Communications: electrical – Visual indication – Using light emitting diodes
Reexamination Certificate
1999-02-19
2001-05-22
Lieu, Julie (Department: 2736)
Communications: electrical
Visual indication
Using light emitting diodes
C340S815400, C340S907000, C340S909000, C340S916000, C340S931000, C362S800000
Reexamination Certificate
active
06236331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to LED traffic lights, more particularly to LED traffic light intensity controllers.
2. Background of the Invention
Traditionally, traffic lights have used light bulbs in order to produce light. A colored filter was installed in front of each bulb for giving one of the three traffic lights common colors. However, traffic lights using this technology have many drawbacks: the bulbs power consumption is high (each being between 100 W and 150 W), thus increasing the operation costs, the bulb lifetime is short and decreases with environmental conditions. For example, a light bulb's lifetime decreases with vibrations and temperature.
In recent years, LED panel arrays were proposed for replacing traditional light bulbs for traffic light applications. Recent technologies that have been developed allow the generation of all the three colors needed in such an application (red, yellow and green). An LED traffic light uses only a fraction of the electrical power a light bulb traffic light used and is thus less expensive for long term use. However, LEDs employed for making up the array have a limited lifetime and their output light intensity also decreases with time. After a period of time, the total light intensity of a color (e. g. the traffic light red color) may drop below the standard minimum intensity required in order to insure traffic safety.
LED traffic lights are also sensitive to vibrations and shocks. Therefore, current technologies using LEDs in order to replace standard traffic light bulbs are neither reliable enough nor cost-efficient for being widely implemented.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an LED traffic light electronic controller for stabilizing the total output light intensity of such a traffic light in order to insure a constant light intensity of each traffic light color throughout the entire traffic light lifetime. The controller detects the output light intensity of a color, and then automatically adjusts the power input for the LEDs in order to increase the light intensity when needed. The controller works in a closed loop cycle in order to perform real-time control of the light intensity output Thus, at each moment of the traffic light lifetime, the output light intensity is constant and equivalent to a predetermined standard. This insures traffic safety for the entire traffic light lifetime and also make it last longer.
Such a controller allows the LED traffic light to be more cost-efficient than standard traffic light bulbs. It insures above standard light intensity output for longer lifetime and does this using only 14 watts to 30 watts per color comparing to 100 watts to 150 watts for standard traffic lights.
It is another object of the present invention to provide the electronic controller completely encapsulated in an exothermic polymer compound. In this manner, each and every part of the controller is firmly fixed in a polymer block that eliminates any chance for that part to be removed from its place. The controller is thus protected against violent vibrations, shocks and failure due to dust and moisture intrusions that commonly affect circuit boards.
It is also an object of the present invention to provide a traffic light intensity controller that automatically puts out of service the traffic light at the end of its lifetime, by detecting an end-of-life sign, such as a too low light intensity output of the LEDs, a particular amount of time expired since the installing date or a too high electric current being fed to the LED matrix. When such a condition occurs, the traffic light controller may also send a failure signal to a traffic light emergency controller, which is a standard controller available on most traffic lights, so the emergency controller may switch the traffic light into an emergency mode, such as a blinking red light mode.
In another preferred embodiment of the present invention, the traffic light intensity controller also comprises an alternative load circuit that is powered alternatively with the LED matrix, i.e. when the LED matrix is turned off the alternative load is on, so the traffic light emergency circuit always detects a closed circuit, even when the light is off, and does not switches the traffic light to the emergency mode.
In a further preferred embodiment, the invention provides a controller for dimming the LED intensity at night, while providing maximum intensity during the brightest hours. Preferably, this is achieved using a photocell detecting ambient light conditions, although other ways such as a time of day circuit could be used.
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Anglehart James
Lieu Julie
Newled Technologies Inc.
Swabey Ogilvy Renault
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