Research And Design Of Buck DC/DC Converter Chip

Power supply is one of the important parts of electronic equipments. Its performances affect directly the stability and reliability of electronic equipment. With the development of electronic technology, the types of electronic equipment are becoming more and more, so the requirements for power supply are more flexible and diverse. With the advantages of simple structure, convenient regulation and high reliability, Buck DC/DC converter is widely used in voltage step-down situation.A current-mode PWM control Buck DC/DC converter chip was designed in this paper. The chip with a built in internal power transistor, has a fixed 380kHz of operating frequency, input voltage range of 4.75V~23V, adjustable output voltage of 0.92V~23V, and with several protection circuits, such as the circuits of under-voltage, over-current, over-temperature. The chip can constitute a complete and reliable Buck DC/DC converter with a minimum number of external components.The thesis analyzed the operational principles of Buck DC/DC topology circuit and control circuit. It is integrated with many function modules, such as bandgap reference voltage circuit, over-temperature protection circuit, error amplifier, voltage comparator, saw-tooth oscillator, bootstrap drive circuit, under voltage lockout circuit, current sensing circuit, etc. All these circuit structures and operation principles are designed and simulated. Finally the feasibility and validity of design method and theory analysis are proved by the simulation results of application circuit of the chip with Hspice of the EDA tool. The chip can realize the prospective target.