Research On A Fast Transient Response Of BUCK Type DC/DC Converter

In recent years, due to the development of mobile phones and tablet computers and other portable electronic products, the market demand for the power management chip developed rapidly, at the same time, due to the rise of the new smart wearable devices, the market of power chip is further expanded.With more integrated circuits, the requirements of power supply management chip area and transient response time are also rising. In this paper, A BUCK type DC/DC converter which has the ability of fast transient response is designed, through some improvements to the part of modules to reduce the transient response time of the entire system.This paper analyzes the influencing factors of fast transient response, wherein the system control mode and transient characteristics were analysis detailed, in the paper, some methods which can reduce the output voltage variation and transient response time were proposed. Then, it introduces several methods and techniques to improve the system transient response, including external inductor-capacitor selection、the Miller capacitor multiplier technology and adaptive slope compensation technology. Reasonable choice of inductor-capacitor reduces output voltage ripple, thereby improving the system transient response time; at the output of the error amplifier uses the current-mode Miller capacitance multiplier technology to compensate. When the system is in steady state, the Miller capacitance is equivalent to a large capacitor to ensure stable operation of the system, when the system is large signal transients, it becomes a small capacitor which can increase the transient response ability of the system. In this paper, the adaptive slope compensation technology was used, compared to conventional slope compensation technology, it can avoid the occurrence of excessive compensation and improves the transient response of the system. Next, analysis and design some modules which can influence the transient response ability of the converter, and its performance meet the design requirements. Finally, it introduced the overall system structure of simulation, some important parameters and performance of the converter were analyzed by simulation.In this paper, we choose CSMC 0.5um BCD process to simulate the performance of the modules and overall chip by Cadence and Hspice. The results of simulation shows that the performance of the module circuits and systems meet the design requirements, when the operating frequency is 500 Khz, the transient response time was 50 us.