Variable Inductor with Adjustable Air Gaps

This paper presents a variable inductor technique, where the inductance in the resonant network can be changed on line at different operation points. As a result, high efficiency can be achieved in a wide range of voltage inputs and outputs. The proposed variable inductor adjusts inductance by altering the magnetic reluctance of the airgap. In the proposed magnetic structure, an auxiliary core is incorporated along with the main core as part of airgaps. The reluctance of the auxiliary core is controlled by an external current excitation. The control flux in the auxiliary core is perpendicular to the main flux so that they do not interfere with each other. This technique is straightforward to implement and does not disrupt the design of the main inductor, as the B-H curve is fully utilized. Simulation and experimental results demonstrate the effectiveness of the proposed technique.