JPH0564027A - Television receiver - Google Patents

Abstract

PURPOSE:To display a video image with marginal parts at the upper and the lower parts of a screen by expanding it in a vertical direction, and simultaneously, to display the superimposed title of this marginal part by compressing it in the vertical direction. CONSTITUTION:A deflection processing circuit 1 outputs the PWM wave of a vertical period to a saw-tooth wave generation circuit 2. The saw-tooth wave generation circuit 2 generates the saw-tooth wave of inclination based on the PWM wave. On the other hand, a gate pulse generation circuit 14 generates a gate pulse at the front part and the rear part of vertical scanning, and the charging current of the capacitor C3 of the saw-tooth wave generation circuit 2 is reduced by this gate pulse. Thus, the inclination of the saw-tooth wave from the saw-tooth wave generation circuit 2 is made small during this period. This saw-tooth wave is supplied to a vertical output part 12, and the vertical amplitude of the upper and the lower edges of the screen is compressed by the vertical output part 12.

Description

Detailed Description of the Invention

[Object of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver, and more particularly to a television receiver suitable for displaying an NTSC broadcast image on a screen having a wide aspect ratio.

[0002]

2. Description of the Related Art Currently, NTSC television broadcasting is being carried out in Japan, and high-definition television broadcasting with a large screen and high definition is about to be started. In this high-definition television broadcast, NTS
The aspect ratio of the screen is different from that of C system, and the current NT
A picture tube having an aspect ratio (16: 9) wider than that of the SC television receiver is adopted. It is also conceivable that the high-definition television broadcast is down-converted to the current NTSC system and the high-definition television broadcast is auditioned by the NTSC system television receiver. Even in this case, a wide aspect picture tube having an aspect ratio of 16: 9 may be used in order not to lose image information in the entire screen.

In this wide aspect picture tube, when a high-definition television picture is down-converted and auditioned, the aspect ratio of the picture matches the aspect ratio of the picture tube, so that no discomfort occurs. However, the current NTS
Since the aspect ratio of the C method is 4: 3, when displaying an NTSC broadcast, it is not possible to display all NTSC images on the entire screen without distortion.

FIG. 4 is an explanatory view for explaining a display when an image having an aspect ratio of 4: 3 is displayed on a wide aspect picture tube having an aspect ratio of 16: 9.

FIG. 4A shows a difference between a screen having an aspect ratio of 4: 3 and a screen having an aspect ratio of 16: 9. FIG. 4B shows a display mode (hereinafter referred to as a first display mode) in which the horizontal time axis of the NTSC signal is compressed and displayed on the center of the wide aspect picture tube. In this case, frame images (hatched portions) of a predetermined gray level are displayed on the left and right of the wide aspect picture tube.

If this frame image is uncomfortable, N
It is also possible to adopt a display mode (hereinafter referred to as a second display mode) in which the vertical amplitude of a TSC image is expanded and displayed in the entire wide aspect picture tube. In the second display mode, the vertical amplitude of the image is increased.

FIG. 5 is a circuit diagram showing a vertical deflection circuit employed in a conventional television receiver capable of displaying in the second display mode, and FIG. 6 is a timing chart for explaining its operation. Is.

The deflection processing circuit 1 supplies a sawtooth wave generation circuit 2 with a PWM wave whose pulse width changes in a vertical cycle. This P
The sawtooth wave generation circuit 2 based on the WM wave is shown in FIG.
A sawtooth wave having a vertical cycle shown in is generated and supplied to the positive input terminal of the differential amplifier 3. The output of the differential amplifier 3 is inverted by the inverting amplifier 4, and the output end of the inverting amplifier 4 is connected to the reference potential point via the coupling capacitor C1, the vertical deflection coil L1 and the current feedback resistor R3. It The output terminal of the inverting amplifier 4 is also connected to the reference potential point via the resistors R1 and R2. The connection point between the resistors R1 and R2 is connected to the connection point between the vertical deflection coil L1 and the resistor R3 via the capacitor C2, and is also connected to the negative input terminal of the differential amplifier 3.

Voltage feedback is performed at the negative input terminal of the differential amplifier 3 as described later, and a pulsed voltage waveform shown in FIG. 6C appears at the output terminal of the differential amplifier 3. The inverting amplifier 4 inverts and amplifies this pulse voltage, and then, as shown in FIG.
The pulsed voltage shown in is output. This voltage is supplied to the vertical deflection coil L1 via the coupling capacitor C1. The vertical deflection coil L1 is almost composed of an inductance component, and when a pulsed voltage is applied, a sawtooth wave current having a vertical cycle flows. As a result, a picture tube not shown is deflected.

A sawtooth wave current also flows through the current feedback resistor R3, and a sawtooth wave voltage shown in FIG. 6B appears at both ends of the current feedback resistor R3. The coupling capacitor C1 blocks the direct current component of the output of the inverting amplifier 4, and the direct current voltage at the connection point of the voltage feedback resistors R1 and R2 is added to the sawtooth voltage across the current feedback resistor R3. It is fed back to the negative input terminal of. Thus, the differential amplifier 3 is subjected to current feedback and voltage feedback, the deflection coil current resembles a sawtooth wave supplied to the plus input terminal, and the operating potential of the inverting amplifier 4 is stable. ..

