| 摘要 |
PURPOSE:To prevent the heat generation of a transistor by setting an FF and stopping conduction when the current of the transistor for driving a motor exceed a fixed value and resetting the FF by a proper clock signal and restart the conduction. CONSTITUTION:A motor 50, a transistor(Tr) 52 and a resistor 60 for detecting current are connected in series. The terminal voltage V0 of the resistor 60 and the reference voltage Vr of a reference-signal generating section 61 are compared 70 by a comparator 70, and a level L is output by the comparator 70 and input to the terminal S of an FF 80 when V0>Vr holds. When an output from a clock signal generator 90 is brought to 'H' and input to the terminal R of the FF 80 at that time, the FF 80 outputs 'H', a Tr 101 is turned ON, the Tr 52 is turned OFF, and the motor 50 is stopped. When voltage V0 drops and V0<Vr holds, the comparator 70 outputs 'H', and input to the terminal S of the FF 80, the FF 80 outputs 'L' when the terminal R is brought to 'L' from 'H', the Tr 101 is turned OFF, the Tr 52 is turned ON, and the motor 50 is restarted. Accordingly, a low-cost Tr having a narrow safety operation region is used as the Tr 52. |
