Note: Descriptions are shown in the official language in which they were submitted.
CA 02207795 2002-06-28
Description
Method and Device for Supplying an Electric Consumer with a
Regulated Electric Voltage or_ Current
The invention concerns a method and an arrangement for
~~upplying an electric consumer with an electric power supply
voltage or current.
Electric consumers are generally supplied with an electric
power supply voltage or current from a power supply source
over electric lines. Potential differences between the
consumer and source can cause a problem with such a power
supply over electric lines.
There are known potential-free (electrically isolated) power
supply systems for electric sensors operating as electric
consumers, where the power for the sensor is transmitted
optically. In a known embodiment, the :Light of: a laser diode
is transmitted over an optical fiber to a photoelement array
which converts the light to electric power fox- the sensor.
The measurement data from the sensor are also transmitted
optically over an optical fiber "Optical Power Supply for
Fiber-optic Hybrid Sensors", W. Gross, 1991, Sensors and
Actuators A, Vol. 25-27 (1991), pages 475-480.
One problem with such optical power transmission systems is
fluctuations in intensity of the light source, due in
particular to aging phenomena or changes in ambient
temperature. Such fluctuations in intensity of the light
source can be compensated by a constant-current regulator
for the light source or by using a monitor photodiode or a
monitor photoelement to measure the
1
06i12i97 17:05 KENYOtJ 8~ KEt~IYON ~ 613232840 N0.1~6 P003i029
optical power emitted by the light source and adjusting the
power supply current for the light source. Effects of
disturbances on the transmission link between light .so~ro~e and
photoelectric converter and changes in con~rersion efficiency of
the photoelectric converter cannot be compensated with these
known types of control.
Therefore, the object ox this invention is to provide a method
and an arrangement fat' supplying an electric consumer 'with an
electric power supply voltage or current without the
disadvantages described above.
This object is achieved according to this invention with the
features of Claim 1 and Claim 6. The powar needed by at least
one consumer is transmitted in the foam of eiectro:teagnetic
radiation by at least one transmitter tc~ at least one rece~.ver.
The receiver is electrically connected to the consumer and
converts the electroc~agnetic radiation received froze the
transmitter to an electric power supply voltage or current fQr
the consumer. To equalize fluctuations in intensity in the
electromagnetic radiation or changes in conversion efficiency of
the transmitter or receiver, the power supply voltage or current
is regulated at a predefined,reference value by regulating the
transmitting power of the tran$mitter. Regu~.atinc~ the power
supply voltage or cuxxrent as a controlled variable means that
the power supply voltage or current is measured, the measured
prevailing value (actual va.7.ue) of the power supply voltage or
current is compared with the predefined reference value
(setpoint), and the transmitting power of the transmitter :~s
adjusted (regulated, Controlled) so that the control difference
(control deviation) between the measured power supply voltage at
2
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the measured power supply current and the reference value
comes to lie within a predefined tolerance interval that at
least includes the zero point. This control makes it
possible to equalize unwanted changes in power supply
voltage or current due to interfering factors such as
temperature, aging of the transmitter and receiver or
attenuation in the transmission link between the transmitter
and receiver. Therefore, in particular, the power
consumption by the transmitter can be reduced and the
lifetime of the transmitter can be increased because the
transmitting power emitted by the transmitter can be adapted
to the actual demand by the consumer, and excess power need
not be supplied to compensate for interference.
This object is also achieved with the features
characterized in claim 21.
Advantageous embodiments of and refinements on the
method and arrangement according to this invention are
derived from the dependent claims.
In accordance with one aspect of this invention,
there is provided a method of supplying an electric
consumer (2) with an electric power supply voltage (U) or an
electric power supply current, wherein a) electromagnetic
radiation (R) of a transmitter (3) and of a wavelength range
between approximately 400 nm and approximately 1400 nm or in
form of radio waves is transmitted to a receiver (4)
comprising a photoelectric converter or a radio receiver and
is converted by the photoelectric converter or the radio
receiver to the electric power supply voltage (U) or the
electric power supply current for the consumer (2), b) the
power supply voltage (U) or the electric power supply
- 3 -
CA 02207795 2003-04-02
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current is regulated by controlling the transmitting power
of the transmitter (3) at a predefined reference
value (REF), c) the transmitting power of the
transmitter (3) is adjusted according to a control
difference between the power. supply voltage (U) or the
electric power supply current and the reference value (REF).
