Y. Midorikawa

Thin film transformer and its analysis by integral equation method

We propose a thin film transformer for small electronic devices, and apply the integral equation method to analyze this transformer. Both the primary and secondary coils of the film transformer are arranged coaxially on the layer and multiply laminated. The operation principal of the transformer is based on the skin effect and the mutual effect between the coils at high frequency. Because of the coaxially arranged coils, the magnetic field of the transformer can be modeled with an axisymmetric assumption. Using the model, we evaluate the electromagnetic field and calculate the lumped circuit parameters, i.e., inductance and resistance, which are compared with experimental values. >

Development of film transformer

In order to realize the light and small power supplies, we propose a film shape transformer. This new transformer is constructed by chemical etching process. Experimental works show that this film transformer has about 98% coupling factor over 500 kHz and over 95% efficiency at 1.5 MHz. As an initial test, we applied our film transformer to a push-pull type DC to DC converter and succeeded in obtaining 11 W output power. >

Inverse analysis for magnetic field source searching in thin film conductor

Previously, we have proposed the sampled pattern matching (SPM) method solving for the inverse problem. In the present paper, we propose a generalized SPM method. The generalized SPM method makes it possible to estimate both the direction and magnitude of currents. We apply this new method to the current estimation in a thin film conductor. Numerical simulation suggests the validity of the method. As a result, this paper presents an effective methodology to estimate a current distribution in a thin film conductor.

Improvement of the film transformer characteristics

Previously, we have proposed a thin film transformer. The operating principle of this transformer is based on the skin effect. Thereby, its weight and size are extremely small but its operating frequency having high efficiency is limited only to high frequency region. In order to remove this fault, we employ the thin ferrite tiles which have been sandwiched between the film conductors. As a result, we succeeded in widening the operating frequency range about 100 times compared with those of original one.

A thin film common mode noise filter and its evaluation by wavelet analysis

With the development of modern electronic switched mode power supplies, greater attention is being focused on line noise problems. To overcome this difficulty, we have previously proposed a resonant type inductor having a noise filtering capability. In the present paper, we develop a film filter implementation of a resonant type inductor. Also, we employ a wavelet analysis technique to evaluate the noise filtering characteristics of the filter. The thin film shape inductor was designed and was used eliminate the line noise caused by a switched mode power supply.

A new inductor having a noise filtering capability

In this paper, we propose a new inductor having a noise filtering capability based on a resonant phenomenon between the two adjacent series connected coils. The resonant impedance and frequency of this inductor can be controlled by changing the inductance as well as capacitance. Simple theoretical and experimental consideration clarify that the resonant impedance takes a larger value at lower frequency when Increasing the inductance. This means that it is possible to realize a noise filter without any external capacitors. Thus, we succeeded in realizing a near inductor having a noise filtering capability. >

A multi-resonant type inductor having notch filtering capability

In order to realize a compact size DC to DC converter power supply, the operating frequency must be in the mega hertz region. Operation at higher frequencies introduces an harmonic noise problem. This problem can be overcome by proposing a new multi-resonant type inductor which exhibits a notch filtering characteristic. This multi-resonant type inductor can be used to reduce problematic harmonic frequency.

Electromagnetic field analysis of film transformer

In this paper, we investigate a thin film transformer for small electronic devices. This transformer is composed of the lamination of thin film conductors. Both the primary and secondary coils of the film transformer are arranged coaxially on one layer and multiply laminated. The operation principle of the transformer is based on the skin effect and the mutual effect between the coils at high frequency. Using the integral equation method, we evaluate the electromagnetic field and calculate the lumped circuit parameters, (e.g. inductance and resistance, etc.). A fairly good agreement is obtained comparing with experimental values. Thus, the applied method is quite useful for design and investigation of the thin film transformer. >

A Resonant Phenomenon Between Adjacent Series Connected Coils and its Application to a Noise Filter

Abstract In this paper, we propose a new inductor having a noise filtering capability based on a resonant phenomenon between the two adjacent series connected coils. Although the resonant impedance and frequency of our inductor can be controlled by changing the inductance as well as capacitance, simple theoretical and experimental considerations clarify that the resonant impedance takes a larger value at lower frequency when increasing the inductance. This means that it is possible to realize a noise filter without any external capacitors. Thus, we have succeeded in realizing a new inductor having a noise filtering capability.

Estimation Of The Magnetization Currents In Permanent Magnets

Introduction The primary aim of the current article is to address a methodology to visualizing the magnetizing current in a permanent magnet Previously, we have proposed the sampled pattern matching method for estimating current distribution from locally measured magnetic fields[ 1-31 In the present paper, we propose a generalized sampled pattern matching method. This new method is applied to the estimation of equivalent current distribution in a permanent magnet The conventional sampled pattern matching method has been employed a current dipole model, which does not satisfl always the current continuity condition Our new method employs a loop current model, so that the current continuity condition is always satisfied Applying this new method to the estimation of equivalent magnetization currents in a permanent magnet, we have succeeded in visualizing the magnetization currents