Power Factor Correction, CCM, DCM, CRM/BCM Control, Bridgeless
Technical Lecture Session
Single-Phase AC-DC Converters
PFC, Constant on time control
This paper presents an innovative improvement of the Constant On-Time (COT) control of Transtion Mode PFC Boost converter, to improve the total harmonic distortion (THD) of the input current at medium/light load. It is a well-known fact that using a conventional COT control, the THD is increased with respect to a peak current-mode control due to the parasitic elements (e.g. Coss power switch capacitance) that causes a negative offset in the inductor current shape. An existing Enhanced COT control (ECOT) improves the THD, extending the power switch on-time TON to compensate for the negative contribution. As a drawback, this control algorithm produces a minimum level of manageable output power, Pout_min. If the Pout_min is higher than the power required by the load, the converter to keep the output voltage regulation stops the operation for some time (aka burst-mode), significantly increasing the THD. The proposed improvement of the existing ECOT control method aims to overcome this issue.