Showing papers on "Flyback transformer published in 2005"

Flyback inverter controlled by sensorless current MPPT for photovoltaic power system

Abstract: This paper presents a flyback inverter controlled by sensorless current maximum power point tracking (MPPT) for a small photovoltaic (PV) power system. Although the proposed system has small output power such as 300 W, a few sets of small PV power systems can be easily connected in parallel to yield higher output power. When a PV power system is constructed with a number of small power systems, the total system cost will increase and will be a matter of concern. To overcome this difficulty, this paper proposes a PV system that uses no expensive dc current sensor but utilizes the method of estimating the PV current from the PV voltage. The paper shows that the application of this novel sensorless current flyback inverter to an MPPT-operated PV system exhibits satisfactory MPPT performance similar to the one exhibited by the system with a dc current sensor as well. This paper also deals with the design method and the operation of the unique flyback inverter with center-tapped secondary winding.

Analysis of integrated boost-flyback step-up converter

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

High boost converter using voltage multiplier

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

AC to DC power supply with PFC for lamp

Abstract: An AC-to-DC converter with PFC or without PFC generates an output constant voltage at any predetermined value (no matter less or more than input line peak voltage, or even equal to input line peak voltage) with an input line AC voltage with wide range (Typical sinusoidal 110 VAC, 60 Hz or 220 VAC, 50 Hz). It is mainly used as power supply for lamp. Previous power supply for lamp has low frequency component or high frequency component. (1) Low frequency light cause eyes pupil and crystalline lens will adjust 60 times, 120 or many times per second to cause eyes tired. Pupil open wide and crystalline lens adjust to collect more light to focus on retina for seeing clearly at weak light while pupil open narrow and crystalline lens adjust to collect less light to focus on retina at strong light to prevent retina from strong light harm and hurt. In the long run, muscles to control pupil and crystalline lens become very tired and become flabby. Then the muscle can't adjust pupil and crystalline according to distance and brightness so that myopia is caused. (2) High frequency voltage causes lamp brightness changes too fast. Eyes can not adjust fast enough to follow the brightness change of lamp for high frequency voltage. But high frequency large current on the secondary cause high EMI that has risk to harm people's health. High frequency light causes EMI issue. Peoples' eyes can't keep up with high frequency light. Peak strong light shine on the retina for pupil can't shrink at high frequency light. In the long run, retina will be harmed and affect eyesight is affected, cornea dryness or crystalline lens opacity is caused. My invention of power supply lamp has only DC constant voltage on lamp. Lamp's brightness is constant and has no low frequency or high frequency component Thus peoples' eyes and health are protected to maximum extent. The output voltage is regulated at predetermined DC constant value by feedback. You can adjust feedback potentiometer value to set output voltage. Potentiometer and resistor voltage divider with auxiliary winding, (opto-coupler, digital isolator or direct feedback) compose the dimming feedback circuit. It is convenient to adjust the brightness of lamp for eyes' comfort by adjusting the potentiometer resistance value. My invention can be used directly on second category lamp that doesn't need high voltage with ballast to start the lamp. Most of them use heat generated by filament or diode etc to create light. Such as Halogen, Incandescent, LED, PAR lamp, miniature sealed beam lamp, Projection lamp, automotive lamp, some stage and studio lamp, DC fluorescent lamp etc. The converter realized pulse-by-pulse or other current limit protection by sense the current sense resistor or signal transformer. One stage DC sinusoidal to DC constant converter 206 can be implemented by all kinds of topologies other than the following topologies as long as they can convert DC sinusoidal voltage to DC constant voltage. Buck, Boost, Buck-boost, Noninverting buck-boost ,H-Bridge, Watkins-Johnson, Current-fed bridge, Inverse of Watkins-Johnson, Cuk, SEPIC, Inverse of SEPIC, Buck square, full bridge, half bridge, Forward, Two-transistor Forward, Push-pull, Flyback, Push-pull converter basedon Watkins-Johnson, Isolated SEPIC, Isolated Inverse SEPIC, Isolated Cuk, Two-transistor Flyback etc One stage AC to DC converter 206 can be realized by discrete components without controller 209 , active startup circuit, feedback circuit or sample circuit. Main switch and active startup circuit can be integrated in IC controller. The AC to DC converter is not used only for lamp. It is can also be used for any device requires DC power supply in all the industrial areas. (Telecommunication, Storage, Personal computer, cell phone power supply and charger, video game etc) For example, Bus AC to DC converter, PFC converter, PFC converter for lighting Computer power supply, Monitor power supply, notebook adapter, LCD TV, AC/DC adapter, adjusted voltage charger, Power tool charger, Electronic ballast, Video game power supply etc.