In accordance with another aspect of this
invention, there is provided an arrangement of supplying an
electric consumer (2) with an electric power supply
voltage (U) or an electric power supply current, having a) a
transmitter (3) for transmitting electromagnetic
radiation (R) of a wavelength range between approximately
400 nm and approximately 1400 nm or in form of radio waves,
b) a receiver (4) for converting the electromagnetic
radiation (R) received from the transmitter (3) to the
electric power supply voltage (U) or the electric power
supply current for the consumer (2) by the means of a
photoelectric converter or a radio receiver,
c) a regulator (6) that regulates the power supply
voltage (U) or the electric power supply current by
controlling the transmitting power of the transmitter (3) at
a predefined reference value (REF), d) a power
controller (7) that adjusts the transmitting power of the
transmitter (3) according to a control difference between
the power supply voltage (U) or the electric power supply
current and the reference value (REF).
In accordance with a further aspect of this
invention, there is provided an arrangement for supplying an
electric consumer (2) with an electric power supply voltage
(US), having a) a transmitter (3) for transmitting
electromagnetic radiation (R), b) a receiver (4) for
converting the electromagnetic radiation (R) received from
- 3a -
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the transmitter (3) to the electric power supply voltage (US)
for the consumer (2), and c) a regulator (6) that measures
the power supply voltage (US) and compares the measured value
with a predefined reference value (URef) and generates a
control signal (S) for controlling the transmitting power of
the transmitter (3) in accordance with [the result of] this
comparison, wherein the regulator (6) contains a voltage
divider (11), a comparing element (12) and a PWM
modulator (14), wherein the input of the voltage divider (11)
is connected to the output of the receiver (4) and its output
is connected to the negative input of the comparing
element (12) whose positive input is connected to the output
of the reference value generator (61) and whose output is
connected to the input of the PWM modulator (14), and the
output of the PWM modulator (14) is connected to [one input
of] a digital mixing device (15) whose other input is
connected to the consumer and whose output delivers a mixed
signal (SpWMD) .
The method and arrangement are essentially suitable
for supplying any electric consumer but they are especially
suitable for supplying electronic circuits and electric
sensors or actuators.
The electromagnetic radiation for transmitting the
power for the consumer can be selected from each wavelength
range for which there are suitable transmitters for
transmitting the electromagnetic radiation and receivers for
converting this radiation to electric power. In a first
advantageous embodiment, visible light or infrared light from
a wavelength range between
-~ 3 b -
~6~12~97 17:05 KE~~I'~'ON ~ KEhJ'r'Ohd -~ 6132328440 hJ0.146 P005/029
about 400 nrn and about 140 nm is used, Then lasers laser
diodes, beds or other light sources rnay be used as the
transmitter. Suitable receivers include, for example
photoelectric converters such as phatodiades, photaelements and
preferably array's of photoelements. The light can be transmittea
from the transmitter to the receiver over optical. fibers or as a
free beam. In a second embodiment, radio waves from the radio
frequency or microwave spectrum tradio or directional radio) and
corresponding radio transmitters and radio receivers are used to
transmit and receive these radio waves.
In another advantageous embodiment of this control system,
successive short control pulses are generated as long as the
control difference between the measured power supply voltage or
the measured power supply current and the reference value xs
less than zero and is thus too small. Then the transmitting
power of the transmitter is increased by a power controller via
a control current as a function of the integral over time of the
control pulses within a predefined time window in order to '
increase the power supply voltage or power supply current that
has dropped too much.
