Circuit for supplying power to a network termination unit of a message transmission system

• US 20030102852A1
• Filed: 12/24/2002
• Published: 06/05/2003
• Est. Priority Date: 03/22/2000
• Status: Active Grant

• Current Assignee: Flextronics International GmbH & Company NFG KG
• Original Assignee: Flextronics International GmbH & Company NFG KG
• Inventors: Kovarik, Peter
• Granted Patent: US 6,815,844 B2
• Time in Patent Office: Days
• US Class Current: 323/284
• CPC Class Codes: H04L 12/10 Current supply arrangements

Abstract

The invention relates to a circuit for supplying power to a network termination unit (55) of a message transmission system, which is connected to a central station via a subscriber line (30). A local power supply voltage source (41), which is arranged in the network termination unit (55) and which supplies power during a normal operating state, is provided as well as a remote power supply source, which is arranged in the central station and which supplies power during an emergency operating state in the case of a failure or malfunctioning of the local power supply voltage source (41). The network termination unit (55) comprises a direct current converter with a transformer and a clocked switch (20). The primary winding (1) of the transformer is connected via the clocked switch (20) to the local power supply voltage source (41), and a connection of the primary winding (1) is connected via a first controllable switch (5) to a wire of the subscriber line (30).

Claims

1. Circuit for supplying power to a network termination unit of a message transmission system, which is connected to a central station via a subscriber line, wherein there is provided a local power supply voltage source, which is arranged in the network termination unit and supplies power during a normal operating state, and a remote power supply source, which is arranged in the central station and supplies power during an emergency operating state in the case of a failure or malfunctioning of the local power supply voltage source, and wherein the network termination unit includes a direct current converter with a transformer and a clocked switch and wherein the primary winding of the transformer is connected via the clocked switch to the local power supply voltage source, characterized in that a terminal of the primary winding (1) is connected via a first controllable switch (5) to a wire of the subscriber line (30).

2. Circuit according to claim 1, characterized in that the terminal of the primary winding (1) connected with the first controllable switch (5) is connected via a second controllable switch (4) with a buffer capacitor (3).

3. Circuit according to claim 1 or 2, characterized in that the first and second controllable switches are formed by field effect transistors (5, 4).

4. Circuit according to claim 2 or 3, characterized in that the buffer capacitor (3) is connected via a charging branch (17) with a charging voltage source.

5. Circuit according to claim 4, characterized in that the charging branch is formed by a charging resistor (17) which is connected with the subscriber line (30) preferably via a blocking diode (16).

6. Circuit according to one of the claims 1 to 5, characterized that a voltage monitoring unit (15) is provided, whose inputs are connected with the local power supply voltage source (41), and that an output of the voltage monitoring unit (15) is connected with a unit for controlling the first and second controllable switches (5, 4).

7. Circuit according to one of the claims 1 to 6, characterized in that an additional voltage monitoring unit (14) is provided, whose inputs are connected with the subscriber line (30), and that an output of the additional voltage monitoring unit (14) is connected with the unit for controlling the first and the second controllable switches (5, 4).

8. Method for transferring to a network termination unit from a normal operating state to a remotely supplied state by using a switching circuit according to claim 1, characterized in that the amplitude of the local supply voltage is continuously measured and compared with a predetermined minimum value, and that when the predetermined minimum value is underrun, the first controllable switch (5) is closed and the network termination unit (55) is switched from a normal operating state to a remotely supplied state, which preferably represents an emergency operating state.

9. Method for transferring a network termination unit from a normal operating state to a remotely supplied state by using a switching circuit according to claim 2, characterized in that the amplitude of the local supply voltage is continuously measured and compared with a predetermined minimum value, and that when the predetermined minimum value is underrun, the second controllable switch (4) is closed and the network termination unit (55) is switched from a normal operating state to the remotely supplied state, which preferably represents an emergency operating state, wherein during the switching time the charge stored in the buffer capacitor (3) is at least partially supplied to the primary winding (1) of the transformer, and that thereafter the first controllable switch (5) is closed.

10. Method according to claim 8 or 9, characterized in that the remote supply voltage is decreased in the normal operating state to a predetermined value and increased to its full value, when the local power supply voltage source (41) fails or has an insufficient voltage or for recharging the buffer capacitor (3).

11. Method according to claim 8, 9 or 10, characterized in that the subscriber line (30) is forcibly switched for maintenance and test operations into the emergency operating state and thereafter returned again to the normal operating state.