This article has shown the design and characterization of silicon-integrated thin-film micro-transformers and their application in a quasi-resonant flyback converter. Two micro-transformers with different turn ratios of 4:4 and 3:3 were designed. The micro-transformers in this study have elongated spiral shape windings sandwiched between two layers of the thin-film magnetic core, and this structure can leverage the anisotropic core property. The micro-transformers were built on a silicon substrate using micro-electro-mechanical systems (MEMSs) fabrication process to ensure a high integration level and high power density. The inductance of 4:4 and 3:3 micro-transformers are 57.3 and 31.5 nH, respectively, their coupling coefficients are 90.5% and 82.7% at 30–40 MHz, and the measured quality factors are 7.82 at 21 MHz and 8.94 at 35 MHz, respectively. A resonant flyback converter topology deploying with a high electron mobility transistor [Gallium nitride (GaN)] was used to evaluate the electrical performance of two micro-transformers. Two resonant flyback converters operating at zero voltage switching (ZVS) reached the maximum conversion efficiency of 46.4% (3:3) and 45.7% (4:4), respectively, with 3.3 V input. The 3:3 micro-transformer developed in this work achieved the highest power density of 128 mW/mm ² with a similar efficiency compared to other cored micro-transformers. The loss analysis of the flyback conversion circuit shows that the main losses in the circuit are the copper winding loss of the micro-transformer and the eddy current loss of the magnetic core. The conversion efficiency of the circuit will be improved by applying thicker copper and core lamination in the future.

This letter demonstrates an on-silicon integrated thin film coupled inductor using a novel cascade matrix concept to suit multiphase integrated voltage regulator (IVR) applications. The novel cascade matrix coupled (CMC) stripline inductor facilitates all-phase-coupled configuration to reduce the phase ripple current in IVRs. It also shows excellent scalability and neat floor planning. Moreover, the proposed CMC inductor uses double layer metal scheme for windings and interconnects, which significantly reduces the ac winding resistance. A four-phase CMC inductor has been successfully fabricated on-silicon substrate and characterized, which uses conventional thin film magnetic core deposition process to achieve in-plane magnetic uniaxial anisotropy. The device occupies 3.2 × 1.7 mm ² floor area and provides 19.5 nH phase inductance with 120 mΩ dc resistance. The saturation current for each phase is up to 0.4 A when the phase inductance drops by approximately 20%. The coupling coefficient between any two phases of the proposed CMC inductor is 0.27, much higher and more controllable than that of toroid core-based coupled inductors.

This paper presents the design, modeling, fabrication, and characterization of a novel electromagnetic vibration energy harvester (EVEH) using a compact flexure guide structure and opposing permanent magnets. The flexure guide is a unique cylindrical structure, and can transfer force and motion by the deformation of elastic beams. It allows the single-degree-of-freedom motion characteristic, and eliminates the friction between the permanent magnets and the housing structure, which exists in mostly reported magnet-spring based vibration energy harvesters. The structure also greatly reduces the spacing between the coil and the permanent magnets, which considerably increases the magnetic flux linkage through the coil. Experimental results show that the EVEH prototype can generate an output voltage of 6.08 V and output power of 4.02 mW from 0.1 g acceleration at resonant (19.5 Hz), achieving a normalized power density of 3.28 mW cm ^{− 3}g ^{− 2}. In addition, the flexure guide can be directly fabricated by 3D printing, which greatly simplifies the harvester assembly compared to other EVEHs reported. In terms of the proposed EVEH, a self-powered sensor network is implemented to transfer the GPS data to some appointed terminals.

The optimal algorithm plays a crucial role in optimizations of electromagnetic devices in terms of both the solution efficiency and the precision of the final result. To reduce the unnecessary information bombing a decision maker and to improve the convergence ability of solution procedures for multi-objective design problems, a vector preference-based physical programming method is proposed. To specify the region of interests of a decision maker, a preference frame is constructed using an aspiration point, a reservation point and a preference vector; to make a full use of the explored information, the sampling points are classified based on all the pseudo preferences in one single run and the aggregated preference functions are calculated in parallel. Dynamic pseudo preference translation offset vector is developed to accommodate different mapping mechanisms for a variety of the diverse optimization problems and increase the robustness of the algorithm. Typical test functions and inverse problem are solved to demonstrate the effectiveness and efficiency of the proposed method.