Television drive control circuit

Claim 2

In a television receiver including a drive amplifier having a variable gain dependent upon the adjustment of means for producing a variable impedance, the improvement comprising: circuit means for coupling said variable means in circuit to control the gain of said drive amplifier in proportion to the adjustment of said variable means; and means for establishing a fixed reference potential regardless of the adjustment of said variable means by effectively disconnecting said variable means from said circuit when a drive signal has a value equal to a predetermined value.

Claim 3

The improvement of claim 1 for a television receiver including a display device having a drive element coupled to said drive amplifier and a control element for controlling the intensity of display, including cut-off means coupled to said control element for selecting a black level within a range of signals from said drive amplifier, said cut-off means being adjusted to select said black level when said drive signal has said predetermined value, whereby said fixed reference level corresponds to a black reference level.

Claim 4

The improvement of claim 2 wherein said reference establishing means includes switch means for disconnecting said variable means from said circuit, thereby establishing the black reference level during a set-up mode.

Claim 5

The improvement of claim 1 wherein said reference establishing means includes a constant voltage source for generating a constant voltage, said circuit means couples said variable means in series with said constant voltage source to cause current flow in one direction through said variable means for drive signals above said predetermined value, drive signals below said predetermined value causing current to flow in an opposite direction.

Claim 6

The improvement of claim 4 wherein said circuit means includes impedance means connected in shunt with said series connected variable means and constant voltage source to form an alternate current path for said drive amplifier when current flows in said opposite direction through said variable means.

Claim 7

The improvement of claim 5 wherein the drive amplifier includes a semiconductor amplifying device having a pair of output electrodes and a control electrode, signal source means coupled to said control electrode for biasing said semiconductor device in proportion to a received television signal, said circuit means connecting in series said variable means, said constant voltage source and said output electrodes so that the impedance of said variable means controls the degenerative gain of said semiconductor device.

Claim 8

The improvement of claim 6 wherein said signal source biases said semiconductor device above cut-off when the current through the semiconductor device produces a drive signal voltage at a junction in the series connected circuit means equal to said constant voltage, whereby said constant voltage corresponds to said predetermined value.

Claim 9

The improvement of claim 4 wherein said constant voltage source comprises resistance means and Zener diode means connected in series across a DC potential source, the junction between said resistance means and the Zener diode means being DC coupled to said variable means.

Claim 10

In a color television receiver including first and second drive amplifiers for first and second color channels, respectively, the improvement comprising: first variable impedance means coupled with said first drive amplifier to control the gain thereof and vary the amplitude of a first drive signal at a first junction in proportion to the impedance of the first variable impedance means; second variable impedance means coupled with said second drive amplifier to control the gain thereof and vary the amplitude of a second drive signal at a second junction in proportion to the impedance of the second variable impedance means; reference means for producing a constant voLtage; and means connecting said first and second variable impedance means to said reference means for causing each variable impedance means to have no control over the gain of the drive amplifier associated therewith when the amplitudes of the drive signal at the associated junction is less than the amplitude of said constant voltage.

Claim 11

In a color television receiver including first and second drive amplifiers for first and second color channels, respectively, the improvement comprising: first variable impedance means coupled with said first drive amplifier to control the gain thereof and vary the amplitude of a first drive signal at a first junction in proportion to the impedance of the first variable impedance means; second variable impedance means coupled with said second drive amplifier to control the gain thereof and vary the amplitude of a second drive signal at a second junction in proportion to the impedance of the second variable impedance means; reference means for producing a constant voLtage; and means connecting said first and second variable impedance means to said reference means for causing each variable impedance means to have no control over the gain of the drive amplifier associated therewith when the amplitudes of the drive signal at the associated junction is less than the amplitude of said constant voltage.

Claim 12

The improvement of claim 9 wherein said connecting means includes first shunt impedance means connected to bypass current around said first variable impedance means and second shunt impedance means connected to bypass current around said second variable impedance means, and circuit means for effectively disconnecting said first and second variable impedance means from said drive amplifiers when said drive signals are equal to said constant voltage, whereby the currents through the drive amplifiers flow through said shunt impedance means.

Claim 13

The improvement of claim 9 including color temperature adjustment means comprising a first means forming a current path from said first variable impedance means to said reference means and effective when enabled for changing the gain of the first drive amplifier, a second means forming a current path from said second variable impedance means to said reference means and effective when enabled for changing the gain of said second drive amplifier, and gate means for enabling said first and second means.

