| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply in which the voltage drop of a control IC circuit down to an operation stop level is prevented for abrupt transient load variation of the switching power supply or transition from a loaded state to a standby state and stabilized response characteristics are ensured even to a variation in load when a transition is made from a standby state to an operating state. SOLUTION: An AC power being supplied from a socket 11 is rectified by a rectification circuit 13 through an input filter 12 and fed to the primary winding N1 of a transformer 14 before being on/off controlled at a specified timing by a switching element Q1 in a control circuit 19. An FB signal indicative of the power state of a load circuit 15 is fed to the control circuit 19 through a transistor Q2, a rectified voltage V3 on the tertiary winding of the transformer is compared with a reference voltage REF 3 by means of a comparator 20 and the transistor Q2 is controlled by the error signal thereof. Voltage drop of a control circuit being fed from the tertiary winding is thereby prevented for abrupt load variation and significant variation in output voltage V0 is prevented. COPYRIGHT: (C)2005,JPO&NCIPI
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