Showing papers on "Flyback transformer published in 2007"

Analysis of Very Fast Transients in Layer-Type Transformer Windings

Abstract: This paper deals with the measurement, modeling, and simulation of very fast transient overvoltages in layer-type distribution transformer windings. Measurements were performed by applying a step impulse with 50-ns rise time on a single-phase test transformer equipped with measuring points along the winding. Voltages along the transformer windings were computed by applying multiconductor transmission-line theory for transformer layers and turns. Interturn voltage analysis has also been performed. Computations are performed by applying an inductance matrix determined in two different ways; by making use of the inverse capacitance matrix and by making use of the well known Maxwell formulas. The modeling of the transformer and the computations are verified by measurements

Soft-Switching Zeta–Flyback Converter With a Buck–Boost Type of Active Clamp

Abstract: This paper presents the system analysis, design consideration, and implementation of a soft-switching zeta-flyback converter to achieve zero-voltage switching (ZVS). In the proposed converter, the zeta and flyback topologies are adopted in the output side to achieve the following features: to share the power components in the transformer primary side, to achieve the partial magnetizing flux reset, and to share the output power. The buck-boost type of active clamp is connected in parallel with the primary side of the isolation transformer to recycle the energy stored in the leakage inductor of isolated transformer and to limit the peak voltage stress of switching devices due to the transformer leakage inductor when the main switch is turned off. The active clamp circuit can make the switching devices to turn on at ZVS. Experimental results taken from a laboratory prototype rated at 240 W, input voltage of 150 V, output voltage of 12 V, and switching frequency of 150 kHz are presented to demonstrate the converter performance. Based on the experimental results, the circuit efficiency is about 90.5% at rated output power, and the output voltage variation is about 1%.

A 23-dBm 60-GHz Distributed Active Transformer in a Silicon Process Technology

Abstract: In this paper, a distributed active transformer for the operation in the millimeter-wave frequency range is presented. The transformer utilizes stacked coupled wires as opposed to slab inductors to achieve a high coupling factor of kf=0.8 at 60 GHz. Scalable and compact equivalent-circuit models are used for the transformer design without the need for full-wave electromagnetic simulations. To demonstrate the feasibility of the millimeter-wave transformer, a 200-mW (23 dBm) 60-GHz power amplifier has been implemented in a standard 130-nm SiGe process technology, which, to date, is the highest reported output power in an SiGe process technology at millimeter-wave frequencies. The size of the output transformer is only 160times160 mum2 and demonstrates the feasibility of efficient power combining and impedance transformation at millimeter-wave frequencies. The two-stage amplifier has 13 dB of compressed gain and achieves a power-added efficiency of 6.4% while combining the power of eight cascode amplifiers into a differential 100-Omega load. The amplifier supply voltage is 4 V with a quiescent current consumption of 300 mA

Active-Clamping ZVS Flyback Converter Employing Two Transformers

Abstract: This paper presents a two-transformer active-clamping zero-voltage-switching (ZVS) flyback converter, which is mainly composed of two active-clamping flyback converters. By utilizing two separate transformers, the proposed converter allows a low-profile design to be readily implemented while retaining the merits of a conventional single-transformer topology. The presented two-transformer active-clamping ZVS flyback converter can approximately share the total load current between two secondaries. Therefore, the transformer copper loss and the rectifier diode conduction loss can be decreased. Detailed analysis and design of this new two-transformer active-clamping ZVS flyback converter are described. Experimental results are recorded for a prototype converter with an ac input voltage ranging from 85 to 135 V, an output voltage of 24 V and an output current of 8 A, operating at a switching frequency of 180 kHz.

On-time control for constant current mode in a flyback power supply

Abstract: A primary side sensing power control system and method for constant current control that utilizes a relationship that involves the measured reset-time from the previous cycle to determine the primary side peak current and off-time for the next cycle. This control mechanism does not need the knowledge of input voltage or magnetizing inductance. Therefore, it removes the sensitivities of input voltage and magnetizing inductance to the output current limit. Furthermore, it uses a time measurement instead of a voltage measurement for the current calculation which in many cases is easier to perform.