By changing the amplitude of the sawtooth wave voltage from the sawtooth wave generation circuit 2, the vertical amplitude of the screen can be adjusted and an image can be displayed in the second display mode. As shown in FIG. 4 (c), when the NTSC image matches the screen shape of the wide aspect picture tube, by adopting the second display mode, the image is widened over the entire display screen. Can be displayed. For example, it is effective in displaying a wide aspect image having margins at the top and bottom of the screen, such as when converting a movie image into an NTSC signal.

By the way, when a Western picture is converted into an NTSC signal, as shown in FIG. 4D, a subtitle supermarket 61 is often added to the lower margin of the screen. However, in the second display mode, since the vertical amplitude of the image is increased, the upper and lower margins of the NTSC screen are lost from the screen as shown by the broken line in FIG. 4 (d). .. That is, the subtitle supermarket 61 has a drawback that it is not displayed because it is missing from the screen.

[0013]

As described above, in the above-described conventional television receiver, in the second display mode, the top and bottom of the video may be missing, and the subtitle supermarket or the like may not be displayed. There was a problem.

The present invention has been made in view of the above problems, and provides a television receiver capable of compressing and displaying the margin portions of a video signal having margins above and below the image at the upper and lower ends of the screen. The purpose is to provide.

[Constitution of the Invention]

SUMMARY OF THE INVENTION A television receiver according to the present invention comprises a deflection processing circuit for generating a first pulse of a vertical cycle, and a tilt based on the first pulse supplied with the deflection processing circuit. A sawtooth wave generating circuit for generating a sawtooth wave signal, a pulse generating circuit for outputting a second pulse at a timing corresponding to an end of vertical scanning, and a sawtooth wave generating circuit for the second pulse. And a control means for controlling the vertical amplitude of the upper and lower ends of the screen.

[0016]

In the present invention, the sawtooth wave generation circuit generates the sawtooth wave signal based on the first pulse of the vertical period from the deflection processing circuit. The pulse generation circuit generates the second pulse at a timing corresponding to the end of the vertical scanning, and the control means controls the inclination of the sawtooth wave of the sawtooth wave generation circuit by the second pulse. As a result, the amplitude of the upper and lower ends of the screen can be compressed compared to other parts, and for example, the blank part of the video signal can be compressed and displayed at a predetermined position on the display screen.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a television receiver according to the present invention. In FIG. 1, the same parts as those in FIG. 5 are designated by the same reference numerals.

The deflection processing circuit 1 generates a PWM wave whose pulse width changes in a vertical cycle. The output terminal of the deflection processing circuit 1 is connected to the base of the transistor Q1 via the resistors R4 and R5 forming the sawtooth wave generating circuit 2. The emitter of the transistor Q1 is connected to the power supply terminal 11 via the resistor R6, and the collector is connected to the reference potential point. A capacitor C3 is connected between the base of the transistor Q1 and the reference potential point. PW is used for the emitter of transistor Q1
A sawtooth voltage based on the M wave is generated and supplied to the vertical output section 12. The vertical output unit 12 is shown in FIG.
It has the same structure as the part surrounded by the broken line of FIG. 2 and is adapted to flow a sawtooth wave current based on the input sawtooth wave voltage to a vertical deflection coil (not shown) to deflect a picture tube (not shown).

In this embodiment, the connection point of the resistors R4 and R5 is connected to the reference potential point via the emitter / collector path of the transistor Q2. A series circuit of a resistor R7, a diode D and resistors R8 and R9 is connected between the power supply terminal 13 and the reference potential point, and the base of the transistor Q2 is connected to the node of the diode D and the resistor R8. The connection point between resistors R8 and R9 is the collector of transistor Q3.
It is connected to the reference potential point via the emitter path, and the base of the transistor Q3 is connected to the output terminal of the gate pulse generating circuit 14. The gate pulse generation circuit 14 is adapted to generate a gate pulse for changing the deflection speed in the front part and the rear part of the vertical scanning period.

Next, the operation of the television receiver thus configured will be described with reference to the timing chart of FIG. 2 and the explanatory view of FIG. 2A shows the PWM wave from the change processing circuit 1, FIG. 2B shows the gate pulse from the gate pulse generation circuit, and FIG. 2C shows the output of the sawtooth wave generation circuit 2. ing.

As shown in FIG. 3 (a), the central portion of an image having an aspect ratio of 4: 3 has a 16: 9 aspect ratio, which is a video portion, and margins (hatched portions) are provided above and below the image portion. It is assumed that the held signal is displayed on the wide aspect picture tube having the aspect ratio of 16: 9 in the second display mode in which the vertical amplitude is increased.

