A positive counter starts counting, starting with an initial value, upon receiving a positive edge of a dimming pulse signal. A negative edge counter starts counting, starting with an initial value, upon receiving a negative edge of the dimming pulse signal. For each i-th (2≦i≦n) channel, the phase shift amount is calculated by multiplying a period count value that indicates the period of the dimming pulse signal by (i−1)/n. When the count value matches the phase shift amount, a burst control signal is switched to a first level. When the count value matches the phase shift amount, the burst control signal is switched to a second level.