Claim 14

The improvement of claim 11 for a color television receiver including a display device having a pair of drive elements coupled to said first and second drive amplifiers and control element means for controlling the intensity of display, cut-off means coupled to said control element means for selecting a black level for different levels of signals from the drive amplifiers, said cut-off means being adjusted to select said black level when said drive signals equal said constant voltage.

Claim 15

The improvement of claim 11 wherein said gate means comprises semiconductor means forward biased into conduction to enable said first and second means, and color killer means effective when only a black and white or only a color signal is being received for forward biasing said semiconductor means.

Claim 16

The improvement of claim 11 for a color television receiver wherein said first drive amplifier corresponds to a red color channel and said second drive amplifier corresponds to a green color channel, said first means having an impedance lower than said second means to increase the red drive output of said first drive amplifier more than the green drive output of said second drive amplifier to cause the color screen temperature to warm for color reception.

Claim 17

The improvement of claim 9 wherein said first variable impedance means comprises a potentiometer having a wiper adjustable across a fixed resistance, and relative color means connecting one end of said fixed resistance with said first drive amplifier to control the gain thereof in proportion to the resistance between said wiper and said one end and connecting the other end of said fixed resistance with said second drive amplifier to control the gain thereof in proportion to the resistance between said wiper and said other end.

Claim 18

The improvement of claim 9 wherein said connecting means includes switch means connected between said reference means and said first and second variable impedance means for disconnecting the variable impedance means from said reference means during a set-up mode, and alternate current path means connected to said first and second drive amplifiers for shunting current when said first and second variable impedance means are disconnected from said reference means.

Claim 19

In a color television receiver including drive amplifiers in first, second and third color channels for driving a tri-color display device having grid means for controlling the intensity of the resulting color display, the improvement comprising: variable means having a single variable element adjustable for inversely controlling a pair of impedanCe means to cause a relative increase or decrease in impedance in one impedance means and a relative decrease or increase in impedance in the other impedance means, respectively; relative color means connecting said one impedance means in said first color channel to control the gain of the associated drive amplifier in proportion to its impedance and connecting said other impedance means in said second color channel to control the gain of the associated drive amplifier in proportion to its impedance; third color means for controlling the gain of the drive amplifier in the third color channel; and black level means connected to bias said grid means for cutting off the display to establish a black level.

Claim 20

In a color television receiver including drive amplifiers in first, second and third color channels for driving a tri-color display device having grid means for controlling the intensity of the resulting color display, the improvement comprising: variable means having a single variable element adjustable for inversely controlling a pair of impedanCe means to cause a relative increase or decrease in impedance in one impedance means and a relative decrease or increase in impedance in the other impedance means, respectively; relative color means connecting said one impedance means in said first color channel to control the gain of the associated drive amplifier in proportion to its impedance and connecting said other impedance means in said second color channel to control the gain of the associated drive amplifier in proportion to its impedance; third color means for controlling the gain of the drive amplifier in the third color channel; and black level means connected to bias said grid means for cutting off the display to establish a black level.

Claim 21

The improvement of claim 17 wherein said relative color means includes means for effectively disconnecting said variable means from control of the gain of said first and second color channels for a signal level of a predetermined constant value, said black level means adjusting the bias on said grid means to establish said black level when said signal levels equal said constant value.

Claim 22

The improvement of claim 18 wherein said effectively disconnecting means comprises constant voltage means for generating a constant voltage corresponding to said predetermined constant value, means connecting said variable means in series with said constant voltage means, and alternate current path means shunting said variable means to allow continued current flow through said drive amplifiers when said signal levels are below said constant voltage.

Claim 23

The improvement of claim 19 wherein said effectively disconnecting means includes set-up switch means connected in series between said constant voltage means and said variable means for creating an open-circuit to simulate the effect of signal levels equal to said constant voltage.

Claim 24

The improvement of claim 17 wherein said third color means comprises second variable means having a variable control element adjustable to proportionately control an adjustable impedance, and gain means connecting said adjustable impedance in said third color channel for controlling the gain of the associated drive amplifier in proportion to the impedance of said adjustable impedance.

Claim 25

The improvement of claim 21 including third variable means having a single variable element adjustable to proportionately control a variable impedance, and supplemental gain means connecting the variable impedance of said third variable means in said first color channel for controlling the gain of the associated drive amplifier in addition to the relative color means.