Showing papers on "Inductor published in 2008"

Switched-Capacitor/Switched-Inductor Structures for Getting Transformerless Hybrid DC–DC PWM Converters

Abstract: A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.

The elusive memristor: properties of basic electrical circuits

Abstract: We present a tutorial on the properties of the new ideal circuit element, a memristor. By definition, a memristor M relates the charge q and the magnetic flux $\phi$ in a circuit, and complements a resistor R, a capacitor C, and an inductor L as an ingredient of ideal electrical circuits. The properties of these three elements and their circuits are a part of the standard curricula. The existence of the memristor as the fourth ideal circuit element was predicted in 1971 based on symmetry arguments, but was clearly experimentally demonstrated just this year. We present the properties of a single memristor, memristors in series and parallel, as well as ideal memristor-capacitor (MC), memristor-inductor (ML), and memristor-capacitor-inductor (MCL) circuits. We find that the memristor has hysteretic current-voltage characteristics. We show that the ideal MC (ML) circuit undergoes non-exponential charge (current) decay with two time-scales, and that by switching the polarity of the capacitor, an ideal MCL circuit can be tuned from overdamped to underdamped. We present simple models which show that these unusual properties are closely related to the memristor's internal dynamics. This tutorial complements the pedagogy of ideal circuit elements (R,C, and L) and the properties of their circuits.

Vibration energy harvesting by magnetostrictive material

Abstract: A new class of vibration energy harvester based on magnetostrictive material (MsM), Metglas 2605SC, is designed, developed and tested. It contains two submodules: an MsM harvesting device and an energy harvesting circuit. Compared to piezoelectric materials, the Metglas 2605SC offers advantages including higher energy conversion efficiency, longer life cycles, lack of depolarization and higher flexibility to survive in strong ambient vibrations. To enhance the energy conversion efficiency and alleviate the need of a bias magnetic field, Metglas ribbons are transversely annealed by a strong magnetic field along their width direction. To analyze the MsM harvesting device a generalized electromechanical circuit model is derived from Hamilton’s principle in conjunction with the normal mode superposition method based on Euler‐Bernoulli beam theory. The MsM harvesting device is equivalent to an electromechanical gyrator in series with an inductor. In addition, the proposed model can be readily extended to a more practical case of a cantilever beam element with a tip mass. The energy harvesting circuit, which interfaces with a wireless sensor and accumulates the harvested energy into an ultracapacitor, is designed on a printed circuit board (PCB) with plane dimension 25 mm × 35 mm. It mainly consists of a voltage quadrupler, a 3 F ultracapacitor and a smart regulator. The output DC voltage from the PCB can be adjusted within 2.0‐5.5 V. In experiments, the maximum output power and power density on the resistor can reach 200 μW and 900 μ Wc m −3 , respectively, at a low frequency of 58 Hz. For a working prototype under a vibration with resonance frequency of 1.1 kHz and peak acceleration of 8.06 m s −2 (0.82 g), the average power and power density during charging the ultracapacitor can achieve 576 μ Wa nd 606 μ Wc m −3 , respectively, which compete favorably with piezoelectric vibration energy harvesters. (Some figures in this article are in colour only in the electronic version)

Boost Converter With Coupled Inductors and Buck–Boost Type of Active Clamp

Abstract: This paper proposes a boost converter with coupled inductors and a buck-boost type of active clamp. In the converter, the active-clamp circuit is used to eliminate the voltage spike that is induced by the trapped energy in the leakage inductor of the coupled inductors. The active switch in the converter can still sustain a proper duty ratio 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 low-input-voltage applications, such as fuel cell and battery power conversion.

Shunt Active-Power-Filter Topology Based on Parallel Interleaved Inverters

Abstract: In this paper, an interleaved active-power-filter concept with reduced size of passive components is discussed. The topology is composed of two pulsewidth-modulation interleaved voltage-source inverters connected together on the ac line and sharing the same dc-link capacitor. The advantages of the proposed approach are as follows: 1. significant reduction in the linkage inductors' size by decreasing the line-current ripple due to the interleaving; 2. reduction of the switching stress in the dc-link capacitor, due to the shared connection; and 3. more accurate compensation for high-power applications, because the power sharing allows one to use a higher switching frequency in each inverter. This paper analyzes the design of the passive components and gives a practical and low-cost solution for the minimization of the circulation currents between the inverters, by using common-mode coils. Several simulation results are discussed, and experimental results with a three-phase 10-kVA 400-V unit are obtained to validate the theoretical analysis.

