摘要
发光二极管(light-emitting diode,LED)的伏安特性易受温度影响,且个体间存在差异,当多条LED支路并联连接于同一电压源时,会出现不均流现象。电流大的LED支路老化加速,光效衰减,甚至过早熄灭,严重影响了LED照明的可靠性。针对此问题,提出一种最小导通电流幅值反馈控制的脉宽调制(pulse width modulation,PWM)均流电路,该电路在常见的PWM均流基础上,自动调整LED支路的供电电压,使得LED支路中存在至少一条支路的均流占空比为1,其他支路的占空比尽可能大,有效提高LED光源的发光效率。此外,在该均流电路上,可容易实现LED支路的独立调光,无需增加电路和成本。最后,以Buck变换器驱动3条LED支路为例,搭建实验样机。实验结果证明了所提出的均流电路可有效实现LED支路均流,提高LED发光效率,并具有独立调光功能。
The light-emitting diode （LED） VI characteristics of temperature dependence and devices variation make LED be current imbalanced when parallelconnected LEDs are powered by the common voltage source. Current imbalance will cause fast degradation or even failure in some LEDs that should be avoided in LED applications. This paper proposes a current sharing circuit based on the pulse width modulation （PWM） of a common bus voltage to realize the required averaged current. If it is in balance, a small duty cycle will necessitate a large LED on-time current, which may cause temporal overheat and low luminous efficacy of LEDs. The minimum on-time current amplitude control scheme is then proposed to maximize the duty cycles and improve the LED luminous performance. Moreover, the individual dimming control in each LED string can readily be incorporated into the current sharing circuit without additional circuit and cost. The analysis, implementation and verification are detailed in this paper.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2014年第21期3432-3439,共8页
Proceedings of the CSEE
基金
国家自然科学基金项目(51107009)
香港研究资助局项目(3-RBA3)~~
关键词
LED驱动器
均流
发光效率
调光
LED driver
current sharing
luminous efficiency
dimming
