Ferrite Core Transformer Research Articles

Design a High Frequency Power Inverter Using Ferrite-Core Transformer for Ohmic Heating of Liquid Conducting System

Design a High Frequency Power Inverter Using Ferrite-Core Transformer for Ohmic Heating of Liquid Conducting System

Electrical Design of a Portable Pure Sine Wave Inverter Using Ferrite Core Transformer and Double Stage Technique

The size of the iron core transformer in an inverter is large and heavy because it has more conductor turns and works at low frequencies. In contrast, ferrite core transformers are designed to work at high frequencies, so the number of turns of the conductor is less, and the transformer size is relatively small and light. Device portability is a significant challenge in designing high-power inverters. This research uses a ferrite core transformer to design a portable pure sine wave inverter. A two-stage technique is proposed in designing the inverter so that the dc-link voltage and capacitor size can be flexibly selected, and the device size can be compacted. The design consists of two stages. First, a circuit to generate a 400-Volt DC voltage is designed using IC SG3525, a MOSFET power amplifier, and a ferrite core step-up transformer. Second, a pure sine wave generator circuit is constructed using an EGS002 module, MOSFETs, and a filter circuit. Experiments are performed by measuring the output voltage, monitoring power and frequency, and observing the waveform with an oscilloscope. The results reveal that the designed inverter can generate a 220-volt pure sine wave output, a maximum power of 500 Watts, a frequency of 50 Hz, and an efficiency between 91.4% to 98.1%.

Self-Operating Flyback Converter for Boosting Ultra-Low Voltage of Thermoelectric Power Generator for IoT Applications

This article presents a novel self-operating flyback converter to boost the ultra-low voltage produced by thermoelectric power generator (TEG). The proposed converter uses dual transformer, one for low-voltage startup and other to extract power from TEG. The use of separate transformer provides high-voltage transfer ratio, reduces high series resistance loss, and brings down the input impedance of circuit. The copper wire wounds ferrite toroid core transformer provides very low series resistance and negligible core loss, which improves the circuit efficiency. This boost converter operates with an input voltage range of 22–300 mV and provides maximum output power of 0.073 – 147 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> correspondingly. The peak efficiency of 68% with output power of 1.32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{mW}}$</tex-math></inline-formula> (voltage ∼1.83 V) is achieved at an input voltage of 50 mV. For regulated output voltage, a feedback loop is used to keep output voltage constant during sudden voltage rise of TEG. The proposed circuit uses discrete components, ferrite toroid core, and PCB, which has lower cost than available energy harvester module, which uses energy harvesting ICs, discrete components, and tiny transformer. The lower startup voltage, higher output power, and voltage with high conversion efficiency of this boost converter maximize the applications potential of the TEG as a portable power source for Internet of Things (IoT) devices.

Wireless Power Transfer between Two Self-Resonant Coils over Medium Distance Supporting Optimal Impedance Matching Using Ferrite Core Transformers

An efficient wireless power transfer (WPT) system is proposed using two self-resonant coils with a high-quality factor (Q-factor) over medium distance via an adaptive impedance matching network using ferrite core transformers. An equivalent circuit of the proposed WPT system is presented, and the system is analyzed based on circuit theory. The design and characterization methods for the transformer are also provided. Using the equivalent circuit, the appropriate relation between turn ratio and optimal impedance matching conditions for maximum power transfer efficiency is derived. The optimal impedance matching conditions for maximum power transfer efficiency according to distance are satisfied simply by changing the turn ratio of the transformers. The proposed WPT system maintains effective power transfer efficiency with little Q-factor degradation because of the ferrite core transformer. The proposed system is verified through experiments at 257 kHz. Two WPT systems with coupling efficiencies higher than 50% at 1 m are made. One uses transformers at both Tx and Rx; the other uses a transformer at Tx only while a low-loss coupling coil is applied at Rx. Using the system with transformers at both Tx and Rx, a wireless power transfer of 100 watts (100-watt light bulb) is achieved.

Comment on “A study on improvement of discharge characteristic by using a transformer in a capacitively coupled plasma” [Phys. Plasmas 22, 123504 (2015)

In the paper [Y.C. Kim et al., Phys. Plasmas 22, 123504 (2015)], the plasma density in radio frequency (RF) capacitively coupled plasma was increased by introducing a step-down ferrite-core transformer into a conventional type-T impedance matching network. The authors ascribed the increment in plasma density to the reduction of DC self-bias. Although this correlation was roughly right, but behaviors of the DC self-bias in the asymmetric RF discharge that was non-linearly interacted with the external circuit were not discussed. In practical applications, this approach of increasing plasma density will be limited by the rapid increase in power loss in step-down ferrite-core transformer operating in high-power 13.56 MHz discharges and the still high DC self-bias governed by the asymmetric geometry.

