Research On Current-mode PWM Switching Power Supply Chip

With the rapid development of information industry, the further reconstruction of traditional industry, and the continuing demands of energy saving, the market of switching power is expanded rapidly. The switch power is widely applied in the field of communication, computer, and so on because of its remarkable advantages of compact size and high efficiency compared with conventional power. Due to the trends of miniaturization of computer system and other kinds of portable electronic products, the power system is required to be smaller, lighter and higher efficiency. In this situation, to design high efficiency switching power supply chip is valuable in the view of both economy and research.This thesis focuses on research and design AC-DC switching power. In this thesis, the operational principle, design approach and system characterization are presented in detail, and a higher efficiency and lower power AC-DC power management chip is designed. This chip adopts the current PWM control mode. At first, the fundamental principle of monolithic current-mode switching controller is introduced, which is followed by a comparison between voltage-mode and current-mode controllers where the pros and cons of both controllers are discussed in detail. Next, the global system architecture is proposed upon the design requirements and sub-block circuits are also introduced that focuses on several essential sub-blocks such as error AMP, VREF and OSC and so on. In the part of OSC, the CMOS chip prevents EMI by using frequency jitter technique. Finally, all sub-circuits and the whole chip circuit are simulated and verified by Cadence.The chip has been finally fabricated with 1.2μm CMOS process and tested. This chip has shown high-efficiency,prevent EMI and low-power loss, which can be used in mobile phone ,digital camera and mp3 and so on.