JPH0146920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to signal lamp devices such as traffic lights and traffic signs, and particularly relates to a colored signal lamp device with low power consumption, high brightness, and long life.

Conventional colored traffic light devices use incandescent light bulbs as light emitters, and use color filters such as colored glass to extract only light of desired wavelengths. It is a well-known fact that incandescent light bulbs have low light conversion efficiency, and because the target wavelength of light uses only a portion of the wavelength of light emitted by incandescent light bulbs, conventional The effective power efficiency of colored signal lights is very low. Furthermore, when the external illuminance changes significantly, in order to obtain the effect of a signal lamp, the brightness of the signal lamp must be determined based on the maximum external illuminance. Therefore, in the case of a signal light installed outdoors, such as a colored road signal light, for example, the brightness of the signal light is determined based on the brightest daytime illuminance. However, at night, the illuminance of the outside world drops significantly, so signal lights that have the same brightness as during the daytime display an unnecessarily bright display, wasting power. However, when trying to reduce power consumption at night using conventional signal lights, another problem arises. That is, since an incandescent light bulb is a light emitting body that uses heat radiation, when the same light bulb is used and the power supply is reduced, the temperature of the light body changes and the emission spectrum changes. When the temperature of the light emitting body decreases, the peak wavelength of light emission shifts to the longer wavelength (infrared) side, and the light emission intensity on the shorter wavelength side decreases sensitively. Therefore, as the efficiency in the visible light region decreases, the emitted light becomes colored. Signal lights display red, yellow, and green (or blue), and if one or two of the three colors cannot be distinguished, the significance of the signal light is halved. Therefore, even if the display functions sufficiently even if the brightness is lowered, as long as the same light emitting body is used, it is not possible to significantly reduce power consumption and perform display at a lower brightness. A solution to this problem would be to use multiple light emitters with different power ratings, but in this case, problems would arise in adjusting the focus and direction of light diffusion, and the equipment would become larger and more expensive. It has the disadvantage of being stored away.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal light device that responds to the brightness of the outside world, has a necessary level of brightness, and consumes little reactive power.

A light-emitting diode has an emission wavelength unique to the semiconductor used, and since light emission depends on the disappearance of carriers, the emission intensity has a property that it is approximately proportional to the forward current. The power efficiency of light emitting diodes has improved significantly in recent years, and has come to far exceed the luminous efficiency of incandescent light bulbs. Furthermore, since no unnecessary wavelength light is emitted for colored display, the effective efficiency is further increased. Furthermore, since the luminance of light emission is approximately proportional to the current value, brightness adjustment using the current value is easy.

Figures 1a and 1b schematically illustrate the principle of the present invention.
In FIG. 1a, a current supplied from a commercial power source 1 is supplied to a light emitting diode array 3 via a photoresponse control circuit 2. In FIG. The light response control circuit 2 supplies an output current corresponding to the incident light. This current may be direct current or alternating current, but it increases as the incident light intensity increases,
It decreases as it decreases. In FIG. 1b, a reversely oriented light emitting diode array 3' is also connected, so that the diode array 3 is illuminated during one half cycle of the commercial frequency and the diode array 3' is illuminated during the other half cycle. In the case of the configuration shown in FIG. 1b, current control is performed by each diode string 3,
3' may be carried out in common or separately.
When several light emitting diode columns are connected in parallel, it is preferable that each column is provided with a constant current circuit or a current limiter to prevent overcurrent. These can also be included in the control circuit 2.

FIG. 2 shows the structure of a light emitting part of a traffic signal light device using light emitting diodes. The configuration for one lamp is illustrated here.

The light emitting portion 10 for one color has an area of approximately 20 cmφ, similar to a normal three-color traffic signal light. A large number of semiconductor light emitting diodes 11,
12, 13... are arranged. The light emitting diode is a red, yellow or green light emitting diode corresponding to the display color. For example, a red light contains Ga _0.7 Al _0.3
Use red light emitting diodes such as As, GaAs _0.7 P _0.3 , etc. for yellow lights, yellow light emitting diodes such as In _0.4 Ga _0.6 P, Al _0.4 In _0.6 PGaP:N, etc. for green lights, and GaP, In _0.2 for green lights.
A green light emitting diode such as Ga _0.8 P is used. The operating voltage of a light emitting diode is at most 1.5~ per piece.
Since the voltage is 4V, it is best to connect an appropriate number of diode strings in series to match the power supply voltage. Further, since the applied voltage, efficiency, etc. usually differ depending on the emission wavelength, it is preferable to take the optimum diode arrangement for each color. Since the area occupied by each diode is usually about 1 to 5 mmφ, the diode arrangement can be designed almost arbitrarily.

In the case of red lights, GaAsP light emitting diodes (for example, NEC SR101C) are used as unit light emitting cells.
A. Good display is obtained by supplying a current of 5 to 15 mA at night. Similarly, when 150 GaAlAs light emitting diodes are used, a current of 5 mA per unit diode is supplied, which is 5 to 10 mA more than a conventional signal light.
Get a twice as bright display. In this way, compared to conventional signal lights, it is possible to obtain the same or brighter display with significantly less power, and to reduce the power consumption at night to about 1/5 of the power consumption during the day. can. Furthermore, in the case of a three-color display signal light, the red display is particularly important, but by using light emitting diodes, it is easy to make only the red display brighter than the other color displays without making any major structural changes. Also, to perform 3-color display, 3
There is no need to use a lamp type, and one lamp can easily display three colors. Next, a circuit for controlling the current supplied to the light emitting diode according to the brightness of the outside world will be explained with reference to FIG.

