Design Of Pwm Step-Down DC-DC Switching Converter

With the rapid development of power electronics technology, the increasingly close relationship of power electronic equipment and the people’s work, life, and electronic equipment can not be separated from a reliable power supply, computer power into the1980s the full realization of the switching power supply first to complete the computerpower updating, and into the1990s, have entered into a variety of electronic and electrical equipment in the field, program-controlled switchboards, communications, electronic testing equipment power switching power supply, power control equipment have been widely used switching power supply, but also to promote the rapid development of the switching power supply technology.In this paper, design a5V-3.3V buck DC-DC switching power supply chip. The chip uses a voltage controlled pulse width modulation (PWM), and integrated in the chip’s internal power switches and rectifiers, greatly improve the efficiency of the chip, while simplifying the peripheral circuits. The chip work in the high1.5MHz frequency, so that the external dimensions of the device to be greatly reduced. This article describes the basic theory of the switching power supply, the theoretical analysis of the buck topology, and discusses the advantages and disadvantages of the different control modes and modulation. Reasonably designed according to the different types of PWM switching power supply, each sub-circuit, mainly following seven modules:the error amplifier module, bandgap reference module, ramp generator module and PWM comparator module, as well as over-temperature, over-current, under pressure protection circuit module. In addition, this paper elaborates the power switch tube rectifier design process, and peripheral device parameters selected.In this paper (of CSMC)0.5μmCMOS process models and Spectre and Hspice EDA simulation software for circuit simulation. The simulation results show that the input voltage of4.5V-5.7V change, good stable3.3V output voltage, maximum ripple voltage of25mV maximum load current of550mA the4mA-550mA load range efficiency of more than88%conversion efficiency of93%of the rated load400mA. The simulation results show that the indicators meet the design requirements, to achieve the desired objectives.