LLC resonant converters are widely applied in on-board power supplies owing to their high power density, high efficiency and small size, and their reliability is critical to the driving safety and passenger experiences. However, the complicated working conditions and harsh environment under which vehicles operate have become a huge challenge to power devices. When a switch failure occurs, the resonant converter cannot maintain a stable output voltage while operating at a resonant point, and both efficiency and output capability of the system will decrease substantially. To make the converter more compatible with fault occasions, an improved LLC topology and its control strategy are proposed in this paper, which can ensure that the output voltage remains unaffected when a switch failure occurs and the converter operates near the resonant frequency. Additionally, an optimized Burst control strategy is designed to suppress the overvoltage of the resonant capacitor during the fault tolerance transition and guarantee a smooth fault tolerance process. Finally, simulation and experimental results verified the effectiveness of the proposed method.

Owing to its advantages including lower switching stress, harmonic components and a better anti-interference capability, the diode neutral point clamped (NPC) three-level inverter has become a prominent topology for DC-AC converters used in new energy fields such as photovoltaic and energy storage. The NPC three-level insulated gate bipolar transistor(IGBT) power semiconductor module which is widely used in high-power applications is studied. The commutation circuit in the NPC three-level power module is analyzed, and a precise simulation and evaluation method for the corresponding parasitic parameters is given. According to the principle of minimizing the parasitic parameters of the commutation circuit, a dynamic characteristic test circuit suitable for the NPC three-level power semiconductor module is designed. Based on the commutation circuit and the operating principle of circuit, a drive circuit for the NPC three-level power module is designed, and a driving scheme that enhances drive current, prevents shoot-through and allows for adjustable dead time is formulated. Finally, through dynamic testing of the NPC three-level IGBT module, a comprehensive assessment of the dynamic loss in power devices under various operating conditions is conducted.

Press-pack IGBT power devices are the core component in the new power system application equipment, and health management can improve their service lifetime and operational reliability, thus guaranteeing the safety and stability of new power systems. First, the package structure and main failure modes of press-pack IGBT devices are introduced. Second, the existing health condition monitoring methods are classified and analyzed according to different types of characteristic parameters. Third, the principles and characteristics of the existing lifetime prediction methods for press-pack IGBTs are summarized. Finally, a comprehensive comparative analysis of the existing health management technologies is performed, and the problems in the health management methods for press-pack IGBTs which need to be further studied and the development trends in the future are pointed out.

With the widespread applications of insulated gate bipolar transistors (IGBTs) in power electronic systems, the accurate acquisition of junction temperature which affects their reliability has become crucial. However, one of the main forms of module failure is the aging of the solder layer, which can have a significant impact on the junction temperature. To accurately estimate the junction temperature, the advantages of two traditional thermal network models (i.e., Cauer and Foster) are combined in this paper, and an interface method for the two models is studied, so that the combination is completed. The aging of the chip solder layer is taken into account, and a hybrid thermal network model is proposed. Finally, through the comparison of finite element simulation and experimental test with the calculation results of the hybrid thermal network model, it is verified that the hybrid thermal network model can achieve an accurate junction temperature estimation, providing a basis for monitoring the operating status of the module.

With the applications of an ultra-wideband pulse signal system in many important fields such as the intelligent sensing technology for new energy automobile, the research and development of high-amplitude and fast-front pulse sources has been widely studied. To meet the demand of an ultrafast power semiconductor switch in nanosecond front pulses, the terminal failure mechanism of avalanche bipolar junction transistor in voltage ramp triggering mode is studied in this paper. The static characteristics of a simulation model are compared with those of a sample device, and the dynamic switching characteristics of the sample device were tested. On the basis of a successful device with a nanosecond switching speed, its failure phenomenon in voltage ramp triggering mode was analyzed.

