Abstract: An electron beam tends to slope downwardly as it is deflected horizontally to form a raster in a video display apparatus. The sloping of the beam can cause geometric errors in the raster, for example orthogonality and parallelogram errors. A raster correction circuit substantially offsets the downward slope of the electron beam by modulating a vertical deflection current with an induced horizontal-rate raster correction current, thereby substantially eliminating orthogonality and parallelogram errors in the raster. In respective embodiments of an inventive arrangement taught herein, the horizontal-rate raster correction current is induced in the vertical deflection coils by magnetically coupling a filament pulse waveform, a horizontal deflection voltage waveform, or a horizontal deflection current into the vertical deflection coils.

Abstract: A control circuit is provided for an auxiliary power supply in an apparatus having run and standby modes of operation. The auxiliary power supply is energized by raw B.sup.+ voltage and operates in a switched mode, responsive to a feedback signal indicative of loading. A switching circuit, also energized by the raw B.sup.+ voltage, changes the auxiliary power supply between operational and non operational modes responsive to an on/off signal. The on/off signal is indicative of the run and standby modes of operation of the apparatus, for example a run supply voltage generated by another power supply in the apparatus. The switching circuit includes a switch optically coupled to a voltage threshold detector. The switch interrupts the feedback signal, for example by shunting to ground, in a manner which inhibits operation of the switching controller during the standby mode of operation of the apparatus.

Abstract: A cathode ray tube may utilize a focus mask color-selection structure. The focus mask structure is susceptible to localized, transient short circuit events, or breakdown events. These events may be caused by conductive particulates that become free within the cathode ray tube and provide a short circuit between first and second layers of the focus mask. The breakdown events are undesirable because they may result in cross-strand currents causing mask strand magnetization that can interfere with a video image on the screen of the cathode ray tube. A transformer rapidly senses random changes in a voltage or a current supplied to the second layer of the focus mask. A pulse waveform generator is coupled to the transformer and provides a pulse waveform responsive to the sudden change in voltage or current.

Abstract: The invention is about a dc/dc converter (1) fitted with switching means (11, 12) having a drive electrode (13, 14) each drive electrode (13, 14) being connected to polarization means (49,50). The switching means are to switch on and off a current coming from a direct source of current 2 and circulating in windings (17, 18, 5) of transformers (6, 7) of the converter. The improvement according to the invention comprises a protection circuit 24 connected to means (44) for detecting the value of current circulating in one of the windings (4, 5, 15, 19, 23) of the transformers. Outputs (47, 48) of circuit 24 are connected to the drive electrode (13, 14) of switching means (11, 12). Protection circuit (24) may be a bistable circuit that will lower voltage at its outputs (47, 48) in a permanent way if detected current has been to high, thus switching off in a permanent way switching means (11, 12).

Abstract: A coupler for coupling a CRT faceplate of a CRT to a lens. The coupler comprises a rigid portion having a CRT faceplate surface for coupling to the CRT faceplate and a lens surface for coupling to the lens. The coupler further comprises an elastomeric layer disposed on at least the CRT faceplate surface and lens surface of the rigid portion.

Abstract: A line deflection circuit for a television receiver or a switched-mode power supply operate with a switching transistor that is connected in series with the primary winding of a transformer and is periodically switched on and off by a switching voltage. In such a circuit, appreciable turn-on and turn-off losses, which reduce the overall efficiency of the circuit, are produced at the switching transistor, particularly at higher operating frequencies. Within a control circuit a DC voltage source is connected to the base of the switching transistor via a periodically actuated switch element and a coil having a core and a tap. The two parts of the coil are wound in opposite senses, and the tap is connected via a diode to ground or to the emitter of the switching transistor.

