Safety Mechanisms for Power Supply
In this post, we will learn about Safety Mechanisms used in Power Supply. The Safety Mechanisms described in this post are based on ISO 26262-5:2018 Annex D.
D.2.6.1 Voltage or current control (input)
Voltage or Current Control is a technique used in functional safety systems to monitor the behavior of input voltage or current. This technique aims to detect anomalies in input signals as soon as possible to prevent incorrect system behavior and maintain operational safety. By continuously monitoring electrical inputs, systems can quickly identify and respond to potential failures, ensuring that all components operate within their specified parameters.
Aim
- Detection of input current or voltage anomalies: Maintains the safety and reliability of the system by detecting incorrect input current or voltage values as soon as possible.
Description
- Monitoring input voltage and current:
- Continuous monitoring: Continuously monitors the input voltage or current of the system to detect signals that are out of the normal range.
- Anomalous detection: Detects abnormal behavior of input signals (e.g. overvoltage, undervoltage, overcurrent, undercurrent).
- Fault Detection and Response:
- Immediate Response: Issues an alarm immediately when an abnormal signal is detected and takes protective measures as needed.
- System Protection: Implements protective mechanisms designed to minimize the risk of damage to system components or malfunctions.
Examples
Example 1: Voltage Monitoring in Automotive Electrical Systems
- Configuration: Detects electrical errors by monitoring the input voltage in the automotive electrical system.
- Operation Principle:
- Continuously monitors the voltage of the car battery to detect overvoltage or undervoltage conditions.
- If the voltage is out of the acceptable range, the system issues an alarm and activates the power cutoff device as needed.
- Advantages:
- Improves the electrical reliability of the electrical system and prevents damage due to voltage abnormalities.
Example 2: Current Monitoring in Industrial Control Systems
- Configuration: Monitors the input current in industrial control systems to detect abnormal current flow.
- Operation Principle:
- Continuously measures the input current to detect overcurrent or undercurrent conditions. – When an abnormal condition is detected, the system issues a warning and automatically cuts off the current to protect the equipment.
- Advantages:
- It improves the electrical safety of the equipment and prevents malfunctions caused by abnormal current.
Limitations and Challenges
1. Sensor Limitations
- Sensor Accuracy: The accuracy and response time of the sensor can directly affect the system’s ability to detect errors.
2. Increased Design Complexity
- Complex Signal Processing: The implementation of a real-time monitoring and processing system for various input signals can be complex.
3. Performance Overhead
- Additional Computational Requirements: Performance overhead may occur due to input signal monitoring, which should be minimized through optimization.
D.2.6.2 Voltage or current control (output)
Voltage or Current Control (Output) is a technique designed to monitor the behavior of output voltage and current values in safety-critical systems. By continuously tracking these electrical parameters, the system can promptly detect any anomalies that could lead to incorrect or unsafe operations. This proactive approach helps in maintaining operational safety and preventing potential damage to the system or connected devices.
Aim
- Output current or voltage abnormality detection: Maintains the safety and reliability of the system by detecting incorrect behavior of output current or voltage values as quickly as possible.
Description
- Output voltage and current monitoring:
- Continuous monitoring: Continuously monitors the output voltage or current of the system to detect signals that are out of the normal range.
- Anomalous detection: Detects abnormal behavior of the output signal (e.g. overvoltage, undervoltage, overcurrent, undercurrent).
- Fault Detection and Response:
- Immediate Response: Issues an immediate warning when an abnormal signal is detected and takes protective measures as needed.
- System Protection: Implements protective mechanisms designed to minimize the risk of damage to system components or malfunctions.
Examples
Example 1: Output Voltage Monitoring in Automotive Electrical Systems
- Configuration: Detects electrical errors by monitoring the output voltage in the automotive electrical system.
- Operation Principle:
- Continuously monitors the output voltage of the car battery to detect overvoltage or undervoltage conditions.
- If the voltage is out of the acceptable range, the system issues an alarm and cuts off the power supply as needed.
- Advantages:
- Improves the electrical reliability of the electrical system and prevents damage due to voltage abnormalities.
Example 2: Output Current Monitoring in Industrial Control Systems
- Configuration: Monitors the output current in industrial control systems to detect abnormal current flow.
- Operation Principle:
- Continuously measures the output current to detect overcurrent or undercurrent conditions. – When an abnormal condition is detected, the system issues a warning and automatically cuts off the current to protect the equipment.
- Advantages:
- It improves the electrical safety of the equipment and prevents malfunctions caused by abnormal current.
Limitations and Challenges
1. Sensor Limitations
- Sensor Accuracy: The accuracy and response time of the sensor can directly affect the system’s ability to detect errors.
2. Increased Design Complexity
- Complex Signal Processing: The implementation of a real-time monitoring and processing system for various output signals can be complex.
3. Performance Overhead
- Additional Computational Requirements: Performance overhead may occur due to monitoring output signals, and should be minimized through optimization.
If you are interested in other articles about ISO 2626 Series, please refer to the links below!
[ISO 26262] #1. Part4-6 Technical Safety Concept (TSC)
[ISO 26262] #2. Safety Mechanisms for Electrical and Electronic
[ISO 26262] #3. Safety Mechanism for Processing Unit
[ISO 26262] #4. Safety Mechanisms for IO units and Interfaces