使用氮化鎵開關元件以降低電源轉換器之共模電磁干擾

Abstract

一種基於疊接技術的氮化鎵元件在近幾年來中高頻(200 kHz to 500 kHz)的應用範圍受到廣泛的討論。基於它元件本身的結構，在元件內部對於底部金屬平面的接法有兩種不同的選擇，可以與汲極或是源極連接，與一般傳統的垂直式結構的Si based Power MOSFET只能連接汲極不同。 本論文提出使用氮化鎵如上所提的兩種接法，經由選用適當的氮化鎵封裝組合來降低電源轉換器中的共模雜訊。就結果而言，可以有效低降低電源轉換器的傳導電磁干擾，除了降低共模電磁干擾以及適當的封裝選擇，其他相關聯的理論說明也都會在本論文中提出。 一個240W LLC搭配一前級PFC的電源轉換器架構設計做為實驗電路來驗證本論文所提出的方法。從結果發現此方法可以很有效低降低傳導電磁干擾，而本論文所提出的方法，也可應用於其他的電源轉換器架構或是換流器。

The gallium nitride (GaN) cascode switch has received much attention recently for line-operated medium-high frequency (200 kHz to 500 kHz) applications. Because of its device structure, there are two package options available with regard to the tab internal connection; either the drain terminal or the source terminal is electrically connected to the metallic plate of the device package, unlike the conventional vertical power Si based MOSFET in which the drain terminal can be connected to the device metallic plate. It is proposed in the dissertation that taking advantage of the unique feature of GaN devices packages mentioned above and using a proper combination of the GaN devices in a converter circuit converter common mode noise can be reduced. As a result, the converter conducted EMI can be reduced. The theory is explained and the rule for proper package selection are described in the dissertertation. A 240-Watt LLC power converter with a front-end power-factor-correction (PFC) circuit was built for experimental verification. In the experiment, significant reduction in the conducted EMI was observed. The proposed strategy can be applied to other converter or inverter configurations. GaN devices provide an option, unavailable in power MOSFET devices to significantly reduce the converter conducted EMI.