基于PWM调光的冷阴极荧光灯动态特性研究

本文在分析了冷阴极荧光灯(CCFL)特性的基础上,对CCFL的驱动电路的工作原理、电路参数选择和设计进行了详细的介绍.研究表明,在脉冲调宽(PWM)方式下,CCFL的驱动电路呈阻尼衰减振荡特征,其起振和衰减振荡特征直接影响CCFL的调光特征,是改善CCFL亮度可调节比的主要因素,文章从理论和实验两方面对亮度调节的动态特性进行了详细分析.

Research on the Dynamic Characteristic for Dimming CCFL Based on PWM

Based on the analysis on the CCFL(Cold Cathode Fluorescent Lamp) characteristic, the paper described the principle of CCFL driving circuit and the way how to design circuit and choose the parameters in the circuit to meet the predefined operating frequency and output voltage. Drived by the PWM(Pulse Width Modulating) mode, the circuit appeared to be the feature of damping harmonic circuit. The dynamic characters at start and end term are the key factors for dimming the lamps. Those mentioned above are theoretically analyzed while experiment data are given in this paper. In order to avoid the flicker phenomena of the display in lower brightness, the frequency of PWM must be more rapid, generally, about 5-7 times than the frame frequency of the display(such as 30Hz for PAL input signal). The minimal turn on/off delay time of the circuit must short than 26 nano-seconds. Both the calculational and measured curves illustrated that the turn off delay of the damping harmonic output is about ten times longer than turn on delay. So reducing the turn off delay time of the circuit driven in PWM is the linchpin of the technology program for dimming the CCFL with large scale.