Current Supervisory Circuit Using Modulated Overcurrent Reporting
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Solution Overview
Problem
Existing current sensors in electrical systems face challenges in reliably detecting and reporting overcurrent events, particularly due to electromagnetic interference and inability to diagnose failures in overcurrent reporting units.
Innovation Solution
A current supervisory device that uses a processing circuit to generate a modulated signal for reporting overcurrent events, with modulation parameters such as pulse width and frequency, allowing for reliable event detection and reporting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a digital output signal is used to report overcurrent events, then the reporting is simple and clear, but the system becomes vulnerable to electromagnetic interference and cannot diagnose reporting unit failures
Solution Approach 1:
The patent introduces a modulated carrier signal as an intermediary between the event detection and the output reporting. The event signal modulates the carrier signal, creating a composite signal that carries event information while being less susceptible to electromagnetic interference. This intermediary approach allows reliable transmission of event status without directly exposing the simple digital output to interference vulnerabilities.
Solution Approach 2:
The patent changes the parameter representation of event information by encoding it in the modulation parameters (frequency, amplitude, or phase) of a carrier signal rather than using direct digital levels. This parameter encoding allows the system to distinguish between actual events and noise, and enables failure diagnosis by monitoring the presence and characteristics of the modulated signal.
2Device complexity
If a simple digital output is used for event reporting, then the device complexity is low, but the ability to diagnose failures in the reporting unit is lost
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the modulated output signal characteristics. By analyzing the presence, frequency, and quality of the modulated carrier signal, the system can determine whether the reporting unit is functioning correctly. This feedback loop provides failure diagnosis capability while maintaining relatively simple circuitry through the use of standard modulation and detection components.
3Reliability
If electromagnetic interference protection is enhanced through modulation, then the event reporting reliability improves, but the device complexity increases
Solution Approach 1:
The patent employs a universal modulation approach where a single modulated carrier signal serves multiple functions: it reports event status, provides electromagnetic interference immunity, and enables failure diagnosis. This multi-functionality reduces the need for separate dedicated circuits for each purpose, thereby limiting the increase in device complexity while achieving improved reliability through modulation.
Data Source
AI summary
A current supervisory device includes current sensing means for sensing a current; a circuit arranged to convert a signal received from the current sensing means into a signal indicative of the sensed current; a processing circuit arranged to receive the signal indicative of the sensed current, to detect an event based on the received signal such that the detecting yields an outcome corresponding to one of at least two different states, and to generate an event signal in accordance with the outcome, such that the processing circuit has modulation means for performing modulation based on the event signal; and an output terminal arranged to output a reporting signal received from said processing circuit, whereby at least one of at least two different states gives rise to the reporting signal being a modulated signal.