Motor controller and electric power tool having the same
US8264189B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 22, 2008 |
| Grant date | Sep 11, 2012 |
| Priority date | — |
| Expiry date | May 31, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02K7/14
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A motor controller is provided with a first PWM circuit that repeatedly outputs an on-signal at a first carrier frequency, a second PWM circuit that repeatedly outputs an on-signal at a second carrier frequency that is lower than the first carrier frequency, an AND circuit that receives both the on-signal outputted from the first PWM circuit and the on-signal outputted from the second PWM circuit and outputs a third on-signal which is a logical product of the received on-signals, and a voltage apply circuit that applies a voltage to the motor intermittently in synchronization with the third on-signal outputted from the AND circuit. At least one of the first carrier frequency and the second carrier frequency is equal to or lower than 1 kHz or equal to or higher than 3 kHz. As a result, generation of an unpleasant noise by a motor controller using two PWM circuits may be suppressed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.