| 摘要 |
PROBLEM TO BE SOLVED: To provide an overcurrent protection circuit that can protect an internal circuit when an overvoltage occurs with suppressing a circuit area to a small value, and continue to supply less power than the usual.SOLUTION: A main SW element 4 having a current capability of enabling flow of current required for a normal operation of an internal circuit 2 is interposed in series to a power supply passage from a power supply terminal P1 to the internal circuit 2. A main driving circuit 8 operates the main SW element 4 under a full ON state. A sub SW element 5 having a current capability of enabling flow of only current which can perform an operation required for processing when an overvoltage occurs in the internal circuit 2 is provided in parallel to the main SW element 4. A sub driving circuit 9 makes the sub SW element 5 perform a voltage follower operation so that the voltage supplied to the internal circuit 2 is equal to a value in a stationary range. A switching control circuit 6 detects whether the voltage of the power supply terminal P1 is in an overvoltage state that the voltage is higher than an overvoltage determination value. When the voltage is not in the overvoltage state, the main driving circuit 8 is operated, and when the voltage is in the overvoltage state, the sub driving circuit 9 is operated and the operation of the main driving circuit 8 is stopped. |
