An Auxiliary Circuit with a Flexible LC Resonant Tank for High-Efficiency and Low-Cost Totem-pole Boost Bridgeless Power-Factor Correction Converter

This paper proposes an auxiliary circuit with a flexible
$LC$
resonant tank for a high-efficiency totem-pole bridgeless power factor correction (PFC) converter. The proposed auxiliary circuit enables a zero-voltage-switching operation of the totempole bridgeless PFC converter. To minimize power loss of the auxiliary circuit, the proposed auxiliary circuit controls a slope of an auxiliary inductor current by adjusting an auxiliary capacitor voltage level. When the main inductor current
$i_{LB}$
is over a designed level, the auxiliary capacitor voltage is controlled to be almost zero. The proposed circuit operates to reduce the conduction loss in the auxiliary circuit with a steep slope of the auxiliary inductor current
$i_{LAUX}$
. When
$i_{LB}$
is under the designed level, the proposed circuit increases the capacitor voltage level to reduce the slope of
$i_{LAUX}$
, resulting in relieving reverse recovery issues. A simple MOSFET control selects the operational mode of auxiliary circuits without any structural change. Moreover, design guidelines for a boundary condition of two operating modes and
$LC$
tank are presented based on the root-mean-square (RMS) current comparison, which optimizes efficiency. Finally, the effectiveness of the proposed converter is verified through experimental results with a 500 W prototype.