Showing papers on "Flyback converter published in 1997"

Single-phase matrix converter

Abstract: A topology of a single-phase AC/AC direct power converter is presented. The circuit, composed from four ideal power switches, is used as a frequency step-up converter. The equations of the proposed converter are developed, its switching angle pattern is calculated and the dynamic behaviour of the system is simulated. Using a power MOSFET and four Schottky diodes, the basic power switch is assembled and a power converter fed from 50 V (RMS), 50 Hz, supplying a passive R, L load operated at 100 Hz, was constructed. Satisfactory agreement between simulated and laboratory results was observed.

Design and Analysis of Piezoelectric Transformer Converters

Abstract: Piezoelectric ceramics are characterized as smart materials and have been widely used in the area of actuators and sensors. The principle operation of a piezoelectric transformer (PT) is a combined function of actuators and sensors so that energy can be transformed from electrical form to electrical form via mechanical vibration. Since PTs behave as band-pass filters, it is particularly important to control their gains as transformers and to operate them efficiently as power-transferring components. In order to incorporate a PT into amplifier design and to match it to the linear or nonlinear loads, suitable electrical equivalent circuits are required for the frequency range of interest. The study of the accuracy of PT models is carried out and verified from several points of view, including input impedance, voltage gain, and efficiency. From the characteristics of the PTs, it follows that the efficiency of the PTs is a strong function of load and frequency. Because of the big intrinsic capacitors, adding inductive loads to the PTs is essential to obtain a satisfactory efficiency for the PTs and amplifiers. Power-flow method is studied and modified to obtain the maximum efficiency of the converter. The algorithm for designing a PT converter or inverter is to calculate the optimal load termination, Y OPT , of the PT first so that the efficiency (power gain) of the PT is maximized. And then the efficiency of the dc/ac inverter is optimized according to the input impedance, Z IN , of the PT with an optimal load termination. Because the PTs are low-power devices, the general requirements for the applications of the PTs include low-power, low cost, and high efficiency. It is important to reduce the number of inductive components and switches in amplifier or dc/ac inverter designs for PT applications. High-voltage piezoelectric transformers have been adopted by power electronic engineers and researchers worldwide. A complete inverter with HVPT for CCFL or neon lamps was built, and the experimental results are presented. However, design issues such as packaging, thermal effects, amplifier circuits, control methods, and matching between amplifiers and loads need to be explored further. iii Acknowledgments I would like to thank my advisor, Dr. Fred C. Lee, for his support and guidance during the course of this research work. Without his constant correction on my research attitude, I would have never accomplish this work. I would like to express my boundless gratitude to my beloved wife, Kuang-Fen, …

DC/AC power converter

Abstract: A DC link power converter apparatus including a first DC to DC converter, a DC to AC converter and a load balancing storage element. The first DC to DC converter has first and second DC ports and the DC to AC converter has a third DC port and has an AC port. The first DC port is connectable to a DC source and the second DC port is connected to the third DC port. The AC port is connectable to an AC load. The load balancing energy storage element is connected to the second DC port for decoupling the DC to DC converter from the DC to AC converter by supplying energy to the third DC port when a voltage at the second DC port is tending to decrease and for storing energy received from the second DC port when a voltage at the third port is tending to increase.

A single-switch AC/DC converter with power factor correction

Abstract: A new single-stage, single-switch power factor correction converter with output electrical isolation is proposed in this paper. The topology of this converter is derived by combining a boost circuit and a forward circuit in one power stage. To improve the performance of the AC-DC converter (i.e., good power factor correction, low total harmonic distortion (THD) and low DC bus voltage), two bulk storage capacitors are adopted. Its excellent line regulation capability makes the converter suitable for universal input application. Due to its simplified power stage and control circuit, this converter presents a better efficiency, lower cost and higher reliability. Detailed steady state analysis and design procedure are presented. To verify the performance of the proposed converter, a design example along with P-simulation program with integrated circuit emphasis (PSPICE) simulation and experimental implementation are given. The measured power factor and efficiency are 99% and 87% at low line (i.e. 110 VAC) operation, and 95% and 81% at high line (i.e. 220 VAC) operation, respectively.

