JP2009134877A - Lighting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting apparatus with a plurality of LEDs in which an emission intensity of an LED can be detected without using an exclusive element for light receiving. <P>SOLUTION: The lighting apparatus includes a plurality of LEDs and a controlling portion which controls an emission intensity by lighting up each of the LEDs one by one and detecting the emission intensity of the lit LEDs by the LEDs which are switched off. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lighting device, and more particularly to a lighting device using a light emitting diode (hereinafter referred to as LED).

  Recently, lighting devices using LEDs have been developed as simple lighting devices that are small and can be driven by a battery, such as a combination of a plurality of single color LEDs or a combination of a plurality of LEDs of different emission colors. It has come to be used according to the application. In the illumination device for imaging, in order to obtain an emission spectrum in consideration of the light receiving characteristics of the imaging element, a combination of LEDs having different emission colors corresponding to the desired spectrum, for example, two red LEDs In addition, a combination of one green LED and one blue LED is known (see Patent Document 1).

Moreover, in such an illuminating device, in order to maintain appropriately the light emission intensity and light emission intensity ratio of several LED of different luminescent color, for every color by the photodetection element with the spectral filter corresponding to the luminescent color of each LED. Detect and feed back the detected value to control the power supplied to the corresponding LED, or each LED emits light at different timing, and the light emission intensity is detected sequentially for each light emission by one light detection element. The detected value is fed back to control the power supplied to each LED (for example, see Patent Document 2).
JP 2004-71807 A JP 2002-344031 A

As described above, in the illumination device using the LED, in order to perform feedback control to make the light emission intensity and the light emission intensity ratio of the LED constant, in addition to the light emitting LED, a light receiving element dedicated to light reception, that is, a light receiving element is separately provided. There is a problem of having to prepare.
The present invention has been made in consideration of such circumstances, and provides an illumination device that does not require a separate light receiving element by using a light emitting LED also as a light receiving element.

  The present invention provides a lighting device including a plurality of LEDs and a controller that controls the light emission intensity by sequentially turning on each LED and detecting the light emission intensity of the LED being turned on by the LED being turned off. is there.

  According to the present invention, the control unit sequentially turns on each LED, and detects the light emission intensity of the LED that is lit by the LED that is turned off to control the light emission intensity. Therefore, the control unit is dedicated for detecting the light emission intensity. It is not necessary to provide a light receiving element. Therefore, the lighting device can be made compact and the cost can be reduced.

  The illumination device according to the present invention includes a plurality of LEDs, and a controller that controls the light emission intensity by sequentially turning on each LED and detecting the light emission intensity of the LED being turned on by the LED being turned off. To do.

  The present invention utilizes the fact that an LED is a pn junction semiconductor and can be used as both a light emitting element and a light receiving element.

  In the pn junction light receiving element, current flows when the incident light energy is larger than the band gap energy, and functions as a light receiving element. Further, since the light emission wavelength of the LED is inversely proportional to the band gap energy, the LED functions as a light receiving element only for light having a wavelength equal to or shorter than the light emission wavelength. That is, an LED that emits green light can receive green or blue light and cannot receive red light.

  Therefore, in the present invention, when the plurality of LEDs include the first LED having the first emission wavelength and the second LED having the second wavelength longer than the first wavelength or the same as the first wavelength, the control unit is configured to The emission intensity is detected by the second LED.

  In the present invention, when the plurality of LEDs are composed of the first and second LEDs that emit blue light and green light, respectively, and the third and fourth LEDs that emit red light, the control unit is the first LED. Is detected by the second LED, the emission intensity of the second LED is detected by the third LED, the emission intensity of the third LED is detected by the fourth LED, the emission intensity of the fourth LED is detected by the third LED, and the first, first The emission intensity of the second, third and fourth LED elements is controlled.

The lighting device according to the present invention may further include a translucent member that integrally covers the plurality of LEDs.
In this invention, it is preferable that a control part performs the detection of the emitted light intensity of LED in a short period that a human eye cannot recognize.
In the present invention, it is particularly preferable that the plurality of LEDs are installed on the same plane and arranged so that the light of the LED being turned on is directly received by the LED being turned off.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. This does not limit the present invention. In addition, the same code | symbol is attached | subjected to the element which is common in each drawing.

Embodiment 1
FIG. 1 is a block diagram showing the configuration of the illumination device of the present invention.
As shown in the figure, the illuminating device controls the light emission intensity by detecting the light emission intensity of the light emitting unit 1 including a plurality of LEDs and each LED in turn, and the light emission intensity of the LED being turned on. A control unit 100 is provided.

