Planar Transformer Research Articles

A Novel AC/DC Bridgeless and Contactless Electrical Energy Transmission System for Multi-load Applications

In this paper, a novel AC/DC bridge-less and contact-less energy transmission system is proposed. The coreless planar transformer and magnetic dipole moment are applied to transmit electrical energy in non-contact manner. In addition, the input ac current of proposed converter has good power factor correction. Simultaneously, the primary-side switches have zero-voltage switching and the secondary-side diodes have zero-current transition. Thus, the power quality and efficiency of proposed contactless electrical energy transmission system can be upgraded. Furthermore, the proposed contactless electrical energy transmission system also can increase transmission distance with the voltage multiplier receiver connected in the rear of the secondary-side coreless planar transformer. Both the power transmission and circuit operation are explained in this paper. Finally, a prototype system is constructed and the validity has been confirmed with experiment and practical measurements.

FEA of PCB Multilayer Stack Up High Voltage Planar Transformer for Aerospace Application

High voltage planar transformer is a technology which can replace conventional transformer with its distinct advantages of saturation and cost efficiency. This paper includes, study and solution methods for PCB winding configuration in planar magnetic elements with multilayer stack up of PCB Cu-tracks, producing High voltage power supply for aerospace application. With finite element analysis (FEA) simulations, different simulation outcomes are discussed for inspecting flux intensity and current density distribution with computing Electric field strength and Magnetic fields. In principal conclusion of study, complete analysis and some practical design guidelines for multilayer PCB stack up are discussed in this paper.

A Compact Planar Transformer With an Improved Winding Configuration

A compact planar transformer with an improved winding configuration has been designed and fabricated. Meander-type design was engraved over the surface of a planar ferrite core, so that the primary and secondary windings can fit into the engraved design. The planar core, with the primary and secondary windings fit into it, was covered with another ferrite core, thus forming a compact planar transformer. Apical type AV polyimide film of 0.025 mm thickness is used between the windings to prevent short circuit. A coupling coefficient of >0.93 was achieved, while the primary and secondary inductance was ~1600 nH. A coupling coefficient for air core transformer with the windings of identical geometry was >0.35 and the inductance of the windings near 160 nH. Fabricated transformer prototype has significantly higher coupling coefficient and inductance of the windings in comparison with the previously developed planar transformer of the similar design.

Leakage Inductance Calculation for Planar Transformers With a Magnetic Shunt

The magnetic shunt is generally inserted in a planar transformer to increase the leakage inductance, which can be utilized as the series inductor in resonant circuits such as the LLC resonant converter. This paper presents a calculation methodology for the leakage inductance of the transformer with a magnetic shunt by means of the stored magnetic energy in the primary and secondary sides of the transformer using the magnetomotive force (MMF) variation method, as well as the stored energy in the shunt based on the reluctance model. The detailed calculation method is described. Both the finite-element analysis simulation and the experimental results have proven the validity of the proposed calculation method for leakage inductance.

Equivalent Circuit of a Planar Transformer Used for TWTA

In this paper, application of planar transformers in TWTA (Travelling-wave Tube Amplifier) is investigated and a method of equivalent circuit is used to study performance of planar transformers. The lumped parameters of planar transformers are extracted by FEM (Finite Element Method).

High Density Solenoidal Series Pair Symmetric Inductors and Transformers

A high density symmetric inductor using a novel combination of solenoidal wound series stacked spirals is proposed in this paper. Series stacking in the individual sections increases overall inductance density, while solenoidal winding pushes the quality factors ( Q ) to higher frequencies. The proposed inductor achieves more than 65% improvement in peak- Q value and 100% higher peak- Q frequency and self resonance frequency, while occupying 20% lesser area when compared with a standard symmetric inductor with crossovers. Implemented in a high resistivity 0.18 \(\mu \) m CMOS silicon-on-insulator process with dual-thick metal stack, the proposed inductor achieves 70-nH inductance and a Q of 11.3 operating at 1.6 GHz within \(250\times 250\) \(\mu \) m \(^2\) area. This translates to a record figure-of-merit of 12.2, which is highest in air core symmetric inductor literature. Further, the proposed inductor configuration is extended to realize a planar transformer with very high turns ratio of 9.25 using only two metals.

