Research And Design Of Synchronous Buck DC-DC Converter XD1717

Owing to the rapid development of science and technology,a variety of trendy and multi-functional electronic devices spring up,which brings convenience and abundance to our lives.Almost all electronic products need constant voltage or current power supply.Therefore,the performance of the power supply has a great influence on the security and function of electronic products,and finally affects the market acceptance and share.Meanwhile,electronic products have a tendency of smaller size and lower consumption in order to have better performance and nicer experience of the consumers,which urges power engineers to modify and perfect the power management technology.Based on the author's switching power supply project,this paper has completed the research and design of buck DC-DC converter XD1717 operating in the peak current mode.Firstly,this paper describes the development process and current situation of switching power supply.Then,this paper focuses on the topology,working principle,working mode,control mode and slope compensation technology of synchronous Buck DC-DC converter.What's more,according to the application environment and functional requirements,the system structure and the electrical characteristics of XD1717 are determined,and the division of the functional modules and the design of the system loop stability are accomplished.Subsequently,some functional modules of the converter's working principle is analyzed and their function is verified by the simulator.After all the functional modules are completed,we combine them into a unity and simulate it.According to the simulation results,we correct and modify and the circuit design to meet the electronic characteristic.Finally,the converter layout design is completed.XD1717 is a synchronous buck switching power supply,mainly used in digital set top boxes,personal video recorders,flat panel television and other electronic devices.XD1717 uses PWM control mode,by adjusting the duty cycle of the output control signal to obtain the desired stable output voltage.In order to improve the conversion efficiency of the converter,XD1717 uses synchronous rectification technology,supplemented by dead time and zero crossing detection circuit to eliminate the possibility of a destructive shoot-through condition in which both MOSFETs conduct simultaneously and reverse current.At the same time,there are several protection circuits(such as UVLO,OCP,OTP,etc.)to prevent all kinds of extreme working condition damaging converter and ensure that converter works safely and reliably.The peak current mode control method is adopted in XD1717,which greatly improves the transient response of the system,and eliminates the bipolar point of the LC filter.Meanwhile,the slope compensation is introduced to suppress the sub-harmonic oscillation when the converter's duty cycle is more than 50%.In addition,XD1717 has a soft-start circuit to achieve a smooth rise in output voltage,to prevent the damage from the surge current caused during start-up.XD1717 uses 0.5?m 5V/30 V BCD process,Cadence and Spectre for key functional modules and the overall circuit simulation verification.The simulation results of the design meet the system requirements.