Air Core Transformer for Wired Communication Isolation
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Solution Overview
Problem
Wired communication systems with ferrite transformers face issues due to high parasitic capacitance, which leads to high current during bulk current injection tests, requiring additional ESD protection and increasing the bulk and cost of the system.
Innovation Solution
The use of air core transformers with a termination resistance equal to the characteristic impedance of the transmission line, and a comparator or driver circuit configured to provide output signals responsive to voltage pulses, reducing parasitic capacitance and impedance, thereby minimizing reflections and enhancing galvanic isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite transformers are used for galvanic isolation, then galvanic isolation is achieved, but parasitic capacitance increases leading to high current during BCI tests
Solution Approach 1:
The patent extracts the harmful parasitic capacitance by replacing the ferrite transformer with an air core transformer. This removal of the ferrite core material eliminates the source of parasitic capacitance while preserving the galvanic isolation function through the air-cored transformer design, directly resolving the contradiction between achieving isolation and avoiding harmful capacitance.
Solution Approach 2:
The patent changes the physical parameter of the transformer core from ferrite material to air core. This parameter change fundamentally alters the electrical characteristics, reducing parasitic capacitance from around 80 pF to negligible levels, while maintaining the transformer's galvanic isolation capability and transforming the signal.
2Power
If ferrite transformers with high parasitic capacitance are used, then signal transformation is achieved, but additional ESD protection components are required increasing system bulk
Solution Approach 1:
The patent removes the need for additional ESD protection components by eliminating the high parasitic capacitance source. The air core transformer inherently provides low capacitance operation, making separate ESD protection circuitry unnecessary, thus reducing system bulk and component count while maintaining signal transformation capability.
3Reliability
If ferrite transformers are used, then galvanic isolation is provided, but cost increases due to additional protection requirements
Solution Approach 1:
The patent extracts the cost burden by eliminating additional ESD protection components. The air core transformer design inherently satisfies both galvanic isolation and low capacitance requirements, removing the need for extra protection components and their associated costs, thereby reducing overall system manufacturing cost while maintaining reliability.
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 reduces parasitic capacitance, lowers impedance, and minimizes reflections, resulting in a more compact, cost-effective, and efficient wired communication system with improved galvanic isolation.
Implementation Method 1
an air core transformer having an input coil connected to the pair of input connections via the termination resistance; and a comparator circuit connected to an output coil of the air core transformer
Implementation Method 2
a termination resistance equal to a characteristic impedance of the transmission line
Data Source
AI summary
The disclosure relates to a communications system having a transmitter and receiver connected via a transmission line. An example communications receiver (202) comprises: a pair of input connections (211, 212) for connecting to a transmission line (203); a termination resistance (213) equal to a characteristic impedance (Zc) of the transmission line (203); an air core transformer (205) having an input coil (206) connected to the pair of input connections (211, 212) via the termination resistance (213); and a comparator circuit (208) connected to an output coil (207) of the air core transformer (205), the comparator circuit (208) configured to provide an output signal (504) responsive to detection of voltage pulses across the output coil (207).