A High-Efficiency DC–DC Converter Using 2 nH Integrated Inductors

Abstract: Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 muH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9 % for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.

An optimized self-powered switching circuit for non-linear energy harvesting with low voltage output

Abstract: Harvesting energy from environmental sources has been of particular interest these last few years. Microgenerators that can power electronic systems are a solution for the conception of autonomous, wireless devices. They allow the removal of bulky and costly wiring, as well as complex maintenance and environmental issues for battery-powered systems. In particular, using piezoelectric generators for converting vibrational energy to electrical energy is an intensively investigated field. In this domain, it has been shown that the harvested energy can be greatly improved by the use of an original non-linear treatment of the piezoelectric voltage called SSHI (Synchronized Switch Harvesting on Inductor), which consists in intermittently switching the piezoelectric element on a resonant electrical network for a very short time. However, the integration of miniaturized microgenerators with low voltage output (e.g. MEMS microgenerators) has not been widely studied. In the case of low voltage output, the losses introduced by voltage gaps of discrete components such as diodes or transistors can no longer be neglected. Therefore the purpose of this paper is to propose a model that takes into account such losses as well as a new architecture for the SSHI energy harvesting circuit that limits such losses in the harvesting process. While most of the study uses an externally powered microcontroller for the non-linear treatment, this circuit is fully self-powered, thus providing an enhanced autonomous microgenerator. In particular this circuit aims at limiting the effect of non-linear components with a voltage gap such as diodes. It is shown both theoretically and experimentally that the harvested power can be significantly increased using such a circuit. In particular, experimental measurements performed on a cantilever beam show that the circuit allows a 160% increase of the harvested power compared to a standard energy harvesting circuit, while the classical implementation of the SSHI shows an increase of only 100% of the output power in the classical case.

Long range low frequency resonator and materials

Abstract: Transmission of power at low frequencies, e.g. less than 1 MHz. The power can be transmitted in various ways, using different structures included stranded wire such as Litz wire. The inductor can also use cores of ferrites for example. Passive repeaters can also be used.

Coherent thermal emission by excitation of magnetic polaritons between periodic strips and a metallic film.

Abstract: The present paper theoretically demonstrates coherent thermal emission in the infrared region by exciting magnetic polaritons between metallic gratings and an opaque metallic film, separated by a dielectric spacer. The coupling of the metallic strips and the film induces a magnetic response that is characterized by a negative permeability and positive permittivity. On the other hand, the metallic film intrinsically exhibits a negative permittivity and positive permeability in the near infrared. This artificial structure is equivalent to a pair of single-negative materials. By exciting surface magnetic polaritons, large emissivity peaks can be achieved at the resonance frequencies and are almost independent of the emission angle. The resonance frequency of the magnetic response can be predicted by an analogy to an inductor and capacitor circuit. The proposed structure can be easily constructed using micro/nanofabrication.

Operation Modes and Characteristics of the Z-Source Inverter With Small Inductance or Low Power Factor

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

A Family of Interleaved DC–DC Converters DeducedFrom a Basic Cell With Winding-Cross-CoupledInductors (WCCIs) for High Step-Upor Step-Down Conversions

Abstract: A basic cell with winding-cross-coupled inductors (WCCIs) and interleaved structure is proposed in this paper. A family of DC-DC converters is deduced from the proposed basic cell, which is suitable for high step-up or step-down conversions. The passive-lossless clamp scheme is derived from the active clamp scheme to recycle the leakage energy and to suppress the voltage spikes caused by the leakage inductance. The advantages of the derived interleaved boost converter with WCCIs and passive-lossless clamp circuits are analyzed as an example. The voltage gain is extended and the switch voltage stress is reduced to minimize the conduction losses. The rectifier reverse-recovery problem is alleviated by the leakage inductance. Furthermore, a series of DC-DC converters with WCCIs and passive-lossless clamp circuits are summarized for high efficiency, high power and high step-up or step-down applications. A clear picture is made in this paper on the general law and structure of the WCCIs for DC-DC conversion in high step-up or step-down applications. At last, the simulated and experimental results of a 1 kW 40 V-to-380 V prototype with WCCIs and passive-lossless clamp circuits verify the significant improvements in performance.

