A driver for driving a gas discharge lamp includes an inductive ballast implemented as auto-transformer having a central tap, connected between one output terminal and a first input terminal, and a triac connected between a second output terminal and a second input terminal. The central tap of the ballast is connected, via a capacitor, to the second output terminal. A control unit has a sense input for sensing the phase of an input voltage at the first input terminal, and is adapted to trigger the triac at a predetermined phase (.PHI..sub.p) after a zero-crossing of the input voltage, the predetermined phase (.PHI..sub.p) being in the range of .DELTA..PHI.+10.degree. to .DELTA..PHI.+15.degree., .DELTA..PHI. being the nominal phase lag of the lamp current with respect to the input voltage.