JPH0377519B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a large-sized video display device that displays images such as television signals by arranging a large number of light-emitting type front panels on a display panel and controlling the amount of light emitted from these display elements.

Conventionally, devices of this type using a light bulb or a cathode ray tube as a display element have been proposed.
However, those using light bulbs had problems such as low luminous efficiency, high power consumption and calorific value, and emitted light color having a reddish tinge. Those using cathode ray tubes are expensive and have the problem of being difficult to obtain a sufficient amount of light.

On the other hand, devices that display images using fluorescent lamps have also been proposed (Special Publication No. 5894-1971, Special Publication No.
However, since these lamps are powered by DC voltage, they use a resistor as a current limiting device. Therefore, there is a problem in that the current limiting device (resistor) generates a large amount of power loss and heat.

In response, the present inventors have proposed a large-sized image display device in which the display element includes a discharge lamp such as a fluorescent lamp and a high-frequency generator that energizes the discharge lamp (patent application (Sho 57-130579). Since this device can use an inductor and a capacitor as a current limiting device to light the discharge lamp at high frequency, power loss and heat generation in the current limiting device can be reduced. It is effective in that it can be made small and lightweight, and has good responsiveness to video signals.

The present invention has been made as a result of research on the above-mentioned large-scale video display device comprising a discharge lamp such as a fluorescent lamp and a high-frequency generator that energizes the discharge lamp. It was found that the light output of the device was not constant. The reason for this is that when a discharge lamp is dimmed in accordance with a video signal, the lamp current of the discharge lamp differs depending on from which point in the high-frequency output voltage waveform the high-frequency output voltage is applied to the discharge lamp. Particularly when a discharge lamp is deeply dimmed, the lamp current fluctuates significantly. That is, as shown in FIG. 1b, for example, in the case of A where the voltage is applied from the zero phase and the case of B where the voltage is applied from the 3/2π phase, there is a phase shift of the current with respect to the voltage and the application of the restriking voltage. Since the phases are different, the lamp current (effective value) will be different as shown in FIG. 1c. The phase shift mentioned above is due to the use of an inductor as a current limiting device (in the case of a capacitor, the current will lead), and the point of re-ignition is when the discharge lamp is turned off once the lamp current reaches zero, and when the lamp current reaches a predetermined level or higher. This is because it does not restart until a voltage (re-ignition voltage) is applied. Note that FIG. 1a shows the supply time of high-frequency voltage to the discharge lamp determined according to the video signal.

Therefore, the present invention provides a large-sized discharge lamp that can obtain stable light output even when the discharge lamp is dimmed deeply, in a discharge lamp such as a fluorescent lamp and a high-frequency generator that energizes the discharge lamp. The purpose of this invention is to provide a video display device.

The present invention was made by focusing on the fact that the light output of a discharge lamp fluctuates due to differences in the first and last half cycles of a high-frequency voltage applied to a discharge lamp for a predetermined period according to a video signal. The aim is to reduce the proportion of these first and last half cycles in the total high frequency voltage applied to the discharge lamp.

In the present invention, when the scanning frequency of the video signal is f _f and the number of dimming stages for dimming the discharge lamp according to the video signal is n, the output frequency fo of the high frequency generator is
It is characterized by being set to 10.f _f.n.

By setting the output frequency of the high-frequency generator as described above, a minimum of 10 cycles of high-frequency voltage will be supplied to the discharge lamp even during the deepest dimming of the dimming stage, and the high-frequency voltage will be supplied to the discharge lamp. The sum of the first and last half cycles of the high-frequency voltage can be reduced to less than 1/10 of the total, making it possible to stabilize the optical output. At 1/10 or more, fluctuations in optical output become virtually negligible.

It is also possible to continuously dim the discharge lamp according to the video signal, but in this case, the
It is not necessary to continuously dim the light to 100%, but considering the level that can be seen by humans, for example, turn off the light by 5% or more.
The deepest level of dimming can be determined, such as 100%, lights out, and 1% to 100%. In the present invention, in such a case, the output frequency of the high frequency generator is determined by setting the number of dimming steps to 20 or 100 from the deepest dimming level, for example, 5% or 1%.

