Backup Tripping Circuit for Microcontroller-Based Circuit Breakers
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Solution Overview
Problem
Microcontroller-based circuit breakers may fail to detect faults if the power supply regulator or the microcontroller itself is faulty, leaving the connected load unprotected.
Innovation Solution
The implementation of backup timing circuits that ensure the circuit breaker trips even if the microcontroller is unresponsive, either due to a power supply failure or a microcontroller fault, by using separate power supplies and configurations that bypass the microcontroller to activate the tripping mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microcontroller-based fault detection system is implemented in a circuit breaker, then fault detection capability is improved, but reliability deteriorates because the microcontroller or power supply regulator may fail, leaving the circuit unprotected
Solution Approach 1:
The system is divided into two independent fault detection paths: a microcontroller-based electronic detection path and a traditional backup tripping path. The backup path uses a separate power supply and timing circuit that operates independently of the microcontroller, ensuring that if the microcontroller fails, the backup path can still detect faults and trip the circuit breaker.
Solution Approach 2:
A backup timing circuit is pre-configured with a separate power supply that will automatically activate if the microcontroller fails. This backup system is prepared in advance to take over fault detection and tripping functions, cushioning against the failure of the primary microcontroller-based system.
2Reliability
If a backup timing circuit with separate power supply is added, then reliability is improved, but device complexity increases
Solution Approach 1:
The backup timing circuit is extracted as a separate, self-contained subsystem with its own power supply, timing components, and tripping mechanism. This modular approach allows the backup system to be added without fundamentally redesigning the entire circuit breaker, minimizing the increase in overall complexity while ensuring reliability.
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
Ensures the circuit breaker trips promptly to protect the load from electrical faults, even if the microcontroller fails to start up or if its power supply is unresponsive, thereby maintaining safety and reliability.
Implementation Method 1
the node can build up a voltage across a capacitor that eventually becomes sufficient to energize the transistor
Implementation Method 2
the transistor whose gate is charged by a node that is also connected to a configurable pin of the microcontroller
Data Source
AI summary
A circuit breaker capable of microcontroller-based fault detection having a backup circuit for causing the circuit to trip in response to a microcontroller fault or a failure of a regulated power supply powering the microcontroller. The circuit breaker includes an RC circuit connected to an SCR. The resistor of the RC circuit is connected between the anode and gate of the SCR, and the capacitor is connected between the gate and cathode of the SCR. The microcontroller has a first pin coupled to the RC circuit, which is initially in a high input impedance state. In the event of a microcontroller fault or power supply failure, the capacitor will charge to a voltage sufficient to activate the SCR and trip the breaker. If the microcontroller startup routine is successful, the pin is configured as an output and is pulled low, shorting out the capacitor.