Patent ID: 8587201

Claim:
An emergency supply circuit for an electronic ballast, wherein said electronic ballast includes a supply input as well as a dimming control input, the circuit comprising: an output line to feed said supply input of the electronic ballast; a first feed line to receive a mains supply signal; a second feed line to receive an emergency supply signal from a battery, with an electronic converter interposed in said second feed line to boost said emergency supply signal, a switch to alternatively connect said output line to said first or said second feed line; a controller sensitive to the absence of said mains supply signal on said first supply line and to the charge level of said battery, said controller to produce switching of said switch to connect said output line to said second feed line in the absence of said mains supply signal on said first feed line, whereby said output line receives said emergency supply signal boosted by said converter, and dimming interface circuitry controlled by said controller to drive said dimming control input of said ballast when said output line is connected to said second feed line; wherein said electronic converter is a DC-DC converter; and wherein a low frequency AC ripple is added to the DC output of said converter.