An electronic ballast for driving a light-emitting device, includes a square wave generator having a plurality of switch elements for converting a DC input voltage into a square-wave AC voltage. A transformer has a driving winding and a plurality of inductive windings mutually connected with each other, in which at least a portion of the inductive windings are respectively connected to a control terminal of the switch element. A resonant circuit connects the driving winding and a light-emitting device and converts the square-wave voltage into an AC output voltage to drive the light-emitting device. An auxiliary control unit connected to the transformer regulates a voltage waveform of the driving winding or a voltage waveform of the inductive winding according to a control signal, thereby changing the voltage waveform of the inductive winding connected to the switch element to adjust the switching frequencies of the switch elements.