Rca Inc.

Robert L Shanley, Ii

Leopold A Harwood

James Hettiger

Robert Preston Parker

Erwin J Wittmann

Jeffery B Lendaro

Jack Craft

Michael L Low

William A Lagoni

Thomas D Yost

Larry Allen Cochran

James McIntire Yongue

A control circuit of a television receiver power supply is constructed using a plurality of transistors operating in a common base configuration. The base electrodes of each of the transistors is coupled to a common conductor rail line that maintains the collector currents in the transistors temperature compensated over a wide range of operating temperatures during normal operation power-up mode of the receiver. In a standby mode of the receiver, power dissipation in the transistors is reduced by applying an on/off control signal to the common conductor rail line that prevents the flow of the collector currents in each of the transistors. Consequently, the supply current requirement of the control circuit is reduced during the standby mode.

On/off control circuitry for television

A supply voltage is developed in accordance with an on/off control signal of a remote receiver during a start-up interval and during a power-up mode of operation of a television power supply. During a standby mode of operation, the supply voltage is switched off. The supply voltage produces a supply current in an oscillator that produces a signal at a horizontal rate related frequency. The supply voltage also produces a base drive current in a switching transistor of a horizontal driver only during the start-up interval. During a power-up mode, a run supply voltage is coupled to the oscillator and to the driver.

Start-up control circuitry for a television apparatus

Non-inverting amplifier, with bandpass filter in regenerative feedback path, forms color reference oscillator in a color TV receiver. Phase shift circuit, responsive to an oscillator output, supplies signals to a first phase shifted signal amplifier, which shares a load with the non-inverting amplifier, and is subject to control by complementary outputs of a phase comparator functioning to compare the phase of an oscillator output with the phase of incoming color synchronizing bursts. A voltage comparator, responsive to the respective phase comparator outputs, is periodically enabled by field rate keying pulses. The voltage comparator output controls the charging or discharging of a capacitor during the keying intervals. A second phase shifted signal amplifier, responsive to the output of the phase shift circuit, and delivering its output to the oscillator's feedback path, is subject to control in dependence upon a comparison of a control voltage derived from the voltage held by the capacitor with a reference DC voltage. A latching circuit, subject to disabling only when receiver's color killer circuit operates in a color unkilling mode, is switched into a first latched mode of operation if voltage held by capacitor reaches a first extreme of its variation range, said first latched mode of operation forcing an unbalance of a first sense upon the voltage comparator inputs. Latching circuit is switched into a second latched mode of operation, forcing an opposite sense unbalance upon the voltage comparator inputs, if voltage held by capacitor reaches opposite extreme of its variation range.

Recovery system for a control loop

Non-inverting amplifier, with bandpass filter in regenerative feedback path, forms color reference oscillator in a color TV receiver. Phase shift circuit, responsive to an oscillator output, supplies signals to a first phase shifted signal amplifier, which shares a load with the non-inverting amplifier, and is subject to control by complementary outputs of a phase comparator functioning to compare the phase of an oscillator output with the phase of incoming color synchronizing bursts. A voltage comparator, responsive to the respective phase comparator outputs, is periodically enabled by field rate keying pulses. The voltage comparator output controls the charging or discharging of a capacitor during the keying intervals. A second phase shifted signal amplifier, responsive to the output of the phase shift circuit, and delivering its output to the oscillator's feedback path, is subject to control in dependence upon a comparison of a control voltage derived from the voltage held by the capacitor with a reference DC voltage.

Oscillator synchronizing system for eliminating static phase errors

Trilevel sandcastle pulse decoder includes a trio of voltage comparators for comparing incoming sandcastle pulses with reference potentials of respectively different levels. One of the voltage comparators, which is subject to change in operating state in response to appearance of a given level of the sandcastle pulse, is precluded from operating state change in response to the appearance of the next higher level of the sandcastle pulse by control circuitry responsive to the output of a second of the voltage comparators. One of the decoder outputs is developed by logic circuitry responsive to outputs of two of the comparators.

Tri-level sandcastle pulse decoder

A color television receiver includes AKB control circuits, operative during periodically recurring kinescope bias control intervals, for automatically adjusting the cathode biases of the receiver's color kinescope. To ensure the integrity of the bias adjustment operations undertaken by the AKB control circuits, the receiver is provided with a control system which includes: (1) keyed luminance/chrominance gain control apparatus, serving to effectively disable luminance and chrominance signal amplifiers during each kinescope bias control interval; (2) keyed brightness control apparatus for rendering the DC levels of color signal inputs to the receiver's kinescope drivers independent of the receiver's brightness control adjustment throughout each kinescope bias control interval; and (3) a control loop for controlling the DC level of the receiver's luminance channel output, which opposes departures of one of said color signal inputs from equality with a reference voltage throughout each kinescope bias control interval. A retrace blanking circuit, otherwise supplying beam cut-off biases to the kinescope cathodes during periods of beam retrace, is precluded from such cut-off bias application during beam retrace periods falling within the kinescope bias control intervals.

Control system for luminance/chrominance signal processing circuits

DC stabilization system for a color TV receiver includes three control loops, each including a keyed comparator for comparing a respectively different one of a set of blue, green and red color signals with a common reference voltage during keying periods determined by line rate keying of 'backporch' timing pulses. The output of the keyed comparator responding to the blue signal adjusts the DC level of a luminance signal component used in color signal formation. The output of the keyed comparator responding to the red signal adjusts the DC level of an I color-difference signal component used for color signal formation. The output of the keyed comparator responding to the green signal adjusts the DC level of a Q color-difference signal used for color signal formation. The line rate keying pulse source is subject to field-rate blanking to preclude comparator keying during significant portion of received signal's vertical sync interval.

