US2013158920A1PendingUtilityA1
Pulse width modulated voltage measuring circuit and method
Est. expiryDec 19, 2031(~5.4 yrs left)· nominal 20-yr term from priority
H02J 7/865G01B 7/14G01R 19/003G01R 19/02G01R 19/16576G01R 19/04G01R 19/16528H02H 3/06G01B 7/003G01D 5/2457H02H 3/087F16H 59/105G01R 19/00G01R 23/02G06F 17/00
48
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Claims
Abstract
A voltage measuring circuit includes a rectifier to receive an alternating current (AC) voltage to be measured and to provide a rectified output; a comparator for comparing the rectified output and producing therefrom a square wave having a pulse width indicative of the rectified output exceeding a threshold; a calculation circuit for converting a measurement of the pulse width into a measurement of the voltage and optionally an opto-isolator interconnecting the comparator to the calculation circuit. The rectifier may provide operating power to the comparator and an input side of the opto-isolator, from the AC voltage signal being measured. The remainder of the measuring circuit may powered by a source isolated from the voltage to be measured.
Claims
exact text as granted — not AI-modifiedWhat is claimed is:
1 . A voltage measuring circuit, comprising:
a rectifier to receive an alternating current (AC) voltage to be measured and to provide a rectified output; a comparator for comparing said rectified output and producing therefrom a square wave having a pulse width indicative of said rectified output exceeding a threshold; a calculation circuit for converting a measurement of said pulse width into a measurement of said voltage.
2 . The circuit of claim 1 , further comprising an opto-isolator interconnecting said comparator to said calculation circuit.
3 . The circuit of claim 1 , wherein said calculation circuit comprises an integrator.
4 . The circuit of claim 1 , wherein said calculation circuit comprises a processor for sampling said square wave to determine at least one of said pulse width, and frequency of said square wave.
5 . The circuit of claim 4 , wherein said processor is operable to calculate a frequency of said AC voltage from at least one of said pulse width and said frequency of said square wave.
6 . The circuit of claim 4 , wherein u is the time said square wave is high, and w is the time said square wave is low in a period, and wherein said processor calculates said frequency as
1
2
·
(
u
+
w
)
.
7 . The circuit of claim 4 , wherein said threshold equals K·V i and wherein u is the time said square wave is high, and w is the time said square wave is low in a period, and wherein said processor calculates said measurement of said voltage as
K
·
V
i
sin
(
π
·
u
2
·
(
u
+
w
)
)
.
8 . The circuit of claim 4 , wherein said threshold equals KV i and wherein u is the time said square wave is high, and w is the time said square wave is low in a period, and wherein said processor calculates said measurement of said voltage as
K
·
V
i
2
·
sin
(
π
·
u
2
·
(
u
+
w
)
)
.
9 . The circuit of claim 4 , wherein said threshold equals KV i and wherein u[i] is the time said square wave is low, and w[i] is the time said square wave is high in a period, and wherein said processor calculates said measurement of said voltage as
∑
i
=
1
n
K
·
V
i
2
·
n
·
sin
(
π
·
u
[
i
]
2
·
(
u
[
i
]
+
w
[
i
]
)
)
.
10 . The circuit of claim 9 , wherein K and n are chosen so that the ratio K/√2·n) approximates an integer.
11 . The circuit of claim 1 , wherein said processor signals a fault when no square wave is output by said comparator.
12 . The circuit of claim 2 , wherein said rectifier provides operating power to said comparator and an input side of said opto-isolator, from said AC voltage being measured.
13 . A method of measuring the magnitude of an AC voltage signal, said method comprising:
rectifying said AC voltage signal to provide a rectified output; comparing said rectified output and producing therefrom a square wave having a pulse width indicative of said rectified output exceeding a threshold; converting a measurement of said pulse width into a measurement of said magnitude of said AC voltage signal.
14 . The method of claim 13 , wherein said converting comprises integrating said square wave.
15 . The method of claim 13 , wherein said converting comprises sampling said square wave to determine a time that said square wave is on and a time that said square wave is off.
16 . The method of claim 15 , wherein said threshold equals K·V i and wherein u is the time said square wave is high, and w is the time said square wave is low in a period, and wherein said measurement said voltage is calculated as
K
·
V
i
sin
(
π
·
u
2
·
(
u
+
w
)
)
.
17 . The method of claim 16 , wherein said threshold equals K·V i and wherein u is the time said square wave is high, and w is the time said square wave is low in a period, and wherein said voltage is calculated as
K
·
V
i
2
·
sin
(
π
u
2
·
(
u
+
w
)
)
.
18 . The method of claim 15 , wherein said threshold equals K·V i and wherein u[i] is the time said square wave is low, and w[i] is the time said square wave is high in a period of said AC voltage, and wherein said measurement of said voltage is calculated over n periods as
∑
i
=
1
n
K
·
V
i
2
·
n
·
sin
(
π
·
u
[
i
]
2
·
(
u
[
i
]
+
w
[
i
]
)
)
.
19 . The method of claim 18 , wherein K and n are chosen so that K/(√2·n) approximates an integer.Cited by (0)
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