Furthermore, in the present invention, the video signal is a continuous electrical signal obtained by scanning an image, such as a television signal or a movie signal. The scanning frequency of the video signal indicates how many images are transmitted per second.

Further, in the present invention, the high-frequency generator may be provided in one-to-one correspondence with the discharge lamps, or one high-frequency generator may be provided for two or more discharge lamps. Such a high frequency generator can be constructed using a thyristor inverter, a transistor inverter, or the like.

Furthermore, in the present invention, a fluorescent lamp or a neon tube can be used as the discharge lamp.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 5. Reference numerals 1 ₁ to 1n are discharge lamps, such as fluorescent lamps, which are arranged in large numbers on the display panel 2 . The display panel 2 is installed, for example, in a stadium such as a baseball field, and has several thousand or more of the discharge lamps 1 ₁ to 1n arranged therein. 3 ₁ to 3n are high frequency generators. In this embodiment, these high frequency generators 3 ₁ to 3n and the recording counter lamps 1 ₁ to 1n are in one-to-one correspondence. discharge lamp 1 ₁
and the high frequency generator ₃₁ are shown in FIG. The other discharge lamps ₁₂ to 1n and high frequency generators ₃₂ to 3n are also similar to those shown in FIG. The high frequency generator ₃₁ in this embodiment has a push-pull type transistor inverter, converts the output of a DC power source 4 such as a power source or battery obtained by rectifying a commercial power supply voltage into a high frequency AC voltage, and generates a high frequency AC voltage. The output is passed through the current limiting device 5 to the discharge lamp 1
₁ . Further, the structure is such that the filament of the discharge lamp ₁₁ can be preheated at all times.
Since the circuit configurations of the high frequency generators 3 ₁ to 3n in this embodiment are well known, their explanations will be omitted. Further, the output frequencies of the high frequency generators 3 ₁ to 3n will be described later. A video signal generator 6 generates a video signal to be displayed on the display panel 2. The video signal generating device 6 may be one for generating video signals such as television signals, video signals, movie signals, etc., but this embodiment shows the case of a black and white television signal. That is,
The video signal generator 6 of this embodiment includes a radio frequency amplifier 7 for amplifying the signal from the antenna A, a video detector 8, and a video amplifier 9. Such a video display device 6 is well known. be. Reference numeral 10 denotes a control device that controls the amount of light emitted by the discharge lamps 1 ₁ to 1n in accordance with the video signal from the video display device 6 (the television signal in this embodiment is 60 Hz in Japan), and displays the video on the display panel 2. In other words, the light output of the discharge lamps 1 ₁ to 1n is controlled according to the white to black luminance indicated by the video signal, and
The dimming levels are, for example, 8 levels, 16 levels, and 32 levels. In this embodiment, the control device 10 includes a synchronization circuit 11 that obtains a synchronization signal from the video amplifier 9 of the video signal generation device 6, and is controlled by this synchronization circuit 11 to set the addresses of the discharge lamps 1 ₁ to 1n. An address setter 12, an A/D converter 13 that converts the video signal from the video signal generator 5 into a digital signal, and an A/D converter 13 that is provided corresponding to the discharge lamps ₁₁ to 1n and selected by the address setter 12. signal generators 14 ₁ to 14n that output signals that determine the lighting time of the discharge lamps 1 ₁ to 1n according to the output of the A/D converter 13 _;
A switch device 1 that controls the high frequency voltage supply to the discharge lamps 1 ₁ to 1n according to the outputs of the discharge lamps 1 1 to 1n.
5 ₁ to 15n. Each component of such a control device 10 is well known. Note that in this embodiment, the switch device 15 ₁
15n is composed of a diode bridge 16 ₁ and a transistor 17 ₁ as illustrated in FIG. 4, and is inserted between the discharge lamp 1 ₁ and the current limiting device 5 ₁ .

