Showing papers on "Inductor published in 2005"

Inductors and Transformers for Power Electronics

Abstract: FUNDAMENTALS OF MAGNETIC THEORY Basic Laws of Magnetic Theory Magnetic Materials Magnetic Circuits References FAST DESIGN APPROACH INCLUDING EDDY CURRENT LOSSES Fast Design Approach Examples Conclusions Appendix 2.A.1: Core Size Scale Law for Ferrites in Non-Saturated Thermal Limited Design Appendix 2.A.2: Eddy Current Losses for Wide Frequency Appendix 2.A.3: MathCAD Example Files References SOFT MAGNETIC MATERIALS Magnetic Core Materials Comparison and Applications of the Core Materials in Power Electronics Losses in Soft Magnetic Materials Ferrite Core Losses with Non-Sinusoidal Voltage Waveforms Wide Frequency Model of Magnetic Sheets Including Hysteresis Effects Appendix 3.A: Power and Impedance of Magnetic Sheets References COIL WINDING AND ELECTRICAL INSULATION Filling Factor Wire Length Physical Aspects of Breakdown Insulation Requirements and Standards Thermal Requirements and Standards Magnetic Component Manufacturing Sheet References EDDY CURRENTS IN CONDUCTORS Introduction Basic Approximations Losses in Rectangular Conductors Quadrature of the Circle Method for Round Conductors Losses of a Current Carrying Round Conductor in 2-D Approach Losses of a Round Conductor in a Uniform Transverse AC Field Low Frequency 2-D Approximation Method for Round Conductors Wide Frequency Method for Calculating Eddy Current Losses in Windings Losses in Foil Windings Losses in Planar Windings Appendix 5.A.1: Eddy Current 1-D Model for Rectangular Conductors Appendix 5.A.2: Low Frequency 2-D Models for Eddy Current Losses in Round Wires Appendix 5.A.3: Field Factor For Inductors References THERMAL ASPECTS Fast Thermal Design Approach (Level 0 Thermal Design) Single Thermal Resistance Design Approach (Level 1 Thermal Design) Classic Heat Transfer Mechanisms Thermal Design Utilizing a Resistance Network Contribution to Heat Transfer Theory of Magnetic Components Transient Heat Transfer Summary Appendix 6.A: Accurate Natural Convection Modeling for Magnetic Components References PARASITIC CAPACITANCES IN MAGNETIC COMPONENTS Capacitance Between Windings: Inter Capacitance Self-Capacitance of a Winding: Intra Capacitance Capacitance Between the Windings and the Magnetic Material Practical Approaches for Decreasing the Effects of Parasitic Capacitances References INDUCTOR DESIGN Air Coils and Related Shapes Inductor Shapes Typical Ferrite Inductor Shapes Fringing in Wire-Wound Inductors with Magnetic Cores Eddy Currents in Inductor Windings Foil Wound Inductors Inductor Types Depending on Application Design Examples of Different Types of Inductors Fringing Coefficients For Gapped-Wire-Wound Inductors Analitical Modeling of Combined Litz Wire-Full Wire Inductors References TRANSFORMER DESIGN Transformer Design in Power Electronics Magnetizing Inductance Leakage Inductance Using Parallel Wires and Litz Wires Interleaved Windings Superimposing Frequency Components Superimposing Modes References OPTIMAL COPPER/CORE LOSS RATIO IN MAGNETIC COMPONENTS Simplified Approach Loss Minimization in the General Case Loss Minimization Without Eddy Current Losses Loss Minimization Including Low-Frequency Eddy Current Losses Summary Examples References MEASUREMENTS Introduction Temperature Measurements Power Losses Measurements Measurement of Inductances Core Loss Measurements Measurement of Parasitic Capacitances Combined Measuring Instruments References APPENDIX A: RMS VALUES OF WAVEFORMS Definitions RMS Values of Some Basic Waveforms RMS Values of Common Waveforms APPENDIX B: MAGNETIC CORE DATA ETD Core Data (Economic Transformer Design Core) EE Core Data Planar EE Core Data ER Core Data UU Core Data Ring Core Data (Toroid Core) P Core Data (Pot Core) PQ Core Data RM Core Data APPENDIX C: COPPER WIRES DATA Round Wire Data American Wire Gauge Data Litz Wire Data APPENDIX D: MATHEMATICAL FUNCTIONS References INDEX

