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Claims  |
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I claim:
1. A surge/transient protector for protecting a plurality of N data lines,
grouped together at a given location, on which lines data are transmitted
within a given data voltage range, each data line comprising first and
second data conductors and a return conductor, the protector comprising:
N data line segments each including first and second data conductor
segments and a return conductor segment;
first and second connector means for connecting each of the N data line
segments in series in one of the N data lines;
a positive bus, a negative bus, and a reference bus;
grounding means for connecting the reference bus to a plane of common
potential;
first unidirectional coupling means coupling each data conductor segment to
the positive bus;
second unidirectional coupling means coupling each data conductor segment
to the negative bus;
bi-directional return coupling means coupling each return conductor segment
to the reference bus;
a first large transient/surge energy storage device, connected between the
positive bus and the reference bus, and having a positive threshold
potential slightly larger than one-half the data voltage range;
a second large transient/surge energy storage device, connected between the
negative bus and the reference bus, and having a negative threshold
potential approximately equal to the positive threshold potential; and
N discharge devices, each connected to the plane of reference potential and
to the first and second data conductors in one data line segment, the
discharge devices having a breakdown potential much higher than the data
voltage range.
2. A surge/transient protector for a group of N data lines, according to
claim 1, in which each coupling means comprises a pair of diodes, and
further comprising:
3N current limiting resistors, each connected in series with one of the
conductor segments.
3. A surge/transient protector for a group of N data lines, according to
claim 1, and further comprising:
N supplemental transient/surge energy storage devices, each connected
between the return segment and one of the data conductor segments for one
data line, each supplemental energy storage device having a threshold
voltage of at least twice the data voltage range.
4. A surge/transient protector for a group of N data lines, according to
claim 3, in which each supplemental energy storage device is a metal oxide
varistor, and in which each coupling means comprises a pair of diodes.
5. A surge/transient protector for a group of N data lines, according to
claim 1, and further comprising:
power supply means for generating a positive bias potential, above the
reference plane, greater than one-half the data voltage range but smaller
than the positive threshold potential, and for generating a negative bias
potential, below the reference plane, having an amplitude equal to the
positive bias potential;
and bias connecting means for connecting the positive bias potential to the
positive bus and the negative bias potential to the negative bus.
6. A surge/transient protector for a group of N data lines, according to
claim 1, in which each primary and secondary transient/surge energy
storage device is a capacitor connected in parallel with a semiconductor
voltage threshold regulator.
7. A surge/transient protector for a group of N data lines, according to
claim 6, in which each voltage threshold regulator is an avalanche Zener
diode.
8. A surge/transient protector for a group of N data lines, according to
claim 6, in which each voltage threshold regulator is a varistor.
9. A surge/transient protector for a group of N data lines, according to
claim 6, and further comprising:
N supplemental transient/surge energy storage devices, each connected
between the return segment and one of the data conductor segments for one
data line, each supplemental energy storage device having a threshold
voltage of at least twice the data voltage range.
10. A surge/transient protector for a group of N data lines, according to
claim 9, in which each coupling means comprises a pair of diodes.
11. A surge/transient protector for a group of N data lines, according to
claim 9, and further comprising:
power supply means for generating a positive bias potential, above the
reference plane, greater than one-half the data voltage range but smaller
than the positive threshold potential, and for generating a negative bias
potential, below the reference plane, having an amplitude equal to the
positive bias potential;
and bias coupling means for coupling the positive bias potential to the
positive bus and the negative bias potential to the negative bus.
12. A surge/transient protector for a group of N data lines, according to
claim 11, in which each coupling means comprises a pair of diodes.
13. A surge/transient protector for a group of N data lines, according to
claim 6, and further comprising:
power supply means for generating a positive bias potential, above the
reference plane, greater than one-half the data voltage range but smaller
than the positive threshold potential, and for generating a negative bias
potential, below the reference plane, having an amplitude equal to the
positive bias potential;
and bias coupling means for coupling the positive bias potential to the
positive bus and the negative bias potential to the negative bus.
14. A surge/transient protector for a group of N data lines, according to
claim 3, and further comprising:
power supply means for generating a positive bias potential, above the
reference plane, greater than one-half the data voltage range but smaller
than the positive threshold potential, and for generating a negative bias
potential, below the reference plane, having an amplitude equal to the
positive bias potential;
and bias coupling means for coupling the positive bias potential to the
positive bus and the negative bias potential to the negative bus.
