Patent attributes
Without shortening clock pulse duration serving as a unit time of a pulse generator, a pulse-width control is possible in which pulse duration varies in increments of a time length shorter than the unit time. A time width Ton_s of a pulse width finely dividing signal Vs from a DSP 17 varies by clock pulse duration Tclk in response to variations in an output voltage Vo. A time control circuit 18 that has received the pulse width finely dividing signal Vs generates, in a control signal Vd, varying segments 30, 31 for making the time width of the pulse drive signal Vg vary by a shorter time ΔTd than the clock pulse duration Tclk. Consequently, resolution of the time width of the pulse drive signal Vg is improved so as to be higher than the clock pulse duration Tclk, which is time resolution of the DSP 17 itself.