| 摘要 |
PURPOSE:To provide a speed detector for a brushless motor which requires only one comparator by comparing the output voltage from a 3-input diode OR circuit, connected reversely to a 2-input diode OR circuit, with the neutral voltage of a three-phase driving coil and outputting a speed detection signal thereby eliminating the logic circuit. CONSTITUTION:Signals of phases U, V, W induced in driving coils Lu, Lv, Lw have the waveform only of the lower potential part of a 2-input waveform passed through 2-input diode OR circuits (SD) D12, D34, D56. A 3-input diode OR circuit (TD) D789 is connected with the output terminals of the SDD12, D34, D56 and also connected, in reverse direction, with diodes D1-D6 and outputs a waveform having highest potential among 3-input waveforms. The neutral voltage of coil detected by a star-connected resistor R is compared with the output voltage from the TDD789 by a comparator 2 which outputs a speed detection signal. Consequently, the number of comparators can be decreased from three to only one. |
