A desired current is caused to flow through a coil by controlling switching of switching elements by a PWM controller. For a voltage sensor, a value of Vo−ΔV, which is a difference between a midpoint voltage Vo of the switching elements and a predetermined threshold voltage ΔV, and a value of Vo−(Vc−ΔV), which is a difference between the midpoint voltage Vo and a value obtained by subtracting the threshold voltage ΔV from a voltage Vc of an upper line, are determined. Then, the determined results obtained from the voltage sensor are input to the PWM controller through flip-flops and a dead time compensator to compensate for dead time, such as, for example, for a command for PWM control signal generation.