Research On A Step-down DC-DC Converter Control Model

With the continuous development of the switching power supply, People have higherrequirement for electrical equipment. The step-down converter (Buck) is the most typicalcircuit topology of switching power supply, and it is widely used in national defense,communications, computers, household appliances and other equipments. As to the driverproblem of Buck converter, I will seek a wide duty driver form of Buck converter in thispaper on the basis of Buck theory.The problems of Buck converter are showed in the article through the analysis of Buckcircuit. Because the switch of Buck converter is located in the high side, it needs to adoptisolation drive mode. Bootstrap method, pulse transformer method and optical couplermethod are introduced in this article. But the three drive forms in the large duty are not verygood at driving the switch. The three drive forms need to add level conversion circuit inisolated drive. Thus the driving circuit is complicated. Therefore, This paper is based on thetraditional Buck converter, with conducting the deformation evolution, proposing a directdrive of Buck converter, with large duty, wide input voltage, non-isolated. The paper analysisand discusses in-depth of the Buck equivalent conversion circuit and feedback circuit. Thedirect drive of the novel Buck conversion has the advantages of large duty, Simple drivecircuit.Comparative experiments between bootstrap method, pulse transformer method, opticalcoupler method and the direct drive are accomplished in this article. A summary is reached byconducting deeply analysis of the waveform and the experimental results in the paper. Finally,the advantages of the direct drive on the theory and practice are confirmed in the paper.Compared with the Buck converter, the switch of novel Buck converter is located in the lowvoltage side, with the advantages: PWM control and gate in common ground, no conversioncircuit, the simple circuit, the low cost. The duty of direct drive mode can reach1,significantly higher than the other three types of driving mode.