The invention relates to phosphor-conversion sources of white light, which are composed of at least two groups of emitters, such as blue electroluminescent light-emitting diodes and wide-band or narrow-band phosphors that partially absorb and convert the flux generated by the LEDs to other wavelengths, and to improving the quality of the white light emitted by such light sources. 2-Oxo-4-methylthiobutyric acid, its salts and its derivatives are used as food supplement, in particular in animal nutrition. This manufacturing method is applicable with substantially no change in the conventional material and process. 1 wt % hydrofluoric acid and at least 0. At least a main part of the first region overlaps the transistor in plan view.