Remaining useful lifetime prediction and extension of Si power devices have been studied extensively. Silicon carbide (SiC) power devices have been developed and commercialized. Specifically, SiC mosfet s have been utilized for the next generation high-voltage, high-power converters with smaller size and higher efficiency, covering various mainstream applications, including photovoltaic systems, electric vehicles, solid-state transformers, and more electric ships and airplanes. However, the SiC-based devices have different failure modes and mechanisms compared with Si counterparts. Therefore, a comprehensive review is critical to develop accurate lifetime prediction and extension strategies for SiC power converter systems. The SiC power device component-level failure modes and mechanisms are first investigated. Different accelerated lifetime tests and component-level lifetime models are then compared. Power converter system-level offline lifetime modeling techniques and software tools are further summarized. Besides, the SiC power converter condition monitoring strategies and health indicators are surveyed. The online measurement challenges are also studied. Furthermore, the system-level lifetime extension strategies are reviewed. By integrating device physics, statistical modeling, reliability engineering, and mechanical engineering with power electronics, this article is intended to provide a comprehensive overview, address existing challenges, and unfold new research opportunities regarding the SiC power converter real-time lifetime prediction and extension.

Overview of Real-Time Lifetime Prediction and Extension for SiC Power Converters

A method for an on-line junction temperature measurement is introduced. The circuit allows the calibration of a real-time thermal model of a power MOSFET. A regular calibration of the real-time model provides an accurate thermal flux model over the lifetime of the power MOSFET. The measurement of threshold voltage is used to determine the device temperature. The paper presents the on-line measurement method, the circuit and test results.

On-line monitoring of the mosfet device junction temperature by computation of the threshold voltage

Within a power converter, multiple currents are usually measured for control, protection, and/or monitoring. They are therefore important sources of information, which must unquestionably be measured accurately to maintain continuous and reliable operation of the power converter. Accurate current measurement has however become tougher with the introduction of wide band-gap (WBG) devices with switching frequency tending toward the megahertz (MHz) range. Because of that, the installed current sensors must have a significantly widened bandwidth. Moreover, they must be nonintrusive and compact, in order not to degrade fast switching characteristics and high power density of the WBG converter. Presently, these features are not collectively obtainable from existing commercial current sensors. Consequently, many new current sensing techniques have surfaced in the literature for usage with the more demanding MHz power converter. These new techniques, some classical techniques, and their hybrid integrations are now reviewed, after overviewing functionalities made possible by current sensors in a power converter. Last but importantly, some future developmental trends aimed at matching MHz current sensors with MHz power converters are described, before concluding the article.

https://ieeexplore.ieee.org/ielx7/63/9714885/09658157.pdf

A Review of Megahertz Current Sensors for Megahertz Power Converters

Silicon carbide metal–oxide–semiconductor field-effect transistor (SiC MOSFET) has become a promising device due to its excellent material properties. Junction temperature is an important parameter and a significant health index. In this article, drain current during turn-on transient is taken as the thermo-sensitive electrical parameter (TSEP) to monitor the junction temperature of SiC MOSFET. Based on the physical properties of wide bandgap semiconductor materials, the switching behaviors of SiC MOSFET and the variation of drain current with temperature were studied. The influence of temperature dependence of threshold voltage and carrier mobility on drain current is analyzed. It is proven that the drain current has a positive temperature coefficient during turn-on transient. Finally, the validity of the proposed method is verified by the theoretical analysis and experiments.

Estimating Junction Temperature of SiC MOSFET Using Its Drain Current During Turn-On Transient

Maintaining the operating junction temperature of a SiC Power MOSFET within a safe and tolerable range is crucial not only for safety reasons, but also for reliable operation, as thermal transient is one of the major stressors that threaten a device’s life span. Conventional methods use thermal sensors for temperature monitoring. However, these sensors require extra space, and the measurement accuracy is affected by their position. Besides, they are unable to track the transient temperature variation owing to relatively slow response time. This paper proposes a new temperature sensor-less method to estimate the junction temperature of SiC power MOSFETs by measuring the device’s turn-on saturation current (ID,sat). The device’s square root of the saturation current ( √ ID,sat) and threshold voltage (Vth) can be extracted and adopted as junction temperature estimators. Compared to the threshold voltage, the square root of the saturation current has the advantage of a shorter test time. The feasibility of this temperature estimation method has been experimentally verified. The results suggest that the proposed method can be used as an alternative for effective online junction temperature monitoring.

/pdf/a-method-of-junction-temperature-estimation-for-sic-power-5bgu3jfr4r.pdf

A Method of Junction Temperature Estimation for SiC Power MOSFETs via Turn-on Saturation Current Measurement

Keeping the operating junction temperature of a SiC MOSFET within safe and tolerable range is vital. Besides safety reasons, it also extends the device’s life span as thermal transient is identified as one of the major stressor for device aging. Conventional methods use thermal sensors for temperature monitoring but these sensors require extra space and are unable to track transient temperature variation due to relatively slow response time. This paper proposes a new temperature sensor-less method to estimate junction temperature by using the device’s square root of saturation current $(\sqrt {{I_D}} )$ and threshold voltage (V th ) for temperature monitoring. Both parameters can be extracted from device’s saturation current and the experimental results have demonstrated the feasibility of this temperature estimation method. The proposed method looks promising as an alternative for future electronic health monitoring (EHM) system.

A Method for Junction Temperature Estimation Utilizing Turn-on Saturation Current for SiC MOSFET

The reliability of power converters has become a major design concern especially for those mission-critical industrial and aerospace applications required to operate in a harsh environment There is a need for real-time monitoring techniques that are capable of tracking health status to give an alert signal before a disastrous system failure and furthermore make the early failure prediction due to long-term wear-out possible This paper presents a real-time isolated voltage monitoring unit (IVMU) that monitors on-state voltage of a semiconductor power switch accurately It can be integrated with off-the-shelf power converter to perform real-time status monitoring The design has been validated with double-pulse testing and on a H-bridge inverter that utilize SiC power switches

Real-time integratable isolated voltage monitoring unit of semiconductor power switch to improve power converter reliability

Understanding the causes of a power device’s defect plays a crucial role in failure and reliability analyses, and hence, the need of health diagnosis. Health diagnosis involves the measurement of predefined electrical parameters of a power device under its usual operating condition and the analyses of their deviations from their norms. Instead of the conventional direct measurements of voltage and current waveforms in time domain, this paper proposes a nonintrusive measurement method that measures the ON-state impedance of a power device in frequency domain. The proposed method eliminates direct electrical contact with the device-under-test, and it has the ability to detect the deviation of the ON-state impedance from its norm for health diagnosis purpose.

/pdf/offline-health-diagnosis-of-power-device-based-on-1bsxrmoh1l.pdf

Hui-Chen Yang

Papers

A Method for Junction Temperature Estimation Utilizing Turn-on Saturation Current for SiC MOSFET

A Method of Junction Temperature Estimation for SiC Power MOSFETs via Turn-on Saturation Current Measurement

Real-time integratable isolated voltage monitoring unit of semiconductor power switch to improve power converter reliability

Offline Health Diagnosis of Power Device Based on Nonintrusive Inductively Coupled Approach