Showing papers on "Flyback converter published in 1986"

Bi-directional buck/boost DC/DC converter

Abstract: A bi-directonal DC/DC converter includes a first power switch coupled to a first input/output of the converter, an energy storage element coupled to the first power switch, a second power switch coupled between the energy storage element and a second input/output of the converter and means for controlling the first and second power switches so that one of the power switches is opened while the other power switch is alternately opened and closed to transfer power from one input/output to the other input/output.

Boost/buck DC/DC converter

Abstract: A bi-directional DC/DC converter includes a first switch coupled to a first input/output of the converter, a first input/output energy storage element coupled to the first input/output of the converter, a second input/output energy storage element coupled to a second input/output of the converter, an intermediate energy storage element coupled between the second input/output and the first switch and a second switch coupled to the intermediate energy storage element and to the first switch. A pulse width modulator operates the first switch between on and off states while the second switch is maintained in an off state to operate the converter as a buck converter, during which time the power is transferrred from the first input/output to the second input/output. A further pulse width modulator operates the second switch between on and off states while the first switch is maintained in the off state to operate the converter as a boost converter, during which time power is transferred from the second input/output to the first input/output.

A Three-Phase Off-Line Switching Power Supply with Unity Power Factor and Low TIF

Abstract: A new three-phase off-line switching AC/DC converter is described, one which draws essentially sinusoidal AC currents from the input line and therefore generates a very low TIF (Telephone Influence Factor) in the three-phase line currents. The converter consists of three two-stage power processors, the first stage of each performing the unity power factor conversion and the second stage providing isolation and combining the power to a single DC output. The converter easily can be reconfigured to operate from either a single-phase or three-phase (wye or delta) input line. In addition to providing the benefits of unity power factor operation (i.e., good power utilization of source volt-ampere capacity, negligible harmonic currents and low TIF), the converter can operate from a wide range of input voltages because it minimizes voltage stresses to which power switches are exposed. The power stages and control circuits used in a 2 KW implementation of the converter are described and modeled. Some measurements demonstrating the operation of the converter are presented.

Current fed regulated voltage supply

Abstract: The invention is a locally isolated regulated power supply providing a regulated dc power output from an ac current source having a large dynamic range. The power supply comprises an ac-to-dc converter for providing a rectified dc output from an ac current input. The converter includes a current transformer in combination with a rectifier. The current transformer has a saturable magnetic core for receiving primary and secondary windings. The current transfomer produces a reduced secondary output voltage that is a function of the ac system current characterized by the decreased coupling between the core and secondary winding as the core approaches saturation during substantial increases in the ac system current. One or more secondary windings and associated circuitry can be provided. In addition, an electronically controlled switch or shunt having as inputs a predetermined reference voltage and the dc output voltage of the rectifier or a signal equivalent thereto is connected across the converter. The switch provides for the continual shunting of the converter whenever the dc output voltage is equal to or greater than the predetermined reference voltage. A voltage support capacitor is connected across the output of the converter for maintaining the output voltage proportional to the selected reference voltage. An isolation diode is used to isolate the voltage support capacitor from the converter during those periods of time when the converter is being shunted by the electronically controlled switch. This prevents the discharge of the capacitor.

High voltage power supply system including inverter controller

Abstract: A high voltage power supply system includes a DC-to-DC converter for producing a DC low voltage, a DC-to-AC inverter connected to a step-up transformer for producing an AC high voltage by transforming an AC low voltage obtained from the DC low voltage, and an inverter controller for controlling an operation time period of the DC-to-AC inverter longer than that of the DC-to-DC converter. Since a residual charge stored in a capacitor of the DC-to-DC converter is rapidly discharged by lengthening the operation time period of the DC-to-AC inverter, an unwanted AC high voltage is induced at a secondary winding of the step-up transformer.

Portable tester and related method for determining the primary winding to secondary winding current ratio of an in-service current transformer.

Abstract: A portable tester for determining the primary winding (18) to secondary winding (22) current ratio of a current transformer (16) while that transformer is in service, including a current probe (40) having a split core positionable around an active power line (14) supplying current to the transformer, an AC to DC converter (44) to convert the AC output of that probe to a first DC signal, another AC to DC converter (56) for converting the secondary output of the current transformer under test to a second DC signal, and a ratio meter (46) for converting the first and second DC signals into a visual display of the ratio of those signals. A mechanism (42) is provided for assuring proper location of the decimal point on the ratio meter. Polarity and burden testing is also provided.

