Showing papers on "Flyback converter published in 1989"

Switchmode Power Supply Handbook

Abstract: Part 1: Functions and Requirements Common to Most Direct Off-Line Switchmode Power Supplies Chapter 1. Common Requirements: An Overview Chapter 2. AC Powerline Surge Protection Chapter 3. Electromagnetic Interference (EMI) in Switchmode Power Supplies Chapter 4. Faraday Screens Chapter 5. Fuse Selection Chapter 6. Line Rectification and Capacitor Input Filters for "Direct Off-Line" Switchmode Power Supplies Chapter 7. Inrush Control Chapter 8. Start-Up Methods Chapter 9. Soft Start and Low-Voltage Inhibit Chapter 10. Turn-On Voltage Overshoot Prevention Chapter 11. Overvoltage Protection Chapter 12. Undervoltage Protection Chapter 13. Overload Protection Chapter 14. Foldback (Reentrant) Output Current Limiting Chapter 15. Base Drive Requirements for High-Voltage Bipolar Transistors Chapter 16. Proportional Drive Circuits for Bipolar Transistors Chapter 17. Antisaturation Techniques for High-Voltage Transistors Chapter 18. Snubber Networks Chapter 19. Cross Conduction Chapter 20. Output Filters Chapter 21. Power Failure Warning Circuits Chapter 22. Centering (Adjustment to Center) of Auxiliary Output Voltages on Multiple-Output Converters Chapter 23. Auxiliary Supply Systems Chapter 24. Parallel Operation of Voltage: Stabilized Power Supplies Part 2: Design: Theory and Practice Chapter 1. Multiple-Output Flyback Switchmode Power Supplies Chapter 2. Flyback Transformer Design Chapter 3. Reducing Transistor Switching Stress Chapter 4. Selecting Power Components for Flyback Converters Chapter 5. The Diagonal Half-Bridge Flyback Converter Chapter 6. Self-Oscillating Direct-Off-Line Flyback Converters Chapter 7. Applying Current-Mode Control to Flyback Converters Chapter 8. Direct-Off-Line Single-Ended Forward Converters Chapter 9. Transformer Design for Forward Converters Chapter 10. Diagonal Half-Bridge Forward Converters Chapter 11. Transformer Design for Diagonal Half-Bridge Forward Converters Chapter 12. Half-Bridge Push-Pull Duty-Ratio-Controlled Converters Chapter 13. Bridge Converters Chapter 14. Low-Powered Self-Oscillating Auxiliary Converters Chapter 15. Single-Transformer Two-Transistor Self-Oscillating Converters Chapter 16. Two-Transformer Self-Oscillating Converters Chapter 17. The DC-to-DC Transformer Concept Chapter 18. Multiple-Output Compound Regulating Systems Chapter 19. Duty-Ratio-Controlled Push-Pull Converters Chapter 20. DC-to-DC Switching Regulators Chapter 21. High-Frequency Saturable Reactor Power Regulator (Magnetic Duty Ratio Control) Chapter 22. Constant-Current Power Supplies Chapter 23. Variable Linear Power Supplies Chapter 24. Switchmode Variable Power Supplies Chapter 25. Switchmode Variable Power Supply Transformer Design Part 3: Applied Design Chapter 1. Inductors and Chokes in Switchmode Supplies Chapter 2. High-Current Chokes Using Iron Powder Cores Chapter 3. Choke Design Using Iron Powder Toroidal Cores Chapter 4. Switchmode Transformer Design (General Principles) Chapter 5. Optimum 150-W Transformer Design Example Using Nomograms Chapter 6. Transformer Staircase Saturation Chapter 7. Flux Doubling Chapter 8. Stability and Control-Loop Compensation in SMPS Chapter 9. The Right-Half-Plane Zero Chapter 10. Current-Mode Control Chapter 11. Optocouplers Chapter 12. Ripple Current Ratings for Electrolytic Capacitors Chapter 13. Noninductive Current Shunts Chapter 14. Current Transformers Chapter 15. Current Probes for Measurement Purposes Chapter 16. Thermal Management Part 4: Supplementary Chapter 1. Active Power Factor Correction Chapter 2. The Merits and Limitations of Hard Switching and Fully Resonant Switchmode Power Supplies Chapter 3. Quasi-Resonant Switching Converters Chapter 4. A Fully Resonant Self-Oscillating Current Fed FET Type Sine Wave Inverter Chapter 5. A Single Control Wide Range Sine Wave Oscillator Glossary References Index

Power conversion apparatus for DC/DC conversion using dual active bridges

Abstract: A DC/DC power converter suitable for high power applications has an input converter which converts the DC input voltage to an AC voltage and supplies this voltage to a transformer. The output of the transformer is provided to an output converter which converts the AC to a DC output voltage at a controlled level to a load. Both the input and output converters are composed of active gate controlled switching devices and are switched in a soft-switched manner to minimize switching losses and increase switching frequency. The converters can be implemented in single phase or polyphase configurations and can be controlled to closely maintain the output voltage provided to the load at a desired level.

