A new digital control strategy of boost PFC at high-line light-load condition

Abstract

The power factor correction (PFC) converter is commonly used in many applications nowadays. For high power applications, boost PFC converter operated in continuous conduction mode is usually employed. However, at high-line light-load condition, the converter operates in discontinuous conduction mode. This leads to erroneous input current sampling which results in low power factor (PF) and high total harmonic distortion (THD). Moreover, the effect of EMI filter capacitor causes the displacement between the input current and input voltage. This paper proposes a digital control method to improve PF and reduce THD by using the current sample correction algorithm, duty ratio feed forward for current controller and EMI filter capacitance current injection algorithm. The increase of PF and reduction of THD are demonstrated by experiments on a 400W boost PFC converter.