氮化鎵功率元件電源轉換與高效率切換開關適配器研究

Abstract

本研究將氮化鋁鎵/氮化鎵高電子移導率電晶體(AlGaN/GaN HEMT)常開型(normally-on)元件與矽場效電晶體元件(MOSFET)進行串疊電路(cascode)分析，串疊後此GaN-HEMT/MOSFET cascode元件形成常閉型(normally-off)開關，更適用於現行閘極驅動元件。 本研究使用GaN-HEMT進行兩種應用並量測其效率，分別為100W直流升壓轉換器和90W電源適配器，其中100W直流轉換器設計由輸入48V轉成輸出96V，在使用cascode GaN功率元件驅動升壓電路時，在開關頻率500 kHz下，輸出功率100W時效率為94.49%，並用於驅動直流馬達。另外，設計電源適配器使其操作於250KHz高頻段下，藉由高頻操作可以減少系統內部變壓器繞圈匝數，有效讓變壓器體積縮小，並在此系統做GaN-HEMT與 Cool MOSFET操作之效率比較，最後GaN-HEMT在250 kHz運作下效率優於Cool MOSFET，可以得知氮化鎵功率元件在高頻操作下的優勢，最後設計出小體積及高效率的電源適配器。

This study presents design and performance evaluation of 100W DC/DC boost converter and 90W AC/DC adapter based on cascoded GaN-HEMTs power device operated at 500 KHz and 250 KHz switching frequency respectively. In high frequency circuits, proper selection of MOSFETs is required in order to have low gate drive power consumption so that high energy efficiency of the converter can be achieved. Even though Si MOSFET has already known for its popularity in low to medium power converters and high frequency applications, GaN HEMTs device could produce better results. This can be done by reducing the total switching loss, conduction loss because of its low Rds-on and gate drive power consumption of the converter as a result of low gate charge, Qg. The experimental results reveal that GaN HEMTs can produce higher energy savings including gate drive power by gaining approximately 4% efficiency compared to its counterpart, Si MOSFET in a regulated 90 W isolated AC/DC converter. In addition, the converter circuit operated at higher frequencies makes it possible to reduce the size of the energy storage elements such as capacitors, inductors and transformers which in turn results in the compact size, weight, volume and the increased power density of the converter.