Power tool having a universal motor capable of being powered by AC or DC power supply

• US 10,333,454 B2
• Filed: 11/20/2017
• Issued: 06/25/2019
• Est. Priority Date: 05/18/2014
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Forster, Michael K., Vanko, John C., White, Daniel J., Gorti, Bhanuprasad V.
• Primary Examiner(s): Dhakal, Bickey
• Assistant Examiner(s): Bouziane, Said
• Application Number:
  US15/817,383
• Publication Number:
  US 20180090978A1
• Time in Patent Office: 582 Days
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: B25F 5/02 Construction of casings, bodies or handles B25F5/006, B25F5/008 take precedence
• CPC Class Codes: H01M 10/0445 Multimode batteries, e.g. containing auxiliary cells or electrodes switchable in parallel or series connections
• CPC Class Codes: H01M 10/4207 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/425 Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing printed circuits H05K1/00
• CPC Class Codes: H01M 10/441 for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H01M 2220/30 Batteries in portable systems, e.g. mobile phone, laptop
• CPC Class Codes: H01M 50/213 adapted for cells having curved cross-section, e.g. round or elliptic H01M50/209, H01M50/216 take precedence
• CPC Class Codes: H01M 50/244 Secondary casings; Racks; Suspension devices; Carrying devices; Holders characterised by their mounting method
• CPC Class Codes: H01M 50/247 specially adapted for portable devices, e.g. mobile phones, computers, hand tools or pacemakers
• CPC Class Codes: H01M 50/296 characterised by terminals of battery packs terminals of batteries H01M50/543
• CPC Class Codes: H01M 50/588 outside the batteries, e.g. incorrect connections of terminals or busbars
• CPC Class Codes: H01M 50/597 Protection against reversal of polarity
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 7/00045 Authentication, i.e. circuits for checking compatibility between one component, e.g. a battery or a battery charger, and another component, e.g. a power source
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0024 Parallel/serial switching of connection of batteries to charge or load circuit
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits
• CPC Class Codes: H02J 7/0045 concerning the insertion or the connection of the batteries
• CPC Class Codes: H02J 7/007 : Regulation of charging or discharging current or voltage
• CPC Class Codes: H02J 7/00714 : in response to battery charging or discharging current
• CPC Class Codes: H02J 7/02 : for charging batteries from ac mains by converters
• CPC Class Codes: H02J 7/36 : Arrangements using end-cell switching
• CPC Class Codes: H02P 25/14 : Universal motors H02P25/12 takes precedence
• CPC Class Codes: H02P 27/08 : with pulse width modulation
• CPC Class Codes: H02P 29/00 : Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors arrangements for starting electric motors H02P1/00; arrangements for stopping or slowing electric motors H02P3/00; control of motors that can be connected to two or more different electric power supplies H02P4/00; regulating or controlling the speed or torque of two or more electric motors H02P5/00; vector control H02P21/00
• CPC Class Codes: H02P 29/024 : Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
• CPC Class Codes: H02P 29/0241 : the fault being an overvoltage
• CPC Class Codes: H02P 29/032 : Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

A power tool is provided including an electric universal motor. A power supply interface is arranged to receive at least one of Alternating Current (AC) power from an AC power supply having a first nominal voltage higher than the operating voltage of the motor, or Direct Current (DC) power from a DC power supply having a second nominal voltage that falls approximately within the operating voltage range of the motor. The power supply interface outputs the AC power via an AC power line and the DC power via a DC power line. A motor control circuit supplies electric power from one of the AC power line or the DC power line via a common node, and reduces a supply of power from the AC power line to a level corresponding to the operating voltage of the operating voltage range of the motor.

Claims

1. A power tool comprising:

a housing;

a universal motor having a positive terminal, a negative terminal, and a commutator engaging a pair of brushes coupled to the positive and the negative terminals, the motor being configured to operate within an operating voltage range;

a power supply interface arranged to receive at least one of Alternating Current (AC) power from an AC power supply having a first nominal voltage or Direct Current (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, wherein the second nominal voltage falls approximately within the operating voltage range of the motor, but the first nominal voltage is substantially higher than the operating voltage range of the motor; and

a motor control circuit configured to supply AC power from the AC power line or DC power from the DC power line via a common node to the motor such that the brushes are electrically coupled to one of the AC or DC power supplies, the motor control circuit being configured to reduce a supply of power from the AC power line to the motor to a level corresponding to the operating voltage of the operating voltage range of the motor, wherein the motor control circuit comprises;

a phase-controlled AC switch disposed in series with the AC power line, and

a control unit configured to control a phase of the AC switch, the control unit setting a fixed conduction band for the AC switch corresponding to the difference between the first nominal voltage and the operating voltage range of the motor, the fixed conduction band being less than 180 degrees to reduce an average voltage amount on the AC line to a level that falls within the operating voltage range of the motor.

2. The power tool of claim 1, wherein the motor control circuit comprises a control unit coupled to a power switch arranged on the DC power line, the control unit being configured to monitor a fault condition associated with the DC power supply and turn the power switch off to cut off a supply of power from the DC power supply to the motor.

3. 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, wherein the power supply 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 double-pole double-throw switch arranged between the common node of the AC and DC power lines and the power supply interface, and/or at least one single-pole double-throw switch having an output terminal coupled to the common node of the AC and DC power lines.