Design of feedback loop in unity power factor AC to DC converter

Abstract: In certain applications it is desirable to convert the utility AC voltage to a DC voltage in such a way as to present a unity power factor load A common means of doing this is a circuit consisting of a bridge rectifier followed by a boost converter Various control schemes for this boost converter are discussed, including their tradeoffs as to power factor, output voltage transient regulation, and cost of implementation A nonlinear regulation-band circuit that has a favorable combination of properties is presented >

Resonant DC/DC converter with class-E inverter and class-E rectifier

Abstract: A new type of high-frequency high-efficiency resonant DC/DC converter is proposed, analyzed, and verified experimentally. It is called a class-E converter because it consists of a class-E inverter and a class-E rectifier. The class-E rectifier acts as an impedance inverter and is compatible with the class-E inverter. Consequently, the converter can operate with load resistances from a full load to infinity while maintaining zero-voltage switching of the transistor in the inverter and the diode in the rectifier. It operates safely with a short circuit at the output. Because of a high value of the load quality factor Q/sub 1/, a narrow frequency range suffices to regulate the DC output voltage over the whole load range. The measured relative bandwidth was delta f/f/sub min/=42.2% as the load resistance was varied from 70 Omega to open circuit. The measured efficiency at the full load was 89% with a 9 W output power at 1 MHz. A family of class-E/sup 2/ resonant DC/DC power converters is given. The possibility of reduction of class-E/sup 2/ converters to lower-order resonant and pulse-width-modulation converters is shown. >

Dc/dc converter switching at zero voltage

Abstract: A two switch, DC/DC converter provides sufficient inductive energy storage at the termination of the "on" period of each switch to alter the charge on the intrinsic and stray capacitance of the combination of switches producing zero voltage across the alternate switch prior to its turn on. A short dead-band between the turn on pulses provided by the control circuit allows time for this transition. Thus the energy stored in the capacitance of the switches is returned to the source and load rather than being dissipated in the switching devices. This greatly improves the efficiency of the converter particularly when operating at high frequency. The unique topology of the converter provides other new and useful characteristics in addition to zero voltage switching capability such as operation as constant frequency with pulse-width-modulation for regulation, quasi-square wave output current, and the ability to integrate the magnetic elements with or without coupling.

Fluorescent lamp controllers

Abstract: An electronic controller for fluorescent lamps includes a DC to AC converter which supplies high frequency current to the lamps and a preconditioner stage which includes a switched mode power supply connected to accept line power and produce a DC input for the DC to AC converter. The switched mode power supply and the DC to AC converter are synchronized to operate in a fixed phase relationship and/or at the same frequency.

Dual sepic PWM switching-mode DC/DC power converter

Abstract: A steady-state analysis and experimental results for a dual sepic pulse-width-modulated (PWM) DC/DC power converter for both continuous and discontinuous modes of operation are presented. The converter is dual to a sepic converter, but it can also be derived from a forward converter by replacing one of its rectifier diodes with a coupling capacitor. The circuit acts as a step-down or step-up converter, depending on the value of the ON switch duty cycle. The transformerless version of the converter has a positive DC/DC voltage transfer function. Therefore, the circuit is suitable for distributed power systems. Design equations for all circuit components are derived. Experimental results measured at 100 kHz were in good agreement with theoretical predictions. >

Strobed DC-DC converter with current regulation

Abstract: A DC-DC converter regulates the maximum current through an inductor. The DC-DC converter operates within a paging receiver and boosts a voltage from a single cell battery to substantially 3.1 VDC in order to operate circuits which require more voltage than that produced by the single cell battery. Such circuits include CMOS microcomputers and code plug. The DC-DC converter is current regulated thus providing for improved power conversion efficiency. The DC-DC converter is active when the voltage is below a minimum voltage and inactive when above a maximum voltage. The DC-DC converter provides for a wide range of load currents from the converted voltage without being controlled by a microcomputer and while delivering the power to the loads with an improved efficiency.

