Research On The Working Mechanism And Control Strategy Of Power Converter Based On The Switch-Linear Hybrid Structure

With the development of aerospace and industrial technology,the traditional switching power supply or linear power supply has gradually been unable to meet the requirements of high efficiency,high precision,high response speed and high power density in certain applications.Unlike the traditional power supplies,the switch-linear hybrid(SLH)power supply not only has the advantages of high efficiency and high power density of switching power supply,but also retains the advantages of high precision and high response speed of linear power supply.Due to the natural superiorities of structure and performance,SLH power supply has been widely used in many fields such as linear power amplifier,motor drive,and electronic load.In this paper,the working mechanism and control strategy of SLH power supply are specifically studied as follows:In the study of voltage-source SLH power supply,the working process of the system is divided into different working modes,on this basis,the collaborative working mechanism of switching power supply and linear power supply is explained in detail.The strong coupling relationship between the two power supplies in the parallel architecture is analyzed,and a feedforward decoupling control strategy based on the output voltage is given to simplify the modeling process of the switching power supply.Then the voltage compensator and current compensator are designed separately according to the loop gain,and the detailed design process and design guidelines are provided.Finally,the model of the voltage-source SLH power supply is constructed and simulated to verify the feasibility of the voltage-source SLH power supply.In the study of current-source SLH power supply,the working principle of voltagecontrolled current source is explained based on the device characteristics of the field effect transistor.Then,in view of the problem that the DC operating point of the field effect transistor is offset due to the pre-stage voltage,a control strategy based on the voltage drop of the post-stage field effect transistor is proposed.By dynamically adjusting the reference voltage of the pre-stage switching power supply,the loss of the field effect transistor in the linear power supply is further reduced.In particular,it is pointed out that the linear power supply essentially affects the switching power supply by changing the damping of the system.Then the small signal modeling of the switching power supply and the linear power supply is carried out,on this basis,the transfer function of the power circuit and the AC equivalent circuit model of the SLH power supply are derived,and then the voltage compensator and current compensator are designed separately.Finally,the model of the current-source SLH power supply is constructed and simulated to verify the feasibility of the current-source SLH power supply.Finally,a voltage-source SLH power supply prototype and a current-source SLH power supply prototype are developed separately,and the two SLH power supplies are tested regarding power efficiency,output ripple and dynamic response speed.The experimental results show that the SLH power supply has higher efficiency than the linear power supply,lower output ripple and faster dynamic response speed than the switching power supply.