Portable power system using DC to DC converter

Abstract: A portable power system for a hand tool employs a high-voltage transmission of power from a battery pack over a cord to a DC to DC converter, which steps the transmission voltage down to rated tool voltage. The system uses a switching transistor to transmit power according to a duty cycle which varies automatically according to tool current draw and voltage. The DC to DC converter employs synchronous rectification with an inductor-capacitor network to transform a duty cycle square wave into DC power. The startup voltage sense feature permits powering up the converter circuitry only when needed. The converter will shut down if no current has been drawn by the tool for a predetermined period of time or if the converter unit is in danger of overheating, as determined by a stored algorithm. The portable power system has safeguards to prevent fouling or shorting in wet environments, is adaptable to left or right handed users, and is physically configurable into a variety of carrying modes.

Feedforward control of DC-DC PWM boost converter

Abstract: A new feedforward control circuit suitable for applications in the dc-dc pulsewidth modulated (PWM) boost converter operated in the continuous conduction mode (CCM) is proposed. Its principle of operation is described, analyzed for steady state, and experimentally verified. The peak value of the sawtooth voltage at the noninverting input of a PWM modulator is held constant and the voltage at the inverting input of the PWM modulator varies in proportion to the converter dc input voltage. As a result, the complement of the on-duty cycle (1-D) is proportional to the dc converter input voltage, yielding the converter output voltage theoretically independent of the converter input voltage. The circuit is very simple and significantly improves line regulation of the output voltage. The measured open-loop line regulation at fixed loads was less than 5% for the converter dc input voltage change by 400%. The load regulation was also good even without a negative feedback loop.

Interleaved continuous flyback power converter system

Abstract: An interleaved flyback electrical power converter system having a plurality of flyback power converters operated in continuous mode, each converter utilizing a power switch operated under zero voltage switching conditions. The interleaved flyback power converter system is highly efficient and compact, and is suitable for use in high power, high frequency applications.

Method and apparatus for isolated flyback regulator control and load compensation

Abstract: Control circuits for a flyback switching voltage regulator that uses magnetic flux sensing are provided. These circuits include a flyback error amplifier circuit, a logic circuit, and a load compensation circuit. The flyback error amplifier circuit allows a flyback voltage pulse from a primary transformer winding to be employed for output voltage regulation. The logic circuit provides appropriate timing and control signals for the flyback error amplifier circuit. The load compensation circuit compensates for parasitic impedance contributions to the flyback voltage pulse without altering the stability of the flyback regulator.

Anomalous bifurcations in DC-DC converters: borderline collisions in piecewise smooth maps

Abstract: Nonstandard bifurcations have been reported in power electronic DC-DC converters. We show that sampled data models with stroboscopic sampling yield piecewise smooth maps and that most of the observed "anomalous" bifurcations fall into a class called "border collision bifurcations". We offer analytical explanation of the dynamics of three converter topologies (current mode controlled first order buck converter, current mode controlled boost converter, duty cycle controlled buck converter).

Step-up/down DC-to-DC converter

Abstract: A converter for converting a DC voltage not stabilized, such as the terminal voltage of a battery, into a stable DC voltage, comprising a voltage comparison unit (2 in FIG. 1) and an operation changeover control unit (3). The voltage comparison unit (2) compares an input voltage and an output voltage. The operation changeover control unit (3) controls the changeover of the operations of the DC/DC converter (1) so that the DC/DC converter (1) may perform a step-down operation as the operation of a step-down type converter when the input voltage is higher than the output voltage as the result of the comparison, and that it may perform a step-up operation as the operation of a step-up type converter when the output voltage is higher than the input voltage. Thus, losses in the smoothing reactor and smoothing capacitor of the step-up/down converter are suppressed to enhance the efficiency thereof.

Half-bridge zero-voltage-switched PWM flyback DC/DC converter

Abstract: A DC-DC ZVS PWM converter circuit which utilizes the leakage inductance of an output transformer and a three-step operation cycle so as to reduce the voltage stress on the converter power switching transistors and to reduce the EMI noise emissions of the circuit.