A Simple Approach for Determination of Numerical Values of Ferrite Nonlinear Susceptibilities

This article presents a straightforward approach for determination of numerical values of nonlinear susceptibilities of soft magnetic ferrites. It is shown that numerical values of susceptibilities can be calculated from the measured amplitudes of harmonics in the output voltage of ferrite core transformer. For this purpose, useful expressions for the susceptibilities are derived and as example, numerical values of the largest nonlinear susceptibilities those of the third and fifth orders are calculated. Additionally, errors of the measured susceptibilities also are determined. Based on the expressions obtained, the analysis of phase shifts between components of flux density on different frequencies and the magnetic field strength also is performed. The comparison of the calculated and measured output voltage waveforms allows concluding that in the frequency range where losses are small and can be neglected, the susceptibility of the third order is negative but that of the fifth order is positive.

Overvoltage Protection for High Frequency High Voltage Power Transformers

Transformers with high-voltage operation may have undesired behavior due to the effects of their parasitic elements. In power electronics applications, if the primary voltage has harmonics, transformer resonances may be excited, causing high primary currents and secondary voltage stress, compromising the device isolation. This behavior is quite dangerous if the transformer operates without load, what means, without damping, because in this situation, the secondary voltage peak can reach more than two times the expected (rated) value. To protect the high frequency high voltage transformer against this dangerous operation, the overvoltage problem in open load condition is carefully explored and explained in this paper, with the proposition of different protection strategies to mitigate its effect, depending on the transformer parasitic elements values. The different strategies are analytically explained and validated by experimental results, showing their criteria design and effectiveness for the protection of high frequency high voltage transformers through the analysis of a 1 kVA, 311V, 20 kHz, 42/512 ferrite core transformer, showing its dynamics working alone and with each protection strategy.

A Multiphysics Design and Optimization Method for Air-Core Planar Transformers in High-Frequency LLC Resonant Converters

Air-core planar transformers are attractive alternatives to ferrite-core transformers for high-frequency power converters, such as LLC resonant converters. Although many design methods have been proposed for LLC converters, most of them are based on traditional ferrite-core transformers. There is a lack of efficient methods to design and optimize air-core planar transformers for high-frequency LLC converters. This paper presents a multiphysics optimal design framework that combines multiple physical models, the progressive bisection design method, and the Bayesian optimization technique to address air-core planar transformer design issues. It has the following contributions. 1) Multiple physical models, including circuit model, magnetoquasistatic model, full-wave electromagnetic model, are built for transformer design and efficiency evaluation. 2) The progressive bisection method and Bayesian optimization algorithm are applied to accelerate the optimal design process. 3) The proposed framework can accurately and efficiently design optimal air-core planar transformers and optimize efficiency in LLC converters. 4) A high-frequency flexible and thin LLC converter is constructed using the optimal design method.

A practical technique to measure transformer losses in high frequency SMPS

All electronic gadgets today employ high frequency Switch Mode Power Supplies. As the number of such gadgets is increasing rapidly, the focus is on improving the efficiency of power conversion and better utilization of energy. It is always a challenge for the practicing power supply engineers to exactly apportion and evaluate the total losses in the power converters. While it is relatively easy to compute and measure the power losses in semiconductor devices, it is practically difficult to measure the power losses in magnetic components. The data sheets provided by the manufacturers, for core loss and thermal resistance, do act as a starting point in the design stage but, always the designers felt the need to know the exact power loss in the ferrite high frequency transformers and their thermal resistance values. The data sheets provide thermal resistance values only for the cores and it is necessary to quantify value for a fully wound transformers. Copper losses in high frequency transformers are very significant and too involved to compute. In this paper, we propose a simple and practical technique, which precisely depicts the actual power loss in a high frequency ferrite core transformer. With this technique various ferrite cores can be characterized for their hysteresis losses at varying flux densities and frequencies. We can also precisely compute the thermal resistance of the Ferrite transformers.

High Frequency Transformer’s Parasitic Capacitance Minimization for Photovoltaic (PV) High-Frequency Link-Based Medium Voltage (MV) Inverter

The high-frequency-based medium voltage (MV) inverter is used in renewable energy power sources for power transmission. However, power quality is compromised as a result of the increase in common mode noise currents by the high inter-winding parasitic capacitance in high-frequency link transformers. This fast voltage transient response leads to harmonic distortion and transformer overheating, which causes power supply failure or many other electrical hazards. This paper presents a comparative study between conventional and modified toroid transformer designs for isolated power supply. A half bridge high-frequency (10 kHz) MV DC–AC inverter was designed along with power source; a 680 W solar module renewable system was built. An FEM-simulation with Matlab-FFT analysis was used to determine the core flux distribution and to calculate the total harmonics distortion (THD). A GWInstek LCR meter and Fluke VT04A measured the inter-winding capacitance and temperature in all four transformer prototypes, respectively. The modified design of a toroid ferrite core transformer offers more resistance to temperature increase without the use of any cooling agent or external circuitry, while reducing the parasitic capacitance by 87%. Experiments were conducted along with a mathematical derivation of the inter-winding capacitance to confirm the validity of the approach.

