Isolating Transformer Grounding Circuit for EMI Noise Saturation
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Solution Overview
Problem
Existing signal isolation technologies, such as isolating transformers, are affected by external electric fields like electromagnetic interference (EMI), leading to noise-induced common mode voltages that can saturate the transformer and prevent accurate signal transmission.
Innovation Solution
The implementation of a grounding circuit that temporarily grounds the transmitting coil of the isolating transformer based on the value of an input signal, reducing the time available for noise-induced voltage buildup, thereby mitigating radiated noise and maintaining data transmission capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolating transformer is used for signal isolation, then signal transmission between isolated portions is enabled, but noise-induced common mode voltage causes transformer saturation and prevents accurate signal transmission
Solution Approach 1:
The grounding circuit proactively grounds the transformer coil before noise-induced voltage can build up to saturation levels. By detecting the input signal state and preemptively establishing a ground reference, the system prevents the harmful common mode voltage from reaching problematic levels, thereby maintaining signal transmission accuracy.
Solution Approach 2:
The grounding circuit acts as an intermediary between the isolating transformer and the ground terminal. It selectively couples or decouples the transformer coil to ground based on signal conditions, mediating the interaction to prevent harmful voltage buildup while maintaining isolation functionality when needed.
2Object-affected harmful factors
If the transformer coil is continuously grounded, then common mode voltage is reduced, but data transmission capability is lost
Solution Approach 1:
The grounding circuit employs periodic rather than continuous grounding, switching between grounded and floating states based on the input signal. During periods when grounding is active, common mode voltage is reduced; during periods when grounding is released, data transmission occurs. This periodic alternation resolves the contradiction by providing both protections at different times.
Solution Approach 2:
The grounding circuit dynamically adjusts its state based on real-time signal conditions. It transitions from a static continuously-grounded configuration to a dynamic system that couples to ground when noise is present and decouples when data transmission is required, optimizing both protection and functionality.
3Loss of information
If grounding is released immediately when signal is asserted, then data transmission is enabled, but noise-induced voltage can rebuild up quickly
Solution Approach 1:
The grounding circuit maintains ground coupling for a programmed period after signal assertion to preemptively prevent noise-induced voltage from rebuilding up. This extended grounding period acts as a preventive measure, ensuring that even after data transmission begins, the transformer remains protected from rapid voltage buildup that could occur if grounding were released immediately.
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 approach reduces the peak-to-peak value of common mode voltage by approximately twenty percent, preventing saturation of the isolating transformer and ensuring accurate signal transmission and detection.
Implementation Method 1
The isolating transformer has first and second coils separated by an isolation barrier
Implementation Method 2
The first resistor has first and second terminals, the first terminal of the first resistor coupled to the first terminal of the first coil
Data Source
AI summary
In some examples, an apparatus includes an isolating transformer and a grounding circuit. The isolating transformer has first and second coils separated by an isolation barrier, the first coil having first and second terminals. The grounding circuit is coupled to the first and second terminals. The grounding circuit is configured to couple the first and second terminals to a ground terminal during a first time period. The grounding circuit is also configured to decouple the first and second terminals from the ground terminal during a second time period.