| 摘要 |
PURPOSE:To control an overcurrent at the starting time by driving a power transistor via a pulse and controlling the pulse width in response to the current which is inputted to a motor. CONSTITUTION:When a control circuit becomes ON, a frequency generator 13 applies a rectangular pulse to a counter 14 and a triangular pulse to a comparator 15. The counter 14 sequentially outputs signals to terminals 14a-14c in response to the counted values of the rectangular pulses. On the other hand, since a reference voltage A is inputted to the negative input of the comparator 15, a pulse of wide width is applied through AND gates 19-21 which are opened by the output from the counter 14 to transistors TR4-TR6. When a large current is flowed when a motor IN is started, a phototransistor 33 becomes ON, a transistor 37 is turned OFF, a transistor 35 is turned ON, and a reference voltage B is inputted to the negative input of the comparator 15, and a pulse of narrow width is accordingly ouputted. |
