JPH0311596A - Dc discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To lower the least brightness of a display and to improve the display contrast rate by providing a minute display control device to ON-control a minute display circuit only for a specific time before the starting of the brightness control. CONSTITUTION:The brightness control is carried out by inputting a brightness data output simultaneously with a scanning signal Vc from a display control circuit 10, and using the output of a PWM circuit 11 to control the time width. And a minute display control device is composed of timers 20 and 21, a high voltage switch circuit 22, and the like. When the scanning signal Vc is output, a delay time T1 is produced by the timer 20, and a delay time T2 is produced by the timer 21 immediately after the delay time T1. During the delay time T2, the switch element 22a of a high voltage switch circuit 22 is turned on, and a lamp 1 is to carry out a minute discharge through a resistance 4. As a result, the brightness level in a black time when the main discharge current does not flow is to be reduced, and the contrast rate is improved extensively.

Description

[Detailed description of the invention] [Production Ytζ)) Utilization: 1 The present invention provides a direct current discharge lamp, which is a display element of a large video display device used in stadiums, baseball fields, etc. This invention relates to a DC discharge lamp lighting device for lighting.

``Prior Art'' A display device using a direct current discharge lamp as a display element for obtaining an A contrast has been developed. For outdoor use, use under strong external light.
By increasing the maximum brightness, you can achieve a high contrast ratio of 1
I can only say one thing. However, when used in the evening or at night,
Maximum brightness of Mafuj ~ Sagara during daytime 1/2-, i
, '3/', and in this case, the contrast is not the maximum brightness but the minimum brightness level (black level) that is important.

Conventional methods for displaying images and controlling brightness gradation employ so-called time width control, which controls the time width of a lamp current (main discharge current) at a nearly constant DC level that is effective for brightness control1. In addition, in order to improve display responsiveness, a slight discharge current is passed through a bypass circuit different from the main discharge current in the display lamp (l) after the power is turned on, so that the display lamp is always lit faintly. FIG. 6 shows such a conventional lighting device.7 In FIG. 6, the filaments 1 to 2 of the DC discharge lamp 1 are
P) A DC power supply Ea is connected to one end of the filament 2 and the anode 3 via a current limiting resistor 4 to form a slight discharge circuit, and a DC power supply E l:+ is connected to the other end of the filament 2 and the anode 3. , a current-limiting resistor 5, a switch element 6, and a diode 0g) are connected in series to form a main discharge circuit. The DC power source Et) is composed of a first DC power source E l:) +, a switch element 7, a second DC power source E l:+ 2, and a bypass diode 8. Furthermore, the filaments 1 and 2 are heated by DC power supplies F and f.

In the second circuit, a DC power source F, 21 causes a slight discharge current to constantly flow through the lamp 1, and while the switch element 6.7 is on, a resistor 5 is applied in addition to the above slight discharge current. The main discharge current flows through the ramp amount.
)It has become. Note that the switch element 7 is set to be shorter than the on time of the switch element 0, and the DC power source E
The main discharge starting voltage is obtained by applying a force of 1.:1 to h.

(-1) Since the lamp main discharge current is time width controlled in the lighting device shown in Figure 6 of 2, during lamp dimming (brightness gradation control), a lamp current stall time occurs; , the lamp is scanned in the image.

This is done in order to avoid a start-up delay time occurring when starting up (discharge destruction) and deterioration of display responsiveness. This eliminates the need to start the lamp at a high voltage for each scan, resulting in better display responsiveness5.
Furthermore, since there is no startup delay, the linearity of gradation control is maintained even at low luminance, and as a result, excellent display performance can be obtained.

However, passing a slight discharge current through the lamp 1 so that it is always dimly lit has the disadvantage that the minimum brightness becomes relatively high. For this reason, when the surroundings are dark and the maximum brightness is lowered, such as at night or in the evening, the last performance of the controller 1 becomes worse. or,
It becomes impossible to use it in a pitch-dark room, such as during an indoor event, and it is difficult to expect an improvement effect.

2) Conventional lighting devices can also be used as display devices (with limited space for installation).

- Is it possible to solve this problem by making the slight discharge current that is constantly flowing even smaller?I have to experiment to find out that there is a limit for the following reasons.

In other words, when controlling the time width of the main discharge current of the lamp,
It was determined that immediately after the lamp main discharge current was turned off, a pulse-like voltage higher than the supply voltage of the main discharge current was generated in the slight discharge lamp voltage.

This pulsed voltage is shown in FIG. 7, and is generated every time the lamp current is controlled in time width. , - pulse-like voltage becomes high especially at low temperatures, and it is also known that it has temperature characteristics such that it becomes high at temperatures below 0°C.

The height of the second pulsed voltage is determined by the lamp temperature, main discharge current, slight discharge current, or other secondary factors. Regardless of the characteristics, such as the shape of the discharge lamp, the type of internal gas, the pressure, etc., the origin of this pulsed voltage is thought to be the vibration of the discharge phenomenon of the lamp anode. There is.

