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: A vertical rate signal generator is coupled to an integrator for producing a vertical rate parabola signal. The parabola signal is applied to a band-pass filter for producing a vertical rate sinusoidal signal that is applied to a convergence winding. When a loss of the horizontal synchronizing signal occurs, the frequency of the sawtooth signal decreases. As a result, the DC, average level of the sinusoidal signal varies, during a transition interval, following restoration of the horizontal synchronizing signal. The band-pass filter filters out low frequency components. The duration of the transient interval is thereby reduced in a manner to reduce picture bounce. The peak amplitude of the sawtooth signal is also clipped for reducing the variation of the average level of the sinusoidal signal.

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 correction circuit for a cathode ray tube displaying images subject to distortions comprises: a multiplier for a first horizontal sine waveform and a vertical parabola waveform to define a correction signal, the vertical parabola having a zero value during vertical retrace; a summer for combining a second horizontal sine waveform with the correction waveform to define a composite correction signal, one of the second horizontal sine waveform and the correction signal being first inverted; and, a correction coil for the cathode ray tube receiving the composite correction signal and generating a dynamic magnetic field responsive to the composite correction signal for correcting a residual inner pincushion distortion and for correcting a horizontal linearity distortion imparted by the correction of the residual inner pincushion distortion.

Abstract: A circuit in accordance with an inventive arrangement comprises: a signal generator for a correction signal having a substantially parabolic shape at a scanning rate of the video display; a waveform clipper coupled to the signal generator for the correction signal, the waveform clipper having a current sink transistor coupled to the signal generator for the correction signal for clamping the correction signal, and a reference transistor coupled to a base of the current sink transistor for providing a reference voltage; and, a switch for disabling the reference transistor during excursions of the correction signal and enabling the reference transistor during clamping. The switch may comprise a switching transistor coupled to the reference transistor and to the correction signal, the switching transistor disabling the reference transistor during excursions of the correction signal and enabling the reference transistor during clamping.

Abstract: A deflection waveform correction signal generator comprises a parabolic shaped signal generator and first and second sawtooth shaped waveform generators. The first horizontal frequency sawtooth shaped waveform is generated by a clipped retrace pulse. The first sawtooth generator has an output coupled to an integrating circuit for generating a parabolic shaped signal. The sawtooth generator and sawtooth waveform integrator are reset at a horizontal rate by reset pulses of differing duration. The different duration of reset pulses results in the parabolic signal having regions of non-parabolic shape. A control loop is coupled to the integrator and measures and maintains a pulse duration generated responsive to the parabolic signal. A control current is generated responsive to the pulse duration and is coupled to the integrator input to cause the parabolic shaped signal to be generated at a predetermined time interval.

Abstract: A differentiation network differentiates a retrace pulse signal to produce a narrower pulse during the first half of retrace that is coupled to an input of a convergence amplifier. The convergence amplifier is coupled to a convergence winding to produce a convergence current. The narrower pulse produces an overshoot at the amplifier input and, thereby, speeds up the response time to the convergence amplifier.

Abstract: A wide bandwidth, high gain ultrasonic frequency transducer drive circuit utilizes a relatively low voltage source of supply voltage. A first signal path from a source of drive signals includes circuitry resonant with the transducer for providing a relatively high signal voltage across this transducer. A second signal path from the source of drive signals includes a resonant circuit mutually coupled to the first resonant circuit for inducing signal energy into the first path and increasing the signal voltage across the transducer.

Abstract: A tuner bandswitching system for a television receiver tuning system wherein a reset pulse generated at the completion of the selection of a channel to be received is utilized to determine the initial stable state of a series of bistable circuits and to provide a bandswitch reset pulse for use in establishing an initial voltage output from a voltage sweep generator utilized to scan a varactor tuned VHF tuner or a varactor tuner through one or more bands of frequencies. The bistable circuits control switching voltages supplied to the VHF tuner and the UHF tuner to provide for sequencing of the tuning system serially through, for example, the low VHF band, the high VHF band, and the UHF band until the appropriate band has been selected wherein the selected channel can be tuned. When the selected channel is tuned, a hold signal is developed. Data identifying the channel being received during a sweep through a given band is accumulated in a counter. At a predetermined output of the counter (e.g.

Abstract: A bandstart detector system for a television receiver tuning system wherein a sample of oscillator signals utilized for conversion of radio frequencies into intermediate frequencies is coupled to a plurality of tuned circuits. Detecting means are coupled to each of the tuned circuits to produce control signals having an amplitude inversely related to the difference between the oscillator signal frequency and the resonant freqency of each of the tuned circuits. The amplitude of the control signal will vary as the oscillator signal frequency is swept in a regular manner through a predetermined band of frequencies corresponding to television channel frequency allocations. The control signals are coupled to a sensing circuit which produces one output signal when the control signal is below a predetermined level and a second output signal when the control signal is above a predetermined level.

Abstract: A varactor tuner frequency controller wherein a tuning voltage is developed for optimumly tuning a VHF tuner or a UHF tuner to any one of a plurality of channels. A capacitor utilized to store charge for developing the tuning voltage is discharged by means of a pulse developed by a monostable circuit which is gated by a bandswitch reset pulse. Charging of the capacitor is provided for by a positive current source which supplies a substantially constant current to the capacitor in the absence of a hold signal, the hold signal only being present when a selected channel has been reached. In the presence of a hold signal, the current supplied by the positive current source is modified in accordance with an automatic fine tuning signal, and a negative current source supplies a substantially constant current to the capacitor approximately equal to the current supplied by the positive current source in the absence of the hold signal to effect a stopping of the sweep.