| 摘要 |
PROBLEM TO BE SOLVED: To simplify the structure of a rotor position detecting circuit of a brushless motor, make the motor small and low cost and made a very precise position detection. SOLUTION: When DC power is switched by a plurality of transistors of an inverter section 3 and is supplied to a brushless motor 4, a position detecting circuit 10 synthesizes the terminal voltages of armature windings by means of a synthesis circuit 10a and then cuts a DC component of the synthesized voltage (neutral point voltage: induced voltage waveform) by means of a DC-cutting circuit 10b and at the same time, generates a specified reference voltage by means of a voltage generating circuit 10c and connects the neutral voltage with its DC component cut and the specified reference voltage with a resistor circuit 10e and fluctuates the neutral voltage above and below the specified reference voltage. The neutral voltage which has been fluctuated above and below is compared with the specified reference voltage, by a comparing circuit 10e to detect a signal at the intersection between the neutral voltage and the reference voltage (a signal which changes at the half point of the induced voltage) and then outputs the signal to a controlling circuit 11. The controlling circuit 11 detects a magnetic pole changing point of a rotor changes (in other words, detects the position of the rotor) from the signal which changes at the half point of the induced voltage (in other words, detects the position of the rotor) and then switches the energization of the armature windings according to the magnetic pole changing point. |