A 233-MHz 80%-87% efficient four-phase DC-DC converter utilizing air-core inductors on package

Abstract: We demonstrate an integrated buck dc-dc converter for multi-V/sub CC/ microprocessors. At nominal conditions, the converter produces a 0.9-V output from a 1.2-V input. The circuit was implemented in a 90-nm CMOS technology. By operating at high switching frequency of 100 to 317 MHz with four-phase topology and fast hysteretic control, we reduced inductor and capacitor sizes by three orders of magnitude compared to previously published dc-dc converters. This eliminated the need for the inductor magnetic core and enabled integration of the output decoupling capacitor on-chip. The converter achieves 80%-87% efficiency and 10% peak-to-peak output noise for a 0.3-A output current and 2.5-nF decoupling capacitance. A forward body bias of 500 mV applied to PMOS transistors in the bridge improves efficiency by 0.5%-1%.

Midinfrared resonant magnetic nanostructures exhibiting a negative permeability.

Abstract: In 1968, Veselago proposed the concept of a negative refractive index or left-handed material (LHM) [1] with both a negative permittivity" and a negative permeability � . Many interesting properties are associated with negative materials including a negative index of refraction, backward phase propagation, a reversed Doppler effect, and backward emission of Cherenkov radiation. Recently, interest in LHMs has increased substantially with the theoretical prediction that a planar slab of LHM functions as a perfect lens without any diffractive loss of resolution [1,2] and with the first demonstrations of LHMs in the rf and THz electromagnetic regions [3‐6]. While metals provide a negative permittivity at frequencies below the plasma frequency, naturally occurring materials with negative permeability are not available. Composite electromagnetic materials with resonant structures with sizes much less than the wavelength can act as an effective homogeneous media with a negative permeability. Pendry et al. proposed a split ring structure that responds to the magnetic field of incident radiation [7]. The split ring structure (SRS) can be viewed as an equivalent inductor-capacitor (LC) tank circuit. In the presence of a time-varying magnetic field, the magnetic field generated by the current induced in the ring opposes the external magnetic field. At frequencies in the vicinity of the resonance, a negative effective permeability can be realized. While most experimental work has been done at microwave and, more recently, THz frequencies, extending the phenomena to infrared (IR) and visible frequencies will greatly increase the range of applications. Based on the previous modeling work [7] and on the fabrication difficulties associated with scaling the SRS to higher frequency, there has been general pessimism about the prospects of extending these properties to optical frequencies in metallic structures. In this Letter, we describe the fabrication, characterization, and modeling of arrays of a new nanostructure design with resonances in the mid-IR region and properties that demonstrate strong magnetic activity indicative of negative permeability. To our knowledge, this is the first experimental work on negative permeability reported in the IR. Importantly, the scaling of these results to even higher frequency is investigated, and a structure exhibiting negative permeability in the technologically important near-IR range 1:3 � m is proposed. The structure (Fig. 1, top) consists of an array of gold ‘‘staples’’ each with two outwardly splayed footings, separated from a thick continuous gold film by a ZnS dielectric layer. Each staple is a LC circuit with the structure part of the inductor associated with the upper loop of the staple and with two capacitors formed between the gold staple footings—the dielectric layer and the bottom gold layer. As a result of the thick Au film, light can only be reflected from or absorbed within the structure; there is no transmission in the IR. For analysis, it is simpler to view this structure in transmission as the staple and its image mir

Boost DC-AC inverter: a new control strategy

Abstract: Boost dc-ac inverter naturally generates in a single stage an ac voltage whose peak value can be lower or greater than the dc input voltage. The main drawback of this structure deals with its control. Boost inverter consists of Boost dc-dc converters that have to be controlled in a variable-operation point condition. The sliding mode control has been proposed as an option. However, it does not directly control the inductance averaged-current. This paper proposes a control strategy for the Boost inverter in which each Boost is controlled by means of a double-loop regulation scheme that consists of a new inductor current control inner loop and an also new output voltage control outer loop. These loops include compensations in order to cope with the Boost variable operation point condition and to achieve a high robustness to both input voltage and output current disturbances. As shown by simulation and prototype experimental results, the proposed control strategy achieves a very high reliable performance, even in difficult transient situations such as nonlinear loads, abrupt load changes, short circuits, etc., which sliding mode control cannot cope with.

