| 摘要 |
PROBLEM TO BE SOLVED: To provide a control circuit capable of improving a light load efficiency with a relatively simple configuration, and controlling the oscillation state of a switching power supply in a stable manner under a wide-range input/output condition. SOLUTION: The frequency of a voltage lowest point of voltage resonance caused by a primary winding of a transformer and a capacitor is counted by a lowest point detection counting part as lowest point frequency information. The time at which the point frequency is counted is detected as a count time, and a first reference time or a second reference time is set. A set state or a reset state is logically held by a logic holding circuit part. The first reference time or the second reference time that has been set is compared with the count time for the length of time. Based on the result information of comparison for length and the information held by the logic holding circuit part, the logic holding circuit part is switched. Further, upon switching of the logic holding circuit part, the frequency of lowest point skips, before a semiconductor switch is turned on, is determined based on the lowest point frequency information. COPYRIGHT: (C)2012,JPO&INPIT |
