Lighting control system and method

• US 8,742,695 B2
• Filed: 05/24/2013
• Issued: 06/03/2014
• Est. Priority Date: 05/14/2012
• Status: Active Grant

• Current Assignee: USAI, LLC
• Original Assignee: USAI, LLC
• Inventors: Wray, Donald L.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US13/902,548
• Publication Number:
  US 20130300305A1
• Time in Patent Office: 375 Days
• Field of Search: 315/185.R, 315/191, 315/192, 315/193, 315/307, 315/308, 315/291, 315/224
• US Class Current: 315/307
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/3577 Emulating the dimming characteristics, brightness or colour temperature of incandescent lamps
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/395 Linear regulators
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A lighting system provides for independent control of both the brightness of an LED light fixture and the perceived color of the light emitted by the LED light fixture. The LED light fixture has two LED light sources, a control circuit alternately pulses the two LED light sources and changes relative duty cycles of the light sources to alter a perceived color output of the lighting fixture, in response to a change in a control signal from a controller. Duty cycles of the light sources are a function of the control signal and vary inversely. The LED light fixture also receives a control signal for controlling a current level provided to the LED light sources to independently control the brightness of the lighting system.

Claims

1. A method of operating a Light-Emitting Diode (LED) light, comprising:

supplying a current to a light source, the light source having first and second groups of light-emitting diodes (LEDs) and each group having at least one LED;

a controller receiving a timing signal having a period;

supplying a color control signal to the controller, the color control signal having a first signal level;

in response to the color control signal at the first signal level, the controller alternately pulsing the first and second groups of LEDs during the period, such that the first group of LEDs has a first duty cycle and the second group of LEDs has a second duty cycle during the period;

modifying the color control signal such that the color control signal has a second signal level different than the first signal level;

in response to modifying the color control signal, the controller alternately pulsing the first and second groups of LEDs during the period, such that the first group of LEDs has a third duty cycle different than the first duty cycle and the second group of LEDs has a fourth duty cycle different than the second duty cycle during the period;

the first and second duty cycles being a function of the color control signal at the first signal level, and the third and fourth duty cycles being a function of the color control signal at the second signal level; and

a change in the duty cycle of the first group of LEDs from the first duty cycle to the third duty cycle being inverse to a change in the duty cycle of the second group of LEDs from the second duty cycle to the fourth duty cycle.

2. The method of claim 1, wherein:

the color control signal comprises a voltage signal; and

the first signal level is a first voltage level and the second signal level is a second voltage level, wherein the second voltage level is different from the first voltage level.

3. The method of claim 1, comprising:

the first and second signal levels being within a first range of signal levels of the color control signal; and

throughout a second range of signal levels of the color control signal different than the first range, the controller illuminating the first group of LEDs for a duty cycle of 100 percent of the period of the timing signal and not illuminating the second group of LEDs during the period.

4. The method of claim 3, comprising:

throughout a third range of signal levels of the color control signal different than the first and second ranges, the controller illuminating the second group of LEDs for a duty cycle of 100 percent of the period of the timing signal and not illuminating the first group of LEDs during the period.

5. The method of claim 1, wherein:

the controller includes a first switch connected in series with the first group of LEDs and a second switch connected in series with the second group of LEDs; and

the controller controls the first switch according to a duty cycle of the first group of LEDs and controls the second switch according to a duty cycle of the second group of LEDs.

6. The method of claim 5, wherein the first and second switches each comprise a Field Effect Transistor (FET).

7. The method of claim 5, wherein the controller comprises an inverter buffer having at least a first, a second and a third inverting op amp connected in series, and the first switch is connected to an output of the second inverting op amp and the second switch is connected to an output of the third inverting op amp.

8. The method of claim 1, wherein:

in the step of modifying the color control signal, the color control signal is modified from the first signal level to the second signal level at a first rate of change; and

in response to the modification of the control signal, the controller causes the first and second groups of LEDs to transition from the first and second duty cycles to the third and fourth duty cycles respectively at a second rate of change that is slower than the first rate of change.

9. The method of claim 8, wherein the transition of the first and second groups of LEDs from the first and second duty cycles to the third and forth duty cycles respectively occurs in a smooth and continuous fashion.

10. The method of claim 9, further comprising providing a slide-type wall-mounted dimmer control, and in the step of modifying the color control signal, the dimmer control is moved from a first setting to a second setting.

11. The method of claim 1, further comprising the step of varying an intensity of the first and second groups of LEDs by varying the current supplied to the light source.

12. The method of claim 11, wherein the step of varying the current supplied to the light source is performed by adjusting a setting of a dimmer.