To generate the control pulses, first a binary comparator signal
containing information about the [plus or minus sign of the
control difference is preferably generated by a comparator
circuit. The cornparator signal assumes its first logic state
when the control difference between the measured value of the
power supply voltage or current and the reference value supplied
by a reference value generator is less than zero, arad it assumes
its second logic state when the control difference is greater
than or equal to zero. This binary camparator signal is sent to
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means for generating the control pulses; these means generate
electric Gantrol pulses when the comparator s~.gnal is in its
first logic state. In one embodiment, these meanv for generating
the control pulses include an astable multivibrator whose input
receives the comparator signal and wh4se output delivers a train
of control pulses as long as the comparator signal is in its
first logic state. In another embodiment the means for
generating the control pulses include means for modulating the
radiation of the transmitter with regular pulses, a. filter unit
connected electrically to the receiver to filter oat these
pulses, and a logic circuit such as an ANB gate whose first
input receives the comparator signal and whose second input
receives pulses from the filter unit. The logic cirGUit switches
the pulses as control pulses to its output when the comparator
signal is in its fixst logic state.
Because of the electrical isolation, the electx~.c control pulses
are preferably transmitted as light signals or radio signals
from a signal transmitter to a signal recei~rer and then
converted back to electric pulses. The amplitude and duration of
these electric pulses are preferably normalized, e.g., with the
help of a manostable multivibre~tnx, and then sent to an
integrator that ~.ntegrates the pulses over time. 'Ihe output
current of the integrator, which corresponds to the ~.ntegral of
the pulses aver time within a time window defined by the time
constant of the integrator. is provided as a variable control
current far regulating the transmitting power of t~~e
transmitter.
In an especially advantageous ernbadiment of the control system,
a pulse width-modulated signal (PWM signal) is used to transmit
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the control difference between the power supply voltage or power
supply current and the reference value. The value of the control
difference is then coded in the ~raxxabl.e pulse width of the PWM
signal. The transmitting power of the transmitter is regulated
with this PWM signal. 1n this embodiment, r_he regulator also
contains a PWM modulator for Gpnverti.ng the control difference
into a PWM signal in addition to containing a reference value
generator for supplying the reference value and a eumparing
element for determining the control difference.
By using a PWM modulator that receives the control diffexeloce
determined between the measured power supply voltage or measured
power supply current and the predefined reference value, the
control difference thus determined is converted to a PWM signal
in the regulator and transmitted to the transmitter, preferably
as an isolated signal. Gne bit is sufficient for this
transmission. Good stability properties of the control circuit
are achieved due to the transmission of the PWM signal thus
generated, and limit cycles are prevented from occurring from
the beginning. Since a t5.mewcoded analog signal is transmitted
by means of the PWMf signal, a PI controller can be used to as an
output regulator fox the transmitter. This yields an especially
advantageous linear control of the power suppJ.y voltage of the
consumer.
In an advantageous embodiment, the PWM modulator- is composed of
a modulation generator, a comparing element, and a comparator.
The positive input of the comparing element forms the input of
the PWM modulator. The negative input of the comparing element
is connected to the output of the modulation generator, The
comparator is connected downstream from the comparing element.
s
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The output of the comparator forms the output of the PWM
modulator. The modulation. generator may be in particular a delta
generator, a saw-tooth voltage generator or a generator whose
modulation Signal is asymmetrical and delta~like and comprises
exponential functions.
In an especially advantageous embodiment of the regulator. the
PWM modulator is designed to convert the control difference to a
PWM signal only in a range around the reference value. This
yields a higher resolution, so a better control quality is
achieved.
In another advantageous embodiment of this arrangement, the
output of the receiver is buffered. The reliability and
stability of the load is increased by this buffering of the
receiver.
To further illustrate this invention, reference is made to the
figures. which schematically show:
Figure 1: a schematic diagram of an arrangement for supplying an
electric consumer with an electric power supply
voltage,
Figures 2 and 3 each show one embodiment of a regulator
for such an arrangement,
Figure 4: one embodiment of a power controller for such an
arrangement,
Figure 5: one embodiment of an arrangement with PWM control
signals, and
Figure 6: one embodiment of a P~1M modulator,
each figure in the form of schematic diagrams. Corresponding
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parts are labeled with the same notation.
Figure 1 shows an electric consumer 2, a transmitter 3 for
transmitting electromagnetic radiation R, a receiver ~ far
receiving radiation R, two electric term~.nals 4A arid ~B of the
receiver, a regulator 6 and a power controller 7.