15. A surge/transient protector for a group of N data lines, according to
claim 14, in which each coupling means comprises a pair of diodes.
16. A surge/transient protector for a group of N data lines, according to
claim 12, in which:
the data voltage range is fifty volts;
the positive and negative threshold potentials for the first and second
storage devices are each approximately twenty-seven volts;
the breakdown potential of the discharge devices is approximately eighty
volts;
the threshold voltage of the supplemental storage devices exceeds one
hundred volts;
and each diode in the coupling means is a suppressor diode having a
breakdown voltage exceeding eighty volts.
17. A surge/transient protector for a group of N data lines, according to
claim 1, and further comprising a unitary housing encompassing all of the
surge/transient protector circuit components.
18. A surge/transient protector for a group of N data lines, according to
claim 17, in which each coupling means comprises a pair of diodes, and
further comprising:
3N current limiting resistors, each connected in series with one of the
conductor segments within the housing.
19. A surge/transient protector for a group of N data lines, according to
claim 17, and further comprising:
N supplemental transient/surge energy storage devices, mounted within the
housing and each connected between the return segment and one of the data
conductor segments for one data line, each supplemental energy storage
device having a threshold voltage of at least twice the data voltage
range.
20. A surge/transient protector for a group of N data lines, according to
claim 19, in which each primary and secondary transient/surge energy
storage device is a capacitor connected in parallel with a semiconductor
voltage threshold regulator. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
At a mainframe computer or other data processing center of substantial size
there are usually one or more data cables, converging on the data
processing center from a plurality of peripheral stations. A typical cable
may contain sixteen data lines, each data line including two data
conductors and a return conductor; the same cable usually includes two
ground lines, so that a conventional fifty pin connector serves to connect
the cable to the computer. Of course, other cable sizes employing
different connectors (e.g., twenty-five or one hundred pins) are also
employed in essentially the same way. In any such data system there is a
preselected voltage range for transmission of data on the data conductors,
usually balanced with respect to the return conductor; a typical range is
fifty volts, twenty-five volts of each polarity relative to ground.
Any voltage outside the preselected data voltage range, on any of the
conductors, may cause physical damage to the computer, to the peripheral
stations, or to the cable, in addition to interfering with the data
transmission. This problem applies to very brief voltage transients as
well as to voltage surges of appreciable duration; any and all overvoltage
surges and transients may be quite deleterious. Thus, the cable, or
separate data lines, and particularly the computer or other data
processing equipment, need protection against overvoltage surges of any
origin. That is the aim of the present invention.
SUMMARY OF THE INVENTION
It is a principal object of the invention, therefore, to provide a new and
improved apparatus for protecting N plural-conductor data lines, and a
computer or other data processing equipment connected to those lines,
against voltage surges or transient voltages that exceed a preselected
data voltage range, all of the apparatus being mounted in a compact,
unitary housing.
Another object of the invention is to provide a new and improved
surge/transient protector for N plural-conductor data lines that is
compact, simple, and economical in construction, yet durable and
dependable in operation.
Accordingly, the invention relates to a surge/transient protector for
protecting a plurality of N data lines, grouped together at a given
location, on which lines data are transmitted within a given data voltage
range, each data line comprising fist and second data conductors and a
return conductor; the protector comprises N data line segments each
including first and second data conductor segments and a return conductor
segment, first and second conductor means for connecting each of the N
data line segments in series in one of the N data lines, a positive bus, a
negative bus, and a reference bus, and grounding means for connecting the
reference bus to a plane of common potential. First unidirectional
coupling means are provided for coupling each data conductor segment to
the positive bus, with second unidirectional coupling means for coupling
each data conductor segment to the negative bus, and bi-directional return
coupling means for coupling each return conductor segment to the reference
bus. A first large transient/surge energy storage device is connected
between the positive bus and the reference bus, having a positive
threshold potential slightly larger than one-half the data voltage range;
a second large transient/surge energy storage device is connected between
the negative bus and the reference bus, having a negative threshold
potential approximately equal to the positive threshold potential. N
discharge devices are each connected to the plane of reference potential
and to the first and second data conductors in one data line segment, the
discharge devices having a breakdown potential much higher than the data
voltage range. A unitary housing encompasses all of the surge/transient
protector components as set forth above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the use of surge/transient
protectors constructed in accordance with the present invention; and
FIG. 2 is a schematic diagram of a surge/transient protector according to
one embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a general illustration of a typical environment in which a
surge/transient protector device constructed in accordance with the
present invention is employed. FIG. 1 shows a mainframe computer 60 that
is connected to a multiplicity of data terminals or work stations. Each
data terminal in one series 61-1 through 61-16 is connected to a
communication cable 81. Each data terminal is shown as having four
conductors connected to the cable. These conductors usually include first
and second data conductors, a return conductor, and a reference or ground
conductor. Each such set of conductors constitutes a data line. However,
not all of the conductors continue individually through cable 81; cable 81
may contain only one or two ground conductors serving all of the data
lines in the cable.
