Applied Thermal Engineering, Volume 70, Issue 1, 5 September 2014, Pages 593-599.
Po-Chien Chou, Stone Cheng, Szu-Hao Chen.
Dept. of Mechanical Eng., National Chiao-Tung University, Hsinchu 300, Taiwan.
Abstract
This work presents an extensive thermal characterization of a single discrete GaN high-electron-mobility transistor (HEMT) device when operated in parallel at temperatures of 25 °C–175 °C. The maximum drain current (ID max), on-resistance (RON), pinch-off voltage (VP) and peak transconductance (gm) at various chamber temperatures are measured and correlations among these parameters studied. Understanding the dependence of key transistor parameters on temperature is crucial to inhibiting the generation of hot spots and the equalization of currents in the parallel operation of HEMTs. A detailed analysis of the current imbalance between two parallel HEMT cells and its consequential effect on the junction temperature are also presented. The results from variations in the characteristics of the parallel-connected devices further verify that the thermal stability and switching behavior of these cells are balanced. Two parallel HEMT cells are operated at a safe working distance from thermal runaway to prevent destruction of the hottest cell.
ACKNOWLEDGEMENTS
This work was supported by the MoEA project 101-EC-17-A-05-S1-154, and MoST project 102-2221-E-009 -074, Taiwan, R.O.C.. The authors would like to thank Prof. Edward Yi Chang of NCTU for supporting GaN devices, and Edward Kuo of Advanced Precision Testing Technology CO., Ltd for their very helpful suggestions and technical support.
Figure Legend: Operating waveforms of two parallel HEMTs with a common gate drive.