JPH06261265A - Television set - Google Patents

Abstract

PURPOSE:To prevent the luminance of a video signal display part from being influenced by the luminance of a side panel part on the display surface of a CRT. CONSTITUTION:To an electron beam limiting resistance 4 of an auto contrast limiter circuit (ACL circuit) 8 for limiting a beam current of a CRT 1, a series body of a beam current limit relaxing resistance 13 and a beam current limit relaxing transistor 14 is connected in parallel. In such a state, when a set luminance value of a side panel part is set to a prescribed value or above, a value of the beam current limiting resistance 4 is made small by allowing the beam current limit relaxing transistor 14 to conduct, so that suppression of an amplification factor of a video signal amplifier circuit 9 by a beam current is relaxed. In such a manner, when luminance (beam current) of the side panel part exceeds a prescribed value, a limiting operation of the ACL circuit 8 is relaxed, therefore, even when amplitude of a video signal is small, a video signal display part does not become dark.

Description

Detailed Description of the Invention

[0001]

This invention has an aspect ratio of 1
The present invention relates to a television receiver having a CRT with a wide aspect ratio display surface such as 6: 9.

[0002]

2. Description of the Related Art Conventionally, when a video image produced for a 4: 3 television is projected on a television receiver having an aspect ratio of 16: 9, a video signal of The time axis is compressed, and as shown in FIG. 6A, side panel signals of uniform level as shown in FIG. 6B are inserted and displayed on both sides of the video signal display section. Hereinafter, the portions having uniform brightness levels on both sides will be referred to as side panel portions. The brightness of the side panel portion is usually configured to be variable by the controller according to the preference of the user.

FIG. 7 is a diagram showing an auto contrast limiter circuit (hereinafter referred to as "ACL circuit") of a CRT.
Reference numeral 1 is a CRT, 2 is a high-voltage rectifying diode, 3 is a flyback transformer, and the high-voltage rectifying diode 2 and a flyback transformer 3 constitute a high-voltage generating circuit. The flyback transformer 3 boosts a horizontal retrace pulse and boosts it. The horizontal pulse is rectified by the high-voltage rectifying diode 2 and the capacitance of the CRT 1 to generate a high voltage that causes a beam current to flow through the CRT 1.

Reference numeral 4 is a beam current limiting resistor, 5 is a diode for detecting a beam current, 6 is a resistor for determining an amplification factor, 7 is a variable resistor for determining the amplification factor, and the cathode side of the diode 5 is a flyback transformer 3. At the connection point A of the resistor 4,
The anode side is connected to a connection point B between the resistor 6 and the variable resistor 7 to form an ACL circuit 8, and an amplification factor control voltage that determines the amplification factor of the signal amplification circuit 9 is generated at the point B. The amplification factor of the video signal amplifier circuit 9 changes according to the moving average value of the amplification factor control voltage for several frames. The amplification factor decreases when the amplification factor control voltage decreases, and the amplification factor increases when the amplification factor control voltage increases. There is.

Reference numeral 10 is a video signal output circuit for driving the CRT 1 with the video signal inputted from the video signal amplifier circuit 9, and 11 is a time axis of the video signal having an aspect ratio of 4: 3, compressed on both sides as shown in FIG. A video signal time axis compression circuit for inserting the side panel signal shown in b) is a controller for controlling the video signal time axis compression circuit 11 by a user's operation to control the brightness of the side panel portion.

Next, the operation will be described. The video signal amplifier circuit 9 amplifies the video signal input from the video signal time base compression circuit 11 with an amplification factor determined by the amplification factor control voltage input from the ACL circuit 8, and outputs it to the video signal output circuit 10. Output. The video signal output circuit 10 drives the CRT 1 with the input video signal, and a beam current corresponding to the drive amount flows from the high voltage generation circuit to the video signal output circuit 10 via the CRT 1 to display an image on the display surface of the CRT 1. It is projected.