Analysis of integrated boost-flyback step-up converter

Abstract: The operating principles, theoretical analysis, and design methodology of a high-efficiency step-up converter are presented. The integrated boost-flyback converter (IBFC) uses coupled-inductor techniques to achieve high step-up voltage with low duty ratio, and thus the slope compensation circuit is disregarded. The voltage gain and efficiency at steady state are derived using the principles of inductor volt-second balance, capacitor charge balance and the small-ripple approximation for continuous-conduction mode. Finally, a 35 W, 12 V DC input, 48 V DC output, f/sub sw/= 40 kHz IBFC has been implemented in the laboratory to validate the theoretical analysis. A design procedure is expounded, and design guidelines for selecting critical components are also presented. It is shown that high voltage gain with high efficiency can be achieved by the IBFC system.

Apparatus and process for reducing the susceptibility of active implantable medical devices to medical procedures such as magnetic resonance imaging

Abstract: A feedthrough terminal assembly for an active implantable medical device (AIMD) includes a plurality of leadwires extending from electronic circuitry of the AIMD, and a lossy ferrite inductor through which the leadwires extend in non-conductive relation for increasing the impedance of the leadwires at selected RF frequencies and reducing magnetic flux core saturation of the lossy ferrite inductor through phase cancellation of signals carried by the leadwires A process is also provided for filtering electromagnetic interference (EMI) in an implanted leadwire extending from an AIMD into body fluids or tissue, wherein the leadwire is subjected to occasional high-power electromagnetic fields such as those produced by medical diagnostic equipment including magnetic resonance imaging

High boost converter using voltage multiplier

Abstract: With the increasing demand for renewable energy, distributed power included in fuel cells have been studied and developed as a future energy source. For this system, a power conversion circuit is necessary to interface the generated power to the utility. In many cases, a high step-up DC/DC converter is needed to boost low input voltage to high voltage output. Conventional methods using cascade DC/DC converters cause extra complexity and higher cost. The conventional topologies to get high output voltage use flyback DC/DC converters. They have the leakage components that cause stress and loss of energy that results in low efficiency. This paper presents a high boost converter with a voltage multiplier and a coupled inductor. The secondary voltage of the coupled inductor is rectified using a voltage multiplier. High boost voltage is obtained with low duty cycle. Theoretical analysis and experimental results verify the proposed solutions using a 300 W prototype.

Design and analysis of switched-capacitor-based step-up resonant converters

Abstract: A switched-capacitor-based step-up resonant converter is proposed. The voltage conversion of the converters is in step-up mode. By adding a different number of switched-capacitor cells, different output voltage conversion ratios can be obtained. The voltage conversion ratio from 2 to any whole number can therefore be generated by these switching-capacitor techniques. A resonant tank is used to assist in zero-current switching hence the current spike, which usually exists for classical switched-capacitor can be eliminated. Both high-frequency operations and high efficiency are possible. Generalized analysis and design method of the converters are also presented. Experimental results verified the theoretical analysis.

30-100-GHz inductors and transformers for millimeter-wave (Bi)CMOS integrated circuits

Abstract: Silicon planar and three-dimensional inductors and transformers were designed and characterized on-wafer up to 100 GHz. Self-resonance frequencies (SRFs) beyond 100 GHz were obtained, demonstrating for the first time that spiral structures are suitable for applications such as 60-GHz wireless local area network and 77-GHz automotive RADAR. Minimizing area over substrate is critical to achieving high SRF. A stacked transformer is reported with S/sub 21/ of -2.5 dB at 50 GHz, and which offers improved performance and less area (30 /spl mu/m/spl times/30 /spl mu/m) than planar transformers or microstrip couplers. A compact inductor model is described, along with a methodology for extracting model parameters from simulated or measured y-parameters. Millimeter-wave SiGe BiCMOS mixer and voltage-controlled-oscillator circuits employing spiral inductors are presented with better or comparable performance to previously reported transmission-line-based circuits.

Power line communication using power factor correction circuits

Abstract: A PFC circuit modulating a power line using pulse width modulation (PWM) to drive a power MOSFET and series inductor across the power line. Since many modern electronic systems include a power factor correction circuit (PFC) that already includes a series inductor and power MOSFET, a PLC is incorporated into a controller to inject a PLC transmit signal into a control loop for the PFC circuit. This can be done using either an analog PFC controller, such as the UCC28517, the UCC2819A, or a digital PFC controller such as based on a TMS320C24xx DSP.

