Each of blocks includes an arbitrary number of series connections of LEDs. A current signal for controlling operation of the LEDs in the blocks is divided into plural signal currents. An allowable forward current having a duty cycle corresponding to a division number is caused to flow through the LEDs in one block for an allowable time, using one of the signal currents. A rated forward current that does not cause destruction of LEDs is caused to flow through the LEDs in the other blocks, using the other of the signal currents. The LEDs in the blocks are driven by causing the allowable forward current and the rated forward current to flow periodically. The rated forward current is caused to flow through at least one additional LED, whereby a difference between respective voltages corresponding to the allowable forward current and the rated forward current is produced.