A method for determining a rotor position of a BLDC motor with a magnetic rotor and stator having at least one exciter coil to which an exciter voltage is applied in accordance with a commutation process, comprises: interrupting the exciter voltage applied to the exciter coil, wherein the exciter voltage has a profile with at least one first section in which the profile of the exciter voltage has a non-vanishing finite gradient, wherein the exciter voltage in the first section is interrupted, and wherein at the time of interruption the exciter voltage has a value different from zero; capturing a voltage induced in the exciter coil by the magnetic rotor; restoring the exciter voltage to a value different from zero; and determining a rotor position of the rotor with respect to the exciter coil on the basis of the captured induced voltage.

A measuring circuit (100) is described, for the voltage of an electric machine comprising a first operational amplifier (20) having its non-inverting input (5) connected to a non-inverting input (10) of at least one second operational amplifier (30), and its output (7) feedback connected, through a resistance (R5), to the inverting input (6), the inverting input (6) of the first operational amplifier (20) being further connected through a resistance (R6) to a first phase (C) of the input current to an electric machine, the output (7) of the first operational amplifier (20) being connected, through a resistance (R8), to the inverting input (2) of a third operational amplifier (40) which has its non-inverting input (3) connected to a reference voltage (VREF), the output (7) of the first operational amplifier (20) being further connected to a first output (VC) of the circuit, which is at a voltage value equal to the voltage of a first phase of the electric machine to be measured, said third operational amplifier (40) having its output (1) feedback connected, through a capacitance (Cl), to the inverting input (2), the output (1) of the third operational amplifier (40) being further connected through a resistance (R10) to the non-inverting input (5) of the first operational amplifier (20) and to the non-inverting input (10} of the second operational amplifier (30); a system and a process for calibrating electric machines using such circuit (100) are further described.

A method and apparatus are provided for controlling a sensorless multi-phase permanent magnet (PM) motor by sensing induced motor terminal voltages from the PM motor while the rotor is spinning, generating an input voltage vector signal from the plurality of induced motor terminal voltages, projecting the input voltage vector signal to a transformed voltage vector signal which does not include DC-offset components by using a Clarke transformation without a zero component that is applied to the input voltage vector signal, and estimating an initial rotor position of the rotor from the transformed voltage vector signal, wherein said sensing, projecting, and estimating are performed while a power converter for the sensorless multi-phase PM motor is disabled.

A motor drive circuit includes: a PWM signal generation part configured to generate a PWM signal based on a count value of a counter; a detection part configured to detect a zero crossing of a counter electromotive voltage generated in a coil of a motor; a prediction part configured to predict an arrival timing of the zero crossing of the counter electromotive voltage; a stop part configured to stop a counting operation of the counter after a first time point going back from the arrival timing predicted by the prediction part; and a reset part configured to reset the count value at a timing at which the detection part detects the zero crossing of the counter electromotive voltage.

A motor drive circuit includes: a PWM signal generation part configured to generate a PWM signal based on a count value of a counter; a detection part configured to detect a zero crossing of a counter electromotive voltage generated in a coil of a motor; a prediction part configured to predict an arrival timing of the zero crossing of the counter electromotive voltage; a stop part configured to stop a counting operation of the counter after a first time point going back from the arrival timing predicted by the prediction part; and a reset part configured to reset the count value at a timing at which the detection part detects the zero crossing of the counter electromotive voltage.

A blower motor control device stops energization to a motor when a rotation speed of a rotor reaches a learn rotation speed, and acquires a correction amount as a new learn value for correcting a position error of the rotor relative to a Hall element by using an induced voltage in a coil of the motor and a detection signal from a rotation sensor. The blower motor control device stores the new learn value in a ROM. The blower motor control device corrects the position error by using a previous learn value read from the ROM, for energization control of the motor, until the rotation speed reaches the learn rotation speed.

A sensor-less detection circuit includes a first voltage adjustment circuit providing a first output voltage at a first node using one of three input voltages. A second voltage adjustment circuit provides a second output voltage at a second node using all three, or only two, of the three input voltages. The second voltage adjustment circuit acts as an internal virtual neutral point for detecting a zero crossing event of the motor. A differential amplifier is coupled with the first and second nodes and outputs a third output voltage at a third node. A reference buffer has a reference voltage input and provides a fourth output voltage at a fourth node. A comparator is coupled with the third and fourth nodes and outputs a fifth output voltage at a fifth node, the fifth voltage indicating a zero cross event.

A sensor-less detection circuit includes a first voltage adjustment circuit providing a first output voltage at a first node using one of three input voltages. A second voltage adjustment circuit provides a second output voltage at a second node using all three, or only two, of the three input voltages. The second voltage adjustment circuit acts as an internal virtual neutral point for detecting a zero crossing event of the motor. A differential amplifier is coupled with the first and second nodes and outputs a third output voltage at a third node. A reference buffer has a reference voltage input and provides a fourth output voltage at a fourth node. A comparator is coupled with the third and fourth nodes and outputs a fifth output voltage at a fifth node, the fifth voltage indicating a zero cross event.

A method of driving a three-phase motor includes, while a first phase is energized, driving a second phase using a first drive function which is sinusoidal. The first phase is switched to a non-energized state and a back electromotive force (BEMF) voltage of the first phase is detected. For at least a portion of a time when the first phase is non-energized the driving of the second phase depends on the output of a second drive function different from the first drive function. The second drive function may be non-sinusoidal and may be a cosine function. The second drive function may drive the second phase when the output of the second drive function is a modulation ratio less than 1. When the output of the second drive function is a modulation ratio greater than or equal to 1 the second phase may be driven to a modulation ratio of 1.

A method of driving a three-phase motor includes, while a first phase is energized, driving a second phase using a first drive function which is sinusoidal. The first phase is switched to a non-energized state and a back electromotive force (BEMF) voltage of the first phase is detected. For at least a portion of a time when the first phase is non-energized the driving of the second phase depends on the output of a second drive function different from the first drive function. The second drive function may be non-sinusoidal and may be a cosine function. The second drive function may drive the second phase when the output of the second drive function is a modulation ratio less than 1. When the output of the second drive function is a modulation ratio greater than or equal to 1 the second phase may be driven to a modulation ratio of 1.