Design and Implementation of an Air-Cored Fly-back Converter

This paper proposes a miniaturized, light weight design of a fly-back converter based on air cored transformer, suitable for various consumer electronics applications. A method to achieve higher coupling factor in the air-core transformer is also proposed and analyzed. Simulation of the air-core transformer is carried out using ANSYS MAXWELL tool and the design is validated using FEA analysis. A coupling factor of 0.923 between primary and secondary winding of the air-cored transformer is achieved using the proposed method. A fly-back converter is implemented using the air-core transformer and the experimental prototype of the converter is realized using a four layer PCB. Steady state operation of the converter with a switching frequency of 1 MHz is verified using the experimental prototype.

I. Introduction

Use of high-speed Mosfets and wide band gap devices, e.g., GaN HEMTs, results in DC-DC power converters with smaller value of inductance [1]–[3]. As the inductance is smaller, using air-core seems feasible for this type of application. In stand-alone applications, where EMI is less of an issue, magnetic components with air-core can be quite useful. There are several advantages of using air-core magnetics in power converters including reduction in cost and weight, non-existence of magnetic saturation, iron loss, non-linearity of inductor operation, etc. Most of the available research has focused on design of air-core magnetics (inductor/transformer) as a method to miniaturize a converter design [4]–[6]. However, places where procuring magnetic cores is an issue or is expensive, this type of design will be quite handy for certain application sectors, like LED lights, charging, auxiliary power supplies in electric drives, Consumer Electronic Devices (CED), and Point of Load Converters (POL) in non-critical applications, etc.