Telephonic communications – Subscriber line or transmission line interface – Network interface device
Reexamination Certificate
1999-08-20
2003-06-24
Tieu, Binh (Department: 2643)
Telephonic communications
Subscriber line or transmission line interface
Network interface device
C379S413000, C379S001010, C379S009050, C379S324000, C700S286000, C363S146000
Reexamination Certificate
active
06584197
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to power management systems and subsystems, and is particularly directed to a new and improved power management scheme for (customer premises installed) digital data services (DDS) telecommunication equipment, that is configured to interface the DDS equipment with both a local utility power source and a telecommunication link (span) that is remotely powered by way of a telecommunication facility, such as a central office. The inventive power management scheme includes an auxiliary energy storage element, such as a capacitor, that stores energy from the local utility power source and the span. The invention monitors the power availability for and requirements of the DDS equipment; if the local utility power is insufficient to maintain proper operation of the DDS equipment, a limited quantity of power is drawn from the span.
BACKGROUND OF THE INVENTION
In addition to sending voice and/or data over the telephone lines, a telecommunication service provider may use the same wires to power circuits, such as DDS terminal devices that are connected to the signal lines at remote locations. The power that is used to operate telecommunication equipment via the signal lines is sourced from the telephone company's central office (CO). This method of remote line powering is commonly referred to as ‘loop’ or ‘span’ powering, and permits the phone companies to remotely power terminal equipment that is up to several miles away from the central office. Loop powering is customarily used extensively on mid-span devices (rather than termination devices) in DDS, ISDN, T
1
, HDSL, and other digital networks. The device at the remote end of the link may or may not continuously need this span-supplied power, or may use this power only during emergency situations. For purposes of the present description, the equipment at the remote end of the link will be referred to as terminating equipment, and typically resides at a customer's premises.
Within the telephone networks of the continental United States, terminating devices for digital data services are generally not span-powered. Instead, the terminating device is typically located within the customer's premises and receives its power from the customer's local utility feed. In normal operating conditions, the only current drawn by the ‘locally powered’ termination device from the network signal wires is what is commonly termed ‘sealing’ or ‘wetting’ current. Wetting current is not necessary for the equipment to operate, but is used to reduce corrosion of the wires and splices between the phone company and the remote location.
However, when local utility power is lost at the customer's premises (for example during a lighting storm), the terminating device will stop functioning. This is problematic for digital services (such as ISDN) that implement plain-old-telephone-service (POTS) support. Should a local power failure occur, there will be a loss of phone service (including emergency service, such as the ability to place a 911 call). As a consequence, customers have traditionally been required to maintain a separate standard analog phone line in addition to the ISDN digital data line(s).
There is currently interest in the both U.S. and abroad to configure terminating devices that can be span-powered. Although there is no applicable U.S. regulation or tariff for span-powering customer premises equipment, the European Telecommunications Standards Institute (ETSI) has released an international technical report ETR080, as a precursor to a possible specification. This technical report recommends that the central office supply between 51 VDC and 115 VDC on the span (depending on its length). The effect of line resistance requires that power drawn by terminal equipment be less than a prescribed value (1100 mW) during worst case conditions. This constitutes a potential problem in the U.S., since a standard ringer equivalency number (REN) load of five (North American) consumes more instantaneous power than is available from the span.
SUMMARY OF THE INVENTION
In accordance with the present invention, these concerns are successfully addressed by a dual power management system, that is readily integrated with customer premises-installed digital data services terminal equipment, and is operative to controllably power such equipment from either or both of a local power source and the span. The invention automatically switches between local powering and remote powering as necessary for terminal equipment operation and sinks wetting current from the network during local powering.
As will be described, the invention is configured to monitor the power availability for and power requirements of termination equipment and, in response to local power being insufficient to maintain operation, derives from the phone line up to a maximum amount of power, which is limited to a fixed value that prevents the line from collapsing, and satisfies current industry proposals, such as that contained in the above-referenced ETR080 report. The inventive power management scheme includes an auxiliary energy store that is controllably operative to store a limited quantity of energy from the local utility interface or the span, so as to enable extended power operation (including ringing the phone).
The general architecture of the dual power management system of the present invention includes a local utility interface and a span interface. The local utility interface has barrier—isolation transformer circuitry configured to connect to a local utility interface—typically, an AC wall outlet—which isolates and transforms the utility voltage to a safe level, such as 42 VDC. A main power converter is coupled to receive the local utility voltage and supplies various regulated voltages as required for terminal equipment communication subsystems.
In addition to being coupled to the local utility interface, the main power converter is coupled to a power limited converter within the span interface. Normally, the span interface provides a signaling interface with the telephone lines, and sinks wetting current. In addition, in response to insufficient local power, the power limited converter derives power from the span to maintain terminal equipment operation. Controlled extraction of a limited amount of power from the span is carried out by a power-limited converter, in response to a reduction or loss of power from the local utility. During this ‘span’—powered mode, the power-limited converter controllably charges an auxiliary energy storage capacitor that is coupled in circuit with each of the local utility interface section, the span interface section and the main power converter. The auxiliary energy storage capacitor is normally charged by transformed voltage from the local utility interface.
A power availability sensing and control unit is coupled to a terminal device control processor and to associated interface circuits, and serves to monitor a number of operational parameters, including performance of the local utility interface, the span, and the amount of energy stored in the auxiliary storage capacitor. This information is used to control various power management subsystems, such as modulation of the span interface section's power limited converter, current limit, start-up control, undervoltage lockout, etc. Undervoltage lockout (UVLO) and start-up circuits are included to ensure that the power circuits are disabled for conditions outside their intended operating range, and to provide for a smooth start-up when power is initially applied.
Should there be a failure or unacceptable reduction of the local utility power, the sensing and control unit will switch the operation of the power management system to ‘span-powered’ mode, so that the power limited converter within the span interface unit will begin drawing the maximum power available from the network, until the auxiliary energy storage capacitor is fully charged. Once the auxiliary storage capacitor is fully charged, the span power will be modulate
Boudreaux, Jr. Ralph R.
McElroy Paul G.
McGary John S.
Robinson Steven M.
Adtran Inc.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Tieu Binh
LandOfFree
Power-limited remote termination converter with wetting... 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-limited remote termination converter with wetting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power-limited remote termination converter with wetting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3138379