Keyed DC stabilization system with protection from error introduction

DC stabilization system for color signal inputs to kinescope drivers of a color TV receiver (of a type employing AKB control) includes four control loops, one serving to adjust DC level of I color-difference signal, one serving to adjust DC level of Q color-difference signal, and two serving to adjust DC level of the Y (luminance) signal. One of the Y-adjusting control loops, employing a voltage comparator enabled only during periodic kinescope bias control intervals recurring at a field rate, is provided with an effective time constant which is short relative to the duration of a line interval. The other of the Y-adjusting control loops, employing a voltage comparator enabled only during backporch blanking portions of line intervals lying outside of the recurring kinescope bias control intervals, is provided with an effective time constant which is long relative to the duration of a line interval.

DC Stabilization system

Color reference oscillator comprises a non-inverting amplifier, with positive feedback via a crystal filter linking its output and input. A quadrature phase shift network, coupled to the filter output, delivers phase shifted signals to a pair of independently controlled amplifiers. One of the controlled amplifiers is responsive to control voltage outputs of a burst-responsive phase detector so as to inject phase shifted signals into the oscillator loop, as and when required, to effect synchronization of oscillator with burst component of incoming color television signal. The second of the controlled amplifiers is responsive to a reference DC voltage and to a manually adjustable DC control voltage, and develops a phase shifted signal output, of a magnitude and polarity dependent upon the magnitude and sense of the difference, if any, between the respective DC voltages, for combination with the non-inverting amplifier's output. Variation of the manually adjustable control voltage effects an adjustment of the free-running frequency of the oscillator.

PLL Oscillator synchronizing system with DC control of free-running

A pair of differential amplifier stages are connected in cascade to form a multistage amplifier for signal amplification purposes. The base-emitter paths of current source transistors which establish the operating currents for the respective stages are connected in series across a common source of forward bias voltage. The collector-emitter path of an additional transistor is shunted across the base-emitter path of one of the current source transistors. As biasing of the additional transistor is varied, the distribution of gain between the respective cascaded stages is altered substantially without disturbance of the overall gain of the multistage amplifier.

Amplifier incorporating gain distribution control for cascaded

Apparatus for simultaneously controlling the contrast of broadcast color video signal information and auxiliary color graphics information displayed by the kinescope of a color television receiver. Plural kinescope color signal coupling paths receive color video signals, a white drive graphics signal which is applied in common to the plural signal paths with a sense for enabling the kinescope to display color graphics information during graphics intervals, and plural blanking signals which are separately applied to the color signal paths for selectively blanking the outputs of the signal paths to determine the color of displayed graphics information. A picture control signal simultaneously varies the level of the color video signal and the level of the common white drive graphics signal in the same sense.

Picture control for television receiver on-screen display

Signals to be cored are applied to the inputs of a linear signal amplifier, and of a multistage limiting amplifier having cascaded input and output amplifying stages. A cored version of the signals, corresponding to the difference between a linearly translated version of the signals and a doubly clipped version thereof, is developed by a signal combiner responsive to the outputs of both amplifiers. A variable coring level control voltage controls the distribution of gain between the input and output amplifying stages, substantially without disturbing the overall gain of the limiting amplifier, which is set to match the overall gain of the linear amplifier. In an illustrative embodiment, the signals which are adjustably cored are horizontal peaking signals derived from the received luminance signal in a color television receiver. An automatic peaking control system associated with output of the adjustable coring circuit opposes changes in peaking level that might otherwise accompany coring level adjustment.

Adjustable coring circuit

Adjustable coring circuit includes linear amplifier and multistage limiting amplifier responsive to input signals from a common source. Limiting amplifier includes an input stage receiving operating current from a first current source transistor, in cascade with an output stage receiving operating current from a second current source transistor. Cored signal, corresponding to the difference between a linearly translated version of the input signals and a doubly clipped version thereof, is developed by a signal combiner responsive to outputs of both amplifiers. Base-emitter paths of the two current source transistors are connected in series across a common bias source. The base electrodes of two control transistors, of mutually opposite conductivity types, respond to variations of common coring level control voltage. Collector-emitter path of one control transistor shunts base-emitter path of first current source transistor. Emitter-collector path of other control transistor, which shunts the common bias source, is nonconducting over major portion of variation range of coring level control voltage.

Adjustable coring circuit permitting coring extinction

A television receiver includes a character generator for permitting kinescope display of auxiliary characters in addition to display of normal video signal information, and means for sensing a given characteristic (e.g., bias) of video signal processing circuits of the receiver during prescribed sensing intervals. The character generator is disabled during the sensing intervals to prevent false outputs from the character generator from distorting the characteristic being sensed.

Television receiver with selectively disabled on-screen character

A DC coupled signal translating circuit for supplying auxiliary graphics information switching signals to a video signal processor. The switching signal comprises plural switching levels including a quiescent level. The translating circuit includes first and second complementary conductivity input transistors with interconnected emitter signal inputs for receiving switching currents representative of the graphics switching signals via a conductor which undesirably exhibits a parasitic capacitance. The transistors are biased to conduct a nominal quiescent current and develop collector output currents which are proportional to the input switching currents, and which are respectively coupled via current repeating networks to control inputs of the video processor. Switching delays attributable to the parasitic capacitances of the input coupling conductor are significantly reduced due to the emitter voltage clamping action of the input transistors for all conditions of the input switching signals.

Growing community of inventors

Indianapolis, IN, United States of America

Robert L Shanley, Ii