A Thermal Network Model for Multichip Power Modules Enabling to Characterize the Thermal Coupling Effects

A proper thermal network model (TNM) facilitates the thermal analysis of multichip power modules, and is beneficial to reliability evaluation of power converters. However, many TNMs are struggling to provide accurate thermal analysis while maintaining acceptable computational efficiency. To address this, a TNM based on the Cauer model is proposed in this paper, where the Cauer model is obtained with the assistance of the structure function (SF). Then, the thermal coupling effects in multichip power modules are fully characterized. More specifically, the thermal coupling in the proposed TNM is equivalent to the injected power losses from the specific nodes, and an enumeration method is accordingly used to identify the injected nodes and the injected power losses. Moreover, a discretization approach based on the forward Euler method is implemented to enhance the computational efficiency. Subsequently, the junction temperature of the multichip power module is estimated through the signal-flow graph method. Finally, the proposed TNM uses the typical insulated-gate bipolar transistor (IGBT) modules as a case study, and extensive simulations and experimental tests are conducted to validate the effectiveness of the proposed TNM.