Power tool having multiple power supplies

Abstract

A power tool includes a housing, a brushless direct current (BLDC) motor including a rotor and a stator having at least three stator windings corresponding to at least three phases of the motor, the rotor being moveable by the stator when the stator windings are appropriately energized within the corresponding phases, each phase being characterized by a corresponding voltage waveform energizing the corresponding stator winding, the motor being configured to operate within an operating voltage range, and a power supply interface arranged to receive at least one of AC power from an AC power supply having a first nominal voltage or DC power from a DC power supply having a second nominal voltage, the power supply interface configured to output the AC power via an AC power line and the DC power via a DC power line. A motor control circuit is provided to receive the AC power line and the DC power line and supply electric power to the motor at a voltage level corresponding to the operating voltage range of the motor from at least one of the AC power supply and/or the DC power supply, the motor control circuit including: a rectifier circuit configured to convert an alternating signal on the AC power line to a rectified voltage signal on a DC bus line, and a power switch circuit configured to regulate a supply of electric power from at least one of the DC bus line and/or the DC power line to the motor.

What is claimed is: 
     
         1 . A power tool comprising:
 a housing;   a brushless direct current (BLDC) motor including a rotor and a stator having at least three stator windings corresponding to at least three phases of the motor, the rotor being moveable by the stator when the stator windings are appropriately energized within the corresponding phases, each phase being characterized by a corresponding voltage waveform energizing the corresponding stator winding, the motor being configured to operate within an operating voltage range;   a power supply interface arranged to receive at least one of AC power from an AC power supply having a first nominal voltage or DC power from a DC power supply having a second nominal voltage, the DC power supply comprising at least one removable battery pack coupled to the power supply interface, the power supply interface configured to output the AC power via an AC power line and the DC power via a DC power line; and   a motor control circuit configured to receive the AC power line and the DC power line and supply electric power to the motor at a voltage level corresponding to the operating voltage range of the motor from at least one of the AC power supply and/or the DC power supply, the motor control circuit including: a rectifier circuit configured to convert an alternating signal on the AC power line to a rectified voltage signal on a DC bus line, and a power switch circuit configured to regulate a supply of electric power from at least one of the DC bus line and/or the DC power line to the motor.   
     
     
         2 . The power tool of  claim 1 , wherein the rectifier circuit comprises a diode bridge. 
     
     
         3 . The power tool of  claim 2 , wherein the rectifier circuit further comprises a link capacitor arranged in parallel to the diode bridge on the DC bus line. 
     
     
         4 . The power tool of  claim 1 , wherein the DC power line is connected directly to a node on the DC bus line bypassing the rectifier circuit. 
     
     
         5 . The power tool of  claim 1 , wherein the DC power line and the AC power line are jointly coupled to an input node of the rectifier circuit. 
     
     
         6 . The power tool of  claim 1 , further comprising a power supply switching unit arranged to isolate the AC power line and the DC power line. 
     
     
         7 . The power tool of  claim 6 , wherein the switching unit comprises at least one of: a relay switch arranged on the DC power line and activated by a coil coupled to the AC power line; at least one single-pole double-throw switch having input terminals coupled to the AC and DC power lines and an output terminal coupled to an input node of the rectifier circuit; and/or at least one double-pole double-throw switch having input terminals coupled to the AC and DC power lines, a first output terminal coupled to the input node of the rectifier circuit, and a second output terminal coupled directly to a node on the DC bus line bypassing the rectifier circuit. 
     
     
         8 . The power tool of  claim 1 , wherein the motor control circuit further comprises a controller configured to control a switching operation of the power switch circuit. 
     
     
         9 . The power tool of  claim 8 , wherein the controller is further configured to monitor a fault condition associated with the power tool or the DC power supply and deactivate the power switch circuit to cut off a supply of power to the motor. 
     
     
         10 . The power tool of  claim 8 , wherein the controller is configured to sense current on one of the AC power line or the DC power line to set a mode of operation to one of an AC mode of operation or a DC mode of operation, and control the switching operation of the power switch circuit based on the mode of operation. 
     
     
         11 . The power tool of  claim 8 , wherein the power switch circuit comprises a plurality of power switches including three pairs of high-side and low-side power switches configured as a three-phase bridge circuit coupled to the phases of the motor. 
     
     
         12 . The power tool of  claim 11 , wherein the motor control circuit further comprises a gate driver circuit arranged between the controller and the power switch circuit, and configured to drive gates of the plurality of power switches based on one or more drive signals from the controller. 
     
     
         13 . The power tool of  claim 12 , wherein the motor control circuit further comprises a power supply regulator including at least one voltage regulator configured to output a voltage signal to power at least one of the gate driver circuit or the controller. 
     
     
         14 . The power tool of  claim 11 , wherein within each phase of the motor, the controller is configured to activate a drive signal for a corresponding one of the plurality of power switches within a conduction band corresponding to the phase of the motor, and set a pulse-width modulation (PWM) duty cycle according to a desired speed of the motor and control the drive signal to turn the corresponding one of the plurality of power switches on and off periodically within the conduction band in accordance with the PWM duty cycle to enable variable speed operation of the motor at constant load. 
     
     
         15 . The power tool of  claim 3 , wherein the first and second nominal voltages both fall approximately within the operating voltage range of the motor. 
     
     
         16 . The power tool of  claim 3 , wherein at least one of first and second nominal voltages does not approximately correspond to the operating voltage range of the motor. 
     
     
         17 . The power tool of  claim 16 , wherein the motor control circuit is configured to optimize a supply of power from at least one of the AC power line or the DC power line to the motor at a level corresponding to the operating voltage range of the motor.