JPS6136431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color video output drive adjustment circuit for a color television receiver, and is particularly designed to enable excellent drive adjustment.

Hereinafter, one embodiment of the color video output drive adjustment circuit of the present invention will be described with reference to the drawings.

In Figure 1, 1 is, for example, as shown in Figure 2A, the pedestal level of the horizontal synchronizing signal of the video signal is 0IRE, and this white peak level is
When set to 100 IRE, the horizontal blanking period of this video signal indicates the red video signal input terminal to which the red video signal is set to the reference black level of 7.5 IRE, and is supplied to this red video signal input terminal 1. A red video signal with a horizontal blanking period set to the reference black level as shown in Figure 2A is
2 to the base of transistor 2. The collector of this transistor 2 is connected via a resistor 3 to a power supply terminal 4 to which a positive DC voltage +Vc is supplied, and the emitter of this transistor 2 is connected to a resistor 5.
It is connected to a negative power supply terminal 6 to which a negative DC voltage -Vc is supplied via. Reference numeral 7 indicates a reference pulse signal input terminal, and as shown in FIG. 2B, this reference pulse signal input terminal 7 corresponds to a predetermined time _T1 within the horizontal blanking period of the video signal as shown in FIG. 2A. The reference pulse signal Sa shown in FIG. 2B is supplied to the reference pulse signal input terminal 7 through the resistor 8. Supplied to the collector of transistor 2. Reference numeral 9 denotes a brightness adjustment signal input terminal, and as shown in _FIG . A brightness adjustment signal that has the width of the blanking period and can take an arbitrary DC value level V1 of both positive and negative polarities, ranging from DC voltage +Vs to -Vs centered on 0 according to the adjustment of the brightness adjustment device. The brightness adjustment signal 9a supplied to the brightness adjustment signal input terminal 9 is supplied to the collector of the transistor 2 via the resistor 10.

Therefore, the collector of this transistor 2 has a second
As shown in FIG. D, a signal is obtained in which the brightness adjustment signal 9a and the reference pulse signal Sa are superimposed within the horizontal blanking period of the phase-inverted red video signal as shown in FIG. 2A. In this case, the brightness adjustment signal 9a is centered at 0, and the reference pulse signal Sa is based on 0 voltage, so they can be directly superimposed, and the period of the reference pulse signal is included within the base interval of the brightness adjustment signal 9a. Therefore, this reference pulse signal Sa is inserted with the brightness adjustment signal 9a as a reference. This transistor 2
A red video signal as shown in FIG. 2D obtained at the collector of is supplied to a clamp circuit 11 constituting a part of the brightness adjustment device. In this clamp circuit 11, the second
Brightness adjustment signal 9a of the red video signal as shown in Figure D
is clamped to zero voltage. Therefore, in this case, by varying the level _V1 of the brightness adjustment signal 9a, the brightness of the image on the color cathode ray tube, which will be described later, can be adjusted. The output signal of this clamp circuit 11 constitutes a gain control amplifier circuit.
The red video signal of the color cathode ray tube 15 is supplied to the base of an npn transistor 12, and the collector of this transistor 12 is connected to the power supply terminal 4 via a load resistor 13. The emitter of the transistor 12 is connected to the drain of a resistance gate field effect transistor (hereinafter abbreviated as SRG) 16, and the source of the SRG 16 is grounded. In this case, this SRG 16 has an impedance value R ₁ between the drain and the source that changes depending on the voltage EG supplied to the gate, and R ₁
There is a relationship of ∝1/E _G , and the gain G of this transistor 12 is when the resistance value of the load resistor 13 is R _L Therefore, the gain G can be controlled by the voltage E _G. Further, the emitter of the transistor 12 is connected to the collector of an npn type transistor 17 having a constant current circuit configuration constituting the background adjustment circuit, and the emitter of this transistor 17 is connected to the power supply terminal 6 via a resistor 18.
The base of transistor 12 is connected to the connection point between the emitter of transistor 17 and resistor 18 via capacitor 19, and the base of transistor 17 is grounded via a series circuit of resistor 20 and capacitor 21.

