| 摘要 |
PROBLEM TO BE SOLVED: To remove the flyback voltage components of an induced voltage that is generated in the floating phase of an excitation coil, and high-frequency components by a PWM signal, without requiring any externally mounted elements or without increasing the size of the elements. SOLUTION: When the position of a rotor is to be detected by detecting an induced voltage, that is generated at excitation coils 3, 4, and 5 of a star connection three-phase brushless motor 1, the potential of terminals U, V, and W of the excitation coils 3, 4, and 5 and that of a neutral point terminal C are sampled by transfer gates 36, 37, 38, and 39 in synchronization with the on signal of a PWM signal excluding a prescribed period immediately after switching to a floating phase. At the same time a sampling voltage immediately before the off control period of the transfer gates 36, 37, 38, and 39 is compared by comparators 33, 34, and 35, while the voltage is retained at capacitors 40, 41, 42, and 43, thus detecting the position by the induced voltage which does not contain flyback voltage components and high-frequency components due to a PWM signal, and hence detecting the position accurately without using externally mounted integration circuits or without increasing element areas too much. |
