| The nolinear DC-DC switching power supply based on inductive energy storage has a wide range of input and output voltage range,higher conversion efficiency,higher load capacity and high integration,all these properties satisfied modern power electronics/equipment especially portable electronic devices demand for power supply.So they are widely used today and enjoy great potential and vast development prospects.This paper takes the nolinear DC-DC switching power supply based on inductive energy storage as the object of study and introduces the basic principle of DC-DC regulator in brief,then this paper comparatively analyzes the difference of several control modes to DC-DC regulator.Particularly,this paper mainly studies and analyzes the control mode of COTCM.The COTCM has the advantages of both COT mode and Current mode,such as simple structure,high conversion efficiency in light-load,fast transient responsed speed and current limiting protection.However,the working frequency fluctuates according to the input and output voltage,the delay of system,dead-time and other factors,which increase the processing difficulty to EMI,the flaws inherent of this mode prevent further increase in transient responsed of the system,and the output voltage fluctuates according to the application environment,all these disadvantages limit the future development of COTCM.Therefore,the optimal design is conducted on the basis of COTCM by this paper.Fistly,this paper introduces the technology of input voltage feed-forward and output voltage feedback,which realized adaptive on-time of the regulator,eliminating the influence of input and output voltage to working frequency.Then,a technology called inner pseudo-PLL is given out to improve the working frequency characteristic by adjusting the on-time of the regulator according to the departure of working frequency and referenced frequency.Thirdly,this paper introduces Translinear Loop to realize the purpose of adjustable working frequency and convenient external synchronization,which broadened the range of working frequency and reduced the difficulty of design of PLL.Fourthly,a novel transient enhanced circuit is designed for boosting the transient responsed of the system.Fively,a circuit called analogic calibration is designed for trimming the output voltage accurately.Furthermore,a on-chip frequency compensation structure for COTCM controled DC-DC regulator is presented on the basis of finding out a accurate model of s-domain.At last,this paper make a summing up of these above optimized designs to obtain a control theories called Enhanced-AOTCM.This paper design a high accuracy,adaptive on_time,valley current sampling BUCK DC-DC regulator by using the Enhanced-AOTCM,this regulator has integration of programmable soft-start,over current protection,over temperature protection,over or short circuit protection and so on.Based on 350 nm 40V BCD process,circuit and layout design,simulation of the regulator are accomplished by using the EDA tools of Cadence.The simulation results show that the proposed system achieved the expected design objective such as high conversion efficiency in light-load,ultrafast transient responsed speed,near-single woking frequency,output voltage of high accuracy and so on. |
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