【作者】 孔令荣；

【导师】 邹雪城；

【作者基本信息】 华中科技大学 ， 软件工程， 2007， 硕士

【摘要】 白光LED具有发光强度大、效率高、体积小、寿命长等优点,被认为是当前最具潜力的光源之一,已经广泛应用于手机、数码相机、MP3、数字电视、照明等大多数便携式电子产品领域。为了充分发挥其优势,需要配备良好的驱动电源。驱动白光LED,关键是要提供恒定的电流,以保证发光强度的稳定和均匀。利用升压式DC/DC转换器来驱动白光LED具有高效率、高精度、高匹配度、应用灵活等优点,是便携式应用中首选的。本文主要研究的就是用于白光LED驱动的可用PWM模拟信号或经过编程的数字信号进行亮度调节的升压式DC/DC芯片的设计。本文首先分析了开关电源的一些关键技术,从系统的高度剖析了开关电源降低功耗、提高效率和性能的方法,并从白光LED的特性中分析了它对驱动电源的要求。在此基础上,根据芯片的设计要求,构建了芯片的整体系统结构,并对各功能模块作了明确的划分。接着,分析和设计了芯片中误差放大器电路、数字信号调节LED亮度的电路、PWM模拟信号调节LED亮度的电路、过压保护、限流保护以及热关断保护电路等,并给出了仿真结果。最后,用HSPICE对芯片进行了全局仿真:芯片启动时间只需要200μs,输出电压纹波系数仅为0.5%,中等负载下转换效率在80%以上,输出电压达到14.5V时可以实现有效的过压保护,能够实现PWM亮度调节功能,仿真结果表明设计的芯片达到了预期的要求。更多还原

【Abstract】 As one of the most promising light sources with many advantages, such as high luminous efficiency, high luminous intensity, long life period etc, White LED has been widely applied to portable electronic appliances, such as mobile phone, digital camera, MP3, digital TV and so on. An excellent power driver for high performance White LED is essential. The main function of White LED driver is to provide constant current, and now it has become the star of power management field. Using step-up DC/DC converter to drive White LED is a major method for portable applications. The design of a step-up synchronous rectification DC/DC converter Chip, with PWM and programmable digital signal dimming control, is introduced in this thesis.In the main part of this thesis, firstly, some key techniques to reduce power waste and to enhance performance for boost DC/DC are analyzed, and in the same time, the required feature of White LED driver is deduced from the White LED feature. Based on the design requirements of the objective IC and the key technologies which analyzed and studied before, the whole chip’s architecture is constructed and the sub-circuits’function are defined. And then, some sub-circuits such as error amplifier, digital dimming control unit, PWM dimming control module, over voltage protection circuit, current limit circuit and thermal shutdown circuit are then studied in details. Finally, the whole chip simulation results by HSPICE are given: the start-up delay attains 200μs, the output voltage ripple coefficient is only 0.5%, the efficiency is above 80% under moderate load, and the over-voltage protection and PWM luminance modulation are effective.更多还原