A Low-Cost High Power Factor Battery Charger based on Standard Peak-Current Mode Integrated Controllers

Abstract

In recent years, several low-cost Power Factor Corrector (PFC) control techniques operating in Continuous Conduction Mode (CCM) have been proposed to simplify traditional control strategies based on a multiplier. This simplification makes sense in the case of relatively low-power, low-cost and wide input voltage range applications. These techniques revolve above the Boost converter as a first stage of a.c.-d.c. power supplies, because their application in other topologies is more expensive and complex. In some applications, however, a PFC can be used as a one-stage power supply. This paper presents a new low-cost control strategy suitable for the Flyback family of PFCs (e.g., Buck-Boost, Flyback, SEPIC, Cuk and ZETA). Control is carried out by a standard Peak Current-Mode Integrated Controller (PCMIC) for d.c.-d.c. converters. Neither an analog multiplier nor an input voltage sensor is needed to achieve quasi-sinusoidal line waveforms, which makes this method very attractive for low-cost applications. In fact, this method is the simplification of One Cycle Control (OCC), also called Linear Peak Current Mode Control (LPCMC), applied to the Flyback family of PFCs. In this case, the use of a simple exponential compensation ramp instead of linear ramp is the proposed solution for reducing the Total Harmonic Distortion (THD). Moreover, the line current is cycle-by-cycle controlled and therefore the input current feedback loop is extremely fast, thus allowing the use of this type of control with high frequency lines. Finally, an experimental prototype of a battery charger was developed as a high Power Factor (PF) power supply to verify the viability of the new control strategy.