Thermal characterization of power transistors

A New Technique for Thermal Resistance Measurement in Power Electron Devices

“…Due to the relatively slow dynamics of thermal phenomena, the power device exhibits a very different small-signal behavior when considering frequencies well below (i.e., nearly dc) and well above (e.g., 1 kHz) the cutoff frequency of thermal phenomena [6]. Since the proposed approach is based on this important difference, the small-signal resistances at the two outlined frequencies are now computed according to (1). These two different resistances will be referred to in the following as and , respectively.…”

“…In this case, can be interpreted as the average temperature of the MOSFET channel. Clearly, (9) may be treated analogously to (1), and all the theoretical developments for the single port device may be repeated for the two-port device by simply replacing , with the voltage and current at the output port of the power transistor. Thus, (8) can be directly used for the evaluation of the thermal resistance of power transistors.…”

“…In this case, an electrical temperature sensitive parameter (TSP) of the device, such as the on-voltage or the inverse current of a diode, is typically used as a built-in temperature sensor [1]. Two types of TSP-based methods may be defined: continuous and switched (or pulsed) methods.…”

“…If the power switching and the TSP measurement times are sufficiently close to each other (typically s), the junction temperature does not change, and its value is identified on the basis of the TSP measurement under the same device operating condition used for calibration. Then, the thermal resistance is simply obtained [1] as . Slightly different procedures are also possible by considering pulsed operating conditions instead of switched ones [1], [2].…”

“…Then, the thermal resistance is simply obtained [1] as . Slightly different procedures are also possible by considering pulsed operating conditions instead of switched ones [1], [2]. Clearly, both these kinds of measurements require relatively simple but special-purpose instrumentation with switched or pulsed measurement capabilities.…”