The operation of the ACL circuit 8 is such that when a video signal having a large amplitude is input, the beam current amount increases, so that the voltage at the point A determined by the beam current amount drops, and the voltage at the point A becomes lower than the voltage at the point B. Then, the beam current detecting diode 5 is turned on, and thereafter the video signal amplifier circuit 9 is driven by the voltage at the point A.
The amplification factor of is determined. After that, as the beam current increases, A
Since the voltage at the point drops, the increase rate of the amplitude of the video signal output from the video signal amplifier circuit 9 decreases, the increase rate of the drive amount of the CRT 1 of the video signal output circuit 10 decreases, and the increase rate of the beam current decreases. Limit to be

[0008]

In the conventional television receiver, when the user operates the controller to set the brightness of the side panel portion to a high level, an image is output from the ACL circuit by the amount of increase in the beam current amount of the side panel portion. The amplification factor control voltage input to the signal amplification circuit increases, the amplification factor increases, and the beam current increases. Therefore, when the average luminance of the video signal becomes lower than the luminance of the side panel portion, the luminance of the side panel portion determines the amplification factor of the video signal amplifier circuit, and the luminance of the video signal display portion becomes greater than that of the input video signal. There is a problem that the brightness becomes darker than the brightness corresponding to the amplitude.

The present invention has been made to solve the above problems, and provides a television receiver in which the brightness of the video signal display unit does not become dark even if the brightness of the side panel unit is set high. The purpose is to

[0010]

A television receiver according to the present invention includes a switching means for relaxing the beam current limitation when the brightness set in the side panel section of the ACL circuit exceeds a predetermined value. It is provided.

Further, the ACL circuit is provided with means for detecting the average luminance level of the video signal and controlling so that the luminance of the side panel portion does not exceed the detected average luminance level.

Further, the ACL circuit is provided with means for stopping the limiting operation during the display period of the side panel portion and operating only during the display period of the video signal display portion.

[0013]

According to the present invention, when the brightness of the side panel section exceeds a predetermined value, the limitation of the beam current by the ACL circuit is relaxed. Therefore, even if the brightness of the side panel section is high, the brightness of the video signal display section is reduced. It doesn't have a big influence.

Further, since the maximum value of the brightness of the side panel does not exceed the average brightness level of the video signal, the limitation of the beam current is governed by the average brightness of the video signal,
It is not affected by the brightness of the side panel.

The display period of the side panel section is ACL.
Since the limiting operation of the circuit is stopped and the circuit operates only during the display period of the video signal display section, the limitation of the beam current is controlled by the average luminance of the video signal and is not influenced by the luminance of the side panel section.

[0016]

EXAMPLES Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1, the same reference numerals as those in FIG. 7 denote the same parts, 13 is a beam current limitation relaxation resistance, 14 is a beam current limitation relaxation transistor, and 15 is a beam current limitation relaxation transistor.
Is a controller that controls the video signal time base compression circuit 11 to make the brightness of the side panel section variable, and when the brightness of the side panel section is set to a brightness equal to or higher than a predetermined value, a beam current limitation relaxing transistor is provided. A signal for setting the base of 14 to "H" is transmitted.

Next, the operation of the first embodiment will be described with reference to the flowchart of FIG. For the same parts as the prior art,
The description of the operation is omitted. If the user operates the controller 15 to increase the brightness of the side panel section in step 1, the controller 15 writes the brightness value B of the side panel section set in step 2 to the address B,
In step 3, the brightness value C set in advance is compared.

This preset brightness value C
Is a video amplifier circuit 9, a video output circuit 10 and a CRT 1.
Even if the amplification factor of the video signal amplification circuit 9 is determined by the fixed value of the beam current limiting resistor 4 and the voltage drop value due to the beam current, the brightness of the video signal display unit is determined by the brightness value determined based on the characteristics of The brightness value is set within a range that is not so noticeable as compared with the brightness of the side panel portion.

In step 3, if the B value is smaller than the C value, the process proceeds to step 4, and the base of the beam current limit relaxation transistor 14 is "L", which is in the off state.
The voltage at the point is a constant voltage determined by the values of the resistor 6 and the variable resistor 7, and the amplification factor of the video signal amplifier circuit 9 is constant. After that, the process proceeds to step 6 to control the video signal time base compression circuit 11 to set the brightness of the side panel portion to the value B.

If the B value is larger than the C value in step 3, the process proceeds to step 5, the base of the beam current limitation relaxation transistor 14 becomes "H", and the beam current limitation relaxation transistor 14 is turned on. , The resistance value between the power source and point A is the parallel value of the beam current limiting resistor 4 and the beam current limiting relaxation resistor 13, and the voltage at point A is the amount of beam current flowing through CRT1 and the impedance between the power source and point A. Determined by.

