Research On Current Balancing Method For Multi-Output LED Driver

High efficiency, energy saving and environmental protection have been important developing directions in lighting industry. As been the most potential new generation illuminant currently, LED has become a hot topic in recent years. Applications in high power LED lighting and backlighting occasions need to use multi-string LED in parallel, current balancing between several LED strings should be considered. The research of Multi-Output LED driver is based on this background.This paper mainly studies half bridge (HB) circuit based on topology current-balancing scheme. It introduces circuit principle in each modes, analyzes the current balancing effects, summarizes the design considerations of half bridge circuit and the key parameters to affect current balancing, and design two prototypes working in CCM mode and DCM_â…¡mode.Chapter one and chapter two present the background of Multi-Output LED Driver. Chapter one reviews the existing current balancing methods in Multi-Output LED Driver, includes active methods and passive methods. Chapter two systematically introduces several topologies and rectifier structures of secondary side compatible with topology current-balancing scheme, including current fed topology and voltage fed topology, and analyze the advantages and disadvantages of various topologies briefly.Half bridge circuit is widely used in low-power applications greater than 100W. Chapter three, chapter four and chapter five analysis the principle of half bridge circuit which is working in CCM mode, DCM mode and Multi-Output occasion, and indicates the key parameters of the circuit at different working modes, including how to determine the inductor according to the given input and output parameters. Corresponding simulation and experimental results are given then.The conclusion of the whole paper is given in chapter six, this paper proposes topology current-balancing scheme, half bridge circuit is just an example, with no additional components, this scheme can achieve current balancing of two or even more LED strings. Compared with traditional methods, the advantages of the proposed scheme are simple control, precise current balancing and high efficiency.