Receiver 4 converts electromagnetic radiation R received by
transmitter 3 to an electric power supply voltage US car an
electric power supply current foz~ consumer 2. This po~.~er supply
voltage U$ is available across the two terminals 4A and ~~ of
receiver 9 between which consumer 2 is canneated.
The transmitting power of transmitter 3, i.e., the power of the
electromafnetic radiation R output, can be controlled by power
controller 7. For this purpose, power controller ~ supplies
transmitter 3 with aE~ electric control currert T or~ ~ahich the
transmitting power of transmitter 3 depends.
Regulator ~ measures power supply voltage U far consumer 2.
Power supply voltage t~ is preferably measured directly at
consumer 2 by a four~pole measurement, as illustrated here, to
prevent a voltage drop in the feeder lines from recez~rer 4 tc~
consumer 2 in the measurement. Howe~rer, power supply voltage U
can also be picked off at any two points in the power supply
circu?t between which consumer 2 is connected. rn particular,
the maximum power supply voltage Us available across the two
terminals 4A and 48 of receiver 4 ran also be measured.
Regulator 6 compares the measured value (actual value) of power
supply voltage U with a predefined reference value (setpaintl
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RE F. If the actual value of power supply voltage U differs too
greatly from its setpoint REF, xegulatvr 6 instructs power
controller 7 via control signal S to adjust the transmitting
power of transmitter 3 as a function of control difference ~U =
U - REF between actual value U and setpoint REF. If control
difference GU = U - REF is below a predefined non-positive
tolerance value x1 s 0, i.e., if the prevailing power supply
voltage U is too law, power controller 7 increases the
transmitting power of transmitter 3 via control current
However, if control difference bU = GT - REF exceeds a predefined
nor.-negative tolerance value x~ a 0, i.e., i~ the measured power
supply voltage U is too high, power controller 7 preferabiy
reduces the transmitting powez of transmitter 3. It control
difference ~U = U - REF is within the predefined tolerance
interval ;x1, x2) between the ~wo tolerance values x1 and x2,
power controller 7 keeps control current ~ constant and thus
also keeps the transmitting power of transmitter 3 constant.
This arrangement thus yields a control circuit whose controlled
variable is the power supply voltage U and whose controlled
system consists of transmitter 3, receiver 4 and the
transmission link between transmitter 3 and receiver 4. All
influencing quantities that affect this contzalled system, such
as changes in attenuation of the transmission link for
electromagnetic radiation R or changes in efficiency of
transmitter 3 and/or receiver 4 due to aging or ohanges in
temperature, for example, can be compensated by regulating the
power supply voltage U for consumer 2. The manipulated variable
of the control circuit is control current T of power controller
7 or control signal S of regulator &,
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Regulator 6 may be impwemented in various designs and, to
control the transmitting power of transmitter 3, it may be
operatively connected to transmitter 3 over various controlled
systems.
Figure 2 illustrates a first embodiment of regulator 6.
Regulator 6 contains a reference value generator 61 and a
comparator circuit with two resistors 62 and 63 and an
operational amplifier 64 in addition to an astable multivibrator
55. Reference value generator 61 is electrically connected to
receiver 4 and generates a predefined reference voltage, which
is negative in the embodiment illustrated here, as reference
value REF which is available at output 61A of reference value
generator ~1. This output 61A of reference value generator 61 is
electrically connected to a first input 64A of operational
amplifier 54 via the first resistor 62. This first input 69A of
operational amplifier 64 is electrically connected to the second
terminal 9B of receiver 4 via the second resistor 53. The other
input ~4B of operational amplifier 64 is electrically connected
to the other terminal 4A of receiver 4. In the embodiment
illustrated here the second terminal 9B of receiver 9 is at a
positive potential with respect to a constant potential, e.g.,
zero potential (ground), at the first terminal 9A. With a
suitable choice of resistors 6~ and 6~ and operational amplifier
64, a binary comparator signal CS is obtainsd at output 54C of
the operational amplifiers the first logic state of this binary
comparator signal CS corresponds to the case when power supply
voltage U is below its setpoint REF t~U c ~), and its second
logic state corresponds to the Apposite case, namely when power
supply voltage U is greater than or equal to reference value REF
(~U ~ 0). Binary comparator signal CS is sent to astable
CA 02207795 1997-06-13
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multivibrator 65. Astable multivibrator 65 generates electric
pulses P of a predefined duratzon at given intervals when
co:nparator signal CS that is applied to its input is in its
first logic state, i.e., when control difference DU = ~' - RAF is
less than zero.