Soft-switching flyback inverter with enhanced power decoupling for photovoltaic applications

Abstract: A novel single-phase flyback inverter for photovoltaic applications is proposed to achieve low-frequency ripple current reduction on the DC busbar and to draw sinusoidal current into the AC grid. Based on capacitive idling techniques, the proposed circuit topology is derived from a single-ended primary-inductance converter and two-switch flyback inverter to obtain soft-switching operation for all of the active switches. Compared with a buck-boost inverter and other flyback inverter topologies for AC photovoltaic module systems, no extra active switches are used in the proposed inverter to realise both soft-switching and enhanced power decoupling with only four active switches. Peak-current mode control method is employed in the control schemes to ensure pure sinusoidal current with unity power factor on the AC grid. Laboratory experimental results based on a 500 W prototype are provided to verify the effectiveness of the proposed inverter.

Circuitry for supplying electrical power to loads

Abstract: A power supply, comprising a boost converter which provides voltage to a first load, and a flyback converter which provides voltage to a second load and which utilizes an inductive element of the boost converter as a primary winding of a transformer of the flyback converter. Also, a power supply comprising a MOSFET which is disposed between solid state elements and a second reference potential and which controls current flowing through the solid state elements. Also, a circuit comprising a transformer, a first circuit portion comprising the primary winding of the transformer and a second circuit portion comprising the secondary winding of the transformer. Also, a power supply comprising means for using a common transformer for providing a boost converter and a flyback converter. Also, a power supply comprising a transformer, means for providing a boost converter utilizing the transformer, and means for providing a flyback converter utilizing the transformer.

Switching power supply

Abstract: A switching power supply is provided which keeps constant, even when the oscillation frequency of a switching element increases, the on duty of secondary current passing through a secondary winding, thereby achieving a constant current drooping characteristic with high accuracy. To be specific, a secondary current on-period detection circuit generates a signal indicating the off timing of the secondary current, based on a flyback voltage generated on an auxiliary winding. A secondary-current detection delay time correction circuit generates a signal indicating a time when a predetermined period has elapsed since the switching element is turned off. A secondary current on-duty control circuit generates a clock signal for turning on the switching element so as to keep constant the on duty of the secondary current, based on the signal generated by the secondary current on-period detection circuit and the signal generated by the secondary-current detection delay time correction circuit.

Hybrid Transformer Model for Transient Simulation: Part I - Development and Parameters

Abstract: Summary form only given. A new topologically-correct hybrid transformer model is developed for low- and mid-frequency transient simulations. Power transformers have a conceptually simple design, but behaviors can be very complex. Selection of the most suitable representation for a given behavior depends on the type of transformer to be simulated, the frequency range, and other factors such as the internal design of the transformer and available parameters or design data. Here, a modular model suitable for frequencies up to 3-5 kHz is developed, utilizing a duality-based lumped-parameter saturable core, matrix descriptions of leakage and capacitive effects, and frequency-dependent coil resistance. Implementation and testing of this model was done for 15-kVA 208D-120Y 3-legged and 150 kVA 12, 470Y-208Y 5-legged transformers. The basis and development of the model is presented, along with a discussion of necessary parameters and the approaches for obtaining them.

Two-Stage Cell Balancing Scheme for Hybrid Electric Vehicle Lithium-Ion Battery Strings

Abstract: Two-stage charge equalization scheme for HEV lithium-ion battery string is proposed with the optimal power rating design rule in this paper, where in the first stage the over charged energy of higher voltage cells is drawn out to the single common output capacitor and then, that discharged energy is recovered into the overall battery stack in the second stage. To achieve charge equalization of sort, the conventional flyback DC/DC converters of low power and minimized size are employed. The industrial sample employing both the proposed two-stage cell balancing scheme and the optimal power rating design rule shows good cell balancing performance with reduced size as well as low voltage stresses of the electronic devices.

