Design And Research Of DC-DC Buck Converter Based On Pmbus Management And Current Mode Control

With the rapid development of portable electronic products,multiple functions are intergrated in the chip,and performance requirements are getting higher and higher,correspondingly,the requirements for power management chips are becoming more and more demanding.In the power management unit(PMU),the switching mode power supply is widely used due to its high efficiency,fast response,flexible design and high reliability.The studys in this paper combines the working mode of analog switching power supply and digital switching power supply,which has the advantages of simple and reliable loop control,fast response,low price of analog working mode and flexible configure and multi-point power conversion optimization of digital working mode.Simultaneously,it can avoid the problems of single application and difficult adjustment in analog working mode,as well as complex design and analysis and limit cycle oscillation in pure digital working mode.On this basis,A Buck DC-DC converter circuit based on power management bus and current mode control which can be applied to many scenarios such as low voltage and high current to meet the needs of complex applications is designed.In this paper,firstly,by introducing the research background and the development trends of power management chip,the significance of the DC-DC Buck converter circuit based on power management bus and current mode control is drawn.Secondly,the working principle of the PMBus,the typical control mode and modulation mode of the switching power supply are discussed.Thirdly,a system framework and working principle of the circuit designed in this paper are expounded and verified by simulation.Then,through the analysis and simulation of the PMBus communication circuit and the high & low power transistors sampling circuit,the design scheme is further enriched.Finally,through the simulation of the chip system level,the simulation analysis of the working state of the circuit under different working conditions is given to verify the feasibility and reliability of the designed scheme,and the required parameters performace is achieved.The Buck converter implements a feedback loop using a typical peak current control mode.The configure,high-precision current sampling circuit samples the high & low power transistors current to achieve real-time monitoring of the inductor current,forming a stable and reliable feedback loop.And through the PMBus,the circuit parameters can be configured online and multi-point power output optimization.When the system starts to work,the data is read from the memory cell EEPROM,and the switching power supply is initially configured to make the circuit reach the normal working state.When the external application changed,users can reconfigure the corresponding circuit through the PMBus interface.At the same time,part of the system state or fault information can be stored in the EEPROM to achieve configure performance of the switching power supply.Based on the HHGrace 0.18 um BCD process,the design system circuit and sub-circuit are simulated by Cadence and HSPICE.The simulation results show that the system circuit can stably output 1.2V,1.5V,3V and 3.3V voltages under typical input voltages of 6V and 12 V.And can work stably under different loads such as 2A,5A,8A and 10 A.And through the simulation of the load regulation rate and linear adjustment rate of the system circuit,the calculated load regulation rate is 0.089%,and the linear adjustment rate is 0.13%,which verifies the rationality and feasibility of the scheme.