JP2006172820A - Led lighting control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve lighting control in which all the LEDs are operated without any problem even if the control for dimming light control brightness to 15% of the maximum brightness is carried out. <P>SOLUTION: In a lighting control device in which a plurality of serially-connected LEDs are lighted by using an AC voltage from an AC power source, and by installing a zero-cross detecting part which detects a zero-cross point of an AC voltage waveform and a dimming control part which controls the dimming of an LED group, by obtaining a wave height point of the AC voltage waveform from the AC power source, and by carrying out the pulse width modulation of the voltage (PMW control synchronized with power source frequency) which is supplied to the LED group because its wave height point Pp is taken as the reference, the voltage supplied to the LED group is prevented from being the voltage Vf or less in which the LED group of serial-connection is operable even if the light control brightness is reduced to 15% of the maximum brightness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an LED lighting control device applied to a light emitting / display device using a plurality of LEDs as a light source, such as an LED signal lamp.

  Conventionally, a three-color signal lamp installed on a road or the like is composed of an incandescent bulb (light source), a reflector arranged on the back side of the incandescent bulb, and a front cover arranged on the front side of the incandescent bulb. The front cover has a structure in which red, blue and yellow signal colors are colored.

  In recent years, LED (light emitting diode) type signal lamps have been put into practical use for the purpose of reducing power consumption and maintenance / management efforts (see, for example, Patent Document 1). .

  The LED signal lamp uses a LED unit in which a large number of LEDs (light emission color: red, blue, or yellow) are mounted on an LED substrate as a light source. The LED unit is housed in a lamp case and the front side of the LED group. Is covered with a transparent front lens cover. Moreover, as a signal lamp using an LED unit as a light source, in addition to a three-color signal lamp, for example, an LED flashing lamp that is installed at a branching point or a curved part of a road and used to call a driver's attention Has also been put to practical use.

In LED signal lamps, LED flashing lights, and the like, dimming control may be performed in which the luminance is reduced with respect to daytime luminance (maximum luminance). As dimming control applied to the LED group, when the LED group is turned on using an AC voltage from an AC power source, for example, as shown in FIG. Phase control of controlling the voltage supplied to the LED group by shifting in the direction of M or N is applied (see, for example, Patent Document 2).
JP 2000-67386 A JP 2004-273267 A

  By the way, when dimming LED by phase control, there exist the following problems.

  First, the LED has a characteristic that when the voltage supplied from an AC power supply or the like becomes lower than the operation start voltage, the current stops flowing and the lighting (operation) becomes impossible. Therefore, it is necessary to use the LED above the operation start voltage. There is.

  On the other hand, a large number of LEDs are connected in series to an LED signal lamp, an LED flashing lamp, and the like, and a plurality of LED groups connected in series are connected in parallel. For example, in a flashing yellow signal lamp, 32 LEDs (for example, operation start voltage = 2.0 V) are connected in series to one row of a plurality of LED groups connected in parallel, and all LEDs in one row are connected. The voltage Vf required to light up is 64V (Vf = 2.0V × 32). In addition, in a green signal lamp such as a traffic signal lamp, 24 LEDs (for example, operation guarantee voltage = 3.0 V) are connected in series in one row, and the voltage required to light all the LEDs in one row. Vf is 72V (Vf = 3.0V × 24).

  Then, in the flashing lamp or the like, the nighttime luminance is adjusted to 15% of the daytime luminance (maximum luminance), and in the dimming method based on the general phase control described above, as shown in FIG. There is a case where most of the voltage applied to the LED group connected in series is lower than Vf (absolute value) necessary for lighting, and there is a problem that all the LEDs do not light up. .

  The present invention has been made in order to solve such a problem. In order to light up a group of LEDs connected in series with an AC power supply, the dimming brightness is controlled to 15% of the maximum brightness. Another object is to provide an LED lighting control device capable of realizing dimming control in which all LEDs operate without problems.

  The lighting control device of the present invention is a lighting control device that lights a plurality of LEDs connected in series using an AC voltage from an AC power supply, and detects a zero-cross point of an AC voltage waveform, and the plurality of LEDs A dimming control unit that controls dimming of the LED, and the dimming control unit obtains a crest point of the AC voltage waveform based on the zero cross point detected by the zero cross detection unit, and determines the crest point. It is characterized by being configured to modulate the pulse width of the voltage supplied to the plurality of LEDs as a reference.

  The crest point is a point (phase angle) Pp (see FIG. 4) at which the voltage (absolute value) becomes the maximum value (crest value) in a half cycle of the AC voltage waveform.

  According to the lighting control device of the present invention, the peak point of the AC voltage waveform from the AC power source is obtained, and the pulse width modulation (PWM control synchronized with the power source frequency) of the voltage supplied to the plurality of LEDs with the peak point as a reference. As shown in FIG. 5, for example, even if the pulse width PM of the voltage is narrowed down, the voltage supplied to the LED group does not fall below Vf required for lighting, and all LEDs operate without any problem ( Light up).

