Showing papers on "Flyback transformer published in 2004"

Active voltage clamp in flyback converters operating in CCM mode under wide load variation

Abstract: Active clamp topologies of low power dissipation have become a very attractive solution in order to limit overvoltages in flyback converters. Although many suitable topologies have been introduced for the case of discontinuous conduction mode (DCM), where the duty cycle value depends on the load level, in continuous conduction mode (CCM) it is more difficult to appropriately design such topologies so as to "sense" load changes-due to the small duty cycle divergence under wide load variation. Taking for granted that in order to achieve high power-factor correction in these converters, CCM is a more attractive mode of operation, a drastic solution for this case that will manage to eliminate voltage stresses under wide load changes has become very essential. For this purpose, this paper presents an active clamp topology with small power dissipation, suitable for flyback converters operating in CCM mode. Its main idea is the use of a load-dependent current source, consisting of an auxiliary converter operating in DCM mode. Experimental results highlight the effectiveness of the proposed topology under wide load changes, establishing it as an appropriate solution in order to develop flyback converters, even at the power range of 500 W.

Multilevel converter based intelligent universal transformer

Abstract: A multilevel converter-based, intelligent, universal transformer includes back-to-back, interconnected, multi-level converters coupled to a switched inverter circuit via a high-frequency transformer. The input of the universal transformer can be coupled to a high-voltage distribution system and the output of the universal transformer can be coupled to low-voltage applications. The universal transformer is smaller in size than conventional copper-and-iron based transformers, yet provides enhanced power quality performance and increased functionality.

PWM controller for synchronous rectifier of flyback power converter

Abstract: A synchronous rectifier PWM (SR-PWM) controller controls a MOSFET in response to the value of a secondary current and the status of a synchronous signal for both discontinuous and continuous operation mode. The secondary current is generated in a secondary circuit and is detected by two threshold-detection terminals of the SR-PWM controller. The SR-PWM controller produces the synchronous signal by detecting a switching signal of the transformer via a detection terminal of the SR-PWM controller. Furthermore, a delay-time is inserted after the MOSFET is turned off and before the next switching cycle starts to ensure a proper operation of the MOSFET. In one embodiment, an equivalent series resistance (ESR) of an output capacitor can be used as a sensor to detect the secondary current. Therefore, no additional current sensor is required and the efficiency can be improved.

A ZCS bidirectional flyback DC/DC converter

Abstract: This paper addresses the design and analysis of a zero-current-switched (ZCS) bidirectional flyback dc/dc converter. The converter is based on extending a previously developed unidirectional ZCS flyback converter and replacing the output diode with a controlled switch, which acts as either a rectifier or a power control switch in the corresponding power flow direction. By adding an auxiliary winding in the coupled inductor, a switch, and a capacitor, the hard-switching design is converted into a soft-switching one. The technique utilizes the leakage inductance of the flyback coupled inductor to create zero-current-switching conditions for all switches in both power flow directions, leading to reduced switching losses, stresses, and electromagnetic interference. The operating principles of the converter and experimental results have been presented.

Multifunction hybrid intelligent universal transformer

Abstract: A multifunction hybrid intelligent universal transformer includes a conventional transformer coupled with power electronics on the secondary side to enhance the functionality of power conversion. The universal transformer includes features for overcoming the deficiencies associated with conventional transformers, including voltage sag compensation, instantaneous voltage regulation, outage compensation, capacitor switching protection, harmonic compensation, single-phasing protection, DC output, and variable frequency output.

Design considerations for a medium frequency transformer in a line side power conversion system

Abstract: Design considerations are presented for a medium frequency transformer in a line side power conversion system for electric railway traction. The system employs soft commutation in order to reduce switching losses and allow for high operating frequency of the transformer. Two different designs are evaluated; The first one is dry insulated and the second one is liquid-immersed. Calculations indicate that a 1 MVA transformer operating at 4 kHz could be realized with an active weight of below 150 kg for both dry and liquid-immersed transformer concepts. The transformers are modeled magnetically, electrically and thermally, and a geometric optimization procedure based on a cost function is applied to achieve an optimum design.

