| 摘要 |
<p>A switching power source which detects the power failure within a short period of time and maintains its output voltage for a long time. The switching power source comprises: first voltage control means which controls the switching means (2) by controlling pulse width modulation means (9) using first differential voltage detecting means (8) which compares the output voltage (VO) with a reference voltage (VR); and second voltage control means having means (12) for expanding the operation range of the pulse width modulation means to extend a maximum period of energization of the pulse width modulation means (9) using second differential voltage detecting means (11) which compares said output voltage (VO) with a second reference voltage (VRR) which is smaller than the reference voltage (VR); wherein provision is made of second switching means (16) that connects a precharged second capacitor (15) in parallel with a first capacitor (1) of the power source input side when the second differential voltage detecting means (11) operates twice within a short period of time.</p> |
