Control device for brushless DC motor

A control device for a brushless DC motor having an armature and a rotor, the control device comprising:

• an inverter having semiconductor switching elements for switching DC current on and off and supplying multi-phase driving voltage to the armature;
• means for starting and accelerating the motor to a predetermined rotational speed by controlling the inverter under a start-up-drive mode;
• means for detecting an angular position of the rotor based on voltage induced in the armature;
• means for driving the motor by controlling the inverter based on the detected angular position of the rotor under a self-controlled-drive mode;
• means for detecting a phase difference between a phase of the detected angular position of the rotor and a phase of the driving voltage supplied to the armature;
• and
• means for switching drive modes from the start-up-mode to the self-controlled-mode, wherein:
• the switching means switches the start-up-drive mode to the self-controlled-drive mode based on a plurality of signals representing the phase difference detected in a predetermined period of time, and
• wherein the switching means, in a transient period from the star-up-drive mode to the self-controlled-drive mode, decreases duty ratio of the pulse-width-modulated driving voltage when the phase of the driving voltage is advanced by more than a predetermined amount from the phase of the angular position of the rotor, and increases the duty ratio of the pulse-width-modulated driving voltage when the phase of the driving voltage is delayed by more than a predetermined amount from the phase of the angular position of the rotor, thereby making the phase difference between both phases smaller.

A control device for a brushless DC motor having an armature and a rotor, the control device comprising:

• an inverter having semiconductor switching elements for switching DC current on and off and supplying multi-phase driving voltage to the armature;
• means for starting and accelerating the motor to a predetermined rotational speed by controlling the inverter under a start-up-drive mode;
• means for detecting an angular position of the rotor based on voltage induced in the armature;
• means for driving the motor by controlling the inverter based on the detected angular position of the rotor under a self-controlled-drive mode;
• means for detecting a phase difference between a phase of the detected angular position of the rotor and a phase of the driving voltage supplied to the armature;
• and
• means for switching drive modes from the start-up-mode to the self-controlled-mode, wherein:
• the switching means switches the start-up-drive mode to the self-controlled-drive mode based on a plurality of signals representing the phase difference detected in a predetermined period of time, and
• wherein the switching means switches the start-up-drive mode to the self-controlled-drive mode when a part of the plurality of signals representing the phase difference is included in a predetermined range and the rest of the signals indicate that the phase of the driving voltage is advanced from the phase of the rotor position.

A control device for a brushless DC motor having an armature and a rotor, the control device comprising:

• an inverter having semiconductor switching elements for switching DC current on and off and supplying multi-phase driving voltage to the armature;
• means for starting and accelerating the motor to a predetermined rotational speed by controlling the inverter under a start-up-drive mode;
• means for detecting an angular position of the rotor based on voltage induced in the armature;
• means for driving the motor by controlling the inverter based on the detected angular position of the rotor under a self-controlled-drive mode;
• means for detecting a phase difference between a phase of the detected angular position of the rotor and a phase of the driving voltage supplied to the armature;
• and
• means for switching drive modes from the start-up-mode to the self-controlled-mode, wherein:
• the switching means switches the start-up-drive mode to the self-controlled-drive mode based on a plurality of signals representing the phase difference detected in a predetermined period of time, and
• wherein the driving voltage supplied to the armature is a pulse-width-modulated voltage,
• wherein the switching means switches the start-up-drive mode to the self-controlled-drive mode when all of the plurality of signals representing the phase difference, detected immediately after a duty ratio of the pulse-width-modulated driving voltage is increased by a predetermined amount, indicate that the phase of the driving voltage is advanced from the phase of the rotor position.

A control device for a brushless DC motor having an armature and a rotor, the control device comprising:

• an inverter having semiconductor switching elements for switching DC current on and off and supplying multi-phase driving voltage to the armature;
• means for starting and accelerating the motor to a predetermined rotational speed by controlling the inverter under a start-up-drive mode;
• means for detecting an angular position of the rotor based on voltage induced in the armature;
• means for driving the motor by controlling the inverter based on the detected angular position of the rotor under a self-controlled-drive mode;
• means for detecting a chase difference between a phase of the detected angular position of the rotor and a phase of the driving voltage supplied to the armature;
• and
• means for switching drive modes from the start-up-mode to the self-controlled-mode, wherein:
• the switching means switches the start-up-drive mode to the self-controlled-drive mode based on a plurality of signals representing the phase difference detected in a predetermined period of time, and
• wherein the switching means does not switch the start-up-drive mode to the self-controlled-drive mode when a part of the plurality of signals representing the phase difference indicates that the phase of the driving voltage is delayed from the phase of the rotor position.