A study of power correction boost converter operating at CCM-DCM mode

A power factor correction boost converter operating in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is analyzed. In principle, CCM-DCM mode is a special variable hysteresis control. It features the inductor current oscillated between a pure sinusoidal wave and zero. However, its design rules in engineering applications are similar to those of the constant on-time control. A theoretical approach is carried out to demonstrate that there exists a correspondence between the two different control modes, and conditions for using these simplified equations are presented. In actual implementation of the CCM-DCM mode, filter capacitors are necessary to obtain a clean sinusoidal current reference. On the other hand, the capacitor will bring a DC component in the reference signal, affecting the switching characteristics, rms currents, losses of the power components, and the power factor of the converter. A CCM-DCM mode with consideration of the DC component is analyzed, and the design equations with the new mode are presented. The analytical results for a 40 W boost converter, including the effects of the DC component and the selection considerations of the filter capacitor, are discussed