Snubber circuit for a hand held power tool

Patent metadata

Field	Value
Publication number	US-9400517-B2
Application number	US-201314078892-A
Country	US
Kind code	B2
Filing date	Nov 13, 2013
Priority date	Nov 13, 2012
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A hand held power tool including a trigger, a motor, an output unit driven by the motor, a switch bridge, and a snubber circuit. The switch bridge is operable to selectively provide power to the motor to drive the output unit in response to activation of the trigger. The snubber circuit is electrically connected in parallel across the switch bridge. The snubber circuit is operable to store energy when power is being provided to the motor, and release the energy when power is not being provided to the motor.

First claim

What is claimed is:

1. A hand held power tool comprising:
a trigger;
a motor;
an output unit driven by the motor;
a switch bridge operable to selectively provide power to the motor to drive the output unit in response to activation of the trigger; and
a snubber circuit electrically connected in parallel across the switch bridge, the snubber circuit operable to store energy when power is being provided to the motor and release the energy when power is not being provided to the motor.

2. The hand held power tool of claim 1 , wherein the energy is released from the snubber circuit into one of the switch bridge and the motor.

3. The hand held power tool of claim 1 , wherein the motor is a brushless direct-current motor.

4. The hand held power tool of claim 1 , wherein the snubber circuit includes a capacitor operable to store energy.

5. The hand held power tool of claim 4 , wherein the snubber circuit further includes a switch, the switch configured to release the energy stored in the capacitor upon activation of the switch.

6. The hand held power tool of claim 5 , further comprising a controller, and wherein the switch is controlled by the controller.

7. The hand held power tool of claim 5 , wherein
a positive terminal of the switch bridge is electrically connected to a first terminal of the switch,
a second terminal of the switch is electrically connected to a positive terminal of the capacitor, and
a negative terminal of the capacitor is electrically connected to a negative terminal of the switch bridge.

8. The hand held power tool of claim 1 , further comprising a battery receptacle operable to receive a battery pack.

9. The hand held power tool of claim 8 , wherein the battery pack receives the energy released from the snubber circuit.

10. The hand held power tool of claim 1 , wherein the snubber circuit includes a capacitor, a diode, a resistor, and a Zener diode.

11. The hand held power tool of claim 10 , wherein
a positive terminal of the switch bridge is electrically connected to an anode of the diode,
a cathode of the diode is electrically connected to a positive terminal of the capacitor and a positive terminal of the resistor,
a negative terminal of the resistor is electrically connected to a cathode of the Zener diode, and
an anode of the Zener diode is electrically connected to a negative terminal of the capacitor and a negative terminal of the switch bridge.

12. A hand held power tool comprising:
a motor;
an output unit driven by the motor;
a switch bridge operable to selectively provide power to the motor; and
a snubber circuit electrically connected to the switch bridge in a parallel-type configuration, the snubber circuit including a capacitor configured to store magnetic-field energy when power is being provided to the motor and release the magnetic-field energy when power is not being provided to the motor.

13. The hand held power tool of claim 12 , wherein the energy is released from the snubber circuit into one of the switch bridge and the motor.

14. The hand held power tool of claim 12 , further comprising
a user-activated switch; and
a controller electrically connected to the user-activated switch, the controller configured to control the switch bridge upon activation of the user-activated switch.

15. The hand held power tool of claim 14 , further comprising a switch electrically connected in series with the capacitor.

16. The hand held power tool of claim 15 , wherein
the switch is configured to release the magnetic-field energy stored in the capacitor upon activation of the switch, and
wherein the controller is further configured to activate the switch.

17. The hand held power tool of claim 16 , wherein
a positive terminal of the switch bridge is electrically connected to a first terminal of the switch,
a second terminal of the switch is electrically connected to a positive terminal of the capacitor, and
a negative terminal of the capacitor is electrically connected to a negative terminal of the switch bridge.

18. The hand held power tool of claim 12 , wherein the snubber circuit further includes a diode electrically connected in series with the capacitor.

19. The hand held power tool of claim 12 , further comprising a battery receptacle configured to receive a battery pack.

20. The hand held power tool of claim 19 , wherein the battery pack receives the energy released from the snubber circuit.

21. The hand held power tool of claim 12 , wherein the snubber circuit further includes a diode, a resistor, and a Zener diode.

22. The hand held power tool of claim 21 , wherein
a positive terminal of the switch bridge is electrically connected to an anode of the diode,
a cathode of the diode is electrically connected to a positive terminal of the capacitor and a positive terminal of the resistor,
a negative terminal of the resistor is electrically connected to a cathode of the Zener diode, and
an anode of the Zener diode is electrically connected to a negative terminal of the capacitor and a negative terminal of the switch bridge.

23. A method for controlling unclamped inductance in a power tool including a motor, an output unit driven by the motor, a switch bridge, and a snubber circuit, the method comprising:
receiving power at the switch bridge;
selectively providing power to the motor;
storing energy in the snubber circuit when power is being provided to the motor; and
releasing the energy stored in the scrubber circuit when power is not being provided to the motor.

24. The method of claim 23 wherein the energy is a magnetic-field energy.

25. The method of claim 23 wherein the energy is released from the snubber circuit into one of the switch bridge and the motor.

Assignees

• Milwaukee Electric Tool Corp

Inventors

• Mergener Matthew J
• Wycklendt Matthew P

Classifications

• H02P6/085

  in a bridge configuration · CPC title

• G05F3/10 Primary

  using uncontrolled devices with non-linear characteristics · CPC title

• H02M1/34

  Snubber circuits · CPC title

• H02J7/32

  for charging batteries from a charging set comprising a non-electric prime mover {rotating at constant speed} · CPC title

• B25D17/00

  Details of, or accessories for, portable power-driven percussive tools {(details or components, e.g. casings, bodies, of portable power-driven tools not particularly related to the operation performed B25F5/00)} · CPC title