| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a switching power supply device capable of further suppressing overcurrent to a transformer when overcurrent occurs, reducing voltage fluctuation at a current detection terminal of a control circuit which is caused by change in an ambient temperature, and suppressing variation in an overcurrent protection operation. <P>SOLUTION: A control circuit 15 is configured to have a main switching element Q1 connected in series to a primary coil N1 of a transformer T, and to perform PWM control of the main switching element Q1 to perform an overcurrent protection operation. A control switching element Q2 connected between a switching frequency setting circuit 16 and a ground terminal of the control circuit 15 turns on when an output voltage generated at a third coil N3 reduces to a predetermined setting value or less to bypass a part of a current to the switching frequency setting circuit 16. A current detection terminal of the control circuit 15 for detecting a power supply output voltage is connected to a connection portion between a resistance R1 and a resistance R2 in a voltage-dividing circuit 18. <P>COPYRIGHT: (C)2013,JPO&INPIT |
