In-Operation Junction Temperature Extraction for Cascode GaN Devices Based on Turn-Off Delay

In this article, a method to extract the junction temperature of cascode gallium nitride (GaN) devices based on the turn-off delay is proposed for the first time, together with a possible circuit implementation. We described the method theory at first, which showed good applicability even at low gate-resistor values, allowing avoidance of self-sustained oscillations and extra losses. The circuit implementation has also been presented starting from the design process and ending with a comprehensive experimental campaign. The experimental results show both a good static and dynamic performance and a high repeatability within 0.6 degrees C. The overall obtained accuracy stays within +/- 2 degrees C and the response time is 500 ns, besides, the test results from dc power cycling shows that the accuracy of proposed method will not be affected by aging.