Push pull resonant flyback switchmode power supply converter

Abstract: A flyback converter high voltage power supply which includes two switches (Q10, Q11) operating in push pull fashion to provide alternate polarity energy pulses to a load (30). A main component of the power supply is a transformer (T10), the primary winding of which is divided into halves (P1, P2). The secondary may also be split into halves (S1, S2), or may be configured without a split so long as the secondary and rectifier combination result in full wave rectification. The first of the two switches (Q10) couples an input voltage (Vin) across the first primary half (P1) to store energy in the magnetic core during a first time interval, and at the end of the first time interval disconnects the first primary half (P1) from the input voltage (Vin). During a second time interval, the energy stored in the magnetic core during the first time interval is delivered to the load (30) via the secondary winding (S1, S2). The second of the two switches (Q11) similarly couples the input voltage (Vin) across the second primary half (P2) to store energy in the magnetic core during a third time interval, and then disconnects the second primary half (P2) from the input voltage (Vin) at the beginning of the fourth time interval. During the fourth time intevral, the energy stored in the magnetic core is again transferred to the load (30) via the secondary. A duty factor modulator is used to control the switching of the first and second switches (Q10, Q11) to vary the length of the time intervals in reponse to variations in the load and input voltage.

Current mode controlled bidirectional flyback converter

Abstract: A description is given of a current-mode-controlled bidirectional flyback converter handling different values of power in either direction. The flyback transformer operates in a continuous conduction mode in one direction and in a discontinuous conduction mode in the other direction of power flow. Signal flow graph modeling, analysis, and design of such a scheme are presented. Experimental results are included. >

Class E DC/DC converters with an inductive impedance inverter

Abstract: The analysis, design equations, and experimental verification are presented for a class E DC/DC switching-mode high-efficiency resonant DC/DC converter with a transformer center-tapped rectifier. The analysis is performed at a constant current through the DC-feed choke and using the high Q/sub 1/ assumption (Q/sub 1/>or=5). The converter can operate under safe conditions for load resistances ranging from a full load to an open circuit. This feature has been obtained by using an inductive impedance inverter. The results of the analysis are then generalized for the entire family of class E DC/DC converters. Experimental results show good agreement with the theoretical predictions. The measured total efficiency was 89% at 1 MHz with 15 W output power. A narrowband FM regulation ( delta f/f=12%) of the DC output voltage was achieved as the load was varied from a minimum resistance (full load) to an open circuit. >

Fluorescent dimming ballast utilizing a resonant sine wave power converter

Abstract: In a method or combination, a DC voltage supply, a converter including a series or a parallel resonant circuit (LR, CR, TR) for converting the DC voltage to a sinusoidal current, and a load (T1, T2) including at least one fluorescent lamp responsive to the sinusoidal current to effect excitation of the lamp.

Pulse width modulation power transmission system

Abstract: A converter for interconnecting two electric networks to transmit electric power from one network to the other, each network being coupled to a respective power generator station. The converter, having an AC side and a DC side, includes a bridge of semiconductor switches with gate turn-off capability coupled to a control system to produce a bridge voltage waveform having a fundamental Fourier component at the frequency of the electric network coupled to the AC side of the converter. The control system includes three inputs for receiving reference signals allowing to control the frequency, the amplitude and the phase angle of the fundamental Fourier component with respect to the alternating voltage of the network coupled to the AC side of the converter. Through appropriate feedback loops, the converter may be used to maintain at a predetermined level the power flowing therethrough or to keep at a preset value the voltage across the DC terminals of the converter and, in both cases, to maintain the frequency synchronism between the fundamental Fourier component and the alternating voltage of the network coupled to the DC side of the converter.

Performance of low loss synchronous rectifiers in a series-parallel resonant DC-DC converter

Abstract: The functionality of efficient synchronous rectifier components, specially developed for resonant DC-DC converter topologies designed to operate at high frequency, has been demonstrated in a series-parallel converter circuit operating at 420 kHz and 85 W Conduction losses for these components are three times lower than for Schottky diodes Switching conditions for efficient operation have been identified both experimentally and using accurate multilevel modeling >

Dual switched mode power converter

Abstract: A dual power converter is introduced which addresses the problem of output ripple and switching losses in a switched power converter. One stage of the power converter is a conventional PWM (pulse-width modulated) converter, and the other stage is a linear source. The linear source controls the voltage directly, and the output current of the linear stage is used to generate the control signal for the switching stage. This scheme is modeled as a two-stage control system, and the overall response is obtained in terms of the individual transfer functions. The PWM converter supplies most of the current, while the linear source supplies the reverse of the ripple current. Two DC-to-DC buck converters have been designed and implemented, giving excellent ripple suppression and high efficiency at very low switching frequencies. >

AC/DC converter using resonant network for high input power factor

Abstract: An AC/DC converter is provided, suitable for use in an advanced single phase, sine wave voltage, high frequency power distribution system, such as that used on a 20 kHz Space Station Primary Electrical Power Distribution System. The converter comprises a transformer, a resonant network, a current controler, a diode rectifier and an output filter. The voltage source is converted into a sinusoidal current source. The output of this current source is rectified by the diode rectifier and is controlled by the current controller. The controlled rectified current is then filtered by the output filter to obtain a constant voltage across the load.

