钙钛矿材料由于具有结构稳定、易于获取、成本低廉和易于合成等优点,在发光二极管、激光器和太阳能电池等光电器件领域具有广阔的应用前景。目前,部分适合UV-LED应用的钙钛矿具有结构不稳定性。为了寻找结构稳定的钙钛矿,此项研究利用...钙钛矿材料由于具有结构稳定、易于获取、成本低廉和易于合成等优点,在发光二极管、激光器和太阳能电池等光电器件领域具有广阔的应用前景。目前,部分适合UV-LED应用的钙钛矿具有结构不稳定性。为了寻找结构稳定的钙钛矿,此项研究利用第一性原理对无铅双钙钛矿Cs_(2)NaScX_(6)(X=Cl,Br,I)的电子及光学性质进行了理论计算。计算结果表明:Cs_(2)NaScX_(6)(X=Cl,Br,I)为直接带隙半导体,带隙值分别为5.545 e V(Cl)、4.549 eV(Br)和3.408 eV(I),Cs_(2)NaScI_(6)在紫外光范围内具有较强的光吸收。本研究内容为无铅A_(2)B^(I)B^(III)X_(6)型双钙钛矿成为UV-LED的候选材料提供理论支持。展开更多
In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on out...In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.展开更多
文摘钙钛矿材料由于具有结构稳定、易于获取、成本低廉和易于合成等优点,在发光二极管、激光器和太阳能电池等光电器件领域具有广阔的应用前景。目前,部分适合UV-LED应用的钙钛矿具有结构不稳定性。为了寻找结构稳定的钙钛矿,此项研究利用第一性原理对无铅双钙钛矿Cs_(2)NaScX_(6)(X=Cl,Br,I)的电子及光学性质进行了理论计算。计算结果表明:Cs_(2)NaScX_(6)(X=Cl,Br,I)为直接带隙半导体,带隙值分别为5.545 e V(Cl)、4.549 eV(Br)和3.408 eV(I),Cs_(2)NaScI_(6)在紫外光范围内具有较强的光吸收。本研究内容为无铅A_(2)B^(I)B^(III)X_(6)型双钙钛矿成为UV-LED的候选材料提供理论支持。
文摘In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (C<sub>o,tr</sub>) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low C<sub>o,tr</sub> operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.