Showing papers on "Flyback transformer published in 1982"

Switching dc-to-dc converters

Abstract: In a switching dc-to-dc converter an output current substantially free of pulsations is provided by summing a flyback current and transformed current response to the current used to build up the electromagnetic field that stores the energy for flyback.

Coupling power line communications signals around distribution transformers

Abstract: A circuit is described for bi-directionally coupling a communication signal around a distribution transformer. The circuit includes a single-phase coupling transformer with a primary to secondary voltage ratio approximately equal to that of the distribution transformer. A capacitor is connected to one of the secondary terminals of the coupling transformer. The capacitor is chosen so that the series circuit including the capacitor, the self inductance of the coupling transformer and, possibly, the series inductance of interconnecting lines is resonant at the carrier frequency of the communications signal. The series combination of the capacitor and the secondary of the coupling transformer can be connected between two of the conductors on the secondary side of the distribution transformer which are selected for communication signal propagation.

Communications signal bypass around power line transformer

Abstract: A circuit for bi-directionally bypassing a delta-wye transformer with a balanced phase-to-neutral power line communications signal, using passive components. The circuit includes a set of three capacitors connected in a wye configuration, each having one side connected to one of the three phase power lines on the delta side of the transformer. The circuit further includes a network connected from the node of the wye configuration of capacitors to the neutral conductor or conductors associated with the power lines on the two sides of the delta-wye transformer. The network includes a single phase transformer, as well as a capacitance connected from the secondary of this transformer to the node of the wye of the delta-wye transformer. The network further includes an inductive reactor connected from the neutral on the wye side of the delta-wye transformer to the node of the wye transformer. Component values of the network are selected so that the network is resonant from the three phase lines on the delta side of the transformer to the node on the wye side of the delta-wye transformer. Further, by selection of the voltage ratio of the single phase transformer, the voltage transformation ratio of the communications signal from the delta side to the wye side is made the same as the corresponding power voltage ratio of the delta-wye transformer.

High voltage, low power transformer for efficiently firing a gas discharge luminous display

Abstract: A power system comprising a high voltage, low power transformer that utilizes self-resonance parameters and pulse control techniques for efficiently firing a gas discharge lamp of the type commonly used to form a luminous advertising display. The transformer is fabricated from a material, such that the transformer will have a characteristic self-resonating frequency. The transformer is driven by Direct Current pulses from a source of supply thereof. The widths of the current pulses are controlled so as not to exceed one fourth the wavelength of the self-resonating frequency of the transformer. Performance is optimized when the repetition rate of the current pulses is directly controlled according to the self-resonating frequency of the transformer. By virtue of the present invention, an efficient transformer of relatively low weight, size, and cost is provided by which to fire the lamp of the display and thereby produce an apparent optical intensity that is approximately equal to that available from a conventional gas discharge power transformer. However, the energy consumed by the present transformer is substantially less than that expended by presently available transformers.

Regulated flyback power supply using a combination of frequency and pulse width modulation

Abstract: A switching regulator power supply operates at a variable high frequency and pulse width with low power dissipation and a minimum of complexity. The transformer primary windings which are included as part of a self starting circuit start a pulse generator having a variable pulse width and variable frequency. During operation, the input RC network of the pulse generator, in response to the input rectified AC line voltage, conditions the pulse generator to generate output pulses whose widths vary as a function of changes in the input rectified AC voltge. An error circuit coupled to the secondary winding compares the output DC supply voltage to a reference voltage and generates an error signal which is applied through a coupling circuit for further adjusting the frequency of the pulse generator within a desired range to existing load conditions.

Electronic microwave oven power supply

Abstract: A power supply for a magnetron is adapted to be powered from a regular power line and comprises an inverter means operable to provide an AC voltage of relatively high frequency. This relatively high-frequency AC voltage is applied to a step-up transformer, which transformer exhibits a relatively high leakage inductance between its input and output windings. A capacitor is connected across this transformer's output winding and effectively resonates with the internal inductance thereof. A rectifier and filter means is connected in parallel circuit with this capacitor, and provides an output of current-limited substantially constant-magnitude DC voltage for application to the magnetron. As a result, the magnetron is efficiently powered with a nearly constant DC voltage, as contrasted with the pulsed DC voltage normally used for powering magnetrons.

