A Design Of An Efficient Buck/Boost DC-DC Converter

With the rise of portable digital products,batteries,as an integral part of its life time and availability are particularly important.Long standby time of the device is more popular with consumers.So that the power management chip design presents new challenges-higher efficiency,lower power consumption and smaller size.In this paper,the research status and development trend of converter for a brief overview,describes the control method of a high performance four switch in the three kinds of basic topological structure.Then the converter and control method works as a benchmark to complete its overall structure,and gives several important sub-module circuit structure,including the bandgap,OSC,OTP,UVLO and other important sub-module circuit-level design.Bandgap reference voltage with zero temperature coefficient;OSC with a current charge and discharge the capacitor to produce a constant frequency;OTP is the use of negative temperature coefficient of the transistor to achieve protection;UVLO is realized by the current value of real-time detection resistor.Later,with the Spectre simulation tool for simulation of various important modules and the whole circuit,and the simulation results show that the functional circuit has reached the desired target.Compared with conventional single mode converter,the converter can be determined in the boost,buck or buck-boost mode control of the state of the four switches according to the input voltage,this increases the input voltage range,improve the utilization of the battery.This design is based on CSMC 0.5um Mixed-Signal Technology.Simulation results show that this converter has the following advantages:low output ripple,fast transient response and high conversion efficiency.