JP2007012405A - Lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting system capable of preventing generation of color unevenness. <P>SOLUTION: An LED driving circuit 122 lights odd numbered LEDs and even numbered LEDs alternatively or one by one in order so that overlap of lights is eliminated when two LEDs of different colors are adjacently and closely arranged when performing emission drive of a plurality of LEDs 121-1 to 121-n. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an illumination device that illuminates, for example, a meter mounted on a vehicle, and more particularly to an illumination device in which a plurality of light emitting diodes are arranged close to each other in parallel.

As a lighting device for a vehicle instrument, for example, one described in Patent Document 1 is known.
The illumination device described in Patent Document 1 includes a plurality of first light emitting diode driving circuits in which a plurality of light emitting diodes for illuminating a meter and a first current limiting resistor are connected in series, and these first light emitting diode driving circuits in parallel. A second light emitting diode drive circuit connected in series with a smaller number of light emitting diodes and a second current limiting resistor than the first light emitting diode drive circuit, for example, driving with different illuminance of the instrument such as daytime and nighttime Between the circuits, the light emitting diodes that illuminate the meter are balanced so that there is no difference in luminance.

The vehicle instrument illumination device having such a configuration is used in a form suitable for a so-called backlight illumination method using a plurality of light emitting diodes (LEDs) immediately below a clock display unit including a liquid crystal display device (LCD), for example. It is done.
JP 2004-228385 A

By the way, in the illuminating device applied to the said backlight illumination method, LED of the same color is arrange | positioned closely.
In particular, when LED lights having different hues (having slightly different wavelengths even if they are the same color) are arranged close to each other, as shown in FIG. 1, when LEDs 1 to 6 having different hues are DC-driven at the same time, In the part indicated by “a” in the figure, an area point having a different color is generated, and a point slightly different from the light emitting area of the adjacent LED indicated by “b” in the figure and a non-overlapping area is generated. That is, light unevenness (color unevenness) occurs.
Therefore, in the conventional lighting device, the transparent milky white plate is colored so that the portion where the light overlaps or the portion where the light does not overlap, so that the LED is not directly visible, and light unevenness ( Color unevenness) was reduced.

As described above, in the conventional lighting device, since the lighting timing of the LEDs is the same, the milky white plate is colored.
However, since coloring is performed by printing, the printing unevenness at the time of printing and the density deviation of the ink are more varied than the shade of the LED light, so it is difficult to obtain uniform illumination light (color).

  An object of the present invention is to provide an illuminating device that can prevent the occurrence of color unevenness without coloring a transparent plate or the like and can achieve uniform illumination.

  A first aspect of the present invention is an illumination device that illuminates a portion to be illuminated, in which light from a plurality of light emitting diodes arranged at a predetermined interval and an adjacent light emitting diode among the plurality of light emitting diodes is emitted. A light emitting diode driving circuit that drives the plurality of light emitting diodes so as not to overlap and illuminates the illuminated portion.

  Preferably, the light emitting diode driving circuit alternately drives odd-numbered and even-numbered light emitting elements in the light emitting element array.

  Preferably, the light emitting diode driving circuit sequentially drives a plurality of light emitting diodes one by one.

  Preferably, the light emitting diode driving circuit includes first and second light emitting diode groups including a plurality of light emitting diodes, wherein light shielding is provided between the first light emitting diode group and the second light emitting diode group. Sequentially drives the plurality of light emitting diodes of the first light emitting diode group with a first drive signal, and the plurality of light emitting diodes of the second light emitting diode group have a duty different from that of the first drive signal. Driven with a drive signal of 2.

  Preferably, the plurality of light emitting diodes emit light of the same color having different hues.

  Preferably, the illuminated portion is a liquid crystal display device, and a transmissive diffusion plate is disposed between the arrangement position of the plurality of light emitting diodes and the liquid crystal device.

  According to the present invention, it is not necessary to color a translucent milky white plate as a countermeasure against light unevenness (color unevenness) with respect to the illumination directly under the liquid crystal, and it is possible to make the illumination (color shade) uniform.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram illustrating an overall configuration of an LCD (liquid crystal display device) clock display unit to which the illumination device according to the present embodiment is applied.

  As shown in FIG. 2, the LCD clock display unit 10 is detachably disposed on the circuit board 11, the illumination device 12 mounted on the circuit board 11, the LCD holder 13 detachable from the circuit board 11, and the LCD holder 13. It has LCD14 as a to-be-illuminated part, and the diffusion plate 15 which consists of a transparent milky white board | plate material arrange | positioned between the upper surface of the holder 13, and the lower surface of LCD14.

