A Design Of High Efficiency Buck DC-DC Based On Adaptive Constant On Time Control

Today, electronic equipment is faced with the situation of power budget and volume contraction. Which put forward higher requirements of voltage regulation ability, efficiency, response speed and integration of power management chip. Under this trend, Constant On Time control of DC-DC has become the focus of research at home and abroad, because of its characteristic of simple structure, good dynamic response performance and high efficiency in light load condition.This paper introduces a design of high efficiency Buck DC-DC based on adaptive Constant On Time control. It’s structure adopts the technology of the Adaptive Constant On Time control. The power MOSFET’s On-Time is based on the input voltage, the reference voltage and system frequency, which ensure the system has a strong ability of adaptability. This paper has established the model of the main control loop and the frequency lock loop. Then complete the open-loop simulation by using Matlab, which ensure the stability of the system. In order to adapt to more application requirements, the system adopted two kinds of working mode. One of them is the Forced Continuous Mode, which can realize low output voltage ripple and suitable for the low noise. Another one is Burst Mode, which can realize high efficiency in light load because the system woke in Discontinuous Current Mode and some parts enter Sleeping Mode. The simulation and verification work of whole design based on Matlab, Cadence, Hspice and other tools. The chip test results show that the system can work normally and various performance indexes can meet the design requirements.The DC-DC chip is designed with a standard 0.35μm BCD process of Korea Dongbu HiTek. The measuring results show that the system frequency is adjustable in 800kHz-2.5 MHz, the input voltage range is 3.6V-24V, the maximum output current is 2.5A, the peak power efficiency can reach 96.1%, it can work normally in both forced continuous Mode and Burst mode. Multiple indexes of the chip can be adjusted, users can find the best solution according to the requirements of applications. The chip can be used in the system such as high efficiency, low noise. It has a very wide application prospect.