Multicell Interleaved Flyback Using Intercell Transformers

Abstract: An original converter composed of interleaved flyback is presented. The cells are interconnected through intercell transformers replacing the standard multi-winding inductors used as insulation and storage magnetic device in the flyback. The combination of the interleaving effects and of the intercell transformer characteristics allows eliminating the mains limitations of the standard flyback due to the low performances of multiwindings inductors. In a first part, the different ways to interleave galvanic insulated converters as forward or flyback are briefly recalled. The second part presents the intercell transformers and shows that they can be used to interconnect interleaved converters cells. In the third and last part, this particular magnetic interconnection is applied to interleaved flyback cells and leads to create an ldquointercell transformer flybackrdquo. Its specific properties and advantages are described. Experimental results, obtained on a 2-kW test bench are finally presented.

Double ended converter with output synchronous rectifier and auxiliary input regulator

Abstract: A DC to AC power converter is disclosed. The power converter has four power-switching devices, two diodes, a step-up and isolation transformer, a capacitor-choke filter and a controller. Two power-switching devices located on the primary side of the transformer are switched to provide alternate cycles of an ac current to the primary side of the transformer, which magnetically couples the ac current to the secondary side of the transformer. Two power-switching devices on the secondary side of the transformer are switched to alternately allow the forward and return ac currents from the secondary side of the transformer in the output path to a load connected to the output of the DC to AC power converter.

An Airborne Radar Power Supply With Contactless Transfer of Energy—Part II: Converter Design

Abstract: A magnetic link is established between the stationary and revolving frames of a radar system by means of a rotating transformer. Based on the magnetics analysis of Part I of the series, a design methodology is proposed for integrating a rotating transformer into a power electronic converter using the efficiency and voltage gain plots. It is shown that a phase-shifted full-bridge topology can effectively utilize the parasitic components of the transformer. The increased magnetizing current assists the resonant transition, and this, in turn, compensates for the increased conduction losses that a rotating transformer yields. The proposed design method secures the soft-switching operation of the converter over the entire load range and allows efficient operation and reduced electromagnetic emissions. The methodology is evaluated experimentally, and the resulting prototype demonstrates an average efficiency of 92.6% in the 0.2-1-kW output power range. The proposed topology extends the power capacity of the rotating transformer without compromising its size, cost, or performance. A comparison between the slip rings and rotating transformer solutions highlights the merits and weaknesses of each technology.

An Improved Single-Stage Flyback PFC Converter for High-Luminance Lighting LED Lamps

Abstract: This paper presents a universal power supply for high-luminance LED lamp test. The proposed power supply is designed and implemented by adopting an improved single-stage Flyback configuration. A constant current control method is used to regulate the lamp current and brightness under different pieces of LED series connection. A laboratory prototype has been built and tested. With the prototype, high efficiency, high power factor, and constant lamp current can be achieved for the performance test of various LED lamps.

A Novel Transformer Structure for High power, High Frequency converter

Abstract: Power transformer structure is a key factor for the high power, high frequency converter performance which includes efficiency, thermal performance and power density. This paper proposes a novel transformer structure for the kilo-watt level, high frequency converter which is reinforce insulation needed for the secondary side to primary side. The transformer has spiral-wound primary layers using TIW (triple insulation wire) and PCB-winding secondary layers. All the windings are arranged by full interleaving structure to minimize the leakage inductance and eddy current loss. Further more, the secondary rectifiers and filter capacitors are mounted in PCB-winding secondary layers to further minimize the termination effect. A 1.2 KW (O/P: 12 V/100 A, I/P: 400 V) Mega Hz LLC converter prototype employed the proposed transformer structure is constructed, and over 96% efficiency achieved.

Integrated Zeta–Flyback Electronic Ballast to Supply High-Intensity Discharge Lamps

Abstract: This paper proposes a metal halide lamp electronic ballast based on the integration of zeta and flyback converters, which are used to achieve power factor correction and lamp current stabilization, respectively. The proposed integrated converter allows to reduce the number of ballast components without increasing the current stress in the shared switch. Thus, the lamp is supplied with a low-frequency square waveform that avoids the acoustic resonance phenomenon. The proposed topology has been implemented and validated by experimental results.