Dc-to-dc converter

Abstract: A dc-to-dc converter includes a transformer having a primary winding connected to an input rectifying and smoothing circuit via an FET or like switching device, and a secondary winding connected to an output rectifying and smoothing circuit A resonance capacitor is connected in parallel with the switching device A switch control circuit cyclically turns the switching device on and off so as to keep constant the output voltage of the output rectifying and smoothing circuit by feedback control The switch control circuit drives the switching device in light load mode when a flyback voltage developed by the transformer terminates earlier than each clock pulse, and in heavy load mode, in which each on-off cycle of the switching device is longer than in the light load mode, when the flyback voltage terminates later than each clock pulse

A parallel-connected single phase power factor correction approach with improved efficiency

Abstract: In this paper, a new parallel-connected single phase power factor correction (PFC) topology using two flyback converters is proposed to improve the output voltage regulation with simultaneous input power factor correction and control. This approach offers lower cost and higher efficiency by parallel processing of the total power. Flyback converter-I primarily regulates output voltage with fast dynamic response and processes 55% of the power. Flyback converter-II with ac/dc PFC stage regulates input current shaping and PFC, and processes the remaining 45% of the power. This paper presents a design example and circuit analysis for 200 W power supply. A parallel-connected interleaved structure offers smaller passive components, less losses even in continuous conduction inductor current mode, and reduced volt-ampere rating of dc/dc stage converter. TI-DSP, TMS320LF2407, is used for implementation. Simulation and experimental results show the performance improvement.

Feedback compensation design for switched mode power supplies with a right-half plane (RHP) zero

Abstract: A boost and flyback converters operating in Continuous Conduction Mode (CCM) are notorious for their difficult control loop stabilisation and sluggish response. This paper describes feedback' compensation design of these converters. Design of the two selected compensation circuits is illustrated with a CCM boost converter, with experimental results given to verify effectiveness of each compensation circuit.

Dc-to-dc converter with flyback period detector circuit

Abstract: A dc-to-dc converter includes a transformer having a primary winding connected to an input rectifying and smoothing circuit via an FET or like switching device, and a secondary winding connected to an output rectifying and smoothing circuit. A resonance capacitor is connected in parallel with the switching device. A switch control circuit cyclically turns the switching device on and off so as to keep constant the output voltage of the output rectifying and smoothing circuit by feedback control. The switch control circuit drives the switching device in light load mode when a flyback voltage developed by the transformer terminates earlier than each clock pulse, and in heavy load mode, in which each on-off cycle of the switching device is longer than in the light load mode, when the flyback voltage terminates later than each clock pulse.

DC to DC converter with high frequency zigzag transformer

Abstract: A DC to DC converter including a zigzag transformer. The transformer operates at high frequency with integrated magnetics and does not provide isolation. The multiphase converter has gate inputs with PWM signals appropriately phase-shifted depending on the number of phases to make balanced phase voltages across the transformer windings. The switching frequency of the converter is relatively low but fast transient response can be achieved by adding an integrated zigzag transformer.

Fabrication and characteristics of PDA LCD backlight driving circuits using piezoelectric transformer

Abstract: In this paper, to apply piezoelectric transformer for personal digital assistants (PDA) liquid crystal display (LCD) backlight driving circuits, piezoelectric transformer using 0.3 wt.% Nb2O5 added PNW-PMN-PZT ceramics was fabricated as Rosen-type one with the size of 1 mm ×16 mm ×5 mm, and their electrical characteristics were investigated with the variations of load resistance and driving frequency. Then, the PDA LCD backlight driving circuits was manufactured using piezoelectric transformer, two MOSFET connected in series, voltage control oscillator (VCO) and one-chip microprocessor. After driving LCD backlight for 25 min using the proposed circuit, at driving frequency of 214.4 kHz, input voltage of 31.78 V and input current of 21.1 mA were measured at the input part of piezoelectric transformer. Then, output voltage of 293.2 V and output current of 2.2 mA were shown at the output part of piezoelectric transformer. At the same time, efficiency of 96.2% and temperature rise of 3.6 °C were appeared at the piezoelectric transformer.

