Tunable light emitting device

A light emitting device configured to tunably emit light with a total color temperature (CTtot), said light emitting device comprising:

• at least one light emitting diode (LED) filament, comprising an elongated carrier having a first major surface and a second major surface opposite to said first major surface,
• a first light source, being a first plurality of LEDs arranged on said first major surface of the carrier, and arranged to emit a first light with a first color temperature (CT1), said first color temperature tunably adjustable within a first color temperature range from a first low color temperature (CT1low) to a first high color temperature (CT1high), having a range span r1=|CT1low−CT1high|, and with a first luminous flux F1,
• a second light source, being a second plurality of LEDs arranged on said second major surface of the carrier, and arranged to emit a second light with a second color temperature (CT2), said second color temperature tunably adjustable within a second color temperature range from a second high color temperature (CT2high) to second low color temperature (CT2low), having a range span r2=|CT2low−CT2high|, and with a second luminous flux F2,
• a controller configured to individually control the first and second light sources so to tunably adjust said first and second color temperatures from a first state to a second state according to a preselected scheme,
• by increasing the first color temperature from CT1low in said first state to CT1high in said second state, and by decreasing the second color temperature from CT2high in said first state to CT2low in said second state,
• said controller is further configured to control the first and second luminous fluxes F1 and F2, such that the change is F1 is larger than the change in F2 if r1<r2 and visa versa,
• such that the total color temperature of the light emitting device remains invariant at a constant value in said first and second states, preferably the first color temperature and the second color temperature differ less than 300 K.