FIG. 1 shows another series of data terminals 62-1 through 62-16; these
data terminals are all connected to mainframe computer 60 by means of a
cable 82. Again, each data line for each data terminal includes two data
conductors and a return conductor; reference or ground conductors may also
be provided. Other cables (not shown) may be utilized to connect
additional data terminals or work stations to mainframe computer 60.
Two surge/transient protector devices 80 and 90 are shown in FIG. 1, each
connected in series with one of the cables 81 and 82 that supply data to
and transmit data from mainframe computer 60. Thus, protector 80 is
interposed in series between cable 81 and another cable 83 that is a
continuation of cable 81 and connects directly to computer 60. Similarly,
a cable 84 extends the data lines of cable 82 to computer 60, with the
surge/transient protector 90 interposed in series. The same arrangement
would apply to any additional cables. As will be apparent from the
description hereafter, protectors 80 and 90 could be constructed as a
single device. The illustrated arrangement, with one protector circuit for
each cable, however, is usually more flexible and more economical.
In conventional construction, each of the cables 81, 82, etc., is likely to
include sixteen data lines, with each line comprising three conductors
(two data conductors and a return). The data conductors are sometimes
called a transmit conductor and a receive conductor. In addition, in a
conventional cable there would be two ground conductors for a total of
fifty conductors in the cable. Thus, conventional fifty pin connectors may
be used to connect each cable to apparatus such as the mainframe computer
60. In the arrangement illustrated in FIG. 1, two connectors 85 and 87
connect protector 80 to cables 81 and 83, whereas two other connectors 86
and 88 connect cables 82 and 84 to the other protector 90.
A preferred embodiment of surge/transient protector 80 affording a simple
and economical structure for protecting all of the data lines in cable 81
against the effects of lightning, overvoltage surges, and other similar
occurrences, is illustrated schematically in FIG. 2. Dash outline 80
represents the housing of the protector unit. Protector 90, FIG. 1, may
incorporate the same construction.
Protector 80, FIG. 2, includes a first or positive bus 91, a second or
negative bus 92, and a reference bus 93 having an appropriate connection
94 to ground. As seen at the bottom of FIG. 2, a first transient/surge
suppressor comprising a large charge storage device, the capacitor 95, is
connected between positive bus 91 and reference bus 93. A voltage
threshold regulation device 105 is connected in parallel with capacitor
95; device 105 is preferably a silicon avalanche Zener diode. Other
devices may be used for regulation of the discharge voltage for capacitor
95, including other semiconductor avalanche diodes and varistors.
Regardless of the type, device 105 should have a breakdown (threshold)
voltage slightly greater than one-half the overall data voltage range for
the data lines of cable 81 that are to be protected by circuit 90. As an
example, the data transmission range for the system shown in FIGS. 1 and 2
may be taken as plus and minus twenty-five volts. As indicated in FIG. 2,
in these circumstances the threshold voltage for regulator 105, and hence
for discharge of capacitor 95, may be higher, up to about thirty-five
volts as a maximum, but preferably is no more than a few volts in excess
of one-half the overall data voltage range.
A second transient/surge charge storage device 96 is connected between
negative bus 92 and ground bus 93. Device 96 should be matched with
capacitor 95 so that two charge storage devices have the same operating
characteristics. A threshold voltage regulator 106, matched to Zener diode
105, is connected in parallel with capacitor 96. Preferably, the two
storage devices 95 and 96 are large capacitors; e.g., 10,000 microfarads.
