JP3206021B2 - 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 color television receiver having the function of stabilizing white balance by detecting and feeding back a cathode ray tube (CRT) current and stopping vertical deflection for white balance adjustment. It is about the machine.

[0002]

2. Description of the Related Art In recent years, cathode color current detection has been used in color television receivers to stabilize white balance. On the other hand, a function of stopping vertical deflection for screen adjustment or white balance adjustment is used.

Hereinafter, a conventional television receiver will be described with reference to the drawings. (FIG. 3) is an example of a configuration of a conventional television receiver. (FIG. 3)
1 is a reference signal insertion circuit, 2 is an addition circuit, 3 is a cathode drive amplifier, 4 is a cathode current detection circuit, 5 is a bias control circuit, 6 is a sawtooth wave generation circuit, 9 is a switch,
10 is a vertical output amplifier, 11 is a cathode ray tube (hereinafter abbreviated as CRT), 12 is a timing generation circuit, and 13 is a PN.
A P-type transistor, 14 is a resistor, and 15 is a vertical deflection yoke.

The operation of the television receiver configured as described above will be described below by dividing the operation into a white balance stabilizing function and a vertical deflection stopping function.

[0005] First, the white balance stabilizing function will be described. The reference signal insertion circuit 1 inserts a reference voltage signal for bias control during a vertical blanking period of a video input signal. As shown in FIG. 4, a DC voltage for controlling one line of bias is inserted into the upper part of the screen which cannot be seen by overscan, in a time-divided manner, as shown in FIG. 4. The timing of insertion is created from the vertical deflection waveform in the timing generation circuit 12.

The video signal having the reference signal inserted therein is added with a bias control signal in an adding circuit 2 and further amplified by a drive amplifier 3 to a voltage sufficient to drive a CRT cathode. The cathode current detection circuit 4 is composed of an emitter follower amplifier composed of a PNP transistor 13 and a resistor 14. The cathode voltage is equal to the input voltage, and a detection voltage proportional to the cathode current appears at both ends of the resistor 14.

[0007] The bias control circuit 5 outputs a DC bias to the addition circuit 2 so that the output of the cathode current detection circuit 4 with respect to the reference voltage signal inserted by the reference signal insertion circuit 1 becomes an adjustment value. More specifically, a feedback loop is formed by comparing the output voltage of the cathode current detection circuit 4 with the adjustment voltage, integrating the error, inverting the polarity, and setting the result as the bias input of the addition circuit 2 so that the error becomes zero. Let it converge. That is, when a video input signal having a voltage equal to the reference voltage signal is input, the DC bias control signal is automatically adjusted so that a cathode current equal to the cathode current corresponding to the reference voltage signal, that is, a CRT luminance is obtained.

As described above, even if the characteristics of the CRT 11 and the drive amplifier 3 change, the bias can be automatically corrected so that the cathode current becomes constant, and the operating point of the CRT drive circuit is stabilized. CRT between primary colors
Variations in the operation of the drive circuit are suppressed, and white balance can be stabilized.

Next, the function of stopping the vertical deflection will be described. In FIG. 3, the output of the sawtooth wave generating circuit 6 and the no signal are switched by the switch 9 to stop the vertical deflection. Stopping the vertical deflection is equivalent to the fact that each horizontal line converges and the light on the CRT tube surface is amplified, which is useful for finding a cut-off point where the CRT starts to shine. Generally, the cathode voltage is set to a constant value, vertical deflection is stopped, and the screen voltage is adjusted at a point where the raster starts to emit light, so that the screen voltage is adjusted. Also, by adjusting the DC bias of the cathode drive amplifier at the point where each of RGB starts to shine, it is used for white balance adjustment in a dark part.

[0010]

However, in the above configuration, if the white balance stabilizing function and the vertical deflection stopping function are to be realized at the same time, the cathode current detection during the vertical blanking period is performed in the white balance stabilizing function. However, since the reference voltage signal is inserted, the raster of the reference voltage signal always appears, and the raster overlaps with the cutoff adjustment raster, so that the cutoff adjustment is difficult to perform.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a television receiver capable of stabilizing white balance and stopping vertical deflection to facilitate cutoff adjustment.

[0012]

In order to solve the above problems, a television receiver according to the present invention receives a primary color video signal and inserts a reference voltage signal for detecting a cathode current of a CRT in synchronization with a vertical synchronization signal. A reference signal insertion circuit, an addition circuit that adds a DC bias to an output signal of the reference signal insertion circuit, a drive amplifier that amplifies an output video signal of the addition circuit to a voltage sufficient to drive a CRT,
A cathode current detection circuit for detecting a cathode current of a CRT; and a bias for outputting a DC bias to the addition circuit so that an output of the cathode current detection circuit with respect to the reference voltage signal inserted by the reference signal insertion circuit becomes an adjustment value. A sawtooth wave generation circuit that includes a control circuit and generates a sawtooth wave for vertical deflection synchronized with a vertical synchronization signal, a differentiation circuit that differentiates an output signal of the sawtooth wave generation circuit, and delays an output signal of the differentiation circuit. A delay circuit, a switch for selecting an output signal of the delay circuit and an output of the sawtooth wave generation circuit, and a vertical output amplifier for amplifying a signal selected by the switch and driving a vertical deflection yoke. It is.

[0013]

According to the present invention, when the vertical deflection of the effective screen portion is stopped, the raster is deflected upward or downward only during the vertical blanking period, so that the raster of the cathode current detection reference voltage signal can be effectively changed. The screen part can be separated from the raster, making it easier to adjust the cutoff.

