Patent ID: 7339329

Claim:
A ballast for an electrodeless discharge lamp, said ballast comprising: an induction coil adapted in use to be disposed adjacent to said discharge lamp; a high frequency power supply supplying a high frequency electric power to said induction coil for operating said lamp; and a dimmer controller which, in response to a dimmer command designating a varying dimming ratio, generates a control signal defining a first period in which said power supply is controlled to apply a coil voltage of a first level to said induction coil for operating said lamp, said first period being followed by a second period in which said power supply is controlled to apply the coil voltage of a second level that is lower than said first level and fails to sustain the lamp, wherein said dimmer controller generates said control signal that defines, between said second period and said first period, a starting period in which said coil voltage increases continuously.