Research And Design Of BUCK DC/DC Converter With Wide Input And High Efficiency

With the development of integrated circuits technology,portable electronic devices,and new energy vehicles have become more and more common in daily life.Therefore,improving energy efficiency can make the device work for a longer time.BUCK DC/DC converters can offer stable supply voltage,enhance energy utilization efficiency.With the application environment becoming more complex,the requirement for energy conversion efficiency,input voltage range,and output current ability of BUCK converter have increased.Therefore,choosing a proper control and modulation cheme is an important step in the BUCK converter design.By analyzing the application environment and features of control methods,this thesis chooses the peak current modulation scheme.To achieve a wide input voltage range,this thesis chooses the BCD process to design circuits.This thesis analyzes the small-signal model by description function method and designs proper frequency compensation circuits.Aiming at improving conversion efficiency,this design chooses charge pump and bootstrap circuits to supply operating voltage for drive circuits.In the typical application,the on-resistance of MOSFET can reach 0.04 ohm,and the switching frequency is about 330 kHz.At the same time,this thesis uses the output voltage of the BUCK converter as the operating voltage of internal circuits to decrease the static loss.In order to improve the reliability of circuits,this thesis designs undervoltage protection circuits for low input voltage situations.To decrease the ripple voltage,this thesis chooses suitable peripheral components according to the input voltage and load current.This design includes the following key sub-circuits:The bandgap circuit,this sub-circuit can work in the whole input voltage range and has a low linear regulation.The charge pump circuit can provide stable output voltage with an input voltage range from 6.5 V to 60 V to make the power transistor work in the deep linear region.Therefore,the conductor resistance is reduced.The oscillator output is insensible to temperature and operating voltage.The oscillator offers stable frequency for feedback circuits and frequency compensation.The low dropout regulator with over-current protection circuits can provide 2.6 V or 3.3 V optional output voltage controlled by the digital signal.Over-current protection circuits can limit the maximum output current and prevent short-circuit.Based on the 0.25 μm BCD process,this thesis simulates circuits by the Cadence platform.Simulation results reveal that the maximum ripple voltage is 4.4 mV in light and heavy load applications.The front-end simulation results show that the conversion efficiency is up to 90%in the typical application and the minimum conversion efficiency is 77%with the input voltage range from 6.5 V to 60 V,the simulation results meet the design requirement.