Design Of A Buck DC-DC Converter XD1593 With Constant-On-Time Control Mode

In recent years, with the continuous development of electronic technology, more and more portable electronic products such as mobile phones, laptops and cameras have been emerging into people’s daily life. The core part of these electronic products is the power supply, so the quality of the power directly affect the battery life and service life of electronic products. To make the performance of electronic products more excellent, the key is to optimize the performance of the power supply. At present, power supply is divided into linear power supply and switching power supply. Linear power conversion efficiency is low, and it is not conducive to energy saving and environmental protection, so the linear power supply is gradually replaced by switching power supply. Because of the low power consumption, high conversion efficiency and low production cost, switching power supply is widely used in various electronic fields.This paper firstly makes a brief introduction to the switching power supply technology, and introduces the development of switch power supply, research status and development trend, classification and application; Then this paper expounds the theoretical basis of DC-DC converters, and mainly introduces the step-down DC-DC converter topology structure, work mode, modulation mode and control mode; And on this basis, this paper discussed the function characteristics, system architecture, working principle and stability problems of the chip, analysed the principle of some key sub modules in the system, and verified the simulation results; Finally, the function of the whole circuit is verified by simulation, and the layout of the whole circuit is given.The design of the converter is based on the Constant-On-Time(COT) control mode, which does not require the error amplifier and loop compensation network, the system’s architecture is simple, the speed of transient response is fast. The converter choose the operating mode according to load current, and selects the continuous conduction mode when the load is over, selects the non continuous conduction mode when the load is light; the chip uses synchronous rectification technology, in light load mode, choose non continuous conduction mode; the chip uses synchronous rectification technology, the chip uses synchronous rectification technology, makes the system conversion efficiency up to 96% under overload condition, and the conversion efficiency is higher than 85% under light load condition; The input voltage range is 4.2V~16V, the output voltage range is 0.805V~13V, the output current can reach 3A; The chip has integrated the protection module such as under voltage lock, over temperature protection, over current protection, zero crossing detection and so on. It improves the reliability of the chip.Chip XD1593 based on 0.18μm BCD30 V process, using Cadence and Spectre simulation tools to simulate the key sub modules and the overall circuit. Simulation results show that the performance of the chip can meet the design requirements.