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发光二极管(LED)的U-I特性适合采用恒流电源驱动。由于峰值电流控制的模式简单方便,在LED驱动电路中常采用双环峰值电流控制,使大功率LED的驱动电源稳定工作。但是当电源的占空比超过50%且电感电流连续时,峰值电流控制模式就存在次谐波振荡的问题,当电流内环被噪声或瞬态干扰时就不能精确控制LED发光亮度。在双环峰值电路控制中加入斜坡补偿信号,能有效解决次谐波振荡引起的问题。因为LED的负温度效应会使输出电压降低从而引起LED的损坏,所以将传统双环峰值电路中的电压外环改进为电流外环,改善了LED的负温度效应引起的问题。最后通过数字仿真软件Multisim 10对改进后的双环峰值电流控制系统进行了性能验证。
The U-I characteristics of light emitting diodes (LEDs) are suitable for use with constant current power supplies. As the peak current control mode is simple and convenient, often used in the LED driver circuit double-loop peak current control, high-power LED driver power supply stable work. However, when the duty ratio of the power supply is more than 50% and the inductor current is continuous, the peak current control mode has the problem of subharmonic oscillation. When the current inner loop is disturbed by noise or transient, the LED brightness can not be precisely controlled. Adding the slope compensation signal in the double-loop peak circuit control can effectively solve the problems caused by the subharmonic oscillation. Because the LED negative temperature effect will reduce the output voltage and thus cause LED damage, so the traditional double-loop peak voltage circuit outer ring improved current outer ring, LED negative temperature effect to improve the problem. At last, the performance of the improved double-loop peak current control system is validated by the digital simulation software Multisim 10.