Discrete Power Semiconductor Losses Versus Junction Temperature Estimation Based on Thermal Impedance Curves

Loss estimation in power semiconductor components is an important research topic for a long time with various methods that have been proposed in the literature. Although these methods have been implemented and allow estimating the losses with satisfactory results, the junction temperature of the component is generally controlled poorly while it influences the losses. This article presents a dynamic calorimetric method used to estimate the losses in power semiconductor devices, taking into account their evolution as a function of the junction temperature. The proposed method is based on the temperature measurement in a metal block fixed under the component. Through a thermal model based on the notion of thermal impedance, the transient temperature measurement in the block allows determining the losses and the junction temperature of the device. In order to size the test bench and determine the robustness of this method with respect to measurement or implementation uncertainties (heat transfer coefficients and thermal conductivity of materials), thermal simulations were performed using the Flotherm software. Due to the presence of noise in the measurements, post signal processing is also necessary. By applying the chosen setting, a corresponding experiment was conducted to verify the proposed method. This experiment showed promising results for both loss and junction temperature determination.