The DC voltage ratings of these capacitors should be greater than the
breakdown voltage of devices 105 and 106. Thus, assuming that devices 105
and 106 are Zener avalanche diodes rated at twenty-seven volts for
breakdown, the DC voltage ratings of capacitors 95 and 96 may be
thirty-five volts.
A power supply 101 energized through a conventional plug connector 102
connected to an external AC power source (not shown) is provided for buses
91-93 in protector circuit 90. As shown, power supply 101 includes a
bridge circuit 103 having its input terminals connected to plug 102. The
positive and negative output terminals of bridge 103 are connected to
positive bus 91 and negative bus 92, respectively. Plug 102 includes a
ground connection so that the output voltage from power supply 101 is
balanced in its application to buses 91 and 92, relative to ground bus 93.
Power supply 101 may be replaced by other power supply arrangements, such
as a pair of batteries, one connected between buses 91 and 93 and the
other between buses 92 and 93. In some instances, power supply 101 may
even be omitted.
The mainframe data line protector 80 includes coupling means for coupling
all of the conductors in each data line of cable 81 to both the positive
and negative buses 91 and 92. FIG. 2 shows the coupling arrangements for
three data lines 111, 112, and 126, which are assumed to be the first two
lines and the last line from a sixteen line cable 81. For data line 111,
there is a first (positive) data conductor segment 131, a second data
(negative or receive) conductor segment 133, and a return conductor
segment 132. A current-limiting resistor 134 is in series with the first
data conductor segment 131; conductor segment 131 is coupled to positive
bus 91 by a diode 135 and is coupled to negative bus 92 by an
oppositely-polarized diode 136. Typically, resistor 134 may be ten ohms;
diodes 135 and 136 may be suppressor diodes rated at eighty-two volts. The
second data conductor segment 133 for line 111, which includes a series
current limiting resistor 137, is coupled to positive bus 91 by a diode
138 and to negative bus 92 by a diode 139. The return conductor segment
132 for data line 111, in which a current limiting resistor 141 is
interposed, is coupled to ground bus 93 by two oppositely polarized diodes
142 and 143. Resistors 134, 137 and 141 should all have the same impedance
and voltage rating; diodes 135, 136, 138, 139, 142, and 143 should all be
matched to each other. Series IN4000 diodes are suitable.
Two additional protective devices are provided for data line 111, in the
circuit arrangement of FIG. 2. One is a three-electrode gas discharge tube
144 that has two electrodes connected to the two data conductor segments
131 and 133 at the side of circuit 80 to which cable 81 is connected by
connector 85. The third electrode of tube 144 is connected to ground.
Typically, for a system having a data voltage range of fifty volts, the
breakdown voltage for gas tube 144 may be eighty volts. The other
protective device for line 111 is sown as a metal oxide varistor (MOV) 145
connected from data conductor 133 to return conductor 132 at the side of
protector circuit 80 that is connected to cable 83 by connector 87.
Actually, MOV 145 functions, in protector 80, as if it were a large
capacitor or other such storage device. The breakdown voltage for device
145 should be substantially higher than that of any of the other protector
elements in circuit 80, well beyond the anticipated range of voltages on
the lines of cable 81. In the illustrated system, functioning within the
parameters given above, the breakdown rating for MOV 145 may be one
hundred thirty volts.
Positive-polarity surges and transient on conductor segment 131, from
voltages occurring on the corresponding data conductor in cable 81, are
usually diverted to positive bus 91 through diode 135 and are effectively
dissipated by charging of capacitor 95. Any excess charge on device 95 is
ultimately discharged to ground through diode 105. Negative-polarity
surges on conductor segment 131 are disposed of similarly through diode
136 and bus 92, and are absorbed by capacitor 96, regulated by diode 106.
For data conductor segment 133 of line 111 the process is similar;
positive-going line surges are usually diverted to bus 91 via diode 138
and are dissipated by charging of capacitor 85, whereas negative polarity
transients traverse diode 139 to bus 92 and are spent charging capacitor
96.
Typically, for a system having a data voltage range of fifty volts, the
breakdown voltage for gas tube 144 may be eighty volts. The other
protective device for line 111 is shown as a metal oxide varistor (MOV)
145 connected from data conductor 133 to return conductor 132 at the side
of protector circuit 80 that is connected to cable 83 by connector 87.
