Method and device for braking a motor

• US 20050052145A1
• Filed: 10/22/2004
• Published: 03/10/2005
• Est. Priority Date: 10/18/2002
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Carrier, David A., Gorti, Bhanuprasad V.
• Granted Patent: US 7,075,257 B2
• Time in Patent Office: Days
• US Class Current: 318/381
• CPC Class Codes: H02P 3/12 by short-circuit or resistive braking

Abstract

A method and apparatus for braking a motor has a braking circuit that intermittently shorts the windings of the motor to brake the motor. The braking circuit is powered by back EMF generated by the motor when power is disconnected from the motor.

Claims

1. A method of braking a motor, comprising:

disconnecting power from the motor;

coupling a motor braking circuit to windings of the motor to power the motor braking circuit with back EMF generated by the motor after power to the motor has been disconnected; and

intermittently shorting the windings of the motor with the motor braking circuit to brake the motor.

2. The method of claim 1 wherein intermittently shorting the windings of the motor with the motor braking circuit includes repeatedly switching an electronic switch coupled across the windings of the motor on and off.

3. The method of claim 2 wherein powering the motor braking circuit with back EMF generated by the motor includes charging a storage capacitor with the back EMF and providing power to the motor braking circuit with the storage capacitor.

4. The method of claim 3 wherein repeatedly switching the electronic switch on and off includes generating a series of pulses with the motor braking circuit and pulsing an input of the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

5. The method of claim 4 wherein generating the series of pulses with the motor braking circuit includes generating the series of pulses with a timer of the motor braking circuit.

6. The method of claim 5 wherein the electronic switch includes at least one of a triac, a SCR, a FET, an IGBT and a Darlington pair.

7. The method of claim 2 and further including connecting at least one side of the electronic switch to the motor windings when power to the motor is off and disconnecting the at least one side of the electronic switch to the motor windings when power to the motor is on.

8. The method of claim 7 wherein powering the motor braking circuit with back EMF generated by the motor includes charging a storage capacitor with the back EMF and providing power to the motor braking circuit with the storage capacitor.

9. The method of claim 8 including generating a series of pulses with the motor braking circuit and pulsing the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

10. The method of claim 9 wherein generating the series of pulses with the motor braking circuit includes generating the series of pulses with a timer of the motor braking circuit.

11. The method of claim 10 wherein the electronic switch includes at least one of a triac, a SCR, a FET, an IGBT and a Darlington pair.

12. The method of claim 1 including connecting power to the motor by turning a power switch on and disconnecting power from the motor by turning the power switch off.

13. The method of claim 12 including coupling the braking circuit to the windings of the motor with the power switch to couple the braking circuit to the windings of the motor with the power switch is off and decoupling the braking circuit to the windings of the motor when the power switch is on to decouple the braking circuit to the windings when the power switch is on.

14. A method of braking a motor, comprising:

disconnecting power from the motor;

coupling a motor braking circuit to windings of the motor to charge a storage capacitor of a motor braking circuit with back EMF generated by the motor after power to the motor has been disconnected, the storage capacitor providing power to the motor braking circuit; and

intermittently shorting the windings of the motor with the motor braking circuit to brake the motor.

15. The method of claim 14 wherein intermittently shorting the windings of the motor includes repeatedly switching an electronic switch coupled across the windings of the motor on and off by generating a series of pulses with the motor braking circuit and pulsing an input of the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

16. The method of claim 15 including turning a power switch on to connect power to the motor and decouple the motor braking circuit from the windings of the motor and turning the power switch off to disconnect power from the motor and couple the braking circuit to the windings of the motor.

17. A method for braking a motor, comprising:

connecting power to a motor when a first switch is on and disconnecting power to the motor when the first switch is off;

generating a pulsed output signal with a controller when the first switch is switched off to switch a braking power switching device coupled across windings of the motor on and off to brake the motor;

charging a storage capacitor using back EMF generated by the motor when the first switch is switched off; and

providing power to the controller with the charged storage capacitor.

