Design And Implementation Of High Performance Boost DC-DC Circuit

Power management chips have a trend of higher integration,smaller volume,higher efficiency and more frequent transient conversion.Switching power supplies have become the first choice for power management chips due to their high conversion efficiency and simple circuit structure.Among them,Boost DC-DC converters have a wide range of applications in products with boost demand.In this context,the high-performance Boost DC-DC converter designed in this paper has certain theoretical and commercial value.In this thesis,the defects of the current Boost converter are analyzed.Based on the peak current control and constant off-time control,the control structure of CM-ACFT(Adaptive Constant Off-time Peak Current Control)is deeply studied.The program to improve system stability and electromagnetic compatibility performance and improve conversion efficiency is also given in this thesis.To maintain the stability of the circuit system,converter under Peak Current Control mode requires a slope compensation circuit,while converter under Constant Off-time Control mode requires additional ripple injection circuitry.In this thesis,the peak current control and constant off-time control modes are combined to form a dual-loop feedback system consisting of an inductor current inner loop and an output voltage outer loop,which can improve the stability of the converter.In order to solve the problem that the frequency of the converter can’t be constant under different input voltages,the input and output voltage are introduced into the Off-timer in this paper.The Off-timer is conducive to realize the adaptive adjustment of the switching frequency so as to keep the switching frequency constant and elevate the EMC performance of the converter.In addition,the frequency adjustment circuit is introduced in this thesis,which enables users to choose appropriate frequency according to the demand.In light-load state,the Force Pulse Width Modulation(FPWM)mode can be selected through a MODE pin to ensure that the chip can have good EMC performance in any working environment.For the problem of low efficiency under light-load conditions,the pulse frequencymodulation(PFM)mode is used as another mode selection mode in this thesis.In the PFM mode,the circuit has no switching action in part of the cycle,which can reduce switching losses,improving high conversion efficiency for the system.In this thesis,the circuit design is completed by 0.18mm BCD process.The key sub-modules and the whole circuit are simulated and verified by Cadence Spectre simulation tool.The simulation results show that the efficiency of the converter can reach more than 90% in the heavy load condition and the highest efficiency can reach 97%.The switching frequency remains basically unchanged when the input and output voltages change,and the frequency selection function is available.The system load regulation rate is within ±1%,which proves that the system has good stability.