Next, in step 6, the controller 15 sets the brightness of the side panel portion to the B value. This increases the beam current amount, but the impedance between the point A and the power supply is a parallel value of the beam current limiting resistance 4 and the beam current limiting relaxation resistance 13, and is lower than when the transistor 14 is in the OFF state. Even if the beam current amount increases, the voltage at the point A decreases less, and the amplification factor of the video signal amplifier circuit 9 decreases less. Therefore, when the brightness of the side panel portion is increased, the conventional problem that the brightness of the video signal becomes dark is solved. This is because the beam current limit is
This is mainly because the image signal is used and the influence of the brightness of the side panel portion is reduced.

The impedance between point A and the power supply is
Always beam current limiting resistor 4 and beam current limiting relaxation resistor 1
If 3 is set to the impedance connected in parallel, CR will be set when the brightness of the side panel is set to dark.
The amount of beam current of the video signal display portion on the display surface of T1 increases, which causes a problem that the luminance of the video signal display portion deteriorates.

However, in the first embodiment, only when the brightness value B of the side panel portion is set to a value larger than the brightness value C determined from the characteristics such as CRT, that is, the B value>
Since the impedance between the point A and the power source is lowered only when the value is C, the above problem does not occur.

Example 2. Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block circuit diagram of the second embodiment, and the same reference numerals as those in FIG. 1 denote the same parts,
Reference numeral 16 is an average luminance level detection circuit of the video signal, and 17 is a controller, which receives the output of the average luminance level detection circuit 16 and controls the luminance of the side panel portion.

Next, the operation of the second embodiment will be described with reference to the flowchart of FIG. Average brightness level detection circuit 16
Outputs the average brightness level of the detected video signal to the controller 17. The controller 17 reads the average brightness level (hereinafter, referred to as “D value”) of the video signal detected by the average brightness level detection circuit 16 into the address D in step 11, and displays the average brightness level of the side panel section set by the user in step 12. The brightness (hereinafter referred to as “F value”) is read into the address F.

Next, in step 13, the D value and the preset value E are compared. The E value is a set luminance value of the side panel and is a value preset according to the characteristics of the CRT 1, the video output circuit 10 and the video amplification circuit 9. For example, the video signal display unit is black and the beam is The voltage at the point A is a brightness value at which the transistor 5 is not turned on when the current is only in the side panel portion.
In other words, even if the brightness of the side panel portion is set to the E value, the effect of limiting the beam current due to the brightness of the side panel portion can be ignored.

Next, if the result of the comparison in step 13 is D value <E value, the process proceeds to step 14 to compare the E value and the F value, and if F value> E value, the process proceeds to step 15. To set the brightness of the side panel to E value. At this time, even if the brightness of the side panel section becomes brighter than the brightness of the video signal display section, the E value is determined as described above, and therefore the beam current limiting operation of the ACL circuit 8 is not affected.

If F value <E value in step 14, the process proceeds to step 17, and the brightness of the side panel is set to the F value set by the user. Also at this time, since the F value <E value, the beam current limiting operation of the ACL circuit 8 is not affected.

If D value> E value in step 13, the process proceeds to step 16, the F value and the D value are compared, and if D value> F value, the process proceeds to step 17 to determine the brightness of the side panel portion. Is set to the F value. At this time, since the brightness of the side panel section is lower than the brightness of the video signal display section, the beam current is limited by the video signal, and the brightness of the side signal section does not make the brightness of the video signal display section dark.

If D value <F value in step 16, the process proceeds to step 18 and the D value is set as the brightness of the side panel portion. At this time, since the brightness of the side panel section is at the same level as that of the video signal display section, only the video signal display section does not become dark.

Example 3. Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block circuit diagram of the third embodiment, and the same reference numerals as those in FIG. 1 denote the same parts,
Reference numeral 18 denotes a beam current limiting connection transistor, and an inverted output signal of the side panel signal as shown in FIG. 6C is input from the video signal time base compression circuit 11 to the base of the transistor 18.

