Apparatus for driving brushless motor and method of controlling the motor

A method of controlling a multi-pole, brushless motor equipped with a plurality of multi-phase stator coils, the method comprising:

• determining an elapsed time from a falling edge of a driving voltage to a rising edge of a counter-electromotive voltage in an unexcited state of the brushless motor;
• determining a phase commutation point of time depending on the determined elapsed time;
• and
• performing phase commutation at the determined phase commutation point of time.

A method of controlling a brushless motor performing phase commutation at a reference time determined based on a counter-electromotive voltage induced from an unexcited stator coil, the method comprising:

• determining an elapsed time from a falling edge of an unexcited driving voltage to a rising edge of the counter-electromotive voltage;
• determining whether the counter-electromotive voltage reaches a preset point;
• and
• determining a time earlier than the reference point of time by a reduced amount of a delay time corresponding to the determined elapsed time, upon the counter-electromotive voltage reaching the preset point, as a phase commutation point of time.

A method of controlling a brushless motor equipped with a plurality of multi-phase stator coils, the method comprising:

• determining an elapsed time from a first edge of a first voltage to a second edge of a second voltage for an unexcited state of the brushless motor;
• determining a time for phase commutation depending on the determined elapsed time;
• and
• performing phase commutation at the phase commutation point of time.

A method of controlling a brushless motor performing phase commutation at a reference time determined based on a first voltage induced from an unexcited stator coil, the method comprising:

• determining an elapsed time from a first edge of an unexcited second voltage to a rising edge of the first voltage;
• determining whether the first voltage reaches a preset point;
• and
• determining a time earlier than the reference point of time by a reduced amount of a delay time corresponding to the determined elapsed time, upon the first voltage reaching the preset point, as a phase commutation point of time.

A method of controlling a brushless motor, comprising:

• detecting a falling edge of a terminal voltage in an unexcited state in which a driving voltage is turned off;
• upon detection of a rising edge of a counter-electromotive voltage, determining the elapsed time after the detecting the falling edge of the terminal voltage;
• and
• performing phase commutation at a point of time depending on the determined elapsed time.

An apparatus for driving a brushless motor having multi-phase stator coils, comprising:

• an inverter switching at least one voltage applied to the multi-phase stator coils;
• a driver driving the inverter;
• and
• a controller determining an elapsed time required to detect a first voltage after a second voltage is turned off, to determine a phase commutation point of time based on the determined elapsed time, and controlling the driver to perform phase commutation at the determined phase commutation point of time.