| 摘要 |
<P>PROBLEM TO BE SOLVED: To exhibit the effect of field-weakening control sufficiently by making a reference voltage being compared with an induced voltage in order to detect rotor position variable linearly thereby varying a conduction phase timing significantly. <P>SOLUTION: When the output from an inverter circuit 3 for controlling a brushless DC motor 6 is in saturated state, a reference voltage being compared with an induced voltage of a stator winding (imaginary neutral voltage) is increased/decreased linearly. In this regard, a control circuit 15 delivers a PWM signal having a specified duty ratio to a low-pass filter circuit 12 and a specified amount of differential voltage is outputted therefrom. Output (reference voltage) from a voltage division circuit 10 is increased/decreased linearly at a reference voltage generating section 13 by the specified differential. The imaginary neutral voltage of the motor (induced voltage waveform of motor) from an imaginary neutral circuit 11 is compared with these two new reference voltages and the comparison result is employed as a positional signal. Field-weakening control can be carried out by advancing the conduction phase due to intersection of the induced voltage and the reference voltage significantly. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
