Study On AC/DC Power Controller System With Muti-mode Fly-back Secondary Feedback

In recent years, a variety of functional and novel electronic products have shown up, people's life is also has changed with the emergence of these electronic products today, personal computers, LCD TV has become no longer new, more portable devices like smart phones, smart watches and tablet computers have been popularized. Consumer electronics products play a more and more important role in people's lives. At the same time, people have more requirements for these electronic products, better performance, better portability, energy saving and environmental protection, etc. And power supply as the energy source and power of all electronic products, also should meet the higher demands. Many new devices have been invented in power supply technology, and new topologies and working modes are proposed for obtaining better performance. Switching power supply has been widely used in various fields due to its high conversion efficiency, low power consumption, energy saving, and environmental friendly. Among them, in the medium and small power use like adapters, AC/DC converter power supply technology, the fly-back topology structure becomes the best choice because of its excellent input and output isolation performance, lower product cost and light weight, small size.In this paper, an AC/DC converter based on secondary feedback mode is designed. The feature of the chip is that it can automatically adjust the operating mode through the change of load, so that it can achieve high conversion efficiency and low power loss in different situations. In full load or heavy load conditions, the converter uses PWM modulation to work in continuous mode. When the load decreases, the system enters DCM works in valley switching mode, and the system converts the green mode when the system is light load or no-load. This design improves the conversion efficiency of the system in the whole load conditions, and reduces the power consumption of standby time. In addition, the chip is integrated in the internal circuit of the under voltage lockout circuit, the edge blanking circuit, over temperature protection, over voltage protection and other protection functions to ensure that the chip is stable and reliable.In this paper, the working principle, working mode and modulation method of the fly-back converter are introduced, and the architecture of the chip system is given. Then, design and Simulation of each module of the chip integrated architecture are presented. Finally, the simulation and optimization of the whole chip and the design of the chip layout are carried out. In the process of design and optimization, the design of the side feedback AC/DC is accomplished. The design of the chip is based on the 0.35?m 30V/5V BICMOS high voltage SMIC process, the chip works in 90Vac-264 Vac, the rated output is 18V/1A The conversion efficiency is 78%, and the linear load rate is 0.5%. The performance of the whole chip meets the design requirements.