Dual Voltage Monitoring for Fast Undervoltage Load Shedding
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Solution Overview
Problem
In automotive systems, undervoltage conditions can lead to insufficient or unstable voltage for critical loads, risking loss of critical vehicle functions, and existing solutions fail to rapidly and effectively manage power distribution to ensure compliance with ISO 26262 safety standards.
Innovation Solution
A power supply control apparatus with dual voltage monitors and a control circuit that rapidly disconnects non-critical loads from the supply voltage upon detecting undervoltage, using operational amplifiers and a latch circuit to ensure rapid response times and reduce interference, achieving ASIL B functional safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-critical loads are not switched off during undervoltage condition, then the power supply can maintain voltage for longer duration, but critical loads may receive insufficient or unstable voltage resulting in loss of critical vehicle function
Solution Approach 1:
The patent segments the loads into critical and non-critical categories, allowing differential power management. The control circuit selectively disconnects non-critical loads while maintaining power to critical loads during undervoltage conditions, resolving the contradiction between maintaining overall power supply stability and ensuring critical functions receive sufficient power.
Solution Approach 2:
The patent extracts non-critical loads from the overall power consumption during undervoltage conditions by selectively disconnecting them. This separation allows the power supply to maintain adequate voltage levels for critical loads by removing the unnecessary load demand, thus preserving critical vehicle functions.
2Reliability
If a single voltage monitor is used to detect undervoltage condition, then the device complexity is reduced, but the reliability and safety compliance (ASIL requirements) may be insufficient
Solution Approach 1:
The patent applies local quality by implementing redundant voltage monitoring specifically for safety-critical undervoltage detection, while other system functions can use simpler monitoring. This targeted redundancy ensures ASIL compliance for critical functions without unnecessarily complicating the entire system.
Solution Approach 2:
The patent implements beforehand cushioning by using multiple voltage monitors to detect undervoltage conditions before they affect critical loads. This redundant monitoring system provides a safety margin and ensures reliable detection of undervoltage conditions, meeting functional safety requirements through proactive rather than reactive protection.
3Reliability
If the response time for load disconnection is extended, then the control circuit can perform more comprehensive analysis, but the voltage drop may cause loss of critical function before protection is activated
Solution Approach 1:
The patent implements preliminary action by pre-configuring the control circuit with predetermined disconnection logic for non-critical loads. When undervoltage is detected, the system immediately executes the pre-planned disconnection sequence without requiring complex real-time analysis, thus achieving rapid protection within 100 μs while preserving critical functions.
Solution Approach 2:
The patent applies skipping by bypassing complex analysis steps during undervoltage events and directly executing the load disconnection function. This rushed-through approach prioritizes speed of protection over comprehensive analysis, ensuring critical functions are protected within the 100 μs timeframe before voltage collapse occurs.
Data Source
AI summary
An apparatus controls the supply of power to multiple loads. The apparatus includes a first voltage monitor for monitoring a supply voltage. The apparatus includes a second voltage monitor for monitoring the supply voltage. The apparatus includes a control circuit for controlling a load driver to selectively drive the loads. The control circuit is configured to control the load driver to disconnect one or more predetermined ones of the loads from the supply voltage, in response to either of the first voltage monitor or the second voltage monitor determining an undervoltage condition. The first voltage monitor and the second voltage monitor are connected to the supply voltage in parallel.