Research Of High Efficiency Step-down DC-DC Chip With Frequency Synchronization Function

High efficiency electrical portable products has token a large share in electronics consume market, power supply chips have been used more and more. How to improve the efficiency has becoming an important research area in designing power supply chips, besides, sometimes there is greet beat frequency inference between power supply chips and system, so, how to solve this problem also has becoming an important research area.This thesis first declares the buck-topology converter's work and feedback control principle, and then it researches why the PWM-controlled chips have poor efficiency in the light load conditions, the conclusion it gets is that the main power waste is because of the power MOSFETS'frequent switching actions. Secondly, it supplies the basic chip information according to the using information, and then it designs the whole chip's function diagram and typical use circuit. Thirdly, it designs some sub-circuits of the chip, these sub-circuits combined mainly used to realize the Burst mode and Frequency Synchronization mode functions. Lastly, based on the typical use circuit, it shows some simulation results to improve that the former design goal has been achieved successfully.The burst mode introduced in the thesis can improve the efficiency when chip works in the light load condition. Its characters represent that: in the light load condition, chip will only work several cycles, in this period the output voltage will rise, when it goes up to a special value, the chip and both power MOSFETS will be shutdown, the following time the output voltage will go down. The frequency synchronization mode introduced in the thesis, its characters represent the oscillator in the chip is consisted by a windows comparator and an exterior pulse proceeding circuit, the oscillator can let the chip works as the external frequency.The design is implemented base on the 0.6μm BCD technologies, with the fully system-level simulations. The results indicate that the controller has a fast transient response and a good soft start performance, upstanding load regulation less than 2% and quite fine efficiency up to 92% in typical application.