In the second embodiment of a regulator according to figure 3,
the comparator cixcuit of regulator 6 comprises four resistors
62, 62A, 63 and 63A and again an operational amplifier 64. The
first input 64A of operational amplifier 64 is connected to the
second terminal 4B of receiver 4 via resistor 63 and to the
first terminal 4A of receiver 9 via resistor 63A. The second
input 548 of operational amplifier 64 is electrically connected
to output G1A of reference value generatoz ~1 via xesistor 62
and to the first terminal 4A of receiver 9 via resistor 62A. In
this embodiment, reference value generator 67. supp:~ies a
positive reference voltage as rexerence value REF. Furthermore,
digital pulses, preferably square-wane pulses, are also
transmitted to receiver 9 with electromagnetic radiation R. To
do so, radiation R of transmitter 3 is modulated accordingly.
These pulses are filtered out by a filter unit 67 connected
across the two terminals 4A and 9~ of receiver 9 and sent as
electric pulses P' to one input 668 of a logic circuit 66.
Comparator signal CS of operational amplifier 64 is applied to
another input 66A of logic circuit 66. T~ogic circuit 66 switches
pulses P' through to its output 56 as pulses P only when
compa.rator signal CS is in its first logic state, i.e., when the
measured power supply voltage U is below reference value R.EF.
For example, an AN'D gate may be used as logic ditcuit 66.
In the advantageous embodiments illustrated here in Figures 2
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and 3, electric pulses P generated by multivibrator ~5 or logic
circuit 6~ are sent to a signal transmitter 60 and converted to
electromagnetic pulses as control signals S, ir' particular
optical signals or radio signals. These electromagnetic control
signals S can be transmitted in such a way that they are
electrically isolated (potential-free).
Resistors 62. 63, 62A and 63A of the camparator circuit may be
fixed 4r adjustable, variable resistors or a combination of the
two. Instead of the Camparator circuit illustrated in Figures 2
and ~. other comparator circuits are also possible for comparing
the prevailing power supply voltage U with its reference value
REF: those skilled in the art will be familiar with such
options.
F~trtherrnare, in all embodiments, the power supply current for
consumer 2 can be regulated instead of the power supply voltage.
Regulator 6 is then connected in series with consumer 2 to
measure the power supply current and it comprises a reFerence
current generator and a corresponding cam.parator circuit for
comparing the power supply current and the reference current,
Figure 4 shows one embodiment of power controller 7 that can be
combined to advantage with an embodiment of regulator 5
illustrated in Figures 2 and 3. A signal receiver ~o receives
electrarnagnetic control signals S from signal transmitter 60
(not shown in Figure 9) and converts them to electric pulse
signals S'. These eleCtrie pulse signals 5' are sent to a
monostable multivibratar 71 that forms normalized pulses S'° from
pulse signals S' by normalizing them with regard to amplitude
and duration and synchronising them with one edge of pulse
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signals S'. These normalized pulses 5" are then sent to an
integrator 7~. Integrator '72 then integrates normalized pulses
S" over a predefined interval and supplies at its output an
integrator current r2, the intensity of which corresponds to the
computed integral over time. Furthermore, a current source 73 is
provided to generate a constant basic current Il. Total current
I1 + I2 resulting from basic current I1 and integrator current
I2 is sent to a control unit 79. Control unit 74 supplies
control current T for transmitter 3 (not Shawn .in Figure 4). The
higher the total current rl + I2 at the input of control unit
74, the higher is control current T.