On the circuit board 11, a lighting device 12 is mounted with a plurality of LEDs (light emitting diodes) 121-1 to 121-n (n = 12 in the example of FIG. 2) and an LED drive circuit (122) described in detail later. Has been.
The circuit board 11 is mounted with a connector portion 111 that is connected to a plurality of connection terminals of the LCD 14.
The circuit board 11 is also mounted with a drive system for the LCD 14.

The illuminating device 12 includes a plurality of LEDs 121 (−1 to −n) and an LED drive circuit 122.
The LEDs 121-1 to 121-n are linearly arranged on the circuit board 11 in a straight line at a predetermined interval in the longitudinal direction of the LCD 14.
The holder 13 corresponding to this LED array is formed with an opening (not shown) so that the LCD 14 can be illuminated.
Since each LED 121-1 to 121-n has a light amount and a light emission color that vary depending on a current value, the LED resistance is set to LEDMAX, the circuit resistance is set to a maximum (IFMAX) state, and the brightness is determined by the duty.
Further, in the LED driving circuit 122 of the present embodiment, when performing light emission driving of the plurality of LEDs 121-1 to 121-n, two LEDs having slightly different colors are adjacent to each other and arranged close to each other. In this case, a driving method that reduces color unevenness by lighting without overlapping of light is adopted.

  Below, the 1st-3rd structural example of the LED drive circuit which employ | adopted the drive method which reduces this color nonuniformity is demonstrated in relation to drawing.

  FIG. 3 is a circuit diagram showing a first configuration example of the LED drive circuit of the present embodiment. FIG. 4 is a waveform diagram of drive signals of the LED drive circuit of FIG. FIG. 5 is a diagram showing a driving principle of the LED driving circuit of FIG.

In the LED drive circuit 122A of FIG. 3, for ease of understanding, an example in which six LEDs 121-1 to 121-6 are mounted is shown.
In addition to the six LEDs 121-1 to 121-6, the LED drive circuit 122A includes a power source (battery) V12 in which the anode sides of the LEDs 121-1 to 121-6 are connected in parallel, and the LEDs 121-1 to 121-6. Resistive elements R1 to R6 connected in series to the cathode of the driving transistor TR1, TR2 composed of npn transistors, inverter INV122, resistive element R7 connected between the base of the driving transistor TR1 and the input line of the driving signal SDRV, the driving transistor A resistance element R8 connected between the base and emitter of TR1, a resistance element R9 connected between the base of the driving transistor TR2 and the output line of the inverted driving signal SDRVX of the inverter INV122, and a connection between the base and emitter of the driving transistor TR2. Having a resistance element R10 That.

In the LED driving circuit 122A, the other ends of the resistance elements R1, R3, R5 having one end connected to the cathodes of the odd-numbered LEDs 121-1, 121-3, 121-5 in the LED array are connected in common, and the node ND1 is connected. The node ND2 is configured by commonly connecting the other ends of the resistance elements R2, R4, and R6 having one end connected to the cathodes of the even-numbered LEDs 121-2, 121-4, and 121-6 in the LED array. Yes.
The base of the drive transistor TR1 is connected to the input line of the drive signal SDRV via the resistor element R7, the emitter is grounded, and the collector is connected to the odd-numbered common node ND1 in the LED array.
The base of the drive transistor TR2 is connected to the input line of the inverted drive signal SDRVX via the resistor element R9, the emitter is grounded, and the collector is connected to the even-numbered common node ND2 of the LED array.

That is, as shown in FIG. 5, the LED drive circuit 122A in FIG. 3 collectively drives the odd-numbered LEDs 121-1, 121-3, 121-5 in the LED array to emit light, and then the even-numbered LEDs 121- 2, 121-4 and 121-6 are driven to emit light collectively.
A series of operations are sequentially performed, and a plurality of LEDs are driven to emit light so that a uniform color can be recognized by the afterglow phenomenon.
As a result, by turning on a plurality of LEDs without overlapping light, there are no portions with different hues, and color unevenness can be reduced.

  FIG. 6 is a circuit diagram showing a second configuration example of the LED drive circuit of the present embodiment. FIG. 7 is a waveform diagram of drive signals of the LED drive circuit of FIG. FIG. 8 is a diagram showing a driving principle of the LED driving circuit of FIG.