Power circuit with high input power factor and a regulated output

Abstract: A single power converter is capable of drawing low distortion current from an AC line and delivering DC or AC power to a load. The single power converter is used to independently control the input current and the output current. The power converter transformer has an output winding which is controlled by pulse-width modulation (PWM) and a frequency controlled boost winding for controlling input current.

Power failure stop circuit for a converter

Abstract: The voltage in a converter 20 is compared with a reference voltage to detect an input power failure, in response to which a motor driven by the converter is automatically decelerated in accordance with a stored signal pattern/speed reduction curve such that the energy regenerated by the motor is equal to its power consumption. The DC bus voltage of the converter is thus maintained substantially constant during the regenerative braking of the motor, and it is promptly halted without resort to any mechanical braking unit.

Power supply operable on varying inputs

Abstract: A power supply provides the stable DC voltages needed for a computer terminal from a wide range of line voltages and frequencies. The line is rectified and fed to a flyback transformer wherein primary current is controlled in duration for providing the desired energy transfer to the secondary winding. The outputs from the flyback transformer are rectified and filtered. A separate start-up circuit uses a transformer across the line voltage, and a positive coefficient resistor provides a time limit to allow the use of a small transformer even though the line voltage may be high. The start-up circuit must produce a minimum voltage for the switching transistor in the flyback arrangement to allow operation of the power supply, and the start-up transformer is disconnected from the circuit after operation to prevent electromagnetic interference within the terminal. The output from the power supply is used in the control of the switching transistor so that, once the start-up circuit has achieved the needed voltage level, the power supply can assist in maintaining the operation.

Clocked direct voltage converter

Abstract: A clocked direct voltage converter with potential separation includes a control circuit for controlling the switching times of a switching transistor arranged on the primary side of the voltage converter, in which voltage converter voltage proportional to an output quantity is chopped by a controllable switch. The chopped voltage is transmitted by a transformer to the primary side of the converter, is then rectified, filtered and supplied to the control circuit. In order to obtain the largest possible control range for the converter, a further transformer is provided which transmits oscillation signal of an oscillator of the control circuit to the controllable switch on the secondary side voltage converter. By means of this oscillation signal, the controllable switch is controlled.

Low dissipation capacitor voltage sharing circuit for a static AC/DC converter

Abstract: In an AC/DC converter, the dissipation voltage sharing resistors commonly placed in parallel with the series capacitors are replaced by a resistor balancing path derived from the capacitor junction point to a symmetrically disposed voltage reference point belonging to the AC input vectorial system.

Filter capacitor discharge circuit for a DC-DC converter

Abstract: A power supply circuit includes a battery power source connected by a switch to the input of a DC to DC converter. The output of the DC to DC converter is connected to a filter capacitor and a load. A crow-bar is connected to the input and the output of the DC to DC converter. The crow-bar shorts the output to ground to discharge the capacitor when the voltage at the input drops to a predetermined value.

High voltage resonant DC/DC converter

Abstract: A high voltage DC/DC converter including a voltage resonance switching circuit formed by a coreless transformer, a GTO thyristor switching element connected between the primary winding of the transformer and a D.C. source, and a voltage resonance capacitor connected in parallel to the switching element. A rectifier circuit is connected to the secondary winding of the transformer to rectify an output current from the transformer circuit. The resonance frequency of the parallel resonance circuit made of the resonance capacitor and the coreless transformer is selected to be the frequency of that component of the current supplied to the circuit through the switching element, which has a greater amplitude than any other component of the current (including the fundamental frequency and other harmonic).

Power-factor-corrected AC/DC converter

Abstract: An AC/DC converter comprises a half-bridge electronic self-oscillating inverter powered from the non-filtered full-wave-rectified 120 Volt/60 Hz power line voltage, and its resulting amplitude-modulted 30 kHz output voltage is applied to a series-resonant L-C circuit. The 30 kHz voltage developing across the tank capacitor of this L-C circuit is rectified and applied as DC to an energy-storing capacitor, from which the AC/DC converter's output is supplied. Trigger pulses are provided to trigger the inverter into self-oscillation at the beginning of each pulse of DC voltage provided by the unfiltered rectified power line voltage. As soon as the magnitude of the DC voltage across the energy-storing capacitor exceeds a first level, the trigger pulses cease to be provided. As soon as the magnitude of the DC voltage on the energy-storing capacitor falls below a second level, the trigger pulses are again provided. As long as the inverter is in operation, the current pulled from the power line is essentially of constant magnitude and therefore providing for a power factor of about 90%.

