JP2009182074A - Light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device which has a simple circuit configuration, a small harmonic component of an input current, and a high-power factor. <P>SOLUTION: The light-emitting device includes: a light emission unit 1 constituted by connecting a plurality of series circuits 11 to 14, each formed by connecting a current limiting element and one or more solid light-emitting elements in series, in parallel; and a lighting device 2 which is connected to an AC power source AC and rectifies an AC voltage in a full-wave manner to supply a drive voltage to the light-emitting unit 1. In the light-emitting unit 1, at least one series circuit comprises a combination of solid light-emitting elements different in number or intrinsic voltage, and then the plurality of series circuits 11 to 14 having different turn-on periods are connected in series. The series circuits having the different turn-on periods are driven to light having nearly equal average current values. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting device using a solid light emitting element as a light source.

Conventionally, a light emitting device using a solid light emitting element such as a light emitting diode as a light source has been proposed. As a lighting control method for such a light emitting device, for example, a direct current lighting control method (for example, see Patent Document 1) in which a direct current voltage obtained by rectifying and smoothing an alternating current voltage is applied to a solid state light emitting element, and an alternating current voltage is rectified and smoothed. A switching lighting control method is known in which a DC voltage is boosted and a rectangular wave voltage obtained by switching the boosted DC voltage at a high frequency is applied to a solid state light emitting device (see, for example, Patent Document 2).
JP 2006-73637 A Japanese Patent Laid-Open No. 11-67471

  By the way, the luminous efficiency of solid-state light emitting devices has been greatly improved in recent years, and those that could only be used for auxiliary lighting have been gradually used for main lighting. When used in main lighting applications, it is the harmonics of the input current that must be noted in the future.

  In the technique disclosed in Patent Document 1, a device for making an input current close to a sine wave by controlling a transistor connected in series with an LED is devised. Moreover, in patent document 2, the device which reduces the harmonic of an input current is made | formed by switching at high frequency. In any case, however, a control circuit is required, which causes an increase in size and cost. Furthermore, the capacitor input type configuration disclosed as the conventional example of Patent Document 2 does not require a control circuit, but has a problem that harmonic components of the input current increase.

  The present invention has been made in view of the above points, and an object thereof is to provide a high-power factor light-emitting device with a simple circuit configuration and a low harmonic component of an input current.

  In order to achieve the above object, according to the first aspect of the present invention, as shown in FIG. 1, a plurality of series circuits 11 to 14 in which a current limiting element and one or more solid state light emitting devices are connected in series are connected in parallel. A light emitting device 1 and a lighting device 2 connected to an alternating current power source AC and full-wave rectifying an alternating current voltage to supply a driving voltage to the light emitting portion 1, wherein the light emitting portion 1 A plurality of series circuits 11 to 14 having different lighting periods are connected in parallel.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the light emitting section 1 is a combination in which the number of solid state light emitting elements of at least one series circuit is different.

  The invention of claim 3 is characterized in that, in the invention of claim 1, the light emitting section 1 is a combination in which the intrinsic voltages of the solid state light emitting elements of at least one series circuit are different.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the light emitting section 1 is driven to be lit in an average current value substantially equal in a series circuit having different lighting periods.

  According to a fifth aspect of the present invention, in the light emitting device according to any one of the first to third aspects, the light emitting unit 1 has a lighting period that is higher for a lighter element having a specific brightness according to a variation in the specific brightness of the solid state light emitting element. A series circuit is configured to be shorter.

  The invention of claim 6 comprises the light emitting unit 1, the lighting device 2, and the lamp 3 in which the light emitting unit 1 and the lighting device 2 are housed in the invention of any one of claims 1 to 5. Characteristic (FIG. 3).

  According to the first to third aspects of the present invention, in the plurality of series circuits, the lighting period is increased with respect to the pulsating voltage obtained by rectifying the AC voltage by changing the number of solid-state light emitting elements and the intrinsic voltage of the series circuit. Since the current flows through the multiple series circuits, which differ for each of the multiple series circuits, the combined current has a shape almost similar to a sine wave, and an input current with less harmonics is obtained. Can do.

  According to the invention of claim 4, in the plurality of series circuits having different lighting periods, the series circuit having a short lighting period is driven so that the average current becomes substantially equal by increasing the peak current more than others. Thus, there is an effect that variation in brightness of the entire solid-state light emitting element, that is, a difference in brightness of the light emitting element for each series circuit is reduced.

  According to the fifth aspect of the present invention, by using the light emitting element in different lighting periods according to the brightness variation of the solid state light emitting element, the effect of reducing the brightness variation of the entire solid state light emitting element can be obtained. That is, a relatively bright light-emitting element can be used in a series circuit with a short lighting period, whereby the overall brightness can be averaged.