Three-phase synchronous PWM for flyback converter with power-factor correction using FPGA ASIC design

Abstract: The design and development of a synchronous pulsewidth modulation (PWM) generator suitable for the three-phase flyback converter with transformer isolated and power-factor correction using a field-programmable gate array is proposed. The proposed three-phase synchronous PWM makes it possible for the converter to obtain the sinusoidal supply currents with a near-unity power factor. A high-frequency transformer is considered in the design to provide galvanic isolation and serves the dual role of inductor and transformer. Results are provided to demonstrate the effectiveness of the design.

Driver for high efficiency LED based on flyback stage with current mode control for emergency lighting system

Abstract: Nowadays, permanent emergency lighting systems (PELS) are widely used in many applications: emergency exit indication, lighting in critical or strategic points. Limitation in operation hours in classical lamps (10.000-20.000 hours for fluorescent lamps) implies short lamp replacement times and, therefore, high maintenance costs. This paper shows a driver based on a flyback circuit for a PELS system. Control in current mode operation assure current constant in LED's in any battery condition. The long operation life (above 100.000 hours) of high efficiency LED's with a very simple electronics circuitry implies an interesting solution for this type of applications. A 30 lumens and 1 hour PELS has been built and tested.

Harmonic nonlinear transformer modeling

Abstract: This paper proposes a new saturated single-phase transformer model and a three-phase three-legged transformer model for their implementation in a harmonic load flow. The nonlinear magnetizing behavior of the transformer is represented in both models by a simple saturated reluctance function. The procedure for the nonlinear magnetizing current calculation is described. The model incorporation into the harmonic load flow is also analyzed. Simulations have been developed in order to show the performance of the proposed models, and have been compared with real measurements.

On the effects of voltage subharmonics on power transformers: a preliminary study

Abstract: In this paper the effects that voltage subharmonics have on power transformers are presented. The work tackles the basic case of a single phase transformer and the phenomenon of hysteresys loop asymmetrization and core saturation is focused on. Experimental results together with simulation results, both in time domain and frequency domain, are utilized for a first insight into the physical phenomenon and for sensitivity analyses.

Transient characteristics of high-voltage flyback transformer operating in discontinuous conduction mode

Abstract: Modelling and analysis of the high-voltage flyback transformer utilised in small-sized high-voltage power supplies are presented. The equivalent circuit model, frequency characteristics and transient behaviour are investigated to analyse the effects of parasitic parameters in the discontinuous conduction mode. Simulation and experimental results are provided to show the validity of the analysis.

Method and circuit for regulating power in a high intensity discharge lamp

Abstract: A circuit for controlling power to a high intensity discharge lamp is disclosed. The circuit according to one embodiment of the invention comprises a rectifier circuit coupled to receive an alternating current line voltage, and a boost/flyback converter coupled to the rectifier circuit which outputs a regulated DC bus voltage. A power control circuit also couples a feedback signal to the boost/flyback converter to regulate the power output of the boost/flyback converter. A method of controlling power to a high intensity discharge lamp is also disclosed. The method comprises steps of generating a DC voltage for the high intensity discharge lamp by way of a boost/flyback converter; monitoring the DC voltage and the current generated in the boost/flyback converter; and modifying the power output by the boost/flyback converter to regulate power based upon the voltage and the current.

