Design And Modeling Of AC - DC Converter Based On Primary Feedback

Currently, with all kinds of portable products widely used, people’s life become more convenient. These products need a stable power supply, so the requirement for power management chip is higher and higher. Switch-mode power supply is widely used in power management system due to its high efficiency and low cost.Switch-mode converter consist of boost and buck topology, which is simple and with high efficiency. But in small power applications, the traditional basic converter topology will not be able to isolated input and output completely, which may cause in some instability. At the same time, many applications don’t need such high operating voltage, so the basic converter topology requires a second stage DC-DC converter to achieve the voltage, which increase the loss. So flyback converter topology come out to overcome the problem, which uses a transformer to transmit power and store energy, and users can adjust the output voltage by adjusting the turns ratios of the transformer. The most important is that it realizes the electrical isolation between output and input, which makes circuit safe and reliable.But in the traditional flyback converter, a photoelectric coupler is adopted when realizing the voltage feedback control, which greatly increases the cost, reduces the reliability and efficiency, and makes the circuit instable. It gradually can’t match the requirement of some low power applications. So in this text we mainly aimed at the flyback converter improvements, and design a set of primary-side regulationg AC-DC converters, which sampling the voltage from the primary side coil, and circuit principle and simulation analysis is discussed in turn.