LED traffic light intensity controller

• US 6,236,331 B1
• Filed: 02/19/1999
• Issued: 05/22/2001
• Est. Priority Date: 02/20/1998
• Status: Expired due to Fees

• Current Assignee: Newled Technologies Incorporated
• Original Assignee: Newled Technologies Incorporated
• Inventors: Dussureault, Guy
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US09/252,789
• Time in Patent Office: 823 Days
• Field of Search: 340/815.45, 340/815.4, 340/907, 340/909, 340/916, 340/931, 362/800, 315/131, 315/158
• US Class Current: 340/815.45
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

The LED traffic light electronic controller stabilizes the total output light intensity of the traffic light in order to ensure 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. The controller also provides a ballast load when off, and is able to provide an open circuit when the LEDs have exhausted their useful lifespan. The intensity is further controlled by detecting ambient light conditions.

Claims

1. An LED traffic light panel comprising:

an array of LEDs having a similar performance to one another which performance decays over an extended period of operational time;

a variable power supply connected to said array of LEDs;

an extra LED having also a similar performance to said LEDs of said array;

a light detector optically coupled to said extra LED; and

a controller circuit for adjusting said variable power supply in response to an output of said light detector, whereby an output light intensity of the traffic light panel is stabilized over the life of said LEDs in order to insure a constant light intensity of each traffic light color throughout the entire traffic light panel lifetime.

2. The light panel as claimed in claim 1, further comprising:

said power supply receives a power signal from a traffic light controller unit; and

a circuit responsive to a voltage supplied to said array of LEDs for disconnecting a load from said power signal when said voltage indicates that said array of LEDs have a performance which has decayed to a predetermined limit, such that said power signal will meet an open circuit at said panel,

whereby said traffic light controller unit recognizes the traffic light panel as “

burnt out”

once the performance has decayed to said limit.

3. The light panel as claimed in claim 1, wherein:

said power supply receives a power signal from a traffic light controller unit; and

said controller circuit also detects said power signal and connects a shunt load to said power signal when said power signal is in an off-state and disconnects said shunt load when said power signal is in an on-state, whereby said controller unit will not detect an open circuit when in an off-state and thus disable the traffic light.

4. The light panel as claimed in claim 2, wherein:

said controller circuit also detects said power signal and connects a shunt load to said power signal when said power signal is in an off-state and disconnects said shunt load when said power signal is in an on-state, whereby said controller unit will not detect an open circuit when in an off-state and thus disable the traffic light.

5. The light panel as claimed in claim 1, wherein:

said array of LEDs are mounted to one side of a board;

said power supply, said extra LED, said light detector, and said controller circuit are mounted to another side of said board; and

said LEDs, said power supply, said extra LED, said light detector, and said controller circuit being completely encapsulated in a transparent polymer compound.

6. The light panel as claimed in claim 5, wherein said polymer compound is exothermic.

7. The light panel as claimed in claim 1, further comprising means for generating a light intensity signal by detection of at least one of time of day and ambient light, wherein said controller circuit further adjusts said variable power supply in response to said light intensity signal.

8. The light panel as claimed in claim 2, further comprising means for generating a light intensity signal by detection of at least one of time of day and ambient light, wherein said controller circuit further adjusts said variable power supply in response to said light intensity signal.

9. The light panel as claimed in claim 3, further comprising means for generating a light intensity signal by detection of at least one of time of day and ambient light, wherein said controller circuit further adjusts said variable power supply in response to said light intensity signal.

10. The light panel as claimed in claim 1, further comprising:

a light sensitive device arranged to receive ambient light and generate a light intensity signal;

wherein said variable power supply is responsive to said intensity signal and connected to said array of LEDs for adjusting a brightness of said LEDs depending on said ambient light.

11. An LED traffic light panel comprising;

an array of LEDs;

a power supply receiving a power signal from a traffic light controller unit and supplying power to said array of LEDs, said power supply having an impedance which appears as an open circuit to said controller unit when said power signal is in an off-state; and

a controller circuit for detecting said power signal and connecting a shunt load to said power signal when said power signal is in an off-state and disconnecting said shunt load when said power signal is in an on-state, whereby said controller unit will not detect an open circuit when in an off-state and thus disable the traffic light.