随着便携式电子产品的日益普及，直流电压转换器(DC-DC)芯片得到广泛应用。由于这些产品通常使用单电池供电，能量有限，如何提高转换效率，降低功耗，延长电池寿命，便成为设计者需要考虑的主要问题。 本毕业设计提出了一种基于脉冲宽度调制(PWM)和脉冲频率调制(PFM)模式的高效率、低功耗开关电源直流电压转换器的设计方法。电路在负载电流较大(约>70mA)、电感电流连续时，采用开关频率2MHz的电压型PWM控制工作模式；在负载电流较小(约<70mA)、电感电流不连续时，采用较小的开关频率的峰值电流和电压双重控制的PFM工作模式，实现了在0~500mA的负载电流变化范围内的高转换效率。芯片采用SMIC公司的0.35μm CMOS混合信号模型设计。仿真和测试结果表明该电路可实现PWM和PFM模式供电以及两种模式之间的平稳过渡，具有较好的负载和线性调节能力。输出电压的误差小于土4%，最大静态工作电流小于18μA，最大转换效率达90%。 论文第一章和第二章讨论了开关电源式DC-DC的稳压原理和控制方法。并在第三章叙述了本次毕业设计提出的DC-DC转换器的系统结构及工作模式。第四章具体介绍了DC-DC转换器的主要电路模块的设计思路。第五章给出了BUCK系统仿真结果。

DC-DC converters are widely adopted with the growing usage of portable applications. Since these applications are usually powered by energy-limited single-cell battery，how to improve the efficiency and power consumption to prolong the battery life is the primary consideration in DC-DC converter designs. A design method of a high-efficiency，low-power，switching mode power supply DC-DC converter with Pulse-width modulation(PWM) and pulse-frequency modulation(PFM) modes is presented. The converter operates in voltage control based PWM mode at a switching frequency of 2MHz when the load current is large(>70mA) and inductor current is continuous; and works in peak-current and voltage control based PFM mode with a reduced switching frequency when the load current is small(<70mA) and inductor current is discontinuous，ensuring highly efficient Operation within a large range(0~500mA) of load current variation. The chip was designed using SMIC 0.35μm CMOS mixed-signal process. Simulation results indicate that the converter operates in PWM/PFM modes and performs seamless switching between them，displaying good load and line regulations. The output voltage error is less than士4%，the maximum quiescent current is less than 18μA and the maximum of efficiency up to 90%. Switching-power DC-DC principles and control strategies is discussed in the chapter 1 and chapter 2. And chapter 3 describes the system structure，operating modes and performance of the DC-DC converter. Chapter 4 introduces the design method of some main circuit blocks. Chapter 5 presents systematic simulation result.