  The control unit 100 includes a control circuit 10, a light emitting circuit 20, a light receiving circuit 30, and a switching circuit 40. The light emitting circuit 20 includes a DC power source and a drive circuit that supply a forward current to the pn junction of each LED of the light emitting unit 1 via the switching circuit 40 to cause each LED to emit light.

  The light receiving circuit 30 includes a detection circuit that detects a change in reverse current generated by light incident on each LED via the switching circuit 40.

  The switching circuit 40 includes a switching circuit, and supplies a forward current from the light emitting circuit 20 to each LED of the light emitting unit 1 and captures a reverse current from each LED of the light emitting unit 1 to the light receiving circuit 30. 10 is switched in accordance with the timing signal supplied from 10.

When the light emitting unit 1 is turned on, the control circuit 10 controls the light emitting circuit 20 and the switching circuit 40 so that the forward current is supplied from the light emitting circuit 20 to all the LEDs of the light emitting unit 1.
When detecting the light emission intensity of the light emitting unit 1, the control circuit 10 controls the light emitting circuit 20, the light receiving circuit 30, and the switching circuit 40, and sequentially supplies a forward current from the light emitting circuit 20 to each LED of the light emitting unit 1 at a predetermined timing. Supplying each LED to light, and detecting the light emission intensity of the lighted LED by converting the reverse current that flows when the lighted LED receives light according to the timing to the voltage by the light receiving circuit 30. To do.

  The control circuit 10 uses the light emitting circuit 20 to control the magnitude of the forward current to each LED according to the captured light emission intensity. Thereby, the light emission intensity of each LED is held at the set value. Thus, by detecting the light emission intensity of the LED using the LED and performing feedback control, the light emission intensity and the light emission intensity ratio of the LED can be properly maintained even if the light emission characteristic of the LED changes due to some cause. . The control circuit 10 is constituted by a microcomputer comprising a CPU, a ROM, and a RAM.

2 is a top view showing a light emitting module 1a used as the light emitting unit 1 (FIG. 1) in the first embodiment, and FIG. 3 is a cross-sectional view taken along the line AA in FIG.
As shown in these drawings, the light emitting module 1a includes a glass epoxy resin substrate 4 and includes four chip-shaped LEDs, that is, an LED (B) that emits blue light, an LED (G) that emits green light, The LED (R1) that emits red light and the red LED (R2) are mounted on the same plane of the substrate 4.

  As shown in FIG. 3, the light emitting module 1a is composed of a covering portion 5 that integrally covers four LEDs with a translucent resin such as a silicon-based resin, and a white non-translucent resin that reflects visible light. And the formed peripheral wall 3. The inner wall surface of the peripheral wall portion 3 is inclined and functions as a reflector that reflects light emitted from each LED. Eight connection terminals 6 for four LEDs are formed by a conductor pattern and are led out from the peripheral wall 3 toward the periphery of the substrate 4.

FIG. 4 is a timing chart showing the lighting timing of the LEDs (R1, R2, G, B), and FIG. 5 is a timing chart showing the capturing timing of the LEDs (R1, R2, G, B). In these figures, a period T ₀ is a normal lighting period, and a period Tt is a light emission intensity detection period.
In FIG. 4, the high period is the lighting period, and the low period is the extinguishing time.
In FIG. 5, the high period is the capture period.

  As can be seen from FIGS. 4 and 5, in the emission intensity detection period Tt, the LED (R1) emits light in the period T1, the LED (R2) receives the light emission, and the LED (R2) emits light in the period T2, The light emission is received by the LED (R1), the LED (G) emits light in the period T3, the light emission is received by the LED (R1), the LED (B) emits light in the period T4, and the light emission is indicated by the LED (G ) Is received.

  In this case, the light transmission / reception relationship between the LEDs is indicated by arrows in FIG. That is, FIG. 2 shows that LEDs (R1, R2, G, B) are arranged on the same plane (the surface of the substrate 4), and the emission intensity of one LED is detected by an adjacent LED at the closest distance from the LED. It is shown that.

  Therefore, in the LED that takes in light, not only the light emitted from the adjacent LED propagates through the covering portion 5 and is reflected by the interface of the covering portion 5 and the peripheral wall portion 3, but also the adjacent LED is laterally (on the substrate 4). Since the light emitted in the parallel direction can be received from a very short distance, the illumination device of this embodiment can be used sufficiently as a light receiving element even with an LED having a lower light receiving sensitivity than a photodiode generally used as a light receiving element. Has the effect of being able to.

