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Kafe 바로가기국가/구분 | United States(US) Patent 등록 |
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국제특허분류(IPC7판) |
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출원번호 | US-0782400 (2004-02-18) |
발명자 / 주소 |
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 | 피인용 횟수 : 419 인용 특허 : 11 |
Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply preferably includes a battery, such a lithium ion or nic
Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply preferably includes a battery, such a lithium ion or nickel cadmium.
What is claimed is: 1. A method for extending the life of a power supply that supplies power to a motor in a power tool, comprising: supplying voltage pulses of an initial width to the motor using pulse width modulation; comparing a motor current generated due to the supplied voltage pulses to at l
What is claimed is: 1. A method for extending the life of a power supply that supplies power to a motor in a power tool, comprising: supplying voltage pulses of an initial width to the motor using pulse width modulation; comparing a motor current generated due to the supplied voltage pulses to at least one of three different thresholds; and changing the pulse width from the initial width to one of zero, a first alternative pulse width and a second alternative pulse width based on the comparison to a given threshold. 2. The method of claim 1, wherein the alternative width is shortened. 3. The method of claim 1, wherein the alternative width is lengthened. 4. A power tool, comprising: a housing; a power supply disposed within the housing and including a plurality of lithium ion batteries; a motor disposed within the housing and providing torque to the power tool; and a pulse width modulation controller within the housing for varying the pulse width of voltage pulses supplied to the motor based on a comparison of the motor current to one of at least three different thresholds. 5. The power tool of claim 4, wherein the lithium ion batteries are rechargeable. 6. The power tool of claim 4, wherein the pulse modulation controller includes a switch that supplies current to the motor when the switch is turned on. 7. The power tool of claim 6, wherein the pulse modulation controller further includes a microprocessor that turns the switch on and off. 8. The power tool of claim 7, wherein the pulse modulation controller further includes voltage measuring circuitry to determine a turn on time for the switch. 9. The power tool of claim 8, wherein the voltage measuring circuitry measures battery voltage and motor voltage. 10. The power tool of claim 9, wherein power tool further includes circuitry for speed control. 11. The power tool of claim 10, wherein the circuitry for speed control includes a potentiometer. 12. The power tool of claim 11, wherein the voltage measuring circuitry further measures a voltage across the potentiometer. 13. The power tool of claim 6, wherein the pulse width modulation circuit further includes a ramp generator that provides a ramp signal. 14. The power tool of claim 13, wherein the pulse width modulation circuit further includes a comparator that compares the ramp signal to a measured motor voltage to determine the pulse width modulation waveform. 15. An apparatus for limiting current to a load, comprising: means for supplying power; means for providing torque to a load; means for switchably supplying power to the means for providing torque from the means for supplying power, the means for switchably supplying power being actuated according to a pulse width modulation technique; and means for controlling the means for switchably supplying power based on a comparison of current generated in the apparatus to one of at least three different thresholds. 16. The apparatus of claim 15, wherein the means for supplying power includes lithium ion batteries. 17. The apparatus of claim 16, wherein the means for supplying power provides a direct voltage between 30 and 40 volts.
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