| 摘要 |
PROBLEM TO BE SOLVED: To reduce a drop of supply voltage when an externally supplied DC voltage drops, and implement an overcurrent limiting function for a load. SOLUTION: A main transistor T1 has a collector connected to a DC power line 3. A supply voltage Vd is supplied to a load circuit 6 through an emitter of the main transistor T1 and a DC power line 4. A constant voltage circuit 7 clamps a DC voltage VB between the DC power lines 3, 4 at a clamp value to output a constant voltage Va. A step-up circuit 8 steps up the supply voltage Vd to output a step-up voltage Vb. A voltage selection circuit 9 applies the higher voltage of the constant voltage Va and the step-up voltage Vb to a base of the main transistor T1. The step-up circuit stops the step-up action when the DC voltage VB is equal to or higher than the clamp value. COPYRIGHT: (C)2013,JPO&INPIT |