The emission intensity detection period Tt is set to a time during which the human eye cannot recognize the blinking of the LED.
Further, the control circuit 10 controls the light emitting circuit 20 at an appropriate timing in the lighting period T ₀ according to the light emission intensity of each LED detected in the light emission intensity detection period Tt, and sets the light emission intensity of each LED to a desired set value. To correct.

The lighting time T ₀ of the continuous single lighting part at the time of capture is approximately the light emission cycle (for example, the time from capturing the blue LED light to the next capturing of the same blue LED light) when capturing periodically. It should be within 15msec. If the lighting time T ₀ is longer than this, white light emission may appear to flicker.

  Furthermore, it is preferable that the capture time Tt is shorter than 1/10 of the cycle To, and the capture times T1, T2, T3, and T4 are 800 μsec or less. Even when the time is longer than this, it looks white without any problem when looking still, but when the line of sight is moved, the phenomenon that the three colors R, G, and B appear separated (called color break) occurs. There is a case.

  If the capture time Tt is extremely shortened, the light emission intensity of the LED may not be stable. In addition, the AD converter for digitally processing the signal intensity cannot respond. In the present embodiment, signal processing can be performed by setting it to 60 μsec or more, but taking-in times T1, T2, T3, and T4 are set to 100 μsec in consideration of variations in LED characteristics. However, it goes without saying that T1, T2, T3, and T4 do not necessarily have to be equal.

Embodiment 2
In this embodiment, the light emitting module 1a shown in FIGS. 2 and 3 of the first embodiment is replaced with the light emitting module 1b shown in FIGS. 6 and 7, and other configurations are the same as those of the first embodiment.
In addition, the light emitting module 1b replaces the blue LED (B) and the green LED (G) of the light emitting module 1a with two blue LEDs (B1, B2) and two green LEDs (G1, G2), respectively. 6 is increased to 12 corresponding to the number of LEDs, and the other configuration is the same as that of the light emitting module 1a.
FIGS. 8 and 9 are diagrams corresponding to FIGS. 4 and 5, and are timing charts showing lighting timings and capturing timings of six LEDs (R1, R2, G1, G2, B1, and B2), respectively.

  As can be seen from FIGS. 8 and 9, in the emission intensity detection period Tt, the LED (R1) emits light in the period T1, the LED (R2) receives the light emission, and the LED (R2) emits light in the period T2, The light emission is received by the LED (R1), the LED (G1) emits light in the period T3, and the light emission is received by the LED (R1).

  Further, the LED (G2) emits light in the period T4, the LED (R2) receives the light emission, the LED (B1) emits light in the period T5, the LED (G1) receives the light emission, and the LED in the period T6. (B2) emits light, and the light emission is received by the LED (G2).

  In this case, the relationship of light exchange between the LEDs is indicated by arrows in FIG. That is, FIG. 6 shows that these six LEDs are arranged on the same plane (the surface of the substrate 4), and the emission intensity of one LED is detected by another LED that is closest to the LED. Yes. Therefore, this embodiment can achieve the same effect as that of the first embodiment.

Embodiment 3
In this embodiment, the light emitting module 1a shown in FIGS. 2 and 3 of the first embodiment is replaced with the light emitting module 1c shown in FIGS. 10 and 11, and other configurations are the same as those of the first embodiment. In the light emitting module 1c, the blue LED (B), the green LED (G), and the two red LEDs (R1, R2) of the light emitting module 1a are replaced with four same color LEDs (D1, D2, D3, D4). The other structure is the same as that of the light emitting module 1a.
FIGS. 12 and 13 are diagrams corresponding to FIGS. 4 and 5, and are timing charts showing lighting timings and capturing timings of four same color LEDs (D 1, D 2, D 3, D 4), respectively.

  As can be seen from FIGS. 12 and 13, in the emission intensity detection period Tt, the LED (D1) emits light in the period T1, the LED (D2) receives the light emission, and the LED (D2) emits light in the period T2, The LED (D3) receives the light emission, the LED (D3) emits light in the period T3, the LED (D4) receives the light emission, the LED (D4) emits light in the period T4, and the light emission is the LED (D1). ) Is received.

