An electric lamp supply comprises a full-wave rectifier (D1-D3, SCR) composed partially or entirely of thyristor(s), said full-wave rectifier having both an input terminal connected with an ac source (AC) and an output terminal connected with a lamp (Z); smoothing means (C1) connected in parallel with the lamp; means (ZD) to detect a voltage across the lamp that exceeds a prescribed level; and means (T,C2) to control the conduction angle of the thyristor(s) (SCR) dependently on the magnitude of the voltage, said controlling means being operable in association with said detecting means.