JPS5819886Y2 - color television receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a television receiver configured to switch brightness and contrast color saturation in conjunction.

For example, if the ambient brightness is extremely different, such as during a demonstration at a store and during normal viewing indoors, it is necessary to adjust the brightness of the receiver each time. In color television receivers, brightness, contrast, and color saturation are closely related to each other, so in order to always obtain the best screen condition, the latter two must be adjusted in accordance with the adjustment of the former. □The adjustment operation was really troublesome for the user.

Therefore, in addition to each adjustment volume that individually adjusts brightness, cost thrust, and color saturation, a switching circuit is provided to switch each adjustment circuit into, for example, two stages, and in each switching state, each of the three Color television receivers are already available on the market in which the optimal values are set in advance to always have a constant relationship, and the respective switching circuits are switched in conjunction with each other.

However, in conventional television receivers of this type, the brightness switching circuit controls the clamp level of the DC component regeneration circuit, the contrast switching circuit controls the feedback amount of the video amplifier circuit, and the residual color saturation switching circuit controls the clamp level of the DC component regeneration circuit by resistor division. It was configured to switch the magnitude of each chroma signal.

For this reason, each of the switching circuits is independent, so three switches are required for each switching, and the number of components increases.

However, the present invention proposes a color television receiver that eliminates these drawbacks, and the details thereof will be explained below with reference to an embodiment shown in the drawings.

In the drawing, 1 is the transistor of the first video amplifier circuit, 2 is the first stage transistor of the second video amplification circuit whose emitter follower output is used manually, and the emitter of this transistor 2 is connected to the resistor 3 and the brightness adjustment variable resistor. 4 and a smoothing capacitor 5, the movable terminal of the variable resistor 4 is connected to the DC power supply (+
A brightness switching circuit 9 is configured by being connected to B l ).

Reference numeral 10 indicates a transistor in the latter stage of the second video amplification circuit, and reference numeral 11 indicates a transistor in the third video amplification circuit.The base of the latter transistor 11 has one of its fixed terminals connected to the AC ground through a resistor 12 and a capacitor 13 for contrast adjustment. The movable terminal of the variable resistor 14 is connected to the other fixed terminal of the variable resistor 14 and the transistor 1.
A contrast switching circuit 18 consisting of a changeover switch 15 interlocking with the switch 8 and resistors 16 and 17 is provided between the 0 and the emitters.

Reference numeral 19 denotes a color drive circuit consisting of three transistors 19', 19'', and 19''' to which the emitter follower output of the transistor 11 is applied to each emitter and each color difference signal output from the color signal circuit IC 20 is applied to the base. The collector output of each transistor is applied to each cathode K of the color picture tube 25, but the color drive circuit 19 has no special features, so its detailed portion is omitted in the figure. are doing.

The color signal circuit IC 20 includes almost all of the chroma-related circuits such as a color demodulator having terminals 23 and 24.1 for deriving the color difference signal outputs and a chroma amplifier having a gain control terminal 20 to which a DC voltage is applied. This IC has a pair of fixed terminals connected between the power supply (+B, ) and a ground point, and a variable resistor 26 for color saturation adjustment, and a movable terminal connected to a resistor 27.2.
The color saturation switching circuit 3 is connected to the control terminal 20 through the resistor 8, and the connection midpoint of this resistor is connected to the other fixed contact of the changeover switch 8 through the resistor 29.
0 is added.

In addition, the drawing numbers showing each terminal of the IC20 are from this I
It represents the terminal number of C.

In a color television receiver having such a configuration, when the selector switches 8 and 15 are currently on the 1tCH side (as shown in the figure), it is in a high brightness state corresponding to the demonstration at a store, etc. The DC potential of the transistor 2 is approximately determined by the resistor 6 and the variable resistor 4, and the signal output (emitter follower output) of the transistor 10 is determined by short-circuiting both ends of the resistor 16. , x is transmitted to the variable resistor 14, and the DC potential of the control terminal 20 is determined by the resistor 27.29 and the variable resistor 26, omitting the input impedance of the IC 20 seen from this terminal. The brightness, contrast, and color saturation are each set to predetermined values to provide the best screen condition.

Next, move the changeover switches 8 and 15 to the opposite position as shown (L side).
When switched to , it is a low brightness state corresponding to normal viewing indoors, etc. In this case, the emitter DC potential of transistor 2 is approximately determined by resistors 6 and 7 and variable resistor 4, so it is not possible to switch to the above-mentioned high brightness state. the DC potential at each cathode of the picture tube 25 rises, as is clear from the circuit connections shown, and the signal output of the transistor 10 is divided by the resistor 16, 17 and applied to the variable resistor 14. As a result, the luminance signal input to each of the cathodes becomes smaller,
On the other hand, the DC potential of the control terminal 20 is determined by the variable resistor 26 and therefore becomes low.

Therefore, in this case, the brightness of the picture tube 25 is lower than in the high brightness state, and its contrast and color saturation are also slightly lower, providing an optimal screen condition in this case.

In the color television receiver of the present invention as described above, the brightness switching circuit and the color saturation switching circuit, which are linked to each other, are designed to switch the DC bias voltage, so the switch for switching between the two circuits is also used. This type of interlocking switching type television can be constructed in a number of ways, and the switching circuit is switched to split the signal output, which reduces the number of components. Practical as a receiver.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing the main components of the color television receiver of the present invention. 2.10, 11: Transistor of video amplification circuit, 8.1
5: changeover switch, 9: brightness changeover circuit, 18: contrast changeover circuit, 30: color saturation changeover circuit.

Claims (1)

[Scope of utility model registration request] The emitter of the first transistor in the video amplifier circuit is provided with a first and second switch that switches to the -A0 side and the low (G) side in conjunction with each other, and a DC voltage for brightness adjustment is applied to the emitter. L of the first switch via a resistor
Connect the fixed terminal on the H side, connect the movable terminal to a DC power source with a voltage higher than the DC voltage, and connect the fixed terminal on the H side to the variable resistor for color saturation adjustment connected to the DC power source. The sliding terminal is connected via a resistor, the sliding terminal is connected to a gain control terminal of the chroma amplifier circuit, and the output point of a second transistor in the video amplifier circuit whose input is the output of the first transistor is connected to the slide terminal via a resistor. Connect it to the H side fixed terminal of the second switch, ground the L side fixed terminal through one of the voltage dividing resistors, and connect its movable terminal to the output point through the other voltage dividing resistor. , one end of the other voltage dividing resistor opposite to the output point is connected to a video amplification circuit at the next stage.