JP2009266460A - Light-emitting diode illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting diode illumination device in which even when a failure occurs in one light-emitting diode, the whole illumination device does not have lights-out. <P>SOLUTION: The light-emitting diode illumination device includes a light-emitting part 100 in which light emitting blocks 101-10n are connected in series which include a first light-emitting diode 110 and a second light-emitting diode 120, respectively, and a switching circuit 130 which makes a drive current Id to flow to any of the first light-emitting diode 110 and the second light-emitting diode 120, and a control circuit 20 which monitors a conduction state of the first light-emitting diode 110 in which the drive current Id flows and controls the switching circuit 130 according to its conduction state. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting diode illumination device using a light emitting diode as a light source.

  In recent years, an illuminating device using a light emitting diode (LED) as a light source instead of a fluorescent lamp or the like has been put into practical use. By using a light emitting diode as a light source, effects such as long life and energy saving can be obtained as compared with the case of using a fluorescent tube.

For example, the brightness of the entire lighting device can be increased by connecting a plurality of light emitting diodes in series. A method of using an existing equipment as it is by attaching an illumination tube containing a plurality of light emitting diodes (hereinafter referred to as an “LED tube”) to an existing fluorescent lamp luminaire instead of a fluorescent tube has been studied. (For example, refer to Patent Document 1).
JP 2002-197901 A

  However, for example, when an LED tube in which a plurality of light emitting diodes are connected in series is attached to an existing fluorescent lamp lighting fixture, if a failure occurs in one light emitting diode and a driving current does not flow to the light emitting diode, the entire lighting device There was a problem that turned off. Since light emitting diodes are expensive, if a failure occurs in one light emitting diode, replacing the entire LED tube results in enormous costs.

  In view of the above problems, an object of the present invention is to provide a light-emitting diode illuminating device that does not turn off the entire lighting device even when a failure occurs in one light-emitting diode.

  According to one aspect of the present invention, (a) a light-emitting unit including a light-emitting block including a first and second light-emitting diodes and a switching circuit that allows a drive current to flow to either of the first and second light-emitting diodes; (B) A light-emitting diode illuminating device including a control circuit that monitors a conduction state of a first light-emitting diode through which a drive current flows and controls a switching circuit according to the conduction state is provided.

  According to the present invention, it is possible to provide a light-emitting diode illuminating device that does not turn off the entire illuminating device even when a failure occurs in one light-emitting diode.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the lengths of the respective parts, and the like are different from the actual ones. Therefore, specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention includes the shape, structure, arrangement, etc. of components. It is not specified to the following. The technical idea of the present invention can be variously modified within the scope of the claims.

  As shown in FIG. 1, the light-emitting diode illuminating device according to the embodiment of the present invention includes any one of the first light-emitting diode 110 and the second light-emitting diode 120, and the first light-emitting diode 110 and the second light-emitting diode 120. The conduction state of the light emitting unit 100 formed by serially connecting the light emitting blocks 101 to 10n each including the switching circuit 130 for flowing the drive current Id and the first light emitting diode 110 through which the drive current Id flows is monitored. And a control circuit 20 that controls the switching circuit 130 in accordance with (n: an integer of 2 or more). Although FIG. 1 shows an example in which a plurality of light emitting blocks 101 to 10n are connected in series, the number of the light emitting blocks 101 to 10n is not limited, and the number of light emitting blocks included in the light emitting unit 100 may be one.

  As shown in FIG. 1, the anodes of the first light emitting diode 110 and the second light emitting diode 120 are connected to the input terminal 11 a, and the cathode is connected to the switching circuit 130. The first light emitting diode 110 and the second light emitting diode 120 may be formed on the same semiconductor substrate, or separate light emitting diode elements may be disposed on the printed circuit board.