Operating Performance of the Flux-Lock and the Transformer Type Superconducting Fault Current Limiter Using the YBCO Thin Films

Abstract: The operating characteristics of the flux-lock and the transformer type superconducting fault current limiters (SFCLs) have been tested and compared each other. The SFCLs are composed of the primary and secondary coils and the YBCO thin film as a current limiting unit. The turn ratios between the primary and secondary windings were 63:21 and 63:42, respectively. The winding direction between the primary and secondary windings was subtractive. When a fault occurred under the same conditions, the line current was limited more effectively in the transformer type SFCL. That is, the current value of the flux-lock type SFCL was approximately 2 times as high as that of the transformer type SFCL at the turn ratio of 63:42. However, the flux flowing into the iron core of the flux-lock type was less saturated than in the transformer type due to its flux distribution. The resistance generated in the YBCO thin film was higher in the flux-lock type where its voltage was also higher because of the winding direction between the primary and secondary windings. The initial limiting current of the flux-lock type was 2 times as high as that of the transformer type at the turn ratio of 63:42. The power consumed in the YBCO thin film of the transformer type was also remarkably low because the resistance, the current, and the voltage of the YBCO thin film are all lower. Consequently, we found that the transformer type had advantages for the current limiting effect and power burden of the YBCO thin film.

Minimum Phase Response in Digitally Controlled Boost and Flyback Converters

Abstract: This paper addresses modeling and control issues related to practical high-frequency digital PWM control of constant-frequency boost, buck-boost and flyback converters. Discrete-time models, including the effects of A/D sampling and delays in the digital control loop, are derived for two cases: output voltage A/D sampling during transistor off time in combination with trailing-edge (TE) DPWM, and A/D sampling during transistor on time in combination with leading-edge (LE) DPWM. We show that off-time sampling with TE-DPWM, which is a common approach in digital controller realizations, can result in desirable minimum-phase responses, thus simplifying compensator design in wide bandwidth closed-loop voltage regulators based on boost or flyback converters. The results are verified by simulation and experimental results on a boost converter prototype.

Minimum Phase Response inDigitally Controlled Boostand Flyback Converters

Abstract: Thispaperaddresses modeling andcontrol issues related topractical high-frequency digital PWM control of constant-frequency boost, buck-boost andflyback converters. Discrete-time models, including theeffects ofA/Dsampling and delays inthedigital control loop, arederived fortwocases: outputvoltage A/D sampling duringtransistor offtimein combination withtrailing-edge (TE)DPWM, andA/Dsampling during transistor ontimeincombination withleading-edge (LE) DPWM. We showthatoff-time sampling withTE-DPWM,which isa commonapproach indigital controller realizations, can result indesirable minimum-phase responses, thussimplifying compensator design inwidebandwidth closed-loop voltage regulators basedonboost orflyback converters. Theresults are verified by simulation andexperimental results on a boost converter prototype.

DC power transmission system of voltage source converter using pulse-interleaving auxiliary circuit

Abstract: A DC power transmission system of a voltage source converter using a pulse-interleaving auxiliary circuit is disclosed. The converter system comprises an IGBT converter for converting an AC power to a DC power or the DC power to the AC power; an open Y-Y transformer and a Y-Δ transformer for stepping up or stepping down the AC power having a predetermined magnitude; a capacitor for dividing a DC voltage; and a DC Auxiliary circuit composed of a normal transformer and half-bridge for overlapping a pulse type input voltage to increase the number of pulses of an output waveform. In using a DC auxiliary circuit composed of normal transformer and 3-level half-bridge to increase the number of pulses of the output waveform by superposing the voltage in the form of the pulse, a normal transformer may be used instead of the tapped transformer to reduce the size thereof and to obtain an accurate transformer ratio, and a 3-level half-bridge may be used instead of the H-bridge to reduce the switching loss.

