Coreless Printed Circuit Board ( Pcb ) Transformers —

© 2000 IEEE. Information contained in this newsletter may be copied without permission provided that the copies are not made or distributed for direct commercial advantage, and the title of the publication and its date appear. A bstract – In this article, the fundamental concept, characteristics and application potentials of coreless printed-circuit-board (PCB) transformers are described. Coreless PCB transformers do not have the limitations associated with magnetic cores, such as the frequency limitation , magnetic saturation and core losses. In addition, they eliminate the manual winding process and its associated problems, including labor cost, reliability problems and difficulties in ensuring transformer quality in the manufacturing process. The parameters of the printed windings can be precisely controlled in modern PCB technology. Because of the drastic reduction in the vertical dimension , coreless PCB transformers can achieve high power density and are suitable for applications in which stringent height requirements for the circuits have to be met. A transformer's power density of 24W/cm 2 has been reported in a power conversion application. When used in an isolation amplifier application, coreless PCB transformers tested so far enable the amplifier to achieve a remarkable linear frequency range of 1MHz, which is almost eight times higher than the frequency range of 120 kHz in existing Integrated-Circuit products. PCB materials offer extremely high isolation voltage, typically from 15kV to 40kV, which is much higher than many other isolation means such as opto-couplers. It is envisaged that coreless PCB transformers can replace traditional core-based transformers in some industrial applications. Their application potentials deserve more attention and exploration. Introduction The discovery of Faraday's law of induction is indisputably a corner stone in electrical and electronic engineering. electric generators and transformers has made electricity a common form of energy in modern society. These days, transformers are commonly used for electrical isolation and energy and/ or signal transfer. Normally, traditional transformers consist of copper wind-ings wound on magnetic cores. The use of magnetic cores in transformers is usually thought to be essential because the magnetic cores, which are made of ferromagnetic materials, provide good conducting paths for the magnetic flux. The core-based transformer concept has not faced much serious challenge in the past, probably because of the fact that most transformer designs were for low-frequency (50 or 60Hz) operations. Even when the operating frequency in many modern power electronics applications (such as switched mode power supplies) was significantly increased to …