Showing papers on "Flyback transformer published in 1984"

Power supply with noise immune current sensing

Abstract: A power supply (20) incorporates a switching regulator circuit and a flyback transformer (26) having diodes (42) for unidirectional current flow from an output circuit of the transformer to a load (24). Substantially noise-free sensing of currents in both input (32) and output (34) windings of the transformer is provided by a sensing circuit composed of a sense winding (46) on the transformer and an integrator (50) coupled to the sense winding. The integrator provides an output signal proportional to volt seconds or flux which, in turn, is proportional to either the input current or the output current. The input current and the output current flow alternately due to a switching action of the regulator circuitry. The regulator circuitry includes an electronic switch (38) coupled via a comparator to an output terminal of the integrator so as to initiate a pulse of current in the input winding when the output currents drop below a preset value, and to terminate the input current when the input current exceeds a preset value. A bank of capacitors (54) connected to the input winding (32) stores electric energy in the intervals between pulses for subsequent discharge into the transformer during the current pulses. The foregoing arrangement of the power supply circuitry provides for isolation of input and output sections of the power supply to prevent the coupling of noise. An overvoltage sensing circuit may also be coupled to the output winding (34) for acting via a logic unit to terminate input current during intervals of excessively high output voltage.

Flyback feedforward pulse width modulation regulator

Abstract: A flyback feedforward circuit for a pulse width modulated DC power supply in which the duty cycle is determined by varying the slope and peak amplitude of the sawtooth waveform under the influence of a weighted sum of input and output voltages.

Apparatus for accommodating inductive flyback in pulsed motor windings

Abstract: Control circuits for operating electric motors of the class having windings pulsed in sequence and a magnetic field, the class being exemplified by brushless d.c. motors. Improved apparatus is provided for accommodating flyback action when excitation current through any one of the windings is interrupted by the opening of a switch device (e.g., on-off controlled transistor), whether that device be a sequence power switch or a main switch having a common series relation to all of the power switches and operated with an adjustable duty cycle so as to permit adjustment of motor speed and torque. The flyback apparatus, as here disclosed, provides low loss flyback current paths so as to return inductively stored energy back into the winding when its excitation is interrupted, thereby to enhance motor efficiency while eliminating high open circuit voltages across the switching devices. Negative torque which might be created in the flyback circuits as a result of back e.m.f. in a winding is precluded by threshold circuit elements or by timed control of the conductive and non-conductive states of the flyback current paths.

High voltage pulsed power supply with time limiting nonlinear feedback

Abstract: An apparatus for supplying high voltage pulsed direct current to an X-ray tube includes a transformer, a high frequency inverter circuit and a nonlinear feedback loop. The invention uses the high frequency inverter connected in series with a DC power supply source and the primary winding of the transformer in order to generate high voltage, high frequency AC in the secondary winding. A rectifier connected to the secondary winding supplies high voltage pulsed DC to the X-ray tube. A detector, such as a voltage divider, detects the voltage supplied to the X-ray tube and supplies a representation of it to a nonlinear feedback circuit connected between the detector and the high frequency inverter. The inverter circuit includes at least one switch generated by electrical pulses. The nonlinear feedback circuit controls the duty cycle of the inverter during only a portion of the output voltage range of the high voltage pulsed power supply, preferably only after the output voltage reaches 90% of the rated high voltage to be supplied to the X-ray tube.

East-west correction circuit

Abstract: In a deflection circuit, a flyback transformer and a retrace resonant circuit that includes a deflection winding are mutually coupled by a relatively small capacitor during the retrace interval so as to reduce transient distortions that may be caused by a sudden high beam current change. East-west modulation is provided to the deflection circuit output stage via an impedance having a relatively large value at the retrace frequency. A resonant circuit that includes the deflection winding and the flyback transformer is tuned to the retrace frequency. Synchronization information of the current through the deflection winding may be derived from a winding of the flyback transformer.

