Power electronics regulate and modify the electrical power. They are found in computers, power steering systems, solar cells, and many other technologies. Researchers are trying to improve power electronics by using silicon carbide semiconductors. However, wear defects such as cracks remain problematic. To help researchers improve future device designs, early damage detection in power electronics before a complete failure is required.
In a study recently published in IEEE Transactions on Power Electronics, researchers from Osaka University monitored the propagation of cracks in a silicon carbide Schottsky diode in real time during power cycle tests. The researchers used an analytical technique known as acoustic emission that has not previously been reported for this purpose.
During the power cycle test, the researchers mimicked the device repeatedly turning the device on and off to monitor the resulting damage to the diode over time. An increasing sound emission corresponds to a progressive damage to the aluminum strips attached to the Schottsky diode made of silicon carbide. The researchers correlated the monitored acoustic emission signals with specific stages of equipment damage that eventually led to failure.
“A transducer converts acoustic emission signals into measurable electrical output during power cycle tests,” explains lead author ChanYang Choe. “We observed burst waveforms that correspond to fatigue cracks in the device.”
The traditional way to check if a power supply is damaged is to monitor abnormal increases in forward voltage during power cycle tests. Using the traditional method, the researchers found that the forward voltage increased abruptly, but only when the device almost completely failed. In contrast, the acoustic emission figures were much more sensitive. Instead of an all-or-none response, there were clear trends in noise emission values in power cycle tests.
“In contrast to forward voltage curves, acoustic emission curves show all three stages of crack development,” says senior author Chuantong Chen. “We determined crack initiation, crack propagation and equipment failure and confirmed our interpretations through microscopic imaging.”
Up until now, there has been no sensitive early warning method for detecting fatigue cracks that lead to complete failure of Schottsky diodes made of silicon carbide. The acoustic emission monitoring described here is one such method. In the future, this development will help researchers determine why silicon carbide devices fail and improve future designs in current and advanced technologies.
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Materials provided by Osaka University. Note: the content can be edited by style and length.