串疊氮化鎵功率元件之拓樸實際應用

Abstract

以氮化鋁鎵/氮化鎵半導體作為高電子遷移率電晶體(HEMT)時，相較於傳統以矽為主的場效電晶體(FET)，此元件常開且適用於高頻操作。電力電子常用的拓撲隨著半導體的發展而不斷變化，近年來氮化鎵材料在業界積極被開發，因氮化鎵具有其優良特性，實現了需要低導通電阻和出色體二極體特性之拓樸，從而將應用擴展到傳統場效電晶體無法充分發揮之領域。本研究導入串疊(Cascode)結構，以常開型(normally-on) GaN-HEMT氮化鎵元件結合低壓矽場效電晶體，兩者進行串疊電路，形成常閉型(normally-off)開關元件。串疊氮化鎵結合了氮化鎵本身出色的反向恢復(Qrr)特性，低導通與低開關耗損，減少切換間能量的流失，進而改善電源系統開關效率。因串疊後氮化鎵具有與MOSFET功率元件相同工作原理，可直接替置現行以MOSFET作為電力轉換之驅動開關元件。本研究致力於將常閉型氮化鎵功率元件應用於不同電力電子拓樸中，包含以高效率系統驅動之直流無刷馬達及微型太陽能逆變器，並加以分析與MOSFET間差異，通過數位控制與驅動電路整合下，擴展了串疊氮化鎵之拓樸應用。

Normally-off GaN-based high-electron-mobility transistor (HEMT) have been developed with fast switching and low conduction losses. This study dedicated in applying normally-off GaN in conventional power electronic circuit topologies including high efficiency BLDC, and Micro Solar Inverter. Two different topologies: synchronous/nonsynchronous rectification, and ZVS full-bridge, are been investigated for GaN power device because of their fame of low Rds(on) and a superior reverse-recovery charge Qrr comparing to Si power MOSFET. Under 3x faster switching and 1.66x less power loss, GaN improved 2.73% efficiency than Si-based MOSFET with 250KHz switching frequency for boost converter topology.