电子科技大学学士学位论文.doc

摘 要 与传统光源相比较，LED具有体积小、效率高、寿命长、污染少等优点，必将成为未来的照明市场的主流。 本文设计了一个可用于PWM电流控制模式的DC-DC升压驱动芯片的低功耗振荡器。该DC-DC升压驱动芯片集成了大功率开关管、振荡器、PWM比较器、带隙基准电压源、偏置电流产生电路、误差放大器、过压保护电路、欠压保护电路等。文中阐述了开关电源的基本结构、工作原理及其优缺点和PWM调光方式，对基准电压源、偏置、软启动电路、误差放大器、电流比较器、过压欠压保护比较器、驱动等子模块的进行了功能描述，最后重点分析了振荡器电路的原理、参数设计，利用Cadence软件完成仿真验证。 仿真结果表明，在典型的应用条件下，振荡器的频率为20KHz，功耗在0.5mW以下，占空比在百分之二到百分之九十五连续可调，达到了设计要求。 关键词：白光LED驱动、电流模式、PWM调光、振荡器ABSTRACT Compared with the traditional lighting source ,because of the LEDs’ advantages such as small size, high efficiency, long life-span and less pollution, it’s no doubt that LEDs will become the mainstream application in lighting market. This paper designed a low-power Oscillator that could used for a DC-DC boost chip with PWM current-control mode. The DC-DC boost driver IC chip integrates high-power switch MOS, oscillator, PWM comparator, hand-gap voltage reference source, bias current circuit, error amplifier, over-voltage protection circuit , under-voltage protection circuit and so on. This paper first described the basic structure of switching power supply, its principle of working, its advantage and disadvantage, and the PWM dimming. And then explain the function of the sub-module such as hand-gap voltage reference source, bias current circuit，soft-start circuit ，error amplifier, current comparator，over/under voltage protection circuit and driver. At last focus on the principle of the oscillator circuit, its parameter design, and simulation by using Cadence software. The simulation results show that under the typical application conditions, the frequency of the oscillator is 20KHz. The power consumption is under 0.5mW. The duty cycle is continuously adjustable from 2 percent to 95 percent. Meet the design requirements. Key words: white LEDs drivers, current mode, PWM dimming, oscillator目 录 第1章 引言 1 1.1 课题背景及研究意义 1 1.2 国内外研究态势 3 1.3 论文结构及主要内容 5 第2章 开关电源电路原理及PWM调光技术简介 6 2.1 开关电源的电路拓扑结构 6 2.2 脉宽调制（PWM）方式 7 2.2.1 电压模式的PWM调制方式 8 2.2.2 电流模式的PWM调制方式 10 2.3 PWM调光技术特点 12 2.3.1