Constant power switching power supply

Abstract: A power supply for a gaseous discharge lamp in which power adjustments are made automatically to insure that rated lamp power is delivered regardless of changes in lamp impedance or line voltage which may occur. A high D.C. voltage is delivered to a step down low hysteresis transformer and electronic switching is provided to obtain a high frequency pulsed flow to the primary of the transformer. Sawtooth waves are generated and peak current is utilized to regulate closely power input to the transformer. A feature is the use of a programming resistor to select the desired power level for the particular gas discharge lamp.

DC-to-DC Switching converters

Abstract: DC-to-dc switching converters that deliver non-pulsating output current use a conventional transformer and a flyback transformer with primary windings recurrently connected in series to the primary d-c energy source and with secondary windings alternately connected to the output load.

The Resonance Effect of Oscillating System Overvoltages on Transformer Windings

Abstract: This paper investigates theoretically and experimentally the conditions for and the effects of internal transformer winding resonances produced by oscillating exciting voltages. In particular, it demonstrates that both short-line faults and energizations can cause high voltage stresses between points in the windings. Calculations and test results on internal transformer voltage gain under resonance conditions, critical line length, surge impedance ratio and other parameters are presented. The frequency characteristics of the transformer terminal impedance and of the internal voltage gain are displayed and the merits of terminal measurements discussed. At the present state of the art, only limited protection against oscillating excitation is available.

Core reset for single-ended dc-to-dc converter

Abstract: Saturation is avoided in the core of the transformer used for direct conversion in a single-ended dc-to-dc converter of the type using auxiliary flyback conversion through a plural-winding inductor. This is done by resetting the core with a winding threading the core, through which winding the secondary current of the plural-winding inductor passes.

Method and apparatus for balancing flux in a power transformer circuit

Abstract: Method and apparatus are disclosed for use with switching power transformer circuits for balancing and compensating for core flux caused by unswitched D.C. current flowing in the transformer. A method and apparatus for adjusting the duty cycle of the switching portion of the power transformer circuit serves to balance the flux present in the transformer core during each half cycle of the operation of the circuit.

Power converter symmetry correction circuit

Abstract: A pulse width modulated power converter having a single time multiplexed symmetry correction circuit operative to vary the pulse width of output drive pulses applied to an output transformer. As a result, the average current and thus the volt second product seen by each half of the transformer primary winding will be equal under steady state conditions. The transformer drive remains balanced over the entire dynamic range to prevent unwanted saturation of the transformer core.

Side pincushion modulator circuit with overstress protection

Abstract: A side pincushion corrected deflection circuit for a television receiver includes a deflection winding, a trace capacitor and a first switch for generating scanning current in the deflection winding. A modulator circuit includes a modulator inductor and capacitor and a second switch for generating a sawtooth modulator current in the inductor. The trace and modulator capacitors are charged from a B+ operating voltage source through the primary winding of a flyback transformer. A transistor stage in the modulator circuit shunts current away from the modulator capacitor to control the modulator and trace capacitor voltages. A vertical rate bias voltage is applied to the transistor stage and varies the shunt current at a vertical rate in a parabolic manner to provide side pincushion correction. Under fault conditions, such as an open-circuited deflection winding or trace capacitor, the modulator capacitor voltage tends to undesirably increase above the peak voltage developed under normal operating conditions. To prevent overstressing the modulator transistor stage, a diode clamp is coupled between the modulator capacitor and a source of reference voltage, thereby preventing the modulator capacitor voltage from substantially exceeding the reference voltage level.

High voltage power supply

Abstract: A high voltage power supply of the flyback type typically used in cathode ray tube displays or TV receivers operates in synchronism with the scan rate frequency of display and may either be self-synchronizing, externally synchronized, or externally directly driven. The power supply has a relatively high efficiency (75%), regulates three output voltages to within ±0.1% against source voltage variations and regulates its highest level voltage output to within ±0.1% against source voltage and load variations.

