Showing papers on "Flyback transformer published in 1968"

Circuit for reducing stray capacity effects in transformer windings

Abstract: A transformer charging system that provides a highly efficient operation and that substantially eliminates switching transients. The high voltage or secondary winding of the transformer as well as the primary winding in some arrangements, is divided into segments which are isolated from each other by unidirectional current conductive devices such as diodes. For charging a load coupled to the secondary winding, current pulses are repetitively applied to the primary winding from the power source with the flyback voltage resulting from the pulse terminations causing current to flow through the diodes. The diodes allow the stray capacitance associated with each segment to initially charge but prevent them from discharging between the repetitive operations, which would cause additional flow of primary current and dissipation losses.

Power converter circuit operating as an electric potential transformer

Abstract: A POWER CONVERTER CIRCUIT OF ELECTRONIC TRANSFORMER FOR AN A.-C. SUPPLY COMPRISES A LINEAR TRANSFORMER WHOSE WINDINGS ARE CONNECTED RESPECTIVELY TO INPUT AND OUTPUT TERMINALS THROUGH INVERTER CONFIGURATION SWITCHING CIRCUITS EMPLOYING BIDIRECTIONAL CONDUCTING SOLID STATE SWITCHING DEVICES OR INVERSE-PARALLEL PAIRS OF UNIDIRECTIONAL CONDUCTION SOLID STATE SWITCHING DEVICES. BY SYNCHRONOUSLY RENDERING CONDUCTIVE ONE SWITCHING DEVICE IN THE PRIMARY AND SECONDARY SIDE SWITCHING CIRCUITS, AND ALTERNATELY AND SYNCHRONOUSLY RENDERING CONDUCTIVE ANOTHER DEVICE IN EACH CIRCUIT AT A SWITCHING RATE SUBSTANTIALLY HIGHER THAN THE SUPPLY FREQUENCY, THE INPUT POTENTIAL IS CONVERTED TO A HIGHER FREQUENCY WAVE, TRANSFORMED, AND RECONSTRUCTED AT THE OUTPUT TERMINALS. IN THIS WAY THE SIZE OF THE TRANSFORMER IS REDUCED.

Electron beam deflection and high voltage generation circuit

Abstract: 1,260,375. Cathode-ray tube deflection circuits. R.C.A. CORPORATION. 11 April, 1969 [15 April, 1968], No. 18631/69. Heading H3T. [Also in Division H2] In a deflection circuit for a cathode-ray tube, a first bi-directional switching means 24 is arranged to be conductive during the forward stroke so as to connect deflection coil 22 across an energy supply device 23 and a second switching means 46 arranged to become conductive towards the end of the forward stroke, the switching means 24, 36 being coupled via a T- network comprising capacitors 29, 30 and inductor 28. As described, diode 26 is arranged to be conductive at the beginning of each trace so that a deflection current is driven by the large capacitor 23 through the deflection coils 22. Soon after the beginning of each forward stroke, a pulse is induced in winding 31 and fed to the gate of thyristor 25 so that the anode/cathode path becomes conductive when the deflection current passes through zero midway through each forward stroke 8 As before the end of each forward stroke, thyristor 37 is turned on by a pulse from the horizontal oscillator 19 so that energy which has been stored into capacitors 29 and 30 is circulated resonantly via circuits including components 24, 29, 28, 36 and 36, 28, 30. This provides a reverse current in thyristor 25 so that after the stored carriers have been dissipated, thyristor 25 becomes turned off, terminating the forward stroke. The resonant current now continues via diode 26 until a further reversal occurs when that diode is also turned off. Energy is thus returned to capacitor 23. Further current reversal similarly turns off thyristor 37 and (later) diode 38 so that a further forward stroke can start. The flyback pulses induced in transformer 43 (tuned to approximately the third harmonic of the flyback frequency) are rectified at 44 to provide E.H.T. for the cathode-ray tube. Circuits 46 ... 50 protect the circuit against E.H.T. flash-over. Capacitor 30 is arranged to resonate with its associated inductance at twice the flyback frequency. Stabilizing image width.-The exchange of energy between transformer 43 and the rest of the circuit is arranged so that, following variation in cathode-ray tube current, the corresponding change in deflection current is approximately one half the change in E.H.T. voltage so that the image width remains constant.

Lamp control circuit with high leakage reactance transformer and controlled bilateral switching means

Abstract: Load power control device for control of the operation of gaseous discharge lamps or other loads comprises a high reactance transformer having the primary connected to an alternating current voltage source, a secondary connected to the load, and a bi-lateral switch connected at the output of the high reactance transformer and in parallel with the load for controlling the power applied to the load.

