| 摘要 |
PURPOSE:To stabilize the operation of a switching regulator even in case of voltage variations which exceed a control range, by specifying the length of the conduction period of a switching element when detecting an AC input voltage dropping rapidly. CONSTITUTION:If an unstabilized DC voltage obtained only by rectifying an AC input voltage applied to a terminal drops rapidly, a voltage at the connection point between resistances 26 and 27 drops below the collector voltage of a transistor (TR) 18 in a normal state, turning on a diode 30. As a result, while the base boltage of a TR 14f drops, the base current increases, so a voltage at the connection point (a) between the collector of the TR14f and the base of a TR13 rises to prolong the on period of the TR13 which truns on a switching element 2, whose on period is then shortened, thereby preventing the switching element from being cut off. |
