Power electronics cooling effectiveness versus thermal inertia

Today, the popularity of power electronics integration is increasing. Despite the prospect of fully integrated module, including features like driving and control electronics, protection, power integration has not taken-off for medium to high power electronics applications. Manufacturing issues such as yield, reliability and return-on-investment for a new fabrication line are the major blocking points. As a first step toward integrated modules, integration of the cooling system appears realistic and cost effective. Increasing the cooling effectiveness could double the output current of an inverter while using the same amount of silicon. On the other hand, integrated cooling leads to small thermal inertia, which can generate high temperature variation under load cycling condition. This paper highlights the relationship between cooling effectiveness and thermal inertia. Typical performances of several cooling systems are compared under load cycling condition to explain how to take into account the variation of the losses in the choice of a cooling technique at the design stage. As an example, a standard liquid cooled plate performed similar to an integrated microchannel network for specific load variation frequencies.