Method and device for braking a motor
First Claim
1. A motor braking circuit, comprising a braking power switching device coupled across windings of a motor that is repeatedly cycled open and closed by a sequence of pulses generated by the motor braking circuit to intermittently short the windings to brake the motor, the motor braking circuit adjustable to vary at least one of a duty cycle and frequency of the sequence of pulses, the braking power switching device having a small amount of resistance to reduce peak current flow when the windings are shorted through the braking power switching device.
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Accused Products
Abstract
A method and apparatus for braking a motor has a braking power switching device coupled across windings of the motor. To brake the motor, the braking power switching device is cycled on and off.
956 Citations
53 Claims
- 1. A motor braking circuit, comprising a braking power switching device coupled across windings of a motor that is repeatedly cycled open and closed by a sequence of pulses generated by the motor braking circuit to intermittently short the windings to brake the motor, the motor braking circuit adjustable to vary at least one of a duty cycle and frequency of the sequence of pulses, the braking power switching device having a small amount of resistance to reduce peak current flow when the windings are shorted through the braking power switching device.
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16. A motor braking circuit, comprising:
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a FET coupled across windings of a motor, wherein the FET includes an internal diode coupled across the windings of the motor that acts as a free wheeling diode and is used in lieu of a separate free wheeling diode; a controller coupled to the FET that, upon the motor being switched off, generates a sequence of pulses that switch the FET on and off to brake the motor, the controller adjustable to vary at least one of a duty cycle and a frequency of the sequence of pulses; and a storage capacitor that is charged when power to the motor is switched on and that provides power for the motor braking circuit when power to the motor is switched off. - View Dependent Claims (17, 18, 19, 20)
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- 21. A control circuit for a motor, comprising a switch for activating the motor when the switch is on, a controller, a FET coupled across windings of the motor and coupled to the controller, the FET having an internal diode coupled across the windings of the motor, the internal diode of the FET acting as a freewheeling diode and used in lieu of a separate diode, the controller cycling the FET on and off to brake the motor when the switch is switched off.
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34. A power tool, comprising:
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a housing surrounding a motor; a switch for activating the motor when the switch is on; a controller; and a braking switching device coupled across windings of the motor and coupled to the controller, the controller cycling the braking switching device open and closed with a sequence of pulses to intermittently short the windings to brake the motor when the switch is switched off, the controller adjustable to vary at least one of a duty cycle and a frequency of the sequence of pulses, the braking switching device having a small amount of resistance to reduce peak current flow when the windings are shorted through the braking switching device. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41)
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- 42. A method of braking a motor, comprising cycling a braking switching device coupled across windings of the motor open and closed to intermittently short the windings to brake the motor by pulsing the braking switching device with a pulsating signal and adjusting at least one of a duty cycle and frequency of the pulsating signal, the braking switching device having a small amount of resistance to reduce peak current flow when the windings are shorted through the braking switching device.
- 45. In a cordless power tool having a permanent magnet DC motor, a switch that activates the motor when switched on and deactivates the motor when switched off, a method of braking the motor, comprising switching a semiconductor switch coupled across the windings of the motor on and off to intermittently short the windings to brake the motor by pulsing the semiconductor switch with a pulsating signal and adjusting at least one of a duty cycle and frequency of the pulsating signal, the semiconductor switch having a small amount of resistance to reduce peak current flow when the windings are shorted through the semiconductor switch.
- 48. In a power tool having a mains powered motor, a switch that activates the motor when switched on and deactivates the motor when switched off, a method of braking the motor, comprising switching a semiconductor switch coupled across the windings of the motor on and off to intermittently short the windings to brake the motor by pulsing the semiconductor switch with a pulsating signal and adjusting at least one of a duty cycle and frequency of the pulsating signal, the semiconductor switch having a small amount of resistance to reduce peak current flow when the windings are shorted through the semiconductor switch.
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51. A power tool, comprising:
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a housing surrounding a motor; a switch for activating the motor when the switch is on; a controller; and a FET coupled across windings of the motor and coupled to the controller, the controller cycling the FET open and closed to brake the motor when the switch is switched off, the FET having an internal diode coupled across the windings of the motor, the internal diode of the FET acting as a freewheeling diode and used in lieu of a separate freewheeling diode.
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52. A power tool, comprising:
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a housing surrounding a motor; a switch for activating the motor when the switch is on; a controller; and a FET coupled across windings of the motor and coupled to the controller, the controller cycling the FET open and closed to intermittently short the windings to brake the motor when the switch is switched off, the FET having an internal diode coupled across the windings of the motor, the internal diode of the FET acting as a freewheeling diode and used in lieu of a separate freewheeling diode, the FET having a small amount of resistance to reduce peak current flow when the windings are shorted through the FET. - View Dependent Claims (53)
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Specification