A dual mode control for bridgeless SEPIC power factor correction rectifier

This paper presents the design and development of a dual mode controlled bridgeless SEPIC unity power factor correction rectifier for a typical low power application like an LED driver. The proposed topology has reduced component count with reduced conduction losses because of no front end diode rectifier. The bridgeless SEPIC converter is designed to operate in discontinuous current mode so as to obtain a natural zero current turn off in output diode and zero current turn on in switches. This will reduce the complexity in control and provides voltage following capability for the source current. The proposed dual mode control circuit gives a supplementary control capability to attain sinusoidal current even in the presence of harmonics in source voltage. A harmonic detection is carried out on the source voltage and the control is directed according to the results either to voltage follower or average current control. The second control uses an extraction technique to get a sinusoidal current reference and maintains UPF even with the presence of harmonics in the source voltage. The proposed converter with its associated control is developed in MATLAB/Simulink for a power rating of 10W a practical rating of an LED load. Beside the normal operating conditions, the circuit is tested under varying source voltage, frequency and also with harmonic source voltage. The source current is found to be sinusoidal under all the conditions and the current THD is found to be well below 5% with unity power factor.