High efficiency DC step-up voltage converter

Abstract: A DC power converter is disclosed for converting an input voltage to a final output voltage that is higher than the input voltage. The power converter includes an input terminal for receiving the input voltage and a final output terminal. A boost converter generates an intermediate voltage that is higher than the input voltage and lower than the final output voltage. The boost converter includes an inductor having a primary winding that has a first end connected to the input terminal, a switch for selectively connecting the second end of the first winding to ground, a first diode connected between the second end of the first winding and an intermediate node, and a first output capacitor connected between the intermediate node and ground. The boost converter produces at the first output capacitor an intermediate voltage higher than the input voltage. The step up converter described further includes a second winding on the inductor, a first end of which is connected to receive the intermediate voltage. A diode is connected between the second end of the second winding and the converter output terminal. A second output capacitor is connected between the converter output terminal and ground.

Development and testing of prototype models for a high-performance 300 MW self-commutated AC/DC converter

Abstract: A technical project is under way in Japan to develop a high-performance self-commutated power converter for future HVDC transmission and DC interconnection applications. In the first stage of the project, prototype power converter models for a 300 MW self-commutated converter were developed. The models were subjected to factory testing to verify the technology for series connection of a large number of gate turn-off thyristors (GTOs), a gate power supply from the high voltage main circuit and energy regeneration using snubber circuits. Satisfactory results were obtained.

Two-frequency electronic ballast system having an isolated PFC converter

Abstract: An AC-AC ballast system for a discharge lamp (e.g., a fluorescent lamp), which includes a PFC converter which incorporates an isolation transformer, and a DC-AC inverter provided on the secondary side of the isolation transformer. Because the AC line input is isolated from the lamp load by the transformer in the PFC converter, the switching frequency of the PFC converter can be advantageously significantly higher than the lamp current frequency (and the switching frequency of the DC-AC inverter), to thereby enable a significant reduction in the size and weight of the ballast system, without an increase in the emission of EMI radiation from the lamp. In this regard, the ballast system of the present invention can be thought of as a two-frequency ballast system having an isolated PFC converter.

Single-switch AC/DC converter with power factor correction

Abstract: A single-switch, one-stage power factor correction converter with output electrical isolation is proposed. To relieve the voltage spike caused by the leakage inductance of the power transformer, two bulk storage capacitors are used. The proposed converter has both a good power factor correction and excellent line and load regulation capabilities with an efficiency of 87%.

Analysis and design of a fixed-frequency LCL-type series-resonant converter with capacitive output filter

Abstract: A fixed-frequency modified (LCL-type) series-resonant converter which uses a capacitive output filter is analysed using the Fourier series approach. Based on the analysis a simple design procedure is given. Detailed SPICE simulation results are presented for the designed converter to evaluate its performance for varying input supply voltage and for load variation. Experimental results obtained from a MOSFET based 500 W, 115 V output converter are presented to verify the analysis. The converter operates in lagging power factor mode for a very wide variation in the load and the supply voltage and is suitable for high voltage output applications.

Dual-output dc-dc power supply

Abstract: A multi-output power supply having half-brick dimensions includes a forward converter circuit which receives a DC input voltage and in response to a first control signal generates a first DC output voltage at a first level; and a buck regulator circuit which receives the first DC output voltage from the forward converter circuit. In response to a second control signal, the buck regulator generates a second DC output voltage at a second level.

Control algorithms and circuit designs for optimal flyback-charging of an energy-storage capacitor (e.g., for flash lamp or defibrillator)

