CURRENT FEEDBACK FOR IMPROVING PERFORMANCE AND CONSISTENCY OF LED FIXTURES

• US 20160029455A1
• Filed: 03/05/2014
• Published: 01/28/2016
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: AYDIN, Tarek
• Granted Patent: US 9,894,725 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/18 using temperature feedback
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

A lighting system includes a power converter connected to mains voltage and configured to provide a driving current responsive to a control signal. A voltage measurement circuit is configured to provide a voltage sense signal indicative of an amplitude of the mains voltage. A light-emitting diode (LED) module includes at least one string of LEDs that emit light responsive to the driving current, and is configured to detect an LED current through the at least one string and output a current feedback signal indicative of the detected LED current. A driver controller is configured to output the control signal responsive to the voltage sense signal and the current feedback signal.

Claims

1. A lighting system comprising:

power converter connected to mains voltage and configured to provide a driving current responsive to a control signal;

a voltage measurement circuit configured to provide a voltage sense signal indicative of an amplitude of the mains voltage;

a light-emitting diode (LED) module comprising a plurality of strings of LEDs that emit light responsive to the driving current, and configured to detect respective LED currents through each of the strings and output a current feedback signal indicative of the detected respective LED currents; and

a driver controller configured to output the control signal responsive to the voltage sense signal and the current feedback signal, wherein the power converter is configured to output respective driving currents to the strings responsive to the voltage sense signal and the current feedback signal indicative of the detected respective LED currents.

2. The lighting system of claim 1, wherein the LED module comprises:

an amplifier connected to the at least one string, and configured to amplify the LED current and provide the amplified LED current as a detected LED current; and

an analog to digital converter configured to convert the detected LED current into a digital signal and output the digital signal as the current feedback signal.

3. The lighting system of claim 2, wherein the LED module further comprises:

an optical isolator connected between the analog to digital converter and the driver controller, and configured to enable transmission of the digital signal from the analog to digital converter to the driver controller as the current feedback signal; and

a local voltage source connected to the power converter, and configured to provide a local voltage to the amplifier, the analog to digital converter and the optical isolator.

4. The lighting system of claim 3, wherein the power converter comprises a buck power converter.

5. The lighting system of claim 3, wherein the analog to digital converter comprises a 12-bit analog to digital converter, and the optical isolator comprises a digital I2C opto-coupler.

6. The lighting system of claim 2, wherein the power converter and the driver controller have non-isolated ground references, and the digital signal from the analog to digital converter is output directly from the LED module as the current feedback signal to the driver controller.

7. The lighting system of claim 1, wherein the control signal comprises a pulse-width modulated (PWM) signal or an analog signal, the lighting system further comprising:

a power controller connected to the driver controller, and configured as responsive to the control signal to control the power converter to output the driving current so as to maintain the LED current at a selected constant level.

8. The lighting system of claim 7, wherein the power controller comprises a power factor correction chip disposed within the power converter.

9. The lighting system of claim 1, further comprising:

a dimmer connected to the mains voltage and configured to modify a phase of the mains voltage provided to the power converter to adjustably dim the light emitted by the LED module; and

a dimmer measurement circuit connected to the dimmer, and configured to output a dimmer sense signal responsive to a detected modified phase of the mains voltage,

wherein the driver controller is configured to output the control signal further responsive to the dimmer sense signal.

11. The lighting system of claim 1, wherein the LED module further comprises:

a microcontroller configured to output a digital signal comprising the current feedback signal, an LED voltage feedback signal indicative of a voltage across the at least one string and an LED temperature feedback signal indicative of a temperature of the LEDs within the at least one string, wherein the driver controller is configured to output the control signal further responsive to the LED voltage feedback signal and the LED temperature feedback signal.

12. The lighting system of claim 1, wherein the mains voltage comprises AC mains voltage within a range of about 90 volts AC to 480 volts AC.

13. The lighting system of claim 1, wherein the driver controller is configured to provide the control signal so as to maintain the LED current at a selected constant level.

10. (canceled)

14. A lighting driver comprising:

a power converter connected to mains voltage and configured to provide a driving current to a solid state lighting load responsive to a control signal;

a voltage measurement circuit configured to provide a voltage sense signal indicative of an amplitude of the mains voltage; and

a driver controller configured to output the control signal responsive to the voltage sense signal and a current feedback signal indicative of a lighting current through the solid state lighting load, wherein the power converter provides the driving current to maintain the lighting current at a selected constant level regardless of the amplitude of the mains voltage.

15. The lighting driver of claim 14, wherein the current feedback signal is indicative of a lighting current through at least one string of a plurality of light emitting diodes (LEDs) within the solid state lighting load.

16. The lighting driver of claim 15, wherein the driver controller is configured to output the control signal further responsive to an LED voltage feedback signal indicative of a voltage across the at least one string and an LED temperature feedback signal indicative of a temperature of the LEDs within the at least one string.

17. The lighting driver of claim 14, further comprising:

a dimmer connected to the mains voltage and configured to modify a phase of the mains voltage provided to the power converter to adjustably dim the light emitted by the solid state lighting load; and

a dimmer measurement circuit connected to the dimmer, and configured to output a dimmer sense signal responsive to a detected modified phase of the mains voltage,

wherein the driver controller is configured to output the control signal further responsive to the dimmer sense signal.

18. The lighting driver of claim 14, wherein the control signal comprises a pulse-width modulated (PWM) signal or an analog signal, the lighting driver further comprising:

a power factor correction chip connected to the driver controller, and configured as responsive to the control signal to control the power converter to output the driving current so as to maintain the lighting current at the selected constant level.

19-21. -21. (canceled)

22. A method of controlling a solid state lighting load, the method comprising:

converting mains voltage to provide a driving current to the solid state lighting load;

generating a current feedback signal indicative of a lighting current through the solid state lighting load; and

detecting an amplitude of the mains voltage,

wherein said converting comprises providing the driving current to maintain light emitted from the solid state lighting load at a selected constant brightness responsive to the detected amplitude of the mains voltage and the current feedback signal.

23-25. -25. (canceled)