Next, the operation of the third embodiment will be described. The description of the operation of the same parts as those of the conventional art will be omitted. The base of the beam current limiting connection transistor 18 is shown in FIG.
Since the inverted output signal of the side panel signal as shown in (c) is applied, the beam current limiting connection transistor 18 is turned off during the display period of the side panel portion.
The constant voltage at point B is applied to the video signal amplifier circuit 9. The beam current limiting connection transistor 18 is turned on during the display period of the video signal display section, and when the voltage at the point B exceeds the voltage at the point A, the diode 5 is turned on, and the beam current limiting connection is the same as in the conventional example. Is done. Therefore, the beam current is limited only by the video signal brightness, and the brightness of the video signal display unit is not changed by the brightness of the side panel unit.

[0033]

According to the present invention, when the brightness of the side panel portion exceeds a predetermined value, the effect of limiting the beam current by the ACL circuit is relaxed, so that the brightness of the side panel portion is higher than the average luminance of the video signal. However, the brightness of the video signal display portion is hardly affected.

Further, since the brightness of the side panel portion does not exceed the average brightness of the video signal display portion, the limitation of the beam current is mainly determined by the average brightness of the video signal,
It is not affected by the brightness of the side panel.

The display period of the side panel is AC
Since the beam current limiting operation of the L circuit is stopped and the L signal is operated only during the display period of the video signal display section, the limitation of the beam current is considered only by the average luminance of the video signal and is not influenced by the luminance of the side panel section.

From the above, the image display quality is maintained while the brightness of the side panel portion can be adjusted, and the CRT is
It also has a good effect on itself. That is, even if the brightness of the side panel section is increased, the beam current is properly limited to the video signal, so that the brightness of the video signal display section does not become dark and the video display quality is maintained.

Further, as a result, there is an effect that a television receiver in which the difference in the degree of deterioration in the luminance of the CRT caused by the difference in luminance between the side panel portion and the video signal display portion, that is, the central portion of the CRT and both sides is small can be obtained.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an auto contrast limiter (ACL) circuit according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a first embodiment.

FIG. 3 is a block circuit diagram of an ACL circuit according to a second embodiment of the present invention.

FIG. 4 is a flowchart of a second embodiment.

FIG. 5 is a block circuit diagram of an ACL circuit according to a third embodiment of the present invention.

FIG. 6 is a waveform diagram of a side panel type display surface displaying a 4: 3 image on a 16: 9 display surface, a side panel signal and its inverted signal.

FIG. 7 is a block circuit diagram of a conventional ACL circuit.

[Explanation of symbols]

 1 CRT 2 High-voltage rectification diode 3 Flyback transformer 4 Beam current limiting resistor 5 Beam current detection diode 6 Resistor for amplification factor determination 7 Variable resistor for amplification factor determination 8 Auto contrast limiter (ACL) circuit 9 Video signal amplification circuit 11 Video Signal time axis compression circuit 13 Beam current relaxation resistance 14 Beam current limitation relaxation transistor 15 Controller 16 Average brightness level detection circuit 17 Controller 18 Beam current limitation connection transistor

Claims (3)

[Claims] 1. A side panel unit having an adjustable brightness level is projected on the side of a video signal display unit which is obtained by compressing and displaying a time axis of a video signal having a small aspect ratio on a display surface having a wide aspect ratio of a CRT. And including an auto-contrast limiter (ACL) circuit that limits the beam current of the CRT when the amplitude of the input video signal exceeds a predetermined value. Is set to exceed a predetermined value, switching means is provided so as to relax the limitation of the beam current. 2. A side panel section having an adjustable brightness level is projected on the side of a video signal display section in which a time axis of a video signal having a small aspect ratio is compressed and displayed on a wide aspect ratio display surface of a CRT. And an ACL circuit for limiting the beam current of the CRT when the amplitude of the input video signal exceeds a predetermined value.
A television receiver characterized in that the CL circuit is provided with means for controlling the luminance of the side panel portion so as not to exceed the average luminance level of the input video signal. 3. A side panel unit having an adjustable brightness level is displayed on the side of a video signal display unit in which a video signal having a small aspect ratio is compressed and displayed on a display surface having a wide aspect ratio of a CRT. And an ACL circuit for limiting the beam current of the CRT when the amplitude of the input video signal exceeds a predetermined value.
The display period of the side panel section in the CL circuit is the ACL
A television receiver comprising means for stopping the limiting operation of the circuit and operating the video signal display section only during the display period.