Circuit and associated method for reducing power consumption in an a power transformer

Abstract: A method and circuit is provided for reducing power consumption in a power transformer, typically incorporated into an electrical or electronic device such as a consumer device. In an embodiment, a detection/isolation circuit is coupled to an input of a power transformer/rectifier via a switching device. The switching device can be, for example, a solid state relay. The detection/isolation circuit is configured to sense the occurrence of no-load conditions in the power transformer and responsively disengage the power transformer from a coupled source of power (e.g., wall outlet) via the coupled switching device.

Circuit System With Supply Voltage For Driving An Electromechanical Switch

Abstract: A circuit (10) for controlling operation of a load (16). In one example, a MEMS switch (20) is positioned in the circuit(10) to place the load (16) in one of a conducting state or a nonconducting state. A piezoelectric transformer (46) provides a relatively high voltage output signal or a relatively low voltage output signal to control movement of the switch (20) between a closed position, placing the load in the conducting state, and an open position. The high voltage output signal includes a frequency component in the resonant frequency range of the transformer (46). Control circuitry (65) provides an input voltage signal to the piezoelectric transformer (46) to provide the high voltage output signal or the low voltage output signal at the output terminals of the piezoelectric transformer (46).

Reduction Methods of Conducted EMI Noise on Parallel Operation for AC Module Inverters

Abstract: An AC photovoltaic module system consists of a photovoltaic module and a voltage source inverter, and a number of the ac modules are connected in parallel. The inverters have to be connected to a photovoltaic module on the roof of a residence, therefore it is necessary to make it small and light weight. Thus, the flyback inverter is used for the AC module system in this paper. The advantage of the inverters is that stable current injection into a utility line can be achieved without using the inter-linkage inductor. When the common-mode filter is connected in series to the total output of the inverters, the reduction effect of the common-mode noise is greater than when individual filters are connected to each inverter output. This paper discusses common- and differential-mode EMI noise for AC module inverters and shows an installation point for a common- and differential-mode filter to reduce the noise voltage.

Method and apparatus of providing synchronous regulation for offline power converter

Abstract: A synchronous regulation circuit is provided to improve the efficiency for an offline power converter. A secondary-side switching circuit is coupled to the output of the power converter to generate a synchronous signal and a pulse signal in response to an oscillation signal and a feedback signal. An isolation device transfers the synchronous signal from the secondary side to the primary side of the power converter. A primary-side switching circuit further receives the synchronous signal to generate a switching signal for soft switching a transformer. The pulse signal is utilized to control a synchronous switch for rectifying and regulating the power converter. The synchronous switch includes a power switch and a control circuit. The control circuit receives the pulse signal for turning on/off the power switch. The power switch is connected in between the transformer and the output of the power converter. In addition, a flyback switch is operated as a synchronous rectifier to freewheel the inductor current of the power converter. The flyback switch is turned on in response to the off of the power switch. The on time of flyback switch is correlated to the on time of the power switch.

Limitations of the Flyback Power Factor Corrector as a One-Stage Power Supply

Abstract: Low cost passive power factor correction solutions and single-stage integrated converters cannot draw a sinusoidal input current and are only suitable solutions for low power levels. Power factor correctors (PFC) with a multiplier solve this drawback, but need a second-stage DC/DC converter to obtain fast output voltage dynamics. However, the output voltage response of a PFC can be improved by increasing the bandwidth of the error amplifier of the output voltage feedback loop. So, a one-stage PFC can be used as complete power supply when an extremely fast output response is not required. Nevertheless, increasing error amplifier bandwidth compromises design, making it more difficult to comply with IEC 61000-3-2 standards. This paper analyzes the application limits of the Flyback PFC as a complete power supply. The thrust of the paper is to establish the Flyback PFC as a solution for PFC topologies depending on power level, input voltage range, output voltage, output response and line current harmonic content. Static and dynamic models have been included in this study. Finally, theoretical results are validated using a 600 W prototype.

