| 摘要 |
A digital filter for removing a PWM noise from a sampling data includes: an averaging filter. The sampling data is obtained by sampling a control amount of a control object, which is driven at a driving frequency in a PWM control manner, at a sampling frequency. The PWM noise includes fundamental and harmonic wave components. The averaging filter calculates an average of the sampling data, which is sampled most recent predetermined sampling times providing an averaging number. The sampling frequency and the averaging number are determined to satisfy a relationship that an absolute value of a difference between the sampling frequency multiplied by a predetermined first integer and the harmonic wave frequency is equal to the sampling frequency divided by the averaging number and multiplied by a predetermined second integer in a frequency range between zero and a Nyquist frequency when the fundamental and harmonic wave components are removed. |
