In a color separator circuit, edge detection filters detect an edge encountered in the horizontal direction. The four-step commutation device sets times between the steps to a value more than zero so as to inhibit open circuit between output phases and short circuit between power supply phases, and sets the times between the steps in accordance with the polarity of the load current so as to cancel a distortion of an output voltage due to four-step commutation during a PWM cycle. A first conductive layer is deposited at the bottom of the deep trench.