Patent ID: 8076871

Claim:
A driver apparatus for driving a gas discharge lamp (L), the apparatus comprising a commutator circuit, comprising: input terminals for receiving an input current, a branch comprising lamp connection terminals for connecting the lamp (L), with an inductor (L 2 ) arranged in series with the lamp connection terminals and a capacitor (C 3 ) arranged in parallel with the lamp connection terminals, the inductor (L 2 ) and the capacitor (C 3 ) having a parallel resonance frequency f R ; and a controller for controlling said commutator circuit ( 5 ) so as to alternate between a first state, in which the lamp current has a first direction, and a second state, in which the lamp current has a second direction; wherein the controller ( 6 ) is capable of operating: in a steady-state mode in which alternating between said first state and said second state takes place at a relatively low commutation frequency; in a hot-restrike ignition mode in which alternating between said first state and said second state takes place at a first ignition frequency f P1 =f R /n 1 , n 1 being an odd integer; and in a cold-ignition mode in which alternating between said first state and said second state takes place at a second ignition frequency f P2 =f R /n 2 , n 2 being an odd integer larger than n 1 .