JPH0799463B2 - Lighting control device for variable color fluorescent lamp - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lighting control device for a variable color fluorescent lamp used in a large color display device.

BACKGROUND ART Conventionally, this type of variable color fluorescent lamp used in a large color display device has been shown in FIGS. 4 to 7. That is, this variable color fluorescent lamp is composed of U-shaped portions 1a, 1b and 1c composed of three U-shaped glass tubes and a rectangular parallelepiped portion 2 formed of a glass plate. , 1
Phosphors of different emission colors (for example, red phosphor, green phosphor, and blue phosphor) are applied to the inner surfaces of b and 1c, respectively, and the U-shaped portions 1a, 1b, and 1c of the respective phosphors are coated. A light emission control electrode, that is, the anodes 3a, 3b, 3c are sealed at one end of the.
On the other hand, on the front surface of the rectangular parallelepiped part 2, communication holes 5a, 5b, 5c communicating with the other open ends of the U-shaped parts 1a, 1b, 1c are bored, and inside the rectangular parallelepiped part 2 serving as a common discharge space. Is provided with a common electrode which is paired with each anode 3a, 3b, 3c, that is, a common cathode 4.
Further, an auxiliary electrode that does not contribute to light emission, that is, an auxiliary anode 3d is provided on the side of the common cathode 4 provided in the common discharge space. The discharge space composed of the U-shaped portions 1a, 1b, 1c and the rectangular parallelepiped portion 2 is kept airtight with the outside, and a rare gas and a metal vapor gas such as mercury are sealed inside. Further, a light shield (not shown) is attached to the outer surface of the rectangular parallelepiped portion 2.

FIG. 8 shows an example of a basic circuit of a lighting control device for such a variable color fluorescent lamp, in which the DC power source 8 is connected to each of the anodes 3a, 3b, 3c and the auxiliary anode 3d via a selection switch circuit 7 for switching the discharge path. The emission color is changed by controlling the discharge switching timing. Further, current limiting elements 6a to 6c are respectively connected in series to the respective anodes 3a, 3b, 3c and the auxiliary anode 3d so that a constant lamp current flows. In the figure, the starter 9 generates a high voltage at the time of starting. As shown in FIG. 9, the selection changeover switch circuit 7 is specifically composed of switching transistors Qa, Qa ', Qb, Qb', Qc, Qc ', Qd, whose switching ON / OFF duty is variable by a control circuit. It is formed by Qd ′, and the DC power source 8 is set to each anode 3a, 3b, 3c at an appropriate timing.
And the discharge path is switched by applying to the auxiliary anode 3d. The control circuit is a clock pulse generator PG, a ring counter LC that counts clocks output from the clock pulse generator PG and sets a light emission possible period of each color, and a lighting signal that generates a lighting control signal that controls light emission of each color. It is formed by generators SGa, SGb, SGc and a gate circuit GC including AND circuits A _{1 to} A ₄ and inverter circuits I _{1 to} I ₃ . FIGS. 10 and 11 are time charts (shown by the operation of the switch contacts 7a to 7d) showing the timing when the DC power is applied to the respective anodes 3a, 3b, 3c and the auxiliary anode 3d, and the clock pulse. Within each repeating period T set by the clock pulse generated by the generator PG, a red light emission possible period T _R , a green light emission possible period T _G , and a blue light emission possible period T _B are set,
The light-emission periods T _R , T _G , and T _{B of} each color are fixedly set to be equal. Further, the repetition cycle T is set so that flicker due to switching does not occur. First
FIG. 10 shows a state in which the power source is applied in the brightest light emission state (a state in which light is emitted over the entire period of each light emission possible period T _R , T _G , T _B ). The light emitting positions of the respective colors are not the same, but if viewed from a sufficiently long distance or mixed with the diffusing means, it will appear that they are emitting light of substantially white. FIG. 11 shows a case where the actual light emission period of each color is set to 1/2 of each light emission possible period T _R , T _G , T _B by the selection changeover switch circuit 7, and the brightness is as shown in FIG. Compared with the case, it becomes 1/2, and the light emission state is 50% dimming. in this case,
During the period in which the discharge is performed between the common cathode 4 and the auxiliary anode 3d, the phosphor does not emit light, and the light is apparently turned off, which is a light emission pause period. Although it is conceivable that the light emission pause period is completely turned off (discharging stopped state), when the state of complete extinction is repeated, the temperature of the common cathode 4 is drastically changed and the common cathode 4 changes. There is a problem that the life is shortened. Therefore, a constant current is caused to flow in the common cathode 4 by causing discharge with the auxiliary anode 3d during the light emission suspension period, which is a so-called pseudo-off state. by the way,
In such a lighting control device, the light-emission periods T _R , T _G , and T _{B of} each color are fixedly set to be equal, and each color in the brightest light-emission state (operating state of FIG. 10) is set. The lamp input power that contributes to the light emission is almost constant, but the brightness (eg, brightness) of each color is as follows: green light emission> red light emission> blue light emission. Here, when trying to realize a white light emission state with an arbitrary color temperature where the brightness is almost the same for each color (the brightness ratio is 1: 1: 1), the actual light emission period of the green light emission and the red light emission is shown. The light emission possible period T _R and T _G must be made shorter, and there is a problem that the light emission efficiency cannot be set to the maximum due to the existence of the light emission suspension period.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to make it possible to realize a white light emitting state with an arbitrary color temperature while maximizing the light emitting efficiency. An object is to provide a lighting control device for a color fluorescent lamp.