Abstract: A circuit for providing an output voltage to a pincushion modulator circuit. The circuit includes an amplifier having an input for receiving an input signal. The amplifier amplifies the input signal to produce the output voltage at an output of the amplifier which is coupled to an input of the pincushion modulator circuit. A compensation path eliminates instability at frequencies above a first frequency caused by interaction between the amplifier and the pincushion modulator circuit.

Abstract: The invention relates to a switched-mode power supply having a switching transistor which periodically switches through a voltage which is applied to a primary winding of a transformer, having a base current network and having a switching stage for operating the switching transistor, and having a control stage for stabilizing a secondary voltage, the switching transistor having a switched-on phase, an off phase and an oscillation phase during operation. The switching transistor (TP20) of the switched-mode power supply according to the invention is switched through step by step during switching on, via a high-resistance resistor (RP05, RP06, RP07), a primary winding (6, 7) and a capacitor (CP24) . After this, the switched-mode power supply oscillates autonomously via this winding (6, 7) and is controlled by the control stage (TP24) .

Abstract: A convergence correction circuit, for a cathode ray tube projecting images having keystone, differential sinusoidal and differential right-edge curl distortions, comprises generators for horizontal-rate, generally sinusoidal, horizontal-rate sawtooth and horizontal-rate pulse waveforms. A summer combines the horizontal-rate waveforms into a horizontal-rate composite waveform. A multiplier and an amplifier generate as an output signal a product of the horizontal-rate composite waveform and a vertical-rate sawtooth waveform. A convergence correction coil is coupled for receiving the output signal and generating a dynamic magnetic field correcting the keystone, differential sinusoidal and differential right-edge curl distortions.

Abstract: A power amplifier circuit drives a load with a convergence correction current which is proportional to a convergence correction voltage waveform that is applied to the power amplifier circuit. A predriver stage of the power amplifier circuit comprises first and second transistors in a push-pull configuration. First and second voltage divider networks bias emitter electrodes of the first and second transistors, respectively, so that a common-mode current flow between the first and second transistors is limited. The first and second voltage dividers also protect the first and second transistors, respectively, from damage caused by thermal runaway.

Abstract: A convergence correction voltage waveform is applied to a power amplifier circuit. An output stage of the power amplifier drives a deflection coil of a cathode ray tube with a convergence correction current, which is proportional to the convergence correction voltage waveform. A differential voltage potential across an output device of the output stage is compared against a predetermined reference voltage. As the differential voltage potential begins to drop below the predetermined reference voltage, a buck-topology voltage regulator, which is coupled to the output device, turns on. The differential voltage potential is thereby maintained at a level greater than the predetermined reference voltage.

Abstract: An electron beam tends to slope downwardly as it is deflected horizontally to form a raster in a video display apparatus. The sloping of the beam can cause geometric errors in the raster, for example, orthogonality and parallelogram errors. A raster correction circuit offsets orthogonality and parallelogram errors in a raster by modulating a horizontal deflection current at a vertical scanning rate. The raster correction current is phased in relation to a horizontal-rate deflection current such that scan lines in an upper-half portion of the raster are shifted to the right, and scan lines in a lower-half portion of the raster are shifted to the left.

Abstract: A voltage source, a transformer and a switching controller are coupled for switched mode generation of a regulated output supply voltage. A switching circuit responsive to an on/off signal turns the power supply on and off by establishing a conductive condition in a conductive path. A fault detector establishes a non-conductive condition in a part of the conduction path responsive to an overload condition. A delay circuit establishes a conductive condition in an auxiliary conduction path for a period of time after the power supply is turned on. The auxiliary conduction path becomes non-conductive when the fault detector establishes a conductive condition in the part of the conduction path. The part of the conduction path remains conductive absent an overload condition. A latch arrangement including the delay circuit maintains the non-conductive condition in the auxiliary conduction path until the power supply is turned off.

