| 摘要 |
A driver (110; 210) for driving a gas discharge lamp (1) comprises an inductive ballast (14) implemented as auto-transformer having a central tap (15), connected between one output terminal (18) and one input terminal (11), and a triac (130) connected between a second output terminal (19) and a second input terminal (12). Said central tap of the ballast is connected, via a capacitor (150), to said second output terminal (19). A control unit (220) has a sense input (226) for sensing the phase of an input voltage (VIN) at said one input terminal (11), and is adapted to trigger the triac (130) at a predetermined phase ( phi P) after a zero-crossing of said input voltage (VIN), said predetermined phase ( phi P) being in the range of DELTA phi +10 DEG to DELTA phi +15 DEG , DELTA phi being the nominal phase lag of the lamp current (IL) with respect to the input voltage (VIN).
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