| 摘要: | 元件動態量測使用雙脈衝量測(double pulse test, DPT)方法時，該雙脈衝量測的操作模式為硬開關且有電阻式負載和電感式負載，而本研究動態量測所使用的模式為電感式負載，除了待測物開關元件本身，還需要額外一顆續流二極體作為待測物關閉時的續流路徑，而這顆續流二極體的反向恢復特性就會影響到待測物開關元件開啟時的切換損耗。
本研究利用碳化矽金氧半場效電晶體架構之1200 V商用元件Cree C2M0080120D、Infineon AIMW120R060M1H、Toshiba TW060N120C (有內建蕭特基二極體)，以及碳化矽蕭特基二極體架構之1200 V商用元件Infineon IDW30G120C5B、Rohm SCS230KE2HR進行在半橋電路中的不同續流二極體對開關元件的硬開關特性影響，研究包含了三個項目之變溫量測與分析：(1) 動態量測下，利用不同商用元件作為續流二極體，觀察開關元件的切換特性，(2) 元件體二極體及蕭特基二極體之順向電壓，和(3) 動態量測下，不同商用元件作為續流二極體時的反向恢復特性。
經量測後發現使用不同的續流二極體會得到開關元件不同的切換損耗，那是因為體二極體和蕭特基二極體結構的不同，因此會有不同的順向電壓和反向恢復特性。蕭特基二極體相較於體二極體皆會有較低的順向電壓和較佳反向恢復特性，因此在電流流經二極體時，通過蕭特基二極體所產生的功耗也會較低。蕭特基二極體較低的順向電壓也可以使金氧半場效電晶體內建蕭特基二極體元件，使得電流主要通過其內建的蕭特基二極體而非體二極體，因此當電流流過時會有較低的功耗，但會受到金氧半場效電晶體的輸出電容以及內建蕭特基二極體接面電容的影響，所以在室溫時反向恢復特性的部分較不會有明顯的改善，不過在高溫時即可展現出其蕭特基二極體的優勢。在高溫環境中，也可以觀察到蕭特基二極體有較穩定的反向恢復特性，其反向恢復特性不會隨著溫度上升而有劣化的趨勢，因此在高溫環境中使用蕭特基二極體作為續流二極體在半橋電路中會有較低的開啟切換損耗。
本研究也有利用Silvaco TCAD模擬軟體觀察體二極體在不同溫度下造成順向電壓以及反向恢復特性變化的機制原因，發現溫度上升會使內建電壓降低，使二極體更容易導通，並且也會使少數載子數量增加，使反向恢復特性劣化。
;The dynamic measurement of the devices employs the double pulse test (DPT). The primary operating modes for double pulse test include resistive load and inductive load. In this study, the dynamic measurements use the inductive load mode. In this mode, apart from the device under test (DUT) as the switching device, an additional freewheeling diode is required to provide a current path when the DUT is turned off. The reverse recovery characteristics of this freewheeling diode will affect the switching losses when the DUT turns on.
This study uses 1200 V commercial devices with Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) structure, specifically the Cree C2M0080120D, Infineon AIMW120R060M1H, and Toshiba TW060N120C, as well as 1200 V commercial devices with SiC Schottky Barrier Diode (SBD) structure, specifically the Infineon IDW30G120C5B and Rohm SCS230KE2HR, for use as the freewheeling diodes investigation including three types of measurements and analysis, (1) the switching characteristics of the switching device, (2) the forward characteristics of the body diodes and SBDs, (3) the reverse recovery characteristics of different commercial devices when they are used as freewheeling diodes.
It was found that using different freewheeling diodes results in different switching losses for the switching device. This is due to the structural differences between body diodes and SBDs, leading to different reverse recovery characteristics and forward voltage. SBDs generally exhibit lower reverse recovery and forward voltage compared to body diodes. Consequently, when current flows through the freewheeling diode, the power loss through the Schottky barrier diode is lower. The lower forward voltage of SBDs also allows current to pass through the built-in Schottky barrier diode of the MOSFET rather than the body diode, resulting in lower power loss when current flows. However, due to the influence of the MOSFET’s output capacitance and the junction capacitance of the built-in Schottky barrier diode, the reverse recovery characteristics at room temperature do not show significant improvement, but the advantages of the Schottky barrier diode become apparent at high temperatures. SBDs exhibit more stable reverse recovery characteristics, which do not deteriorate with increasing temperature. Therefore, using SBDs as freewheeling diodes in half-bridge circuits results in lower turn-on switching losses at high temperatures.
This study also uses Silvaco TCAD simulation software to observe the mechanisms behind the changes in forward voltage and reverse recovery characteristics of body diodes at different temperatures. It was found that increasing temperature lowers the built-in voltage, making the diode easier to turn on, and increases the number of minority carriers, thereby deteriorating the reverse recovery characteristics. |