The control device 10 and the video signal generating device 6 as described above are housed in or attached to the display panel 1, or provided in a separate operation room (not shown), as appropriate.

Next, the high frequency generator 3 ₁ -
The output frequency fo of 3n is set as follows. That is, the scanning frequency of the video signal is 60Hz as described above. Then, when the number of dimming steps is set to 8 steps, the output frequency fo is 10×60×8 to 4.8kHz.
The settings above are as follows. Also, the number of dimming stages
When set to 16, the output frequency fo is set to 9.6kHz or higher.

Next, the effect will be explained. The signal generators 14 ₁ to 14n in the control device 10 are address setters 12
According to the output of the A/D converter 13, a signal is output that determines the lighting time of the discharge lamps ₁₁ to 1n, as shown in FIG. 5a. Switch device 15 ₁ ~
15n outputs the discharge lamps 1 1 to 14n as shown in FIG. _5b in response to signals from the signal generators 14 ₁ to 14n.
Controls the supply of high frequency voltage to 1n. That is, when the brightness of the video signal is high, the high-frequency voltage supply time to the discharge lamps 1 ₁ to 1n is lengthened to increase the light output and bring it closer to white, and when the brightness is low, the light output is decreased. This makes the color closer to black. In this manner, one cycle of the video signal ends, and in the next cycle, the above-described operation is repeated and the television video is displayed on the electronic display board 1.

For discharge lamps 1 ₁ to 1n, 10 even at the deepest dimming.
Since a voltage exceeding the cycle is supplied, changes in the phase of the high frequency voltage supplied due to differences in dimming intensity,
Alternatively, even if there is a phase shift in the high frequency voltage supplied to the discharge lamps ₁₁ to 1n, the sum of the first and final half cycles is 10% of the total voltage, as shown in Figure 5b.
% or less, the light output of the discharge lamps 1 ₁ to 1n can be stabilized. Therefore, it is possible to display high quality images.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications are possible. For example, the present invention can also be applied to color display. in this case,
The control device and the like can be configured using well-known devices.

As detailed above, the present invention uses a discharge lamp as a display element and specifies the output frequency of the high frequency generator that energizes the discharge lamp based on the relationship between the scanning output wave number of the video signal and the dimming stage. Even when the phase of the voltage supplied to the discharge lamp is not constant, such as during the deepest dimming, it is possible to reduce changes in the light output and provide high-quality video display.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the operation of the device that is the premise of the present invention, FIG. 2 is a front view showing an embodiment of the present invention, FIG. 3 is a block diagram showing the system configuration of the same embodiment, and FIG. The figure is a circuit diagram showing a high frequency generator in the same embodiment, and FIG. 5 is a waveform diagram showing the operation of the same embodiment. 1 ₁ ~ 1n...discharge lamp, 2...display panel, 3 ₁ ~ 3
n... High frequency generator, 6... Video signal generator, 10... Control device.

Claims (1)

[Scope of Claims] 1. A large number of discharge lamps arranged on a display panel, a high frequency generator for energizing the discharge lamps, a video signal generator, and the above-mentioned method for each of the discharge lamps according to the video signal. a control device that controls an output supply period of the high frequency generator and displays it on the display panel; the high frequency generator has an output frequency fo, the scanning frequency of the video signal is f _f , and the control device dims. A large-sized video display device characterized in that when the number of stages is n, it is set to fo10.f _f.n. 2. The large-sized image display device according to claim 1, wherein a plurality of the high-frequency generators are provided in one-to-one correspondence with the discharge lamps. 3. Claim 1 or 2, wherein the high-frequency generator includes a rectifier that rectifies a commercial AC power supply voltage, and an inverter that converts the output of the rectifier into a high-frequency AC voltage. The large-sized video display device described. 4. The large-sized video display according to any one of claims 1 to 3, wherein the video signal generating device generates a video signal of one of a television signal, a video signal, and a movie signal. Device.