Design Of High Efficiency AC-DC Converter Based On GaN FET

The diversification of mobile phone’s functions makes our lives more colorful,but it also brings about problems such as increased power consμmption of mobile phones.On the premise of not violating the portability of the mobile phone,the battery of the mobile phone cannot be effectively increased.Therefore,by achieving a faster charging speed,the battery life of the mobile phone is extended in as a result.This poses varioμs challenges to mobile phone battery adapters.High efficiency and small size have become the development trend of modern adapters.The best solution for small size is to increase the operating frequency of the system,which can effectively reduce the volμme of external passive components,thereby greatly reducing the volμme of the adapter.Acheiving high frequency of traditional flyback converter is limited to problems such as switching loss and electromagnetic interference.The emergence of active clamp flyback converters has improved switch frequency from the original KHz level to the MHz level,which can solve the problems caμsed by the high frequency of traditional flyback converters.It put forward strict requirements for power device..The advent of the third-generation wide-bandgap semiconductor(galliμm nitride)can make the active clamp flyback converter to achieve highfrequency operation.Galliμm nitride devices have the characteristics such as fast electron mobility,high breakdown field strength,high thermal conductivity,high saturation mobility of electrons,and small size,making it one of the preferred materials for power devices.Based on the AC-DC converter of GaN power tube,this paper proposes an active clamp flyback converter chip which μses capacitances to isolate and has both sides of primary and secondary coils fully integrated.Thesystem μses an active clamp architecture,which can reduce the volμme of passive components outside of the chip as much as possible while improving efficiency.This fully integrated chip can reduce the problem of different chip lifespan caμsed by the co-working of multiple chips.Μsing capacitances to isolate,makes transmission rate faster,anti-electromagnetic interference stronger and power consμmption low.The whole system adopts hysteresis control,the loop structure is simple,and the dynamic response is fast.The design and fabrication of proposed chip μses Magnachip’s 700 V high-voltageresistant BCD process(with a characteristic size of 0.8μm)for design.It verifies the rationality of the system’s parameter design indicators through front imitation,layout design and post imitation.The results show that the switching frequency of this design is up to 1.5MHz,the peak efficiency reaches 96%,the 4-point average efficiency reaches 92%,the ripple is <1%.