Study On Digital Control Point Of Load Power Supply

With the development of Switching Mode Power Supply technology, distributed power gradually replaced the centralized supply system. Point of Load (POL) power is part of distributed supply system, the feature of load request smaller output voltage ripple and better load regulation performance. Interleaved parallel structure is commonly used in point-of-load power topology, with this structure, it can realize smaller output voltage ripple and faster speed of the dynamic response under the same circuit conditions. The current sharing of each channel is an important problem of such topology. Digital control is a new control method developed in 90s, which has become increasingly popular because of its flexibility, reliability, small size. The control strategy is the key factor to digital power. How to use digital control features enhancing converter performance is an important issue.The digital control strategy and current-sharing of POL power supply are mainly studied in this thesis. Proposed an improved optimal control method, which increasing the dynamic performance of POL power supply a lot. The interleaved multi-phase topology is detailedly analyzed, and the digital control average current mode is proposed to realize current sharing between the paralleling phases. The achievements of this dissertation are as follows:Proposed an improved digital optimal control method to realize the possible least overshoot and setting time. The setting time is divided into two stages and the duty-ratio is under subsection control. The improved optimal algorithm convert the control object from time control to output voltage control based on the relationship between capacitor charge and voltage. The optimal control method is realized only by comparing the sample voltage with calculated voltage. The realization is simple and effective. Simulation and experiment is presented to compare the optimal method with other digital control way. The results show that the former has better dynamic performance.Analyzing the current sharing problem in detail and proposed the digital control average current mode current sharing method. The method avoids the current sharing bus which highly request in the analogue way. The influence of current sharing to current error and output voltage dynamic performance are analysed.A two channels interleaved Buck converter is present as example to analyse the influence of current sharing to converter performance from the view of output impedance. The efficiency of interleaved parallelling converter is also analyzed, and the comparison with single channel output converter is presented. Simulation and experiment results show that the digital average current mode current sharing method has good performance which agrees with the analysis result.