Capacitive Signal Transfer Assembly for Fast Safe Data Links
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Solution Overview
Problem
Existing safe communications channels in functional safety applications often face a trade-off between ensuring safety and achieving fast data transfer rates, as measures to limit electrical energy during faults can negatively impact data transfer speeds.
Innovation Solution
The proposed solution involves a signal transfer assembly with a series connection of at least two capacitors connected in parallel to an ohmic resistor in the communications channel, which raises the filter cut-off frequency of the low-pass filter, thereby reducing the low-pass effect and increasing the bandwidth of the communications channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ohmic resistors are connected in series in the communications channel to limit electrical energy during faults, then safety is improved, but data transfer rates deteriorate due to the low-pass filtering effect
Solution Approach 1:
The patent changes the electrical parameters of the communications channel by adding capacitors in parallel to the series resistor. This modifies the filter cut-off frequency parameter, raising it from a value that attenuated fast signals to a value above the highest signal frequency, thereby enabling fast data transfer while maintaining the safety function of the series resistor
Solution Approach 2:
The patent creates a composite filtering structure by combining resistive and capacitive elements. The series resistor and parallel capacitor form an RC circuit with specific time constant characteristics that allow both safety energy limiting and fast signal passage, effectively creating a hybrid safety-speed communication channel
2Object-affected harmful factors
If the filter cut-off frequency is kept low to ensure safety through energy limiting, then fault protection is improved, but signal attenuation occurs for fast signals with frequencies above the cut-off
Solution Approach 1:
The patent directly addresses the cut-off frequency parameter by adding parallel capacitance, which increases the time constant (τ = RC) and consequently raises the cut-off frequency (f_c = 1/(2πRC)). This parameter change ensures that fast signals with frequencies up to and exceeding the original cut-off frequency are no longer attenuated, while the series resistor continues to limit fault energy
Solution Approach 2:
The capacitor acts as an intermediary element that mediates between the safety requirement (energy limiting by resistor) and the speed requirement (fast signal transmission). The capacitor provides a high-frequency path that bypasses the resistor's low-pass filtering effect, allowing fast signals to pass while the resistor maintains its protective function for lower frequency fault conditions
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 allows for higher data transfer speeds and the transfer of faster signals without loss of information, while maintaining safety by ensuring that the filter cut-off frequency is above the frequencies of all information-carrying signal components, thus preventing attenuation.
Implementation Method 1
Signal transfer assembly with capacitive coupling
Implementation Method 2
The at least one ohmic resistor of the communications channel with the signal sink input capacitance of the signal sink forms a low-pass filter with a filter cut-off frequency
Data Source
AI summary
A signal transfer assembly has a signal source with a signal source output, a signal sink with a signal sink input, having a signal sink input capacitance, and a communications channel connecting the signal source output to the signal sink input, where the communications channel has a first signal terminal for connecting the signal source output, a second signal terminal for connecting the signal sink input, and at least one ohmic resistor, connected in series between the first signal terminal and the second signal terminal, in order to transfer a source signal into a sink signal, a series connection of at least two capacitors is connected into the communications channel, between the first signal terminal and the second signal terminal and parallel to the at least one ohmic resistor.