Regulated flyback converter with spike suppressing coupled inductors

Abstract: Flyback converters can generate multiple voltage levels by rectifying and filtering multiple windings on a single power transformer. Different voltages should be related by the turns ratio of the respective windings. Transformer leakage inductance causes leading edge voltage spikes on some windings causing the filters to peak charge to a higher value than expected. The addition of a small coupled inductor between two or more windings will block the leading edge spike allowing the filter to charge to the correct voltage. The turns ratio of the coupled inductor is selected to cancel the leading edge voltage spike on the desired winding. The coupled inductor can be used to correct the voltage of a winding used for feedback purposes as well as improving the cross regulation between multiple converter outputs.

Evaluation and design of megahertz-frequency off-line zero-current-switched quasi-resonant converters

Abstract: A performance comparison of flyback, forward, and half-bridge zero-current-switched quasi-resonant converter topologies for high-frequency offline applications is presented. It is shown that the half-bridge topology with secondary side resonance operating in half-wave mode is most suitable. A complete design procedure for the half-bridge power stage and the voltage-feedback control is presented together with experimental results for a 300 V DC hybridized converter which operates with conversion frequencies from 400 kHz to 2 MHz and delivers 1.5-16 A at 5 V DC. >

Current limited quasi-resonant voltage converting power supply

Abstract: A voltage converting power supply having current limiting characteristics wherein a flyback converter is operated in a load dependent half-wave mode. Constant pulse width switching at a variable rate is utilized for regulation and, by setting the maximum switching frequency, current limiting is achieved.

Power source for emergency lighting systems

Abstract: A buck/boost converter is driven by a high frequency dc-to-dc flyback converter to provide substantially constant output power, independent of the output voltage, to an inductor to provide current to a load having a v-i characteristic that is suitable for use with a current power source, such as a plurality of parallely-connected LEDs. The flyback converter repetitively generates a battery-simulated output voltage that is current-limited and which may be used to charge a battery as well as to provide power to the buck/boost converter. The buck/boost converter includes a switching circuit for repetitively transferring current to the load and a current sensor circuit operating in conjunction with the switching circuit to change the state of the buck/boost converter to repetitively open the switching means and initiate release of the current to the load.

AC/DC conversion with reduced supply waveform distortion

Abstract: Method and apparatus for performing AC/DC conversion to provide a regulated DC output with reduced distortion of the AC supply waveform. An AC supply is filtered and rectified to provide a DC signal. A plurality of flyback circuits, each having a series connection of a switch and a first winding which is connected in parallel to the rectifier circuit, as well as a second winding which is inductively related to the first winding, are provided. The second winding from each flyback circuit is connected in parallel through ORing diodes to form an output. The switches in each flyback circuit are repeatedly enabled and disabled in sequence. The first winding in each flyback circuit is energized from the DC signal when the respective series switch is enabled. When the switch is disabled, the inductively related second winding is energized. The combined output from each of the second windings provides a regulated DC signal.

DC/DC converter with class E zero-voltage-switching inverter and class E zero-current-switching rectifier

Abstract: A class-E resonant DC/DC power converter is introduced and verified experimentally. It is composed of a class-E zero-voltage-switching inverter and a class-E zero-current-switching rectifier. Therefore, it offers high efficiency at high frequencies. The measured DC/DC efficiency was 82.64% at full load with 7.3-W output power. A relative frequency range of only 6.12% was sufficient to regulate the DC output voltage at 20 V for load resistances ranging from 55 Omega to infinity. >

Universal fluorescent lamp ballast

Abstract: A ballast having a converter for converting input power into DC at a high frequency and a commutator for converting the DC to AC at a low frequency to cause light emission from a gas discharge lamp The converter also contains a transformer for converting the input AC to a low voltage AC for heating the filaments in the lamp Current and Voltage sensors associated with the commutator provide feedback to control circuitry which allows power conversion after the filaments heat and the voltage to the lamp to increase to the voltage required to start the lamp even when different starting voltage requirement lamps are used After the lamp starts, the lamp is soley current mode controlled By frequency modulation of the commutator, both power and crest factor can be controlled

Switched-mode power supply circuit

Abstract: A switched-mode power supply circuit having a transformer and a first controllable switch on the primary side of the transformer. A first section is in the form of a flyback d.c. converter including a first secondary winding of the transformer for generating a first d.c. output voltage which is stabilized, by a control, against d.c. input voltage variations of the circuit and of a first load. A second section including a second secondary winding of the transformer constitutes a forward d.c. converter having a second controllable switch for generating a second d.c. output voltage. The ratio between the period of conductance of the second switch and the period of the control signal of the first switch is independent of the frequency of this signal.

