| 摘要 |
<p>PURPOSE:To improve the efficiency of a power source by forming a pulse width control signal by an OFF signal generator for generating an OFF signal which varies in a low level width in response to the amplitude of an output voltage in synchronization with a switching frequency. CONSTITUTION:An OFF signal generator 1 has a first reference source 2, an error amplifier 3, a variable impedance circuit 4, an integrating capacitor 5, a first reset switch 6, a second reference source 7 and a comparator 8. An OF pulse signal generator 10 for generating an ON pulse signal in synchronization with the switching frequency of a switching element has a reference source 12, an integrating capacitor 13, a second reset switch 14 and a comparator 15. Thus, since the OFF pulse becomes valid before the ON pulse signal is generated when an output rises higher than the reference source at the time of a light load or the like, the ON pulse signal is not output so that a pulse width control signal is made open-phased.</p> |