  Moreover, you may accommodate the light emission blocks 101-10n in a package, respectively. At this time, for example, a light emitting diode that emits blue light is employed for the first light emitting diode 110 and the second light emitting diode 120, and a red and green phosphor is applied to the package through which the emitted light is transmitted, thereby providing a package. The output light from can be made white. Alternatively, a light emitting diode that emits white light may be employed for the first light emitting diode 110 and the second light emitting diode 120.

  The switching circuit 130 includes a first switch 131 and a second switch 132. One terminal of the first switch 131 is connected to the cathode of the first light emitting diode 110, and the other terminal is connected to the output terminal 11b. One terminal of the second switch 132 is connected to the cathode of the second light emitting diode 120, and the other terminal is connected to the output terminal 11b. As will be described later, connection (ON) / release (OFF) of the first switch 131 and the second switch 132 is controlled by the control circuit 20.

  The light emitting blocks 101 to 10n included in the light emitting unit 100 are connected to the input terminals 11a of other light emitting blocks 101 to 10n adjacent to the output terminal 11b to form a series connection chain including the light emitting blocks 101 to 10n. Then, each end of the serial connection chain of the light emitting blocks 101 to 10 n is connected to the drive circuit 30. That is, the input terminal 11 a of the light emitting block 101 and the output terminal 11 b of the light emitting block 10 n are connected to the drive circuit 30.

The drive circuit 30 supplies a drive current Id to the light emitting blocks 101 to 10n to cause the first light emitting diode 110 or the second light emitting diode 120 in the light emitting blocks 101 to 10n to emit light. The drive current Id flows from the input terminal 11a of the light emission block 101 to the output terminal 11b of the light emission block 10n.

  In the following, it is assumed that the first switch 131 of the switching circuit 130 is turned on and the second switch 132 is turned off in the initial state of the light emitting blocks 101 to 10n. That is, in the initial state, the first light emitting diode 110 is connected in series between the input terminal 11a and the output terminal 11b. Then, the drive current Id flows from the anode of the first light emitting diode 110 connected to the input terminal 11a to the cathode connected to the output terminal 11b. On the other hand, the drive current Id does not flow through the second light emitting diode 120.

  The control circuit 20 monitors the conduction state of the first light emitting diode 110 through which the drive current Id flows. For example, the forward voltage Vf between the anode and the cathode of the first light emitting diode 110 in the light emitting state and the driving current Id flowing through the first light emitting diode 110 are monitored. When it is detected that an abnormality such as a short circuit failure or an open failure has occurred in the first light emitting diode 110, the driving current Id flowing through the first light emitting diode 110 is cut off, and the driving current is supplied to the second light emitting diode 120. The switching circuit 130 is controlled so that Id flows. Specifically, the first switch 131 is turned off and the second switch 132 is turned on, and the second light emitting diode 120 is connected in series between the input terminal 11a and the output terminal 11b. As a result, the drive current Id does not flow through the first light emitting diode 110, while the drive current Id flows from the anode to the cathode of the second light emitting diode 120. For this reason, the second light emitting diode 120 emits light.

  In many cases, the light emitting diode is changed from a light emitting state to a non-light emitting state due to a short circuit failure of the light emitting diode. When a short failure occurs in the first light emitting diode 110, the drive current Id flowing through the first light emitting diode 110 is generally increased, and the forward voltage Vf between the anode and the cathode is generally decreased. . Hereinafter, a case where the control circuit 20 monitors the forward voltage Vf of the first light emitting diode 110 of each of the light emitting blocks 101 to 10n will be described as an example.

