Buck-Type Current Unfolding Converter With Discontinuous Conduction Mode in Ultra-Low Power-Factor Operation

Inhalt:
This paper proposes a control method for a buck-type current unfolding converter, especially operating under non-unity power factor. The proposed method utilizes discontinuous conduction mode (DCM) to control the inductor current. DCM enables the converter to drastically reduce its inductors and allows the current controller to handle step changes in current due to non-unity power factor operations. Furthermore, this method enables the application of a feedforward-based control strategy by utilizing DCM, thereby eliminating the need for current sensors in the converter. Experimental results demonstrate sinusoidal output current waveforms at both unity and zero power factors, achieved without any current sensors in the converter prototype. These results confirm the effectiveness of the proposed method, particularly its robust current control capabilities. The proposed method is expected to increase the switching frequency and reduce the size of the passive components.