To generate synchronization signals of PWM (pulse width modulation) signals from the PWM signals.

A triangular wave generation circuit 101 generates, from the PWM signals PWMIN, the triangular wave signals TRIA and TRIB having two positive and reverse phases that alternately repeat the process of rising with a fixed temporal gradient and the process of falling with the fixed temporal gradient according to the rising edge of the PWM signals PWMIN and the triangular wave signals TRIC, that alternately repeat the process of rising with the fixed temporal gradient and the process of falling with the fixed temporal gradient according to the falling edge of the PWM signals PWMIN. A comparator 121 outputs pulses PD, indicating the level comparison result of the triangular wave signals TRIA and the triangular wave signals TRIC. A comparator 122 outputs pulses PE, indicating the level comparison result of the triangular wave signals TRIB and the triangular wave signals TRIC. An XNR gate 130 generates pulses whose level is inverted, depending on whether the levels of the pulses PE and PE match, and outputs them as the synchronization signals SYNC.