Research On Some Key Problems Of DC-DC Converter With Digital PWM Control

With the digital control of DC-DC converter research unceasingly thorough,high performance digital circuit on the circuit performance puts forward higher requirements,therefore,this paper studies two major issues of the stability error and dynamic response of the DC-DC converter based on digital PWM control,and strives to achieve better performance.This paper takes BUCK converter as an example,firstly,has introduced the basic Principle of BUCK converter,has analyzed a detailed BUCK converter CCM mode,has built a model of the BUCK converter with switching converter equivalent transformation principle,has got the transfer function of converter control to output,has designed the PID compensator according to the loop stability criterion,and has obtained the open-loop transfer function of the closed-loop control system of the BUCK converter,and has determined the stability of the closed loop control system of BUCK converter by the Bode diagram method,then has given the main parameters of BUCK converter system,and has discreted the compensator and realized simulation with S function;has analysed the relationship between steady-state error with multi point sampling digital PWM control technology,has given the steady state error relation of one point sampling,two points sampling,three points sampling,and four points sampling,has verified the relation with simulation,has proved the correctness of the theoretical derivation by simulation results(has reduced the steady-state error,has solved the steady-state error);has derived the time of recovery to the steady state after the corresponding load mutation,input voltage mutation with capacitor charge and discharge balance principle,has verified the correctness of formulas(has improved the dynamic response,has solved the problem of dynamic response).Then this paper has designed the main circuit of BUCK converter,over-current detection and protection circuit,driver circuit,voltage detection circuit,JTAG interface circuit and clock circuit,the download mode selection circuit,serial programming circuit,and given the program flow chart of software.Finally,this paper uses the digital control panel based on TMS320F28335,has realized the digital implementation of multi point sampling based on BUCK converter with CCS3.3,and has given the experimental results of the buck converter control system closed-loop output voltage,given preliminary experimental results of the comparison of the output voltage of one point sampling,two points sampling,three points sampling and four points sampling,has verified that the multi point sampling digital PWM control technology can reduce the steady-state error compared with the single point sampling digital PWM control technology,which can solve the problem of steady state error initially.