Time Saving Averaging Algorithm for Transient Thermal Analyses over Deterministic Pulse Superposition

Transient thermal analysis (TTA) with the measurement of the single pulse thermal impedance (Z th (t)) is a standard method to verify the thermal integrity of power semiconductors modules. For best evaluation of measured data, the signal to noise ratio (SNR) should be as high as possible. Especially in the early time domain, it is difficult to achieve high SNR because of the required high bandwidth. Most common way to increase SNR is averaging over several TTA measurement repetitions. Since the semiconductor module therefore has to reach thermal equilibrium, this solution is very time consuming. This paper introduces a new averaging algorithm for TTA, wherein several short deterministic pulses are applied to the semiconductor before standard TTA. Over superposition, the influence of the previous pulses is removed from all short pulses and averaging is possible without reaching thermal equilibrium. Result is a standard single pulse Z th (t) and not a duty cycle form of it. The algorithm is tested by simulations and experimentally using automotive LEDs to verify feasibility and demonstrate benefit. Thereby a SNR increase equivalent to 33 repetitions in standard TTA was reached.