Thermal Resistance and Capacitance Characteristics of A 4-in-1 Integrated Power Control Unit (PCU) Module for Hybrid Electrical Vehicle (HEV)

In this work, a 4-in-1 integrated PCU module was developed for the application of hybrid electrical vehicles. It realized the integration of power dies, direct current bus capacitors, current flow sensors and liquid-cooler in physical structure, and the integration of the boost circuit, power generator, motor drives and a multiplexing charger in functional units of power converter. The thermal resistance and capacitance (RC) characteristics for the power switch dies were studied and compared by experiments. It has been revealed that the difference of the RC characteristics among different power converter units depends on the types and the parallel number of power switch dies, while the difference of the RC characteristics between the upper-side and lower-side within a single power converter unit is attributed to the distinct spacing between the paralleled power switch dies and layout design of the upper-copper-layer of the direct bonding copper (DBC). Based on this unique RC characteristics of the developed 4-in-1 integrated PCU module and the power loss for the current operating conditions, the volume flow rate of the coolant for the PCU module has been optimized by simulations. This approach could minimize the risk of local overheating of the power dies in the module which is particularly important for the high-integration design of the developed PCU module.