Wide Input Range And High Power Buck Converter Based On Current Mode Control

Within the rapid development of automobile,vehicle-mounted electronic chips tend to be diversified,integrated,and miniaturized by degrees.The 12 V～36 V power supply voltage supplied by automobiles requires additional conversion chips to drive the automotive chips.Therefore,switching power converters have been concerned extensively and become a hot topic for the moment,which has a series of characteristic such as broad input Scope,regulation of output,and low-energy.In view of the demand of market for automotive power management chips which is urgent for higher efficiency and lower ripple,this thesis designs a buck DC-DC converter chip,which reduces the loss of conduction by Sensefet technology and synchronous rectifier technology to improve efficiency significantly.The overall structure of the chip is determined by thoery analysis detailly: Taking the demands of rapid response and high conversion efficiency into account,the PWM peak current mode is applied to control stage.Considering the problem of subharmonic oscillations,this design overlays the solpe signal by compensation module into the current loop.To realize the soft-start function,a three-input error amplifier is proposed which can prevent circuits from overshoot damage effectively during power-on.furthermore,the Major modules of circuit such as internal reference voltage source,oscillator,PWM comparator and internal power conversion have been designed.The module to maintain system reliability such as temperature protection and dead zone delay have been added for the requirements of vehicle-mounted electronic chips under high power and heavy load.Within the use of Simplis software,this thesis carries out behavior-level modeling of the overall chip.The overall circuit of the conversion chip was constructed using Cadence platform.Meanwhile the layout drawing and verification were carried out by SMIC 0.35 μM BCD process.The simulation results show that:When the input voltage is in the range of 10 ～ 40 V,the chip can output 5.5 V stable DC voltage,the ripple rate is 0.3%,the switching frequency of the converter is 330 k Hz,the output current is 1.5A,the transfer efficiency in the input range are more than 80% and highest attainable efficiency is 90%,These indicators show that this chip has good anti-disturbance ability.