High-Precision In Situ Inductor Loss Evaluation for DC–DC Converters Based on Gain–Phase Frequency Characteristics Correction in Voltage/Current Measurement Systems

Abstract

Accurate in situ evaluation of inductor losses in operating DC–DC converters is hindered by frequency-dependent gain and phase errors in practical voltage and current probes, especially when the voltage–current phase approaches 90° in a low-loss inductor. This article presents a frequency-domain gain–phase correction method based on vector network analyzer (VNA) characterization of commercially available probes. The proposed approach is based on the same fundamental principle as the cross-power method and enables high-accuracy loss evaluation using general-purpose oscilloscopes and probe systems during actual converter operation. Gain–phase characteristics are measured for high-voltage differential probes, AC/DC current probes, and optically isolated probes. Applying the derived correction to harmonic components measured in a 100-kHz, 450-W boost converter reduces the discrepancy between different probe combinations from approximately 20 W to below 0.2 W. The results demonstrate that frequency-dependent correction is essential for reliable in situ magnetic loss evaluation using the standard measurement equipment.