JPS5912864Y2 - TV receiver screen automatic adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic screen adjustment device for a color television receiver that automatically adjusts the screen condition according to external light surrounding the receiver.

The main purpose of the present invention is to perform all automatic screen adjustments using direct current, thereby eliminating the effects of noise and the like, as well as preventing any negative effects from occurring due to the automatic adjustments.

Another object of the present invention is to facilitate the interlocking adjustment of the video amplification circuit and the band amplification circuit in a color television receiver.

Still another object of the present invention is that it can be easily modified from conventional manual adjustment circuits.

As a device that automatically adjusts the brightness, contrast, and color saturation of the screen according to the external light surrounding the receiver,
Conventionally, intermediate frequency amplification circuits using AGC circuits have been known.

In this device, the impedance of the charging conversion element is changed according to the ambient external light, and the gain of the intermediate frequency amplification circuit is changed by changing the AGC voltage according to this impedance change, thereby improving the contrast and color saturation of the screen. I am trying to adjust the degree.

Furthermore, automatic brightness adjustment is performed by connecting the charging conversion element to a variable resistor for brightness adjustment provided in the video amplification circuit.

However, the method using such an AGC circuit has the following drawbacks.

The charging conversion element is connected between the input side of the AGC circuit and the video amplification circuit, and a video signal is applied to this input side from the video detection circuit.

Therefore, the video signal is also applied to the charging conversion element, which is subject to various restrictions on the circuit configuration.

Considering its purpose, the charging conversion element is located on the front panel of the receiver.
That is, it needs to be placed far from the internal circuits.

Therefore, the charging conversion element and the internal circuit must be connected using long lead wires.

Therefore, external noise is easily picked up and stray capacitance increases.

As a result, the video signal applied to the AGC circuit is attenuated and the original AGC operation is disrupted, or the output of the video detection circuit is reduced.

Therefore, if a shielded wire is used to avoid the influence of external noise, the stray capacitance will further increase, further deteriorating the AGC function.

In addition, a photoelectric conversion element is installed between the AGC circuit and the video amplification circuit in order to adjust brightness, contrast, and color saturation, but the circuit to prevent mutual interference between the two circuits becomes complicated. .

In particular, since both circuits must be separated by connecting a high resistance to the photoelectric conversion element, the sensitivity of the photoelectric conversion element is reduced and the adjustment range is narrowed.

In addition, the contrast and color saturation are adjusted by the AGC circuit, and the brightness is adjusted by a different method.
It is extremely difficult to change these three elements at the same rate.

Furthermore, since the AGC circuit is used, for example, when the electric field is weak and the ambient light is bright, the AGC is applied strongly and the gain of the intermediate frequency amplification circuit is reduced.

Therefore, the S/N of the screen becomes poor.

As described above, there arises the problem that the S/N ratio changes due to ambient external light.

The present invention eliminates the above-mentioned drawbacks by performing all adjustments using direct current.Examples of the present invention will be described below with reference to the drawings.

Figure 1 shows the circuit diagram of a general color television receiver. 1 is an antenna, 2 is a high frequency amplification circuit, 3 is an audio circuit, 4 is a speaker, 5 is a video detection circuit, and 6 is a video amplification circuit. circuit, 7 is a synchronous separation circuit, 8 is a deflection circuit, 9 is a convergence circuit, 10 is a high voltage rectifier circuit, 11 is a band amplification circuit, 12 is a color demodulation circuit, 13 is a matrix circuit, 14 is a petal ramp circuit, 15 is a real image tube.

16 is an adjustment circuit for automatically adjusting the screen according to the present invention, and its output DC control voltage V;

1. vo2 to the video amplification circuit 6 and the band amplification circuit 1
In addition to 1.

This DC control voltage V.

1. (2) Gain control is performed in the video amplification circuit 6 to adjust the average brightness and contrast using a conventionally known method using o2, and gain is controlled in the band amplification circuit 11 to adjust the color Saturation adjustment is performed.

Fig. 2 is a basic circuit diagram of the present invention, in which 17 is a photoelectric conversion element such as CdS, R1 and R2 are dividing resistors, T1 is a control transistor, R3 is a volume resistor for screen adjustment, 18 is a correction circuit, and 19 is the power supply terminal, and L is the external light.

When the resistance value of CdS changes depending on the illuminance of ambient light, the voltage change is applied to the base of transistor T1 via resistors R1 and R2.

As a result, the collector voltage at point A in the figure changes, and this voltage change is transmitted to the correction circuit 1 through resistor R3.
Added to 8.

From this correction circuit 18, a DC control voltage (2) is divided at an appropriate ratio.

1, 'VC2 is obtained and added to the video amplification circuit 6 and the band amplification circuit 11, respectively.

This allows the brightness, contrast, and color saturation of the screen to be automatically adjusted.

In this case, the petal clamp circuit 14 prevents the black level of the video amplification circuit 6 from changing.

For example, DC control voltage ■.

When increasing by 1, the amplitude of the video signal increases while the black level of the video signal is fixed, so that the average luminance increases and the contrast also increases.

As is clear from the above, the present invention uses the DC voltage change at point A in FIG.

It is designed to obtain 1°vo2.

