Patent ID: 7777166
Filing Date: 2010-08-17
Classification: F21K,F21V,F21Y,G01D,G01J,G09F,G09G,H04N

Abstract:
1. A luminaire, comprising: a lighting panel including at least one tile and having a principal plane, at least a first string of solid state lighting devices on a first side of the at least one tile and configured to emit light at a first dominant wavelength and a second string of solid state lighting devices on the first side of the at least one tile and configured to emit light at a second dominant wavelength, different from the first dominant wavelength, a reflector sheet on the first side of the at least one tile, and a brightness enhancement film on the reflector sheet, wherein the reflector sheet is arranged between the at least one tile and the brightness enhancement film, and wherein the reflector sheet and the brightness enhancing film both extend in parallel to the principal plane of the lighting panel; a first current supply circuit configured to supply an on-state drive current to the first string in response to a first control signal; a second current supply circuit configured to supply an on-state drive current to the second string in response to a second control signal; a photosensor arranged to receive light from at least one solid state lighting device in the first string and at least one solid state lighting device in the second string; and a control system configured to receive an output signal from the photosensor and to adjust the first control signal and/or the second control signal responsive to the output signal of the photosensor to thereby adjust an average current supplied to the first string by the first current supply circuit and/or to adjust an average current supplied to the second string by the second current supply circuit, such that the photosensor, the control system and the first and second current supply circuits thereby form a feedback loop for the lighting panel; wherein the first and second control signals comprise pulse width modulation (PWM) signals, and wherein the control system is configured to control an average current supplied to the first and/or second string by varying a duty cycle of the first and/or second control signal, wherein the first and second strings of solid state lighting devices are energized in response to the first and second control signals to emit combined light having a color that is a combination of light emitted by the first string of solid state lighting devices and the second string of solid state lighting devices, and wherein the control system is configured to cause a leading edge of a pulse of the first control signal to occur at a different time from a leading edge of a pulse of the second control signal.