Operation modes and characteristics of the Z-source inverter with small inductance

Abstract: The Z-source inverter utilizing a unique LC network and forbidden shoot-through states provides unique features, such as the ability to buck and boost voltage with a single stage simple structure. The analysis and control methods provided in the literature are based on an assumption that the inductor is relatively large and the inductor current is continuous and has small ripple. This assumption becomes invalid when the inductance is small in order to minimize the inductor's size and weight for some applications where volume and weight are crucial. Under this small inductance condition, the inductor current becomes high ripple or even discontinuous. As results, the Z-source inverter exhibits new operation modes that have not been discussed before. This paper analyzes these new operation modes and voltage boost relationship of the Z-source inverter under the low inductance and large current ripple condition.

Boost Converter with Coupled Inductors and Buck-Boost Type of Active Clamp

Abstract: This paper proposes a boost converter with coupled inductors and buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate voltage spike induced from the trapped energy in leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio when even under high step-up applications, reducing voltage and current stresses significantly. Moreover, since both main and auxiliary switches can be turned on with zero voltage switching, switching loss can be reduced and conversion efficiency therefore can be improved significantly. A 200 W prototype of the proposed boost converter was built from which experiment results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively. It is relatively feasible for applications to fuel cell and battery power conversion

Suppression of line voltage related distortion in current controlled grid connected inverters

Abstract: The influence of selected control strategies on the level of low-order current harmonic distortion generated by an inverter connected to a distorted grid is investigated through a combination of theoretical and experimental studies. A detailed theoretical analysis, based on the concept of harmonic impedance, establishes the suitability of inductor current feedback versus output current feedback with respect to inverter power quality. Experimental results, obtained from a purpose-built 500-W, three-level, half-bridge inverter with an L-C-L output filter, verify the efficacy of inductor current as the feedback variable, yielding an output current total harmonic distortion (THD) some 29% lower than that achieved using output current feedback. A feed-forward grid voltage disturbance rejection scheme is proposed as a means to further reduce the level of low-order current harmonic distortion. Results obtained from an inverter with inductor current feedback and optimized feed-forward disturbance rejection show a THD of just 3% at full-load, representing an improvement of some 53% on the same inverter with output current feedback and no feed-forward compensation. Significant improvements in THD were also achieved across the entire load range. It is concluded that the use of inductor current feedback and feed-forward voltage disturbance rejection represent cost-effect mechanisms for achieving improved output current quality.

A single-phase inverter system for PV power injection and active power filtering with nonlinear inductor consideration

Abstract: This paper proposes a single-phase two-wire inverter system for photovoltaic (PV) power injection and active power filtering (APF) with nonlinear inductor consideration. The proposed system can fully or partially perform APF, process PV power, eliminate harmonic currents, improve power factor, and take into account the nonlinear effect of its output filter inductor. In the system, even though only the utility current is sensed, both APF and maximum power point tracking features can be still achieved, reducing the number of current sensors and cost significantly. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator and a defined limit circle. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase the accuracy of the estimated current. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the algorithm.

Generalised steady-state analysis of multiphase interleaved boost converter with coupled inductors

Abstract: The generalised steady-state analysis of the multi-phase interleaved boost converter with coupled inductors operated in continuous inductor current mode is addressed. The analytical expressions for efficiency, inductor and input currents, and output voltage are derived from the transformed average state-space model. Generalised expressions for the input and inductor current ripples and the output voltage ripple are also derived for various inductor couplings and the characteristics are analysed according to the inductor couplings. The steady-state performance is verified experimentally.

A novel winding-coupled buck converter for high-frequency, high-step-down DC-DC conversion

Abstract: This paper analyzes the fundamental limitations of the buck converter for high-frequency, high-step-down dc-dc conversion. Further modification with additional coupled windings in the buck converter yields a novel topology, which significantly improves the efficiency without compromising the transient response. An integrated magnetic structure is proposed for these windings so that the same magnetic cores used in the buck converter can be used here as well. Furthermore, it is easy to implement a lossless clamp circuit to limit the device voltage stress and to recover inductor leakage energy. This new topology is applied for a 12V-to-1.5V/25A voltage regulator module (VRM) design. At a switching frequency of 2MHz, over 80% full-load efficiency is achieved, which is 8% higher than that of the conventional buck converter.

