An apparatus for driving a lamp of a liquid crystal display device includes a control signal generator generating a switching control signal, a waveform modulator modulating at least an amplitude of the switching control signal to generate a modulated switching control signal, and an AC waveform generator converting a supply voltage based on the modulated switching control signal to generate an AC waveform for driving the lamp, the AC waveform including at least two different peak-to-peak amplitudes within a time period.