Flyboost power factor correction cell and a new family of single-stage AC/DC converters

Abstract: A novel power factor correction (PFC) cell, called flyboost, is presented. The proposed PFC cell combines power conversion characteristics of conventional flyback and boost converters. Based on the flyboost PFC cell, a new family of single-stage (S/sup 2/) ac/dc converters can be derived. Prominent features of newly derived S/sup 2/ converters include: three power conversions, i.e., boost, flyback, and another isolated dc/dc power conversions are simultaneously realized that typically uses only one power switch and one simple controller; part of the power delivered to the load is processed only once; bulk capacitor voltage can be clamped to the desired level; and capable of operating under continuous current mode. Experimental results on example converters verify that while still achieving high power factor and tight output regulation, the flyboost PFC cell substantially improve the efficiency of the converter.

Control of high-frequency AC link electronic transformer

Abstract: An isolated high-frequency link AC/AC converter is termed an electronic transformer.The electronic transformer has size and cost advantages over a conventional transformer because of high-frequency operation of the magnetic core. Of the various topologies of electronic transformer, the high-frequency AC link electronic transformer achieves high-frequency AC power transformation without a DC link. The circuit uses the standard H-bridge, one on either side of the high-frequency transformer. A novel PWM scheme is proposed, which symmetrically delays and advances the phase of the left and right legs of the front-side converter with respect to the output side converter. The proposed scheme introduces free wheeling sub-periods, which results in zero voltage switching in the output-side converter. The electronic transformer as an AC automatic voltage regulator (AVR) offers distinct advantages over a conventional servo voltage stabiliser in terms of size and speed of response. The AVR application is discussed and experimental results of a 500VA AVR are presented. A four-quadrant switch presents difficulties in turning off inductive load current because of the absence of a free wheeling path in the switch. A biasing circuit is proposed to convert the potentially lossy switching transition into lossless transition. Simulation and experimental results with the biasing circuit are presented.

Zero-Voltage Transition Flyback Inverter for Small Scale Photovoltaic Power System

Abstract: A zero-voltage transition (ZVT) flyback inverter is proposed. The current in the flyback transformer is controlled in the fixed frequency, and the pulse width is varied to make the inductor current sinusoid. In order to reduce switching losses and noises, a soft-switching technique is adopted. The soft-switching technique is called the switched snubber circuit or the primary current steering technique. It is suitable for the pulse-width modulation (PWM), because the time of the resonant transition is very short and the time is independent of the switching frequency. A laboratory prototype using a digital controller for the ZVT flyback inverter was built. From the simulation using the PSPICE and experimental results, the zero-voltage transition operation of the main switch is confirmed. The proposed inverter is suitable as a power conditioner for PV power systems

Theory of electrothermal behavior of bipolar transistors: Part I -single-finger devices

Abstract: A detailed theoretical and numerical analysis of the electrothermal behavior of single-finger bipolar transistors is proposed. Two models of different complexities are introduced to investigate self-heating effects in bipolar junction transistors (BJTs) and heterojunction bipolar transistors (HBTs) biased with a constant base-emitter voltage source or with a constant base current source. In the constant base-emitter voltage case, simple relations are derived for determining the onset of the flyback behavior in the output characteristics which defines the boundary of the safe operating region. The model indicates that the flyback behavior disappears at high V/sub BE/ values, and predicts a thermal hysteresis phenomenon at high currents. It is also shown that at high current levels the electrothermal behavior is dominated by ohmic base pushout. If a constant base current is applied, the model shows that both BJTs and HBTs are unconditionally thermally stable. The transient behavior is also considered, and the temperature evolution is investigated for different bias conditions. The model shows that, if the device is biased in the thermally unstable region, thermal breakdown occurs within a finite time instant in the limit case of a zero ballast resistance. Finally, the reduction in the safe operating area due to avalanche effects and to the temperature dependence of thermal conductivity is discussed, and a simplified model is proposed.

Mode transformer for miniaturized optical circuits

Abstract: A novel mode transformer was fabricated that transforms a modal area by a factor of 100. Using the mode transformer improves the efficiency of mode transformation by an order of magnitude compared with that when no mode transformer is used. With this mode transformer, input–output coupling of miniaturized, on-chip integrated optical circuits to external optical fibers is achieved with low loss. The mode transformer’s design, fabricated in silicon, is scalable to virtually any waveguide size, facilitating continuous miniaturization in silicon optoelectronics.

