At time of startup, a rotation controlling section for controlling a rotor of a brushless motor supplies power to an excitation coil of one phase among excitation coils of three phases limitedly for a predetermined time. An induced voltage measurement section measures an induced voltage generated in another excitation coil than the excitation coil to which the power was supplied and based on the result of this measurement, possibility/impossibility of startup is decided. Based on the result of this decision, an excitation coil of one phase among the excitation coils of three phases is set as a supply starting coil to which power is to be supplied first and forced commutation is carried out.

A device for controlling a motor having a stator and a rotor, the stator being provided with at least one winding, the motor being controlled by a control module, the control device including: at least one transformation module for transforming a source signal taken from at least one of the terminals of the winding into a floating image signal representative of a counter-electromotive force induced in the winding. The transformation module has: a time constant determined from characteristics of the motor and/or characteristics of the control module; at least one first terminal connected to at least one of the terminals of the winding, and a second terminal, the first and second terminals being likely to have floating potential relative to the fixed reference terminal.

A circuit, comprising a plurality of phase windings in an electric motor, an inverter configured to excite the phase windings by a sequence of voltage pulses including a plurality of successive voltage pulses that a current can be set in each of the phase windings, wherein the voltage pulses are selected in such a manner that a positive and a negative current are produced in all the phase windings during the voltage pulses, a current sensor for measuring a peak value for the current being set during a duration of each voltage pulse in each phase winding, and an evaluation circuit connected to the current sensor, wherein the evaluation circuit is configured to determine the voltage pulse in the voltage pulse sequence during a duration of which peak current value having a greatest magnitude was measured.

A first line-to-line terminal voltage of a three-phase electric motor is measured while the three-phase electric motor free-spins. A second line-to-line terminal voltage of a three-phase electric motor is measured while the three-phase electric motor free-spins. A motor's rotor position is determined based on the first line-to-line terminal voltage and the second line-to-line terminal voltage. Three-phase current is sent to the motor after the rotor position has been determined. The three-phase current being in-phase with the rotor position.

Utilizing an asymmetric magnetic field caused by a mechanism design between a motor rotor and a stator to induce a BEMF, a method for starting a fixed rotation direction of single-phase sensorless DC brushless motor, includes: power-on starting a motor control circuit; if the motor is not in a rotating state before starting the excitation, executing a static starting procedure; then, if the motor rotation direction conforms to a predetermined direction, executing a normal driving procedure; otherwise, executing a static starting procedure. The static starting procedure, by discharging remnant energy of the motor, achieves the purpose of star-up by performing the steps of first phase excitation, stop excitation, and strong second phase excitation. In the normal driving procedure, the slope of BEMF signal of the first phase or the second phase is taken out periodically to detect the motor rotation direction.

A detector detects whether or not a first line induced voltage and a second line induced voltage match each other, the first line induced voltage being a potential difference of a first phase potential of phase potentials relative to a reference potential, and the second line induced voltage being a potential difference of a second phase potential of the phase potentials other than the first phase potential relative to the reference potential. The phase potentials is outputted by the armature due to an induced electromotive force. The reference potential is any one of a minimum phase and a maximum phase. A rotation-position setting unit sets, to a predetermined value, an estimation value of a rotation position of the motor 2 at a point in time when the first line induced voltage and the second line induced voltage match each other.

A motor controller comprises a switch circuit and a control unit. The switch circuit is coupled to a motor for driving the motor. The control unit is configured to generate a control signal to control the switch circuit. The motor controller is configured to generate a current signal and a voltage signal. When a current phase of the current signal is at a predetermined crossing phase, the motor controller calculates a difference value between the current phase of the current signal and a voltage phase of the voltage signal, where the motor controller is configured to control the difference value. The motor controller may stabilize the motor and avoid noise by modulating the difference value. The motor controller may modulate the difference value, such that the difference value is equal to a predetermined phase difference.

The invention utilizes an asymmetric magnetic field caused by a mechanism design between a motor rotor and a stator to induce a BEMF, and discloses a method for starting a fixed rotation direction of single-phase sensorless DC brushless motor, including: power-on starting a motor control circuit; if the motor not in the rotating state before starting the excitation, executing a static starting procedure; then, if the motor rotation direction conforming to the predetermined direction, executing a normal driving procedure; otherwise, executing a static starting procedure. The static starting procedure, after of static starting by discharging remnant energy of the motor, achieves the purpose of star-up by performing the steps of first phase excitation, stop excitation, and strong second phase excitation. In the normal driving procedure, the slopes of BEMF signal of the first phase or the second phase is taken out periodically to detect the motor rotation direction.

A first line-to-line terminal voltage of a three-phase electric motor is measured while the three-phase electric motor free-spins. A second line-to-line terminal voltage of a three-phase electric motor is measured while the three-phase electric motor free-spins. A motor's rotor position is determined based on the first line-to-line terminal voltage and the second line-to-line terminal voltage. Three-phase current is sent to the motor after the rotor position has been determined. The three-phase current being in-phase with the rotor position.

A circuit, comprising a plurality of phase windings in an electric motor, an inverter configured to excite the phase windings by a sequence of voltage pulses including a plurality of successive voltage pulses that a current can be set in each of the phase windings, wherein the voltage pulses are selected in such a manner that a positive and a negative current are produced in all the phase windings during the voltage pulses, a current sensor for measuring a peak value for the current being set during a duration of each voltage pulse in each phase winding, and an evaluation circuit connected to the current sensor, wherein the evaluation circuit is configured to determine the voltage pulse in the voltage pulse sequence during a duration of which peak current value having a greatest magnitude was measured.