In addition, a resistor 22 for dividing the output side of the amplifier circuit 14 is provided.
and 23 are grounded through a series circuit, the connection point of these resistors 22 and 23 is connected to the drain of a field effect transistor 24 constituting a gate circuit, and the source of this field effect transistor 24 is connected to the resistor 2.
5, an operational amplifier circuit 26 that constitutes a comparator circuit.
A gate signal input terminal 24a is derived from the gate of this field effect transistor 24. In this case, this gate signal input terminal 24
As shown in FIG. 2E, a gate signal S _G for gating the portion of the brightness adjustment signal 9a during the horizontal blanking period of the video signal is supplied to the signal a. Also, a variable resistor 27 for back ground adjustment is inserted between the power supply terminal 4 and the ground, and the movable element 27a of this variable resistor 27 is connected to the positive input terminal of the operational amplifier circuit 26. Grounded via capacitor 28. The error signal obtained at the output side of the operational amplifier circuit 26 is supplied via a resistor 29 to the connection point between the resistor 20 and the capacitor 21, thereby controlling the current of the transistor 17 constituting the constant current circuit to It is designed to adjust the background of the screen. Further, the output side of the amplifier circuit 14 is grounded through a series circuit of dividing resistors 30 and 31, and the connection point of the resistors 30 and 31 is connected to the base of an NPN transistor 32 constituting an emitter follower amplifier circuit. , the collector of this transistor 32 is connected to the power supply terminal 4, the emitter of this transistor 32 is connected to the negative power supply terminal 6 through a resistor 33, and the emitter of this transistor 32 is connected through a capacitor 34a forming a clamp circuit 34. The connection point between the capacitor 34a and the drain of the field effect transistor 35 is connected to the drain of the field effect transistor 34b forming the clamp circuit 34, and the field effect transistor The source of field effect transistor 34b is grounded, and a clamp signal input terminal 34c is led out from the gate of field effect transistor 34b. A clamp signal S _G corresponding to the brightness adjustment signal 9a portion of the horizontal blanking period of the video signal is supplied to this clamp signal input terminal 34c as shown in FIG. 2E, and the brightness adjustment signal 9a portion of this video signal is grounded. Clamp to a potential, that is, 0 voltage. Further, the source of the field effect transistor 35 is connected via a resistor 36 to the negative input terminal of an operational amplifier circuit 37 constituting a comparison circuit, and a gate signal input terminal 35a is derived from the gate of the field effect transistor 35. In this case, a corresponding gate signal is supplied to the gate signal input terminal 35a during the period _T1 in which the reference pulse signal Sa within the horizontal blanking period of the video signal is superimposed, as shown in FIG. 2F.

Also, a variable resistor 38 for drive adjustment is inserted between the power supply terminal 4 and the ground, and the movable element 38a of this variable resistor 38 is connected to the positive input terminal of this operational amplifier circuit 37. Grounded via capacitor 39. This operational amplifier circuit 37
The error signal obtained at the output side of is supplied to the gate of SRG 16 as a control signal.

In Fig. 1, red video signal input terminal 1
As shown in FIG. 2A, a red video signal whose horizontal blanking period is set to the reference black level is supplied to the reference pulse signal input terminal 7 as shown in FIG. 2B. A reference pulse signal Sa of a predetermined level V ₀ for a predetermined period T ₁ is supplied to the brightness adjustment signal input terminal 9 as shown in FIG.
As shown in FIG. 2D, since the brightness adjustment signal 9a centered on the 0 voltage during the period including the period _T1 of the reference pulse signal Sa within the horizontal blanking period is supplied, the voltage is applied to the collector of the transistor 2 as shown in FIG. 2D. Brightness adjustment signal 9 during the horizontal blanking period of the video signal
A signal on which the reference pulse signal Sa and the reference pulse signal Sa are superimposed is obtained, and this video signal is supplied to a clamp circuit 11, which clamps the brightness adjustment signal 9a portion of this video signal to, for example, 0 voltage. Since the video signal is supplied to the color cathode ray tube 15, the brightness in the color cathode ray tube 15 can be adjusted by adjusting the level _V1 of the brightness adjustment signal 9a. Also, during the horizontal blanking period of the video signal as shown in FIG. The level of the brightness adjustment signal 9a is gated by the transistor 24 and the voltage obtained at the movable element 27a of the variable resistor 27 for background adjustment is compared, and the output signal of the operational amplifier circuit 26 constituting this comparison circuit is used. Since the current of the constant current circuit constituted by the transistor 17 is controlled, the color cathode ray tube 1 is controlled by adjusting the mover 27a of the variable resistor 27.
5 background adjustments can be made.