Magnetics on silicon: an enabling technology for power supply on chip

Abstract: Data from the ITRS2003 roadmap for 2010 predicts voltages for microprocessors in hand-held electronics will decrease to 0.8V with current and power increasing to 4A and 3W, respectively. Consequently, low power converters will move to multimegahertz frequencies with a resulting reduction in capacitor and inductor values by factors of 5 and 20, respectively. Values required at 10 MHz, for a low power buck converter, are estimated at 130 nH and 0.6 uF, compatible with the integration of magnetics onto silicon and the concept of power supply-on-chip (PSOC). A review of magnetics-on-silicon shows that inductance values of 20 to 40nH/mm/sup 2/ can be achieved for winding resistances less than 1/spl Omega/. A 1-/spl mu/H inductance can be achieved at 5 MHz with dc resistance of 1/spl Omega/ and a Q of four. Thin film magnetic materials, compatible with semiconductor processing, offer power loss density that is lower than ferrite by a factor of 5 at 10 MHz. Other data reported includes, lowest dc resistance values of 120 m/spl Omega/ for an inductance of 120 nH; highest Q of 15 for an inductance of 350 nH and a current of 1 A for a 1- /spl mu/H inductor. Future technology challenges include reducing losses using high resistivity, laminated magnetic materials, and increasing current carrying capability using high aspect-ratio, electroplated copper conductors. Compatible technologies are available in the power switch, control, and packaging space. Integrated capacitor technology is still a long-term challenge with maximum reported values of 400 nF/cm/sup 2/.

Power tracking for nonlinear PV sources with coupled inductor SEPIC converter

Abstract: The photovoltaic (PV) generator exhibits a nonlinear i-v characteristic and its maximum power (MP) point varies with solar insolation. In this paper, a V2-based MP point tracking (MPPT) scheme is developed using a buck-boost transformation topology. Although several buck-boost transformation topologies are available we have considered here a coupled inductor SEPIC converter for experimentation. To achieve almost ripple-free array current we have used ripple steering phenomena with the help of integrated inductor. This integrated inductor not only reduces the magnetic core requirements but also improves converter performance. Mathematical models are formulated and tracking algorithm is evolved. A combined PV system simulation model is developed in the SIMULINK. For a given solar insolation, the tracking algorithm changes the duty ratio of the converter such that the solar cell array (SCA) voltage equals the voltage corresponding to the MP point. This is done by the tracking algorithm, which mainly computes the power proportional to square of terminal voltage and changes the duty ratio of the converter so that this power is maximum. The proposed algorithm is implemented in real-time with the help of Analog Device ADMC-401 DSP evaluation module. The tracking program is developed to perform experimental investigations using analog-to-digital converter (ADC) interrupt. Using this processor we are able to track the MP within 200 ms. The proposed peak power tracking effectiveness is demonstrated through simulation and experimental results.

Reconfigurable RFICs in Si-based technologies for a compact intelligent RF front-end

Abstract: This paper presents reconfigurable RF integrated circuits (ICs) for a compact implementation of an intelligent RF front-end for multiband and multistandard applications. Reconfigurability has been addressed at each level starting from the basic elements to the RF blocks and the overall front-end architecture. An active resistor tunable from 400 to 1600 /spl Omega/ up to 10 GHz has been designed and an equivalent model has been extracted. A fully tunable active inductor using a tunable feedback resistor has been proposed that provides inductances between 0.1-15 nH with Q>50 in the C-band. To demonstrate reconfigurability at the block level, voltage-controlled oscillators with very wide tuning ranges have been implemented in the C-band using the proposed active inductor, as well as using a switched-spiral resonator with capacitive tuning. The ICs have been implemented using 0.18-/spl mu/m Si-CMOS and 0.18-/spl mu/m SiGe-BiCMOS technologies.

Design and Control of a supercapacitor storage system for traction applications

Abstract: The storage system in this paper is made of supercapacitors. The main goal is to ensure an efficient energy management in a series hybrid vehicle, even if braking resistors are still needed. Design considerations are discussed. In particular the influence of the inductor resistance on the system stability is described. A maximum control structure is then deduced from the energetic macroscopic representation of the storage system. Comparisons between experimentation and simulation are presented in order to highlight the influence of the inductor resistor. Experiments are then carried out on a normal operating cycle.

