Research And Design Of Buck DC-DC Converter XD1715 With Frequency Synchronization Function

With the rapid development of electronic technology and integrated circuit manufacturing technology,portable electronic equipments have become greatly popular.The power performance is an important factor to evaluate the performance of electronic equipment.As an important part of power management chip,switching power supply can be widely used in a variety of electronic equipments to ensure the stability and reliability of power supply.However,electronic products update faster and faster,and focus on small size and multi-function.This puts forward new requirements for the design of switching power supply.So the study on designing the efficient and energy-saving switching power supply chip which satisfies on the demand of market,has great practical significance.In this paper,a Buck DC-DC converter XD1715 with frequency synchronization function is designed on the basis of the working principle and control system of DC-DC converter.In terms of circuit function,the charge pump phase-locked loop structure inside XD1715 helps the converter to achieve frequency synchronization function,greatly expanding the application of XD1715.The temperature compensation circuit is added to the traditional bandgap reference circuit,which reduces the temperature coefficient of the voltage reference module,and effectively reduces the influence of temperature change towards the converter.In the aspect of stability,the slope compensation module inside XD1715 can eliminate the sub-harmonic oscillation in the peak current mode controlling system.The error amplifier with Type-? compensation circuit can improve the situation which the crossing frequency is low and the phase margin is small.These two measures effectively improve the loop stability of the system.In order to further analyze and verify the stability of the system,this paper use the switching element averaging method to establish the small signal model and analyze the loop gain,and finally verifies the results through the Matlab simulation.In the system framework,the synchronous rectification adopted by the converter is aimed to improve the conversion efficiency of the chip,and the use of peak current mode can improve the transient response of the chip.In addition,in order to protect the converter,XD1715 also designs the protection mode.XD1715 based on 0.5?m BCD process is simulated with Spectre software on the Cadence.It can be seen from the simulation results that the converter is stable under the specified conditions;the startup and shutdown functions are normal;the frequency range of the frequency synchronization function is 300 k Hz~2MHz,which meets the design requirement;the load transient response characteristics are better;the conversion efficiency is higher,and the conversion efficiency is highest up to 96.5%.At the same time,in the case of abnormal output,Hiccup protection mode can play a role in the protection of the converter.These functions are all in accordance with the intended design goals.In the following work of the design of XD1715,its load transient response and its conversion efficiency will be improved,so that the converter will show more excellent performance.