  In this case, the relationship of light exchange between the LEDs is indicated by arrows in FIG. That is, FIG. 10 shows that these four LEDs are arranged on the same plane (the surface of the substrate 4), and the emission intensity of one LED is detected by another LED that is closest to the LED. Yes. Therefore, this embodiment can achieve the same effect as that of the first embodiment.

Modified Example FIGS. 14 and 15 are diagrams corresponding to FIGS. 6 and 7 showing a light emitting module 1d (modified example) obtained by modifying the light emitting module 1b of the second embodiment. In the light emitting module 1d, a metal lead frame 7 is used instead of the substrate 4 (FIG. 7), and LEDs (B1, G1, R1) and LEDs (B2, G2, R2) are respectively provided on the lead frame 7. Arranged in a row. Further, the connection terminals 6 for the respective LEDs are integrally formed by a lead frame 7.

The lead frame 7 has an insulating and heat conductive adhesive layer (for example, a thermosetting epoxy adhesive sheet) on a heat sink 9 made of a material having good heat conductivity (for example, ceramics, aluminum, or copper). ) 8 is pasted.
In the light emitting module 1d, the inner wall surface of the peripheral wall portion 3 is inclined so that the light emitted from each LED is efficiently reflected and emitted as in the light emitting module 1b.

  A light emitting module 1e shown in FIG. 16 is a modification of the light emitting module 1d (FIG. 15). In the light emitting module 1e, the lead frame 7 is integrally and firmly bonded to the resin forming the peripheral wall portion 3.

It is a block diagram which shows the structure of the illuminating device of Embodiment 1. FIG. 3 is a top view of the light emitting module of Embodiment 1. FIG. It is AA arrow sectional drawing of FIG. 3 is a timing chart showing the lighting timing of the LED according to the first embodiment. 3 is a timing chart showing the LED capture timing of Embodiment 1. FIG. 3 is a diagram corresponding to FIG. 2 of the second embodiment. FIG. 4 is a diagram corresponding to FIG. 3 of the second embodiment. FIG. 5 is a diagram corresponding to FIG. 4 of the second embodiment. FIG. 6 is a diagram corresponding to FIG. 5 of the second embodiment. FIG. 9 is a diagram corresponding to FIG. 2 of Embodiment 3. FIG. 4 is a diagram corresponding to FIG. 3 of the third embodiment. FIG. 5 is a diagram corresponding to FIG. 4 of Embodiment 3. FIG. 6 is a diagram corresponding to FIG. 5 of the third embodiment. FIG. 7 is a view corresponding to FIG. 6 illustrating a modification of the second embodiment. FIG. 8 is a view corresponding to FIG. 7 showing a modification of the second embodiment. FIG. 16 is a diagram corresponding to FIG. 15 illustrating another modification of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emission part 1a, 1b, 1c, 1d, 1e Light emission module 3 Perimeter wall part 4 Board | substrate 5 Covering part 6 Connection terminal 7 Lead frame 8 Adhesive layer 9 Heat sink 10 Control circuit 20 Light emission circuit 30 Light reception circuit 40 Switching circuit 100 Control part

Claims (7)

  A lighting device including a plurality of LEDs and a controller that controls the light emission intensity by sequentially turning on each LED and detecting the light emission intensity of the LED being turned on by the LED being turned off.   2. The lighting device according to claim 1, wherein the plurality of LEDs are installed on the same plane, and are arranged so that light emission of the LED being turned on is directly received by the LED being turned off.   The lighting device according to claim 1, further comprising a translucent member that integrally covers the plurality of LEDs.   The lighting device according to claim 1, wherein the plurality of LEDs include two LEDs that respectively emit green light and blue light, and two LEDs that emit red light.   The plurality of LEDs include a first LED having a first emission wavelength and a second LED having a second emission wavelength that is longer than the first emission wavelength or the same as the first emission wavelength, and the control unit determines the emission intensity of the first LED. The illuminating device of Claim 1 detected by 2LED.   The plurality of LEDs include first and second LEDs that emit blue light and green light, respectively, and third and fourth LEDs that emit red light, and the control unit detects the emission intensity of the first LED by the second LED. The light intensity of the second LED is detected by the third LED, the light intensity of the third LED is detected by the fourth LED, the light intensity of the fourth LED is detected by the third LED, and the first, second, third and fourth LED elements The illuminating device of Claim 1 which controls the emitted light intensity of.   The lighting device according to claim 1, wherein the control unit performs detection of the light emission intensity of the LED in a short period of time that human eyes cannot recognize.

Images