If this pulsed voltage reaches the power supply voltage of the slight discharge current, the lamp will go out because it will not be possible to maintain the lighting state with a slight discharge. Unless a starting voltage is applied, it is not possible to control the brightness or even light the light with a slight discharge.

Therefore, a power source for a slight discharge that flows a slight discharge current cannot control brightness unless the two main discharge currents are applied with a voltage equal to or greater than the pulsed voltage immediately after being turned off. By the way, since this pulsed voltage has the above-mentioned variation factors, it is impossible to reduce the micro-discharge power supply voltage because the micro-discharge current is lowered under the conditions of the factor that causes this variation to be maximum. On the other hand, increasing the power supply voltage is also an option, but this is not possible because the loss in the current limiting resistor will increase.

Also, if you simply reduce the current while leaving the slight discharge power supply voltage as it is, the lamp voltage when lighting a slight discharge will increase,
Eventually, it became impossible to maintain the lighting, and the second step was to increase the power supply voltage, causing a slight discharge current.

In the method shown in -, where a slight discharge current is constantly passed through the bypass of the main discharge current, the slight discharge is turned on, and the time width of the main discharge current is controlled every time the lamp is scanned, the power supply voltage for the slight discharge is determined by the power supply voltage or the surrounding environment. Therefore, it was impossible to lower the brightness during slight discharge lighting.

1. Problems to be Solved by the Invention 61: Problems to be Solved by the Invention The present invention cJ has been provided in view of the above points,
By applying a starting pulse to start discharge each time the lamp is scanned, instead of using a method of constant slight discharge, the display responsiveness due to the delay time in starting discharge of the lamp, which was a concern in the past, can be reduced. The minimum brightness (black brightness) of the child display has been significantly lowered to maintain good display performance.
The purpose is to improve display contrast ratio.

“Means to solve problems” Operation principle of the present invention F! l! The figures are shown in FIGS. 1 and 2.

FIG. 2 is an operation chart/diagram of FIG. 1.

A video scanning signal VC or 6f' is sent from the display control circuit 10.
When output at J Hz, lamp 1
brightness control is started. Brightness control is performed by the display control circuit 10
Then, the scanning signal V (output line 1 of PWM circuit 11 which manually controls the time width of the luminance data output 13 at the same time, PWM circuit 1) is output, and the main discharge current of the DC discharge lampco is output. The time width of the flow is controlled by a switch element 6. 1. Display system m times! 8shi0, PWMIi
The brightness control means is composed of the lF I 1 , SW, , H elements 6, and the like.

As shown in FIG. 2(a), when the scanning signal 1 is outputted, the timer 20 sets a delay time T1 as shown in FIG. 2(1).
Immediately after this delay time T1, the timer 21 creates a delay time T, as shown in c) in the figure. During this delay time T2, the switch element 2 of the high voltage switch circuit 22
2: The lamp is turned on and a slight discharge is caused by one lamp through the resistor I-1.The timer 20, 21, high voltage switch circuit 22, etc. constitute a minute discharge control means.

By the way, the above delay time T1 is regulated by the relationship between the period until the next scanning signal VC enters] 6,7 m5ec (in the case of 60Hz), and (16,7+n5ec-T,
There needs to be enough time for the two lamps 1 to start lighting with the direct current power source Ea between m5ec)pi) and to generate a slight discharge. This situation is determined from experimental data as shown in FIG. No. 311 shows the relationship between the value of the power source Ea and the starting time of Run 1]. The voltage value of power supply Ea is 500V
Then, when 0.5 tnsec is applied, lamp 1 is turned on. Show that.

In addition, the scanning signal V( is the one that is always output after the power-on of the large-sized video device is performed and the system is started. This is because the present invention provides the second scanning signal
This is the reference signal for starting the ramp of each display element, and it also has an appropriate time width and phase as shown in Figure 3 for the period of the scanning signal \l (with a 60 Hz frequency).
) T2 pulse (output of timer 21) to cause the lamp 1 to periodically discharge slightly, and after causing the lamp 1 to be slightly discharged by -degree, the main discharge current time is set using the low voltage DC power supply V1, which is much lower than the voltage value of the power supply Eε1. Is the width controlled?t). If each time the luminance becomes zero in relation to the luminance data of the display control circuit 10 or jl, the scanning signal V (or disappears and f = sip) causes a problem. , for 167m5ec until the next scanning signal VC,
This is because only the output pulses 1 and 2 of the timer 21 are output, so there is a one-cycle delay in image generation. If this phenomenon occurs frequently, the image becomes cloudy.

