Research On All-GaN Integration Technology Based On Dynamic Characteristics Of GaN HEMTs

In recent years,GaN power HEMTs have been adopted in emerging applications(e.g.fast charger,Li DAR & Datacenter etc.),where its unique superiority of high switching speed endows the GaN-based power system with significantly increased power density.Because of its important role in national security and industrial upgrading,it has become one of the key research topics in integrated circuits of China.In the newly announced Outline of China's 14 th Five-Year Plan and Vision 2035,it is clearly proposed to accelerate the development of gallium nitride and other wide-bandgap semiconductors.GaN power devices are facing new opportunities and challenges,and higher requirements are being placed on GaN power transistor-based power electronics systems.At present,the dynamic characteristics of GaN HEMT in high-frequency applications,including selfheating effects and current collapse problems,as well as the integration of GaN power systems have gradually become the focus and hotspot of research in the field.The main research contents of this thesis are as follows:(1)The application of GaN devices in Buck converters is mainly based on discrete devices for system design,GaN HEMTs bring higher power density and higher efficiency to the system,but also inevitably produce a more serious self-heating effect.In order to assess the impact of self-heating effect on system performance more accurately,this thesis quantitatively calculates the power loss caused by the self-heating effect of GaN HEMTs in Buck converters.Research has been conducted from the perspectives of devices and circuit systems,and a method of combining theoretical calculations and experimental measurements has been adopted.In addition,the influence of dynamic on-state resistance of GaN HEMTs on the power performance of the converter is introduced.(2)In addition to self-heating effects and current collapse problems,EMI issues in system design based on discrete GaN devices is another important factor restricting the performance of GaN power systems.To solve this problem,a new GaN system design scheme,All-GaN integrated design,has been proposed and attracted great attention as soon as it appeared.In this thesis,the Spice model of high-precision silicon-based GaN devices was established,which is also the cornerstone of the All-GaN integrated circuits.Self-heating effects and trap models are added to improve the accuracy of the Spice model.The device modeling is also used to link the device dynamic characteristics to the AllGaN integrated design.Then,an All-GaN integrated gate driver with dead-time control is designed and simulated using the Spice model.The circuit introduces a feedback structure to realize dead-time control,which effectively prevents the current through in half-bridge structures.At the same time,the static leakage of the circuit is effectively reduced by using a combination of primary and secondary sides in the design of the NOT and NAND circuits.