OSSD Voltage Comparison Fault Detection
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Solution Overview
Problem
Existing Output Signal Switching Devices (OSSDs) require significant firmware efforts and complex components to detect output faults using test pulses, which can lead to distorted signals and erroneous fault detection due to high resistive and capacitive loads.
Innovation Solution
The OSSD employs three different voltages (supply voltage, first voltage, and second voltage) to compare and detect faults, eliminating the need for test pulses by switching off output terminals if their voltage exceeds expected levels, thereby simplifying the device and reducing firmware complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test pulses are used to detect output faults, then fault detection capability is improved, but firmware complexity and device complexity increase significantly
Solution Approach 1:
The patent extracts the fault detection function from the complex test pulse generation and monitoring system, implementing it instead through a simple voltage comparison mechanism using voltage dividing means. This removes the need for complex firmware to generate and monitor test pulses, while maintaining reliable fault detection capability.
Solution Approach 2:
The patent changes the detection parameter from time-domain test pulses to voltage-level comparison. By using voltage dividing means to create different voltage levels and comparing these against threshold values, the system achieves fault detection through parameter change rather than through complex temporal pulse sequences.
2Reliability
If test pulses are applied to output terminals, then output faults can be detected, but signal distortion and erroneous fault detection occur due to high resistive and capacitive loads
Solution Approach 1:
Instead of applying full-strength test pulses that may cause signal distortion, the patent uses a partial action approach by continuously maintaining different voltage levels through voltage dividing means. This allows fault detection without the excessive action of strong test pulses that distort signals under high load conditions.
Solution Approach 2:
The patent performs preliminary action by pre-establishing different voltage levels at the output terminals through voltage dividing means before any fault occurs. This eliminates the need for subsequent test pulse application, thereby preventing signal distortion that would occur during active testing.
3Ease of operation
If low-side switches are used to generate test pulses, then output terminals can be switched to low level, but dead time and switching complexity are introduced
Solution Approach 1:
The patent replaces the mechanical/electronic switching system (low-side switches) with a passive voltage dividing network. This substitution eliminates the need for active switching components and their associated dead times, while maintaining the ability to provide different voltage levels at output terminals for fault detection.
4Reliability
If test pulses are used for fault detection, then output faults can be identified, but resistive and capacitive loads must be limited which reduces adaptability
Solution Approach 1:
The patent implements a universal voltage dividing network that can work with any resistive or capacitive load without requiring load limitations. The voltage comparison mechanism is universally applicable regardless of load characteristics, thereby increasing adaptability while maintaining fault detection capability.
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 cost-effective manufacturing with reduced firmware complexity, wider application scope, and reliable fault detection without the limitations of test pulses, meeting Safety Integrity Level 3 requirements.
Implementation Method 1
first voltage reducing means, preferably connected to a supply voltage, that are adapted to reduce the supply voltage to a first voltage which is lower in magnitude than the supply voltage, second voltage reducing means, preferably connected to the supply voltage, that are adapted to reduce the supply voltage to a second voltage which is lower in magnitude than the first voltage
Data Source
Figure 1
AI summary
The invention relates to an Output Signal Switching Device (OSSD) having at least one pair of electric output terminals, the pair of electric output terminals comprises a first output terminal and a second output terminal. The OSSD further comprises first voltage reducing means providing a first voltage which is lower in magnitude than a supply voltage, second voltage reducing means providing a second voltage which is lower in magnitude than the first voltage, wherein the second voltage is applied to the first output terminal and the first voltage is applied to the second output terminal, and wherein switching means are provided which are adapted to separate the second voltage from the first output terminal and/or the first voltage from the second output terminal, if the magnitude of the voltage at the second output terminal is equal to or higher than the magnitude of the supply voltage and/or if the magnitude of the voltage at the first output terminal is equal to or higher than the magnitude of the first voltage.