  According to the invention of claim 6, it is possible to realize a light emitting device having a lamp that exhibits the effect of any one of claims 1 to 5.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the present embodiment includes a plurality of series circuits (11 to 14) formed by connecting resistors R (R1 to R4), which are current limiting elements, and one or more light emitting diodes L in series. And a lighting device 2 that is connected to an AC power source AC and that rectifies an AC voltage in a full wave and supplies a driving voltage Vdc to the light emitting unit 1.

  The lighting device 2 is composed of, for example, a diode bridge, and full-wave rectifies the AC voltage from the AC power supply AC, and outputs the rectified pulsating voltage Vdc to the light emitting unit 1. The lighting device 2 may have another circuit configuration as long as the AC voltage is full-wave rectified.

  The light emitting unit 1 includes a plurality of series circuits (11 to 14) formed by connecting resistors R (R1 to R4) and one or more light emitting diodes L in series. 14, the number of light-emitting diodes L connected in series is different.

  The operation of this embodiment will be described below. As shown in FIG. 2, since the light emitting diode L of the first series circuit 11 is lit only when the pulsating voltage Vdc is higher than the forward voltage Vf1 necessary to light the light emitting diode L, And the non-lighting state are repeated alternately. Here, the current flowing through the light emitting diode L is If1.

  Next, the number of light-emitting diodes L connected in series in the second series circuit 12 is smaller than the number of serial connections in the first series circuit 10, and therefore the forward voltage Vf2 is lower than the forward voltage Vf1. The current flowing through the series circuit is If2.

  Similarly, the number of light-emitting diodes L connected in series in the third series circuit 13 is further smaller than the number of serial connections in the second series circuit 12, and therefore the forward voltage Vf3 is further lower than the forward voltage Vf2. The current flowing through the third series circuit 13 is If3.

  Further, the number of light-emitting diodes L connected in series in the fourth series circuit 14 is further smaller than the number of serial connections in the third series circuit 13, and therefore the forward voltage Vf4 is lower than the forward voltage Vf3. The current flowing through the series circuit 14 of No. 4 is If4.

  As described above, a plurality of series circuits 11, 12, 13, and 14 having different forward voltages Vf1, Vf2, Vf3, and Vf4 are connected in parallel, currents corresponding to different lighting periods flow, and the input current Iin Since the current flows as a combined current If1 + If2 + If3 + If4 of the currents flowing through the parallel circuits, as a result, a waveform close to a sine wave is obtained, and a current with less harmonic distortion is obtained.

  In the present embodiment, each series circuit having a different forward voltage is described as one circuit, but the number of each series circuit may be an arbitrary number. That is, two or more series circuits having the same lighting period may be connected in parallel.

  Further, although the configuration using the resistor R as the current limiting element is described, it is needless to say that it can be realized even with a constant current element or a constant current circuit.

(Embodiment 2)
In the first embodiment described above, the forward voltages Vf1, Vf2, Vf3, and Vf4 of the first series circuit 11, the second series circuit 12, the third series circuit 13, and the fourth series circuit 14 are made different. In this embodiment, the number of light emitting diodes L in each of the series circuits 11 to 14 is the same, but in this embodiment, the number of light emitting diodes L in each of the series circuits 11 to 14 is the same. By using the light emitting diodes L having different voltages, the forward voltages Vf1, Vf2, Vf3, and Vf4 are made different.

  Further, the number of light emitting diodes in each series circuit may be varied in series, and the specific voltage of the light emitting diodes in each series circuit may be a different combination.

  Furthermore, in one series circuit, a plurality of types of light emitting diodes having different specific voltages may be connected in series so that the ratio (use ratio) of the light emitting diodes having different specific voltages in each series circuit may be different.

  That is, it is possible to arbitrarily create a series circuit having a different forward voltage by appropriately using a combination having a different number of series in the first embodiment and a combination having a different specific voltage in the second embodiment. Can be made closer to a sine wave.

(Embodiment 3)
In the above-described first and second embodiments, the forward voltage of each series circuit is different, so that the lighting period during which a current flows in each series circuit is different. In the present embodiment, the current limiting resistors R1, R2, R3, and R4 of the series circuits 11, 12, 13, and 14 are made different so that in a plurality of series circuits having different lighting periods, Then, driving is performed so that the average current (effective current of AC half cycle) becomes substantially equal in each series circuit by flowing more peak current than others. Thereby, the effect that the variation of the brightness of the whole solid light emitting element, ie, the difference in the brightness of the light emitting element for each series circuit, is reduced can be obtained.

