A compact transient electrothermal model for integrated power systems: Automotive application

The paper is about a so-called ¿diffusive representation¿, a new modeling dynamic systems method and its application to efficient transient thermal modeling of multichip power module taking into account thermal coupling effects. Compact thermal models are required for many analyses during the design of power systems. Generally a RC-ladder model is used and analytical expressions enable to quantify R and C values. Unfortunately the trade-off between complexity, convergence and accuracy is hard to settle. Diffusive approximation of the heat law equation offers an alternative representation. The compact thermal model is a state space model. Parameters identification procedures are given and are validated. The method is applied on an inverter leg, a 400A MOSFET power module manufactured by VALEO for starter-alternator system. Electrothermal measurements have been achieved to develop an electrical model with thermo-sensitive parameters of the MOSFET dies. Electro-thermal measurements and 3D Finite Element thermal simulations have been performed for validations. A compact diffusive model comes as a state space model and may be easily implemented in a ¿circuit¿ simulator.