Abstract: A flyback-type of a transformer-coupled DC/DC power converter supplies a train of current pulses to charge an energy-storage capacitor to a desired high voltage, converting input DC power obtained from a lower voltage DC source. The energy-storage capacitor is charged to a specified voltage within a specified time with minimum peak and RMS currents in the transistor, the rectifier diode, the transformer windings and the DC power source, minimizing the i/sup 2/R losses. This is done by generating: (1) energy-storage current pulses in the power transistor and the transformer primary winding in which the current increment from the beginning to the end of a pulse is only a small fraction of the final (peak) value; and (2) energy-delivery flyback current pulses in the capacitor and the transformer secondary winding in which the current decrement from the beginning to the end of a pulse is only a small fraction of the initial (peak) value. Recommended methods are: (1) hysteretic current-mode control with current sensing in both transformer windings; (2) peak-current-commanding current-mode control with switching frequency or transistor-nonconducting time varying in a prescribed way during the charging; or (3) valley-current-commanding current-mode control with switching frequency or transistor-conducting time varying in a prescribed way during the charging. Compared with one nonoptimal method, peak currents are reduced by a factor of about 2 and i/sup 2/R power losses are reduced by a factor of about 1.33.

Low cost high efficiency power converter

Abstract: A switch mode power converter achieving high efficiency through zero voltage switching (ZVS) by using an auxiliary switch, a capacitor, an auxiliary winding and an inductor. The technique can be applied to a boost, buck-boost, buck, isolated forward or isolated flyback converter. The auxiliary switch is turned on before the main power switch turns on, and the capacitor provides voltage to energize the inductor and force current to flow into the auxiliary winding. The current is transformed by the main winding and discharges the capacitance across main power switch to zero volts before the main switch turns on. Hence ZVS is obtained and can greatly reduce the switching loss of the main power switch.

Re-lift circuit: a new DC-DC step-up (BOOST) converter

Abstract: A re-lift circuit, which is a new DC-DC step-up (boost) converter, is proposed. This converter performs positive to positive DC-DC voltage increasing conversion with high output voltage.

Simulation and modeling of a DC-DC converter controlled by an 8-bit microcontroller

Abstract: Traditionally, analog control technologies have been employed to regulate the output voltage of DC-DC converters. The utilization of digital control techniques for this regulation function is currently under consideration. Critical issues in a digital control implementation include analog-to-digital conversion range, resolution and delay, calculation time, and numerical precision. Results from an investigation into the modeling and simulation of DC-DC converters controlled by an 8-bit microcontroller are described in this paper. Many of these critical issues have been modeled using Matlab/sup TM/ and Simulink/sup TM/ from The Mathworks Inc. Simulation results from this model are compared to experimental waveforms obtained from a buck converter controlled by a Microchip PIC16C74 8-bit microcontroller. Experimental results agree well with the simulation model. The buck converter is represented by its state-space averaged model in the simulation.

Soft switched PWM AC to DC converter with gate array logic control

Abstract: A soft switched PWM AC to DC power converter for a DC power supply is disclosed. The power supply includes a power factor corrector (PFC) converter with a power boost topology, a DC/DC converter with a forward topology and a fly-back converter which serves as an auxiliary power supply for the controller components. The three converters are synchronized by a gate array logic (GAL) IC to minimize EMI noise. The GAL also conditions the PWM for the PFC and the DC/DC converter to provide very precise switching control. Synchronizing and PWM timing signals are derived by the GAL using a high-speed clock signal that is input to the GAL as a data input. The clock signal is repeatedly divided using synchronous division to yield a digital monostable timing signal that enables very precise control of converter switches.

A new topology for single phase UPS systems

Abstract: This paper presents a new converter topology, based on a single switch AC/DC or DC/DC boost converter combined with a half bridge inverter, suitable for on-line single phase UPS systems. The converter uses only four active switches, including the one for maintaining the charge of storage battery, to realize very desirable features. These include sinusoidal input currents, a common neutral connection-eliminating the requirement of an isolation transformer, low voltage storage battery as well as its charge/discharge regulations. Further, higher AC-DC conversion efficiency can be obtained due to reduced voltage stresses on the switch in the boost converter during normal operation, compared with conventional half bridge converters. Detailed simulation results and experimental results are included in this paper.

A DC-DC converter for short-channel CMOS technologies

Abstract: An integrated DC-DC converter with two passive external components was designed and fabricated in an advanced, short-channel (L/sub eff/ 10 MHz) were used to minimize the size of external components, and novel circuits were used to reduce the stress on the short channel devices. Measured efficiencies for a 3.3 V to 1.65 V converter were approximately 75% for output currents from 15 to 40 mA.