Also, during the horizontal blanking period of the video signal as shown in FIG. portion is clamped to 0 voltage, and then the reference pulse signal Sa portion is gated by the field effect transistor 35 constituting the gate circuit, and this reference pulse signal Sa is extracted.
The level of Sa is compared with the voltage obtained at the movable element 38a of the variable resistor 38 for drive adjustment by the operational amplifier circuit 37 constituting the comparison circuit to obtain this error signal. The error signal is supplied to the gate of the SRG 16, thereby controlling the gain of the transistor 12, so that the movable element 3 of the variable resistor 38 for drive adjustment is
By adjusting 8a, drive adjustment, that is, white level adjustment can be performed. In this case, in the above example, the brightness adjustment signal 9a is clamped to 0 voltage, and the level of the reference pulse signal is detected using this as a reference, so that this level can be detected accurately and the brightness adjustment signal 9a that determines the background Since the signal level is adjusted using this as a reference, adjusting this signal level does not affect the background.

In addition, in the present invention, the same circuit as shown in FIG. 1 is provided for the edge color video signal system and the blue video signal system,
The respective output signals are sent to the green video signal supply terminal 15G and the blue video signal supply terminal 1 of the color cathode ray tube 15.
5B respectively.

In the present invention, the levels of the three primary color video signals can be adjusted by adjusting the movable element 38a of the variable resistor 38 for drive adjustment of each of the red video signal system, the green video signal system, and the blue video signal system. The drive adjustment can be made. Further, in the present invention, the level of the reference pulse signal superimposed on the horizontal blanking period of the video signal is detected, and the gain of the transistor 12 constituting the gain control amplifier circuit is adjusted based on the level to perform drive adjustment. Therefore, there is an advantage that the desired drive adjustment can be made regardless of the temperature characteristics of the device used. Further, in the above example, the brightness adjustment signal 9a is set to 0.
Since the voltage is clamped and the level of the reference pulse signal is detected using this as a reference, this level can be detected accurately, and the white level is adjusted using the brightness adjustment signal 9a that determines the background as a reference. There is an advantage that adjusting this white level does not affect the background.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations can be taken without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a color video output drive adjustment circuit according to the present invention, and FIG. 2 is a diagram for explaining the present invention. 1 is a red video signal input terminal, 2, 12 and 32
are transistors, 7 is a reference pulse signal input terminal, 9 is a brightness adjustment signal input terminal, 15 is a color cathode ray tube, 16 is an SRG, 34 is a clamp circuit, 3
5 is a field effect transistor constituting a gate circuit; 37 is an operational amplifier circuit constituting a comparison circuit; 3
8 is a variable resistor for drive adjustment.

Claims (1)

[Claims] 1. A reference pulse signal having a predetermined amplitude is superimposed on a part of the horizontal blanking period of each signal of the three primary color video signals and supplied to each gain control amplifier circuit, and the output signal of each gain control amplifier circuit is colored. supplying the signal to the cathode ray tube, detecting the level of each of the reference pulse signals in the output signal, comparing the respective detection level with a reference level, and controlling the gain of each of the gain control amplifier circuits using the comparison output. A color video output drive characterized in that the level of the three primary color video signals is adjusted by relatively adjusting the reference level in each system of the three primary color video signals. Adjustment circuit.