JP3414078B2 - Television receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver.

[0002]

2. Description of the Related Art Although the white balance is adjusted at the time of shipment from the factory, the current ratio of each cathode, which determines the output brightness of the primary color signal of the picture tube, shifts due to aging, and as a result, the white balance cannot be kept constant. .

A conventional auto cutoff for solving this problem will be described below with reference to FIG.

When the primary color (R, G, B) signals are input to the cutoff circuit 2, an automatic cutoff reference pulse is superimposed in the vertical blanking period of the signals.

The signal is then applied to the cathode of CRT3. The auto cutoff clamp circuit 4 receives the cathode current, extracts the autocutoff reference pulse proportional to the cathode current, and clamps it.

Then, again in the cutoff circuit 2, the extracted automatic cutoff reference pulse is compared with a preset reference voltage, and the cutoff (pedestal DC) is adjusted according to the difference.

That is, the feedback is applied by detecting the cathode current. The control circuit 1 serves to control the entire circuit.

[0008]

As described above, the use of the automatic cutoff has the advantage that the white balance is kept constant even if it changes over time. However, since the auto cutoff pulse is superimposed on the vertical blanking period, it does not normally appear on the screen, but when the power is turned off, the vertical deflection current becomes small, and as a result, the vertical blanking period is also displayed on the screen and the auto cutoff pulse is displayed. The problem that the off-reference pulse appears on the screen occurs.

[0009]

In order to solve the above problems, the television receiver of the present invention is provided with a circuit having a function of deleting the auto cutoff reference pulse when the power is turned off.

According to the present invention, even if the vertical deflection current becomes small when the power is turned off, the auto cutoff pulse superimposed in the vertical blanking period is not displayed on the screen.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, in a television receiver having a function of keeping a white balance constant by using an auto cutoff, the autocutoff reference pulse is deleted when the power is turned off. It is a television receiver with the function to do, and even if the vertical deflection current becomes small when the power is turned off, the auto cutoff pulse superimposed in the vertical blanking period is
It has the effect of not being displayed on the screen.

According to a second aspect of the present invention, a means for superimposing an auto cutoff reference pulse in the vertical blanking period of the primary color signal, a means for conversely deleting the auto cutoff reference pulse from the primary color signal, and a cathode of the CRT. A means for extracting an automatic cutoff reference pulse proportional to the current and the extracted automatic cutoff reference pulse are compared with a preset reference voltage, and the cutoff (pedestal D
This is a television receiver provided with a means for adjusting C). Even if the vertical deflection current becomes small when the power is off, the auto cutoff pulse superimposed in the vertical blanking period is displayed on the screen. It has the effect of never happening.

FIG. 1 shows an embodiment of the present invention.
Will be explained. In FIG. 1, the same parts as those of the conventional example shown in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

(Embodiment 1) In the configuration of FIG. 1, a pulse elimination circuit 5 is added from FIG. The operation described in the conventional example is the same in FIG. In addition to these operations, in the present embodiment, the control signal from the control circuit is input to the pulse deleting circuit 5 when the power is turned off, and in the pulse deleting circuit 5, the cutoff circuit 2 superimposes the automatic cutoff pulse in the vertical blanking period. To delete.

[0015]

As described above, according to the present invention, the auto cut-off pulse is not displayed even if the vertical deflection current becomes smaller than the normal time when the power is turned off without impairing the effect of the auto cut-off. A television receiver can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional television receiver.

[Explanation of symbols]

1 control circuit 2 cut-off circuit 3 CRT 4 Auto cut-off clamp circuit 5 pulse deletion circuit

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 9/73

Claims (2)

(57) [Claims] 1. A television receiver having a function of keeping white balance constant by using auto cutoff, which has a function of deleting an autocutoff reference pulse when the power is turned off. Wherein the means for superimposing the vertical blanking period of the primary color signals automatic cutoff reference pulses, electrostatic
On the contrary, when the power is off, the means to delete the auto cutoff reference pulse from the primary color signal, the means to extract the auto cutoff reference pulse proportional to the cathode current of the CRT, and the extracted auto cutoff reference pulse are preset. Compared to the reference voltage
A television receiver equipped with means for adjusting the cutoff (pedestal DC) according to the difference.