Power-efficient series-charge parallel-discharge charge pump circuit for LED drive

A charge pump drive circuit for LED lighting is proposed. This circuit is realized with repeated use of a compact unit module consisted of a capacitor and diodes. The series-charge and parallel-discharge operation gives the efficiency better than the conventional converters with ac line input. This paper also shows how to minimize the number of modules for a given number of LEDs. A prototype implemented the charge pump drive circuit shows a maximum efficiency of 95% for 22 LEDs in series with the ac line voltage of 220 Vrms.

I. Introduction

Light emitting diodes (LEDs) are attracting public attention for general lighting these days. It is expected that LEDs will replace incandescent light bulbs or fluorescent lamps as fabrication processes, device designs and assembly technologies grow [1]–[2]. Together with the advance of LED devices, the development of driving circuit is also important to improve the performance and to reduce the manufacturing cost for LED lighting. Fig. 1 shows previously reported LED driver, which is buck type DC-DC converters [3]. The number of components is few in this driver. But DC-DC converters, such as Fig. 1, and flyback converters [4] have bulky magnetic components such as transformer and inductor. And large rms-current causes power-loss when ac line is input source. Therefore this paper proposes a compact and efficient power conversion circuit, which is a charge pump drive circuit with the series-charge and parallel-discharge operation. Figure 1. Previously reported LED driver