Reserch And Design Of A High Efficient BUCK Converter With Adaptive Constant On Time

From the birth of the first transistor in the Bell Laboratories in 1947, to the invention of the first integrated circuit in 1958, until now only lasts for a few decades, the semiconductor industry has brought unprecedented boom on the global science and technology. The 21 st century is a century full of infinite possibilities. In this century, we witness too many great discoveries in science and technology, from the early radio, television, cable telephone and later MP3, laptop computers, smart phones, electronic equipment. Those things make our life more and more convenient. Many of the things that were not even imagined in the past century became possible. "There were nothing we cannot do, only to think." This is probably the best compliment of this century!With the continuous progress of science and technology, while the rapid development of the Internet, the Internet of things seems to be more and more close to us. A variety of basic semiconductor components, sensor and power system and so on is becoming more and more manifest their importance. Become the indispensable thing of rapid development of science and technology. Switching power supply in the power supply system is widely used in almost all electronic products by its smaller size, lighter weight and higher efficiency. Switching power supply has imperceptibly become an indispensable power supply way in the rapid development of electronics industry.In this thesis, we design a high efficient BUCK converter with adaptive constant on time, the PWM control mode with input feed-forward results in ultra-fast transient response and high efficiency. Internal integration of the adaptive constant on time module can generate conduction time with an inverse proportional to the input voltage, even in the wide input range, input voltage will not affect the switching frequency, to guarantee the system good frequency stability. Internal integration of low dropout linear regulator to provide internal power supply, a good control of the system power consumption, while improving the stability of the system.In this thesis, after introducing the basic working principle of BUCK converter, the modulation mode and control mode are briefly introduced, then we focus on the system architecture of the BUCK converter designed in this paper, Including the chip power on and soft start, normal and abnormal switching cycle, overcurrent and light load working process, and abnormal state protection. After a brief description to the chip function module, we focus on the detailed theoretical analysis of adaptive constant on time module, low dropout linear regulator and it’s under pressure protection module, start and pre bias module. The simulation waveforms are used to verify the theoretical analysis results. At last, the whole system is simulated and the key performance indexes are verified.In this thesis, the design of BUCK converter based on the 40V-BCD 0.5μm process, using Cadence circuit design software for the system structure and module schematic drawing, with Spectre simulation software for the simulation. The simulation results show that the overall system function and the sub module function can achieve the expected target.