  In the lighting control device of the present invention, an illuminance sensor that detects the brightness (illuminance) around a place where a plurality of LEDs are installed is provided, and the dimming level is determined based on the detection output of the illuminance sensor. You may comprise so that the pulse width of the voltage supplied to these LED may be modulated according to a light level. When such a configuration is adopted, in the dimming range from daytime luminance (maximum luminance) to nighttime luminance (15% of daytime luminance), luminance dimming according to the surrounding brightness is performed, for example, in five levels of dimming levels. Can be done automatically.

  According to the lighting control device of the present invention, a peak point of an AC voltage waveform from an AC power source is obtained, and control (PWM control) is performed to modulate the pulse width of the voltage supplied to a plurality of LEDs with the peak point as a reference. Therefore, even if the dimming brightness is controlled to 15% of the maximum brightness, all the LEDs operate without any problem. In addition, basically, since a method of performing luminance dimming by phase control of the AC voltage waveform is adopted, it is possible to adjust luminance without using a dimming transformer.

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

-LED lamp-
First, an LED type lamp to which the present invention is applied will be described with reference to FIG.

  An LED-type lamp 10 shown in FIGS. 1A and 1B is an LED-type flashing lamp that is installed at a branching point / curve portion of a road and used to call a driver's attention. Two light emitting portions (yellow) 11 and 11 are provided. These two light emitting units 11 and 11 are arranged in the vertical direction of the LED lamp 10. In addition, the LED lamp 10 is provided with hoods 16, 16 that cover the upper area on the front side of the light emitting units 11, 11.

  Each of the light emitting units 11 and 11 uses LED units 12 and 12 (see FIG. 2) in which a large number of LEDs (light emitting color: yellow) 13 and 13 are mounted on the LED substrate 14 as light sources. The LED units 12 and 12 are accommodated in lamp cases 10a and 10a, respectively. In addition, the front side of the LEDs 13... 13 of the LED units 12 of the respective colors is covered with a front lens cover 15. Each LED unit 12 has LEDs 13... 13 whose emission color is yellow mounted in a dot arrangement as shown in FIG.

  Then, as shown in FIG. 3, a large number of LEDs 13... 13 constituting the LED unit 12 of the light emitting unit 11 are connected in series with a predetermined number (for example, 32) of LEDs 13. The LED 13 group is connected in parallel, and the lighting control device 1 that controls the lighting of the LEDs 13... 13 is disposed on the back side of the LED substrate 14 (see FIG. 1).

-Lighting control device-
Next, the lighting control device 1 will be described with reference to FIGS.

  The lighting control device 1 of this example includes a dimming circuit 2, a blinking circuit 3, and the like, and an AC power supply 5 of AC 100V is connected to the dimming circuit 2. The dimming circuit 2 is connected to an illuminance sensor (for example, a CdS cell) 4 that detects ambient brightness (illuminance).

  The flashing circuit 3 supplies a flashing signal for alternately turning on / off the LED units 12 and 12 (for example, 60 times / min) to the dimming circuit 2 (the dimming control unit 22).

  The dimming circuit 2 includes a zero cross detection unit 21 and a dimming control unit 22.

  The zero cross detection unit 21 detects the zero cross point of the AC voltage waveform from the AC power supply 5 and outputs the detection signal to the dimming control unit 22.

  The dimming control unit 22 is configured by an MPU (Micro Processor Unit), a delay circuit, a memory, and the like, and executes processing such as dimming level setting and PWM control synchronized with the power supply frequency described below.

<Dimming level setting>
The dimming control unit 22 determines the dimming level using the detected illuminance value from the illuminance sensor 4. Specifically, a table showing the relationship between the illuminance detection value by the illuminance sensor 4 and the dimming level is stored in the memory of the dimming control unit 22 in advance, and the illuminance detection value from the illuminance sensor 4 is referred to by the table. The dimming level is determined by conversion. In this example, the dimming range is from daytime luminance (maximum luminance) to nighttime luminance (15% of daytime luminance), and, for example, five levels of dimming levels are set within the range.

<PWM control synchronized with power supply frequency>
The dimming control unit 22 performs PWM control synchronized with the power supply frequency by the following operations (1) to (3).

  (1) As shown in FIG. 4, the zero cross point Cp of the AC voltage waveform from the AC power supply 5 is detected by the zero cross detection unit 21, and the AC voltage waveform from the AC power supply 5 is based on the detected zero cross point Cp. Is obtained. Here, when the AC power supply 5 is 60 Hz, the period T is known: T = 16.7 msec (T = 20 msec in the case of 50 Hz), so the zero cross point Cp is detected, and from the zero cross point Cp to T / 4 The peak point Pp can be obtained by calculating a position (phase angle) shifted by a certain amount.

