Research On Synchronous Rectifier Technology Of Low-power Flyback DC/DC Converter

Nowadays,miniaturization has became an important project in the development of international space and military fields.So it requires the power supply for small-sized space and military equipments to achieve the goal of smaller size,lower power and higher reliability,that means DC/DC converters need to use simple structure,few components,and enable to function properly under hash environments and hostile temperature.However,the conversion efficiency of DC/DC converters which suit low-power,small-volume workplaces is not satisfied.The problem of low-power flyback DC/DC converters’ conversion efficiency improvement has to be studied particularly to promote the performance of national micro satellites and mini military weapons.Flyback topology is chosed as power topology in this paper for its simple structure,few components and suitable for low-power situation accroding to the study target,and the research is launched with the propose of improve the conversion efficiency of the converter.Based on the working principle,working mode and working mode of flyback converter,the loss of flyback converter is studied in this thesis.After listing the loss distribution of each part,the synchronous rectifier with low conduction loss is used to replace the traditional diode rectifier in order to solve the problem that the rectifier loss accounts for the largest proportion of the total loss of flyback converter and the disadvantage of the traditional diode rectifier loss become more prominent when the output voltage is lower.Different voltage and current mode self-driving synchronous rectifier control circuits are designed in this paper.These circuits are simulated and verified by simulations and experiments.The current self-driving synchronous rectifier circuit is selected as the experimental prototype because of its advantages of accurate control,reliable operation and low cost.After determining the overall structure of the circuit,a 5V/3A low power flyback converter with current mode self-driven synchronous rectification is designed.According to the design criteria,each part of the flyback converter is designed in detail according to the design process,and the PCB experimental prototype is developed for testing,also the efficiency and performance of the flyback converter are measured and analyzed.The experimental results show that the efficiency of flyback converter has been effectively improved by using the appropriate synchronous rectifier circuit,the maximum value of efficiency improvement is 4.2%.The efficiency of the flyback converter has exceeded the products with similar parameters at home and abroad,which confirms the role of synchronous recitification technology and achieves the research goal of this study.This design also lays a foundation for hybrid intergration circuit module design,and different synchronous rectifier control methods are showed in detail which provides the research direction of the subsequent design and provides a direction for the research and development of the similar products.