Patent ID: 7703943

Claim:
A color tunable light source comprising: a first light emitting diode arrangement operable to emit light of a first color; a second light emitting diode arrangement operable to emit light of a second color, the light emitting diode arrangements being configured such that their combined light output comprises the output of the source, wherein the first light emitting diode arrangement comprises a phosphor provided remote to an associated first light emitting diode that is operable to generate excitation light of a selected wavelength range and to irradiate the phosphor such that the phosphor emits light of a different color, wherein light emitted by the first light emitting diode arrangement comprises the combined light from the first light emitting diode and the light emitted from the phosphor; and control means operable to control the color of light emitted by the source by controlling the ratio of intensity of light emitted by the first and second light emitting diode arrangements, the control means comprising a pulse width modulated power supply operable to generate a pulse width modulated drive current and wherein the first and second light emitting diode arrangements are operable on opposite phases of the pulse width modulated drive current and the color of light emitted by the source is controllable by a duty cycle of the drive current.