The phototransistor _Q1 , the transistor _Q2 connected to _Q1 in a Darlington manner, and the load resistor R form a preamplifier 5 that responds to the amount of incident light. The output V _io of the preamplifier is supplied to a variable power supply section 6 including a differential amplifier AMP, a comparison voltage source V _ref , and a negative feedback impedance Z. The differential amplifier AMP compares the comparison voltage V _ref with the input voltage V _io from the front stage amplifier 5 and supplies a current corresponding to the brightness of the outside world to the diode 3 of the light emitting section. Switching circuits for changing display colors and the like are omitted.

The circuit constants can be adjusted by adjusting the comparison voltage V _ref and the negative feedback impedance Z. In this way, in the example shown in FIG. 3, the current can be continuously controlled in proportion to the brightness of the outside world, and the amount of light can be continuously adjusted. For signal lights that have approximately the same external conditions, such as a signal light at one intersection (or a certain area) on a road, it is easy to share the control circuit, especially the optical response front-stage amplifier 5. On the other hand, when the external conditions vary greatly even for signal lights at the same point due to directions, etc., it is preferable to control only those with similar external conditions using the same control circuit. Those skilled in the art will easily be able to add power amplification stages depending on the required output in cases such as centralized control. The power required per unit signal light is approximately 60
Compared to ~150W, the device using the light emitting diode of the present invention can reduce the power consumption to several watts or less. As is clear from the above explanation, the power consumption is greatly reduced, and during nighttime, the power consumption can be further reduced to a fraction of that. There is great potential for further improvement in the luminous efficiency of light-emitting diodes, and even greater power reductions can be expected by using the light-emitting directional properties of light-emitting diodes. Obtainable.

In the embodiment shown in FIG. 3, the control circuit is somewhat complicated. FIG. 4 shows a simple structure suitable for supplying large amounts of power.

In this embodiment, the display diode is divided into two diode groups 8 and 9. The control circuit 5' connects and disconnects the output current in response to the brightness of the outside world. When the outside world is bright, the control circuit 5' supplies an output current and closes the relay 7. When the relay 7 closes, the diode group 8 of the light emitting section is connected to the power source E ₂
connected to. The diode group 9 of the light emitting section is always connected to the power source _E1 . The power source E ₁ and the power source E ₂ may be the same or may be AC power sources.
The switch SW is a light emitting/disconnecting switch for a signal light.

In this way, both diode groups 8 and 9 can be turned on when the outside world is bright, and only one diode group 9 can be turned on when the outside world is dark.
Particularly effective display can be achieved at nightfall by dividing the external light-emitting unit into a plurality of parts and setting different threshold values for each part. As described above, in the example shown in FIG. 4, the light is dimmed by performing binary control of a high current value and a low current value by comparing the brightness with the reference brightness of the outside world. It is preferable that the light emitting diode be driven with alternating current, but in the case of alternating current driving, it does not emit light for at least half a cycle. FIG. 5 shows a diode array that is AC driven and has almost no extinction period. The diodes in one indicator light are divided into a diode group 21, 22 of one polarity and a diode group 31, 32 of the other polarity, which are turned on alternately every half a period of lighting.

The control circuit 25 changes the output current depending on the brightness of the outside world.

The control circuit that changes the output current in response to the brightness of the outside world is not limited to the structure shown in FIG. For example, the differential amplifier may be driven by a single phototransistor instead of the Darlington connection, or the differential amplifier may be omitted.

FIG. 6 shows another example of a circuit in which the light emitting section is driven with alternating current. In this circuit, the SCR is driven by the output voltage of the phototransistor, and the light emitting diode 21,
The current flowing through 22 is controlled. Furthermore, full-wave driving may be performed by connecting a light emitting diode and an SCR in parallel with each other in a similar configuration with opposite polarities.

Considering compatibility with the signal lamp device currently in use, it is recommended that at least the light emitting part be AC driven and the applied voltage set to about 100 to 200V.
The light detection section can also be driven by alternating current.

For example, in the circuit shown in FIG. 6, the voltage terminal +V may be connected to the other end of the AC power source via an adjusting variable resistor. Throughout the above embodiments, the display switching (connection/disconnection) circuit for the signal light is omitted from the drawings, but combinations of the illustrated circuits and these circuits will be obvious to those skilled in the art.

As explained above, the present invention is a signal light device that includes a semiconductor light emitting diode for displaying and a variable current source that supplies an output current to the light emitting diode in response to the brightness of the outside world, and which saves power. The goal is to achieve the following. Furthermore, high brightness display, miniaturization of the display section, and long life of the device can be achieved.

[Brief explanation of drawings]

1a and 1b are schematic circuit diagrams for explaining the principle of the present invention, FIG. 2 is a schematic plan view of a light emitting part used in the present invention, and FIG. 3 is a signal light according to an embodiment of the present invention. Partial circuit diagram of the device, Figure 4,
5 and 6 are partial circuit diagrams of a signal light device according to an embodiment of the present invention, respectively. In the figure, 10...light emitting part of the signal lamp device, 3, 3', 8, 9, 11, 12, 13, 21,
22, 31, 32... Light emitting diode, 2, 2
5, 5, 6, 5', 7, Q ₁ , SCR...variable current source.

Claims (1)

[Scope of Claims] 1. A signal light device comprising a first light emitting diode group 8, a second light emitting diode group 9 that emits light at a constant brightness, and current control circuits 5, 6, 5', 25. , the first light emitting diode group 8 and the second light emitting diode group 9 constitute a signal display section, and at least one of these two groups includes light emitting diodes 21, 31, 22, 32 of opposite polarity. are provided as a pair and driven by an alternating current, and the output of the current control circuit is connected to the first light emitting diode group 8 to adjust the luminance of the first light emitting diode group 8 to the outside world. 1. A signal light device that performs variable control according to the brightness of the signal light.