Design Of High Efficiency Step-Down DC/DC Converter

As the rapid development of integrated circuit (IC) industry, higher performances of switching power supply are requested by modern electronic apparatus and systems, which include smaller volume, higher power density, higher efficiency, higher reliability, and so on. According to these requirements, especially that of reducing low power dissipation at stand-by status, a step-down DC/DC controller with high efficiency was proposed in this thesis.At first, with overview of the development of modern switching power supply, the target of the controller was presented.Then, based on the design target of chip system, the system architecture of the controller was proposed. The efforts were focused on its efficiency improvement, peripheral components reduction, low voltage circuit design, system reliability, loop compensation and tradeoff between output voltage ripple and efficiency.The core of the thesis was efficiency improvement. Recently, it is a common situation that most of switch power supplies have high efficiency while operating at high and middle load, but have low one at light load. Thus, burst mode and pulse skip mode (PSM) are introduced to improve the efficiency at light load. Burst mode has higher efficiency but bigger ripple voltage and PSM mode has lower efficiency but smaller ripple voltage. In the proposed system, different applications could choose enabled mode.After completing the system architecture, some key modules like error amplifier, current comparator, reference voltage, phase-locked loops and some other protection circuits were designed and simulated in 1.5μm BCD technology. The controller chip was completed based on the system architecture and circuit modules. Some typical electrical characteristics were simulated and analyzed. The system simulation results showed all specifications of the controller were successfully achieved.