Floating battery feed circuit using multifilar transformer.

Abstract: A substantial reduction in the common-mode noise generated by a switching-mode power converter is achieved by incorporating a multifilar-wound transformer (410) into the converter in such manner that the inter-winding capacitances cause a cancellation of common-mode, noise components at the converter output.

DC/DC converter of the "forward" type with zero-current switching and two-way current operation

Abstract: DC/DC converter comprising a transformer whose primary L1 is coupled to a source +E by a MOS transistor T1. A diode D1 and a second MOS transistor T2 in parallel are connected in series with a capacitor C and the secondary L2. The second MOS transistor T2 is controlled directly by the voltage across the terminals of the capacitor C. This converter, of the "forward" type, switches at zero current whilst being practically able to operate at a constant frequency.

Control method for an extra high voltage d-c transmission connecting two three-phase networks

Abstract: Simultaneous power and voltage control by a d-c-tie between a-c networks is carried out by means of fixed and switchable inductive and capacitive compensation elements including the tap changer of both converter transformers of a d-c-tie for setting the optimum operating point by a transformation ratio of the converter transformer taps matching the primary current ratio, of the converter transformer taps for the maximally permissible stage of the one converter transformer, taking into consideration control, extinction and overlap angles of the d-c-tie.

Dual-slope analog-to-digital converter with voltage to current converter

Abstract: An analog-to-digital converter is provided based on supplying various multiplexed inputs, including analog input signal samples, to a voltage-to-current converter charging and discharging an integrated capacitor. A comparator determines the status of this capacitor to a control counter to provide digital representations.

Flyback transformer circuit with a noise cancelling circuit

Abstract: In a flyback transformer circuit for a cathode-ray tube of the type arranged such that secondary windings of the flyback transformer are isolated from an a.c. power source, a positive terminal of at least one secondary winding of the flyback transformer is connected via a capacitor or a series circuit of a capacitor and a parallel circuit of a resistor and a coil to a terminal which is coupled with the commercial a.c. power source via low impedance in connection with high frequency. With the provision of the capacitor or the series circuit including the capacitor, the potential at the positive terminal of the secondary winding is made equal to that at the commercial a.c. power source in connection with high frequency components, and thus the flyback pulse appearing at the positive terminal of the secondary winding has the same polarity and substantially the same peak value as that appearing at the above-mentioned terminal. As a result noise caused from flyback pulses is effectively prevented from entering the ground line or earth to avoid undesirable phenomena caused from such noise.

Hybrid switching circuit in a DC to DC converter

Abstract: In the preferred and illustrated embodiment of a DC to DC power converter in a sonde and exposed to high temperatures, a transformer with primary and secondary provides AC to a full wave rectifier bridge. The bridge output is DC with ripple on it. The bridge output is connected serially to the primary winding and also to a shunt capacitor. The circuit provides high temperature performance including slower switching speeds, reduced power dissipation and wider current range.

A multiinput type converter for an uninterruptible dc power supply

Abstract: Low-power uninterruptible dc power supplies have been used widely. These are powered by several types of power sources with differing voltages, e.g., commercial ac power sources as well as batteries. A multi-input-type converter is developed to simplify circuit configuration and realize a low-loss power system. This paper presents a method of designing a multiinput transformer as well as the operation principle of a multiinput-type uninterruptible power supply and the circuit technology required for it. The power supply can be realized if the transformer primary winding-turn ratio is designed considering the input voltage variation range and the voltage-drop in the transformer primary circuit. The fact that the switching-duty ratio must be changed drastically and that the switching transistor loss is inclined to increase in a multiinput-type converter causes some problems. It is shown that the application of a collector current proportional drive circuit to the forward-type converter or a base resistor switching circuit to the flyback-type converter is effective in reducing the converter loss and the converter can be simplified by using most of the converter circuits in common.

