| DC-DC converters are widely used in data center,LED driver,microprocessor and other scenarios,and these applications require both high steady-state accuracy and excellent load transient performance,which converters can work stably in a wide load range and the overshoot/undershoot voltage is small.The time-optimal control method can theoretically achieve the fastest load transient adjustment through one switching to bring the converter to the new steady-state operating point.Based on this concept,this paper intends to explore the DC-DC converter from the perspective of topology improvement and control strategy adjustment method to improve load transient performance.The main contents of the study are as follows:Firstly,the time-optimal control converter’s steady-state controller is designed to solve the secondary adjustment problem existing in the traditional PID control as the time-optimal control steady-state controller.It is analyzed that when PID control is used as the time-optimal control steady-state controller,the converter has a secondary adjustment transient phenomenon that deviates from the steady-state operating point after the transient process ends.In order to avoid this transient problem,the inductor current ripple hysteresis control is constructed as a steady-state control from the perspective of eliminating the DC offset of the control signal.The small-signal model of ripple current hysteresis control is derived and the selection of related parameters is given.It is verified by simulation that the proposed steady-state ripple current hysteresis control time optimal control DC-DC converter has no secondary adjustment after the transient state ends,and can complete the optimal dynamic adjustment process successfully.Secondly,in order to further improve the load transient performance of the DC-DC converter on the basis of time optimal control,the time optimal control of the Buck converter with dynamic auxiliary phase is proposed.Aiming at the problem of multiple steady-state operating points in time optimal control,the structure of dynamic auxiliary phase is introduced.Based on the idea of capacitor charge balance,the switching time of auxiliary circuit in the dynamic process of load is mathematically derived.The calculation formula of the specific switching moment when the load jumps up and down and the selection of auxiliary inductance are discussed.And the simulation comparison of the proposed scheme and TOC scheme is given.This control breaks through the bottleneck limitation of the original Buck main circuit parameters.It has been verified that it can achieve faster load transient adjustment than time-optimal control.Finally,the time-optimal control strategy of the dynamic auxiliary phase Boost converter is proposed.The proposed control idea of the dynamic auxiliary phase is extended to the Boost converter,and the design of the time-optimal control of the Boost converter and the calculation of the switching time of the multiple switching control are mainly discussed.The simulation comparison chart and the actual circuit design and experimental waveforms are given.It is verified that the proposed control strategy can solve the problems of large resistance energy consumption and large input current overshoot in the auxiliary circuit Boost converter of time optimal control,also reduces the transient voltage adjustment and improves the load transient performance of Boost converter. |