Flyback-forward boost switchmode converter

Abstract: A high-frequency, power converter circuit including a transformer for transforming electrical current and having a primary; at least one secondary winding of a first type, and at least one secondary winding of a second type The secondary windings of said first and second types are in flux-coupling relationship with the primary A source of electric current is operatively coupled to the primary to flow therethrough An electronic switch is used for periodically interrupting the flow of current through the primary to provide "on" and "off" periods therefor A flyback circuit is operatively associated with the secondary winding of the first type to provide a first output from the power converter circuit A secondary circuit includes a first diode and an inductor being series connected with the secondary winding of the second type, the diode being positioned in the secondary circuit to enable the inductor to store energy from the transformer during an on period The flyback circuit also has a diode positioned therein to enable current to flow to the first output during an off period; and a second diode is coupled to the junction between the first diode and the inductor to enable current to flow from the inductor to an output of the secondary circuit during an off period

DC to DC converter with self-starting flyback oscillator

Abstract: A power supply for an acoustic fuel injector (18) comprises a DC to DC converter (14) for supplying a regulated voltage to a frequency-controlled oscillator (16) which drives the injector valve or valves. The converter (14) comprises a flyback oscillator (28) including a switching transistor (32) and a transformer (34, 36) for applying rectified current pulses of variable amplitude and occurrence rate to an output capacitor (42). A variable impedance transistor (50) in the input circuit to the flyback oscillator (28) is controlled by a feedback signal (68) from the output circuit (30) to vary the cycle rate of the flyback oscillator (28) to maintain output voltage at a desired value. Start up of oscillations in flyback oscillator (28) is assisted by a resistive feedback connection (56) and oscillations are maintained by a tertiary transformer winding (38).

Current spike protection circuit for switch-mode power supplies

Abstract: A circuit which prevents the flow of excess spikes of magnetization current in the primary windings of a transformer used in a switch mode power supply is disclosed. The circuit comprises an AC coupled, peak detecting, negative feedback path from a current sensing resistor in the primary windings of the transformer to the input of the voltage regulator so that as excess primary winding current spikes begins to flow the driving switches on the transformer primary are rapidly turned off thereby preventing any further rise in transformer primary current.

Raster and stroke writing deflection amplifier arrangement

Abstract: A Raster and Stroke Writing Deflection Amplifier Arrangement for a cathode ray tube (CRT) is disclosed which uses a conventional vertical oscillator and vertical deflection amplifier and a conventional horizontal oscillator and synchronous horizontal deflection amplifier, both driving deflection coils for providing vertical and low power horizontal scan operation for raster scan writing of data, and a flyback transformer and rectifier for providing the high D.C. voltage required by the CRT anode by rectification of high surge voltages created during horizontal retrace periods. During each vertical retrace period a switch connects the synchronous horizontal deflection amplifier to a dummy yoke at a zero crossing of the horizontal deflection signal for uninterrupted operation, connects a source of horizontal stroke writing signals amplified by a linear amplifier to the deflection coil, and also connects a source of vertical stroke writing signals to the vertical deflection amplifier to drive the deflection coil to accomplish stroke writing of information during each vertical retrace period.

J.N. Park General Electric Corporate Research and Development Schenectady, NY and

Abstract: This paper presents a single transistor dc-dc converter that combines both forward and flyback action. The resulting circuit is ohmically isolated and can operate over a wide range of input-to-outp ut voltage ratios. An analysis of the circuit indicates that the forward and flyback portions of the circuit interact to produce three distinct regions of operation. With the design information presented, the circuit can be tailored to utilize the desirable characteristics of either con­ verter action for a specific application. The dynamics of the dual mode circuit are modeled by means of the state-space averaging technique. An ac-dc regulator that takes advantage of the wide operating range of the dual mode circuit operat­ ing off the ac line, with only a small input filter, is described. The intended application of a power supply generally determines what parameters (size, cost, weight, reliability, etc.) are most carefully controlled in its design. These dom­ inant parameters, along with the electrical specifications, will determine the approach taken. In regulated supplies where high efficiency is desired, the dc-dc switching converter is well suited. Within this category, the designer still has several choices. Each of the various types of high frequency dc-dc converters has its own distinct advantages and disad­ vantages for each application. Often, a compromise is neces­ sary because no single converter topology incorporates all the desired characteristics. The standard single transistor switching topologies are the buck (forward), the boost, and the buck/boost (flyback) cir­ cuits. As the name implies, the transistor in each of these circuits operates as a switch, ideally being either fully on or fully off. The duty cycle D represents the percentage of time the switch is closed. This controls the ratio of charging time to discharging time for the inductor. Since the average volt­ age on the inductor must be zero in the steady state, the ra­ tio V0I Vs is thus constrained by D. Notice that in the buck and boost converters, there is a period when energy flows directly from the source to the load, while in the flyback cir­ cuit the charging interval and the discharging interval do not overlap. If ohmic isolation and step-down capability are required, which is true of the majority of line operated dc supplies, the choice narrows to the isolated forward or flyback circuits shown in Figure 1. Note that the isolated flyback converter 1:N 2 :N 1

