Study On Load Time Optimal Control Strategy Using Auxiliary Parallel Inductors Witching Scheme

The fast load transient response is an important performance index for measuring the power supply quality of the DC/DC converters,which is closely related to the adopted control scheme.The load transient performance of traditional linear control schemes such as PI control cannot meet the requirements of the current DC electric equipment.At present,for the DC/DC convertors,circuit adjustment schemes and time optimal control schemes are often adopted to obtain fast transient response.Although the time optimal control scheme can obtain the optimal load transient performance at the control level,its control effect is necessarily subject to the filter element parameters.Therefore,this paper takes the Buck converter as the research object,adopts the scheme that changes the filter element parameters of the main circuit dynamically,combines the principles of time optimal control with the scheme of adjusting the filter element parameters to put forward the load time optimal control strategy using parallel auxiliary inductor switching scheme.The proposed control strategy is applied to the DC power module which adopts the Buck converter structure,and the feasibility of the proposed control strategy was verified by the simulation and experiment results.The research contents of this paper are following:Firstly,the scheme of adjusting the main circuit filter parameters studied,and an auxiliary parallel inductor circuit and the time optimal control strategy based on the auxiliary parallel inductor are proposed.Based on the principles of the time optimal control,the mathematical relationship between the transient performance indexes of the Buck converter and the main circuit filter element parameters is deduced.Then the variable inductance scheme based on the parallel inductor is proposed,and the corresponding parallel auxiliary inductor circuit is designed.Moreover,the mechanism that the adjustment of filter inductance improves the load transient performance is analyzed,and the constraints of the parallel inductor circuit are explored.The control algorithm of the parallel auxiliary inductor is obtained according to the charge-balance principle.Secondly,the main circuit filter inductance adjustment scheme was studied and the sequence switching time optimal control based on auxiliary parallel inductor is proposed.The theoretical analysis shows that the mathematic relationship between the operation times of auxiliary parallel inductor and the voltage deviation is obtained,and the load transient performance could be further improved by the auxiliary parallel inductor.According to the principle of charge-balance,a mathematical model is established to derive the relationship between the times of the auxiliary parallel inductor switching and the auxiliary inductance.The selection principle of the auxiliary parallel inductance is obtained.The control algorithm of the sequence switching time optimal control based on auxiliary parallel inductor is analyzed in detail.Finally,simulation and experiment are completed to verify the proposed control strategy.A simulation module of Buck convertor and its control circuits are built in PSIM software platform.And a practical 30V-15 V DC power module containing Buck convertor main circuit and the control circuit is designed for the experiment.The results of simulation and experiment confirm that the proposed schemes can achieve fast load transient performance which is better than the time optimal control scheme.