The control circuit 20 monitors the forward voltage Vf of the first light emitting diode 110 transmitted from each of the light emitting blocks 101 to 10n by the monitoring signal Sv. When detecting a failure occurring in any one of the light emitting blocks 101 to 10n, for example, the first light emitting diode 110 of the light emitting block 10x, the control circuit 20 causes the driving current Id to flow through the second light emitting diode 120. The switching signal Sc for controlling the switching circuit 130 is transmitted to the switching circuit 130 of the light emission block 10x (1 ≦ x ≦ n). For example, when the forward voltage Vf of the first light emitting diode 110 of the light emitting block 10x does not satisfy the preset setting condition, the control circuit 20 is generated in the first light emitting diode 110 of the light emitting block 10x. It is determined that a failure has been detected. Here, it is assumed that the control circuit 20 transmits the switching signal Sc to the switching circuit 130 when the forward voltage Vf becomes lower than the set value V _LMT . A specific method for setting the set value V _LMT will be described later.

  The switching circuit 130 of the light emitting block 10x that has received the switching signal Sc turns on the second switch 132 and turns off the first switch 131. As a result, the drive current Id flows through the second light emitting diode 120 of the light emitting block 10x, and the drive current Id does not flow through the first light emitting diode 110. That is, the second light emitting diode 120 emits light in place of the failed first light emitting diode 110. For this reason, the light emission state of the light emission block 10x is maintained. Further, since the drive current Id flowing through the light emitting block 10x in which the failure has occurred does not change, the light emitting state of the other light emitting blocks 101 to 10n is not affected.

  As described above, in the light-emitting diode illuminating device illustrated in FIG. 1, the switching circuit 130 changes the path through which the drive current Id flows in the light-emitting blocks 101 to 10n, whereby the first light-emitting diode 110 and the second light-emitting device. The light emission state of the diode 120 is switched. At this time, by turning off the first switch 131 after turning on the second switch 132, the drive current Id continues to flow through the light emitting unit 100.

The set value V _LMT of the forward voltage Vf for detecting a failure occurring in the first light emitting diode 110 can be arbitrarily set. Normally, as shown in FIG. 2, when a failure occurs in the light emitting diode and the forward voltage Vf decreases to about 50% of the normal light emitting state, the light emitting diode enters a non-light emitting state. When the failure further proceeds, the light emitting diode is short-circuited, and the forward voltage Vf becomes 0V. For this reason, it is preferable to set the set value V _{LMT to} about 50% of the normal value of the forward voltage Vf. In addition, the setting value V _LMT is set to the forward voltage Vf so that the driving current Id flows through the second light emitting diode 120 before the first light emitting diode 110 changes from the light emitting state to the non-light emitting state. More preferably, it is set to about 60 to 70% of the normal value, for example, about 65%. Specifically, when the forward voltage Vf in the normal light emission state is about 3.5V, the set value V _LMT is set to about 1.8V to 2.3V.

In addition to setting the lower limit set value V _LMT below the forward voltage Vf value as described above, in order to detect a case where the forward voltage Vf rises abnormally, the forward voltage Vf An upper limit value may be set. When a failure occurs in the light emitting diode and the forward voltage Vf increases and becomes 150% or more of the normal state, the open state is entered and the non-light emitting state is entered. For this reason, for example, the set value V _LMT may be set to about 150% or about 130 to 140% of the normal value of the forward voltage Vf.

  In addition, although the example in which the switching circuit 130 is arranged between the cathodes of the first light emitting diode 110 and the second light emitting diode 120 and the output terminal 11b is shown, as shown in FIG. Of course, the switching circuit 130 may be disposed between the anode of the first light emitting diode 110 and the second light emitting diode 120.

  In the example illustrated in FIG. 1, the control circuit 20 monitors the forward voltage Vf of all the first light emitting diodes 110 of the light emitting blocks 101 to 10n. However, a control circuit that monitors the forward voltage Vf of the first light emitting diode 110 and controls the switching circuit 130 based on the monitoring result may be disposed for each of the light emitting blocks 101 to 10n.

