CURRENT LIMITING CIRCUIT

PROBLEM TO BE SOLVED: To prevent an increase in the voltage of a comparator input terminal in a current limiting circuit for a boost converter to enable current detection with high accuracy without requiring a semiconductor structure of high breakdown voltage. SOLUTION: Between a main switch 22 which flows a current to an inductor 21 and a comparator 40 included in a current detecting circuit 4, a voltage divider circuit 6 is provided which includes two transistors 61, 62 of the same type as that of the main switch 22, that are connected in series. The one transistor 61 is a sub-switch which is connected between a voltage division point M and a drain terminal of the main switch 22, and is turned on/off in synchronization with the main switch 22 in accordance with an output signal of a control circuit 10. The other transistor 62 is a detection resistance transistor which is connected between the voltage division point M and a source terminal of the main switch 22, and whose gate terminal is connected to a bias voltage so that the detection resistance transistor is always on. COPYRIGHT: (C)2011,JPO&INPIT