An Improved Layout Strategy for Common-Mode EMI Suppression Applicable to High-Frequency Planar Transformers in High-Power DC/DC Converters Used for Electric Vehicles

Presently, there is an immense impetus in the automotive industry to develop plug-in electric vehicles (PIEVs) to reverse the ever increasing green house gas emissions from fossil fuels and depleting fossil fuel resources. High-frequency ac-dc converters with an isolated output are one of the essential building blocks for transferring power from utility mains to the traction battery packs which store energy for propelling the EV. Generally, the ac/dc converters used in EVs include a PFC stage at the input side and an isolated dc/dc converter at the battery side. Due to the switching nature of the converter, electromagnetic compatibility (EMC) of these converters is an essential requirement, to ensure not only its own operation but also the safe and secure operation of surrounding electrical equipment. EVs possess a lot of sophisticated electronic circuits in the vicinity of the battery charging power converters. Thus, strict EMC standards of the on-board power converters must be met according to the CISPR 12 or SAEJ551/5 relevant EMC standards. Conventional passive filters used for EMI mitigation in power converters, comes at the expense of cost, size and weight, power losses, and printed circuit board real estate. In this paper, an electromagnetic interference (EMI) filter embedded into the main high-frequency planar transformer used in the dc/dc converter is proposed as a very cost-effective and efficient solution for EVs. The proposed structure is able to significantly suppress the common-mode (CM) EMI noise generated in the dc/dc converter. Experimental results have been obtained from a 3-kW prototype in order to prove the feasibility and performance of the proposed EMI filter. The results show that the proposed embedded EMI filter can effectively suppress the CM noise particularly for high switching frequency power converters. The proposed structure can be a very simple and cost-effective EMI filtering solution for future PIEVs.

Transformer Analysis for Wireless Power DC-DC Converters

This paper presents the analysis of two different types of transformer structures used in wireless power applications. Conventional litz wire windings are compared to planar windings in terms of AC/DC performance ratio, coupling and inductance. Planar and litz wire transformer arrangements are proposed. A 6W LLC wireless power converter is used to compare the different transfomer structures. Finite element anlysis is used to determine the transformer coupling coefficient and AC/DC ratios. The simulation results are validated by experimental measurements

Common-Mode Noise Cancellation by an Antiphase Winding in Multilayer Isolated Planar Transformer

Common-mode (CM) noise is always present in switch-mode power supplies. All International Electrical Commission class I appliances must have their chassis directly connected to the earth ground, which provides a low impedance path for CM noise to transfer from primary to secondary via the isolated transformer. A proposed planar transformer construction is analyzed and a comparison of CM noise cancellation performance with wire-wound transformers is presented. Planar transformers are found to have better noise cancellation throughout the conducted electromagnetic interference range, thanks to a better winding plane matching to the primary CM noise source winding plane. A planar transformer with two primary winding planes is investigated and a construction with antiphase winding is proposed for best CM noise attenuation.

Research on Lower-Order Body Matrix Method and the Configuration Transformation of Planar Metamorphic Mechanism

The lower-order body matrix method is proposed as to topological configuration issue of planar metamorphic mechanism. Through combining lower-order operator and type code of kinematic pair, the lower-order body matrix is built to describe the information of adjacent body and kinematic pair. In the research on configuration transformation of planar metamorphic mechanism, step-description method is put forward which adapts to the analysis of various planar metamorphic ways. Step mathematical equation is established based on the generalized operational rule of lower-order body matrix. Application example shows that the lower-order matrix built with lower-order body matrix method is simpler and more informative, which has many advantages over the adjacency matrix and the correlation matrix that cannot be combined with the kinematics and dynamics equations, and solve the issue that the low-order sequences can only describe the open chain metamorphic mechanism. Step-description method can describe various planar metamorphic configuration transformation process comprehensively, which the EU matrix method cannot complete, providing a new method on the research of planar metamorphic mechanism.

Transformation of the corner: A shield cloak and a planar retro-reflector

A metallic sheet, coated with a few blocks of all-dielectric isotropic materials, is presented for creating an illusion or an image of a corner based on quasi-conformal transformation optics. On the one hand, our design is able to generate cloaking effects to conceal objects hiding inside a corner. On the other hand, we propose to use such a planar transformation device to represent a corner reflector that reflects light directly back to its source. The full wave simulation shows our device is capable of operating considerably well in a broad frequency range, and presents only the appearance of a bare corner functioning as a shield cloak or a planar retro-reflector.

