The Analysis And Design Of Dual Buck Switching Mode Power Supply

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.