LED-valolähde ja menetelmä LED-valolähteen värisävyn tai väri-lämpötilan säätämiseen

In a light source, a plurality of parallel LED strings or columns (R, G, B) share the same current source (12) as a function of time. Current distribution to the LED strings is carried out with semiconductor switches (Q1, Q2, Q3) that are connected in series with the LED strings. Each semiconductor switch and the corresponding LED string is controlled with a dedicated pulse-width modulated colour control signal (C1, C2, C3). The pulse-width modulated control signals control the semiconductor switches (Q1, Q2, Q3) and the LED strings (R, G, B) sequentially active one at a time and to take current from the common current source (12) for the time defined by the corresponding pulse-width modulated control signal (C1, C2, C3). This control establishes colour tone and colour temperature adjustment, which is independent of the operation of the shared current source. The adjustment of the colour tone or colour temperature of a light source may be controlled by two pulse-width modulated colour signals (A, B) from which, in the LED light source, the required number of pulse-width modulated colour control signals (C1, C2, C3) are formed by logical operations, such as NOR, XOR, and AND operations.