Research And Design Of Buck DC-DC Switching Power Supply

With the rapid development of portable electronic devices,it is needed that the power mangement integrated ciruict(IC)should have higher perfromance.Based on the analysis of basic principle of DC-DC switching power supply,a kind of buck DC-DC switching power supply,which is suitable for portable electronic devices,is researched and designed in this thesis.The main works are:Firstly,based on the analysis of basic principle of DC-DC switching power supply,the loop control method,modulation method and performance parameters of DC-DC switching power supply are analysed and introduced in this thesis.Secondly,based on the stability analysis of DC-DC switching power supply with peak current-mode control,two kinds of slope compensation circuits are designed for DC-DC switching power supply and simulated in HHNEC 0.35?m BCD process,which inculde constant slope compensation circuit and adjustable slope compensation circuit.Simulation results show that the designed two kinds of slope compensation circuits can avoid sub-harmonic oscillation of the switching power supply system effectively.At the same time,the adjustable slope compensation circuit can provide adjustable slope with the variation of input voltage of DC-DC switching power supply and can avoid the over-compensation of system to some extent.Thirdly,based on the topology structure of pulse width modulation(PWM)buck DC-DC switching power supply with peak current-mode control,basic sub-circuits,which include error amplifier,sawtooth oscillator,internal low-dropout(LDO)regulator,soft-start circuit,bandgap reference,current sensing circuit,PWM comparator and logic control circuit,are designed and simulated in HHNEC 0.35?m BCD process.Finally,based on these designed sub-circuits of buck DC-DC switching power supply,a kind of topology structure of buck DC-DC switching power supply is given and simulated in HHNEC 0.35?m BCD process.Simulation results show that the designed DC-DC switching supply can provide 3.3V output voltage when input voltage changing from 4.5V to 18 V,and achieves maximal output current of 5A,soft-start time of 0.6ms,line regulation of 0.07%/V,load regulation of 0.075%/A and ripple voltage of 62 mV.The designed DC-DC switching power supply achieves very well performance characteristics and meets the performance demands of portable electronic devices.