Downsizing Design of Powdered Iron Core Inductor Based on Variable-Frequency Modulation Targeted at Harmonics Suppression

Powdered iron core inductor excels in high power applications but perform a noticeable non-linear saturating feature. This paper assesses this feature in terms of the growth caused on current high-frequency harmonics. A frequency-domain method based on signal composition is formulated to predict the current spectrum considering the non-linear feature of inductors. Then a variable frequency modulation strategy is proposed to eliminate the effect of the saturation, based on which the power converter is able to adopt smaller inductors while maintaining a low level of harmonics. Consequently, the power density can be improved. This predictive method is verified on a totem-pole rectifier prototype. Furthermore, with the proposed modulation strategy, the total harmonics distortion is reduced by 0.69%, superior to the case of expanding the inductor size to three times of original.