氮化鎵閘極驅動器之設計與應用

Abstract

氮化鎵材料具有獨特的材料特性，包含高電子遷移率、高崩潰電壓、高電子飽和速度及高電流密度，非常適合應用於高速與高溫操作的環境。然而，缺乏高頻驅動的驅動器和零電壓導通、負電壓關斷的閘極輸入電壓阻礙了氮化鎵功率開關元件在電源轉換器上的應用。本研究提出一適用於常開型氮化鎵功率開關晶體的閘極驅動器，主要利用光耦合器將驅動極浮接，使上橋閘-源極電壓不受輸出電壓變動的影響，藉此正常驅動上橋開關實現半橋電路的驅動。為了安全性考量，未來將朝向製作常關型AlGaN/GaN功率開關元件，故常關型閘極驅動器也是本論文設計的主軸。透過量測崩潰電壓、I-V曲線、臨限電壓、閘極漏電流、閘極電荷測試，及阻性負載開關切換的電性特性，得知閘極驅動器驅動所需的參數，並利用這些電性資訊，設計符合的閘極驅動器實現於驅動三相直流無刷馬達。

GaN materials have some unique properties, including high electron mobility, high breakdown voltage, high electron saturation velocity, and high current density, which make them very suitable for high-speed and high temperature operating environment. However, the lack of high frequency and no readily available drivers for both zero turn-on voltage and negative turn-off voltage are the factors preventing their application to power converters. This study provides the design and implementation of a new gate driver circuit that is suitable for driving normally-on GaN-HEMT device, which is founded by using opto-coupler to float the driver side. This operation let upper-bridge gate to source voltage of the half bridge circuit won’t be affected by the output voltage swing to drive the upper-bridge power switch successfully. For the safety of the operation, normally-off GaN HEMT device is also fabricated in the future, so normally-off gate driver is also needed. The parameter of the gate driver can be known by measuring transistor electricity, including breakdown voltage, I-V curve, threshold voltage, gate to source forward leakage, gate charge test, and resistive switching test. After all, the drive of the BLDC motor is realized by using these electrical information.