PHASE DIFFERENCE DETECTOR, PHASE DIFFERENCE DETECTION PROGRAM, AND PLASMA PROCESSING SYSTEM USING THE PHASE DIFFERENCE DETECTOR
First Claim
1. A phase difference detector for detecting a phase difference between a first AC signal and a second AC signal having a same frequency as a fundamental frequency of the first AC signal, the detector comprising:
- a sine wave generator that generates a sine wave signal having the same frequency as the fundamental frequency;
a cosine wave generator that generates a cosine wave signal having the same frequency as the fundamental frequency;
a first signal multiplier that multiplies the first AC signal and the sine wave signal;
a second signal multiplier that multiplies the first AC signal and the cosine wave signal;
a third signal multiplier that multiplies the second AC signal and the sine wave signal;
a fourth signal multiplier that multiplies the second AC signal and the cosine wave signal;
a DC component extraction unit that extracts four DC components by removing an AC component from a result of multiplication in each of the first through the fourth signal multipliers;
a trigonometric function computation unit that obtains a sine value and a cosine value of the phase difference by a computation using the four DC components; and
a phase difference computation unit that uses the cosine value and the sine value computed by the trigonometric function computation unit to compute arctangent of a ratio of the sine value to the cosine value to obtain the phase difference.
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Accused Products
Abstract
A phase difference detector detects the phase difference between two AC signals at a high speed and with high accuracy. A phase difference computation unit computes the phase difference φr(=φ2−φ1) between two detected voltages v1 (phase angle: φ1) and v2 (phase angle: φ2). The phase difference computation unit uses a sine wave vs and a cosine wave vc generated separately and having the same frequency as the fundamental frequency of the voltages v1 and v2, to perform computation of v2s=v2×vs, v2c=v2×vc, v1s=v1×vs, v1c=v1×vc, and then extracts DC components I2=(−A2/2)·sin(φ2), R2=(A2/2)·cos(φ2), I1=(−A1/2)·sin(φ1), R1=(A1/2)·cos(φ1) at low-pass filters. The phase difference computation unit computes R3=R1×R2+I1×I2 at a complex multiplying unit to obtain R3=(A1·A2/4)·cos(φr), computes I3=R2×I1−R1×I2 to obtain I3=(A1·A2/4)·sin(φr), and computes φr=tan−1(I3/R3) at the arctangent calculation unit, thereby obtaining the phase difference φr.
18 Citations
6 Claims
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1. A phase difference detector for detecting a phase difference between a first AC signal and a second AC signal having a same frequency as a fundamental frequency of the first AC signal, the detector comprising:
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a sine wave generator that generates a sine wave signal having the same frequency as the fundamental frequency; a cosine wave generator that generates a cosine wave signal having the same frequency as the fundamental frequency; a first signal multiplier that multiplies the first AC signal and the sine wave signal; a second signal multiplier that multiplies the first AC signal and the cosine wave signal; a third signal multiplier that multiplies the second AC signal and the sine wave signal; a fourth signal multiplier that multiplies the second AC signal and the cosine wave signal; a DC component extraction unit that extracts four DC components by removing an AC component from a result of multiplication in each of the first through the fourth signal multipliers; a trigonometric function computation unit that obtains a sine value and a cosine value of the phase difference by a computation using the four DC components; and a phase difference computation unit that uses the cosine value and the sine value computed by the trigonometric function computation unit to compute arctangent of a ratio of the sine value to the cosine value to obtain the phase difference. - View Dependent Claims (2, 3, 5, 6)
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4. A computer readable storage medium comprising a phase difference detection program encoded and stored in a computer readable format, the program configured to cause a computer to function as a phase difference detector for detecting a phase difference between a first AC signal and a second AC signal having a same frequency as a fundamental frequency of the first AC signal, the program causing the computer to function as:
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a sine wave generator that generates a sine wave signal having the same frequency as the fundamental frequency; a cosine wave generator that generates a cosine wave signal having the same frequency as the fundamental frequency; a first signal multiplier that multiplies the first AC signal and the sine wave signal; a second signal multiplier that multiplies the first AC signal and the cosine wave signal; a third signal multiplier that multiplies the second AC signal and the sine wave signal; a fourth signal multiplier that multiplies the second AC signal and the cosine wave signal; a DC component extraction unit that extracts four DC components by removing an AC component from a result of multiplication in each of the first through the fourth signal multipliers; a trigonometric function computation unit that obtains a sine value and a cosine value of the phase difference by a computation using the four DC components; and a phase difference computation unit that uses the cosine value and the sine value computed by the trigonometric function computation unit to compute arctangent of a ratio of the sine value to the cosine value to obtain the phase difference.
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Specification