Thin type DC/DC converter using a coreless wire transformer

Abstract

A 1OW class thin type D C D C converter is developed which uses a new type coreless wire transformer. The converter is intended for portable equipment use. The coupling factor of the wire transformer is more than 95% at frequencies higher than 1OOkHz. When applied in a 3 output DCDC converter, the converter is only 5 . 5 m thick and has 70% efficiency.

Evaluation of the shielding effects on printed-circuit-board transformers using ferrite plates and copper sheets

“…6, the normal component of the magnetic field intensity in free space is about 19 dB, i.e., 79.4 times, higher than that inside the ferrite plate. Thus, both simulated results and theory described in (3) show that using ferrite plates only is not an effective way to shield the magnetic field generated from the planar transformer.…”

“…In power transfer applications, the PCB transformers have to be shielded to comply with EMC regulations. Investigations of planar transformer shielded with ferrite sheets have been reported [3], [4]. From [4], the energy efficiency of PCB transformer shielded with ferrite sheets can be higher than 90% in Megahertz operating frequency range.…”

Characterization of coreless printed circuit board (PCB) transformers

“…The primary leakage inductance is given by (4) Derivation of mutual inductance, , between two circular tracks with rectangular cross section has been reported by Hurley and Duffy [18] (5) where when when (6) permeability of vacuum; first kind Bessel function of order zero; inner radius of the th circular track; outer radius of the th circular track; height of the th circular track; inner radius of the th circular track; outer radius of the th circular track; height of the th circular track; separation between the circular tracks.…”

“…Equations (1) to (6) indicate that all of the inductive parameters depend on the geometry of the coreless planar transformer. These inductive parameters vary with 1) outermost radius; 2) number of turns; 3) conductor width; 4) lamination thickness; 5) conductor thickness.…”