Intrinsically Safe Galvanic Barrier Using Segmented Isolation
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Solution Overview
Problem
Conventional galvanically isolated barriers operate at insufficient data rates and are costly, limiting their flexibility and efficiency in modern process control systems, particularly in hazardous environments where intrinsic safety standards must be met.
Innovation Solution
A two-stage approach using a non-galvanically isolated IS barrier and a galvanic isolator, where the galvanic isolator is implemented as a monolithic digital isolator to provide high-speed data transfer while ensuring intrinsic safety standards are met, allowing for a high-speed, low-cost galvanically isolated barrier between non-IS and IS circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional galvanically isolated barriers use optical couplers, then intrinsic safety is ensured, but data transmission rate is limited to approximately 20 kbits/second
Solution Approach 1:
The barrier device is divided into two independent stages: a non-IS side with energy limiting components (fuse, diodes, resistors) and an IS side with galvanic isolation (transformer). This segmentation allows each stage to be optimized independently - the first stage for energy limitation and the second for high-speed isolation, resolving the contradiction between speed and safety certification.
Solution Approach 2:
A coupling capacitor is introduced as an intermediary between the energy limiting stage and the galvanic isolation stage. This capacitor enables high-frequency signal transmission while blocking DC components, allowing the system to achieve both intrinsic safety certification and high data transmission rates by mediating between the two conflicting requirements.
2Adaptability or versatility
If non-galvanically isolated barriers are used, then cost is reduced, but system flexibility is limited due to grounding requirements
Solution Approach 1:
The transformer acts as a galvanic isolation intermediary that eliminates the need for safety grounding while maintaining intrinsic safety. This allows the system to achieve both system flexibility (no grounding constraints) and cost-effectiveness by replacing expensive isolated power supplies with a simpler transformer-based isolation stage.
Solution Approach 2:
The patent replaces the mechanical/physical grounding connection required by non-galvanic barriers with an electromagnetic field-based isolation mechanism using a transformer. This substitution eliminates the need for physical ground connections while maintaining safety, thereby improving system flexibility without proportionally increasing cost.
3Speed
If monolithic integrated circuit isolation devices are used, then data transmission rate increases to greater than 10 Megabits/second, but the devices do not meet intrinsic safety standards due to internal spacing less than 0.5 mm
Solution Approach 1:
The system segments the isolation function into two parts: a transformer for galvanic isolation (which can accommodate larger physical spacing for safety compliance) and a coupling capacitor for high-frequency signal transmission. This segmentation allows the use of high-speed components while meeting intrinsic safety spacing requirements through the transformer's physical isolation.
Solution Approach 2:
The patent changes the operating parameters by using a transformer with sufficient winding spacing to meet the 0.5 mm intrinsic safety requirement, rather than using integrated circuit isolators with fixed internal spacing. This parameter change allows compliance with safety standards while maintaining high data transmission rates through the transformer-coupled architecture.
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 enables high-speed data transmission while adhering to intrinsic safety standards, enhancing system flexibility and reducing costs by utilizing a monolithic digital isolator in conjunction with a diode barrier to create an intrinsically safe galvanically isolated communication bus for process control systems.
Implementation Method 1
non-galvanically isolated barriers limit or shunt the available energy from a non-IS system down to levels which are considered safe under IS standards
Implementation Method 2
galvanically isolated barriers rely on optical coupling, which is inherently slow when compared to state of the art data rates
Implementation Method 3
Monolithic integrated circuit isolation devices have been developed that transfer data at rates of greater than 10 Megabits/second through miniature monolithic transformers or capacitors using modulation techniques
Implementation Method 4
a coupling capacitor to block DC components and allow AC signal transmission
Data Source
AI summary
A system and method for providing an intrinsically safe (IS) galvanically isolated barrier device. An IS barrier device provides IS galvanic isolation between a non-IS system and an IS system using a two-stage approach. In the first stage, a non-galvanically isolated IS barrier limits energy of electrical transmissions received from the non-IS system to convert such electrical transmissions into IS transmissions. In the second stage, the IS transmissions are transmitted through a galvanic isolator to the IS system to galvanically isolate the IS system from the non-IS system. A digital monolithic isolator cannot be IS certified to be the single bridge between IS and non-IS systems, however, it can be used in a certifiable fashion to isolate between IS systems. When used in conjunction with a non-galvanic IS barrier that is capable meeting the IS certification as non-IS to IS barrier, a digital monolithic isolator can be used to implement the galvanic isolator such that high speed, low cost galvanic isolation is possible. Such a galvanically isolated barrier device can be used to implement an IS galvanically isolated high speed communication bus for sample system control.