| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device for controlling switching power supply which, if feedback signals for controlling switching operation of a switching element are not obtained, and current flow from a control terminal ceases, causes the switching operation to stop and keeps the stopped state, thereby preventing breakage of a switching power supply unit. SOLUTION: The device is provided with a protection circuit 8 against opened control terminal which, when feedback signals to a control terminal 24 are cut off, causing current flow from the control terminal 24 to cease, and a voltage of the control terminal 24 exceeds a predetermined voltage, makes the current which flows through a source terminal of an N type MOSFET 12 greater than or equal to a first constant current value (a predetermined current value) that has been set by a constant current source 13, and keeps the state, thereby causing a switching element 1 to stop its switching operation and keep the state. COPYRIGHT: (C)2003,JPO
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