Mutual inductance calculation of movable planar coils on parallel surfaces

Abstract: Recent developments of the wireless battery charging platform have prompted requirements to investigate the mutual inductance between a movable planar coil and the fixed planar coil on the charging platform. The wireless battery charging platform must allow the load to be placed anywhere on the charging surface. Therefore, the relative position between the movable energy-receiving coil and the energy-transmitting coils on the charging platform must be flexible. In this paper, an extended formula is proposed for the mutual inductance calculation for two coaxial or noncoaxial planar spiral windings sandwiched between two double-layer substrates. It can quickly determine the mutual coupling of two planar windings that can have different relative positions and distance between them. This new calculation method provides a new and useful tool for determining the mutual inductance of a movable planar coil and the fixed planar coil on the wireless battery charging platform. The theory has been favorably tested and compared with practical measurements and also with finite-element analysis.

Digital Control of Single-Inductor Multiple-Output Step-Down DC–DC Converters in CCM

Abstract: This paper investigates the application of digital control for non-isolated single-inductor multiple-output step-down dc-dc converters operating in continuous-conduction mode. The accurate and independent control of each output requires a sophisticated digital control architecture so as to minimize the cross-regulation problem. The adopted control includes a separate regulation for common-mode and differential-mode output voltages. Due to the differential-mode control loop dependence on the load current, a variable-gain functional block has been investigated; this provision keeps the differential-mode loop gain constant under different load conditions. Moreover, a nonlinear evaluation of the common-mode voltage has been investigated in order to improve the system dynamic response to asymmetrical load changes. Even if aimed at an integrated solution, experimental verifications have been performed using discrete components, implementing the digital control in a field-programmable gate array. Simulation results on a three-output converter and experimental results on dual-output converter (Vin = 2.5 4divide5 V, Vo1 = Vo2 = 0.9divide1.5 V, and Ioperp = Io2 = 0 4divide0.6 A) confirm the proposed analysis.

Voltage-Balancing Circuit Based on a Resonant Switched-Capacitor Converter for Multilevel Inverters

Abstract: This paper proposes a new voltage-balancing circuit for the split dc voltages in a diode-clamped five-level inverter. The proposed circuit is based on a resonant switched-capacitor converter (RSCC), which consists of two half-bridge inverters, a resonant inductor, and a resonant capacitor. A new phase-shift control of the RSCC is proposed to improve voltage-balancing performance. As a result, it is possible to reduce the inductor to one tenth in volume as compared to a conventional voltage-balancing circuit based on a buck-boost converter. Experimental results are shown to verify the viability of the RSCC-based voltage-balancing circuit.

Zero-Voltage-Switching DC–DC Converters With Synchronous Rectifiers

Abstract: Active resonant tank (ART) cells are proposed in this paper to achieve zero-voltage-switching (ZVS) and eliminate body-diode conduction in DC-DC converters with synchronous rectifiers (SRs). In low-output-voltage DC-DC converters, SRs are widely utilized to reduce rectifier conduction loss and improve converter efficiency. However, during switches' transition, SRs' parasitic body diodes unavoidably carry load current, which decreases conversion efficiency because voltage drop across body diodes is much higher than that across SRs. Moreover, body diodes' reverse recovery leads to increased switching losses and electromagnetic interference. With the proposed cells of an ART, the body diode conduction of the SR is eliminated during the switching transition from a SR to an active switch, and thus body diode reverse-recovery-related switching and ringing losses are saved. An ART cell consists of a LC resonant tank and an auxiliary switch. A resonant tank cell is charged in a resonant manner and energy is stored in the capacitor of the tank. Prior to a switching transition from a SR to an active switch, the energy stored in the tank capacitor is released and converted to inductor current, which forces the SR current changes direction to avoid conduction of the body diode and related reverse recovery when the SR turns off. Moreover, at the help of energy released from the ART, the active switch's junction capacitance is discharged, which allows the active switch turns on at ZVS. Since energy commutation occurs only during switching transition, conduction loss in the ART cell is limited. Moreover, the auxiliary switch turns off at ZVS and the SR operates at ZVS. The concept of ART cells is generally introduced and detailed analysis is presented based on a synchronous buck converter. Experimental results show the proposed ART cell improves conversion efficiency due to the reduced switching loss, body diodes' conduction, and reverse-recovery losses.