Characterization of SQUID-Based Null Detector for a Quantum Metrology Triangle Experiment

We present characterization of a null detector designed for an experiment aimed to close the quantum metrological triangle (QMT). The device is a SQUID amplifier equipped with a large winding-ratio planar input transformer improving the current resolution. We demonstrate equivalent input current noise down to 14 fA/Hz1/2. Furthermore, operation in a realistic environment of a dry dilution refrigerator hosting the QMT experiment is studied. We discuss particular challenges set by such system as the cryogenics introduces relatively large magnetic interference. We present data from measurements simulating the final QMT experiment and introduce the requirements for the averaging and bias reversal.

Design and analysis of a high frequency DC–DC converters for fuel cell and super-capacitor used in electrical vehicle

This work focuses on the application of the high frequency DC–DC converters used in electric vehicles. Two converters are necessary. The first converter is interposed between the fuel cell and the DC–AC inverter. It is unidirectional. The second one is used as interface between the ultra-capacitor and the DC–AC inverter. It allows the bidirectional of the power transfer. Each converter is composed of two full bridges, LC resonant filter and two planar transformers. The use of high frequency transformer allows to minimize the size and weight of the converter, produce a higher voltage in secondary side from input voltage (fuel cell or super-capacitor) and isolate the full bridges. The control strategy of the converters is the phase shift. The converters have been designed, realised and controlled by an FPGA board. To demonstrate the converters feasibility, two converters are implemented and tested. The switching frequency of two converters is 20 kHz. The first converter has a 24-V input and 200 V/1.2 kW output. But, the second converter has a 12.5-V input and 100 V/400 W output.

Rapid analysis and optimization of planar Yagi-Uda dipole arrays printed on a dielectric substrate

Planar antenna modeling requires a constrained solution space and open boundaries and so is highly computationally intensive. One of the methods used to overcome this is by using method of moments simulation. The method of moments is a highly efficient method of solving wire antenna structures and is commonly used in antenna optimization. A method of transforming a wire antenna structure to a planar antenna structure is presented using a 4-element Yagi-Uda antenna designed to resonate at 905 MHz. The wire to planar transformation is based on the circular cross section wire to planar strip, a spacing adjustment based on interelement capacitance, and a length scaling to compensate for the change in effective permittivity. The planar antenna shows slightly improved impedance performance at the resonance [voltage standing wave ratio VSWR=1.39]. This transformation decreased the antenna footprint by 15.11% after conversion for a wire antenna to a planar antenna in air with similar radiation characteristics and on FR4 1.6 mm thickness, the footprint increased by 52%. The antenna simulation time was reduced from 15 min using finite element method to less than 10 s for one cycle by using the method of moments solver. All antenna properties are essentially unchanged. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:184-190, 2014.

Applying Response Surface Methodology to Small Planar Transformer Winding Design

Planar transformers provide a light-weight and low-profile solution for power electronic converters with highly reproducible parameters and simple manufacturability. Parasitic inductances, capacitances, and resistances in planar magnetics are difficult to model due to the complex interactions between the physical winding arrangement of each layer and the core geometry (track width, air gap, clearance, etc.). These nonlinear and multivariate magnetic devices play a key role in defining the performance of traditional, soft-switching, and resonant converters by ruling behaviors such as ringing, self-resonant frequency, conduction losses, and the current rate of change in these converters. In this paper, a methodology for determining parametric models for leakage and magnetizing inductance, inter- and intrawinding capacitances, and the winding resistance of small planar transformers is presented using a variety of winding arrangements. The models are employed to shape the winding design to control parasitic elements in order to optimize soft-switching and resonant converters. A central composite design based on the design of experiment methodology is employed on finite element simulations to provide the comprehensive models. Results from physical verification on a planar Ferroxcube ER18/3.2/10-3F3 core set are provided and show excellent correlation between models and verification tests. The method is later employed to effectively design an LLC resonant converter, which is also experimentally verified to illustrate the benefits of the proposed method. The methodology can be employed to characterize and design planar transformers and to predict their performances as part of a variety of power electronic converters.