[0014]

An embodiment of the present invention will now be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention, and FIG. 2 is a timing chart of the television receiver according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a reference signal insertion circuit, 2 denotes an addition circuit, 3 denotes a cathode drive amplifier, 4 denotes a cathode current detection circuit, 5 denotes a bias control circuit, 6 denotes a sawtooth wave generation circuit, and 7 denotes a differential. Circuit, 8 a delay circuit, 9 a switch, 10 a vertical output amplifier, 11 a CRT, 12
Is a timing generation circuit, 13 is a PNP transistor,
14 is a resistor, and 15 is a vertical deflection yoke.

The operation of the above-configured television receiver will be described below with reference to FIGS. 1 and 2. First, the operation of the function of stabilizing the white balance of the signal system is the same as that of the conventional example, and will not be described.

Next, the operation of the deflection system will be described. The sawtooth wave generating circuit 6 generates a sawtooth wave synchronized with the vertical synchronization signal (FIG. 2B). In a normal use state of the television receiver, the switch 9 selects the output of the sawtooth wave generating circuit 6, and the vertical deflection yoke 15 is driven by the sawtooth wave. On the other hand, a vertical blanking pulse is obtained by differentiating the output of the sawtooth wave generating circuit 6 in the differentiating circuit 7 (FIG. 2C). Further, the vertical blanking pulse is delayed in the delay circuit 8 so as to match the reference signal insertion timing (FIG. 2-D) used in the reference signal insertion circuit 1 and the bias control circuit 5 (FIG. 2-D).

When the vertical deflection is stopped, the switch 9 is moved to the delay circuit 8 side, and a pulse corresponding to the reference signal insertion timing is selected, so that a deflection current shown in FIG. Due to this deflection current, only the part of the raster due to the reference voltage insertion is deflected upward, and there is no vertical deflection in the other parts, and each horizontal line is concentrated on one line. Therefore, the raster of the effective screen range can be viewed separately from the raster of the reference voltage signal, and the cutoff adjustment becomes easy.

In the embodiment shown in FIG. 1, the cathode is driven by the video signal to detect the cathode current. However, the first grid may be driven by the video signal to detect the cathode current.

In the embodiment shown in FIG. 1, the delay circuit 8 may be omitted, and the delay of the deflection current with respect to the terminal voltage of the vertical deflection yoke 15 may be used.

Further, in the embodiment shown in FIG. 1, the timing generation circuit 12 may be shared with the differentiating circuit 7 and the delay circuit 8.

[0023]

As described above, according to the present invention, a reference signal insertion circuit which receives a primary color video signal as input and inserts a reference voltage signal for detecting a CRT cathode current in synchronization with a vertical synchronizing signal,
An addition circuit for adding a DC bias to the output signal of the reference signal insertion circuit;
A drive amplifier that amplifies the voltage to a level sufficient to drive the CRT, a cathode current detection circuit that detects a cathode current of the CRT, and an output of the cathode current detection circuit corresponding to the reference voltage signal inserted by the reference signal insertion circuit to an adjustment value. A sawtooth wave generating circuit that includes a bias control circuit that outputs a DC bias to the adding circuit and generates a sawtooth wave for vertical deflection synchronized with a vertical synchronizing signal; A delay circuit that delays an output signal of the differentiation circuit, a switch that selects an output signal of the delay circuit and an output of the sawtooth wave generation circuit, and amplifies and vertically amplifies a signal selected by the switch. By providing a vertical output amplifier for driving the deflection yoke, the light on the CRT tube surface is amplified to cut the light. Be stopped vertical deflection to facilitate off adjustment, it is possible to provide a television receiver raster for raster and the cut-off adjustment of the reference voltage signal for the cathode current detection is not overlapped.

[Brief description of the drawings]

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

FIG. 2 is a timing chart of an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional television receiver.

FIG. 4 is a diagram showing a positional relationship between a reference voltage signal raster and a CRT effective screen;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference signal insertion circuit 2 Addition circuit 3 Cathode drive amplifier 4 Cathode current detection circuit 5 Bias control circuit 6 Sawtooth wave generation circuit 7 Differentiation circuit 8 Delay circuit 9 Switch 10 Vertical output amplifier 11 CRT 12 Timing generation circuit 13 PNP transistor 14 Resistance 15 Vertical deflection yoke

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-18087 (JP, A) JP-A-2-312388 (JP, A) JP-A-3-154497 (JP, A) JP-A-1- 208091 (JP, A) JP-A-58-6689 (JP, A) JP-B-49-30297 (JP, B1) JP-B-62-6397 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/73

Claims (1)

(57) [Claims] 1. A reference signal insertion circuit for receiving a primary color video signal as input and inserting a reference voltage signal for detecting a cathode ray tube cathode current in synchronization with a vertical synchronization signal, and adding a DC bias to an output signal of the reference signal insertion circuit. An adder circuit, a drive amplifier for amplifying the output video signal of the adder circuit to a voltage sufficient to drive a cathode ray tube, a cathode current detection circuit for detecting a cathode current of the cathode ray tube, and a reference signal insertion circuit. A bias control circuit that outputs a DC bias to the adder circuit so that the output of the cathode current detection circuit with respect to the reference voltage signal becomes an adjustment value, and generates a sawtooth wave for vertical deflection synchronized with a vertical synchronization signal. A sawtooth wave generating circuit, a differentiating circuit for differentiating an output signal of the sawtooth wave generating circuit, and an output of the differentiating circuit. A delay circuit that delays a signal, a switch that selects an output signal of the delay circuit and an output of the sawtooth wave generation circuit, and a vertical output amplifier that amplifies a signal selected by the switch and drives a vertical deflection yoke. Equipped television receiver.