| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent overcurrent detection from malfunctioning by appropriately changing a threshold value. <P>SOLUTION: An overcurrent detection circuit 6B has resistances R21 and R31 connected between both ends of a current detection resistor R11 located between an emitter of Q2 and an output terminal O. Both ends of R31 are connected between a base and an emitter of an overcurrent detection transistor Q5, a diode D21 and a resistance R61 are connected between the output terminal O and -V<SB POS="POST">B</SB>, and a cathode of D21 is connected with an emitter of Q5. A resistance R51 and D11 are connected between a node of R21 and R31, and a ground, and a capacitor C21 is connected between a node of R51 and D11, and an emitter of Q2. A threshold value variable circuit 9A having R51, D11 and C21 makes a threshold value large, if a magnitude of an output voltage becomes large, and makes the threshold value small, if the magnitude of the output voltage becomes small. However, the threshold value variable circuit 9A makes the threshold value increase fast by C21 and D11 when a magnitude of the output voltage increases, and when decreasing, makes the threshold value decrease slowly. <P>COPYRIGHT: (C)2012,JPO&INPIT |