The LED drive circuit 122B of FIG. 6 includes drive transistors TR1 to TRn for each of the n LEDs 121-1 to 121-n, and also includes respective LEDn base counters CNT122. The input clock CLK is input to the counter 1221, The drive signals SDRV1 to SDRVn of the drive transistors TR1 to TRn are sequentially generated at different timings, and the n LEDs 121-1 to 121-n are sequentially emitted one by one.
Also by this LED driving device 122B, by turning on a plurality of LEDs without overlapping light, there are no portions with different hues, and color unevenness can be reduced.

  FIG. 9 is a circuit diagram showing a third configuration example of the LED drive circuit of the present embodiment. FIG. 10 is a waveform diagram of drive signals of the LED drive circuit of FIG. FIG. 11 is a diagram showing a driving principle of the LED driving circuit of FIG.

The LED drive circuit 122C in FIG. 9 is basically the same as the LED drive circuit 122B in FIG. 6, but is configured to be compatible with illumination that requires two types of brightness on a single substrate. .
As shown in FIG. 11, the LEDs 121A-1 to 121A-n and 121B-1 to 121B-n are caused to emit light sequentially by driving signals having different duties with the light shielding plate 1221 as a boundary, thereby causing color unevenness on both sides. We are trying to reduce it.
The drive signals having different duties are generated by AND gates A1 to An using the first drive signals SRDV1A to SDRVnA for the LEDs 121A-1 to 121A-n generated by the n-ary counter CNT122 and the input clock CLK, Second drive signals SRDV1B to SDRVnB supplied to the drive transistors TR1B to TRnB provided corresponding to the respective 121B-1 to 121B-n are generated.
Also by this LED driving device 122C, by turning on a plurality of LEDs without overlapping light, there are no portions with different hues, and color unevenness can be reduced.

  As described above, according to the present embodiment, when the LED driving circuit 122 performs light emission driving of the plurality of LEDs 121-1 to 121-n, two LEDs having slightly different colors are adjacent to each other, and When the LEDs are arranged close to each other, the odd-numbered and even-numbered LEDs are turned on alternately or sequentially one by one so that there is no overlap of light. As a countermeasure against (color unevenness), there is no need to color a transparent milky white plate, and the illumination (color shade) can be made uniform.

It is a figure for demonstrating the subject of the conventional illuminating device. It is a figure which shows the whole structure of the LCD (liquid crystal display device) clock part to which the illuminating device concerning this embodiment is applied. It is a circuit diagram which shows the 1st structural example of the LED drive circuit of this embodiment. FIG. 4 is a waveform diagram of drive signals of the LED drive circuit of FIG. 3. It is a figure which shows the drive principle of the LED drive circuit of FIG. It is a circuit diagram which shows the 2nd structural example of the LED drive circuit of this embodiment. It is a wave form diagram of the drive signal of the LED drive circuit of FIG. It is a figure which shows the drive principle of the LED drive circuit of FIG. It is a circuit diagram which shows the 3rd structural example of the LED drive circuit of this embodiment. FIG. 10 is a waveform diagram of drive signals of the LED drive circuit of FIG. 9. It is a figure which shows the drive principle of the LED drive circuit of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... LCD clock display part, 11 ... Circuit board, 12 ... Illumination device, 121-1-121-n, 121-1A-121-nB ... LED, TR1-TRn ... Drive Transistor 122, 122A-122C ... LED drive circuit, 13 ... LCD holder, 14 ... LCD, 15 ... Diffuser.

Claims (6)

An illumination device that illuminates an illuminated part,
A plurality of light emitting diodes arranged at predetermined intervals;
A light-emitting diode driving circuit that drives the plurality of light-emitting diodes to illuminate the illuminated portion so that light from adjacent light-emitting diodes among the plurality of light-emitting diodes does not overlap. The lighting device according to claim 1, wherein the light-emitting diode driving circuit alternately drives odd-numbered and even-numbered light-emitting elements in a light-emitting element array. The lighting device according to claim 1, wherein the light emitting diode driving circuit sequentially drives the plurality of light emitting diodes one by one. Having first and second light emitting diode groups including a plurality of light emitting diodes;
Light shielding is provided between the first light emitting diode group and the second light emitting diode group,
The light emitting diode driving circuit sequentially drives a plurality of light emitting diodes of the first light emitting diode group with a first driving signal, and drives the plurality of light emitting diodes of the second light emitting diode group to the first driving signal. The lighting device according to claim 3, wherein the lighting device is driven by a second drive signal having a different duty. The lighting device according to any one of claims 1 to 4, wherein the plurality of light emitting diodes emit light of the same color having different colors. The illuminated part is a liquid crystal display device,
The illuminating device according to any one of claims 1 to 5, wherein a transmissive diffusion plate is disposed between an arrangement position of the plurality of light emitting diodes and the liquid crystal device.

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