Design Of A Buck DC-DC Converter Based On Fuzzy-PID Control With Fast Response

With the development of semiconductor manufacturing process, the portable, high-integrated and low-power electronic products get more and more widely used, which brings higher demands on power module. A buck DC-DC converter with smaller size, lower power consumption and higher performance is needed to provide power supply for portable equipments. Compared with the traditional analog methods, digital control methods are more advanced, and more suitable for applying to the control of switching power supply.The main purpose of this paper is to design a buck DC-DC converter with fast response based on fuzzy PID controller, including the design of the main topology of buck DC-DC converter, ADC, controller and DPWM module, the simulation and test of the whole system. First of all, the conventional digital PID controller was designed in frequency-domain, in which response speed and overshoot are balanced to get initial PID parameters according to the system requirements. Then fuzzy algorithm was introduced and the PID algorithm to realize the combination control of fuzzy and PID. The variations of PID parameters were obtained according to the tuning rules and added on the initial PID parameters. The main emphasis of this paper is the design of the fuzzy-PID controller, including the selection of membership function, the design of the affiliated distribution, scaling factor values, the fuzzy rule table and the realization of defuzzification, especially detailed instructions for the formulation of the fuzzy PID rule table. This paper carries on the optimization design for the modules, using MATLAB to complete the modeling and simulation, and then analyzing the simulation results in detail.On this basis, this thesis carried on the hardware and software design of buck DC-DC converter supply, built the circuit testing platform for the verification of the fuzzy PID algorithm, including the open-loop test of main topology and the closed-loop test of the system. Under the conditions of 3.6-5.OV input voltage,1 MHz switching frequency, and 1A load current, the output voltage steadies at 1.8V, with ripple less than 10 mV, peak-to-peak value less than 30 mV, and setup time less than 5ms. Meanwhile, under the condition of 0.4-1.0 A load step, the recovery time is less than 130μs. When the load current is 0.8A, conversion efficiency reaches the maximum 81%. The design met the dynamic and static performance requirements of switching power supply system, and verified the superiority of fuzzy PID algorithm in digital-controlled switching power supply.