| "With the developing of digital technology, the digital control method becomes widely applied in power converter. Digital control method greatly improves the performance, flexibility and reliability of power converter, and provides the ability to monitor, process and adapt to system conditions. Therefore, digital converter can meet the requirements of almost all power supplies. The performance of digital control converter is mainly determined by digital control software and control algorithm rather than massive discrete components' parameters, which means the decrease of cost and volume of power converter and the great improvement of capacity of realizing complex algorithms. Digital DC-DC converter can cater to the requirements of electronic equipment well.The difference between digital DC-DC converter and analog DC-DC converter lies in the control loop. Due to the loop delay existed in the digital control loop, it is necessary to modeling the digital DC-DC converter, and analyze the influence of the loop delay. For comparison, the working processes of DC-DC converter in different modes are elaborated firstly in the thesis. Then the continuous time model of analog DC-DC converter is established. Furthermore, the structure and working process of digital DC-DC converter are analyzed in detail, and its discrete time model is established.Based on the above work, the loop delay existed in digital DC-DC converter is further researched, including the reasons of different delay and their impact on the control loop. In order to reduce the impact of loop delay and the defect of the traditional one beat delay control method, this thesis puts forward a digital current control method without current sampling. The current of the inductor is estimated by an estimate algorithm without current sensor in the control method proposed in the thesis. At last, taking Buck converter as example, the correctness of the proposed digital control method is verified by simulation through Simulink. |
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