A High-Efficiency DC-DC Converter Using 2 nH Integrated Inductors

Abstract: Historically, buck converters have relied on high-Q inductors on the order of 1 to 100 μH to achieve a high efficiency. Unfortunately, on-chip inductors are physically large and have poor series resistances, which result in low-efficiency converters. To mitigate this problem, on-chip magnetic coupling is exploited in the proposed stacked interleaved topology to enable the use of small (2 nH) on-chip inductors in a high-efficiency buck converter. The dramatic decrease in the inductance value is made possible by the unique bridge timing of the stacked design that causes magnetic coupling to boost the converter's efficiency by reducing the current ripple in each inductor. The magnetic coupling is realized by stacking the two inductors on top of one another, which not only lowers the required inductance, but also reduces the chip area consumed by the two inductors. The measured conversion efficiency for the prototype circuit, implemented in a 130-nm CMOS technology, shows more than a 15% efficiency improvement over a linear converter for low output voltages rising to a peak efficiency of 77.9% for a 0.9 V output. These efficiencies are comparable to converters implemented with higher Q inductors, validating that the proposed techniques enable high-efficiency converters to be realized with small on-chip inductors.

The Blixer , a Wideband Balun-LNA-I/Q-Mixer Topology

Abstract: This paper proposes to merge an I/Q current-commutating mixer with a noise-canceling balun-LNA. To realize a high bandwidth, the real part of the impedance of all RF nodes is kept low, and the voltage gain is not created at RF but in baseband where capacitive loading is no problem. Thus a high RF bandwidth is achieved without using inductors for bandwidth extension. By using an I/Q mixer with 25% duty-cycle LO waveform the output IF currents have also 25% duty-cycle, causing 2 times smaller DC-voltage drop after IF filtering. This allows for a 2 times increase in the impedance level of the IF filter, rendering more voltage gain for the same supply headroom. The implemented balun-LNA-I/Q-mixer topology achieves > 18 dB conversion gain, a flat noise figure < 5.5 dB from 500 MHz to 7 GHz, IIP2 = +20 dBm and IIP3 = -3 dBm. The core circuit consumes only 16 mW from a 1.2 V supply voltage and occupies less than 0.01 mm2 in 65 nm CMOS.

Design of Wide Tuning-Range CMOS VCOs Using Switched Coupled-Inductors

Abstract: Two designs of voltage-controlled oscillators (VCOs) with mutually coupled and switched inductors are presented in this paper to demonstrate that the tuning range of an LC VCO can be improved with only a small increase in phase noise and die area in a standard digital CMOS process. Particular attention is given to the layout of the inductors to maintain Q across the tuning range. In addition, different capacitive coarse-tuning methods are compared based on simulated and measured data obtained from test structures. Implemented in a 90 nm digital CMOS process, a VCO with two extra coupled inductors achieves a 61.9% tuning range with an 11.75 GHz center frequency while dissipating 7.7 mW from a 1.2 V supply. This VCO has a measured phase noise of -106 dBc/Hz at 1 MHz offset from the center frequency resulting in a higher figure-of-merit than other recently published VCOs with similar operating frequencies. In addition, the area overhead is only 30% compared to a conventional LC VCO with a single inductor.

Fabrication and Analysis of High-Performance Integrated Solenoid Inductor With Magnetic Core

Abstract: Integrated solenoid inductors with magnetic core were fabricated and analyzed. An inductance above 70 nH was achieved while keeping the coil resistance below 1 Omega and the device area below 1 mm2 using a solenoid design with a single magnetic layer. The inductance of the magnetic inductor was more than 30 times that of the air core inductor of the identical geometry, and the quality factor of the magnetic inductor was >5. Novel inductor designs and the scalability were also examined, and an inductance density higher than 200 nH/mm2 was obtained. The measured device properties and engineering tradeoffs were well explained by analytical models we developed.

