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Considering potential applications related to superconductivity and aerospace (typically less than 100 K), in this article, the temperature dependence of silicon carbide (SiC) power diodes is systematically characterized and analyzed over a wide temperature range of 90–478 K, especially focusing on cryogenic temperature. First, the static performance degradation mechanism of SiC diodes is established in an ultrawide temperature range, including forward/reverse I-V characteristics and junction capacitance (Cj) characteristics. Second, the reverse recovery characteristics are achieved, including peak reverse recovery current (Irm), reverse recovery charge (Qrr), and switching energy (Esw), clarifying a clearer internal relationship between reverse recovery and junction temperature. Meanwhile, the aforementioned critical parameters are further analyzed on an electrical scale with normal atmosphere temperature, including switching speed range of 62.3–2054.8 A/μs, load current range of 6–30 A, and dc voltage range of 400–1000 V. Third, based on newly proposed power loss analysis method, the continuous operation performance of SiC diodes is quantified and analyzed in actual cryogenic converters. The excellent temperature dependence indicates that SiC diodes have great superiority for extreme applications. Importantly, SiC mosfet's body diode shows the great potential to operate as a freewheeling diode in the compact converter, especially at cryogenic temperature. [ABSTRACT FROM AUTHOR]

Due to the superior material properties, SiC mosfet is a promising candidate switching device for high power density and high efficiency power conversion system. The robustness of switching device under extreme temperature condition becomes a crucial factor to ensure power conversion system safely and continuously operating. In this paper, the temperature dependence of dynamic performance of 1.2-kV 4H-SiC power mosfets is systematically characterized over such wide temperature range of 90–493 K and compared with 1.2-kV Si IGBT by a layout optimized double pulse tester (DPT). The degradation of dynamic on-resistance related interface traps is analyzed specially and the energy loss caused by degradation is quantified at cryogenic temperatures. Besides, to validate the performance of SiC mosfet under safely and continuously operating conditions for cryogenic temperature application, a hard switched non-isolated dc–dc buck converter is designed and tested to estimate temperature dependence of conversion efficiency under temperature range of 90–290 K. Moreover, the further characterizations are conducted with gate resistance range of 2–20 Ω, load current range of 3–30 A, and converter output current of 5–22.5 A under different switching frequency (up to 150 kHz) to validate high power and high frequency application potential of SiC mosfet. [ABSTRACT FROM AUTHOR]

Conventional switched-mode power supplies have intrinsic instantaneous power pulsation at the switching frequency thus require bulky filters. To improve the power density, this paper proposes a concept named the mixed analog–digital (MAD) which can be applied as dc–dc converters. By inserting an analog voltage component between the load and source, the output voltage naturally has much smaller fluctuation thereby much smaller passive filter is required. Simulations and experiments validate that the proposed MAD concept can be applied as dc–dc converters to significantly increase the power density. [ABSTRACT FROM AUTHOR]