Electric‐field exposure of persons using video display units

Abstract: Electric fields produced by a selection of video display units have been measured over a frequency range from DC to 1 MHz. The magnitude and the time variation of the electric fields were both recorded by means of a single broadband capacitive sensor located on the surface of a simple simulation of the human body. The electric field at a given location was found to be the sum of three discrete components, each having a different spatial and time variation. These components are produced by, respectively, the charged CRT screen, the flyback transformer, and the low-voltage circuitry. For the units tested, operator exposures are substantially below the limits of existing workplace guidelines.

Remote controlled television receiver power supply

Abstract: A mains rectified DC input voltage is applied to a series-pass regulator to develop a regulated B+ supply voltage. To reduce dissipation in the series-pass transistor, a shunt resistor parallels the series-pass transistor. To place the remote controlled television receiver in the standby-mode of operation, a remote standby control circuit applies an on/off command signal to the horizontal deflection circuit. Operation of the horizontal deflection circuit during the off-state of the command signal is disabled, thereby disabling the flyback transformer derived voltage supplies. A thyristor is placed in series with the shunt resistor and blocks current flow to the B+ supply terminal from the input voltage terminal during standby. To resume run-mode operation, the remote standby control circuit generates the on-state of the command signal to reenable horizontal deflection circuit. Current flowing to the B+ supply terminal from the regulator series-pass transistor also flows in an inductor to induce a voltage that is coupled to the gate of the thyristor to turn on the thyristor and reconnect the shunt resistor in parallel with the series-pass transistor.

Power source circuit

Abstract: A switching power source circuit intermittently switches a current at a primary winding of a transformer in accordance with the repeated switching of a bipolar transistor so as to rectify and smooth a voltage induced at a secondary winding of the transformer, thereby obtaining an output voltage A capacitor is charged by a voltage induced by a feedback winding of the transformer The base-emitter path of the bipolar transistor is reverse biased by this charge voltage so as to perform high-speed switching, so that a compact transformer and capacitor can be used and the switching power source circuit becomes low in cost The application of the reverse bias voltage is performed by a transistor which is turned on when an emitter (grounded through a resistor) voltage of the bipolar transistor is increased to a predetermined level (threshold) A switching period of the bipolar transistor is determined by a period determining circuit consisting of a timing capacitor and a resistor The timing capacitor is charged to reverse bias the bipolar transistor when the bipolar transistor is turned on The timing capacitor is discharged when the bipolar transistor is turned off An auxiliary winding is arranged in the transformer to detect flyback energy, and the ON and OFF times of the bipolar transistor are controlled to stabilize the output voltage even if an output terminal is overloaded

Audio amplifying apparatus and method

Abstract: An audio amplifier operatively connected to the secondary winding of a power transformer. The primary winding of the transformer is connected through a control circuit which has switch means that is turned on and off during selected portions of half cycles of the voltage imposed upon the primary winding of the transformer. By turning the switch on and off at appropriate intervals, the proper amounts of electrical energy can be delivered to supply the power requirements for amplification, while substantially reducing problems of idling currents in the primary winding of the transformer. Thus, the transformer can be made much smaller than in power supplies of conventional amplifiers.

Current driven flyback power supply

Abstract: A current driven flyback power supply (10) has a transistor current switch (24) which periodically couples a primary current through the primary winding (26) of a power transformer (22) which is connected between a source of DC and the collector of the current switch (24). A current transformer (32) has a first winding (38) coupled between the primary winding (26) and the collector of the current switch (24), and a second winding (40) which develops a drive current proportional to the primary current. The drive current is coupled to the base of the current switch (24) and increases proportionally with the increasing amplitude of the primary current. An electrical switch (44) shorts the drive current to ground to turn off the current switch (24) so that stored energy in the power transformer (22) is coupled out through its secondary winding (28) to an output rectifier circuit (48) which develops the output DC voltage. After the stored energy has been completely coupled out through the secondary winding (28) a first current pulse is developed to turn on the current switch (24) to initiate the primary current. During high output power loading conditions, a second current pulse is developed at a selected point in time after the current switch (24) turns off and prior to the stored energy being completely coupled out through the secondary winding (28). The second current pulse turns on the current switch (24) whereby the initial primary current is boosted in amplitude by the residual stored energy in the power transformer (22).