18. The method of claim 17 including disconnecting power to the controller when the first switch is switched on.

19. The method of claim 18 including coupling the braking power switching device across the windings when the first switch is switched on and decoupling them from the windings when the first switch is switched off.

20. A method of braking a motor in a power tool, comprising:

disconnecting power from the motor;

coupling a motor braking circuit to windings of the motor to power the motor braking circuit with back EMF generated by the motor after the power to the motor has been disconnected; and

intermittently shorting the windings of the motor with the motor braking circuit to brake the motor.

21. The method of claim 20 wherein intermittently shorting the windings of the motor with the motor braking circuit includes repeatedly switching an electronic switch coupled across the windings of the motor on and off.

22. The method of claim 21 wherein powering the motor braking circuit with back EMF generated by the motor includes charging a storage capacitor with the back EMF and providing power to the motor braking circuit with the storage capacitor.

23. The method of claim 22 wherein repeatedly switching the electronic switch on and off includes generating a series of pulses with the motor braking circuit and pulsing an input of the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

24. The method of claim 23 wherein generating the series of pulses with the motor braking circuit includes generating the series of pulses with a timer of the motor braking circuit.

25. The method of claim 24 wherein the electronic switch includes a triac, a SCR, a FET, an IGBT and a Darlington pair.

26. The method of claim 21 and further including connecting at least one side of the electronic switch to the motor windings when power to the motor is off and disconnecting the at least one side of the electronic switch to the motor windings when power to the motor is on.

27. The method of claim 26 wherein powering the motor braking circuit with back EMF generated by the motor includes charging a storage capacitor with the back EMF and providing power to the motor braking circuit with the storage capacitor.

28. The method of claim 27 including generating a.series of pulses with the motor braking circuit and pulsing the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

29. The method of claim 27 wherein the electronic switch includes at least one of a triac, a SCR, a FET, an IGBT and a Darlington pair.

30. The method of claim 20 including connecting power to the motor by turning a power switch on and disconnecting power from the motor by turning the power switch off.

31. The method of claim 30 including coupling the braking circuit to the windings of the motor when the power switch to couple the braking circuit to the windings of the motor with the power switch is off and to decouple the braking circuit to the windings when the power switch is on.

32. A method of braking a motor in a power tool, comprising:

disconnecting power from the motor;

coupling a motor braking circuit to windings of the motor to charge a storage capacitor of a motor braking circuit with back EMF generated by the motor after power to the motor has been disconnected, the storage capacitor providing power to the motor braking circuit; and

intermittently shorting the windings of the motor with the motor braking circuit to brake the motor.

33. The method of claim 32 wherein intermittently shorting the windings of the motor includes repeatedly switching an electronic switch coupled across the windings of the motor on and off by generating a series of pulses of with the motor braking circuit and pulsing an input of the electronic switch with the pulses to repeatedly switch the electronic switch on and off.

34. The method of claim 33 including turning a power switch on to connect power to the motor and decouple the motor braking circuit from the windings of the motor and turning the power switch off to disconnect power from the motor and couple the braking circuit to the windings of the motor.

35. A power tool, comprising:

a housing;

a motor disposed in the housing;

a motor braking circuit;

a power switch for connecting power to the motor and decoupling the motor braking circuit from windings of the motor when the power switch is on and disconnecting power to the motor and coupling the motor braking circuit to the windings of the motor when the power switch is off to power the motor braking circuit with back EMF generated by the motor; and

the motor braking circuit, when powered, intermittently shorting the windings of the motor to brake the motor.

36. The power tool of claim 35 wherein the motor braking circuit includes an braking power switching device coupled across the windings of the motor that is repeatedly turned on and off by the motor braking circuit to intermittently short the windings of the motor.

37. The power tool of claim 36 wherein the motor braking circuit includes a storage capacitor charged by the back EMF generated by the motor that provides power to the motor braking circuit.

38. The power tool of claim 37 wherein the braking power switching device includes an electronic switch and the motor braking circuit includes a timer having an output coupled to an input of the electronic switch, the timer generating a series of pulses that switches the electronic switch on and off.