A control arrangement according to Figure 1 with a regulator 6
according to Figure 2 ox Figure 3 and a power controller 7
according to Figure 4 is preferably operated as follows. Control
unit 79 at first receives only basic current Il of current
source 73. Control unit 74 supplies transmitter 3 with a
corresponding control current T. The corresponding basic
transmitting power of transmitter 3 is transmitted with
eleCtxomagnetic radiation R to receiver 4 where it is converted
to a basic power supply voltage US = U~. Hasic current I1 is set
so that control difference Uo - REF between this basic power
supply voltage Uo and reference value REF is Less than zero,
i.e., Ua - REF < Q. The two tolerance values xl and x2 of
regulator 6 are preferably set to be equal to zero, i.e., xl
x2 = 0, so the tolerance intereal consists only of the zero
point 0 as the single tolerance value. Since it holds that ~U
U a REF < xl = 0 because U s US = TJa, regulator 6 generates
control pulses 5 that are transmitted to power controller 7.
Integrator 72 in power controller 7 generates an integrator
current T2 that is different from hero> Cgntrol unit 74 then
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~.ncreases the transmitting power t~f transz~itter 3 through
control current T. This resuJ.ts in an increase in power suppler
voltage U at consumer 2. Regulator 6 transmits control signals S
as long as control difference aU is less than zero i.e_, DU = U
- FIEF ~ 0. Regulator 6 no lange~' transmits control signals S
when power supply voltage U is equal to or greater than
reference value REF, i.e., nU = U ~ REF ~ ~. rntegratar current
I2 of integrator '7z decreases according to the predefined time
constant of integrator ~2. 'Then power supply voltage U drops
again. As soon as power supply voltage U is again lower than
reference value REF, l . a . , AU = U -~ REF < ~, regulator 6 begins
again to increase the transmitting power of transmitter
through new control signals S. '
In an embodiment not illustrated here far regulating the pawe~c
supply vo~.tage ar current far the electric consumer, the
measured value factual value) c~f the power supply voltage or
current far the consumer', which is measured by a measurement
device, can be digitized and transmitted as a digital
measurement signal to a digital compar.~ng element. The actual
digital value of the power supply voltage ox current can
preferably be transmitted in the form of electromagnetic waves
from a signal transmitter that is electrically connected to the
measurement device to a signal receiver that is electrically
connected to the comparing ele~.ent. The cigital comparing
element compares the received actual digital value of the power
supply voltage or current with a stared digital reference value.
Then control current T for transmitter 3 is adjusted by a power
controllez according to the result of this comparison. Far
example, control current T is increased when the control
difference between the digital value of the: power supply voltage
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or current and the digital reference value is less than a first
predefined tolerance value which is non-positive, x1 s 0, and it
is reduced when this control difference is greater than a second
predefined tolerance value which is non-negative, xZ a 0.
However, if the control dzf~erence is within the tolerance
interval (x1, x2], control current T and thus the transmitting
power of transmitter 3 axe kept constant. A suitable
controllable current source can be provided in this case as the
power controller for regulating the control current T.
The measured actual value of the power supply voltage or current
can of course also be transmitted as an analog value in the farm
of electromagnetic radiation to a comparing element, e.g., a
comparator circuit or an analog-digital converter with a
downstream digital comparing element.
To prevent the transmitting powex of transmitter 3 from assuming
excessively high levels during the regulation, a protective
device may also be provided to interrupt the power supply to
transmitter 3 at a predefined maximum transmitting power of
transmitter 3 or maximum control current T. To do so, the
transmitting power of transmitter 3 may be monitored, e.g., by a
monitoring photodiode~ or control current T may be monitored.
To transmit the power for consumer 2, optical transmission
systems or radio transmission systems may be provided. A laser,
a laser diode, an LED or some other light source may be provided
as optical transmitter 3. For example, a photoel2ment or a
photodiode or preferably an array of such photoelectric
Converters may be provided as optical receiver 4. bight can be
transmitted as electromagnetic radiation R from transmitter 3 to
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receiver ~ over optical Fibers ox by a free beam arrangement. rf
the power is transmitted as electromagnetic radiation R by radio
waves, any suitable radio transmitter can be used as transmitter
3 and any suitable radio receiver can be used as receiver 4.
Control Signals S can also be transmitted via light waves or
radio waves. Signal transmitter 60 and signal receiver 70 are
then appropriate optical components or radio companents.