In the deflection processing circuit 1, as shown in FIG. 2A, the width of the positive pulse is small at the beginning of the vertical period, and gradually increases toward the end of the vertical period. Outputs a PWM wave that repeatedly changes the pulse width.
This PWM wave is given to the sawtooth wave generation circuit 2. The capacitor C3 of the sawtooth wave generation circuit 2 is charged during the positive pulse period of the PWM wave, and the transistor Q1 is charged during the vertical scanning period.
The base potential of is gradually increased. Then, the current flowing through the emitter-collector path of the transistor Q1 decreases and the emitter voltage rises. In the vertical blanking period, PWM
During the negative pulse period of the wave, the capacitor C3 is discharged, the base potential of the transistor Q1 is lowered, the emitter current is increased, and the emitter voltage is lowered. Thus, a vertical cycle sawtooth wave voltage appears at the emitter of the transistor Q1.
This sawtooth wave voltage is supplied to the vertical output section 12 to deflect a picture tube (not shown).

On the other hand, the gate pulse generating circuit 14 outputs the positive gate pulse shown in FIG. 2B at the front and rear portions of the vertical scanning period, that is, at the timings corresponding to the upper and lower portions on the screen. It This gate pulse is given to the base of the transistor Q3, and the transistor Q3 is turned on during the gate pulse period. Then, the potential at the connection point of the diode D and the resistor R8 decreases, and the current flowing through the emitter-collector path of the transistor Q2 increases.
Therefore, during this period, the charging current of the capacitor C3 decreases, and the increase amount of the emitter current of the transistor Q1 becomes smaller than that in other periods. That is, as shown in FIG. 2 (c), the emitter of the transistor Q1 has a slower slope in the front and rear portions of the vertical scanning period than in the middle portion of the vertical scanning period corresponding to the center of the screen. Sawtooth voltage is generated. The sawtooth wave voltage is applied to the vertical output section 12, and the vertical output section 12 causes a deflection coil current similar to the sawtooth wave voltage to flow in the vertical deflection coil.

That is, the inclination of the vertical deflection current becomes discontinuous at the front and rear portions of the vertical scanning period, and the deflection speed becomes slow at the portions corresponding to the upper and lower portions of the screen. That is, the range scanned by the electron beam of the picture tube is
The inclination of the deflection current becomes wider than that when it is constant, and even when the second display mode is adopted, the uppermost part and the lowermost part (margin part) of the image are compressed and displayed at the upper and lower ends of the screen.

The amplitude of the sawtooth wave voltage from the sawtooth wave generation circuit 2 is appropriately set to extend the vertical amplitude of the image of FIG. 3 (a), and the emitter current of the transistor Q2 is appropriately controlled to produce a blank area. Determine the amount of compression (shaded area). Thus, the display widths of the image portion and the blank portion can be set appropriately, and the image portion and the blank portion can be displayed in the entire area of the screen. In this way, the subtitle supermarket 63 in the blank area of FIG. 3A is displayed as the vertically compressed subtitle supermarket 64 at the lower end of the display screen, as shown in FIG. 3B.

As described above, in this embodiment, the gate pulse generating circuit 14 generates a positive pulse at the front and rear of the vertical scanning period, and the positive pulse charges the capacitor C3 of the sawtooth wave generating circuit 2. Reduce the current,
By reducing the inclination of the sawtooth wave during this period, the upper and lower ends of the image are compressed and displayed on the screen. Thus, by increasing the vertical amplitude, the portion overscanned to the lower side of the screen can be compressed and displayed at the lower end of the screen.

[0027]

As described above, according to the present invention, by increasing the vertical amplitude, the portion that is originally overscanned on the lower side of the screen can be compressed and displayed on the upper and lower ends of the screen. Thus, it is possible to display the margin portion of the video signal having the margins above and below the screen.

[Brief description of drawings]

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

FIG. 2 is a timing chart for explaining the operation of the embodiment.

FIG. 3 is an explanatory diagram for explaining the operation of the embodiment.

FIG. 4 is an explanatory diagram for explaining a display when an image having an aspect ratio of 4: 3 is displayed on a wide aspect picture tube having an aspect ratio of 16: 9.

FIG. 5 is a circuit diagram showing a vertical deflection circuit used in a conventional television receiver.

FIG. 6 is a timing chart for explaining the operation of the conventional example.

[Explanation of symbols]

 1 ... Deflection processing circuit 2 ... Sawtooth wave generation circuit 12 ... Vertical output section 14 ... Gate pulse generation circuit Q1 to Q3 ... Transistor C3 ... Capacitor

Claims (1)

[Claims] 1. A deflection processing circuit for generating a first pulse having a vertical cycle, and a sawtooth wave generation circuit which is supplied with the first pulse and generates an inclined sawtooth wave signal based on the first pulse. A pulse generating circuit that outputs a second pulse at a timing corresponding to an end of vertical scanning; and a sawtooth wave generating circuit that controls the vertical amplitude of the upper and lower end portions of the screen by the second pulse. A television receiver comprising a control means.