| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately detect the rotation position of a rotor even when a hall device detection signal changes due to a temperature change or a variation in device quality. <P>SOLUTION: A motor position detector comprises hall devices which, upon detecting a magnetic field from magnets for magnetic fields disposed on a rotor, output a hall signal U in sinusoidal waveform; and a zero-cross detection circuit, having a first threshold (0(V)), a second threshold Th2 smaller than the first threshold and a third threshold Th3 larger than the first threshold, which compares the hall signal U with the thresholds and then outputs a position detection signal Spu indicating the rotation position of the rotor. The zero-cross detection circuit, while the first threshold having been set, switches its threshold to the second threshold synchronously when the hall signal U has increased to cross the first threshold and then restores it to the first threshold with prescribed timing, or switches its threshold to the third threshold synchronously when the hall signal U has decreased to cross the first threshold and then restores it to the first threshold with prescribed timing. <P>COPYRIGHT: (C)2013,JPO&INPIT |
