High power density and power factor cascade buck-boost PFC converter under high line input voltage

Abstract

In this paper, a control technique to achieve high power density and power factor (PF) under expanded high line input voltage using a cascade buck-boost PFC converter is proposed. Recently, the requirement of a $277 V_{AC}$ rather than a $230 V_{AC}$ has been increased in an AC distribution structures. The link voltage of conventional boost PFC converter is increased to 450 V under a $277 V_{AC}$ compared to the link voltage (400 V) under a $230 V_{AC}$ . Therefore, the volume of the link capacitor is also increased compared to the volume of a conventional link capacitor, which reduces the power density of the PFC stage. Moreover, the conventional boost PFC converter has a poor PF at the light load conditions due to the phase leading input current caused by the input capacitor. To overcome these problems, this paper proposes control techniques using a cascade buck-boost PFC converter in order to achieve a lower link voltage (400 V) under a voltage range of $180~305 V_{AC}$ . Therefore, a proposed technique uses a smaller link capacitor and achieves a high power density. Also, with a proper control of an additional switch $(Q_1)$, the phase leading input current can be relieved. Proposed techniques are explained and performance of the proposed technique is verified by prototype with 800 W conventional(450 V, 1.78 A)and proposed (400 V, 2.00 A).