Startup control method of brushless DC motor

A startup control method for controlling startup of a brushless direct current (BLDC) motor by commutating a current applied to stator windings according to a rotor position, comprising:

• forcibly aligning the rotor position, and performing phase commutation;
• detecting back-electromotive force (back-emf) from a lead voltage of a phase of a voltage which is not applied thereto after performing the phase commutation, and determining whether the detected back-emf is in a rising interval;
• integrating the lead voltage of the phase of the voltage which is not applied thereto if the back-emf is in a rising interval, and setting a time point that the integration result is greater than a predetermined value as a phase commutation time point;
• setting a time point that a phase current value is greater than a predetermined value as a phase commutation time point if the back-emf is in a falling interval;
• and
• converting the commutation time point to a sensorless operation mode if the back-emf detected from the lead voltage is in a stable interval based on a frequency of the voltage applied to the stator windings.

A startup control method of a brushless direct current (BLDC) motor by commutating a current applied to stator windings according to a rotor position, comprising:

• detecting back-electromotive force (back-emf) from a lead voltage of a phase of a voltage which is not applied thereto after performing the phase commutation, and determining whether the detected back-emf is in a rising interval;
• setting a time point that a phase current value is greater than a predetermined value as a phase commutation time point if the back-emf is in a falling interval;
• and
• converting the commutation time point to a sensorless operation mode if the back-emf detected from the lead voltage is in a stable interval based on a frequency of the voltage applied to the stator windings.

A startup control method for controlling startup of a brushless direct current (BLDC) motor comprising:

• commutating a current applied to stator windings according to a rotor position;
• forcibly aligning the rotor position and performing phase commutation;
• detecting back-electromotive force (back-emf) from a lead voltage of a phase of a voltage which is not applied thereto after performing the phase commutation, and determining whether the detected back-emf is in a rising interval;
• determining phase commutation time point based on current waveform;
• and
• converting to a sensorless operation mode if the back-emf detected from the lead voltage is in a stable interval, based on a frequency of the voltage applied to the stator windings.

A startup control method for controlling startup of a brushless direct current (BLDC) motor by commutating a current applied to stator windings according to a rotor position, comprising:

• performing phase commutation;
• detecting a zero crossing point (ZCP) of the back-emf from each lead voltage;
• and
• performing a sensorless operation mode based on ZCP information, wherein the sensorless operation includes a phase commutation and speed control.

A startup control apparatus comprising:

• a sensorless driving device comprising:
• a rectifying unit to rectify and smooth an AC power supply;
• an inverter to convert the DC power from the rectifying unit into AC power having a plurality of phases;
• a lead voltage detection unit to detect a lead voltage of each of the plurality of phases;
• a current detection unit to detect current of the DC source supplied to the inverter from the rectifying unit;
• a controlling unit to detect a zero crossing point of back-emf according to the lead voltage of the each of the plurality of phases;
• and
• a PWM signal generation unit to PWM signals based on the output of the controlling unit to supply said PWM signals to the inverter,
• wherein a converting unit converts a commutation time point to a sensorless operation mode if the back-emf detected from the lead voltage is in a stable interval based on a frequency of the voltage applied to the stator windings.