Abstract: A voltage source, a transformer and a switching controller are coupled for switched mode generation of a regulated output supply voltage. A switching circuit responsive to an on/off signal turns the power supply on and off by establishing a conductive condition in a conductive path. A fault detector establishes a non conductive condition in a part of the conduction path responsive to an overload condition. A delay circuit establishes a conductive condition in an auxiliary conduction path for a period of time after the power supply is turned on. The auxiliary conduction path becomes non-conductive when the fault detector establishes a conductive condition in the part of the conduction path. The part of the conduction path remains conductive absent an overload condition. A latch arrangement including the delay circuit maintains the non conductive condition in the auxiliary conduction path until the power supply is turned off.

Abstract: A circuit reduces the total number of resistors needed to provide the reference voltages to the plurality of comparators in a flash analog-to-digital converter. In such a circuit, a first string of unit resistances having a first plurality of taps is coupled to a second string of unit resistances having first and second ends and a second plurality of taps between the ends. A first active device has an input coupled to a first tap of the first string of unit resistances and an output coupled to the first end of the second string of unit resistances. A second active device has an input coupled to a second tap of the first string of unit resistances and an output coupled to the second end of the second string of unit resistances.

Abstract: A power supply comprises: a rectifier; a power preconverter coupled to the rectifier; a switched-mode power supply circuit coupled to the power preconverter; and, a phase control circuit for synchronizing operation of the power preconverter with operation of the switched-mode power supply circuit. An energy storage device may be coupled to the power preconverter and to the switched-mode power supply circuit. A preconverter switch conducts during each time interval that a power switch in the switched-mode power supply circuit conducts in order, for example, to charge the energy storage device. The preconverter switch begins conducting only after each time interval begins and always stops conducting before each time interval ends. In a portion of the time interval after the preconverter switch has stopped conducting, a current can flow directly from the power preconverter to the switched-mode power supply circuit without, for example, charging the energy storage device.

Abstract: A cathode ray tube may utilize a focus mask color-selection structure. The focus mask structure is susceptible to localized, transient short circuit events, or breakdown events. These events may be caused by conductive particulates that become free within the cathode ray tube and provide a short circuit between first and second layers of the focus mask. The breakdown events are undesirable because they may result in cross-strand currents causing mask strand magnetization that can interfere with a video image on the screen of the cathode ray tube. A rapid degaussing operation is initiated during the next subsequent vertical blanking period following detection of the breakdown event.

Abstract: A data storage device requires a nominal input supply voltage, within a range having upper and lower tolerance limits in which stored data is retained. A capacitor is coupled to the data storage device. A supply voltage has a voltage greater than at least the upper tolerance limit. A regulator energized by the power supply provides a regulated voltage to the data storage device and the capacitor, the regulator presenting a low leakage discharge path for the capacitor. A feedback circuit is coupled to the regulated voltage and the regulator, the regulated voltage being held, preferably precisely held, at a voltage level between the nominal input supply voltage and the upper tolerance limit. The capacitor energizes the data storage device following an interruption of power from the power supply, discharging very slowly through the low leakage discharge path. The stored data is retained for an extended period of time.

Abstract: A method and apparatus for apportioning standby power implements a first transition mode between standby and run modes of operation in which a control circuit is energized by a standby power supply in a fully active state and generates an on/off command signal responsive to detection of an input signal and a second transition mode between the standby and run modes of operation in which the control circuit is energized by the standby power supply in a partially active state and generates the on/off command signal and a drive signal generator is fully energized by the standby supply. An intermediate transition mode may also be implemented between the first and second transition modes, in which the control circuit and the generator are both energized in a fully active state for a brief interval by the standby power supply and an auxiliary energy source.

Abstract: An automatic degaussing circuit provides a video display apparatus with a degaussing capability over a wide range of ac mains sources. An ac mains source is coupled to a degaussing coil by a series interconnection of first and second temperature-sensitive resistances. The temperature-sensitive resistances have oppositely-tending temperature coefficients, so that a total dc impedance of the automatic degaussing circuit initially decreases after power is applied to the circuit.