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| Multi-output LED driver with charge balance in multi-capacitors |
| HU Chen, WU Xin-ke, PENG Fang-zheng, QIAN Zhao-ming |
| College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China |
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Abstract A multi-channel light-emitting diode(LED) current sharing method utilizing the charge balance of block capacitors was proposed to solve the current sharing issue when LED strings are paralleled. The block capacitors are in series with the corresponding secondary side windings of the transformer. By coupling the block capacitors in series, plus with amp-second balance, accurate current sharing among output LED strings is achieved. A four-output LLCC LED driver was constituted by combining the block capacitors and the LLC topology in primary side. The operating modes in one switching cycle are presented. The current sharing principle was also analyzed. By merging four outputs into one, the characteristic gain curves could be concluded for the circuit design guidance. A 150 W four-channel output prototype with 0.35 A/channel was built up. The amplitudes of the current waveforms in secondary side windings were identical and the phases were identical or opposite in the current sharing range, thus accurate current sharing was realized.
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Published: 01 December 2014
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基于多电容充放电平衡的多路输出LED驱动器
为解决多路并联发光二极管（LED）的均流问题,提出一种利用多个均流电容充放电平衡原理的多路LED均流方法.该方法将多个均流电容与变压器不同副边绕组互相串联,通过多个均流电容的串联耦合和均流电容的安秒平衡原理实现多路LED均流.在此基础上,结合LLC拓扑和副边均流电容,构建四路输出的LLCC谐振LED驱动器.详细分析了驱动器在一个开关周期内的工作模态及多电容均流机理,并通过将多路副边输出简化和等效为单路输出,得到电路的直流增益曲线,并给出驱动器的设计原则.研制了一台功率为150 W,每路输出电流为0.35 A的四路输出LED驱动器样机,试验结果表明：在驱动器的均流范围内,流过变压器副边绕组的电流幅度一致,相位一致或相反,保证了各路LED负载的精确均流.
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