Electric power conversion systems – Current conversion – Including automatic or integral protection means
Reexamination Certificate
2001-12-14
2003-05-06
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including automatic or integral protection means
C379S412000
Reexamination Certificate
active
06560129
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a power supply unit for generating a protective current (sealing current), which is superposed on signal currents carried by metal lines for protection against corrosion. The invention also relates to a process for generating such a protective
BACKGROUND OF THE INVENTION
The metal lines used for transmitting signal currents, e.g., the copper lines in telephone networks still commonly in use for ISDN terminals, are exposed to corrosion at splices or tie points, which over time results in a deterioration in conductivity along the employed line.
However, it was found that feeding in a low direct current can prevent corrosion of the lines.
Primarily for this reason, a protective current (sealing/wetting current) of several milliamperes is superposed on the irregular and direct current-free data stream via the copper lines in digital subscriber terminal systems that use metal line loops as in the ISDN base terminal (BA).
In systems where a remote feed is set upon the user to supply power to the network terminating unit (NT), the direct current can perform the same function as the protective current on the line resulting from the power consumption by the network terminating unit. By contrast, an application provide for protective current supply is normally not used to supply power to network terminating units.
Another potential application for protective current is to use it as a line detection signal for network terminating units (NT). In an ISDN network, the network terminating unit on the user side forms the transition between the basic terminal interface (U interface), which establishes the connection to a central office, and the standardized S
0
interface, to which users can hook up their terminals.
According to standard ANSI T1.601-1992, which describes the basic terminal interface when using metal line loops in ISDN applications, it is not absolutely necessary to provide a protective current. However, if a protective current is provided, certain requirements have to be met. If it does not measure 0 mA, the protective current must exhibit values ranging between 1 mA and 20 mA. In addition, the maximal allowable change rate for the protective current is 20 mA/s.
Other requirements are placed on the metal terminating unit (metallic termination) of a network terminal device, which provides a non-linear direct current path as the sink for the protective current fed in via the terminal lines. The operating states of the metal terminating unit are the non-conducting state OFF (high impedance) and conductive state ON (low impedance).
If a voltage to range between 30 V and 39 V is applied for a preset time to range between 3 ms and 50 ms in the OFF state of the metal terminating unit, a switch is made to the ON state. In this case, the state is to switch within at most 50 ms starting from the point the preset voltage was exceeded. A state change does not take place even at voltages exceeding the preset voltage if it is exceeded for less than 3 ms.
If the current drops below a preset current value (0.1-1.0 mA) for a preset time (3-100 ms) in the ON state of the metal terminating unit, a switch is to be made to the OFF state. In this case, the state is to change within at most 100 ms starting from the point at which levels dropped below the preset current. A state change does not take place even at currents less than the preset current is it levels remain below the preset current for less than 3 ms.
The process of feeding a protective current into the data transmission lines must not disrupt ongoing transmissions. For this reason, it is essential that a stable ON state be ensured for the metal terminating unit of a network terminal unit, and that current changes not arise too abruptly.
Therefore, the power supply unit in, the line terminal unit must satisfy several special requirements to reliably ensure a stable operation of the metal terminating unit of the network terminal unit on the user side.
SUMMARY OF THE INVENTION
The object of the invention is to provide a power supply unit that is particularly suited for delivering ANSI T1.601-1992-conformant protective currents (sealing currents) for digital user terminal lines.
The object is solved according to the invention on the one hand by a power supply unit for generating a protective current (sealing current), which is superposed on the metal lines via signal currents transmitted via metal lines for protection against corrosion at tie points or splices; this power supply unit
exhibits two voltage-controlled power sources, wherein the first power source is capable, depending on an applied voltage, of outputting a constant current having a first value of 0 mA, or a constant current having a second value of at least 1 mA, in particular 1.2 mA, and wherein the second power source is capable, under a threshold value, in particular of 0 V, of the applied voltage, of outputting a constant current having a third value of 0 mA, and, above the threshold value of the applied voltage and proportional to the latter, a current between the constant current of the third value and a fourth value of 20 mA diminished at least by the constant current having the second value of the first power source,
exhibits at least one voltage input, which is connected with the control input of the second power source via an integrator, and
exhibits a current output, with which both the output of the first and the output of the second power source are connected for outputting the sum of the currents delivered by both power sources.
In addition, the object is achieved according to the invention by a process for generating a protective current (sealing current) for protection against corrosion of splices and/or tie points of metal lines via a power supply unit, which comprises a first and second voltage-controlled power source, wherein the first power source is capable, depending on an applied binary control voltage, to generate a constant current having a first value of 0 mA, or a constant current having a second value of at least 1 mA, in particular 1.2 mA, and wherein the second power source is capable, at below a threshold value, in particular of 0 V, to generate a constant current having a third value of 0 mA, and at above the threshold value of the applied voltage and proportional to the latter, a current between the constant current having the third value and a fourth value 20 mA diminished at least by the constant current having the second value of the first power source, characterized by the following steps:
application of an input voltage to the voltage input of the power supply unit,
generation of a binary input voltage from the applied input voltage, unless binary application of the latter has already taken place,
integration of the binary input voltage, in particular via RC integration,
shifting of integrated voltage by a negative offset voltage,
generation of binary control voltage by comparing the input voltage, integrated input voltage or integrated and shifted input voltage with a reference value using a comparator,
generation of an initial output current via the first power source, controlled by the binary control voltage,
generation of a second output current via the second power source, controlled by the integrated and shifted voltage,
addition of the first and second output current into a total current to be used as a protective current, and
output of the protective current on the metal lines to be protected against corrosion.
The binary control voltage should assume a high level during acceleration, before the shifted voltage exceeds the threshold value, and assume a low level during deceleration, before the shifted voltage again drops below the threshold value.
With the power supply unit and process according to the invention, it is possible to provide a protective current that satisfies the ANSI T1.601-1992 requirements.
The power supply unit according to the invention can be operated in such a way as to generate and output a protective current that measures either 0 mA, or runs between a value&g
Berhane Adolf Deneke
Cohen & Pontani, Lieberman & Pavane
Nokia Corporation
LandOfFree
Power supply unit and process for generating protective... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power supply unit and process for generating protective..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power supply unit and process for generating protective... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3033138