Analysis, design and implementation of an active clamp flyback converter

Abstract: This paper presents the detailed circuit operation, mathematical analysis, and design example of the active clamp flyback converter. The auxiliary switch and clamp capacitor are used in the flyback converter to recycle the energy stored in the transformer leakage in order to minimize the spike voltage at the transformer primary side. Therefore the voltage stress of main switch can be reduced. The active clamped circuit can also help the main switch to turn on at ZVS using the switch output capacitor and transformer leakage inductance. First the circuit operation and mathematical analysis are provided. The design example of active clamp flyback converter is also presented. Finally the experimental results based on a 120 W prototype circuit are provided to verify the system performance

Flexible and low cost design for a flyback AC/DC converter with harmonic current correction

Abstract: This study presents a new simple flyback ac/dc converter with harmonic current correction and fast output voltage regulation. In the proposed ac/dc converter, an extra winding wound in the transformer provides two key advantages. The size of the bulk inductor used in the conventional boost-based power factor correction cell can be significantly reduced in the proposed converter. The voltage across bulk capacitor can be held under 450V by tuning the transformer winding ratio even though the converter operates in a wide range of input voltages (90 V/spl sim/265V/ac). This new converter complies with IEC 61000-3-2 under the load range of 200 W, and can achieve fast output voltage regulation.

Switching power device

Abstract: A switching power device uses a non-capacitor flyback converter circuit not provided with a smoothing input capacitor having a large capacity. Therefore, a power harmonic can be suppressed and a rush current preventing element is not required. A fluctuation in an output current to be supplied to a load is fed back to the non-capacitor flyback converter circuit by a feedback circuit at a lower speed than an input AC frequency. Therefore, it is possible to improve a power factor by causing an input AC current to be proportional to an input AC voltage. A voltage control circuit controls an output voltage so as to have a constant voltage, and the output voltage is dropped in proportion to an output current when the output current exceeds a threshold. Therefore, it is possible to have the same output characteristic as a power device comprising a low frequency power transformer.

3-D nonlinear transient eddy current calculation of online power transformer under DC bias

Abstract: This paper presents a new method to analyze the three-dimensional (3-D) nonlinear transient eddy currents and losses of an online transformer in a power system under direct current bias. In the method, power system simulation is incorporated with 3-D field computation to obtain the magnetic parameters and the equivalent exciting source of the online transformer.

Analysis of the contactless power transfer system using modelling and analysis of the contactless transformer

Abstract: In this paper, the electrical characteristics of the contactless transformer is presented using conventional coupled inductor theory. Compared with the conventional transformer, a contactless transformer has large airgap, long primary wire and multi-secondary wire. So contactless transformer has large leakage inductance, small magnetizing inductance and poor coupling coefficient. Therefore, large magnetizing current flows through entire primary system due to small magnetizing inductance and the overall system efficiency will be low. In high power applications, contactless transformer is so bulky and heavy that it should be split by some light and small transformers. So contactless transformer needs several small transformer modules which are connected series or parallel to transfer the primary power to the secondary one. This paper shows analysis and measurement results of the each contactless transformer module and comparison results between series-connection and parallel-connection of the contactless transformer. The results are verified on the simulation based on the theoretical analysis and the 30 kW experimental prototype

A novel low-cost electronic ballast to supply metal halide lamps

Abstract: This paper presents a novel single-stage electronic ballast with high power factor. The ballast circuit is based on the integration of a buck converter to provide the power factor correction and a flyback converter to control the lamp power and to supply the lamp with a low frequency square-waveform current. Both converters work in discontinuous conduction mode, which simplifies the control. In spite of being an integrated topology, the circuit does not present additional stress of current in the main switch, which handles only the flyback or buck current, depending on the operation mode. In order to supply the lamp with a low frequency square-wave current, to avoid acoustic resonances, the flyback has two secondary windings that operate complementary at low frequency. Results of acoustic resonances excited by the high-frequency ripple in the square waveform applied to the lamp are presented, in order to design the circuit. The design procedure of the converters is also detailed. Experimental results from a 35 W metal halide lamp are presented, where the proposed ballast reached a power factor of 0.956, a total harmonic distortion of 30%, complying with IEC 61000-3-2, and an efficiency of 90%.

