LONG LIFE, FAIL SAFE TRAFFIC LIGHT

• US 20140368111A1
• Filed: 06/18/2013
• Published: 12/18/2014
• Est. Priority Date: 06/18/2013
• Status: Active Grant

• Current Assignee: Dialight Corporation (Dialight PLC)
• Original Assignee: Dialight Corporation (Dialight PLC)
• Inventors: Hebborn, Kevin A., Zingler, Glenn J.
• Granted Patent: US 9,578,728 B2
• Time in Patent Office: Days
• US Class Current: 315/76
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: G08G 1/095 Traffic lights
• CPC Class Codes: H05B 41/2921 for protecting the circuit against abnormal operating conditions
• CPC Class Codes: H05B 41/2923 against abnormal power supply conditions
• CPC Class Codes: H05B 41/2925 against abnormal lamp operating conditions
• CPC Class Codes: H05B 41/2926 against internal abnormal circuit conditions
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 45/58 involving end of life detection of LEDs
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

The present disclosure is directed to a method for detecting a failure in a signal light. In one embodiment, the method includes monitoring operation of one or more light emitting diodes (LEDs) of the signal light coupled to a constant current driver, detecting a short circuit in at least one of the one or more LEDs and signaling a failure in the signal light when the short circuit is detected.

Claims

1. A method for detecting a failure in a signal light, comprising:

monitoring operation of one or more light emitting diodes (LEDs) of the signal light coupled to a constant current driver;

detecting a short circuit in at least one of the one or more LEDs; and

signaling the failure in the signal light when the short circuit is detected.

2. The method of claim 1, wherein the detecting the short circuit comprises:

setting a voltage threshold for the signal light;

measuring a voltage across the one or more light emitting diodes (LEDs) of the signal light;

comparing the voltage to the voltage threshold; and

determining the short circuit has occurred when the voltage falls below the voltage threshold.

3. The method of claim 2, wherein the setting the voltage threshold comprises programming a programming resistor.

4. The method of claim 1, the signaling comprises:

placing the signal light in a high impedance state.

5. The method of claim 4, wherein placing the signal light in the high impedance state comprises blowing a fuse.

6. The method of claim 4, wherein placing the signal light in the high impedance state comprises shutting off a current flow to the one or more LEDs.

7. The method of claim 1, wherein the detecting is performed by a controller.

8. The method of claim 1, wherein the detecting is performed by a circuit on an LED board of one of the one or more LEDs.

9. The method of claim 1, wherein the detecting is performed by an external circuit added to a circuit of the signal light.

10. A light signal circuit comprising:

an AC to direct current (AC-DC) converter for coupling to an AC power supply;

a controller in communication with the AC-DC converter;

one or more LEDs coupled to the AC-DC converter;

an under-current and under voltage sensing circuit coupled to the one or more LEDs; and

a failed state impedance circuit coupled to the under current and under voltage sensing circuit and the control circuit.

11. The light signal circuit of claim 10, wherein the under current and the under voltage sensing circuit comprises:

a first programming resistor to set a current threshold; and

a second programming resistor to set a voltage threshold.

12. The light signal circuit of claim 11, wherein the failed state impedance circuit goes into a high impendence state when a measured voltage across the one or more LEDs is below the voltage threshold.

13. The light signal circuit of claim 12, wherein the failed state impedance circuit goes into a high impendence state by blowing a fuse in the failed state impedance circuit.

14. The light signal circuit of claim 10, wherein the AC-DC converter comprises at least one non-electrolytic capacitor.

15. The light signal circuit of claim 10, further comprising:

one or more terminals for connecting to a thermistor or a resistor mounted on each one of the one or more LEDs to set an output current that is compatible with the one or more LEDs.

16. An alternating current to direct current (AC-DC) converter for driving one or more light emitting diodes (LEDs) of a signal light, comprising:

a first diode;

a first inductor coupled to the first diode;

a first capacitor coupled to the first inductor, wherein the first capacitor comprises a non-electrolytic capacitor;

a second diode coupled to the first capacitor and the first diode, wherein the first diode, the first inductor, the first capacitor and the second diode comprise a first loop; and

a switch coupled to the first loop.

17. The AC-DC converter of claim 16, further comprising a buck stage loop coupled to the first loop.

18. The AC-DC converter of claim 17, wherein the buck stage loop comprises:

a third diode;

a second inductor coupled to the third diode;

a second capacitor coupled to the second inductor; and

a fourth diode coupled to the second capacitor, the third diode and the second inductor.

19. The AC-DC converter of claim 16, wherein the switch comprises a transistor.

20. The AC-DC converter of claim 19, wherein the transistor comprises a bipolar transistor or a metal oxide semiconductor field effect transistor (MOSFET).