39. The power tool of claim 38 wherein the electronic switch includes at least one of a triac, a SCR, a FET, an IGBT and a Darlington pair.

40. The power tool of claim 35 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on.

41. The power tool of claim 36 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on, at least one side of the braking power switching device coupled to the windings of the motor through the second switch so that the one side of the braking power switching device is coupled to the windings of the motor when the power switch is off and decoupled from the windings of the motor when the power switch is on.

42. The power tool of claim 41 and further including a diode coupled across the windings of the motor.

43. A power tool, comprising:

a housing;

a motor disposed in the housing;

a motor braking circuit;

a power switch for connecting power to the motor and decoupling the motor braking circuit from windings of the motor when the power switch is on and disconnecting power to the motor and coupling the motor braking circuit to the windings of the motor when the power switch is off to charge a storage capacitor of the motor braking circuit with back EMF generated by the motor; and

the motor braking circuit, when powered, intermittently shorting the windings of the motor to brake the motor.

44. The power tool of claim 43 wherein the motor braking circuit includes an electronic switch coupled across the windings of the motor that is repeatedly turned on and off by the motor braking circuit to intermittently short the windings of the motor.

45. The power tool of claim 44 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on.

46. The power tool of claim 45 wherein at least one side of the electronic switch is coupled to the windings of the motor through the second switch so that the one side of the electronic switch is coupled to the windings of the motor when the power switch is off and decoupled from the windings of the motor when the power switch is on.

47. A motor control circuit, comprising:

a motor braking circuit;

a power switch for connecting power to a motor and decoupling the motor braking circuit from windings of the motor when the power switch is on and disconnecting power to the motor and coupling the motor braking circuit to the windings of the motor when the power switch is off to power the motor braking circuit with back EMF generated by the motor; and

the motor braking circuit, when powered, intermittently shorting the windings of the motor to brake the motor.

48. The circuit of claim 47 wherein the motor braking circuit includes an braking power switching device coupled across the windings of the motor that is repeatedly turned on and off by the motor braking circuit to intermittently short the windings of the motor.

49. The circuit of claim 48 wherein the motor braking circuit includes a storage capacitor charged by the back EMF generated by the motor that provides power to the motor braking circuit.

50. The circuit of claim 49 wherein the braking power switching device includes an electronic switch and the motor braking circuit includes a timer having an output coupled to an input of the electronic switch, the timer generating a series of pulses that switches the electronic switch on and off.

51. The circuit of claim 50 wherein the electronic switch includes at least one of a triac, a SCR, a FET, an IGBT and a Darlington pair.

52. The circuit of claim 47 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on.

53. The circuit of claim 48 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on, at least one side of the braking power switching device coupled to the windings of the motor through the second switch so that the one side of the braking power switching device is coupled to the windings of the motor when the power switch is off and decoupled from the windings of the motor when the power switch is on.

54. The power tool of claim 53 and further including a diode coupled across the windings of the motor.

55. A motor control circuit, comprising:

a motor braking circuit;

a power switch for connecting power to the motor and decoupling the motor braking circuit from windings of the motor when the power switch is on and disconnecting power to the motor and coupling the motor braking circuit to the windings of the motor when the power switch is off to charge a storage capacitor of the motor braking circuit with back EMF generated by the motor; and

the motor braking circuit, when powered, intermittently shorting the windings of the motor to brake the motor.

56. The circuit of claim 55 wherein the motor braking circuit includes an electronic switch coupled across the windings of the motor that is repeatedly turned on and off by the motor braking circuit to intermittently short the windings of the motor.

57. The power tool of claim 56 wherein the power switch includes first and second switches, the first switch connecting power to the motor when the power switch is on and disconnecting power from the motor when the power switch is off, the second switch coupling the motor braking circuit to the windings of the motor when the power switch is off and decoupling the motor braking circuit from the windings of the motor when the power switch is on.

58. The power tool of claim 57 wherein at least one side of the electronic switch is coupled to the windings of the motor through the second switch so that the one side of the electronic switch is coupled to the windings of the motor when the power switch is off and decoupled from the windings of the motor when the power switch is on.