DC Driver Output Monitoring Circuit for On-Off State Diagnostics
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Solution Overview
Problem
Existing DC motor driver monitoring solutions fail to provide continuous feedback during both on and off states, failing to meet the safety requirements of standards like ISO26262 ASIL-B, which necessitates constant monitoring.
Innovation Solution
A circuit is introduced that compares output voltages of a DC motor driver with a threshold voltage during both on and off states, using selection circuitry to determine a monitored voltage signal, and provides feedback to a control unit for anomaly detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current sensing operations are used to monitor DC motor driver output, then feedback related to control output currents can be provided to microcontrollers, but continuous monitoring during both on and off states cannot be achieved
Solution Approach 1:
The monitoring circuit is designed to perform multiple functions: it can monitor both voltage and current parameters, and it can operate during both on and off states of the DC motor driver. The same circuit infrastructure (comparators, selection circuitry) is reused across different monitoring modes, eliminating the need for separate monitoring circuits for different operational states.
Solution Approach 2:
The monitoring circuit dynamically adapts its monitoring parameters based on the operational state. During on-states, it monitors current through the H-bridge; during off-states, it monitors voltage at the output terminals. The selection circuitry dynamically switches between different monitoring modes based on driver state, enabling continuous monitoring without requiring constant high-current sensing paths.
2Reliability
If voltage comparison with threshold is performed during both on and off states, then continuous monitoring capability is achieved, but additional circuit components are required
Solution Approach 1:
The voltage comparison functionality is merged with the existing current monitoring circuitry. The same comparator units used for current monitoring are also employed for voltage comparison during off-states. The selection circuitry merges multiple monitoring signals (current sense signals and voltage comparison signals) into a unified monitoring output, reducing the need for completely separate monitoring infrastructure.
Solution Approach 2:
The monitoring circuit uses simplified copies of the main power circuitry for sensing purposes. Instead of building entirely new monitoring systems, it creates scaled-down versions using the same topological structures (comparators with threshold references) that can be activated in different operational modes. This copying approach enables extended functionality with minimal additional complexity.
3Reliability
If monitoring is extended to off-states, then diagnostic fault coverage is improved, but power consumption increases
Solution Approach 1:
The enhanced monitoring during off-states is implemented periodically rather than continuously. The monitoring circuit activates voltage comparison and selection circuitry only when the DC motor driver transitions to off-states, rather than maintaining full monitoring activity throughout all time. This periodic activation during specific operational windows extends diagnostic coverage while limiting power consumption to necessary intervals.
Data Source
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AI summary
Circuit (30; 30') for monitoring phases of a Direct Current, DC, driver, said DC driver being configured to drive a load via a first terminal and a second terminal coupled to respective load terminals switching a polarity there applied; wherein said circuit (30; 30') comprises: - a first comparison circuitry (AMP1) configured to receive a first voltage (V_OUTa) of the first terminal and a threshold voltage (Vth), to compare said first voltage (V_OUTa) with said threshold voltage (Vth), obtaining a first comparison voltage, and to provide said first comparison voltage to a selection circuitry (PDa,b); - a second comparison circuitry (AMP2) configured to receive a second voltage (V_OUTb) of the second terminal and said threshold voltage (Vth), to compare said second voltage (V_OUTb) with said threshold voltage (Vth), obtaining a second comparison voltage, and to provide said second comparison voltage to the selection circuitry (PDa,b); and - the selection circuitry (PDa,b) being configured to receive the first comparison voltage, the second comparison voltage, and a selection signal (SEL) indicating to select either the first comparison voltage or the second comparison voltage, and to select, based on said selection signal (SEL), said first comparison voltage or said second comparison voltage as a monitored voltage signal (POUT).