Programmable Current Sink Circuit for Industrial Relay Contacts
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Solution Overview
Problem
Existing digital input/output systems, particularly in industrial applications, face challenges with relay contact contamination leading to increased contact resistance and signal loss due to oxidation, and conventional current sinks have limited capability, requiring active circuitry in redundant configurations.
Innovation Solution
A programmable current sink circuit with a digital-to-analog converter (DAC) that sets an adjustable magnitude of current sink, allowing multiple inputs to share current and operate in both current sink and band pass filter modes, using a single metal oxide field effect transistor (MOSFET) without multiplexors or switches, enabling diagnostic measurement of sink current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sinks are used in redundant configurations, then reliability is improved, but device complexity increases due to requirement of active circuitry
Solution Approach 1:
The patent combines multiple current sink functions into a single integrated circuit that can handle redundant configurations (dual, TMR, or simplex inputs) internally. This merging eliminates the need for separate active circuitry in redundant setups, as the single chip provides both the current sinking capability and the redundancy management, thereby improving reliability without increasing device complexity.
Solution Approach 2:
The current sink circuit is designed with universal functionality to support multiple operating modes (dual input, TMR, simplex) within a single device. This multi-functionality allows the same circuit to adapt to different redundancy configurations without requiring additional active components, resolving the contradiction between reliability improvement through redundancy and device complexity reduction.
2Ease of manufacture
If fixed current sink capability is provided, then ease of manufacture is improved, but adaptability deteriorates due to inability to adjust current magnitude
Solution Approach 1:
The patent implements a dynamic current sink capability where the current magnitude can be adjusted based on operational requirements. The circuit includes control logic that allows the current sink value to be modified programmatically or through external control, enabling the same manufactured device to adapt to different current requirements without requiring different hardware configurations, thus maintaining ease of manufacture while improving adaptability.
Solution Approach 2:
The current sink circuit allows change of the current parameter (magnitude) through programmable control or external adjustment mechanisms. This parameter variability enables a single manufactured device to serve multiple applications with different current requirements, resolving the contradiction between ease of manufacture (fixed design) and adaptability (variable requirements).
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 programmable current sink circuit effectively minimizes oxidation, maintains reliable contact operation, and supports redundant configurations without active circuitry, enhancing reliability and diagnostic capabilities in industrial control systems.
Implementation Method 1
a digital-to-analog converter (DAC) that sets an adjustable magnitude of current sink
Implementation Method 2
using a single metal oxide field effect transistor (MOSFET)
Data Source
AI summary
A system and method according to various embodiments can include a programmable current sink circuit that comprises a digital-to-analog converter (DAC). The DAC is programmable to set an adjustable magnitude of current sink so that a proper amount of current is jointly sunk from a plurality of inputs to generate a total sink current. With the adjustable current sink, redundant inputs, such as dual modular redundancy or triple modular redundancy, or simplex inputs can jointly sink the proper amount of current.