DC to DC converter regulated by a constant- frequency duty-cycle generator.

Abstract: Closed loop regulated flyback DC to DC converter using constant frequency generator for duty cycle control

Television deflection circuit with compensation for voltage supply variations

Abstract: 1,179,962. Transistor sawtooth circuits; cathode-ray tube circuits. R.C.A. CORPORATION. 22 March, 1967. [28 March, 1966], No. 13574/67. Headings H3T and H4T. In a television receiver, the field time base capacitor 36 is charged from a voltage derived in such a way as to compensate for the effect on the vertical raster size of variations of the accelerating voltage of the cathode-ray tube caused by variations in supply voltage. As shown, capacitor 36 is charged via an amplitude control 40 from a voltage developed between the output of a series transistor regulator 82 and point A on a potential divider comprising a Zener diode 44 and resistors 46, 48. The charge is terminated by a synchronizing pulse fed via capacitor 60 to the base of switching transistor 22 so that capacitor 36 becomes discharged. The resulting sawtooth waveform is fed via an emitter follower 20 and an output transistor 18 to field deflection output terminals V, V 1 . The circuit is made self-oscillatory by positive feedback via capacitor 28 to the base of transistor 22. A further feedback circuit comprising transformer 26 and hold control 62 provides a parabolic waveform resulting in a steep slope near the end of each trace, thus providing noise immunity. A thermistor 78 and capacitor 76 arrange for the discharge of capacitor 36 to be terminated at an appropriate voltage to provide the correct quiescent current in transistors 20, 18. A linearity control circuit 50, 52, 54 enables an S-corrected output current to be achieved but prevents feedback at frequencies substantially lower than the field deflection frequency. An anti-lock-on resistor 24 is provided. Capacitor 32 by-passes signals at line frequency. A clamping circuit 34 protects transistor 18 against excessive flyback voltages. Amplitude stabilization: power supply.-The power supply may be derived from A.C. mains by a full-wave rectifier 79 or from a 12 V. battery and is stabilized by action of transistors 88, 82 and Zener diode 44. The charging circuit 40, 38 for the field capacitor 36 is derived from point A at the junction of resistors 46, 48, the values of which are such that the variation in field deflection amplitude due to supply voltage variation compensates for the effect of the supply voltage variation on the accelerating voltage of the cathode-ray tube.

Device for the automatic gain control and clamping of the black level for television receivers

Abstract: In a circuit for generating an automatic gain control voltage and for clamping the black level of television signals, a diode has one electrode connected to a video input circuit. Line flyback pulses are applied to the other electrode of the diode by way of a resistor, and an automatic gain control voltage is derived from the other electrode of the diode. A blocking circuit is provided to prevent conduction of the diode during the line synchronizing signal. A video output circuit capacitively coupled to the input circuit is clamped by a line flyback pulses which are also blocked during the line synchronizing period.

Gating circuit for displaced pulses

Abstract: A gating circuit useful for separating data pulses from clock pulses in a double frequency detection system includes a signal generator that provides a sawtooth waveform having ramp portions of the same slope and a flyback interval of fixed magnitude. When the sawtooth signal is above a variable threshold, an input gate is enabled to allow the clock pulses to initiate flyback. The proportions of the sawtooth waveform above and below the threshold remain constant, so that early or late arrival of a clock pulse does not affect the gating of succeeding clock pulses. Thus, an output gate is made to operate to block clock pulses while passing data pulses.

Television deflection circuit

Abstract: 1,216,996 Sawtooth circuits RCA CORPORATION 29 Feb, 1968 [21 March, 1967], No 9858/68 Heading H3P A vertical deflection circuit for a television receiver comprises a capacitor 46 for developing a sawtooth voltage waveform which is fed to the control electrode of an amplifying device 22, the output of which is coupled at V, V 1 to deflection windings A further capacitor 28 is charged by a diode 32 during the flyback period and discharged during the forward stroke via resistors 38, 40 connected to a stabilized voltage source Part of the waveform across capacitor 28 is coupled via resistor 42 to the grid so that the grid bias and hence the trace linearity is adjustable by resistor 30 The stabilized supply is preferably provided by a VDR 36 and is adjustable by resistor 38 (height control) The circuit is preferably made self-oscillatory by feedback from the secondary of the output transformer 24 via an integrator 56 to the base of transistor 50 which discharges the time base capacitor 46 at the end of each sweep A hold control 60 is provided The circuit is synchronized by pulses fed to the grid of valve 22 or the base of transistor 50 Modifications-Transistor 50 may be replaced by a vacuum triode Resistor 23 may be omitted