| 摘要 |
PURPOSE:To reduce vibration and noise and at the same time to increase efficiency by solving the problems that even when an overlap is produced in an output transistor when a control circuit is saturated to performs phase-switching in a driving circuit for a brushless motor having a saturation preventing circuit for an output transistor, the overlap cannot be controlled because of the saturation of a feedback loop and as a result, noise and vibration are produced, thereby allowing the output transistor to be always operated by a proper base current corresponding to the output current. CONSTITUTION:A current detection circuit 1100 for detecting the sum of the output currents of a group of output transistors is provided, and a command voltage is determined by the output of the current detection circuit 1100, thereby being able to produce a command voltage in proportion to the output current of a driving circuit independently of the operating state of an amplifier 301 in a control circuit 300, so that the output transistors 501, 502, 503 of a group 500 of output transistors are operated by a proper base current corresponding to an output current to always supply the maximum voltage to a motor without vibration and noise produced. |
