Design Of Nonlinear Controller For Digital DC-DC Switching Power Supply

Digital power supply has the advantages of small size, easy integration, high stability, strong anti-interference ability and flexible control mode. It is a research hotspot in power supply field in recent years. And the controller as the key module of the digital power supply, it is responsible for generating the digital control signals. The performance of the controller directly affects the stability and dynamic response speed of the digital power supply, so it is significant to study the high performance controller.In this thesis, a nonlinear controller is designed to improve the dynamic response speed of digital power supply. First, this thesis introduces the basic principle of digital power supply, and analyzes the transfer functions of Buck power stage, ADC and DPWM. Second, the PID controller is designed by using the incremental PID control algorithm in the discrete domain, so that the phase margin and the cut-off frequency and other indicators of the system can meet the requirements of the dynamic response speed and stability of the system. The structure design of incremental PID controller is completed by using the direct type ? structure of IIR filter, and this structure can save the time delay unit, namely save circuit area. Fuzzy Logic Designer toolbox in MATLAB is used to complete the design of fuzzy system. The parameters of PID controller are adjusted on-line by fuzzy system to improve the transient response speed and robustness of digital power supply. Last, the size of the control lookup table is reduced according to the input quantization factor and the input variable universe of the fuzzy system. In this way, the control effect is not affected and the hardware resource is saved.The HDL code of the fuzzy adaptive PID controller is finally implemented in this thesis, and a digital analog hybrid simulation platform of the controller is built by the ModelSim and Simulink tools. The verification results show that when the load from 15A step to 30A, the transient response time of the digital power supply based on the basic PID controller is 55 ?s, and the transient response time of the digital power supply based on the fuzzy adaptive PID controller is 15 ?s, and the output voltage ripple of both condition in steady state is 11.8mV, which shows that fuzzy adaptive PID controller meets the design requirements.