In all era.bodiments, a pluraixty of consumers 2 can also be
supplied with power by one or more transmitters 3. Each consumer
2 is then provided with a receiver 4 that converts
electromagnetic radiation R from the minimum of one transmitter
3 to a power supply voltage U9 or a power supply current for an
electric consumer Z. In this case, synchranizatian signals for
Syncrironous Control of consumers 2 can also be transmitted with
electromagnetic radiation R. To do so, control current T of the
minimum of one transmitter 3 can be modulated accordingly.
In a special embodiment of the arrangement, an electric sensor,
e.g., a current transformer or voltage transformers is provided
as consumer 2. The measurement signals of the sensor, preferably
digitized. are preferably transmitted over the same transmission
link as control signals S of regulator 6. In this case, a logic
circuit may be provided to carry control signals S of the
regulator, the digital measurement signals and corresponding
data control pulses an the transmission link between signal
transmitter 60 and signal receiver 70.
In addition, the transmission link between transmitter 3 and
receiver 4 may also be designed to be bidirectional, by
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transmitting the power and the measurement signals of the sensor
and/or control signals S of regulator 6 with a time offset or in
different wavelength ranges by a time multiplex method or a
wavelength multiplex method.
Reference value REF for regulating the power supply voltage U or
the power supply current can be adjusted or controlled during
regulation if power consumption by the consumer varies. Then, in
the terminology of control technology, REF is th.e reference
variable of the Control circuit.
Figure 5 shows a schematic diagram of a measurement system,
wherein currents and voltages are measured at a high potential
for example. However, the measured values thus obtained must be
reliably isolated when transmitted to electronic analyzer 5. As
this diagram shows, electronic sensor 9 and electronic analyzer
~ are spatially isolated from each other. The electric isolation
is accomplished by means of two separate optical xibers 9 and
10. then uslrig different wavelengths. it is also possible to
transmit power and data over a single optical fiber. A
fiberglass ox plastic optical fiber may be used as optical fiber
9 or 10. The type of optical fiber used will depend an the
wavelength of the light used, because the wavelength det6rmines
the attenuation. Power to supply the electronic sensor is
transmitted over optical fiber 9. For this purpose, transmitter
3 delivers to electronic analyzer ~ an electromagnetic radiation
R that is converted back to electricity in a receiver 4, which
is also referred to as an energy converter. Such an energy
converter 4 is a photoelement by design. As a rule, a plurality
of photocells, e.g., GaAs photocells, are connected electrically
in series to achieve a higher output voltage. Transmitter 3 may
1?
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be, far example, a laser diode that emits light at a wavelength
of approx. 85~ nrn. Voltage US (praduGed] by energy converter
serves to power electronic sensor 8 directly, i.e " W shout any
additional local voltage regulation. To guarantee a more
reliable power supply to consumer 2, it is advisable to buffer
the output of energy converter 4 with a capacitor. Then the
power supply voltage USp is available at this buffered output
In order for power supply voltage UsP to nevertheless remain
constant, a regulator 6, having a voltage divider 11, a
cornpaxing element 12, a PWM modulator 19 and a reference value
generator 61 is provided to regulate power supply voltage USp.
First, power supply voltage Usp is measured and compared with a
reference voltage U~f used as reference value REF. Because
output voltage Usp of energy converter ~ forms power supply
voltage USP of the entire electronic sensor circuit 8, and thus
the value of reference voltage URIC is smaller than the value of
power supply voltage Usp, so output voltage Usp that has been
stepped down by voltage divider 11 is used for the comparison in
the embodiment illustrated hexe. Reference voltage U~~ is
generated according to referencz value generator ~1 and sent
both to a positive input of comparing element 12 and to consumer
2, which comprises a signal amplifier and an AjD converter, for
example, arid is linked to a sensor 13. Output voltage Usp Of
voltage divider 11 is available at the negative input of this
comparing element 12. Differential voltage 0L', also referred to
as control difference aU, which is obtained at the output of
comparing element 32, fs sent to PWM modulator 14. The design of
PWt~ modulator 1Q is shown in more detail as a block schematic in
Figure 6. The output of this PW'M modulator 14 is connected to a
digital mixing device 15, such as a multiplexer. The other input
18
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of this digital mixing device 15 is connected to the output of
consumer 2, in particular to its AlD converter. By means of this
digital mixing device 15, the resulting PWM signal Spy of PWM
modulator 14 together with data signal S~ of consumer 2 is
transmitted as mixed signal S~ to electronic analyzer 5 over
optical fiber 10.