Bias voltage control device of electron beam machining device

Abstract: PURPOSE:To make a device small-sized and perform a stable control by providing a bias circuit tap on the secondary winding of an insulated transformer for heating a cathode and controlling the bias voltage through a negative-feedback circuit of a pulse width-modulated light signal. CONSTITUTION:A main power supply 1 is stepped up 2, rectified 3 and applied to a cathode 5, which is heated by a heating power supply 10 connected to an insulated transformer 25. An electron beam 7 machines a work 8 and the current value of the beam 7 is controlled by a current control device 24. The current value is detected by a resistor 13, compared with a reference power supply 15 and fed to a PID regulator 17. The output of the regulator 17 is fed to a light emitting diode 27 through a PWM circuit 26. A light signal is sensed by a photosensing diode 29 through an optical fiber cable 28. The sensed signal is demodulated and controls the input voltage of a bias transformer 35 through a transistor 33. The output of the transformer 35 is rectified and applied across the cathode 5 and a Wehnelt electrode 12. Accordingly, the device can be made small-sized and perform a stable control.

High-voltage stabilizer

Abstract: PURPOSE:To stabilize a high voltage with a few components without isolating a horizontal output circuit from a high voltage output circuit, by detecting the fluctuation of a beam current to change the capacitance of a capacitor of a resonance circuit of the horizontal primary system with this detected output. CONSTITUTION:A horizontal output transistor (TR)18 is driven with a horizontal output drive circuit 17 and a high voltage is applied to an anode 16 of a cathode-ray tube by a flyback transformer 6 and a high-voltage rectifier diode 9. When a beam current increases, the high voltage is dropped and a potential at point (b) split by resistors 14, 15 is dropped. When the potential at the point (b) is lowered, its change is outputted from an operational amplifier 10, the base potential of a resonance capacitance varying TR20 is lowered and the resonance capacitance comprising resonance capacitors 4, 19 is lowered. Thus, the voltage between secondary windings of the flyback transformer 8 is raised. When the beam current decreases, the reverse operation is performed.

Transformer coupled amplifier circuit

Abstract: A transformer coupled amplifier circuit that eliminates transformer induced non-linearities by way of a dual feedback path without sacrificing any of the inherent attributes of general transformer coupled amplifiers

Transformer coupled up-down converter

Abstract: A transformer coupled DC-to-DC converter provides a regulated output with only one active switch. The converter includes a switch, a diode and an inductor coupled to the primary of a transformer in a way which provides symmetry to the transformer as the duty cycle of the switch changes for regulation. The circuit may be current-fed by supplying an input voltage higher than the transformer ratio would indicate, or may be voltage-fed by providing an input voltage lower than the transformer ratio would indicate. The circuit is operated to charge an inductor through the switch and half the primary of a transformer and discharge the inductor through the other half of the primary so that equal energy is provided through the transformer during charging and discharging, thereby providing a symmetrical signal without the need for more than one switch.

Resonant scan deflection circuit with flyback voltage limiting

Abstract: This invention is designed to protect a resonant scan deflection transistor in a deflection circuit from extremely high flyback voltage pulses. The deflection transistor is protected against high flyback voltage pulses even though: the B+ voltage on the deflection circuit varies over a wide range, the rate of the base drive signal varies over a wide range, and the turn-off delay time of the deflection transistor varies from device to device and for any one device as the base drive signal rate changes. The circuit of this invention compensates for the variations in turn-off delay time (t D ) of the deflection transistor at different horizontal scanning rates, and, in response to this compensation, compares the B+ voltage level with the current in the deflection coil. An extra turn-off trigger signal is developed in response thereto for energizing the deflection transistor drive circuit. In response to the trigger signal, the deflection transistor turns off. Since the extra trigger signal (if needed) is received before the sync pulse is received, the deflection transistor turns off and is thereby protected against a dangerously large flyback voltage pulse.

