US 8,427,079 B2Granted

Method and device for driving a multicolor light source

AssigneeKoninklijke Philips Electronics N.V.

InventorsGeert Willem Van Der Veen, Johannes Antonius Kwakman

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Abstract

A lighting device (1) comprises a plurality of LEDs (11-14) producing light (21-24) of mutually different colors. The LEDs are driven in switching cycles (63) with a duty cycle controlled supply current of constant magnitude. In each switching cycle, each LED is first switched ON (61) and then switched OFF (62). In a measuring mode, during one switching cycle (63B), all ON phases of all LEDs are briefly interrupted, except for one LED (11), so that a light sensor (70) measures the light from this one LED. This measurement can be used to adapt the duty cycle of this one LED. In the next switching cycle (63C), the interruption of the ON phases is compensated by extending the ON phases of all LEDs except said one LED, the extension having a duration equal to the duration (τD) of the interruption.

Claims18

Dependent claims

Method for driving a lighting device comprising a plurality of light sources producing light of mutually different colors, wherein the light sources are driven in switching cycles with a duty cycle controlled supply current of constant magnitude, wherein, in each switching cycle, each light source is first in an ON phase and then in an OFF phase;

the method comprising the steps of:
in a measuring mode, selecting one light source to be measured and, during one switching cycle, briefly interrupting all ON phases of all non-selected light sources simultaneously;
and
in a compensation mode, compensating said interruption of the ON phases by briefly interrupting the OFF phases of said non-selected light sources, the interruption of the OFF phases in the compensation mode having a duration equal to the duration of the interruption of the ON phases in the measuring mode.

1 more element

Dependencies are inferred from the claim text.