Design Of DC-DC Step-down Converter Based On COT Architecture

Nowadays,the rapid development of electronic equipment in the direction of miniaturization and portability puts forward higher requirements on the power management chip and urges it to develop in the direction of low power consumption and high integration.In recent years,the switching power supply has gradually replaced the linear power supply with lower conversion efficiency due to its advantages of high efficiency,small size,and stable voltage range,becoming the mainstream products in the power supply market.The DC-DC converter controlled by Constant On-Time(COT)has the characteristics of simple system structure,high light load efficiency and fast transient response,and has become a research hotspot in recent years.In this paper,a Buck DC-DC converter based on COT control mode is designed,and the output ripple is sent to the PWM comparator as a feedback signal,and the quick response of loop is realized.At the same time,the converter is integrated with the base voltage source,which reduces power consumption and simplifies the circuit structure.The constant conduction time circuit is optimized so that the conduction time can be adjusted according to the input and output voltage,so that the circuit has certain adaptability.In order to improve the efficiency of the converter in light load mode,a low-power control mode is designed so that some circuits of the converter are put into a dormant state under a light load condition to further reduce system power consumption and improve overall working efficiency.Based on Hua Hong NEC 0.25?m process,Cadence Virtuoso is used to simulate the system.The performance indexes meet the design requirements and the layout design is completed.At the end of this paper,the chip is tested.The test results show that the system can work normally in continuous conduction mode(CCM)and discontinuous conduction mode(DCM).The input voltage is 2.5V ~ 5.5V and the output voltage can be changed by changing the internal Feedback resistor size set,0.8V ~ 3.6V adjustable,the maximum output current 2A,the overall efficiency of more than 85%.The converter has low power consumption,fast response and other features.