Flyback modulated switching power amplifier

Abstract: A flyback modulated switching power amplifier is described. The amplifier employs a waveform generator to produce an input signal and power switches capable of controlled conduction in one direction and uncontrolled conduction in the other. An inductor is coupled to the power source through the power switches so that flyback current can flow through a switch in its uncontrolled direction from the inductor when the switch is turned off. A conduction feedback circuit detects conduction by the switches and a comparator detects whether the output is "too high" or "too low" relative to the input signal. A logic control selectively activates the switches to control the output voltage, but not until the last switch to be turned off has stopped all conduction, including flyback conduction.

DC-DC converter with galvanically isolated feedback voltage regulation

Abstract: A switched mode power supply has a sense transformer (TX2) with three windings. A first (primary) winding (WD) is in series with the primary winding (WP1) of the power transformer (TX1). Current regulation of the output is provided via a second (sense) winding (WS). Voltage regulation of the output is provided by a further (third) winding (WC) being connected in parallel with the secondary winding (WP2) of the power transformer for producing isolated feedback of an output voltage error signal using the sense transformer (TX2) as a current summing transformer.

Electrostatic air cleaner and high voltage power source therefor

Abstract: Electrostatic air cleaner apparatus is disclosed for use in conjunction with existing space conditioning apparatus which includes a transformer providing a low voltage (typically 24VAC) power signal. The apparatus includes a power supply which is adapted to be coupled to the output of the transformer for providing a low voltage DC power signal. A high voltage generator and regulator is included which is powered by the low voltage DC power signal. The generator and regulator includes a flyback transformer arrangement which generates a high voltage DC signal suitable for energizing the collector and ionizer stages of an air cleaner assembly. The generator and regulator also includes closed loop feedback for regulating the amplitude of the high voltage DC signal so that it remains at or near the optimum amplitude regardless of variations in the amplitude of the low voltage power signal supplied by the existing low voltage transformer. The apparatus also includes an air cleaner assembly to which the high voltage DC signal is applied.

Transformer computer design aid for higher frequency switching power supplies

Abstract: A transformer computer design aid is presented that was developed for use at switching frequencies above 100 kHz where the classical method of using the saturation constraint results in an overheated transformer due to excessive core loss. Flux density is selected instead by an optimization procedure that minimizes total transformer losses. Key equations used in the design procedure are developed. Emphasis is placed on the algorithm used in the transformer design procedure.

Steady-State Characteristics of the Push-Pull DC-to-DC Converter

Abstract: Six modes of operation for the push-pull 4c-to-dc converter are presented by taking into account the magnetizing current of the transformer If the inductance of the transformer is decreased, the region where the output voltage is abnormally high is expanded in the load characteristics

Power supply circuit utilizing transformer winding voltage integration for indirect primary current sensing

Abstract: In a power supply having transformer coupling for regulation of voltage by a pulsing of primary current, a control circuit integrates the output voltage to obtain a measure of flux and primary current. A comparator monitors the integrated voltage to terminate a pulse of primary current prior to saturation of a core of the transformer. This insures linear operation and efficient transfer of energy from the primary to the secondary windings of the transformer. A sensor of secondary current initiates a new pulse of primary current when the secondary current has decayed to a fractional value of the peak secondary current.

High voltage generating circuit

Abstract: A circuit for generating a dc high voltage supplied to an anode of a cathode-ray tube, having a simplified circuit structure and reduced size A first horizontal deflection circuit applies a first flyback pulse across the primary coil of a flyback transformer, while a second horizontal deflection circuit supplies a second flyback pulse to a lower voltage side of the secondary coil of the flyback transformer through a coupling capacitor A dc voltage supplied to the second horizontal deflection circuit is controlled in response to the output voltage of the secondary coil of the flyback transformer A current detection circuit for automatic brightness limiting is coupled to the lower voltage side of the secondary coil of the flyback transformer for detecting changes in the secondary current of the flyback transformer

