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Using the Chip as a Temperature Sensor - The Influence of Steep Lateral Temperature Gradients on the VCE(T)-Measurement
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| Author(s) |
Ralf Schmidt; Uwe Scheuermann |
| Abstract |
During operation steep lateral temperature gradients evolve in IGBT power semiconductor chips. The influence of these
lateral gradients on the measurement of the virtual junction temperature by means of the widely used VCE(T)-method was investigated. In particular we address the question, how the obtained single temperature value is related to the temperature distribution of the chip. A combination of electrical and thermal measurements together with thermal simulations was performed to understand the implicit averaging mechanisms of the VCE(T)-measurement. It is found that the lateral temperature gradient in the chip results in an inhomogeneous sense current distribution during the measurement. This
current distribution is responsible for the formation of the measurement value and its corresponding temperature T*. A
comparison of experimental and simulation results shows that for currently existing IGBTs, T* corresponds to the areaweighted
average of the active chip area. The maximum imbalance in sense current density during the VCE(T)-measurement was determined for maximum load condition on a high performance cooling system to be 150 % and 50 % of the average current density for the central and the corner area of the chip, respectively. Furthermore, the temporal evolution of the temperature profile and its influence on the thermal impedance measurement are discussed. It is shown that the temperature at the chip center evolves with a smaller thermal time constant (i.e., faster evolution) than at the chip corners. |
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| Filesize: | 543.5 KB |
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| Type |
Members Only |
| Date |
Last modified 2011-11-29 by System |
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