Disclosed herein is a control circuit of a three-phase DC motor used along with an external resistance and a three-phase inverter. The control circuit includes a current detection circuit that generates a first current detection value indicating an amount of current of a first current flowing through a first phase of the three-phase inverter. The current detection circuit can generate the first current detection value, based on a voltage drop of a resistance component of a wire existing on a path of the first current, the wire being formed from a material containing copper, or based on a voltage drop of a first resistance that is an on-resistance of an arm of the first phase, and can use, as a standard, a current detection value based on a voltage drop of the external resistance to calibrate the first current detection value based on the voltage drop of the first resistance.

The present invention relates to a method for controlling a bus current of a brushless DC electric motor, comprising: obtaining currents of three phases of a stator; converting the currents of the three phases to a direct-axis current and a quadrature-axis current; based on the direct-axis current, the quadrature-axis current and an efficiency ratio of the electric motor, determining a bus current of the electric motor, wherein the efficiency ratio corresponds to a present operating condition of the electric motor. The method does not need to introduce shunt resistors on the bus, and also enables closed-loop control of bus current.

A gate drive semiconductor device includes: external terminals to which PWM control signals are supplied; external terminals outputting a drive signal for driving a three-phase BLDC motor; external terminals to which the counter electromotive voltage generated by driving the three-phase BLDC motor is supplied; a zero-cross determination unit generating an interrupt signal indicating timing at which the counter electromotive voltage intersects with a midpoint potential of the three-phase BLDC motor based on the PWM control signal and the counter electromotive voltage; and an external terminal outputting the interrupt signal.

An operation controlling apparatus of a reciprocating compressor includes: a detector configured to detect a torque output by a motor of the reciprocating compressor, a rotation speed of the motor, a counter electromotive voltage of the motor, and a current applied to the motor; a controller configured to determine a mode switching time point for switching an operation mode of the reciprocating compressor based on the torque, the rotation speed, the counter electromotive voltage, and the current of the motor, and output a control signal for changing a wire ratio of the motor corresponding to the operation mode; and a driver configured to change the wire ratio of the motor based on the control signal and operate the reciprocating compressor in the operation mode among at least two operation modes.

Methods and power tools for sensorless motor control. One embodiment provides a method for automatic control switching for driving a sensorless motor (150) of a power tool (100). The method includes determining, using a motor controller (224), a first load point based on user inputs (232) and determining, using the motor controller (224), a first motor control technique corresponding to the first load point. The method also includes driving the motor (150) based on the first motor control technique. The method further includes determining, using the motor controller (224), a change from the first load point to a second load point and determining, using the motor controller (224), a second motor control technique corresponding to the second load point. The method includes driving the motor (150) based on the second motor control technique.

An electromagnetic interference reducing circuit is provided. A first random number generator generates a plurality of first random number signals each having a plurality of triangular waves. Each of the triangular waves has a plurality of steps. The first random number generator generates a plurality of first random numbers and modulates each of the first random number signals according to the first random numbers. The first random number generator repeatedly counts, repeatedly removes, or does not count time of the steps of each of the triangular waves of each of the first random number signals according to one of the first random numbers. A first oscillator generates a first oscillating signal. A motor controller circuit controls a plurality of switch components of a motor respectively according to the first random number signals based on the first oscillating signal.

A method for braking a single coil BLDC motor includes iterating a plurality of times through a sequence of: a braking state which lasts a braking period; and a high impedance state which lasts a cool down period. The current runs through the single coil during the braking state and no current runs through the single coil during the high impedance state. The transiting from the braking state to the high impedance state is done when the motor operates in generator mode.

A power tool has a functional component, a motor, a power supply module, a controller and a drive circuit including a first drive terminal and a second drive terminal respectively electrically connected to a first power terminal and a second power terminal of the power supply module, multiple high-side switches wherein high-side terminals of the high-side switches are respectively electrically connected to the first drive terminal, and multiple low-side switches wherein low-side terminals of the low-side switches are respectively electrically connected to the second drive terminal. The controller is configured to output a first control signal to one high-side switch to place it in an on or off state and output a second control signal to one low-side switch to place it in the other state. The low-side terminal of one high-side switch is connected to the high-side terminal of one low-side switch.

A gate driving circuit applied to motor inverter includes first power switch circuit, first and second bootstrap fast charging circuits, and first, second and third capacitors. The first power switch circuit includes first and second power switches. The first bootstrap fast charging circuit is electrically connected to the first power switch. The second bootstrap fast charging circuit is electrically connected to the second power switch. The first capacitor is electrically connected to the first power switch. The second capacitor is electrically connected to the first bootstrap fast charging circuit and first insulated switch. The third capacitor is electrically connected to the second bootstrap fast charging circuit and second insulated switch. When the first power switch is disabled and the second power switch is enabled, an independent power supply enables the second bootstrap fast charging circuit to charge the third capacitor to enable the second insulated switch.

A method for identifying parameters, such as a magnetization-axis and torque-axis inductances, of a permanent magnet motor of an elevator includes applying, such as by a brake controller, at least one hoisting machinery brake to prevent rotation of a rotor of the permanent magnet motor, determining, by a first method, a mean value of motor inductance, as well as the magnetization-axis inductance and the torque-axis inductance as relative inductance values based on the mean value, determining, by a second method, being different than the first method, a mean value of motor main inductances, and determining absolute values of the magnetization-axis and the torque axis inductances based on the motor main inductance obtained by the second method and the relative inductance values obtained by the first method.