Design Of Buck DC-DC Converters Based On Dual-sampling And Adaptive Predictive PID Control

Compared with analog controllers,digital controllers are not susceptible to noise,aging,temperature,humidity,process and parameter variations,meanwhile it also has the advantages of flexibility,programmability,and so on.Therefore,digital control technology has been widely concerned in the field of DC-DC converter.However,compared with analog controlled DC-DC converters,the control loop of digitally controlled DC-DC converters have delay time,resulting in the phase lag of converter system.In order to maintain the stability of the converter system,the bandwith of the converter system should be reduced,thereby reducing the transient performance of the DC-DC converter.In this thesis,based on the combination of dual-sampling scheme and adaptive predictive PID control,a digitally controlled Buck DC-DC converter with high transient performance is designed.Dual-sampling scheme is used to reduce the delay time of the modulation process of Digital Pulse Width Modulator(DPWM),while adaptive predictive control is used to eliminate the delay time of analog-to-digital conversion and the process of calculating and processing of digital controller.In this thesis,the transfer function before compensation is established based on the state space model of Buck converter and the function of each module in digital control loop.Then,transfer function of the designed Buck DC-DC in complex frequency domain is transformed into a transfer function in discrete domain,and the parameters of the digital PID control algorithm are tuned with Matlab/Sisotool.Finally,the parameters of the adaptive prediction algorithm are determined according to the PID parameters after tuning.In this thesis,the system simulation based on the Matlab/Simulink and test based on FPGA-based test platform are carried out.Both the simulation results and the testing results demonstrate that compared with the scheme of dual-sampling and the scheme of adaptive predictive control,when dual-sampling and adaptive predictive control are adopted simultaneously,transient performance of the digitally controlled Buck DC-DC converter is much better.In the test,for a load step between 0.5A and 1.0A,the transient recovery time of the designed DC-DC converter based on dual-sampling and adaptive predictive PID control is not more than 102?s,and the overshoot voltage is not more than 120mV.The set-up time and overshoot voltage of ttart-up process are 142?s and 0 respectively,which satisfy the design specification.The maximum steady-state error,the output voltage ripple line regulation,load regulation of are 1.12%,30mV 1.12%and 0.56%respectively,which also satisfy the design specification.