Brushless motor drive device and drive method

摘要

The invention relates to a brushless motor drive device that performs switching determination of energization modes of a three-phase brushless motor according to a sensorless method, and a drive method thereof. A pulse induced voltage induced in a non-energized phase of three phases by a pulse voltage is compared with a threshold to determine the switching timing of the energization modes. Here, by limiting a duty ratio of a voltage application to equal to or greater than a lower limit, a situation in which the pulse induced voltage is sampled while the pulse induced voltage is oscillating is avoided, and a situation in which the pulse induced voltage falls below a voltage detection resolution is avoided. As a result, determination of energization mode switching timing based on a pulse induced voltage can be performed more stably.

主权项

1. A brushless motor drive device comprising:
a switching section that includes a plurality of energization modes in which two phases to be applied with a pulse voltage are selected from three phases of a three-phase brushless motor, and is configured to switch the plurality of energization modes; a determining section configured to determine switching timing of the energization modes based on a pulse induced voltage induced in a non-energized phase of the three phases by the pulse voltage; and a restricting section configured to
set a duty ratio of the pulse voltage to be equal to or greater than a lower limit, andset a duty ratio, with which the pulse voltage is applied, for a time longer than a sum of an oscillation time of the pulse induced voltage immediately after starting application of the pulse voltage and a time required for A/D converting of the pulse induced voltage, as the lower limit.