| US 7,492,113 B2 | ||
| Brushless motor drive control circuit and brushless motor device using the same | ||
| Norihiro Maeda, Kyoto (Japan) | ||
| Assigned to Rohm Co., Ltd., Kyoto (Japan) | ||
| Appl. No. 11/596,770 PCT Filed May 26, 2005, PCT No. PCT/JP2005/009625 § 371(c)(1), (2), (4) Date Nov. 17, 2006, PCT Pub. No. WO2005/117249, PCT Pub. Date Dec. 08, 2005. |
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| Claims priority of application No. 2004-160355 (JP), filed on May 28, 2004. | ||
| Prior Publication US 2007/0176567 A1, Aug. 02, 2007 | ||
| Int. Cl. H02P 6/00 (2006.01) | ||
| U.S. Cl. 318—400.01 [318/459; 318/700; 318/368; 318/145] | 4 Claims |
| 1. A brushless motor drive control circuit for controlling, through a motor driver, drive of a brushless motor whose rotor
is rotated by the flow of a driving current to 3-phase stator coils having one end connected to a common neutral point, comprising:
at least one counter electromotive voltage filter circuit for inputting a voltage at the neutral point and a counter electromotive
voltage induced at the other end of each phase of the stator coils and switching at least between first and second time constants
according to a rotation speed of the rotor to pass a low-range frequency component corresponding to the time constant,
at least one counter electromotive voltage detection comparator for comparing the counter electromotive voltage which has
passed through said counter electromotive voltage filter circuit and the voltage at said neutral point to output a counter
electromotive voltage polarity signal as the comparison result, and
a motor driver control circuit responsive to said counter electromotive voltage polarity signal for controlling switching
of said time constant of said counter electromotive voltage filter circuit and controlling said motor driver.
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