  If a constant current circuit such as a current mirror circuit is used instead of the current limiting resistors R1, R2, R3, and R4 of the series circuits 11, 12, 13, and 14, the peak current can be more accurately defined. By setting the series circuit with a shorter lighting period to flow more peak current, the average current (= peak current × lighting period / AC half cycle) of each series circuit can be controlled equally.

(Embodiment 4)
In Embodiment 3 described above, the variation in brightness of the entire solid-state light-emitting element is reduced by making the average current of each series circuit substantially equal on the assumption that the inherent brightness of the solid-state light-emitting element is substantially equal. In the present embodiment, solid state light emitting elements having different light emitting efficiencies are used, and a solid state light emitting element with higher light emitting efficiency is driven so that the lighting period is shortened, thereby reducing variations in brightness of the entire solid state light emitting element. is there.

  For example, in the configuration of FIG. 1, since the light emitting diode of the first series circuit 11 has the shortest lighting period, the light emitting diode having the highest light emission efficiency is used. Further, since the light emitting diode of the fourth series circuit 14 has the longest lighting period, the light emitting diode having the lowest light emission efficiency is used. As described above, the brightness variation of the entire solid-state light-emitting element is configured by configuring the series circuit so that the lighting period is shortened as the element having a brighter intrinsic brightness according to the variation in the inherent brightness of the solid-state light-emitting element. Can be reduced.

  In addition, by implementing Embodiment 3 and Embodiment 4 in appropriate combination, variation in brightness of the entire solid-state light emitting element can be further reduced.

(Embodiment 5)
Embodiment 5 of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 3, the light emitting unit 1 and the lighting device 2 of the first embodiment are housed in a lamp 3 of a traffic light. The lamp 3 is a substantially oval box having three substantially circular openings 4 for exposing the light emitting part 1 to the outside, and the light emitting diodes of the light emitting part 1 over the entire surface of each opening 4 Are arranged opposite to each other. The three light emitting units 1 respectively disposed in the three openings 4 are connected to the output of the lighting device 2 through signal control relay contacts and the like.

  The color emitted by the light-emitting diode is different for each opening 4, and is green, yellow, and red from the left opening 4 in FIG. 3. Needless to say, the colors emitted from the light emitting diodes and the arrangement thereof are not limited to those described above, and can be changed according to the application of the traffic signal. For example, in the case of a pedestrian traffic light, two colors of red and blue are arranged in the vertical direction, and in the case of an arrow signal for right turn / left turn / straight, the blue light-emitting diodes are directed to the right, left, and upward These are arranged so as to constitute each arrow shape.

  In each opening 4, the light emitting diodes of the first series circuit 11 having a large number are arranged at the peripheral portion, and the light emitting diodes of the fourth series circuit 14 having a small number are arranged in the approximate center. In this case, since the light emitting diode of the fourth series circuit 14 having a low forward voltage Vf4 has almost no non-lighting period, the light emitting diode at the substantially center of each opening 4 (in the figure during the lighting period of the traffic signal) It ’s almost always on (like a black circle). Therefore, for example, when the moment of an accident is photographed with a video camera of a drive recorder mounted on a taxi or the like, the light emitting diode at the substantially center of each opening 4 is lit almost always. The traffic signal status can be recognized regardless of the condition.

It is a circuit diagram which shows the structure of Embodiment 1-4 of this invention. It is a wave form diagram which shows operation | movement of Embodiment 1-4 of this invention. It is a front view which shows the light-emitting device of Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emission part 2 Lighting device L Light emitting diode (solid-state light emitting element)
R1-R4 resistance (current limiting element)
11-14 First to fourth series circuits

Claims (6)

A light-emitting unit composed of a plurality of series circuits connected in series with a current-limiting element and one or more solid-state light-emitting elements connected in parallel, and connected to an AC power source to drive the light-emitting unit by full-wave rectification of AC voltage A light-emitting device including a lighting device that supplies voltage, wherein the light-emitting unit includes a plurality of series circuits having different lighting periods connected in parallel. The light emitting device according to claim 1, wherein the light emitting unit is a combination in which the number of solid light emitting elements of at least one series circuit is different. The light emitting device according to claim 1, wherein the light emitting unit is a combination having different intrinsic voltages of the solid state light emitting elements of at least one series circuit. The light emitting device according to any one of claims 1 to 3, wherein the light emitting unit is driven to be lighted in a series circuit having different lighting periods so that an average current value is substantially equal. The light emitting unit is configured in a series circuit so that a lighting period is shortened as a device having a brighter intrinsic brightness according to a variation in intrinsic brightness of a solid state light emitting device. 4. The light emitting device according to any one of 3. The light-emitting device according to claim 1, comprising the light-emitting unit, the lighting device, and a lamp that houses the light-emitting unit and the lighting device.

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