This part of IEC 61347 specifies particular safety requirements for electronic step-down convertors for use on d.c. supplies of up to 250 V or a.c. supplies of up to 1 000 V, at 50 Hz or 60 Hz and with rated output voltage = 50 V r.m.s. at a frequency deviating from the supply frequency, or 120 V ripple free d.c. between conductors and between any conductor and earth, associated with tungsten-halogen lamps as specified in IEC 60357 and other filament lamps. NOTE The limit of 50 V rated output voltage is in accordance with band I of IEC 60449. Particular requirements for electronic step-down convertors with means of protection against overheating are given in Annex C. Particular additional requirements for convertors providing safety extra low voltage (hereinafter SELV), are given in Annex I. Performance requirements are covered by IEC 61047. Plug-in convertors, being part of the luminaire, are covered as for built-in convertors by the additional requirements of the luminaire standard.