Single-stage buck-boost inverter

Abstract: An improved Single-Stage Buck-Boost inverter (S2B2 Inverter) is provided, using only three or four power semiconductor switches and two coupled inductors in a flyback arrangement. The inverter can handle a wide range of do input voltages and produce a fixed ac output voltage. The inverter is well suited to distributed power generation systems such as photovoltaic and wind power and fuel cells, for standalone or grid connected applications. The inverter has a single charge loop, a positive discharge loop and a negative discharge loop.

Power transformer temperature evaluation for overloading conditions

Abstract: The calculation methodologies of transformers' hottest spot and top oil temperatures are evaluated in this paper. Thereafter, a comparison between the calculated and the values obtained during the assessment of a transformer factory test was realized. The referred tests were conducted using an ONAF type, 30/40 MVA, 138/13.8 kV transformer, in which sensors with fiber-optic cables, to record directly the internal parameters, were installed. In a first series of tests, transformer loadings corresponding to 100%, 70% and 116.5% of rated power, were used. The tests were completed by applying values of a daily load profile with several hourly power levels. Additionally, in two of the hourly periods, high temporary loadings one of 160% during 30 minutes, and another of 170% during 15 minutes, were applied.

AC/DC converter with power factor correction

Abstract: A switch mode AC/DC converter with input current shaped for unity power factor. Input current is modulated by input voltage, and input inductor and isolation transformer are driven with the same duty ratio, with a low voltage across bulk capacitor. This voltage is determined only by input voltage amplitude. Energy stored in the leakage inductance of the transformer is returned back to the internal DC source. A soft switching circuit is connected to the primary side, eliminating the need for high side drive. Sources of the main and auxiliary switches and primary winding of the transformer are connected to ground for easy primary voltage sensing. Overvoltage protection circuit of the output is connected to exclusively primary side signals. Secondary synchronous rectifier is driven by a circuit synchronized with the system clock. The circuit can be coupled to either the primary or the secondary winding of the isolation transformer.

Rectifier for reducing current harmonics from unbalanced source

Abstract: A rectifier includes a transformer, a rectifying bridge, a link capacitor, and at least a first resonance loop. The transformer is operable to receive three phase input signals having a source frequency and generate a plurality of transformer phase signals. The rectifying bridge has a number of stages corresponding to the number of transformer phase signals and is operable to generate a rectified output signal based on the transformer phase signals. The link capacitor is coupled across the rectifying bridge. The first resonance loop is coupled between the rectifying bridge and the link capacitor. The first resonance loop has a first resonance frequency corresponding to a harmonic frequency of the source frequency.

A transformer comparison for three-phase single active bridges

Abstract: This paper investigates the impact of the transformer configuration on the performance of the three-phase single active bridge The investigated configurations are a wye-wye connected transformer, a wye-delta connected transformer and a delta-wye connected transformer The converter's operation is described in detail for all transformer configurations Voltage and current waveforms of all converter components are derived analytically Furthermore, current and voltage stresses of the converter components are compared and the advantages and disadvantages of the different transformer configurations are discussed The comparison shows large difference of the voltage and current stresses for the different configurations resulting in a large deviations in power density and efficiency Experimental results taken from a 5 kW / 80 kHz laboratory breadboard three-phase single active bridge verify the analysis

Pulse regulation control technique for integrated high-quality rectifier-regulators

Abstract: The pulse regulation control scheme is presented and applied to the boost integrated flyback rectifier/energy storage dc/dc (BIFRED) converter as the most popular member of the integrated high-quality rectifier-regulators (IHQRR). In contrast to the conventional control techniques, the principal idea of pulse regulation is to regulate the output voltage using a series of high- and low-power pulses generated by the current of the input inductor, which is operating in discontinuous conduction mode (DCM). Analysis of the BIFRED converter operating in DCM is presented. Fundamentals of pulse regulation as well as its stability analysis and the estimation of the output voltage ripple are introduced. Experimental results on a prototype converter are also presented to validate the analytical and simulation results.

Device and method for equalising the charge of serially connected capacitors belonging to a double layer capacitor

Abstract: A device and a method are provided for equalizing the charge of the capacitors belonging to a double layer capacitor. The device includes an individual transformer associated with each individual capacitor and a flyback transformer or a spool, from which the energy is transferred, via the individual transformers, to the individual transformer, by the respective low charge. Conclusions on the state of the double layer capacitor and the charge-equalizing switch are derived from the measured charging time and discharging time of the flyback transformer.