Television receiver load compensation circuit

Abstract: A deflection circuit is coupled to a horizontal deflection winding for generating scanning current in the winding. A retrace pulse voltage is developed across the deflection winding during the retrace interval. A flyback transformer is coupled to the deflection circuit and has retraced pulse voltages developed across windings thereof. A source of supply energy is coupled to a first winding of the flyback transformer and a load circuit, such as a high power audio circuit, is coupled to a second winding of the transformer and draws load current therefrom. A switched mode power supply is coupled to the source of supply energy and to the flyback transformer for controlling the transfer of energy between the source and the load circuit. A compensation circuit responsive to the operation of the switched mode power supply produces variations in current in an inductance coupled to the flyback transformer. These variations are indicative of variations in load current drawn by the load circuit. The flyback transformer couples the inductance to the retrace resonant circuit for a variable amount of time during retrace to control the transformer trace-retrace duty cycle in a manner that compensates for retrace time modulation due to loading variations.

Dynamic Characterstics of the Push-Pull DC to DC Converter

Abstract: The dynamic characteristics of the push-pull dc to dc converter are analyzed both theoretically and experimentally for the modes of operation which are caused by the interaction between magnetizing current of the transformer and that of the reactor. Among all six modes of operation, four modes are of the first-order system. In two out of the four modes, the instantaneous reactor current does not fall to zero at any point in the switching cycle.

Small-Signal Analysis of a Coupled-Inductor Step-Down Switching DC-DC Converter

Abstract: Small-signal model of an unfamiliar step-down switching dc-dc converter with continuous input and output current is derived. As a result, analytical expression for the control-to-output transmittance having two zeros and four poles is obtained. An interesting feasibility of the effective zero-pole cancelation is shown which leads to the simple second-order frequency response. Applicability of the standlarized control module for optimization of the overall closed-loop frequency characteristics is discussed.

Primary-pulsed switched-mode power supply

Abstract: The invention relates to a primary-pulsed switched-mode power supply having a flyback converter with a primary winding and secondary winding (1, 2). Arranged between the reference point (P) on the primary side and the load side of the flyback converter (1, 2) is a feedback circuit (CK) which feeds back a load-side voltage to the reference potential, in the sense of compensating for the asymmetric interference voltage component.

A Low-Power Constant-Current Converter with HIC Techniques and its Circuit Simplification

Abstract: A low-power constant-current converter that is required to be small and inexpensive, is developed. The most effective means for size and cost reduction is to introduce hybrid IC (HIC) techniques and to mount as large a number of circuit elements as possible on the HIC substrate. Application of a circuit with a simple configuration is important for the HIC techniques. A flyback type converter that has a small number of parts is utilized, and circuit simplification techniques are developed. The driving transformer for isolation between the input and output in the control loop is replaced by a photocoupler, and the power supply for the transformer secondary circuit is improved to miniaturize the converter. A control circuit to compensate for phase-lag in the photocoupler is studied and a simple method is proposed. Both a method for simplifying the circuits and the analysis and design of the phase-compensation circuit for the constant-current converter are described. The converter is miniaturized to 9.2 cm3/W by application of the HIC technique. The size of the converter corresponding to one subscriber can be reduced to 1/5 compared with that of the conventional multi-output converter.

Method and device for controlling the frequency of a starting converter as a function of the frequency of an operating converter

Abstract: The subject-matter of the invention is a method and a device for controlling the frequency of a starting converter (2) during starting at a frequency which is predetermined by an operating converter (1), with phase-correct synchronisation and, during slowing down from a frequency which is predetermined by the operating converter (1), at a lower frequency. The frequency which is supplied to the starting converter (2) is increased during starting and/or is reduced during slowing down in inverse proportion to the frequency of the operating converter (1).

Optimum design of a single-ended flyback converter

Abstract: In this paper, an optimum design method is employed for a single ended flyback converter with four outputs. The mathematical model contains 16 variables and 16 constraints to minimize the weighted sum of the power loss and weight of the converter. The Augmented Lagrangian Multiplier Penalty Function Technique is adopted in forming the CAD program with FORTRAN IV. By treating the switching frequency as a constant in each computer run, a set of suboptimum design solutions were obtained by varying the frequency from 20 KHz to 60 KHz in 10 KHz steps. The U-shaped curve is observed by plotting the total loss characteristic against frequency. The following optimum design results are also obtained: 1) The optimum de duty ratio is about 0.3 to 0.34. 2) The converter should work at the critical mode between the discontinuous and current mode. 3) The air gap of the transformer core should be large enough (e.g.to 1.3 mm).