Design Of Wide-Input High-Efficiency Buck Converter Based On Current Mode Control

Entering the new century,the development of science and technology is changing with each passing day.More and more electronic products have entered the public vision,and gradually become an indispensable part of people's production and life.Buck converter,as an important voltage drop topology,are widely used in portable equipment,automotive electronics,industrial automation and other fields because of their advantages such as high energy conversion efficiency,wide output voltage range,and strong load capacity.With the continuous growth of various demands,the requirements for the input voltage range and efficiency of Buck converters have gradually increased.So choosing suitable control method and reasonable performance optimization strategy become more and more important in the circuit design process.By comparing the common control methods of Buck converter with the actual needs,this design decided to choose peak current mode(PCM)control architecture with more balanced performance.In order to achieve a wide input voltage range,this paper applies the description function method to small signal modeling of the control loop,and selects reasonable frequency compensation parameters based on the obtained conclusions.In order to solve the problem of low system efficiency in light load applications,two light load control modes are designed in this paper to reduce switching loss.In order to cope with sudden conditions such as over-temperature and over-current,this design adds a variety of abnormal situation monitoring mechanisms to ensure the reliability and safety of the system.Based on the selected control method,a synchronous Buck converter is designed in this paper,which includes the following key sub-circuits: The low dropout regulator(LDO),this sub-circuit has an input power switching function,which helps improve system efficiency and has high power supply rejection characteristics.The error amplifier(EA),this sub-circuit is equipped with an upper limit clamping function,which can prevent the inductor from over-current.The zero-crossing detection circuit,this subcircuit can accurately detect the value of the inductor current,effectively avoiding the reverse current of the inductor.The light load controller,this sub-circuit achieves efficient light-load control through setting reasonable comparison point and control logic.The under-voltage detection circuit,this sub-circuit uses a time-based detection method to detect the gate-source voltage of high side power MOSFET with simple structure and high accuracy.This design uses 0.18?m BCD process for circuit construction and chooses Virtuoso simulation platform to verify the function and performance of the converter.The results show that the Buck converter designed in this paper can achieve a stable output of 0.97 V to 24 V and a voltage error of less than ±3% in a wide input voltage range of 3.6V to 48 V.At the same time,the converter has a maximum load capacity of 5A.The front-end simulation results show that the system can achieve 95% energy conversion efficiency under typical application conditions,and also has more than 70% efficiency under 10 mA light load conditions.In addition to the above key performance indicators,the rest of the system indicators also meet the design requirements.