Emergency power supply circuit for dimmable electronic ballasts and related method

An emergency supply circuit for an electronic ballast may include: an output line to feed a supply input of the ballast; a first line to receive a mains supply signal; a second line to receive an emergency supply signal from a battery, with a converter interposed in said second line to boost said supply signal, a switch to alternatively connect said output line to said first or said second line; a controller sensitive to the absence of said mains supply signal and to the charge level of said battery, said controller to produce switching of said switch to connect said output line to said second line in the absence of said mains supply signal on said first line, whereby said output line receives said supply signal, and dimming interface circuitry to drive said dimming control input of said ballast when said output line is connected to said second feed line.