| 摘要 |
<p>A problem of the present invention is to provide a switching power supply device and a pulse width modulation circuit capable of operating stably in synchronization with a clock signal. To solve the problem, a pulse width modulation circuit 3A in a switching power supply device 1A includes square-wave voltage output means 8A for, when an integrated voltage Vn rises to an upper threshold voltage or more, shifting a square-wave voltage VPWM to L level, or when the voltage Vn drops to a lower threshold voltage or less, shifting the voltage VPWM to H level, and clock means 6A for outputting a first clock signal VCL1 and a second clock signal VCL2, which are 180° out of phase from each other. The square-wave voltage output means 8A is adapted to: (1) if the clock signal VCL1 changes while the voltage Vn is dropping, shift the voltage VPWM to H level even when the voltage Vn has not yet reached the lower threshold voltage; and (2) if the clock signal VCL2 changes while the voltage Vn is rising, shift the voltage VPWM to L level even when the voltage Vn has not yet reached the upper threshold voltage.</p> |