13. The method of claim 12, wherein the dimmer comprises a slide-type wall-mounted dimmer control.

14. A Light-Emitting Diode (LED) light system, comprising:

an LED light source having a first group of LEDs and a second group of LEDs;

a current source for providing an electrical current to the first and second groups of LEDs;

a brightness control operable to generate a brightness control signal for setting a brightness level of the LED light source;

a color control operable to generate a color control signal to set a color output of the LED light source;

a signal generator operable to generate a timing signal having a period;

a controller coupled to the signal generator, the color control and the LED light source;

the color control being operable, at a first setting, to generate a first color control signal for selecting a first color of the LED light source;

in response to the first color control signal, the controller being operable to alternately pulse the first and second groups of LEDs during the period of the timing signal, such that the first group of LEDs has a first duty cycle and the second group of LEDs has a second duty cycle during the period;

the color control being operable, in a second setting, to generate a second color control signal for selecting a second color the LED light source;

in response to the second control signal, the controller being operable to alternately pulse the first and second groups of LEDs during the period, such that the first group of LEDs has a third duty cycle different than the first duty cycle and the second group of LEDs has a fourth duty cycle different than the second duty cycle during the period;

wherein the first and second duty cycles are a function of the color control signal at the first signal level, and the third and fourth duty cycles are a function of the color control signal at the second signal level; and

wherein a change in the duty cycle of the first group of LEDs from the first duty cycle to the third duty cycle is inverse to a change in the duty cycle of the second group of LEDs from the second duty cycle to the fourth duty cycle.

15. The LED light system of claim 14, further comprising:

a resistor;

a capacitor; and

a first op amp having an inverting and a non-inverting input;

where the color control is coupled to the inverting input of the first op amp through said resistor and the inverting input of the first op amp is connected to ground through said capacitor.

16. The LED light system of claim 14, further comprising:

a first switch coupled in series with said first group of LEDs;

a second switch coupled in series with said second group of LEDs;

the first and second switches comprise Field Effect Transistors (FETs);

the controller comprises first, second and third inverting op amps;

the first inverting op amp having an input coupled to an output of the first op amp;

the second inverting op amp having an input coupled to an output of the first inverting op amp;

the third inverting op amp having an input coupled to an output of the second inverting op amp;

said first FET having a gate coupled to the output of said second inverting op amp; and

said second FET having a gate coupled to the output of said third inverting op amp.

17. The LED light system of claim 14, further comprising:

a plurality of LED light fixtures are connected in parallel to the color control, and each of the LED light fixtures having a circuit protector coupled to the color control; and

in the event of a failure of one of the plurality of LED light fixtures, the circuit protector of each the other LED light fixtures being operable to block voltage from feeding from the one LED light fixture.

18. A Light-Emitting Diode (LED) lighting system, comprising:

a light source having first and second groups of light-emitting diodes (LEDs) and each group having at least one LED;

a controller coupled to the light source for controlling the first and second groups of LEDs;

a signal generator coupled to the controller, the signal generator being operable to generate a timing signal for the controller, the timing signal having a period;

a color control coupled to the controller, the color control being operable to generate a variable color control signal including within a first signal range defined by a high signal level and a low signal level that is lower than the high signal level; and

when the color control signal is within the first signal range, the controller being operable to alternately pulse the first and second groups of LEDs during the period and to vary respective duty cycles of the first and second groups of LEDs inversely, as a function of the color control signal, between zero (0) percent and one-hundred (100) percent of the period.

19. The lighting system of claim 18, comprising:

the color control being operable to generate the color control signal within a second signal range different than the first signal range, where the second signal range is defined by the high signal level and a maximum signal level greater than the high signal level; and

throughout the second signal range, the controller being operable to illuminate the first group of LEDs for a duty cycle of 100 percent of the period and to not illuminate the second group of LEDs during the period.

20. The lighting system of claim 19, comprising:

the color control being operable to generate the color control signal within a third signal range different than the first and second signal ranges, where the third signal range is defined by the low signal level and a minimum signal level lower than the low signal level; and

throughout the third signal range, the controller being operable to illuminate the second group of LEDs for a duty cycle of 100 percent of the period and to not illuminate the first group of LEDs during the period.

21. The lighting system of claim 20, wherein:

the color control comprises a slide-type wall-mounted dimmer control; and

the color control signal comprises a varying voltage signal such that the first, second and third signal ranges comprise middle, high and low voltage ranges, respectively, of the color control signal.

22. The lighting system of claim 18, comprising, throughout the first signal range, the controller being operable to vary the duty cycles of the first and second groups of LEDs according to an analog function.

23. The lighting system of claim 18, comprising, throughout the first signal range, the controller being operable to vary the duty cycles of the first and second groups of LEDs substantially continuously.

24. The lighting system of claim 18, comprising, throughout the first signal range, the controller being operable to vary the respective duty cycles of the first and second groups of LEDs such that a sum of the respective duty cycles remains equal to 100 percent of the period of the timing signal.

25. The lighting system of claim 18, comprising the first group of LEDs being operable to produce white light and the second group of LEDs is operable to produce light having a different color than white.

26. The lighting system of claim 18, comprising the light source and the controller being housed within a retro-fit bulb having a standard base selected from a group consisting of an Edison screw base, a double-contact bayonet base, and a bi-pin base.

27. The lighting system of claim 18, comprising, in response to a change in the color control signal at a first rate, the controller being operable to change the duty cycles of the first and second group of LEDs at a second rate slower than the first rate.

28. The lighting system of claim 27, comprising a low-pass filter coupled to the color control and the controller.