| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching type power supply unit for attaining a highly accurate constant-current drooping characteristic by maintaining a constant on-duty of a secondary current passing through a secondary winding even if an oscillation frequency of a switching device is high. SOLUTION: A secondary current on-period detection circuit 6 generates a signal indicating an off-timing of a secondary current detected from a flyback voltage generated at an auxiliary winding 113. A secondary current detection delay time compensation circuit 7 generates a signal indicating a timing when a predetermined period elapses after the switching device 1 is turned off. In addition, a secondary current on-duty control circuit 8 generates a clock signal for turning on the switching element 1 so that on-duty of a secondary current is made constant, based on a signal generated by the secondary current on-period detection circuit 6 and a signal generated by the secondary current detection delay time compensation circuit 7. COPYRIGHT: (C)2009,JPO&INPIT
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