Research And Circuit Implementation Of Low Output Voltage High Efficient BUCK Converter

Electronic equipment,especially portable electronic devices demand for diversified power supply,such as: power supply voltage,load capacity,application under different frequencies.However,for most portable electronic devices(mobile phones,tablets,digital players,etc.),efficiency is one of the most important parameters,because the service life.At the same time,some portable devices also requires low voltage,this not only comes from the development of process,is also in order to adapt to the trend of low voltage.Based on the above consideration,this article analysis the portable devices with low output voltage of the power supply system and efficient and gives concrete realization circuit,we design a constant on time valley current control mode of synchronous buck converter.Use the constant on time,low duty ratio can be obtained,also use margin adjustment technology change the reference voltage input to the error amplifier,so that we can make the output voltage adjustable;In addition the power tube on resistance sampling and adaptive dead band time technology to improve efficiency,at the same time,the control circuit is simple,due to the congenital advantage of this control mode.Paper first summarized the switch power,its development trends are introduced;then summarizes the current control modes(peak current control mode and valley value current control mode and the average current control mode),analyzes the principle and advantages and disadvantages between the current control mode and combined with different modulation mode;Then analyzed the limiting factors of the low duty cycle and analyzes the main power loss of switch power supply,according to different loss part,put forward the different design idea and realization circuit;On this basis,put forward in this paper,the overall architecture design of the chip;Then according to requirements of the chip system,design the inside circuit.Finally,simulation the controller system function and important parameters.Based on the 0.35 um BCD process,using Cadence and Hspice to simulate the circuit and system.The simulation results shows that the chip can output low output voltage of 0.6 V,chip efficiency up to 97% when overloading,light load can reach 67%,the maximum output current 10 A,achieve the desired low output voltage,high efficiency features.