Mixed Signal 5~,,,p is separated in the electronic analyzer back
into data signal SQ and rWM signal SAM. Although data signal So
is sent on to a processor, PWM signal S~~ is applied as an input
signal to a power controller 7 that adjusts the power of
transmitter 3 so that voltage Us or USp produced by energy
c4nverter 4 is kept constant. A demodulator 16 is used to
isolate data signal So of consumer 2 from PWM signal Spy of PWM
modulator 19 and is connected at its output to an interface 17.
A processor can be provided at interface 17 for further
processing of data signal So of consumer 2. In addition, power
controller 7 is also connected to interface 17. A PI controller,
for examFle, is provided as power controller 7, because a tirne-
coded analog signal is transmitted as ~WNi signal 5~~. Regulation
with especially good properties can be achieved by transmitting
a quasi~analog control difference aU for power supply voltage
Usp.
Due to the use of PWM modulator 14, so that control difference
~U is transmitted by means of a PWM signal 5pw," no limit Cycles
occur in voltage regulation, so the load on laser diode 3 is
reduced. Furthermore, the stability properties 4f the control
circuit are improved. Finally, more sudden disturbances, such as
a difference in power consumption by consumer 2 or a disturbance
in the laser current, can be controlled with this embodiment.
1~
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Figure 6 shows the block schematic of one embodiment of ~WM
modulator 14 of electronic sensor 8 from Figure 5. T:nis PWI~i
modulator 19 contains a comparing el.ernent 16, a camparator 19
and a modulation generator 20. The positive input of comparing
element 18 forms the input of modulator 14, and the output of
comparator 19 forms the output of modulator 14. The negative
input of comparing element 18 is connected to the output of
modulation generator 20, and the output of this comparing
element 18 is connected to the input of comparator 19. A saw-
tooth voltage generator is provided as the modulation generatof
20. Instead of the saw-tooth voltage] same other periodic
modulation voltage U~,~ such as a delta voltage may also be used
as modulation voLt~age U,~d. furthermore, the modulation generator
may also generate an asymmetrical and delta-like modulation
signal comprising exponential functions ("e" functions). PWM
modulator 14 is preferably designed to convert the voltage
difference to a PWM signal SQ,,~ only in a range around the
desired voltage U~ ~ UR,~. fihis yields a highex resolution and
thus better control quality-. The above-mentioned modulation
range fox the contxol difference aU that is determined can be
adjusted by means of the amplitude of the modulation voltage
U,~ .
Good stability properties of the control circuit are achieved in
regulating the powex supply voltage USp of consumer 2 due to the
design of regulator 6 of electronic sensor 8 aGCarding to
Figures 5 and 6, whereby the control difference bU is
trapsmitted with the help of a PWM signal SQ~,,,~, One b~.t alone is
sufficient for this type of transmission. Since a time~coded
analog signal is transmitted with PWM signal Sue" a pI
controller can be used as power controller '7 to regulate the
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power of transmitter 3 of electronic analyzer 5, thus yielding
linear contra:.
In addition. aging of the power transmission system can be
determined Qn the basis of the current flowing through laser
diode 3 because the power supply voltage of electronic sensor B
is regulated. To do so, the prevailing current must be based
only on the current flowing at the time of start-up of the
sensor system. However, it is assumed here that the aging of
transmitter 3 is a measure of the aging of the sensor system as
a whole.
Maintenance information can thus be generated by monitoring the
laser diode current.
Destruction of one of the two optical fibers 9 and 10 is one
source of defects that must always be expected. This always
interrupts the data stream transmitted from consumer 2 to
electronic analyzer 5, because either the power supply in
electronic sensor 8 collapses or the information is simply no
longer transmitted. However, such a data strea,z~ failure can also
be detected easily in electronic analyzer 5.
Then in such a case, transmitter 3 must be switched off because
otherwise high-energy invisible light will escape at the break
point and can cause eye damage. The corresponding switch-off
signal is obtained by monitoring the continuity of the data
stream.
21
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