A method for detecting a potential (Vn) includes stator wirings in a Y connection, and automatically adjusting a relationship with a position of a rotor as a system for realizing rotor position-sensorless stable drive of an AC motor where the three-phase stator wirings are in Y connection in the stop and low-speed ranges. A synchronous motor control apparatus includes a three-phase synchronous motor in which three-phase stator wirings are in a Y connection, and an inverter for driving the motor, wherein the synchronous motor is DC-conducted thereby to move a rotor to a predetermined position, and is applied with a pulse-shaped voltage from the inverter in the moved state so that a neutral point potential as potential (Vn) of the Y connection point is acquired when the pulse voltage is applied, thereby driving the synchronous motor based on the acquired value.

A device and control method for driving a sensorless brushless DC (BLDC) motor, particularly related to a technology configured to increase the accuracy of detection of Zero Cross Point through a non-commutation period in a pulse width modulation (PWM) control. The device for driving a sensorless BLDC motor to switch a current applied to a stator winding based on a position of a rotor includes a three phase inverter configured to convert a DC input voltage into a three phase AC voltage and supply the three phase AC voltage to the BLDC motor; a terminal voltage detector configured to detect a three phase terminal voltage from an output terminal of the three phase inverter; and a controller configured to perform a PWM control of the terminal voltage based on a three phase back electromotive force (EMF) included in the detected terminal voltage. The PWM control includes a non-commutation control in which the switching of the current does not occur.

A motor driving device of the present invention includes: a driver that receives supply of a power supply voltage to apply a plurality of phase voltages to a motor; a voltage-division phase voltage generation portion that divides each of the phase voltages to generate a plurality of voltage-division phase voltages; a neutral point voltage generation portion that combines and divides the phase voltages to generate a neutral point voltage; a selector that outputs any one of the voltage-division phase voltages as a selection voltage-division phase voltage; a comparator that compares the selection voltage-division phase voltage and the neutral point voltage to generate a comparison signal; and a controller that generates a selection control signal of the selector and an energization control signal of the driver according to the comparison signal.

A motor system includes a brushless direct current motor, voltage divider circuits, a switch and an analog-to-digital converter. The brushless direct current motor includes 3 sets of windings, one set of windings being floating during each commutation. There are 3 voltage divider circuits, and each voltage divider circuit includes a first resistor, a second resistor and a bypass diode. The first resistor includes a first terminal coupled to the set of floating windings. The second resistor includes a first terminal coupled to the first resistor, and a second terminal coupled to the switch to receive a control voltage at the second terminal of the second terminal or grounding the second terminal of the second terminal. The bypass diode is coupled in parallel to the first resistor. The analog-to-digital converter receives a divided back-electromotive force signal to determine back-electromotive force zero crossing, so as to perform the commutation.