Electronic apparatus
An electronic apparatus includes: a processor; a first electronic circuit that outputs a pulse width modulation signal; a low-pass filter circuit that outputs a voltage based on the pulse width modulation signal; a second electronic circuit that outputs an analog signal by using the output voltage of the low-pass filter circuit; and a third electronic circuit that converts the analog signal into a digital signal, and the processor sets a frequency of the pulse width modulation signal to a frequency at which a noise component included in the digital signal is reduced in relation to a sampling frequency of the third electronic circuit.
1 . An electronic apparatus comprising:
a processor;
a first electronic circuit is configured to output a pulse width modulation signal having a frequency;
a low-pass filter circuit is configured to output a voltage based on the pulse width modulation signal;
a second electronic circuit is configured to output an analog signal by using the output voltage of the low-pass filter circuit; and
a third electronic circuit is configured to convert the analog signal into a digital signal,
wherein a harmonic noise which is a noise component having the same frequency as the frequency of the pulse width modulation signal is generated by the first electronic circuit and is superimposed on the third electronic circuit and is converted into an aliasing noise in the digital signal, and
the processor is configured to set the frequency of the pulse width modulation signal to a frequency, wherein the aliasing noise at the frequency included in the digital signal does not appear in a frequency band equal to or less than ¼ of a sampling frequency of the third electronic circuit,
wherein the first electronic circuit is configured to output n pulse width modulation signals,
n is an integer of 2 or more, and
the processor is configured to perform control of setting frequencies of the n pulse width modulation signals to a same frequency and shifting phases of the n pulse width modulation signals by 360/n degrees respectively.
2 . The electronic apparatus according to claim 1 ,
wherein the noise component is generated at a frequency corresponding to the frequency of the pulse width modulation signal and the sampling frequency,
in a case in which the frequency of the pulse width modulation signal is denoted by Fn and the sampling frequency is denoted by Fs, the processor is configured to set the frequency of the pulse width modulation signal to satisfy NFs+Fs/4≤Fn≤(N+1)Fs−Fs/4, and
N is an integer of 0 or more.
3 . The electronic apparatus according to claim 2 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
4 . The electronic apparatus according to claim 1 ,
wherein the noise component is generated at a frequency corresponding to the frequency of the pulse width modulation signal and the sampling frequency,
in a case in which the frequency of the pulse width modulation signal is denoted by Fn and the sampling frequency is denoted by Fs, the processor is configured to set the frequency of the pulse width modulation signal to satisfy Fn=NFs−Fs/4 or Fn=NFs+Fs/4, and
N is an integer of 1 or more.
5 . The electronic apparatus according to claim 4 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
6 . The electronic apparatus according to claim 1 ,
wherein the n pulse width modulation signals include a plurality of pulse width modulation signal groups divided according to a duty ratio, and
the processor is configured to perform control of shifting the phase of the pulse width modulation signal included in the pulse width modulation signal group for each of the pulse width modulation signal groups.
7 . The electronic apparatus according to claim 6 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
8 . The electronic apparatus according to claim 1 ,
wherein a ground of the low-pass filter circuit and a ground of the third electronic circuit are electrically connected to each other.
9 . The electronic apparatus according to claim 8 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
10 . The electronic apparatus according to claim 1 ,
wherein the second electronic circuit includes a sensor having at least a function of detecting a position of an object, and
the analog signal is a signal indicating a detection result of the sensor.
11 . The electronic apparatus according to claim 10 ,
wherein the second electronic circuit includes a constant current circuit that is configured to supply a constant current to the sensor by using the output voltage of the low-pass filter circuit.
12 . The electronic apparatus according to claim 11 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
13 . The electronic apparatus according to claim 10 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
14 . The electronic apparatus according to claim 1 ,
wherein the second electronic circuit includes an amplification circuit that is configured to amplify a signal indicating a detection result of a sensor having at least a function of detecting a position of an object by using the output voltage of the low-pass filter circuit, and
the analog signal is a signal amplified by the amplification circuit.
15 . The electronic apparatus according to claim 14 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.
16 . The electronic apparatus according to claim 1 ,
wherein the analog signal is a signal having a frequency equal to or less than ¼ of the sampling frequency as a usage band.