Embedded Flexible Fe–Si–Al Powder Composite Film Inductor for Low Power DC–DC Converters

This paper describes the construction of an embedded flexible inductor using Fe-Si-Al powder composite films with a μ
^r
of 140, and proposes a low-power dc-dc converter using this inductor. The fabricated composite films are composed of mixed 85%Fe-9%Si-6%Al flaked powders, and ethylene propylene diene monomer rubber, which is a terpolymer with rigid polymer structure used in low-power applications. The proposed flexible inductor is simulated using Maxwell three-dimensional tool and measured out by folding the fabricated flexible inductor (to 0°, 45°, 90°, and above 90°). It has also been confirmed that the inductance of a flexible inductor has good linearity at a high frequency of several MHz. To verify its usefulness, the proposed inductor with dimensions of 10 mm × 7 mm × 0.28 mm was applied to a dc-dc boost converter fabricated on a flexible printed circuit board of size 10 mm × 23 mm × 0.16 mm. The output power of the fabricated dc-dc boost converter was 2 W (5 V/400 mA) and the switching frequency was fixed at 1.2 MHz. On testing, the fabricated dc-dc boost converter recorded a maximum efficiency of 84%. Additionally, the flexibility of the fabricated embedded flexible inductor was verified by folding it (to 0°, 45°, 90°, and above 90°). Thus, the excellent flexibility of the fabricated embedded flexible inductor was proved.