Remote, inductively coupled, transducer interface

Abstract: An exciter and detector circuit (A1, A2) is inductively coupled (18, 20) with a current conductor (B). The current conductor extends to a remote location at which it is inductively coupled (26, 30) with a remote transducer and encoder circuit (C1, C2). The exciter and decoder circuit supplies a square wave signal of a fixed frequency and amplitude across a primary winding (18) of the inductive coupler. After each half cycle of the square wave as the magnetic field in the inductive coupler is collapsing, a flyback voltage peak is generated which varies with the load applied to the current conductor. At the remote location, a voltage to frequency converter (40) converts variations in the output of the transducer into corresponding variations in a frequency signal. A load modulator (42) is connected with the voltage to frequency converter to apply a load to the rectifier at the frequency of the voltage to frequency converter. This causes the amplitude of the flyback voltage peaks to vary with an envelope frequency which is the same as the frequency of the voltage to frequency converter. A detector frequency to voltage converter (70) converts the envelope frequency into a voltage which varies in proportion to the envelope frequency, hence, to variations in the condition sensed by the transducer.

Differential-type protective relay

Abstract: In a differential-type protective relay actuated to generate a signal necessary for the protection of a bus (1) of an electric power system when a troubled current has flown through the bus, a gapped first transformer (13-4, 23-4) is used to receive an output from a current transformers (12, 22) which are adapted to detect each current in the bus. Each output of a first detection element, which is actuated when the output of the first transformer is higher than a preset level, is fed out to the exterior only when a value obtained by subtracting the sum of the maximum of the output of the first transformer and the value of a signal obtained by shifting the phase of the output through a predetermined angle from the value of a signal obtained by subjecting the output of the first transformer to full-wave transformation is equal to or lower than a preset value.

Switching power source

Abstract: PURPOSE:To improve the efficiency by providing a 3-terminal control element and a reference voltage source in a resetter for discharging flyback energy. CONSTITUTION:A switching power source is composed of an output circuit 3 having a transformer 1, field effect transistor (FET) 2 as a switching element, and diodes 31, 32, a controller 5 which has a pulse-width modulator for controlling ON, OFF the FET 2, and a DC power source 6. In this case, a transistor 81 is connected as a 3-terminal control element between the terminals of the first winding 101 of the transformer 1, and a series unit of a resistor 82 and a Zener diode 83 as a reference voltage source are connected to form a resetter 8, which is connected between the base B and a ground. Thus, when the voltage applied to the FET 2 becomes the prescribed level to the reference voltage source 83, the transistor 81 is conducted to suppress the voltage applied to the FET 2 to the prescribed level.

Power modulator provided with a transformer

Abstract: The invention concerns a power modulator provided with a transformer. This transformer having a high transformation ratio receives a low voltage impulse and transforms it into a high voltage impulse directly applicable on a high frequency or hyperfrequency tube in order to create a powerful impulse magnetic field. The transformer is particularized by the realization of its primary composed of a plurality of primary windings, all of which are connected in parallel and which, put end to end, extend along the entire lengths of the secondary. They are wound furthermore around the secondary and not inside it.

High voltage pulsed power supply for an x-ray tube

Abstract: For supplying high voltage direct current to an X-ray tube (11), a high frequency inverter circuit (3, 8) is connected in series with a source (1) of direct current and a step-up transformer (2). The output of the transformer is rectified and applied across the X-ray tube (11). A nonlinear feedback loop (12, 13) is responsive to the rectified voltage and can supply an error signal through contacts (13d) to the inverter circuit (3 - 8) to bring the rectified voltage to a required value. Contacts (13d) are only closed when a comparator circuit (13e) detects that the rectified voltage has reached a datum value less than the required value.

Horizontal output circuit for television receiver

Abstract: PURPOSE:To make distortion corrections by flowing all of the primary current of a flyback transformer which flows when a horizontal output transistor (TR) is on to a distortion correcting capacitor from a light load to a heavy load. CONSTITUTION:When the load is light (less DC component to flyback transformer 10), the primary current of the transformer 10 is fed back to a power source 11 in a damper period, but the capacitor (C) 15 which is charged by a power source 11 when a horizontal TR 17 is on and a distortion correction control TR 18 is off is still charged to apply a reverse bias to the distortion correction control TR 18. Consequently, all of the feedback current to the power source 11 flows to the C15 to pass through the C15 while discharging the C15. When the load is intermediate, the feedback current from the transformer 10 to the power source 11 is reduced, but all of the current flows through the C15 to reduce charges in the capacitor. When the load is heavy, no feedback current flows to the power source 11 and the current flows from the power source 11 to the transformer throughout a horizontal period. At this time, the control TR 18 turns on to charge the C15.