A Current Source Gate Driver Achieving Switching Loss Savings and Gate Energy Recovery at 1-MHz

Abstract: In this paper, a new current source gate drive circuit is proposed for power MOSFETs. The proposed circuit achieves quick turn on and turn off transition times to reduce switching loss and conduction loss in power MOSFETs. In addition, it can recover a portion of the CV gate energy normally dissipated in a conventional driver. The circuit consists of four controlled switches and a small inductor (typically 100 nH or less). The current through the inductor is discontinuous in order to minimize circulating current conduction loss. This also allows the driver to operate effectively over a wide range of duty cycles with constant peak current-a significant advantage for many applications since turn on and turn off times do not vary with the operating point. Experimental results are presented for the proposed driver operating in a boost converter at 1 MHz, 5 V input, 10 V/5 A output. At 5 V gate drive, a 2.9% efficiency improvement is achieved representing a loss savings of 24.8% in comparison to a conventional driver.

Study of the Effects of Inductor Nonlinear Behavior on the Performance of Current Controllers for Single-Phase PV Grid Converters

Abstract: Resonant and repetitive controllers are well suited for single-phase grid-connected inverters due to their optimum tracking and harmonic rejection capability. In particular, in this paper, their application for single-phase photovoltaic systems is considered. The effects of nonlinear inductance on the performance of current controllers designed to track periodic signals and/or to compensate periodic disturbances are investigated. When the inductance has a nonlinear behavior, a distorted current waveform is produced. Two different nonlinearities have been considered: saturation for high currents and a light nonlinearity, which occurs in the first portion of the magnetization curve, for low currents. A current-dependent model of the nonlinear inductance has been developed. It is mathematically based on the Volterra-series expansion, and it allows us to prove how the harmonic compensation provided by resonant and repetitive controllers can also mitigate the effects of the inductance saturation. This result is the main contribution of this paper, and it is also substantiated with experimental evidence. Moreover, the repetitive controller is able to comply with the harmonic limits reported in IEEE 1547 and IEC 61727, even in very hard saturation conditions.

A New Phase-Shifted Full-Bridge Converter With Voltage-Doubler-Type Rectifier for High-Efficiency PDP Sustaining Power Module

Abstract: A new phase-shifted full-bridge converter with a voltage-doubler-type rectifier for a high-efficiency power-sustaining module of a plasma display panel is proposed in this paper. The proposed converter employs a voltage-doubler rectifier without an output inductor. Since it does not have an output inductor, the voltage stresses of the rectifier diodes can be clamped at the output voltage level. Thus, since no dissipative resistor-capacitor snubber for rectifier diodes is needed, high-efficiency low-noise output voltage can be realized. Due to the elimination of the large output inductor, it features simpler structure, lower cost, smaller mass, and lighter weight. Furthermore, the proposed converter has wide zero-voltage-switching ranges of lagging leg switches with low current stresses of the primary power switches by using the magnetizing current. In addition, the resonance between the leakage inductor of the transformer and the rectifier capacitors can reduce the current stresses of the rectifier diodes and conduction losses. In this paper, the operational principles, analysis, design considerations, and experimental results are presented.

Novel DC-DC Multilevel Boost Converter

Abstract: This paper proposes a new DC-DC converter. The DC-DC multilevel boost converter, based on one inductor, one switch, 2N-1 diodes and 2N-1 capacitor, for N levels plus the reference (total N+1 levels), is a boost converter able to control and maintain the same voltage in all the Nx output levels, and able to control the input current. This converter is based on the multilevel converters principle, and it is proposed to be used as DC-link in applications where several controlled voltage levels are needed with self balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters. Used to feed a multilevel inverter, the proposed topology achieves a self voltage balancing; experimental results prove the principle of the proposition.

Modelling of lossy coils using fractional derivatives

Abstract: Coils exposed to eddy current and hysteresis losses are conventionally described by an inductance with equivalent core-loss resistance connected in parallel. The value of the equivalent core-loss resistance depends on the working frequency and the external wiring. Thus the model is less than satisfactory. The authors propose to describe loss inductance using fractional derivatives containing both a loss term and a storage term.After introducing the theory of fractional derivatives, the operating mode of the fractional coil model is explained by the example of an RLC oscillating circuit. Subsequent measurements of a series resonant circuit with a lossy coil impressively confirm the theoretical model with regard to both the frequency and time domains.

