Digital Control Of Interleaved Boost PFC Converter

With the development of digital control theory and semiconductor technology, the application of digital control in electronic power becomes one of the most important research directions in the power electronic technology. The power factor correction techniques is an effective way to improve grid reliability and power quality. In this thesis, an interleaved boost PFC converter is chosen as the controlled plant to show the feasibility of digital control. In order to implement high power density power supply digital control technique, PID controllers designed and tested based on a digital power supply control chip UCD3138 for this power module. Compared with the traditional analog control technique, the use of digital control technique in the interleaved boost PFC converter can keep the good control performance.Focusing on the digital control of interleaved boost PFC converter, the work includes the following aspects:1. Firstly, the working principle of the interleaved boost PFC converter which worked at Continuous Conduction Mode(CCM) is analyzed to show the relationship between interleaved boost PFC converter’s input ripple current and boost PFC converter. In order to obtain the proper main parameters for the PFC converter, the small-signal model is analyzed for the power stage of interleaved boost PFC converter.2. By comparing several typical control mode methods, digital average current mode method is chosen as the control design scheme. Based on the small-signal model, the voltage loop and current loop are designed and digitalized using bilinear transformation method. The current unbalancing of the two interleaved phase is solved by digital controller.3. The software design of control stage is presented based on digital power controller UCD3138. Major voltage and minor current loops use digital PID controller, and an improved transition response method is proposed. A start-up without overshoot of output voltage is proposed based on the flexibility of digital control. Meanwhile, the control method in light-load mode and X- capacitance reactive current compensation method etc. are optimized using digital method.4. In this study, the simulation and the experiment are conducted to verify the digital control method for the interleaved boost PFC converter. The experimental results confirm this effectiveness of the proposed method.