Patent ID: 9504115
Filing Date: 2016-11-22
CPC Classification: H05B,Y02B

Claim Text:
1. Light source circuitry comprising: a first group of one or more light emitting diodes configured to emit light of a first color; a second group of one or more light emitting diodes configured to emit light of a second color; a third group of one or more light emitting diodes configured to emit light of a third color, wherein the first, second and third groups of light emitting diodes are configured such that, when a fixed current arrives at the light source circuitry, the fixed current is shared between the first, second and third groups; a first transistor connected in series with the first group of light emitting diodes; and a second transistor connected in series with the second group of light emitting diodes, wherein the first transistor and second transistor are configured such that a variation in a single received control signal causes a variation in a first proportion of the fixed current that flows through the first transistor and causes a variation in a second proportion of the fixed current that flows through the second transistor, such that the proportions of the fixed current that flow through each of the first and second groups is controllable in dependence on the single received control signal and such that the remainder of the fixed current flows through the third group; wherein the light source circuitry is configured such that a first signal based on the control signal is provided to the control terminal of the first transistor and such that a second signal based on the control signal is provided to the control terminal of the second transistor; wherein the light source circuitry is further configured such that, when the control signal is at a first level, the largest proportion of the fixed current flows through the third group of light emitting diodes and such that, as the control signal changes to a second level, the proportions of the fixed current that flow through the first and second groups of light emitting diodes increase.