| 摘要 |
PURPOSE:To enable a continuous detection of phase with a better flowing property by switching the polarity of a potential difference signal to be inputted into V/F converter between the times of increasing and decreasing a sine wave signal obtained from a counter for counting an output of the V/F converter. CONSTITUTION:An AC input signal eu is inputted into a divider 21 and divided by an amplitude V thereof eu to obtain a cosine wave signal COStheta. On the other hand, an output pulse of a V/F converter 25 is inputted into a counter 26 and a saw tooth digital phase detection signal theta1 is converted into a cosine wave signal COStheta1 with a cosine conversion circuit 27. This cosine signal COStheta1 is inputted into a subtractor 22 through a D/A converter 28 to be subtracted from the cosine wave signal COStheta. Then, a phase difference signal DELTAtheta is inputted into a plurality switching circuit 23 and then, inputted into an integrator 24 with inversion of the polarity while the phase detection signal theta1 ranges from 0- 180 deg. in the electric angle and without inversion thereof when it ranges from 180-360 deg.. Then, the integration output is inputted into the V/F converter 25.
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