Compact Inductor Research Articles

Design and Assessment of a Planar Inductor for a 32-kW High Power Density DC–DC Converter

A uniform-flux inductor design strategy is described in this paper to improve the gravimetric power density of the common inductor of a 32 kW, 350 V dual-interleaved Buck-Boost DC-DC converter. The strategy consists of an unusual, enclosed winding arrangement that virtually distributes the core magnetic flux density outcoming in a more compact inductor. The resultant common inductor weight and volume are reduced by 41 % and 24 % respectively, the power density being increased to 7.9 kW/kg. A COMSOL numerical prediction confirms almost uniform flux density distribution along the magnetic core axes. Estimation of the inductance, power losses and thermal behaviour are also analysed. Construction assessment is described for a 7 μH, 150 kHz, 180 A inductor, which is experimentally verified in a 350 V, 32 kW prototype. The experiments reveal that the built uniform-flux inductor properly operates ensuring both electrical and thermal stability.

An All-1.8-V-Switch Hybrid Buck–Boost Converter for Li-Battery-Operated PMICs Achieving 95.63% Peak Efficiency Using a 288-m DCR Inductor

In this article, a hybrid step-up/down converter is presented with improved efficiency, smaller form factor, and enhanced reliability for Li-ion-battery-operated power management integrated circuits. Utilizing a hybrid structure with one inductor and two flying capacitors, the dual-path buck–boost (DPBB) converter reduces the average inductor current, switch currents, and the required blocking voltage for the power switches. To support a mid-3-V output from a Li-ion battery, the converter can be realized using 1.8-V rated devices, solely. In addition, the DPBB facilitates a continuous input and output current delivery, thus improving the reliability of the converter significantly. Besides, leveraging the Li-ion battery charge profile, the topology provides an optimal performance during downconversion, in which the converter operates for most of its usage time. With reduced inductor current and smaller voltage rated switches, a more compact inductor with a large dc resistance (DCR) can be used to maintain similar efficiency, which, in turn, helps reduce the converter board space and associated manufacturing cost. Fabricated in a 180-nm BCD technology, the prototype achieves a peak efficiency of 95.63% even for a large 288-m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Omega$</tex-math></inline-formula> inductor DCR with an output ripple below 20 mV for a load current up to 700 mA.

A 27-dBm, 0.92-GHz CMOS Power Amplifier With Mode Switching and a High-Q Compact Inductor (HQCI) Achieving a 30% Back-Off PAE

This brief reports a 0.92-GHz two-stage power amplifier (PA) in 130-nm CMOS process with improved back-off power efficiency and linearity. The two key techniques are: a switching mechanism for adaptive device sizing of the power stage, and a high-Q compact inductor (HQCI). The PA is designed to operate in low power (LP) mode and high power (HP) mode by using an NMOS pass transistor as a switch. The PA measures a peak output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{\mathrm{ out}}$ </tex-math></inline-formula> ) of 27 dBm with a peak power added efficiency (PAE) of 44%. The maximum linear output power reaches 21.5 dBm thanks to our unique HQCI-based output-matching network. At the back-off output power, a 10% increment in PAE is achieved by switching the size of the power stage with the MOS switch. Maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{P}_{\mathrm{ out}}$ </tex-math></inline-formula> of 21.5 dBm is measured below −30 dBc ACLR and 4% EVM for the 16-QAM/20-MHz input modulated signal. The PA has an overall chip size of 1.382 x 1.425 mm2.

Design of an universal source for semi-automatic ac welding and induction heating

This paper proposes a circuit solution and a power source control algorithm for semi-automatic AC welding with improved energy and weight-size characteristics. A distinctive feature of the designed source is the absence of an input rectifier: welding is carried out with a high-frequency alternating current. That has made it possible to significantly reduce power losses in the source, as well as provide the possibility of implementing induction heating by connecting an inductor to the source output. Another distinctive feature of the designed source is an increased power factor and a reduced level of higher harmonics of the current consumed. The power factor of the described source reaches 0.94 against 0.5÷0.7 for sources equipped with a conventional rectifier with capacitive smoothing. The designed source's composition includes a power supply system for the wire feed drive with speed stabilization due to positive feedback on the motor current. That has made it possible to ensure the stable operation of the drive in a wide range of speeds. A model has also been developed of a flux wire welding torch containing a feed drive and a coil with a wire (up to 100 mm in diameter), placed, in order to reduce the size, in the handle of the torch. In addition to the welding function, the source makes it possible to solve the tasks related to induction heating and/or hardening of small parts; to that end, a compact inductor is connected to its output. Tests of the source showed the feasibility of the proposed ideas and circuit solutions. The dimensions of the source are 190×107×65 mm; weight, 1.4 kg; output current, up to 120 A. The proposed technical solution enables the construction of small-sized, lightweight, universal, easy-to-use power supplies for semi-automatic welding with the option of induction heating

Design of a Compact, Robust High-Current Inductor for Pulsed Power Applications

This article describes a high-current, pulse power inductor design to achieve compactness, robustness, and enhanced energy density. Conventional pulse power inductor designs focus on containing the strong expansive Lorentz forces on the inductor coil using bulky external housing. The novelty of the present design is the use of a high-conductivity metallic enclosure placed coaxially around the inductor coil which modifies the magnetic field distribution in such a way that the force experienced by the inductor coil is compressive, rather than expansive. Hence, the Lorentz forces on the inductor coil are contained using a strong inner coil former used for holding the coil, thus eliminating the need for a strong external housing. This leads to a more compact inductor design. This inductor design is studied extensively using COMSOL Multiphysics 5.3 and Opera 18R2 for validation of design concept. Based on these simulations, inductors with inductance of $2~\mu \text{H}$ and energy density of 5 kJ/l are fabricated and tested successfully on an experimental setup to get a pulsed current of magnitude 250 kA and rise time 82 $\mu \text{s}$ with two such inductors connected in parallel as load. Based on the experimental experience and confidence gained on these inductors, a design concept of more compact inductor has also been proposed.