  (2) The pulse width of the voltage corresponding to the dimming level described above, that is, the on-time [tw1 + tw2] shown in FIG. 4 is determined using the obtained peak point Pp as a reference (center). Note that tw1 and tw2 may be the same value, or one of them may be a larger value than the other.

  (3) On-delay value tdon and off-delay value tdoff for the zero-cross point Cp are determined based on the obtained on-time [tw1 + tw2], and the LEDs 13... 13 based on the on-delay value tdon and the off-delay value tdoff The pulse width PW of the voltage supplied to is set. Thus, the pulse width PW of the voltage supplied to the LEDs 13,... 13 is set by the on-delay value tdon and the off-delay value tdoff obtained with reference to the crest point Pp, so that the on-delay value tdon and the off-delay value By changing tdoff in the direction of the arrow in FIG. 4, the voltage with the pulse width PW according to the dimming level can be supplied to the LEDs 13... 13 and dimming based on the detected illuminance value of the illuminance sensor 4. Dimming according to the level becomes possible.

  Here, although not illustrated, the lighting control device 1 includes a full-wave rectification circuit, and performs full-wave rectification after the above-described phase control (PWM control) of the AC voltage waveform to supply a voltage to the LEDs 13. Supply.

  The dimming control unit 22 executes the dimming control described above, and at the same time, executes a control for alternately turning on / off the LED units 12 and 12 according to the blinking signal from the blinking circuit 3.

  As described above, according to the lighting control device 1 of this example, dimming in a range from daytime luminance (maximum luminance) to nighttime luminance (15% of daytime luminance) is possible. Moreover, the peak point Pp of the AC voltage waveform from the AC power source 5 is obtained, and pulse width modulation (PWM control synchronized with the power source frequency) of the voltage supplied to the LEDs 13. Even if the dimming brightness is reduced to 15%, all the LEDs 13 in the LED unit 12 operate without any problem. The reason will be described below.

  First, as described above, when the voltage supplied from an AC power supply or the like is lower than the operation start voltage, the LED has a characteristic that current does not flow and lighting cannot be performed. The operation start voltage of the yellow LED is about 2.0V.

  In this example, a large number of LEDs 13... 13 constituting the LED unit 12 are connected in series in 32 rows, and the voltage Vf required to light all the LEDs 13. Although it is 64 V (Vf = 2.0 V × 32), as described above, the pulse width PW of the voltage supplied to the LEDs 13... 13 is modulated using the peak point Pp of the AC voltage waveform as a reference. Thus, even if the pulse width PM corresponding to 15% dimming is modulated, the voltage supplied to the LEDs 13... 13 does not fall below the voltage Vf, and all the LEDs 13. Accordingly, it is possible to stably and reliably realize dimming in a range from daytime luminance (maximum luminance) to nighttime luminance (15% of daytime luminance).

  In the above embodiment, an example in which the present invention is applied to an LED flashing light has been described. However, the present invention is not limited to this, and an LED signal lamp, an LED caution light, or other LED light emission / display The present invention can be applied to devices and the like, and even when applied to such devices and apparatuses, the same operational effects as described above can be achieved.

  The present invention provides dimming within a range from daytime luminance (maximum luminance) to nighttime luminance (15% of daytime luminance) when lighting an LED group in which a plurality of LEDs are connected in series using an AC voltage from an AC power supply. Can be used effectively to realize the problem without problems.

It is a figure which writes and shows together the front view (A) and side view (B) which show an example of the LED type lamp (LED type flashing light) to which the lighting control apparatus of this invention is applied. It is a front view of the LED unit used for the LED type lamp of FIG. It is a block diagram which shows the structure of an example of the lighting control apparatus of this invention. It is explanatory drawing of the light control performed with the lighting control apparatus of FIG. It is action explanatory drawing of the lighting control apparatus of FIG. It is explanatory drawing of the light control system by general phase control. It is a figure which shows the problem of the light control system of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lighting control apparatus 2 Dimming circuit 21 Zero cross detection part 22 Dimming control part 3 Flashing circuit 4 Illuminance sensor 5 AC power supply 10 LED type lamp (flashing light)
11 Light emitting unit 12 LED unit 13 LED

Claims (2)

  A lighting control device that lights a plurality of LEDs connected in series using an AC voltage from an AC power source, and controls a zero-cross detection unit that detects a zero-cross point of an AC voltage waveform, and controls dimming of the plurality of LEDs A dimming control unit, and the dimming control unit obtains a crest point of the AC voltage waveform based on the zero cross point detected by the zero cross detection unit, and supplies the crest point to the plurality of LEDs based on the crest point. An LED lighting control device configured to modulate a pulse width of a voltage to be applied. An illuminance sensor that detects brightness around a place where the plurality of LEDs are installed is provided, and the dimming control unit determines a dimming level based on a detection output of the illuminance sensor, and sets the dimming level to the dimming level. The LED lighting control device according to claim 1, wherein the pulse width of the voltage supplied to the plurality of LEDs is modulated accordingly.

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