So, the power factor is equal to 1 theoretically. Finally, the proposed new drive control mode is verified in the simulation platform.