A 2.7-mW 1.36–1.86-GHz LC-VCO With a FOM of 202 dBc/Hz Enabled by a 26%-Size-Reduced Nano-Particle-Magnetic-Enhanced Inductor

This paper reports the first LC voltage-controlled oscillator (LC-VCO) in CMOS utilizing a novel nontraditional compact inductor with integrated vertical nano particles magnetic core (Ni-Zn-Cu) to improve the figure-of-merit (FOM) of the VCO circuit. The new magnetic-enhanced inductor, fabricated in an integrated-circuit back-end using a CMOS-compatible process, improves inductance density ( L-density) and quality factor ( Q-factor) up to 7 GHz. A 1.36-1.86-GHz VCO with a nano-ferrite-integrated inductor was fabricated in a 180-nm RF CMOS. Measurements show that the magnetic-cored inductor improves the L-density and Q-factor by 49.8% and 59.2% at 1.8 GHz, respectively, while reducing the size by 26%. The VCO achieves reduced power consumption of 2.7 mW at a 1.8-V supply, low phase noise of less than -121, and -126 dBc/Hz at 100-kHz and 1-MHz frequencies offset, and a high FOM of 202 dBc/Hz. This prototype VCO demonstrates that the new vertical-nano-magnetic-cored inductor technology is a potential solution to high-performance low-cost compact RF systems-on-chip.

LC-based clock generator for high-frequency, continuous-time, ΔΣ ADCs

This paper presents the design and experimental results of a clock generator for high-frequency, continuous-time, converters. The circuit was fabricated in a -V, -nm CMOS technology along with two modulators intended for the digitisation of UWB signals. The clock generator is based on a PLL frequency synthesiser with a low phase noise LC Voltage-controlled oscillatror (VCO). This kind of oscillator achieves the required low jitter specification with a substantial lower power consumption than a conventional ring VCO. In order to save die area, the VCO was made to operate at four times the desired clock frequency of MHz, and a compact multi-layer inductor was used. A system clock with a cycle-to-cycle jitter of only of its period is obtained. The total circuit area is and the resulting power consumption is .

Microstrip Symmetrical Twin-Spiral Inductor Resonator Filter for UWB Applications

This paper presents a novel microstrip type double symmetrical twin-square-shaped spiral inductor resonator bandpass filter for ultra wideband (UWB) applications. The power transformation from port to port is achieved by utilizing electromagnetic coupling phenomena between two symmetrically opposite mounted twin-spiral inductors. The inductor resonator filter is based on self-resonance frequency of the symmetrical spiral inductors and electromagnetic coupling between them. The two twin-symmetrical spiral inductors are connected with stepped-impedance-resonator (SIR) ports for 50 Ω impedance matching. This microstrip symmetrical twin-spiral inductor resonator type filter is resonated at 5.1 GHz frequency. In the experiment, the insertion loss (S21) and the return loss (S11) were measured −0.34 and −26.8 dB, respectively. The proposed compact inductor resonator filter exhibits a significant size reduction compared to existing distributed filter topologies and it can be used for terrestrial microwave UWB applications.

A Wideband Compact Model for Integrated Inductors

This letter presents a compact inductor model that is accurate beyond the inductor's self-resonance frequency. The inductor is represented as a short-circuited transmission line, whose impedance is a hyperbolic tangent function. This function is expanded to its third-order continued fractions approximation. The approximation results in a compact equivalent circuit model with frequency independent parameters that can be extracted directly from S-parameter measurements. No optimization is necessary in this process. The developed compact wideband inductor model is extremely useful for accurate transient and harmonic balance simulations where out of band response is important

Low-cost compact spiral inductor resonator filters for system-in-a-package

In this paper, compact resonator filters embedded in package substrate are proposed using compact spiral resonators. The design is based on the self-resonance frequency of the spiral inductors and electromagnetic coupling effects among resonators. The filters were built and measurement results have good agreement with the simulation data. The proposed filter design technique is generalized and can be implemented in different multilayer arrangements. These new compact inductor resonator filters exhibit a significant size reduction compared to existing distributed filter topologies. The inductor resonator filter designs are based on full-wave electromagnetic analysis. A lumped element equivalent circuit based on the simulated data of the filter is also derived for integration in SPICE-type simulators. The compactness of the newly developed bandpass filter makes the design and integration of bandpass filters attractive for further development and applications in system-in-a-package (SIP) applications.

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

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.

Design and optimization of CMOS RF power amplifiers

A CMOS radio-frequency power amplifier including on-chip matching networks has been designed in a 0.6-/spl mu/m n-well triple-metal digital CMOS process, and optimized using a simulated-annealing-based custom computer-aided design tool. A compact inductor model enables the incorporation of parasitics as an integral part of the parasitic-aware design and CAD optimization; low-Q metal3 spiral inductors are used in the input and output matching networks. A 3-V 85-mW balanced fully integrated Class-C power amplifier with a measured drain efficiency of 55% at 900 MHz has been designed, optimized, integrated, and tested.