Combined transformer and variable inductor

Abstract: A pot-core transformer with a magnetic shunt variable to add the function of a variable series inductor independent of the transformer.

A Method for Estimating the Sinusoidal Iron Losses of a Transformer from Measurements Made with Distorted Voltage Waveforms

Abstract: A method for estimating the sinusoidal iron losses of a transformer from measurements made under highly distorted voltage waveform conditions is proposed. No assumption of the hysteresis/eddy current loss division within the transformer is required. A maximum discrepancy of 2% between the corrected and actual sinusoidal measurements was obtained during the testing of a 50 kVA, 2400 V single phase transformer with voltage waveforts containing six zero crossings per period.

Horizontal deflection circuit

Abstract: PURPOSE:To eliminate ringing generated in a flyback transformer by connecting a series circuit of a coil having a number of turns nearly equal to that of a high voltage coil of a flyback transformer and a resistor in parallel with a winding part at the beginning of the high voltage coil CONSTITUTION:Each layer (winding parts 15a-15d) of the high voltage coil 11 of the flyback transformer 12 has a nearly equal number of turns and the high voltage coil is overlayered on the primary coil 13 wound on a core 20 so as to be concentric to the core 20, then the coupling between the layers of the high voltage coil 15 are improved very much and no loop to cause a ringing is constituted among the winding parts 15a-15d because no AC potential is provided among the layers, thus the ringing is caused only between the winding part 15a of the beginning of the high voltage coil 15 and the primary coil 13 This ringing energy is consumed by a DC resistance component of the coil 17 and a resistive component of a resistor 18 by connecting a series circuit 19 comprising the coil 17 and the resistor 18 to the winding part 15a of the beginning adjacent to the primary coil 13, thereby attenuating the ringing

A new variable-voltage parametric transformer using bridge-connected magnetic circuit

Abstract: This paper describes operating characteristics of a new parametric transformer with variable output voltage. The parametric transformer is constructed with two of a bridge-connected magnetic circuit, and the value of the parametrically-generated output voltage is easily controlled by dc current. An application of the parametric transformer to a dc power stabilizer with high performance is presented in this paper.

Horizontal deflection circuit with raster distortion correction

Abstract: A horizontal deflection circuit with raster distortion correction includes a horizontal deflection winding coupled to a first retrace capacitor and an input inductance such as the primary winding of a flyback transformer coupled to a second retrace capacitor. Horizontal switching elements are operated at a horizontal deflection rate for generating current in the inductance and a horizontal scanning current in the deflection winding. During retrace, the horizontal deflection winding and the first retrace capacitor form a first resonant circuit and the input inductance and the second retrace capacitor form a second resonant circuit. One of the switching elements decouples the resonant circuits from each other to minimize the interaction therebetween. A source of raster distortion correction current is coupled to the deflection winding to provide the required scanning current modulation.

Dc high voltage generator

Abstract: PURPOSE:To reduce the amplitude of a ringing component of a scan period by connecting a circuit consisting of a capacitor, a resistance and a diode between both terminals of a high voltage winding of a flyback transformer and in the polarity that can rectify the voltage in the scan period of a flyback pluse. CONSTITUTION:A diode Da, a capacitor Ca and a resistance Ra are added to a double voltage rectifier circuit 3 connected to a high voltage winding N2 of a flyback transformer T2. A circuit block 2 containing above-mentioned elements is connected to both winding start and end terminals (b) and (c) of the winding N2 in the polarity that can rectify the voltage of the scan period of a flyback pulse. In a scan period the currents flow to both circulation paths Y and Z. For the path Z, the diode Da conducts by a potential difference of the forward direction peoduced between both terminals (b) and (c). However said voltage does not contribute to the DC high voltage output of a terminal HT. While said voltage is always applied to both ends of the capacitor Ca, said voltage is always applied to both ends of the capacitor Ca, and a current produced from the corresponding voltage always flows into the path Z through the resistance Ra. This current attenuates greatly a ringing component.