To study the degradation mechanism of silicon carbide metal-oxide-semiconductor field effect transistors (SiC MOSFETs) under dynamic drain-source stress, a dynamic reverse bias test platform with an adjustable dVds/dt capability up to 80 V/ns was developed. A dynamic high-temperature reverse bias test of commercial SiC MOSFET was carried out, and the effect of dynamic drain-source stress with a high voltage change rate on the electrical characteristics of SiC MOSFET was discussed. Experimental results show that the threshold voltage and forward conduction voltage of the bulk diode increased, indicating that the gate oxygen layer and the bulk diode above the JFET region of the device may be degraded. Sentaurus TCAD was used to analyze the weak position of plane-gate SiC MOSFET under high drain-source voltage and a high voltage change rate, and hole traps were set at the gate oxygen layer junction and the body diode region to simulate the effect of dynamic high-temperature reverse bias on the dynamic and static parameters of SiC MOSFET.

Compared with that in a Si device, the area of near interface oxide traps in a SiC MOSFET is wider, and the corresponding density of traps is two orders of magnitude higher. A lot of traps which are continuously capturing or releasing charges will cause the threshold voltage (Vt) to fluctuate with time, leading to the difficulty in accurately and repeatedly measuring the value of Vith. In the standard method, the value of Vith is measured using a preprocessing method to ensure the consistence in measuring the trap charge state in each time. However, the preprocessed trap state which is affected by drain-source voltages is not taken into account in the standard method, which will bring errors to the Vth test. Aimed at this problem, the transfer curves under the influences of different drain-source voltage pulses were measured at first, which show the effects of different drain-source voltages on Vth. Second, the influence of drain-source voltage on the trap charge state was analyzed based on the transient current method, thus clarifying the mechanism of the influence of drain-source voltage on traps. Finally, the influences of different drain-source voltages on Vith measurement were com-pared. Results indicate that the drain-source voltage affects the positive and negative electric field between the gate and drain, thereby affecting the trap charge state and causing the Vith drift. It is suggested that a smaller drain-source voltage should be used when measuring Vith to improve the measurement accuracy and reduce errors caused by testing factors in reliability experiments.

The advancements in research on automotive power device packaging have significantly improved the dynamic performance and driving range of electric vehicles, making them more efficient and reliable. With the continuous optimization of automotive power device packaging, the electric vehicle industry is expected to embrace a broader market prospect and development space. In recent years, power device packaging modeling, packaging structure and optimization, thermal management and junction temperature monitoring, gate drive and applications, reliability analysis, and online monitoring have become current research hotspots and have received sustained attention from both the academic and industrial sectors. To promote discussions on the challenges and hot issues related to automotive power devices packaging and their applications, a special issue titled "High Reliability Power Device Packaging and Assistant Technology in EV Application" has been launched in the Journal of Power Supply.

Press-pack IGBT power devices are one of the core components in new power system application equipment. Due to the complex working environment and variable working conditions of power equipment, the fatigue failure of power devices will be caused over time. To ensure the safe and stable operation of key equipment in power systems, it is necessary to assess the remaining lifetime of press-pack IGBT devices, thereby timely taking appropriate actions before a device failure occurs. First, a multi-physics field model of press-pack IGBT devices is established, and the mechanical parameters affecting their aging process are analyzed. Based on the analysis results, a suitable model for press-pack IGBTs is selected from the existing lifetime prediction models, and a lifetime assessment software applicable to press-pack IGBTs is developed. Finally, a case study is conducted based on the developed lifetime assessment software, and the assessment result of devices is obtained, providing guidance for the applications of devices.

Gate oxide degradation is a key reliability issue that limits the widespread applications of silicon carbide metal-oxide-semiconductor field-effect transistors(SiC MOSFETs), and online monitoring is an important means to improve the reliability of SiC MOSFETs as it can obtain the gate-oxide health status in real time. In this paper, an online monitoring method for SiC MOSFET gate-oxide health status based on gate reference voltage is proposed. The basic principle of using the gate reference voltage to monitor the gate-oxide health status is introduced in detail, and a gate reference voltage online extraction circuit is also put forward. The designed extraction circuit was verified by pulse tests, indicating that it can achieve online extraction. In addition, aging tests were conducted, and results verified that the proposed method can effectively monitor the gate oxide health status. The designed circuit can be integrated into gate driver without significantly increasing the system complexity.