Surface-Oxidized Amorphous Alloy Powder/Epoxy-Resin Composite Bulk Magnetic Core and Its Application to Megahertz Switching LLC Resonant Converter

To realize a compact, lightweight and high-efficiency megahertz (MHz) switching DC–DC converter using SiC/GaN power device, inductor/transformer core must have small core loss at such high frequency to maintain high efficiency of the converter. This paper focuses on Fe-based amorphous (Fe-AMO) alloy powder used in metal composite bulk magnetic core for MHz switching DC–DC converter, where fine Fe-AMO powder with a mean diameter of $2.56~ {\mu }\text{m}$ was used to suppress MHz band eddy current inside the Fe-AMO powder body. When applying Fe-AMO powder to the closely packed composite core together with epoxy resin, high electrical-resistivity layer must be formed on the Fe-AMO powder surface in order to suppress the overlapped eddy current between adjacent Fe-AMO powders. In this paper, about 10 nm-thick oxidized layer of the Fe-AMO powder surface was successfully formed by using annealing in dry air. This paper describes on the surface-oxidized Fe-AMO powder/epoxy-resin composite bulk core transformer and its application to GaN power device MHz switching LLC resonant DC–DC converter. By using the Fe-AMO composite core transformer, the fabricated 48 V-input/24 V-output LLC resonant converter exhibited 90% over efficiency in the output power range of 24 to 120 W, which was higher efficiency when using the Ni–Zn ferrite core transformer.

High Input Power Factor High Frequency Push-Pull DC/DC Converter

To maintain high efficiency and high power density increased switching frequency is the primary path. The push-pull converter used as ac-dc converter is very suitable for low and medium power application. High efficiency, low switching loss and high power density are the predominance of this application Increased switching frequency gives high power density, reduces size of components and this give simplicity of the circuit. Main aim of proposed topology is to obtain isolated dc voltage from ac voltage input with reduced switching losses and high input poer factor. This topology uses push-pull converter with z-source to improve input power factor and ,50 khz switching frequency with ferrite core transformer to obtain high poer density. This converter topology is suitable for obtaining low voltage ,high current source from a high voltage ,low current AC source. This would find application in high current battery bank charging, heating of the bearings, led lightings and

High-Order Resonant Converter Topology With Extremely Low-Coupling Contactless Transformers

Although a large number of typical resonant converter topologies have been developed for use in contactless power transfer applications, these topologies need to be precisely optimized to obtain maximum efficiency and maximum power transferring capacity. High-order resonant power converters with flexible designs are invariably required to develop energy-efficient and cost-effective converter systems. An ideal converter topology can contribute toward realizing efficient converter systems if it is capable of providing an optimized output that is insensitive to load variations, coupling coefficient, type of the wireless transformer used, and other operating conditions. This paper presents a new contactless power converter topology for a low-coupling (0.14) ferrite-core transformer that has low cost, small size, high efficiency, and a wide gap (20 mm). In addition, the merits and demerits of conventional converter topologies are studied herein, and results for these topologies are compared with those for the proposed converter topology.

A Class of Quadrature Couplers Based on Transformer

A study of lumped transformer-based directional couplers is proposed by converting a conventional two-port transformer into a four-port directional coupler. The directional coupler of this kind is a backward coupler that consists of a ferrite-core transformer and four or five associated lumped reactive elements. Four different topologies of the coupler are proposed with four different reactive element arrangements, namely, ring topology, cross topology, H-shaped topology, and twisted topology. Analysis and design equations are presented. Four different circuits with different frequency responses are derived. Four 13.56-MHz couplers with these four different topologies are designed, fabricated, and measured. Wideband, compact, and backward wave coupling features are theoretically and experimentally confirmed.

High voltage high repetition rate pulse using Marx topology

The paper describes Marx topology using MOSFET transistors. Marx circuit with 10 stages has been done, to obtain pulses about 5.5KV amplitude, and the width of the pulses was about 30μsec with a high repetition rate (PPS > 100), Vdc = 535VDC is the input voltage for supplying the Marx circuit. Two Ferrite ring core transformers were used to control the MOSFET transistors of the Marx circuit (the first transformer to control the charging MOSFET transistors, the second transformer to control the discharging MOSFET transistors).

