A method for generating a set of pulse-width modulation control signals for a multi-level power converter. The method includes generating a base reference signal for each of three or more reference phases and determining a maximum reference and minimum reference. The method includes calculating a reference sum of the maximum reference and the minimum reference and generating a first offset and a second offset based on the reference sum. The method includes for each of the three reference phases generating an upper PWM output and a lower PWM output. The method includes combining the upper PWM output and lower PWM output to generate a multi-level PWM control signal for the reference phase and outputting a set of multi-level PWM control signals generated for the three or more reference phases.

A method for generating a set of pulse-width modulation control signals for a multi-level power converter. The method includes generating a base reference signal for each of three or more reference phases and determining a maximum reference and minimum reference. The method includes calculating a reference sum of the maximum reference and the minimum reference and generating a first offset and a second offset based on the reference sum. The method includes for each of the three reference phases generating an upper PWM output and a lower PWM output. The method includes combining the upper PWM output and lower PWM output to generate a multi-level PWM control signal for the reference phase and outputting a set of multi-level PWM control signals generated for the three or more reference phases.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to apply a drive signal to the power switch circuit to control the supply of power to the brushless motor. The controller is configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor within a variable speed range of zero to at least 15,000 rotations-per-minute (RPM), and control the drive signal based on the detected angular position of the rotor to electronically commutate the motor within a torque range of zero to at least 15 newton-meters (N.m.) and a power output of zero to at least 1500 watts.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor, and apply a drive signal to the power switch circuit to control a commutation of the motor based on the detected angular position of the rotor. The controller detects an initial sector within which the rotor is located at start-up, apply the drive signal so as to rotate the motor to a parking angle associated with the detected initial sector, and control a commutation sequence to drive the motor beginning at the parking angle.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor, and apply a drive signal to the power switch circuit to control a commutation of the motor based on the detected angular position of the rotor. If the supply of power to the motor is turned OFF to cause the motor to slow down and is turned back ON while the rotor speed exceeds a speed threshold, the controller electronically brakes the motor for a time interval to measure the phase current of the motor and detects the angular position of the rotor based on the measured phase current.

The present invention addresses the problem of providing a method for detecting magnetic field location which can realize low cost by using simple hardware and software and can detect a rotor location in units of excitation sections in 120-energization without generating sensing noise at the time of initiation. As a solution, an MPU (51) obtains, through calculation, a neutral point potential from an energization-phase voltage measured by an A/D conversion circuit (53), obtains the difference between the neutral point potential and a non-energization-phase voltage, performs magnitude comparison between the difference and a negative-side threshold value in the case where the present location is an odd-numbered section or between the difference and a positive-side threshold value in the case where the present location is an even-numbered section, and determines the end point of the 60-energization section when the difference exceeds a threshold value in a direction away from the neutral point potential.

A motor drive system capable of suppressing heat generation during a low speed operation may include: an inverter including a plurality of switching elements to convert direct current power to alternating current power having a plurality of phases; a motor driven with the alternating current power converted in the inverter; and a controller determines an operating point of the motor on the basis of a torque command of the motor and generates a d-axis current command and a q-axis current command corresponding to the operating point. In particular, when each of the switching elements is overheated, the controller changes the d-axis current command and the q-axis current command by changing the operating point to a different operating point corresponding to a torque of the same magnitude as the torque command.

A motor drive system capable of suppressing heat generation during a low speed operation may include: an inverter including a plurality of switching elements to convert direct current power to alternating current power having a plurality of phases; a motor driven with the alternating current power converted in the inverter; and a controller determines an operating point of the motor on the basis of a torque command of the motor and generates a d-axis current command and a q-axis current command corresponding to the operating point. In particular, when each of the switching elements is overheated, the controller changes the d-axis current command and the q-axis current command by changing the operating point to a different operating point corresponding to a torque of the same magnitude as the torque command.

A driving circuit for a semiconductor circuit which includes a pair of main terminals through which a main current is conducted and a control terminal to which a control voltage is applied to control a circulation state of the main current, includes: driving voltage switching circuitry that receives a control signal, instructs switching between driving voltages based on a change in the control signal, and outputs a driving voltage, among the driving voltages, that has been selected in the switching; low-speed control circuitry that instructs an increase-decrease change in the control voltage at a low speed; speed-increase control circuitry that executes a speed-increase control of increasing a speed of the increase-decrease change made by the low-speed control circuitry; and speed-increase switching circuitry that instructs switching between an execution and a non-execution of the speed-increase control, and instructs switching between levels of a speed-increase change caused by the speed-increase control.

A control device to control a motor includes a stator including a coil, a rotor including a permanent magnet, a detector that detects a rotational position of the rotor at every predetermined angle and outputs a position signal indicating the detected rotational position, and a controller that receives the position signal output by the detector and adjusts a duty ratio of a driving signal of the rotor by a pulse width modulation scheme based on the received position signal to control rotation of the rotor. The controller raises the duty ratio from a first duty ratio, starting from a point in time at which the position signal is received, and returns the raised duty ratio to the first duty ratio when a next position signal has been received.