Igniting device for transistor inverter

Abstract: PURPOSE:To increase the switching speed by supplying a sufficient negative bias voltage when the base of a transistor is OFF and expediting the extinction of a stored charge. CONSTITUTION:When a control transistor 1Tr is turned OFF from a conductive state, a pulse voltage of a flyback voltage is generated in a secondary winding Nb1 of a transformer 1T, and a power transistor 1Tr is turned ON. When the power transistor 1Tr is turned ON, the magnetic flux of a trasformer 1T is inceased in the positive direction, and the power transistor 1Tr keeps the ON state. In order to release this state, the control transistor 1Tr is turned ON. At this time, it is necessary to flow a reverse current sufficient to remove the stored charge as a control current. When the magnetic flux in the transformer 1T is set in the negative direction, a negative voltage is induced in the secondary winding Nb1 in the transformer 1T, and said voltage is effectively utilized for turning OFF the power transistor 1Tr.

Horizontal deflection circuit

Abstract: PURPOSE:To eliminate the effect of ringing appeared on the screen of a cathode ray tube and to achieve an excellent picture, by rapidly attenuating the ringing generated in a flyback transformer with a simple constitution CONSTITUTION:A secondary low voltage coil 10' and a high voltage coil 8' of a flyback transformer 6' are wound closingly, and the secondary low voltage coil 10' is formed with a conductor layer of metallic thin film with almost equal width as that of the high voltage coil 8' Thus, the degree of coupling between the coils 10' and 8' is high and the ringing generated in the high voltage coil 8' is transmitted to the coil 10' efficiently to flow a large ringing current to a rectifying/smoothing circuit 14 The current is charged in a capacitor 12, supplied to a DC load circuit 13 and consumed As a result, the energy is lost at each cycle of ringing and rapidly attenuated, allowing to prevent dark and bright longitudinal stripes on the screen of a cathode ray tube from being generated

Combined dynamic focus circuit flyback capacitor

Abstract: In a cathode ray tube (CRT) display system utilizing a semiconductor switch in the output stage of the fast scan axis, a resonant circuit is coupled to the flyback circuit for production of a dynamic focus voltage. The capacitance required for the flyback circuit is derived from the equivalent capacitance of the dynamic focus resonant circuit, thereby eliminating the need for a separate flyback capacitor.

Intrinsic safety power supply with a controlled semiconductor disposed in the primary circuit of a transformer

Abstract: We will describe a power supply device that works according to the principle of a clocked power supply unit. For this purpose a controllable semiconductor (3) is arranged in the primary circuit of a transformer (5), which is driven periodically by a clock generator (18). The duty cycle of the clock generator is influenced via an optocoupler (17) by a voltage regulator (16), on the one hand a reference value and on the other hand, the outputs of the power supply device (1) to be entered. In the secondary circuit of the transformer (5), a Short-circuiting Device (10) to which a throttle (14) and a voltage limiter (19) is connected upstream lie. A current limiting regulator (11) operates in such a manner that a decreasing current-voltage characteristic is obtained. A control switch (20) applies the voltage regulator (16), the Ausgangssgrosse of the current limiting regulator (11) and switches to the input variable, when the current limiting controller (11) limits the current.

Simple flyback checker

Abstract: A simple, low cost device for testing for shorted turns in the winding of electromagnetic coils or transformers by making use of the inductive kick voltage that is developed when the current through a coil is quickly interrupted. It uses rectified, unfiltered AC for power and a high speed switch to control the current through the coil under test. It has provisions for measuring the voltage developed by the inductive kick.

Vertical deflection circuit

Abstract: PURPOSE:To reduce the power consumption, by operating the vertical deflection output circuit at higher power supply voltage on blanking pulse period and operating it at lower power supply voltage determined with the voltage dynamic of output for the deflection period and increasing the power supply voltage utilization factor. CONSTITUTION:The vertical deflection signal in saw tooth wave in response to the vertical scanning and vertical blanking period is amplified at the preamplifier 1, this output drives the output transistors Trs7, 8 and Trs9, 10, deflection current is fed to the deflection yoke 13, and the flyback pulse produced in this yoke 13 is clamped at the clamp diode 11. The voltage +B1 from the high voltage terminal 21 is fed to the first power supply voltage applied terminal of the amplifier 1, and the low voltage side voltage +B2 from the power supply terminal 22 is fed to the power supply terminal of Trs7, 8 via the diode 20. Further, the resistor 18 is connected between the terminals 21 and 22, the capacitor 19 is connected to the terminal 22, Trs7, 8 are cut off at the deflection period, the capacitor 19 is charged up at the voltage +B1 with lower operation voltage to increase the utilization factor of power supply voltage.