Shared Positive Overvoltage Protector for Subscriber Line Interface Circuits
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Solution Overview
Problem
Conventional dual protector protection schemes for subscriber line interface circuits are costly due to the need for multiple overvoltage protectors and gate capacitors, and can disrupt service across all channels when a fault occurs on one channel.
Innovation Solution
A line card with a shared positive overvoltage protector referenced to the VBP supply, coupled with individual negative overvoltage protectors referenced to the VBH supply, and a power sink to manage surges, reducing the number of protectors and gate capacitors required while minimizing service disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual protector protection schemes are used for each interface line, then overvoltage protection is provided, but cost and device complexity increase due to requiring multiple protectors and gate capacitors
Solution Approach 1:
The patent combines multiple positive overvoltage protectors into a single shared protector that serves multiple interface lines. The shared positive overvoltage protector is coupled to receive interface lines from multiple subscriber line interface circuits and provides overvoltage protection for all of them simultaneously, eliminating the need for separate protectors for each line.
Solution Approach 2:
The shared positive overvoltage protector is designed to perform multiple functions by protecting multiple interface lines across different subscriber line interface circuits. This universal protector handles overvoltage events on any of the connected interface lines, making a single device serve the role of multiple protectors.
2Reliability
If dual protector protection schemes are used for each interface line, then overvoltage protection is provided, but real estate on the line card increases
Solution Approach 1:
The patent merges multiple protection functions into a single shared positive overvoltage protector device, significantly reducing the physical space required on the line card. Instead of having separate protectors and gate capacitors for each interface line, one shared protector serves multiple lines, reducing component count and board real estate.
3Reliability
If individual protectors are used for each interface line, then protection is provided, but service disruption occurs across all channels when a fault occurs on one channel
Solution Approach 1:
The patent segments the protection scheme into individual negative overvoltage protectors for each interface line while using a shared positive overvoltage protector. This segmentation allows faults to be isolated to individual lines through the negative protectors, preventing cascading failures across all channels while maintaining the benefits of shared positive protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces the cost and real estate needed for the line card by sharing positive overvoltage protection across multiple interface lines, minimizing service disruptions, and maintaining continuous operation during surges and power cross events.
Implementation Method 1
a first positive overvoltage protector coupled to the interface lines, shared across the subscriber line interface circuits, and referenced to the first positive reference voltage to provide overvoltage protection responsive to a voltage on at least one of the interface lines exceeding the first positive reference voltage
Implementation Method 2
Gate capacitors 125, 135 are provided at the gate inputs of the protectors 120, 130 for maintaining the reference voltage for the protectors 120, 130 during transients
Implementation Method 3
The negative overvoltage protector 120 initially clips overvoltages close to the VBH value. If sufficient current is available from the overvoltage, then the negative overvoltage protector 120 will crowbar into a low voltage ground referenced on-state condition
Implementation Method 4
Similarly, the positive overvoltage protector 130 initially clips positive overvoltages close to the VBP value. If sufficient current is available from the overvoltage, then the positive overvoltage protector 130 will crowbar into a low voltage ground referenced on-state condition
Implementation Method 5
During an overvoltage transient, increased current may pass through the protection resistors 110, which are positive coefficient devices, causing them to tri-state and thereby isolate the associated interface line 105
Data Source
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AI summary
A line card includes a plurality of subscriber line interface circuits, a plurality of interface lines, and a first overvoltage protector. The subscriber line interface circuits each have a first input terminal operable to receive power at a first positive reference voltage. The interface lines are each coupled to one of the subscriber line interface circuits for interfacing with subscriber lines external to the line card. The first overvoltage protector is coupled to the interface lines and referenced to the first positive reference voltage to provide overvoltage protection responsive to a voltage on at least one of the interface lines exceeding the first positive reference voltage.