This work presents the analysis of a converter based on an LLC resonant output inverter and its optimal design used in induction heating applications. The new optimal design method improves several operating parameters that leads to an optimization of the dimensioning of the components of the converter. Additionally, this converter achieves an output power factor that can be considered optimal since it allows to minimize the reactive power of the resonant circuit components and reduces the rms values of the output current of the inverter and the current of its switching devices in relation to that found in traditional designs. A complete study of the circuit based on classic models is carried out to introduce simple rules for the design of this type of inverter for induction heating applications and to control its output power based on a phase shift system (PS). Since the inverter is made with silicon carbide (SiC) MOSFET transistors, an efficiency greater than 99% is reached. The experimental results were obtained from the test of a 12 kW 20 kHz converter for induction heating application.
GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors.
Wide band gap semiconductors are expected to be the future technology for power semiconductors that can enable the reduction of power consumption in many applications. But, in order to use these materials, it is necessary to study their reliability. Regarding its possible use in radioactive environments, it is essential to know the response of HEMT structures based on GaN under radiation. This paper is focused on the study of the effects of gamma radiation on dynamic performance of commercial GaN HEMTs. A test campaign was performed to detect variations on dynamic on-resistance induced by irradiation, due to the relevance of dynamic resistance behavior in power switching converters. This study demonstrates an increase of the dynamic resistance in MISHEMTs structures when they are under gamma radiation together with a voltage stress in the drain region. This increase takes place especially after a hardswitching transition due to the hot-electron effect that takes place during the switching events and can not only lead to an increase of the power losses, but also a reduction in the life time of the device due to the permanent degradation that could be induced by the hot-electron effect.
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