Inductor Core Loss Estimation and Comparison of Modulations Achieving ZVS for High-Frequency DCM Grid-tied Inverters

This paper discusses three modulation schemes that can achieve zero-voltage switching (ZVS) and improve the efficiency of discontinuous current mode (DCM) inverters with MHz operation. Bipolar, unipolar and trapezium current modulations (TPCM) are evaluated. The DCM inverter can achieve zero-voltage switching (ZVS) by discretely adjusting the duration of the zero current period, in which the voltage across the devices is oscillating. This paper proposes to estimate the inductor core loss for DCM-operated inverters with the off-time discrete control by diving the inductor current to sinusoidal excitation parts and square excitation parts. The inductor core loss is separately calculated for two kinds of excitations by Steinmetz equation and an improved generalized Steinmetz equation, respectively. A 400-W single-phase full-bridge inverter using GaN-HEMTs and inductors with carbonyl iron powder core was fabricated to validate the analysis. The comparison between the estimated and measured losses confirms that the core loss can be discussed by the results of the proposed estimation method.