High Conversion Ratio DC–DC Converters With Reduced Switch Stress

Abstract: In this paper, a new class of single-switch nonisolated high step-up DC-DC converters with simple topologies is proposed. The proposed topologies utilize a hybrid switched capacitor technique for providing a high voltage gain without extreme switch duty cycle and yet enabling the use of a lower voltage and RDS-ON MOSFET switch so as to reduce cost, switch conduction and turn-on losses. Other advantages of the proposed topologies include: continuous input/output current, simple structure and control. The principle of operation in continuous conduction mode and discontinuous inductor current mode are analyzed. Experimental results obtained on a 45-W prototype are also presented.

Integrated on-chip inductors using magnetic material (invited)

Abstract: On-chip inductors with magnetic material are integrated into both advanced 130 and 90 nm complementary metal-oxide semiconductor processes. The inductors use aluminum or copper metallization and amorphous CoZrTa magnetic material. Increases in inductance of up to 28 times corresponding to inductance densities of up to 1.3 μ H / mm 2 were obtained, significantly greater than prior values for on-chip inductors. With such improvements, the effects of eddy currents, skin effect, and proximity effect become clearly visible at higher frequencies. The CoZrTa was chosen for its good combination of high permeability, good high-temperature stability ( > 250 ° C ) , high saturation magnetization, low magnetostriction, high resistivity, minimal hysteretic loss, and compatibility with silicon technology. The CoZrTa alloy can operate at frequencies up to 9.8 GHz , but trade-offs exist between frequency, inductance, and quality factor. The effects of increasing the magnetic thickness on the permeability spectra were measured and modeled. The inductors use magnetic vias and elongated structures to take advantage of the uniaxial magnetic anisotropy. Techniques are presented to extract a sheet inductance and examine the effects of magnetic vias on the inductors. The inductors with thick copper and thicker magnetic films have resistances as low as 0.04 Ω , and quality factors up to 8 at frequencies as low as 40 MHz.

Self-tuning digital current estimator for low-power switching converters

Abstract: An inductor current estimator suitable for low-power digitally controlled switch-mode power supplies (SMPS) is introduced. The estimation of the average current value over one switching cycle is based on the analog-to-digital conversion of the inductor voltage and consequent adaptive signal filtering. The adaptive filter is used to compensate for variations of the inductance and series equivalent resistance affecting accuracy of the estimation. Based on the response to an intentionally introduced and known current step, the filter tunes its own parameters such that a fast and accurate estimation is obtained. A practical realization of the estimator resulting in a modest increase in digital controller complexity is shown. Besides a simple digital IIR filter and a load step circuit, it only requires a slow analog-to-digital converter for the input voltage measurement. The estimator is tested on a 6.5 V to 1.5 V, 15 W, digitally-controlled buck converter prototype. The results show that between 20% and 100% of the maximum output load the estimator has accuracy better than 10% and one switching cycle response time.

Evaluation of magnetic materials for very high frequency power applications

Abstract: This paper investigates the loss characteristics of several commercial rf magnetic materials forpower conversion applications in the 10 MHz to 100 MHz range. A measurement method is proposed that provides a direct measurement of inductor quality factor QL as a function of inductor current at rf frequencies, and enables indirect calculation of core loss as a function of flux density. Possible sources of error in measurement and calculation are evaluated and addressed. The proposed method is used to identify loss characteristics of different commercial rf magnetic core materials. The loss characteristics of these materials, which have not previously been available, are illustrated and compared in tables and figures. The results of this paper are thus useful for design of magnetic components for very high frequency applications.

A Novel Configuration for a Cascade Inverter-Based Dynamic Voltage Restorer With Reduced Energy Storage Requirements

Abstract: This paper introduces a new configuration for a cascade (H-bridge) converter-based dynamic voltage regulator in which the basic cascade converter is supplemented with a shunt thyristor-switched inductor. The proposed topology is shown to possess the ability of mitigating a severe and long duration voltage sag with a significantly smaller energy demand from the cascade converter. A suitable control system is designed, and the operation of the new device is analyzed using electromagnetic transients simulation as well as mathematical analysis. Simulation and experimental results are presented to demonstrate the feasibility and the practicality of the proposed novel dynamic voltage restorer topology.