Analysis and design of inductive coupling and transceiver circuit for inductive inter-chip wireless superconnect

Abstract: A wireless bus for stacked chips was developed by utilizing inductive coupling among them. This paper discusses inductor layout optimization and transceiver circuit design. The inductive coupling is analyzed by a simple equivalent circuit model, parameters of which are extracted by a magnetic field model based on the Biot-Savart law. Given communication distance, transmit power, data rate, and SNR budget, inductor layout size is minimized. Two receiver circuits, signal sensitive and yet noise immune, are designed for inductive nonreturn-to-zero (NRZ) signaling where no signal is transmitted when data remains the same. A test chip was fabricated in 0.35-/spl mu/m CMOS technology. Accuracy of the models is verified. Bit-error rate is investigated for various inductor layouts and communication distance. The maximum data rate is 1.25 Gb/s/channel. Power dissipation is 43 mW in the transmitter and 2.6 mW in the receiver at 3.3 V. If chip thickness is reduced to 30 /spl mu/m in 90-nm device generation, power dissipation will be 1 mW/channel or bandwidth will be 1 Tb/s/mm/sup 2/.

Precision inductive devices and methods

Abstract: A low cost, low profile, small size and high performance inductive device for use in, eg, electronic circuits In one exemplary embodiment, the device includes a ferrite core comprising multiple inductors and optimized for electrical and magnetic performance Improvements in performance are obtained by, inter alia, control of the properties of the gap region(s) as well as placement of the windings relative to the gap The magnetic path properties of the inductors at the ends of the device are also optionally controllable so as to provide precise matching of inductances Optionally, the device is also self-leaded, thereby simplifying its installation and mating to a parent device (eg, PCB) Methods for manufacturing and utilizing the device are also disclosed

Improving the Characteristics of integrated EMI filters by embedded conductive Layers

Abstract: Discrete electromagnetic interference (EMI) filters have been used for power electronics converters to attenuate switching noise and meet EMI standards for many years. Because of the unavoidable structural parasitic parameters of the discrete filter components, such as equivalent parallel capacitance (EPC) of inductors and equivalent series inductance (ESL) of capacitors, the effective frequency range of the discrete filter is normally limited. Aiming at improving high frequency performance and reducing size and profile, the integrated EMI filter structure has been proposed based on advanced integration and packaging technologies , . Some improvements have been made but further progress is limited by EPCs of the filter inductors, which is restricted by dimension, size and physical structure. In this paper, a new structural winding capacitance cancellation method for inductors is proposed. Other than trying to reduce EPCs, a conductive ground layer is embedded in the planar inductor windings and the structural capacitance between the inductor winding and this embedded layer is utilized to cancel the parasitic winding capacitance. In order to obtain the best cancellation effect, the structural winding capacitance model of the planar spiral winding structure is given and the equivalent circuit is derived. The design methodology of the layout and area of the embedded ground layer is presented. Applying this method, an improved integrated EMI filter is designed and constructed. The experimental results show that the embedded conductive layer can effectively cancel the parasitic winding capacitance, hence ideal inductor characteristics can be obtained. With the help of this embedded conductive layer, the improved EMI filter has much smaller volume and profile and much better characteristics over a wide frequency range, compared to the former integrated EMI filter and the discrete EMI filter.

Electrical conductivity measurement of metal plates using broadband eddy-current and four-point methods

Abstract: Electrical conductivity of metal plates is measured by two distinct methods and the uncertainty associated with each method is evaluated. First, the impedance of an air-cored eddy-current coil is measured in the frequency range 100 Hz to 20 kHz. Corrections are made to account for the fact that the coil is not a pure inductor but exhibits finite resistance and capacitance in and between the windings. Then, the conductivity of brass and stainless steel plates is determined with 3 and 2% uncertainty (68% confidence level) by seeking the best fit (least-mean-square error) between experimental measurements of coil impedance and values calculated theoretically. The residual error in the fitting process is found to be the main indicator of uncertainty in the conductivity measurement. Second, four-point alternating current potential drop measurements are made on the same samples in the frequency range 1–100 Hz. Conductivity is determined from these measurements by means of a simple analytic formula, valid in a quasi-static regime, with an uncertainty approximately 0.5%. The main source of uncertainty in the four-point conductivity measurement is scatter in the voltage measurements. Both of these techniques give rise to smaller uncertainties in the measurement of conductivity than a MIZ-21A eddy-current instrument (2% and 40% for brass and stainless steel, respectively) and without the need for calibration specimens. In addition, the four-point approach is independent of magnetic permeability below a certain characteristic frequency and can be used to measure conductivity of ferrous metals. As an example, the conductivity of a spring steel plate is also determined.

