高增益和多路输出均衡的高效LED驱动拓扑研究

Efficient Multi-output LED Driver Topology with High Voltage Gain

驱动多路并联的发光二极管LED(light-emittingdiode)容易导致各路电流不平衡,为了实现各路LED之间的均流并提高电路效率,提出1种具有多路输出能力的高效率LED驱动电源。采用Boost级联串联谐振变换器的结构实现各路LED之间的均流,并获得较高的电压增益;变压器的漏感抑制了开关管导通时的电流上升速度,实现了开关管的ZCS导通;增加了1个无损缓冲电路减缓开关管关断时的电压上升速度,极大地降低了开关损耗;将变压器的励磁电感设计得足够大,使变压器的损耗降低;在实现软开关的同时,仅需1个开关管,从而降低了电路成本并简化了控制。因此,所提方案在实现均流的同时还能够实现较高的效率和电压增益,且成本较低。详细分析了所提方案电路的工作原理和工作特性,并给出了参数设计的具体流程。最后,搭建了1台输入电压为12 V、两路输出功率为7.9 W的样机,证明了所提方案的可行性。

Aimed at the current imbalance problem in parallel connected multiple light-emitting diode( LED)strings,an efficient multi-output LED driver is proposed to achieve current sharing among different LED strings and improve the efficiency of the circuit.A Boost converter and a series-resonant converter are cascaded to achieve current sharing and a high voltage gain.The transformer leakage inductance suppresses the switch's current rising rate in the turn-on period,which provides the zero-current-switch( ZCS) condition.Moreover,a lossless snubber circuit is added to slow down the switch's voltage rising rate in the turn-off period to significantly reduce the switching loss,and a large magnetizing inductance of transformer is selected to reduce the transformer loss.Meanwhile,only one active switch is used,which reduces the circuit cost and simplifies the control.Therefore,current sharing,high efficiency and high voltage gain are obtained,and the cost is low.The circuit operational principle and operating characteristics together with the specific procedure of parameter design are analyzed and presented in detail.Finally,a 7.9 W two-output prototype with 12 V input voltage was built to verify the effectiveness of the proposed LED driver.