High-frequency high-order parallel resonant converter

Abstract: A novel approach to the analysis of design of a high-order high-frequency LCC-type capacitive coupled parallel resonant converter (PRC-LCC) operated in the continuous-conduction mode is presented. The presence of an additional capacitor in series with the inductance of the conventional PRC results in a converter with more desirable control characteristics. It is shown that, at switching frequencies lower than the resonant frequency, the gain of the LCC-type converter is lower than the grain of the conventional PRC. This facilitates the converter design with a lower turn-ratio transformer and therefore allows for a higher operating frequency. The complete state-plane diagram of the LCC-type converter, from which a set of steady-state characteristic curves is plotted, is given. Various design curves for component value selections and device ratings are given. A design example with computer simulation results is presented. >

Synchronization circuit for a resonant flyback high voltage supply

Abstract: A synchronization circuit for a resonant flyback high voltage supply for use in providing a high voltage output for a CRT. The circuit includes driving circuitry including an input power filter providing power to a coupled inductor which transmits power to a four stage multiplier circuit. Power is switched on and off by a power FET. The synchronization circuit reduces power loss in the FET by using variations in operational frequency to meet varying loads. By reducing the frequency as load increases, the flyback waveform is allowed to complete its resonant cycle before turning on the power FET. An anode resonant flyback regulator including a pulse width modulator controls the FET in response to signals provided by a negative slope detector circuit and feedback voltage. Over current shutdown capability is further provided by a current sensing latch.

Unity power factor AC/DC converter

Abstract: A control for an AC/DC power converter having first and second switches and which converts an AC voltage supplied by an AC source into a DC voltage on a DC output conductor includes circuitry for developing an error signal representing the deviation of the DC voltage from a desired level and a multiplier coupled to the developing circuitry and responsive to the AC voltage for deriving a reference signal representing a desired current magnitude from the AC source. A current sensor develops a current magnitude signal representing the magnitude of the current from the AC source and a circuitry having a hysteresis characteristic compares the current magnitude signal with the reference signal to obtain a comparison signal. Buffer and interface circuits operable the first and second switches in accordance with the comparison signal to in turn cause the DC voltage to approach the desired level and to cause the current from the AC power source to have a certain phase relationship with respect to the AC voltage supplied thereby.

Constant-frequency, zero-voltage-switched, clamped-mode parallel-resonant converter

Abstract: The DC behavior of a constant-frequency, clamped-mode parallel-resonant converter operating above resonant frequency is characterized. The converter is shown to be able to operate with zero-voltage turn-on for all the switches from no load to full load over a wide input range. Various circuit operating modes are identified and their corresponding operating regions defined. DC characteristics for the converter design are derived. A 5 V, 50 W prototype converter operating at 104 kHz is breadboarded to show the feasibility of constant-frequency, zero-voltage-switching operation and to substantiate the analytical results. The converter is operated with zero-voltage switching from no load to full load over the entire input voltage range without any external antiparallel diodes and snubbers. The experimental results are in good agreement with the analytical predictions. An efficiency of 85% is achieved. >

A novel unipolar converter for switched reluctance motor

Abstract: A configuration of a unipolar power converter with improved switching performance suitable for switched-reluctance motor supply is presented. The switched-reluctance motor operation principle is presented and its ideal characteristics are considered. The proposed converter is described and its operation is analyzed. The converter characteristics are studied with the aid of computer simulation. Current control of the proposed converter is considered. A prototype converter has been built to verify the analysis results and to validate the simulation. The design procedure is presented and experimental results which confirm the analysis are given and discussed. >

Mode analysis of half-bridge zero-voltage-switched multi-resonant converter

Abstract: A complete DC analysis of the half-bridge zero-voltage-switched multiresonant converter is presented. The analysis reveals four different modes of operation. The existence of the modes has been verified experimentally. A computer algorithm is developed for calculating the complete DC voltage-conversion-ratio characteristics encompassing all four modes of operation. The DC characteristics enable the design of the converter to be optimized. The optimization is performed by selecting the resonant components and the turns ratio of the transformer. The computer algorithm can be easily adapted for the analysis of the small-signal properties of the half-bridge multiresonant converter. >