Actually, MOV 145 functions, in protector 80, as if it were a large
capacitor or other such storage device. The breakdown voltage for device
145 should be substantially higher than that of any of the other protector
elements in circuit 80, well beyond the anticipated range of voltages on
the lines of cable 81. In the illustrated system, functioning within the
parameters given above, the breakdown rating for MOV 145 may be one
hundred thirty volts.
Positive-polarity surges and transients on conductor segment 131, from
voltages occurring on the corresponding data conductor in cable 81, are
usually diverted to positive bus 91 through diode 135 and are effectively
dissipated by charging of capacitor 95. Any excess charge on device 95 is
ultimately discharged to ground through diode 105. Negative-polarity
surges on conductor segment 131 are disposed of similarly through diode
136 and bus 92, and are absorbed by capacitor 96, regulated by diode 106.
For data conductor segment 133 of line 111 the process is similar;
positive-going line surges are usually diverted to bus 91 via diode 138
and are dissipated by charging of capacitor 95, whereas negative polarity
transients traverse diode 139 to bus 92 and are spent charging capacitor
96. Transients on return line segment 132, on the other hand, are coupled
directly to ground bus 93 through one of the diodes 142, 143, depending on
the polarity of the transients. In all of these functions, resistors 134,
137 and 141 serve to limit the currents developed by the surges.
For transients on line segments 131 and 133, at voltages exceeding the
breakdown rating for gas tube 144 (eighty volts), the gas tube is driven
conductive. This effectively increases the capacity of protector 80 for
such surges, affording two paths from the affected data conductor segments
to ground. A further line of defense, for high-power surges on the
conductor segments of line 111 in protector 80, is the very large,
high-voltage-rated capacitance afforded by MOV 145, which can absorb
substantial power and serves to protect cable 83 and mainframe computer 60
in surge situations such as may be created by lightning or other violent
electrical occurrences in the vicinity of cable 83 and mainframe computer
60 in surge situations such as may be created by lightning or other
violent electrical occurrences in the vicinity of cable 81 or of one of
the data lines connected to the cable.
As will be apparent from FIG. 2, the circuitry in protector 80 that
protects lines 112 and 126 of cables 81 and 83 (and computer 60) against
transients and other surges is the same as described above for line 111.
Thus, for each of the sixteen data lines traversing protector 80, there is
a three-electrode discharge device coupling the data conductor segments to
ground, for voltages exceeding eighty volts, ahead of a small
current-limiting resistor in each data conductor segment. The return
conductor segment in each line also includes a small current-limiting
resistor. The two data conductor segments are each connected to the busses
91 and 92 by a pair of oppositely polarized diodes; the return conductor
segment is coupled to bus 93 by two oppositely polarized diodes. Thus, the
large storage devices, capacitors 95 and 96, their threshold devices 105
and 106, and power supply 101 all serve all of the data lines. And each
data line has its backup protection from a further energy storage device
corresponding to the MOV 145 connected between conductor segments 132 and
133 in line 111.
From the foregoing description, it will be apparent that in protector 80
the energy storage capacitors 95 and 96, with their respective threshold
establishing voltage regulator devices 105 and 106, each serve all of the
data conductor segments in all of the lines that pass through the
protector. This makes it convenient and practical to put the entire
protector 80, including all of its components as shown in FIG. 2, into a
small, unitary housing. Indeed, the commercial version of protector 80,
the model DLP-50 protector of Oneac Corporation, serving a sixteen-line
cable, fits into a housing approximately 7.times.12.times.3 inches
(17.times.30.times.7.5 cm). Of course, this compact construction is also
made possible because for each data line the protector requires just three
small current-limiting resistors, six very small diodes, a gas discharge
tube about the size of a peanut, and a varistor even smaller than the gas
tube.
In some applications a group of data lines may be brought together at a
mainframe computer or other central location without prior collection into
a cable. For situations of this sort, of course, it is only necessary to
provide appropriate connectors to connect the data lines to a protector
like apparatus 80, which is not dependent upon amalgamation of the lines
into a cable. Regardless of cable arrangements, apparatus 80 affords
superior surge/transient protection in a construction that is simple,
inexpensive, durable, and usually compact. Thus, protector 80, as
described and illustrated, has been demonstrated to conform to the
requirements of ANSI/IEEE specification C62.41, category B, 6,000 V/500 A,
0.5 microsecond, 100 KHz decay, maintaining the transient output at or
below forty volts. The protector does not load the data line.
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