A New Power Factor Improving Algorithm Under High-Line and Light-load Conditions

A new accurate computational method suitable for improving power factor of high-power AC-DC power supplies under high AC line voltage and light-load conditions is presented in this paper. The method is both adaptive and iterative and capable of maximizing power factor while total harmonic distortion is controlled within a pre-determined acceptable value. The algorithm can be embedded into a power supply micro-controller or digital signal processor to automatically adjust power factor iteratively under a given operating condition. A simulation model, which is highly correlated with the power factor correction converter stage of a 2kW power supply, is utilized to perform the study to demonstrate the effectiveness of the new algorithm.

I. Introduction

In recent years, although much attention has been paid to achieve the highest 80 Plus Titanium efficiency from 50% to 100% full load, lower-than-desirable efficiency and power factor at high AC line voltage and light-load conditions have always been an issue. Improving light-load efficiency and power factor is still the fundamental obstacle when the next generation power supply is targeted to operate beyond 80 Plus Titanium efficiency with the highest possible power factor when loading is as low as 5% of the maximum rated power.