Parallel connected LEDs operated at high to improve current sharing

Light emitting diodes (LEDs) are have many features that make them attractive for use in an increasing number of applications. For many of these applications it is desirable to have LEDs in parallel. Because forward conduction characteristics vary considerably in for one device to another there is a problem with current sharing in parallel connected LEDs. This paper proposes a new circuit to regulate current in parallel LEDs. The circuit uses a capacitor in series with sets of antiparallel connected LEDs to control the current flow in each of the branches. The circuit is driven with a high frequency voltage generated by a resonant converter. Experimental results show large reductions in current differences between parallel connected LEDs.

I. Introduction

Light Emitting Diodes (LEDs) have started gaining prominence in the lighting industry in the past decade. Their most attractive features are their long life, which is usually greater than 100,000 hours, and their availability in various colors. LEDs are replacing conventional light sources due to their distinct advantages and are widely gaining significance in automotive lighting, signage, and other such applications.