  FIG. 1 illustrates an example in which the light emitting blocks 101 to 10n each include the first light emitting diode 110 and the second light emitting diode 120. However, for example, as shown in FIG. 4, a plurality of light emitting diodes 111 to 11m and light emitting diodes 121 to 12m may be arranged between the input terminal 11a and the switching circuit 130 (m: an integer of 2 or more). At this time, the control circuit 20 may monitor the forward voltage Vf of each of the light emitting diodes 111 to 11m, or may monitor the voltage between the anode of the light emitting diode 111 and the cathode of the light emitting diode 11m.

  In the above description, the case where the forward voltage Vf is monitored to detect a failure of the first light emitting diode 110 has been described. However, in order to detect a failure of the first light emitting diode 110, other measurable parameters whose values are different between normal and failure may be monitored. For example, the current value flowing through the first light emitting diode 110 or the amount of heat generated by the first light emitting diode 110 is monitored.

  As described above, according to the light-emitting diode illuminating device according to the embodiment of the present invention, the driving current Id is caused to flow through the second light-emitting diode 120 instead of the first light-emitting diode 110 in which a failure is detected. Even if a failure occurs in the first light emitting diode 110, the light emitting state of the light emitting blocks 101 to 10n does not appear. That is, it is possible to provide a light-emitting diode illuminating device that does not turn off the entire illuminating device even when a failure occurs in one light-emitting diode. This is particularly effective in a light-emitting diode illuminating device in which a plurality of light-emitting diodes are connected in series. As a result, the cost of replacing the light emitting diode illumination device can be saved. Further, since each of the light emitting blocks 101 to 10n includes the first light emitting diode 110 and the second light emitting diode 120, the light emitting block is switched by switching the light emitting states of the first light emitting diode 110 and the second light emitting diode 120. The light emission lifetime of 101 to 10n can be extended.

(Other embodiments)
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the description of the embodiment already described, the switching circuit 130 includes the first switch 131 and the second switch 132 connected to the first light emitting diode 110 and the second light emitting diode 120, respectively. However, for example, as shown in FIG. 5, the switching circuit 130 switches one switch 133 so that the drive current Id is supplied to either the first light emitting diode 110 or the second light emitting diode 120. Good.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a schematic diagram which shows the structure of the light emitting diode illuminating device which concerns on embodiment of this invention. It is a schematic diagram which shows the relationship between the forward voltage of the light emitting diode which concerns on embodiment of this invention, and a light emission state. It is a schematic diagram which shows the other structural example of the light emission block of the light emitting diode illuminating device which concerns on embodiment of this invention. It is a schematic diagram which shows the other structural example of the light emission block of the light emitting diode illuminating device which concerns on embodiment of this invention. It is a schematic diagram which shows the other structural example of the switching circuit of the light emitting diode illuminating device which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Control circuit 30 ... Drive circuit 100 ... Light emission part 101-10n ... Light emission block 110 ... 1st light emitting diode 120 ... 2nd light emitting diode 130 ... Switching circuit 131 ... 1st switch 132 ... 2nd switch

Claims (5)

A light-emitting unit having a light-emitting block including a first and second light-emitting diodes, and a switching circuit for passing a drive current to any of the first and second light-emitting diodes;
A light emitting diode illuminating device comprising: a control circuit that monitors a conduction state of the first light emitting diode through which the driving current flows and controls the switching circuit according to the conduction state.   The control circuit controls the switching circuit so that the drive current flows through the second light emitting diode before the first light emitting diode changes from a light emitting state to a non-light emitting state. Item 4. The light-emitting diode illuminating device according to Item 1.   The control circuit monitors a forward voltage between the anode and the cathode of the first light emitting diode, and when the forward voltage no longer satisfies a set condition, the driving current is supplied to the second light emitting diode. The light emitting diode illumination device according to claim 1, wherein the switching circuit is controlled to flow.   The light-emitting diode illuminating apparatus according to claim 1, wherein the light-emitting unit includes a plurality of the light-emitting blocks connected in series.   The light emitting diode illumination device according to claim 4, wherein the control circuit monitors a conduction state of the first light emitting diode of each of the plurality of light emitting blocks.

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