Characterization of a pulsed mode high voltage power supply for nuclear detectors

This paper discusses the characterization of a pulsed mode high voltage power supply (HVPS) using LT1073 chip. The pulsed modulated signal generated from this chip is amplified using a step-up ferrite core transformer of 1:20 turn ratio and then further multiplied and converted into DC high voltage output using a diode-capacitor arrangement. The circuit is powered by a 9V alkaline battery but regulated at 5V supply. It was found that the output for this setup is 520V, 87 μA with 10% load regulation. This output is suitable to operate a pancake-type GM detector, typically model LND 7317 where the plateau is from 475V to 675V. It was also found that when a β-source with intensity of 120 cps is used, the power consumption of the circuit is 5 V, 10.1 mA only. When the battery was left 'on' for 40 hours continuously, the battery's voltage has dropped to 6.9V, meaning that the 5V supply as well as 520V output is still maintained. It is noted that the minimum output voltage of 475V has reached when the regulated supply has reduced to 4.6V and consequently the 9V battery dropped to 6.5V, and this had happened after approximately 3 days of continuous operation. The power efficiency for this circuitry was found to be 89.5%. This result has far better in performance since the commercial portable equipment of this type has normally specified that not less than 8 hours continuous operation only. On the circuit design for this power supply, it was found that the enveloped frequency is 133 Hz with approximately 50% duty cycle. The modulated frequency during 'on' state was found to be 256 KHz in which the majority of power consumption is required.

Soft-Switched DC-DC Converter with Current and Voltage Doubler

This paper proposes a method that consists of a phase-shift converter with a current doubler rectifier on the output side. The phase-shift converter operates at a frequency as high as 20-25 kHz (depending on the requirement of the application) to improve the power density of the converter using unity turns ratio in the isolation transformer. The size of the circuit is smaller for the same power rating. Ferrite core transformer is used instead of the conventional one, which is bulky and leads to a very large core loss. Unlike the conventional method, the number of turns of the transformer is reduced and the overall power density is increased. The current doubler rectifier doubles the input current as needed for a few vital applications. The circuit for the phase-shift converter with the current doubler was simulated using PSPICE software. For an input current of 4 A, an output of 10.2 A was obtained, which eventually settled at nearly 8.5 A. A hardware model of the proposed method validates the simulation results.

Soft-switched DC-DC converter with current and voltage doubler

This paper proposes a method that consists of a phase-shift converter with a current doubler rectifier on the output side. The phase-shift converter operates at a frequency as high as 20-25 kHz (depending on the requirement of the application) to improve the power density of the converter using unity turns ratio in the isolation transformer. The size of the circuit is smaller for the same power rating. Ferrite core transformer is used instead of the conventional one, which is bulky and leads to a very large core loss. Unlike the conventional method, the number of turns of the transformer is reduced and the overall power density is increased. The current doubler rectifier doubles the input current as needed for a few vital applications. The circuit for the phase-shift converter with the current doubler was simulated using PSPICE software. For an input current of 4 A, an output of 10.2 A was obtained, which eventually settled at nearly 8.5 A. A hardware model of the proposed method validates the simulation results.

直列および並列共振コンデンサを用いた非接触給電システム

A new contactless power transfer system using series and parallel resonant capacitors is described. If the primary series resonant capacitor and the secondary parallel resonant capacitor are chosen appropriately, the equivalent circuit of the transformer with these capacitors becomes very simple at the resonant frequency. Ignoring the winding resistance and the core loss, the equivalent circuit is the same as an ideal transformer. Therefore, the circuit analysis is easy, and if the input voltage is constant, the output voltage is also constant regardless the output current. Fig. 1 shows the configuration of our contactless power transfer system. The ferrite-core transformer with 10~20 mm gap is drived by 10 kHz rectangular waveform inverter. As the winding resistance and the ferrite-core loss are very small, the simplified equivalent circuit of Fig. 2 can be used. The parallel capacitor Cp at the secondary winding and the series capacitor Cs at the primary winding are determined as following values. 1 ω0CP = xP = x0 + x2 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · (1)

A bidirectional, sinusoidal, high-frequency inverter design

A new method for the design of a bidirectional inverter based on the sinusoidal pulse-width modulation principle and the use of a low-cost and lightweight ferrite-core transformer is presented. The inverter is designed for either ohmic or inductive loads. In the case of inductive loads the reactive power is transferred back to the DC input power source using a new active rectifier design. The inverter is controlled by two minimum-time feedback loops, providing relatively low output voltage distortion (less than 2% for DC input higher than 24V) and good load regulation (better than 2%), while the inverter efficiency remains relatively constant (from 80 to 85%) over a wide output power range (75 to 200W) and DC input voltage range (23 to 28V). Theoretical results are experimentally verified using a laboratory prototype.