The role of parasitic inductance in high-power planar transformer design and converter integration

Abstract: Planar transformers provide a distinct advantage over the traditional transformer. However, when the planar transformer is integrated into a power circuit, the interconnect parasitic effects arise that are not shown in a traditional wire-wound transformer. For typical soft-switching converters, a specific leakage inductance is generally needed to charge and discharge the device output capacitances to achieve zero-voltage turn on. This designated leakage inductance value needs to be large enough to extend the zero-voltage switching range. However, it was found that this hard-to-come-by leakage inductance in a planar structure may be overshadowed by the circuit interconnect parasitic inductance. This paper presents a design integration that incorporates the planar transformer and a full-bridge dc/dc converter. Through design calculation, finite element analysis, and experimental verification, it was proven that the role of the parasitic inductance is indeed far exceeding the transformer leakage inductance. Thus, for any design optimization, it is necessary to take into account the parasitic inductance in the integrated structure.

Systems and methods for driving large capacity AC motors

Abstract: A drive system for driving large capacity motors includes a motor and a variable frequency drive which accepts input from a three-phase power source. The drive system includes a step-up transformer, preferably of a high-capacity three-phase type, positioned between and electrically connected to the motor and the variable frequency drive to thereby step-up voltage received from the variable frequency drive to be supplied to the motor. The transformer includes a transformer chamber formed in the transformer tank containing a cooling fluid for cooling transformer internal components. A plurality of inductors forming part of a harmonic filter are positioned within the transformer chamber such that they can be protected from the environment and simultaneously cooled with other transformer internal components by the dielectric fluid. The filter includes capacitors that are preferably mounted outside of the tank.

A highly efficient contactless electrical energy transmission system

Abstract: This paper proposes a new concept for contactless electrical energy transmission system for an elevator and an automated guided vehicle. The system has rechargeable batteries on the car and electrical energy is supplied at a specific place. When electric power is supplied to the car, it runs automatically and approaches the battery charger. Therefore, a comparatively large gap is needed between the primary transformer at the battery charger and the secondary transformer on the car in order to prevent damage which would be caused by a collision. In this case, a drop of the transformer coupling rate due to the large gap must be prevented. In conventional contactless electrical energy transmission technology, since electric power is received by a pickup coil from a power line, a large-sized transformer is required. When the distance over which the car runs is long, the copper loss of the line also increases. The developed system adopts a high-frequency inverter using a soft switching method to miniaturize the transformer. The system has a coupling rate of 0.88 for a transformer gap length of 10 mm and can operate at 91% efficiency. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 66–74, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10290

Novel soft-commutation DC-DC power converter with high-frequency transformer secondary side phase-shifted PWM active rectifier

Abstract: This paper presents a novel circuit topology of the voltage source type zero voltage soft-switching (ZVS) full bridge DC-DC power converter with an isolated high-frequency transformer, which incorporates zero-current soft-switching (ZCS) phase-shifted (PS)-PWM active power switches in series with diodes of two bridge arms of a full-bridge rectifier on the high-frequency transformer secondary side. This high-frequency linked DC-DC power converter can achieve ZVS for noncontrolled active power switches on the primary side of the transformer and ZCS for PS-PWM active switches on the secondary side of the transformer under wide load variations as well as a wide PS-PWM regulation range. The switching power losses and conduction power losses of the active devices of the proposed DC-DC converter can be considerably reduced. The proposed DC-DC converter blocks circulating current flowing through the semiconductor switching devices on the transformer primary side as compared to the lossless snubbing capacitor and transformer leakage and magnetising inductor-assisted soft-switching full-bridge DC-DC converter with ZVS PS-PWM scheme on the transformer primary side. The steady-state operating principles of the proposed DC-DC converter are evaluated and discussed, based on the simulation and experimental results obtained from a 2 kW-40 kHz breadboard set-up using IGBTs.

Integrated magnetic isolated two-inductor boost converter

Abstract: A two-inductor boost converter includes an integrated magnetic core having a three-legged flux-conducting element with an energy-storing gap, for example in the center leg. Two primary windings are disposed on respective legs, such as the outer legs, and are coupled in parallel to one input terminal of the converter. Two series-connected secondary windings are also disposed on the flux-conducting element, and are connected to rectification and filtering circuitry which may have full bridge, full wave, or voltage doubler configuration. Primary-side switches are coupled in series between each primary winding and the other converter input terminal. Control circuitry generates control signals for the primary-side switches, providing for a desired degree of overlapped conduction during each operating cycle along with periods of non-conduction that result in transferring electrical energy to the load. The integrated magnetic core can include additional windings for ancillary functions, such as for flyback operation during start-up.

