Online Health Monitoring in Power Modules for Inverter Topologies using Isolated Parameter Acquisition

This work presents a versatile acquisition method and hardware to the simultaneous measurement of several electrical parameters in power transistors employed in switched-mode converters. The setup takes into account that the reference potentials vary drastically and dynamically in bridge inverter circuits, depending on the switching state. Accurate acquisition of several electrical parameters of the device, such as the threshold voltage and the on-state resistance, is employed online by converting the measurements from analog to their corresponding digital values close to the transistors. The implementation of a differential transmission based on a 10Mbps asynchronous protocol and a bus system ensures a robust and performant relaying of the measurement data. Measurement results show that the proposed setup is capable of updating a supervisory system of new parameter values efficiently within one PWM cycle to allow an online adjustment and intervention in case of abnormalities. Furthermore, an example AC power cycling test shows how the quasi threshold voltage and on-state voltage varies within one cycle of 5s. Both show an expected change according to their temperature sensitivity in literature.