A Novel Planar Transformer Design Based on a Variable Width Winding

The trend toward high power density, high operating frequency and low profile packaging in power converters will determine designers to replace the conventional Cu-wires transformers with planar transformers. In this paper a novel variable track width per turn design is proposed for the transformer windings. The basic design idea consists of matching the winding resistances per turn in order to maintain a flux balance among turns. The complete design methodologies for both variable and constant width windings are presented and compared. Theoretical design equations are confirmed using a finite element analysis (FEA) simulation. A 10W half bridge LLC converter prototype has been constructed employing both winding structures. Experimental results show a 0.4% converter efficiency improvement using the novel planar transformer based on the new variable width design compared to the conventional constant width approach

Improved High-Frequency Planar Transformer for Line Level Control (LLC) Resonant Converters

An improved high-frequency magnetic-integrated planar transformer is demonstrated. Compared with conventional planar integrated magnetics, the improved structure has better leakage inductance adjustment. Also, instead of expensive printed circuit board windings on the primary side, multistrand Litz wires are used. The transformer is fabricated with two common EE shape magnetic cores along with magnetic insertions placed between the primary and secondary windings outside the main core. A three-dimensional finite-element model is used to investigate the eddy current losses and the adjustment of the leakage inductance.

Design, Modeling, and Analysis of a Compact Planar Transformer

This paper presents a new design of a planar transformer. Over the surface of a flat core, meander-type design was engraved, so that symmetrically adjusted primary and secondary coils, of the same meander-type, can fit into the engraved design. Primary and secondary coils were covered with another flat core consequently forming a compact planar transformer. Windings of primary and secondary coils are printed on both sides of PCB. Conductive stripes of a winding from upper and bottom layer are connected by vias. The transformer was analyzed when the primary and secondary coils were without a core and with a core. High frequency parameters of the transformer were obtained by finite element modeling software and Impedance Analyzer HP4194A in the frequency range from 50 kHz to 1 MHz. The transformer is intended to be used in DC-DC converters (for switching frequency up to several hundred kHz).

An analysis of the possibility of intersystem transformations for purposes of geo-referencing old mine workings

Abstract The paper is dedicated to the issues of both planar and spatial transformations with respect to the territory affected by mining activities. The planar transformations have been applied among the planar Otto mine coordinate system, St. Stephen Datum of Cadastre Coordinates, and the Datum of Uniform Trigonometric Cadastral Network (hereinafter referred to as JTSK). Here basic transformation characteristics among the above systems are defined. The spatial transformation is performed through a point coordinate conversion between the JTSK and the European Terrestrial Reference System (hereinafter referred to as ETRS89) where conventional relations as well as other conversion possibilities were described. Part of the article is the execution of an experiment of a direct transformation between the St. Stephen Datum of Cadastre Coordinates and the ETRS98 system for the territory of Brno, which was not affected by mining activities. For the above transformation, 8 trigonometric points were used, for which the identity analysis had been done initially. Furthermore, the Interpolation and One Step Transformations were tested, which solve the conversion as divided tasks for both position and heights. The Interpolation Transformation showed better values for residues. The results of the above experiment will be applied for purposes of surveying old mine workings using the GNSS technology.

Microtransformer-Based Isolated Signal and Power Transmission

Based on an automatic backend wire bonder as a coil winding machine, microtransformers are produced and their feasibility evaluated for isolated signal and power transmission. Automatic wire bonders allow to precisely shape 25-μm diameter gold wire around prefabricated cores and yokes at high speed. Former reports of wire bonded microcoils treated individual solenoids with low mutual inductance, whereas in this study transformers with strongly coupled microsolenoids are presented. The process is fully compatible with standard microelectronic manufacturing and, therefore, enables the direct integration of transformers into a given electronic circuit, either on-chip or on a printed circuit board, without the need for subsequent mounting steps. Unlike typical integrated planar transformers with known disadvantages concerning their electric properties, wire bonding allows the production, for example, of perfectly 3-D solenoidal transformer designs. The microtransformers are evaluated using a custom digital signal isolator system for isolation voltages of up to 5 kV. The microtransformers can also be used in an isolated dc-dc power converter to transmit energy.