High-frequency flyback-type soft-switching PWM DC-DC power converter with energy recovery transformer and auxiliary passive lossless snubbers

Abstract: A two-switch high-frequency flyback-type zero voltage soft-switching PWM DC-DC power converter for use in auxilary power supplies is proposed. Its basic building block is composed of two active power switches and a flyback high frequency transformer. In addition, two passive lossless snubbers with power regeneration loops for energy recovery that consist of a three-turn auxiliary high frequency transformer, auxiliary capacitors and diodes, are introduced to achieve zero voltage soft switching in the full range of light to full load conditions. The power converter has the advantages of a low cost circuit configuration, a simple control scheme and a high efficiency.The converter's operating principle is described and to in order determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and is compared to a hard-switching PWM DC-DC converter. The comparative electromagnetic conductive noise characteristics of both DC-DC power converter circuits are also investigated.

Single stage PFC power converter

Abstract: A single stage PFC power converter is provided for performing a PFC function in a half-bridge flyback power converter. A high-side switch and a low-side switch periodically supply an input voltage to a primary winding of a transformer. When the high-side switch and low-side switch are switched off, the energy stored in the transformer will be transmitted to a secondary circuit and charged to a bulk capacitor. The bulk capacitor serves to recycle the energy and reduce the output ripple noise. A forward diode and a forward inductor serve to forward the energy of the bulk capacitor to the flowing path of the input voltage for performing PFC function.

Method and apparatus for extending the operating range of a flyforward converter

Abstract: A technique for extending the operating range of a flyforward converter to low input voltages. In one aspect, power converter includes a positive input supply rail and a negative input supply rail. A power converter input voltage is to be applied between the positive and negative input supply rails. A flyback energy transfer element having a flyback input winding and a forward energy transfer element having a forward input winding are also included. The flyback and forward input windings are coupled between the positive and negative input supply rails. Voltage control circuitry coupled to the forward energy transfer element is also included to reduce a voltage across the forward input winding, substantially to zero, when the power converter input voltage falls below a first threshold value.

Positive and negative excitation bidirectional DC-DC converter

Abstract: The invention relates to a forward-flyback two-way DC-DC converter, composing a forward transformer by coupling secondary and primary windings; composing a flyback transformer by coupling another secondary and primary windings, where the two secondary windings are connected in series with the two switches tubes, respectively, and then connected in parallel with a DC power supply. The two primary windings are connected in series and then connected in parallel with a DC power supply through rectifier/inverter. It uses active clamping, RCD clamping, LCD clamping, ZVT and other techniques to compose a family of two-way converter topologies. It uses the forward transformer and a coupling inductance together to transmit energy, solving the defect in using transformer leakage inductance or coupling inductance to transmission energy; avoids the peak problem in current topologies in existing techniques; has the advantages of small current ripple, implementing soft switch for each switch tube, etc.

Protection schemes for various fault conditions for off-line flyback converters

Abstract: Recently, most electronics manufactures require high reliability of switched mode power supply against various fault situations such as over load, output short or rectifier diode short. This paper presents simple and effective protection schemes for the off-line flyback converter. The proposed protection schemes can protect the power MOSFET from various abnormal conditions. The validity and effectiveness of the proposed schemes are verified through experimental results.

Estimation of core loss of transformer under non-sinusoidal voltage supply

Abstract: This paper presents the 1-phase transformer core loss estimation under non-sinusoidal voltage supply. The Epstein test apparatus, with grain oriented magnetic steel side MS (0.3 mm), inverter and low pass filter is used in estimation of core loss. The calculated results are compared with the measured value and are useful for the appropriate single-phase transformer design under non-sinusoidal voltage supply.