Safety Switching Device Galvanic Isolation Segmentation
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Solution Overview
Problem
Existing safety switching devices for fail-safe shutdowns of technical systems require expensive and space-consuming galvanically isolated coupling elements for redundancy and error detection, which are prone to high failure rates and do not effectively detect all errors.
Innovation Solution
A safety switching device with input circuits divided into two galvanically isolated areas, each with a separate test device, reducing the need for coupling elements and enabling effective two-stage testing for error detection and redundancy, while ensuring correct detection of the OFF state and minimizing physical size and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanically isolated coupling elements are used for redundant input channels, then safety function is maintained, but cost and device complexity increase significantly
Solution Approach 1:
The input circuit is divided into two galvanically isolated areas (first area with first input circuit, second area with second input circuit), each capable of independent operation. This segmentation allows redundancy without requiring multiple coupling elements between channels, as each area processes its input independently and the isolation is built into the area boundaries rather than requiring separate coupling components.
Solution Approach 2:
The patent combines the galvanic isolation function with the circuit area division itself, rather than using separate coupling elements. The isolation barrier is integrated into the architecture where the first and second areas are galvanically isolated from each other, eliminating the need for additional coupling components while maintaining the required isolation.
2Reliability
If multiple coupling elements are used for test circuits, then galvanic isolation is ensured, but production costs and space requirements increase
Solution Approach 1:
The test circuit is divided into a first test circuit in the first area and a second test circuit in the second area, with each operating independently within its galvanically isolated area. This segmentation allows each test circuit to function without requiring isolation coupling elements to the other area, reducing the total number of coupling elements needed.
Solution Approach 2:
The patent uses a shared test signal line that crosses the galvanic isolation boundary without requiring a coupling element. The test signal is injected in a controlled manner through the isolation barrier, serving as an intermediary that allows testing across areas without the need for additional isolating components.
3Measurement precision
If redundant input channels are implemented, then fault detection capability is improved, but the number of components and physical size increase
Solution Approach 1:
The circuit is segmented into two compact galvanically isolated areas, each containing its own input circuit and test circuit. This segmentation allows for efficient space utilization where each area is minimized in size, and the overall device footprint is reduced compared to designs that use separate coupling elements for each redundant channel.
Solution Approach 2:
The patent merges multiple functions into the shared components: the shared evaluation circuit performs evaluation for both input channels, the shared test signal line serves both test circuits, and the galvanic isolation structure provides both channel separation and test signal pathways. This functional merging reduces the total component count and physical size.
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 number of required components, improves error detection, and ensures reliable fail-safe shutdowns with reduced costs and space requirements, while maintaining safety functions even in the presence of single errors.
Implementation Method 1
the first and the second input circuits are divided into a first and a second circuit which are galvanically isolated from each other
Implementation Method 2
The input circuit has four optocouplers
Data Source
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AI summary
The invention relates to a safety switching device (10) for deactivating a technical system (12) in a failsafe manner, comprising a first and at least one second input (30, 30'). The first input (30) receives a first input signal (38) by means of a first input circuit (32), and the second input (30') receives a second input signal (38') by means of a second input circuit. The first and second input circuit are divided into a first (I) and a second circuit (II) which are galvanically separated from each other. A first signal input circuit (40), a first threshold element (44), and a first coupling element (42) of the first input circuit (32) as well as a second signal input circuit (40'), a second threshold element (44'), and a second coupling element (42') of the second input circuit are arranged in the first circuit (I). The first circuit (I) further has a first testing device (46) with a third coupling element (48), the first testing device (46) being designed to interrupt a current path from the first and second threshold element (44, 44') to a ground terminal (64). A second testing device (52) and a first discharge circuit (54) of the first input (30) and a third testing device (52') and a second discharge circuit (54') of the second input are arranged in the second circuit (II), said first, second, and third coupling element (42, 42', 48) connecting the first and second circuit (I, II) to each other. (Fig. 1)