Active-clamping ZVS flyback converter employing two transformers

Abstract: This paper presents a two-transformer active- clamping zero-voltage-switching (ZVS) flyback converter, which is mainly composed of two active-clamping flyback converters [1]-[2] By utilizing two separate transformers[3], the proposed converter allows a low-profile design to be readily implemented while retaining the merits of a conventional single-transformer topology The presented two-transformer active-clamping ZVS flyback converter can approximately share the total load current between two secondaries Therefore the transformer copper loss and the rectifier diode conduction loss can be decreased Detailed analysis and design of this new two-transformer active-clamping ZVS flyback converter are described

Adaptively configured and autoranging power converter arrays

Abstract: Multi-cell DC-DC power converters are described. In an adaptive version the isolated regulating multi-cell converter adaptively configures the input cells in a series connection to share the input voltage and in a parallel configuration to share the input current. Double-clamped buck-boost ZVS switching DC-DC, active clamped flyback, and flyback converter topologies may be used in the cells of the converter.

A lead-free piezoelectric transformer in radial vibration modes.

Abstract: In this study, a disk-shaped piezoelectric transformer was fabricated using lead-free (K,Na)NbO3-based ceramics with high mechanical quality factor. The transformer can operate in the fundamental or the third radial vibration mode. The transformer is poled along the thickness direction. The top surface is covered by ring/dot silver electrodes separated by an annular gap which serve as the input and output parts of the transformer, respectively. The bottom surface, fully covered with a silver electrode, is grounded as a common electrode. The dimensions of the top ring/dot electrodes are designed such that the third radial vibration mode can be strongly excited. The electrical properties of the transformer with diameter of 34.2mm and thickness of 1.9mm were measured. For a temperature rise of 35°C, the transformer has a maximum output power of 12W. With the matching load, its maximum efficiency is >95%, and maximum voltage gains are 6.5 and 3.9 for the fundamental and the third radial vibration modes, respe...

Apparatus to provide synchronous rectifying circuit for flyback power converters

Abstract: A synchronous rectifying circuit is provided for flyback power converter. A pulse generator is utilized to generate a pulse signal in response to a leading edge and a trailing edge of a switching signal. The switching signal is used for switching the transformer of the power converter. An isolation device such as pulse transformer or small capacitors is coupled to the pulse generator for transferring the pulse signal through an isolation barrier of a transformer. A synchronous rectifier includes a power switch and a control circuit. The power switch is connected in between the secondary side of the transformer and the output of the power converter for the rectifying operation. The control circuit having a latch is operated to receive the pulse signal for controlling the power switch.

VLSI Design and Application of a High-Voltage-Compatible SoC–ASIC in Bipolar CMOS/DMOS Technology for AC–DC Rectifiers

Abstract: This paper presents an application-specific integrated circuit (ASIC) controller that is suitable for double-stage AC-DC power converters, which employ power-factor correction (PFC) and flyback topologies. The PFC cell is used as a preregulator to comply with line-current harmonic standards, while the flyback converter operates in quasi-resonant (QR)/discontinuous conduction mode to deliver to the load a maximum output power of 120 W. The control functions of the PFC and flyback converters are combined in a unique system-on-chip-ASIC solution to reduce system complexity. The ASIC implements valley-switching control of both the PFC and flyback cells to achieve QR operation. The concept of ldquovalley skippingrdquo is also recalled by the proposed ASIC to determine the operating point in the power-frequency characteristic of the power converter. Depending on the output-power requirement, the ASIC drives the flyback stage into three different states, which result from the combination of the QR and valley-skipping modes. This allows the flyback converter to operate at a fixed on-time, while its off-time is changed according to the output power. The PFC stage is also driven in the QR mode with valley skipping to provide the DC-DC stage with a fixed input voltage of 400 V. To evaluate the performances of the presented ASIC device, a demoboard of a 120-W PFC-flyback system has been realized and tested. Several experimental results have been carried out to confer the validity of the approach that is discussed throughout this paper and to evaluate the performances of the AC-DC rectifier.