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An embedded inductor constructed with Sendust powder composite films and embedded circuits is proposed. The composite films consist of mixed Sendust flaked powders and EPDM rubber. An embedded circuit is an etched spiral copper trace with 16 turns and two layers. Copper trace is patterned with a dimension of 0.025 mm thickness, 0.1 mm width, and 0.1 mm pitch. Regarding the performances of the proposed inductor, it was obtained that the simulated inductance and copper resistance are 4.7 uH and 770 m� , respectively, while the measured results are 5.0 uH and 720 m� , respectively. Measurements also show that the proposed inductor has relative high permeability and quality factor in a wide range of frequencies. It was confirmed that inductance of this inductor has a good stability to high frequency. To verify the usefulness of this inductor, the embedded inductor with a flexibility and the dimension of 10 mm× 7m m× 0.3 mm was applied to a step-up dc–dc converter that is fabricated in the flexible printed circuit. The output power of the fabricated dc–dc converter is 1.8 W (4.5 V/400 mA), and the switching frequency is 1.2 MHz. Finally, the fabricated dc–dc converter was tested and the maximum efficiency of 84% was obtained.

In this study, the losses due to the time-harmonic current in a permanent magnet synchronous motor (PMSM) are calculated through a co-analysis of the time harmonics using a space vector pulse width modulation (SVPWM) inverter. PMSM is typically used as a control motor. The current in the PMSM contains harmonics because the inverter voltage is not sinusoidal, and as a result, losses occur. These losses have a negative effect on the synchronous motor performance, which is vulnerable to heat. Therefore, for efficiency and performance evaluation of the PMSM, it is necessary to consider a co-analysis of the time harmonics. In this study, we present a co-analysis method for a PMSM designed for buses and compare the analysis results with those of the current source analysis in order to verify the significance of the co-analysis. In particular, it is observed that the difference in the eddy current losses in the PM individually determined with the current source analysis and co-analysis is approximately 500%. For validating this study, the experimental equipment is established, and it can be confirmed that the experimental results are close to the co-analysis results.

This paper shows a study on the demagnetization performance analysis of permanent magnet according to three kinds of rotor types of an interior permanent magnet synchronous motor (IPMSM). It is very important to consider demagnetization performance as well as motor performance such as rated torque, output current, and efficiency when designing IPMSM. Three kinds of rotor types according to permanent magnet arrangement; single layer type, v shape type, and double layer type are generally used for IPMSM. In the paper, the magnetic equivalent circuits according to each rotor type are proposed in order for initial design of thickness of permanent magnets considering demagnetization by lumped constant related to magnetic circuit. The volume of permanent magnets per pole and back EMF of each rotor type is assumed to equal for the comparison of demagnetization of IPMSMs with same performance each other. Next, distribution of demagnetization in the permanent magnet is analyzed by using finite element method (FEM) for the verification of the results by magnetic equivalent circuit.

This paper presents a method on a multiobjective optimal design of interior permanent magnet synchronous motor (IPMSM) with V-shaped permanent magnet rotor for high performance. In general, a design method adopting equivalent magnetic circuit is used for basic design of IPMSM. However, its use may give us wrong design result because of air-gap flux calculation method by using lumped reluctance parameters. Moreover, it has difficulty in considering arrangement of permanent magnets and barriers, but on the other hand, there exists high degree of freedom of permanent magnet rotor design of IPMSM. Therefore, finite element method (FEM) is needed for the precise design considering arrangement of permanent magnets and barriers. In order for effective V-shaped permanent magnet rotor design, Taguchi method by adopting five multiobjective functions is proposed as an optimal design method. The different optimal design results are suggested by adjusting weighting value of each objective function. Finally, the characteristics of optimal design model with V-shaped permanent magnet rotor are verified by experiment.

An integrated inductor using the low-temperature co-fired ceramics (LTCC) technology for low-power electronics was fabricated. The inductor has A/sub g/ circular spiral coil with 16 turns (2 turns /spl times/ 8 layers), a dimension of 11.52 mm in diameter, and 0.71 mm in thickness. To establish the calculation of inductance, including total resistance, the fabricated inductor was analyzed. It was confirmed that the calculated values were very close to the measured values. Finally, a low-profile ferrite core, with parameters at /spl mu//sub R/=2400 and AL value =4000 nH/mm /sup 2/, was applied to the inductor to increase inductance. As a result, inductance increased by 293%, compared to the uncored inductor.

A dual spiral sandwiched thin film inductor with a dimension of 5 mm /spl times/ 5 mm was fabricated by a LIGA-like micromachined process. FeBN magnetic films were used as a core material. The inductance and quality factor value of the inductor were measured approximately 1 /spl mu/H and 4 up to 5 MHz, respectively. Using the FeBN film inductor, a hybrid dc/dc converter (15 mm /spl times/ 12 mm /spl times/ 1.5 mm) was designed and fabricated. The circuit topology of the converter was a zero voltage switching clamp voltage (ZVS-CV) buck converter. An input of 3.6 V was bucked to 2.7 V at a switching frequency of 1.8 MHz. The maximum power was 1.5 W. The measured efficiency of the buck converter reached a maximum value of 80% and kept stable up to 300 mA of load currents at 1.8 MHz.

We fabricated a planar-type film inductor with good high frequency characteristics using a FeTaN soft magnetic film. While FeTaN films inherently show good soft magnetic properties and high saturation magnetization, addition of Ti underlayer with a combination of magnetic field annealing leads to an increase of anisotropy field (H/sub k/), thus improving high frequency characteristics. Planar-type spiral inductors using Ti/FeTaN films exhibit an inductance of /spl sim/1 /spl mu/H, resistance of /spl sim/2 ohm, and Q factor of 2.3 at 2 MHz. We also fabricated a hybrid ZVS-CV buck converter using the film inductor. The converter shows about 80% of the conversion efficiency at 1.2 MHz, which withstands a load current up to 300 mA.

We investigated the magnetic properties of as-sputtered FeTaN films as a function of deposition temperature and composition. At the deposition temperature higher than 200/spl deg/C, both soft magnetism and magnetic moments can be fully achieved. While the Ta and N contents in the films affect the magnetic properties, the N content exhibits stronger effects. The magnetic properties are affected by the film microstructures via, crystallinity, grain size, and formation of Fe/sub x/N phases. An excessive N incorporation into the films causes incomplete crystallization and/or formation of Fe/sub 3/N phases in the as-deposited state, leading to a poor soft magnetic property. As-deposited FeTaN film at the optimum composition of Fe/sub 91.7/Ta/sub 4.2/N/sub 4.1/ gives the best soft magnetic properties; coercivity of /spl sim//sub 2/ Oe and permeability of /spl sim/1600 stable up to the frequency of 100 MHz.