An air-core toroidal transformer is a key passive component to achieve MHz operation of power converters. The stray capacitances of this transformer, determined by its structure, prevent fast switching. It is important to reveal the relationship between the structure and the stray capacitances for the design of this transformer. We measure the magnetic flux density of the fabricated air-core toroidal transformers with the different stray capacitances when they are operated in high-frequency switching conditions. As a result, the oscillation is observed in the measured input current and magnetic flux density. By comparing these transformers, it is found that the stray capacitances caused the oscillations.

Olfaction is expected to provide reality and a sense of immersion in multimedia contents. Therefore, an olfactory display, a gadget to present scents to one or more user(s), has been developed. A wearable olfactory display has advantage from the viewpoint of reducing the odorant diffusion into the atmosphere and is suitable for virtual reality applications. In this study, we developed a portable olfactory display using surface acoustic wave (SAW) device and micropumps. In the experiment using quartz crystal microbalance (QCM) gas sensor, we confirmed that the olfactory display can present the odorant with intended intensity.