Design Of Improved Sliding Mode Control System For Synchronous DC/DC Buck Converter

Switching power supplies are mostly used for power supply due to their high efficiency,simple structure,and good anti-interference performance.As a typical nonlinear time-varying system,the switching power supply system has been paid more and more attention to its control technology.Sliding mode control theory,as a commonly used nonlinear control theory in switching power supply control,can reduce the influence of inaccurate model establishment on the system.Therefore,the sliding mode control method is often used for the control of DC/DC converters,and when the sliding mode controller is used for converter control,it is insensitive to lumped disturbances and is susceptible to external disturbances.In response to this problem,this paper studies an improved sliding mode control method based on the hardware platform of the synchronous buck converter,so that the synchronous buck converter has better dynamic and steady-state characteristics.The main research work completed is as follows:First clarify the topology of the synchronous Buck converter,and outline the role of each component in the converter’s working process.According to the working principle of the converter and the circuit analysis of the on-off conditions of the switch,the open-loop circuit mathematical model of the synchronous Buck DC/DC converter is obtained.The control quantity is introduced through the state space method,the state space model is established,and the mathematical model is analyzed.Characteristics in the frequency domain.Secondly,according to the sliding mode control theory,a sliding mode controller is designed for the synchronous Buck converter,and the controller is analyzed.In order to improve the recovery speed of the sliding mode controller,a non-singular terminal sliding mode control method that can converge quickly is selected.In order to overcome the insensitivity of traditional sliding mode controllers and non-singular terminal sliding mode controllers to lumped disturbances in synchronous Buck converter systems,a generalized proportional integral observer is introduced to enable the controller to effectively compensate for disturbances.In order to further improve the observation accuracy of the observer,an extended state observer is introduced,and at the same time,the non-singular terminal sliding mode controller is not sensitive to external disturbances.Simulation experiments are carried out and it is found that the recovery speed and robustness of the controller are improved.Then,in order to improve the anti-jamming performance of the controller and weaken the chattering phenomenon,the sliding function is modified,and the modified sliding function is introduced,and its stability is analyzed and proved.At the same time,in order to improve the response speed of the controller,a non-singular terminal sliding mode controller based on the improved reaching law is designed for the synchronous Buck converter,and simulation experiments are carried out to verify the effectiveness of the control method.Finally,a hardware experiment platform is designed for Buck converters.Introduced the composition and principle of each circuit in the hardware closed-loop system,as well as the construction and debugging process.According to the configuration of the hardware platform,the corresponding control algorithm program is written,and the effectiveness of the designed control method is verified through the start-up experiment,load disturbance experiment and input disturbance experiment.