Note that in the conventional manual adjustment circuit, the transistor T1, the resistors R1 and R2, the photoelectric conversion element 17, etc. are not present, and the point A is directly grounded.

Figure 3 shows an embodiment of the present invention;
The same parts as in the figures are given the same reference numerals.

Resistors R1, R2...Rlo are voltage dividing resistors to obtain the required voltages, R3 is a volume resistor for sensitivity adjustment, R5 is a thermistor for compensating temperature characteristics, and C is a resistor for the sudden change in external light. This is a capacitor installed to prevent the circuit from operating due to sudden changes.

20 is a high voltage power supply terminal, to which a high voltage (about 130V) is applied to the power supply of terminal 19 (about 18V).

By applying this high voltage to the transistor T1 via the resistor R0°Rlo, etc., the upper limit of the DC voltage change (approximately 18 cm) is always applied to the point A regardless of variations in the internal impedance of the transistor T1.

D is a protection diode.

According to the above configuration, when the transistor T1 is in a saturated state, the voltage between the collector and emitter of the transistor T1 is approximately O, and when the transistor T1 is non-conducting, its collector voltage is approximately the power supply voltage, so the DC current at the point A is Approximately 0 to 1 voltage
This voltage can be varied within a range of 8V, and this voltage is used as a reference level for the voltage dividing resistors R10 and R that constitute the correction circuit 18.
1°...... By dividing the voltage at a predetermined ratio by R2o, the DC control voltage ■c1. ■c2 can be obtained.

This DC control voltage ■c1. Due to vo2, for example, when the ambient light becomes dark, the voltage level at point A is lowered to darken the screen and lower the color saturation.

Also, at this time, the sensitivity of the automatic adjustment can be adjusted by varying the resistor R3.

In other words, resistor R3, which was conventionally used for manual adjustment.
You can use it as is to adjust the sensitivity.

As described above, the present invention includes a transistor T1 whose base is connected to the photoelectric conversion element 17, whose emitter is grounded, whose collector is connected to the power supply via the variable resistor R3, and whose gain is set to a control voltage. ■.

1; a pedestal clamp circuit 14 connected to the video amplification circuit 6 and fixing the black level of the video signal in the video amplification circuit 6; and a pedestal clamp circuit 14 whose gain is variable by the control voltage VC2. and a DC path 18 that commonly supplies the voltage generated at the collector of the transistor T1 to the video amplification circuit 6 and the band amplification circuit 11 as a control voltage, respectively. This invention relates to an automatic screen adjustment device for a television receiver that automatically adjusts the contrast and color saturation of the screen at the same time depending on the situation.

Therefore, according to the present invention, only DC voltage is applied to the charging conversion element, so even if this photoelectric conversion element and the internal circuit of the receiver are connected using a long lead wire, it will not be affected by stray capacitance. .

Furthermore, even if a shielded wire is used, its capacitance will not affect the circuit operation.

Furthermore, external noise can be removed by a simple method such as providing an AC bypass capacitor at one end of the lead wire on the internal circuit side.

In addition, since multiple controlled circuits are all controlled by DC voltage, common control that changes contrast, color saturation, and brightness at the same rate can be easily performed, and there is no interference between controlled circuits. .

Furthermore, these control operations do not affect the S/H of the screen.

Furthermore, with this invention, it is only necessary to insert a transistor on the ground side of the variable resistor of the conventional manual adjustment circuit, so when changing the design from a manual type to an automatic type at a manufacturing factory, even the printed circuit board for the automatic adjustment circuit part can be replaced with a new one. As long as it is made, there is almost no need to change the pattern of the conventional printed circuit board, so it is easy to change from a manual type to an automatic type, and the cost is also low.

Furthermore, since the photoelectric conversion element is connected to the base of the common emitter transistor and its collector control voltage is taken out, the variable range of the control voltage can vary widely from near the power supply voltage to near the ground voltage, and the video amplifier circuit and the gain of the band amplification circuit can be changed sufficiently.

Therefore, control sensitivity can be increased, and control with good linearity can be performed over a wide range of ambient external light illuminance.

Further, a variable resistor can be used for sensitivity adjustment.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a color television receiver to which the circuit of the present invention is added, Fig. 2 is a circuit diagram of the principle of the invention, and Fig. 3 is a circuit diagram showing an embodiment of the invention. . In addition, in the symbols used in the drawings, 6 is a video amplification circuit, 11 is a band amplification circuit, 16 is an adjustment circuit, and 17 is a C
dS, 18 is a correction circuit, and T1 is a transistor.

Claims (1)

[Scope of utility model registration request] A transistor with a photoelectric conversion element connected to its base, whose emitter is grounded, and whose collector is connected to a power supply via a variable resistor, a video amplification circuit whose gain is varied by a control voltage, and this video amplification circuit. A pedestal clamp circuit that is connected to the circuit and fixes the black level of the video signal in this video amplification circuit; a band amplification circuit whose gain is variable by a control voltage; A television receiver consisting of a DC path that commonly supplies a control voltage to each of the amplifier circuit and the band amplifier circuit, and automatically adjusts the contrast and color saturation of the screen simultaneously according to the brightness of ambient light. Machine screen automatic adjustment device.