Improving DC superimposition characteristics of powder cores by applying coupled inductors in multi‐phase boost converter

Abstract

In applications where DC current is superimposed, such as inductors for non‐isolated DC‐DC converters, powder core can be considered as an attractive solution owing to its superior features such as: high saturation flux density, high Curie temperature, and soft‐saturation property. However, in powder cores, a drop of inductance appears prominently due to DC superimposition characteristics. This feature is not a desirable characteristic because it leads to an increase in the inductor ripple current under heavy load, which complicates the thermal design of power semiconductors and capacitors. This paper verifies the improvement of DC superimposition characteristics of powder cores by applying coupled inductors. First, the effect of coupled inductors on the improvement of DC superimposition characteristics is experimentally verified. Second, a measurement method for the DC superimposition characteristics of coupled inductor is proposed. Then, a magnetic circuit model is built using the measurement results. Finally, a coupled analysis of magnetic and electric circuits is performed, and it is confirmed that lower magnetic field operation can be realized by coupled inductors even under heavy load conditions. It has been proven that coupled inductors are effective in improving the DC superposition characteristics of the powder cores.

A Review of Tunable Inductors for Power Electronics: Techniques and Applications

“…The piezoelectric material will therefore experience compression upon the application of a positive electric field, which will be translated into tensile stress in the ferromagnetic material as if the ferromagnetic material is being dragged downward. Figures 25,27,and 29 provide examples that fit into this explanation. However, with the same assumptions, if the shape is two rings placed inside each other such as in Fig.…”

“…𝐵𝐵 𝑠𝑠𝑠𝑠𝑠𝑠 is typically a constant that depends on the magnetic core material; it is the maximum that cannot be surpassed and is considered the upper limit that the peak flux density produced in the magnetic core should not exceed when designing magnetic components [1]. The saturation flux density of the most common soft magnetic materials is shown in Table I, and it is evident that the iron powder cores have a high saturation flux density and are much superior to ferrite cores, despite the fact that their relative permeability is much lower (𝜇𝜇 𝑟𝑟 < 200) than that of ferrite cores [28,29].…”

“…1, and there may be more than one gap distributed along the iron core. While, in powder cores, the air gap is uniformly distributed throughout the material, and these air gaps are created using a non-ferromagnetic material, insulating layer, that is being used to control the permeability of the core [2,[29][30][31][32].…”