| 摘要 |
PURPOSE:To provide a control circuit which efficiently drives a brushless motor regardless of the variation in number of revolution. CONSTITUTION:The title control circuit consists of a resultant voltage detecting circuit 3, connected in parallel with fixed windings, which is composed of resistors forming polyphase connection and detects the terminal voltage of the fixed windings; comparator 15 which generates exciting timing waveform signals VP to detect the timing to excite the fixed windings based on the neutral point voltage of the fixed windings and the resistance neutral point voltage of the resultant voltage detecting circuit 3; and reference signal circuit 9 which outputs reference square-wave signals PT, having a required phase difference, in response to exciting timing waveform signals VP from the comparator 15. In addition the control circuit is provided with a three-phase ring counter 4 which outputs exciting signals SUH-SWL for timely connecting/disconnecting switching elements based on the rise and fall of the reference square-wave signals PT output from the reference signal circuit 9. |