DISCLOSURE OF THE INVENTION (Embodiment 1) FIG. 1 shows a specific circuit of an essential part of an embodiment of the present invention.
In a lighting control device similar to the conventional example shown in FIG. 8 and FIG. 9, the ring counter LC is used instead of the light-emission period setting circuit 10 for arbitrarily setting the light-emission periods T _R , T _G , and T _B of each color. The selectable switching circuit 7 is provided, and the light-emissible period setting circuit 10 includes four one-shot flip-flops.
It is formed by F _{1 to} F ₄ . The pulse width of the pulse generated in each one-shot flip-flop F _{1 to} F ₄ is set by the external capacitors C _{1 to} C ₄ and the resistors R _{1 to} R ₄ , and the red, Green emission period
The resistors R ₂ and R ₃ that set T _R and T _G are formed by volumes.

The operation of the embodiment will be described below. Now, by adjusting the resistance value of the resistors R ₂ and R _{3 that} consist of a volume,
Emission period T _R , T corresponding to red or green emission
_G can be set arbitrarily, and T is the repetition period set by the clock pulse generated by the clock pulse generator PG.
T _B is determined by T _B = T− (T _R + T _G ). For example, the light-emission period T _R , T _G , T _B of each color indicates the light emission efficiency of the phosphor of each color. Considering this, it is set as shown in FIG. If the light-emission periods T _R , T _G , and T _B are set so that the brightness of each emission color is the same (the brightness ratio is 1: 1: 1), light emission is possible over the entire period. A white light emission state is obtained, and the color temperature of the white light emission state can be changed by adjusting the light emission possible periods T _R and T _G to make the luminance of each emission color different. in this case,
Since it is possible to prevent the light emission pause period from existing in the white light emitting state, it is possible to maximize the light emission efficiency. FIG. 3 is a time chart when the light emitting period of each color is approximately halved to obtain a white light emitting state with 50% dimming. The light emission period setting circuit 10 is the second
It goes without saying that any circuit configuration may be used as long as it is possible to set the light-emissible period as shown in the diagram time chart, and the invention is not limited to the first embodiment.

[Advantages of the Invention] As described above, according to the present invention, a power source is supplied to a discharge electrode for emitting each color of a variable color fluorescent lamp in which a discharge path for emitting light of a plurality of colors is formed in a shared discharge space through a selection changeover switch circuit. A lighting control device for a variable-color fluorescent lamp, in which the emission color is changed by switching the discharge switching timing of the selection changeover switch circuit in time series.
Since the selection changeover switch circuit is provided with the light-emission period setting circuit that arbitrarily sets the light-emission period of each color without providing the light-emission period at the time of 0% lighting, it is possible to prevent the light-emission period from existing in the white light emission state. There is an effect that a white light emitting state of an arbitrary color temperature can be realized with the light emitting efficiency being maximized.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an essential part of an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the operation of the same, FIG. 4 is a perspective view of a variable color fluorescent lamp according to the present invention, and FIG. Partial cutaway front view, FIGS. 6 and 7 are partially cutaway side views of the same, FIG. 8 is a diagram showing a basic configuration of a lighting control circuit, and FIG. 9 is a block circuit diagram showing a specific configuration of a conventional example. FIG. 10 and FIG. 11 are explanatory diagrams of the same operation. Reference numeral 7 is a selection changeover switch circuit, and 10 is a light emission possible period setting circuit.

Claims (1)

[Claims] 1. A power source is applied to a discharge electrode for emitting each color of a variable color fluorescent lamp, in which a discharge path for emitting light of a plurality of colors is formed in a shared discharge space, through a selection changeover switch circuit, and the selection changeover switch circuit is operated. In a lighting control device for a variable color fluorescent lamp that changes the emission color by switching the discharge switching timing in time series, at the time of 100% lighting, the emission possible period of each color is arbitrarily set without providing a light emission pause period. A variable color fluorescent lamp lighting control device, wherein a possible period setting circuit is provided in a selection switch circuit.