An improved boost converter with coupled inductors and buck-boost type of active clamp

Abstract: This paper proposes an improved boost converter with coupled inductors and buck-boost type of active-clamp feature, PWM control and zero-voltage switching in both main and auxiliary switches. In the converter, the active-clamp circuit is used to eliminate voltage spike induced from the leakage inductor of the coupled inductors. The active switch of the converter can still sustain a proper duty cycle when it operates with a high step-up voltage ratio, reducing voltage stress significantly. A set of passive-clamping circuit is adopted to eliminate undesired resonance between leakage inductor of the coupled inductors and stray capacitor of the boost diode, recovering trapped energy. Thus, conversion efficiency can be improved significantly. A 200 W prototype of the proposed boost converter was built from which experimental results have shown that efficiency can reach as high as 92% and surge can be suppressed effectively.

Dual buck-boost converter with single inductor

Abstract: A dual output buck-boost power converter operates with a single inductor to achieve high efficiency with automatic or inherent load balancing. Switches associated with the opposite polarity outputs are driven based on feedback signals, with one feedback signal being a reference voltage and another feedback signal being related to an opposite polarity output. The opposite polarity feedback signal is provided to a comparator with a reversed polarity to achieve a simple balanced control that maintains polarity outputs. The power converter delivers power to each output with each switching cycle and uses a single inductor to achieve high efficiency performance.

Zero-current-switching switched-capacitor bidirectional DC-DC converter

Abstract: The proposed zero-current-switching switched-capacitor quasi-resonant DC-DC converter is a new type of bidirectional power flow control conversion scheme. It possesses the conventional features of resonant switched-capacitor converters: low weight, small volume, high efficiency, low EMI emission and current stress. A zero-current-switching switched-capacitor step-up/step-down bidirectional converter is presented that can improve the current stress problem during bidirectional power flow control processing. It can provide a high voltage conversion ratio using four power MOSFET main switches, a set of switched capacitors and a small resonant inductor. The converter operating principle of the proposed bidirectional power conversion scheme is described in detail with circuit model analysis. Simulation and experiment are carried out to verify the concept and performance of the proposed bidirectional DC-DC converter.

Analysis of Double Step-Down Two-Phase Buck Converter for VRM

Abstract: A novel two-phase buck converter suitable to apply the power supplies for MPU is proposed Compared to conventional two-phase buck converter, the proposed converter essentially has double step-down ratio as Eo/Ei = D/2 and high efficiency is realized by reducing the switching loss of the switching elements In addition the current ripple of the output smoothing capacitor is improved to the same value as that of conventional four-phase buck converter Moreover the current unbalance between two inductors in each phase is removed automatically without any current sensing means The above fine characteristics are simply achieved an additional capacitor

Integration of planar transformer and/or planar inductor with power switches in power converter

Abstract: A power converter integrates at least one planar transformer (T1, T2) comprising a multi-layer transformer substrate and/or at least one planar inductor comprising a multi-layer inductor substrate with a number of power semiconductor switches (S7-S10) physically and thermally coupled to a heat sink via one or more multi-layer switch substrates.

Modeling of capacitor impedance in switching converters

Abstract: Switched capacitor (SC) converters are gaining acceptance as alternatives to traditional, inductor-based switching power converters. Proper design of SC converters requires an understanding of all loss sources and their impacts on circuit operation. In the present work, an equivalent resistance method is developed for analysis, and equivalent resistance formulae are presented for various modes of operation. Quasiresonant converters are explored and compared to standard SC converters. Comparisons to inductor-based switching power converters are made. A number of capacitor technologies are evaluated and compared for applications to both SC converters and inductor-based converters. The resulting model can be used to accurately predict and optimize converter performance in the design phase.