4. The power tool of claim 1, wherein the DC power supply comprises a high rated voltage battery pack with the second nominal voltage being in the range of approximately 100V to 120V.

5. The power tool of claim 1, wherein the DC power supply comprises at least two medium-rated voltage battery packs and the power supply interface is configured to connect two or more of the at least two battery packs in series to obtain the second nominal voltage being in the range of approximately 100V to 120V.

6. The power tool of claim 1, wherein the operating voltage range of the motor is approximately within a range of 100V to 120V encompassing the second nominal voltage, the first nominal voltage is in the range of 220 VAC to 240 VAC, and the control unit is configured to set the fixed conduction band of the AC switch to a value within the range of 100 to 140 degrees.

7. The power tool of claim 1, wherein the operating voltage range of the motor is approximately within a range of 60V to 90V encompassing the second nominal voltage, the first nominal voltage is in the range of 100 VAC to 120 VAC, and the control unit is configured to set the fixed conduction band of the AC switch to a value within the range of 70 to 110 degrees.

8. The power tool of claim 1, wherein the control unit is configured to operate the tool at constant speed at the fixed conduction band.

9. The power tool of claim 1, wherein the AC switch includes a phase controlled switch comprising one of a triac, a thyristor, or a SCR switch, and the controller is configured to control a phase of the AC switch according to a desired speed of the motor.

10. The power tool of claim 1, wherein the motor control circuit further comprising a DC switch circuit arranged between the DC power line and the motor, wherein the control unit is configured to control a switching operation of the DC switch circuit or the AC switch to control a speed of the motor enabling variable speed operation of the motor at constant load.

11. The power tool of claim 10, wherein the DC switch circuit comprises one or more controllable semiconductor switches configured in at least one of a chopper circuit, a half-bridge circuit, or a full-bridge circuit, and the control unit is configured to control a pulse-width modulation (PWM) duty cycle of the one or more semiconductor switches according to a desired speed of the motor.

12. The power tool of claim 10, wherein the control unit is configured to vary a conduction angle of the AC switch from zero up to the fixed conduction band according to a desired speed of the motor.

13. The power tool of claim 10, wherein the control unit 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 one or the other of the DC switch circuit or the AC switch based on the mode of operation.

14. A power tool comprising:

a housing;

a universal motor having a positive terminal, a negative terminal, and a commutator engaging a pair of brushes coupled to the positive and the negative terminals, the motor being configured to operate within an operating voltage range;

a power supply interface arranged to receive at least one of Alternating Current (AC) power from an AC power supply having a first nominal voltage or Direct Current (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, wherein the second nominal voltage falls approximately within the operating voltage range of the motor, but the first nominal voltage is substantially higher than the operating voltage range of the motor; and

a motor control circuit configured to supply electric power from one of the AC power line or the DC power line via a common node to the motor such that the brushes are electrically coupled to one of the AC or DC power supplies, the motor control circuit being configured to reduce a supply of power from the AC power line to the motor to a level corresponding to the operating voltage of the operating voltage range of the motor,

wherein the motor control circuit comprises;

a power switching unit including a diode bridge and a controllable semiconductor switch nested within the diode bridge, wherein the AC and DC power lines of the power supply interface are jointly coupled to a first node of the diode bridge and the motor is coupled to a second node of the diode bridge; and

a control unit configured to control a switching operation of the semiconductor switch to control a speed of the motor enabling variable speed operation of the motor at constant load, wherein the control unit is configured to control a phase of the AC power line via the semiconductor switch.

15. A power tool comprising:

a housing;

an electric universal motor having a positive terminal, a negative terminal, and a commutator engaging a pair of brushes coupled to the positive and the negative terminals;

a power supply interface arranged to receive at least one of Alternating Current (AC) power from an AC power supply or Direct Current (DC) power from a DC power supply, and to output the AC power via an AC power line and the DC power via a DC power line;

a power switching unit comprising a diode bridge and a controllable semiconductor switch nested within the diode bridge, wherein the AC and DC power lines of the power supply interface are jointly coupled to a first node of the diode bridge and the motor is coupled to a second node of the diode bridge; and

a control unit configured to control a switching operation of the semiconductor switch to control a speed of the motor enabling variable speed operation of the motor at constant torque.

16. The power tool of claim 15, wherein the control unit 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 semiconductor switch according to the mode of operation.

17. The power tool of claim 16, wherein, in the DC mode of operation, the control unit is configured to set a pulse-width modulation (PWM) duty cycle according to a desired speed of the motor and turn the semiconductor switch on and off periodically in accordance with the PWM duty cycle, and, in the AC mode of operation, the control unit is configured to set a conduction band according to a desired speed of the motor and, within each AC line half-cycle, turn the semiconductor switch ON at approximately the beginning of the conduction band and turn the semiconductor switch OFF at approximately a zero crossing of the AC power line.

18. The power tool of claim 15, wherein the power tool further comprises a second semiconductor switch and a freewheel diode disposed in series with the motor to allow a current path for a motor current during an off-cycle of the semiconductor switch in the DC mode of operation.

19. The power tool of claim 15, wherein the semiconductor switch comprises one of a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT).

20. The power tool of claim 15, wherein the diode bridge is arranged to rectify the AC power line through the semiconductor switch, but not through the motor.

21. The power tool of claim 15, wherein the power switching unit is arranged between the common node of the AC and DC power lines.