Design Of Controller In Digital Power Supply For Improving Transient Response

Digital controller is the core part of digital power system, which is responsible for the control system's response speed and the stability. Digital controller is widely used in industry, information, transportation, education and other fields because of its high reliability, flexible design, optimum performance and short design cycle.The design of a digital controller to improve the transient response of the digital power supply is introduced in this thesis. Firstly, the working principle of digital power supply system is introduced and the basic principle and model of three sub modules of power stage, ADC and DPWM are analyzed. Then, the basic digital PID controller is designed by the SISO tool in Matlab and the improved structure controller is designed. Improved structure controller is a hybrid controller which is composed of PD control and PID control, the part of PD control has no integral coefficient and can speed up the dynamic response speed, the part of PID control has characteristics with high phase margin. In this way, the overshoot and the time of stability can be reduced. According to the range of the error signal of the controller's input, the threshold value is set in the improved structure controller. When the input error range is greater than the threshold, the PD control will be used, when the input error range is less than or equal to threshold, PID control will be used. After the regulation of these two kinds of control mode, the transient response speed of digital power supply was improved.The improved structure controller is modeled and simulated with system in Simulink. At the same time, the improved structure controller is implemented with HDL code and the co-simulation of ModelSim and Simulink is carried out. Simulation results show:input voltage is 3.3V, output voltage is 1.5V, the switching frequency is 1MHz, the transient response time of improved structure system in the situation of decreased load is 27?s and in the situation of increased load is 18?s, which both meet the design requirements.