Suitability of pulse train control technique for BIFRED converter

Abstract: Pulse Train/spl trade/ control scheme is presented and applied to a boost integrated flyback rectifier/energy storage dc-dc (BIFRED) converter operating in discontinuous conduction mode (DCM), which avoids the light-load high-voltage stress problem. In contrast to the conventional control techniques, the principal idea of Pulse Train technique is to regulate the output voltage using a series of high and low energy pulses generated by the current of the inductor. The applicability of the proposed technique to both the input and magnetizing inductances of BIFRED converter is investigated. Analysis of BIFRED converter operating in DCM as well as the output voltage ripple estimation is given. Experimental results on a prototype converter are also presented.

The Research on Characteristics of Electronic Power Transformer for Distribution System

Abstract: The 3-phase and 4-wire distribution electronic power transformer (D-EPT) is composed of the input three phase PWM rectifier, medium frequency transformer and output single phase inverters. In this paper, the operation principle of D-EPT is analyzed and its control scheme is designed. For the PWM rectifier, an outer loop control of the DC voltage and an inner loop control of AC current are adopted. Then, a dual-loop control is implemented for the output inverters based on the RMS value and instantaneous value of output voltage respectively. The simulation results show that D-EPT has good steady-state and dynamic load characteristics under the proposed control scheme

Design and control of a current source flyback inverter for decentralized grid-connected photovoltaic systems

Abstract: This paper presents a new design and control strategy of the flyback inverter for decentralized grid-connected PV systems, in order to achieve high power density, high efficiency, and high power factor regulation. The design and control methodology which are investigated are aiming either to the achievement of a converter with the smallest possible volume for a given power or to the maximization of the power transfer that can be achieved for given converter parameters. The validation of the proposed design and control methodology will be confirmed by experimental results accomplished on a laboratory prototype

Magamp application and limitation for multiwinding flyback converter

Abstract: A new magamp technique for multiwinding flyback converters is proposed. Ideal operating principle and analysis are presented. The practical circuit operation is limited due to the nonideal component characteristics. An analytical model for studying the phenomenon is provided. Based on the model, the mechanism of the boundary condition that causes the converter to be out of regulation is explored. Experimental verifications on a 20 W two-output flyback converter are conducted. They illustrate the effectiveness of the proposed magamp approach and the accuracy of the presented analytical model.

Transformer interface for preventing EMI-based current imbalances from falsely triggering ground fault interrupt

Abstract: A transformer interface prevents a false ground fault interrupt in a power supply arrangement. The power supply arrangement has a line wire and a neutral wire connected by way of a ground fault interrupt circuit to an electrically powered device, to which a ground wire is also coupled. The interface has current imbalance sensor transformer windings coupled to the line and neutral wires. A ground wire current sensor transformer winding is coupled to the ground wire. A detector transformer winding produces a signal that triggers operation of the ground fault interrupt circuit, in response to the difference between currents produced by the current imbalance sensor transformer windings exceeding detected ground wire current by a prescribed value.

Energy-saving Flyback Converter for EDM Applications

Abstract: Electrical discharge machining (EDM) uses controlled electric sparks to erode the metal in a workpiece, and this method is now a well established machining process for high power applications. EDM power supplies utilizing different topologies for high power applications (e.g. full bridge configuration) are widely available. Through the years, EDM processes have increasingly been used in high precision machining and in manufacturing micromechanical components, with new low power topologies being investigated for the latter. We implemented a current mode flyback converter for use in low power EDM applications. This topology has an energy conservation feature and removes the need for output bulk capacitors. Energy used in the erosion process will come from the energy stored in the flyback transformer and will be transferred to the small output filter capacitors and the effective capacitance of the tool, workpiece, and dielectric combination. A servomechanism that controls the arc distance will determine the output voltage. We have developed an EDM power supply prototype utilizing the flyback topology for low power applications with minimal components count and inherent protection under short circuit conditions. Our work includes the design, fabrication, and characterization of the whole system. We compared the efficiency and quality of work of our proposed topology with that of a linear converter.

Multiphase transformer for a multiphase dc-dc converter

Abstract: A multiphase DC-DC converter is provided that includes a multiphase transformer, the multiphase transformer including a plurality of input voltage terminals and an transformer output voltage terminal, each input voltage terminal associated with a corresponding phase Each phase is assigned to an input voltage terminal of the plurality of input voltage terminals to minimize a ripple current at the input voltage terminals of the multiphase transformer