System with open-loop DC-DC converter stage

Abstract: Innovative systems and methods for advantageous use of a new isolated power converter topology, in which transformer isolation is provided by a very simple DC-DC converter operated in open-loop mode (with each switch running at a constant duty cycle of approximately 50%, to achieve an effective duty cycle of approximately 100%), and feedback or modulation is instead applied to a preconverter stage which also does power factor corrections. Since the isolation stage is operated at a constant duty cycle, distortion can be minimized and its efficiency can be fully optimized, with a simple circuit and small component count. Unlike a flyback converter, only a very small inductance is required. A simple control architecture is used with current control loop. The disclosed circuit tightly clamps the voltages on the switch and on the transformer, with no ringing nor overshoot.

Power converter stabilization loop

Abstract: The invention provides a stabilized power converter having an input voltage and an output voltage, where the stabilized converter operates similar to a conventional converter under normal conditions, and operates continuously at the maximum power transfer point during overload conditions. The stabilized converter comprises a voltage control loop for regulating output voltage, and a stabilization loop for regulating input voltage. In a preferred embodiment, the stabilization loop senses the input voltage to the stabilized converter and compares it to a reference voltage. Whenever converter input voltage is above the maximum power transfer voltage, no action is taken by the stabilization loop, and the converter operates in the conventional manner. As converter input voltage approaches the maximum power transfer voltage, converter output voltage and corresponding converter input and output power are reduced to compensate.

Current-source resonant converter in power factor correction

Abstract: A 3 kW AC/DC converter is studied to comply the following conditions: power factor correction, output voltage regulation, electrical insulation, high efficiency. In this study we are interested in current-source resonant converter topologies with two energy storage elements and electrical insulation which allow the leakage inductance of a transformer to be included in order to achieve smaller size and lighter weight.

Frequency-controlled series-resonant converter with synchronous rectifier

Abstract: This paper presents an analysis and experimental results for a frequency-controlled series-resonant dc-dc converter that consists of a Class-D zero-voltage-switching (ZVS) series-resonant inverter and a center-tapped synchronous rectifier. If the dc output voltage is low, the efficiency of the converter is dominated by the efficiency of the rectifier. Low on-resistance metal-oxide-semiconductor field-effect transistors (MOSFETs) are used in the rectifier instead of diodes because the forward voltage drop across the rectifying device is low, resulting in a high efficiency. The dc output voltage is regulated against variations in the load resistance and the dc input voltage by varying the operating frequency. Experimental results are presented for a converter with a dc input voltage of 150 V, an output voltage of 5 V, and a dc load resistance ranging from 0.5 to 5.5 R. The measured efficiency was 86% for a 50 W output and 89% for a 25 W output. The theoretical results were in good agreement with the measured results.

Pulse width modulated DC/DC converters

Abstract: Part I: The fundamentals: Capacitor, inductor, and transformer. Topology_basics of DC/DC converters. Passive filter and frequency content of waveforms. Part II: Forward converter: Steady-state duty cycle equation. Output voltage regulation. Small signal stability analysis. Series-pass regulator. Time-domain studies and filter design. High stress parts and power dissipation. Part III: Flyback converter and boost converters: Flyback converter in discontinuous conduction mode. Boost converter in continuous conduction mode. Part IV: Current-mode and simulation: current-mode control. Simulation of PWM forward converter. Simulation of flyback converter with current-mode control. Appendix. References. Index.

Active snubber for buck-based converters and method of operation thereof

Abstract: For use with a buck-based converter having an isolation transformer, a snubber circuit and a method of damping a transient in the power rectifying diode due to its reverse recovery. In one embodiment, the snubber circuit includes: (1) a capacitor, coupled to a power rectifying diode in the buck-based converter, that receives energy from the power rectifying diode during a reverse recovery period thereof and (2) a flyback converter, coupled to the capacitor, that receives the energy from the capacitor and delivers the energy to a voltage source on the primary side of the isolation transformer.