Ethernet Interface Circuit Preventing Common-Mode to Differential Mode Over-Voltage Conversion
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Solution Overview
Problem
Current Ethernet port protection circuits convert common-mode over-voltage into differential mode over-voltage due to potential differences between signal lines, damaging Ethernet chips.
Innovation Solution
An interface circuit comprising a transformer unit, a protection unit, and an interface unit, where the protection unit is connected to the center tap of the transformer unit and grounded, ensuring that all signal lines are clamped to a low voltage during surge conditions, preventing differential mode over-voltage conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a gas discharge tube is connected with a center tap of the transformer unit to clamp over-voltage on signal lines 1, 2, 3, and 6, then the over-voltage on these signal lines is reduced to low voltage, but the idle signal lines 4, 5, 7, and 8 remain at high voltage and discharge to the active signal lines, converting common-mode over-voltage into differential mode over-voltage that damages the Ethernet chip
Solution Approach 1:
The protection circuit is divided into two independent parts: one for active signal lines (1, 2, 3, 6) using a gas discharge tube connected to the transformer center tap, and another for idle signal lines (4, 5, 7, 8) using a Bob-smith circuit with insulation and withstand voltage. This segmentation allows each part to be optimized independently, preventing the idle lines from discharging to active lines and converting common-mode over-voltage into differential mode over-voltage.
Solution Approach 2:
The Bob-smith circuit acts as an intermediary protection mechanism for idle signal lines 4, 5, 7, and 8. It provides insulation and withstand voltage to prevent these idle lines from discharging to the active signal lines during over-voltage events, thereby preventing the conversion of common-mode over-voltage into differential mode over-voltage that would damage the Ethernet chip.
2Strength
If idle signal lines 4, 5, 7, and 8 are connected with a Bob-smith circuit to withstand over-voltage through insulation, then insulation protection is provided, but the signal lines still discharge to each other at the modular plug during surge voltage, causing common-mode to differential mode conversion
Solution Approach 1:
The Bob-smith circuit is designed with insulation and withstand voltage capabilities before over-voltage events occur. This preliminary protective measure creates a barrier that prevents idle signal lines from discharging to active signal lines during surge conditions, thereby preventing the harmful conversion of common-mode over-voltage into differential mode over-voltage at the modular plug.
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
This configuration enhances systemic protection performance and improves the reliability of Ethernet devices by eliminating the conversion of common-mode over-voltage to differential mode over-voltage, thereby safeguarding the Ethernet chip.
Implementation Method 1
a transformer unit and a network port (RJ45 interface) that are connected with an Ethernet chip. Signal lines 1 and 2 of the network port are electrically connected with a receiving terminal of the transformer unit, signal lines 3 and 6 are connected with a sending terminal of the transformer unit
Implementation Method 2
An over-voltage of the signal lines 1, 2, 3, and 6 of the network port (RJ45 interface) is discharged through a gas discharge tube connected with a center tap of the transformer unit
Data Source
AI summary
An interface circuit and a communication device are provided. The interface circuit includes a transformer unit, a protection unit, and an interface unit. A secondary side of the transformer unit is connected with a chip. A first terminal of the protection unit is electrically connected with a center tap of a primary side of the transformer unit, and a second terminal of the protection unit is grounded. A first access terminal of the interface unit is connected with a first port of the primary side of the transformer unit, a second access terminal of the interface unit is connected with a second port of the primary side of the transformer unit, and a third access terminal and a fourth access terminal of the interface unit are electrically connected with the first terminal of the protection unit respectively.