Dynamic Junction Temperature Evaluation: On-State Voltage Measurement Device vs. IR Thermography

Abstract:
Temperature monitoring of power semiconductors is essential to ensure component reliability and longevity. During the operation of an inverter, this is typically done using infrared thermography or temperature sensors placed nearby the chip. An alternative method utilizes the chip itself as a temperature sensor by exploiting the fact that the on-state voltage is temperature-dependent. Precise measurement of this voltage allows for an accurate evaluation of the chip temperature. During pulsed operation, a specialized measurement circuit, called Isoclipper, is used, which suppresses high switching voltages, allowing high-resolution observation of the conduction voltage. In combination with a detailed calibration and a modified inverter control, a correlation with an IR camera within a range of 3 K can be achieved, as verified through an experimental setup.