| 摘要 |
PROBLEM TO BE SOLVED: To prevent incorrect position detection and change over energization optimally by obtaining a proper reference voltage in the rotational control of a brushless motor. SOLUTION: When a DC power is switched by a switching element of an inverter circuit 3 and applied to the brshless motor 4, a control circuit 11 detects the position of the rotor of the brushless motor 4 by a position detecting signal from a position detector 5, and the supply of the armature winding current of the brushless motor 4 is changed over on the basis of the position detection. A reference-voltage generating circuit 10 divides the voltage of the power supply for the inverter circuit 3 by a resistor circuit 10a consisting of one resistor R5 and a plurality o resistors R6 or R9 and a plurality of fixed voltage can be generated at that time, and one fixed voltage in a plurality of fixed voltage is selected by a selector circuit 10b. The control circuit 11 controls the selector circuit 10b, detects a plurality of fixed voltages, and determes one fixed voltage as reference voltage. A composite voltage obtained by combining the winding voltage of the brushless motor 4 by a resistor circuit 5a and the determined reference voltage are compared by a comparison circuit 5b, and the result of the comparison is used as a position detecting signal. |
