| 摘要 |
<p>The length of a soft start period is set by the time constant of an external circuit connected to a soft start terminal (SS) of a switching control IC (200). A current flowing through a switching element (Q1) is detected by a current detection terminal (IS), when the current exceeds a first predetermined current value, a second overcurrent protection function operates to stop a switching operation, and when the current exceeds a second predetermined current value, the second overcurrent protection function operates to rapidly turn off the switching element (Q1) to thereby limit the current peak value. The setting/unsetting of a first overcurrent protection function is selected according to the voltage of the soft start terminal (SS) at the end of the soft start period. After the voltage of the soft start terminal (SS) reaches a predetermined voltage, the ON pulse width of the switching element (Q1) is limited to the maximum value. Consequently, the increase of the number of terminals is prevented, and an appropriate overcurrent protection method can be selected from among a plurality of overcurrent protection methods.</p> |
