Research And Design Of A High-efficiency DC-DC Buck Converter With Hybrid Modulation

With the development of various protable electronic devices,people wish that batteries of the devices could work for a long time,and the devices could sustain a high-efficiency state during both high-performance operational time and stand-by time.When the device is in the stand-by mode,it only requires a small load current from the power supply.However,when it operates in a high-performance mode,the current it needs from the power supply is very large.Thus,the power management chips are developing the corresponding multi-mode,high-efficieny,and wide load range techniques to achieve those requirments.Based on the above considerations,this article is aimed to research and design a high-efficiency DC-DC Buck converter with hybrid modulation technique.At first,the background of power-supply ICs and the trends of their development are introduced,which brings out the meaning of researching and designing such a high-efficiency DC-DC Buck converter.This paper briefly introduces several basic topologies of DC-DC converter,and it also analyzes the operating principle of DC-DC converters.Next,the main losses in switching power supply systems are analyzed,and several mainstream technical schemes that deal with those problems are put forward,which prepares the basic theories for the later research.Then,the operating principle and implemention schemes of three mode are introduced in detail,and the functions of each circuitry are verified by the analysis along with simulation.At last,through the final simulation of the whole chip,the output waveforms of the circuits in each operation mode are given.Besides,the chart that describes the relationship between efficicney and load current is obtained.This Buck uses the Peak Current Mode as its basic structure,so the circuit operates in PWM mode when it's heavy loaded.However,when it comes to light load situation,the circuit can operate in different modes with the use of an election circuit.In the light load situation,the circuit can enable the sleep mode during Burst Mode operation.In sleep mode,the internal circuitry is partially turned off,and the load current is now being supplied from the output capacitor.In the Pulse Skip Mode,the converter can skip some cycles based on load demand,thus increasing efficiency by reducing switching current.In Forced Continuous Conduction Mode?FCCM?,this synchronous Buck allows the inductor current to reverse during low output loads to remain the constant frequency pulse width modulation.For light load application,the efficiency of Burst Mode operation is the highest,the efficiency of PSM operation is the secondary,followed by FCCM operation's efficiency.Therefore,according to different load conditions,selecting different operation modes can cover application requirements as comprehensively as possible.Based on HHNEC BCD180 process,the simulation results show that the efficiency of the Forced Continuos Conduction Mode is the lowest in light load situation,and the efficiency of the Pulse Skip Mode is higher than that of the Forced Continuos Conduction Mode,but it is less efficient than the Burst Mode.In the situation that V_IN=3.3V,V_OUT=1.8V,Temperature=27?,the circuits can function properly within the load current that vary from 1mA to 7A.The highest efficiency can reach 92%.In the Burst Mode,it can achieve the efficiency up to more than 80%among a very wide load range.