Predictive Current Control in Active Power Factor Correction Controller

Abstract

The half-bridge (HB) LLC resonant converter is widely used
in high and medium power applications, because of several
advantages such as zero-voltage-switching (ZVS) capability
over a wide input range and low component count. Most LLC
resonant converters employ frequency modulation scheme to
regulate the output power. However, in wide input voltage
applications with widely varying hold-up time requirement,
large switching losses are incurred during low power
applications, which results in a low overall efficiency. A
variable magnetizing inductance has been proposed for
certain applications. However, this is not easy to implement
as the relationship is not linear. This paper proposes a high
efficiency, high power density half-bridge LLC resonant
converter at low power application. High efficiency is reached
at all power levels by introducing an operating mode: Lowpower mode. Here, the output power is regulated by adjusting
the voltage across the primary resonant capacitor. This
provides for accurate mode control and linear power control.
This method provides flexibility and ease of design for
applications with largely varying power level requirement.