Calibration-Free Calorimeter for Sensitive Loss Measurements: Case of High-Frequency Inductors

Abstract

Wide-band-gap technologies enable ultra-high efficiencies in high-frequency power conversion. However, inadequate accuracies in electrical measurements could lead to spurious efficiency measurements, even above 100%. Furthermore, bandwidth limitations, particularly for current probing, delay mismatches between current and voltage probes, loading effects and electromagnetic interferences make electrical techniques inappropriate for measuring extremely-low losses in switches with high dv/dt and di/dt values and magnetic components with high-frequency excitations. Calorimetric methods overcome this issue by a direct loss measurement through the generated heat. Nevertheless, limited ranges and accuracies of existing systems hinder their application in sensitive measurements. Moreover, time-consuming calibrations with extensive data processing impede rapid design assessments. In this work, we further investigate a previously proposed closedtype double-chamber calorimeter and present its high accuracy for the evaluation of low levels of losses in high-frequency power inductors. The system provides adjustable cooling and can measure losses as low as 500 mW, enabling evaluation of highperformance power converters and their components with no dependencies on the geometries of the evaluated devices/systems.