From the above operation, it can be seen that whether the lamp brightness control is
87. Each time the control starts, the lamp 1 is slightly discharged! Set it to . By doing this, immediately after the main discharge current is turned off by the switch element 6, as in the conventional example,
If a pulsed voltage higher than the voltage of the main discharge power source V or the fine discharge power source Ea is generated and fine discharge lighting cannot be maintained, the light will not turn off anytime.

In addition, slight discharge lighting occurs between 2 and 6 and 7 m5ec.
Since only a short time of 31°See is required, the brightness level during blanking when the main discharge current does not flow is reduced to about 1.15 l゛\ compared to the conventional one, and the contrast ratio is greatly improved. will be done.

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. Fig. 4 shows the embodiments, and Fig. 5 does not show the operating state thereof. The lamp is a double-tone discharge lamp composed of three primary color fluorescent discharge paths of R, +-; and B, and one filament 2. In this example, there are three discharge lamp configurations: R, +-x, and R.
R, G, R, Gt7) There may be 4 discharge paths. For the purpose of explanation, each discharge path is a differential for time width control of the main discharge current.
-day ratio by 50%-), every cycle 8, 8 +n
Turn it on after 5ec.

In addition, in this embodiment, control is performed to light up a slight discharge in all three discharge paths simultaneously.This does not increase the number of high-voltage switch circuits 22. This is because the entire display device and its configuration can be simplified.

When the display device is powered on, the power supplies VEf and Ea rise, and the filament 2 is preheated. On the other hand, the display control circuit 10 generates a scanning signal V (as shown in FIG. 5 <8>) at 60 Hz.
The WM circuit 11 is in scanning order 1, and is shown in FIGS.
), the flip-flop VC. ,,V. 1
1 is internally generated, corresponding to the brightness take (currently equivalent to 5096 duty ratio), and the time width is 8.8 + nq (・〈・ is generated in synchronization with each scanning signal ■), and the constant current circuit 231,
, 2 3c. 2 The transistors 6, . . . which are the switching elements of B□ are operated for a certain period of time.

On the other hand, the scanning signal ■ (is insulated by the isolator 2.1, and the scanning signal v (after generation, T.g) by the timer 2o.q+).
21 for time T, / moss on, each discharge path I, G, B
are simultaneously slightly discharged. From the start of this slight discharge control (]
6,7 TI+nscc land, firstly, the main discharge current or constant current amount i ¥823. , and then,
Discharge paths G, B and main discharge current or constant current circuit 23. , 2B.
This situation is shown as examples of lamp voltage waveforms in FIGS. 5(e) to (8).

Such a system (in wholesale, each discharge path 1-: , G
B(li7+main discharge time 8, 8+nsec(i
i2l, each discharge qf4 FF. , ('.; 2B is completely turned off, there is no generation of pulse-like voltage as in the conventional example, and there is no problem of instability when the light is maintained). In addition, the main discharge time of all discharge paths is zero, that is, the black luminance of the display screen when the control brightness is zero is slightly (1
The slight discharge brightness is 6,7 T,)+nsec, and the flutter brightness can be significantly reduced compared to the conventional example.

[Effects of the Invention 1] As described above, the present invention includes a brightness control means for controlling the brightness by controlling the pulse width of a DC discharge lamp using a periodic brightness control signal, and a brightness control means for controlling the brightness by controlling the pulse width of a DC discharge lamp using a periodic brightness control signal, and a time sufficient to start the DC discharge lamp. Therefore, each discharge path is completely turned off after the main discharge time of each discharge path. However, unlike the conventional example, there is no generation of pulse-like voltage, there is no problem such as instability of lighting maintenance, and the main discharge time of all discharge paths is zero, that is, the control brightness is set to zero. The black luminance on the display screen becomes the slight discharge luminance during the short period of time during which the brightness control starts, and the flash luminance can be significantly reduced compared to the previous example. Part 7 that is effective

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the embodiment 0) of the present invention, Fig. 2 is a characteristic diagram of the same tights\char 1, Fig. 3 is a characteristic diagram of the same
The figure is a front 2 diagram showing a specific example of the same as the above, FIG. 5 is an explanatory diagram of the same as the above, and FIG. DC discharge lamp, 2 is filament, 3 is anode, 4
, 5 is a resistor, E 2+ is a DC power supply for slight discharge, and Vl is a DC power supply for main discharge 6

Claims (1)

[Claims] (1) A DC discharge lamp that is equipped with one filament and at least one anode and has a discharge path that emits light independently for each anode, and is effective when DC power is applied to the DC discharge lamp via a current limiting resistor. It has a main discharge circuit that flows the main discharge current to obtain a brightness, and a slight discharge circuit that makes the DC discharge lamp into a slight discharge state and flows the main discharge current. a brightness control means for controlling the brightness by pulse width control; and a fine discharge control means for turning on the fine discharge circuit for a predetermined period of time sufficient to start the DC discharge lamp and before the start of the brightness control. A DC discharge lamp lighting device characterized by comprising: