EPS Gate Driver Voltage Threshold Control
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Solution Overview
Problem
Conventional electric power steering apparatuses lack the ability to appropriately switch between assist control and assist stop control based on the factor of abnormality in motor control, leading to unnecessary shutdowns even when only one phase of a brushless DC motor is disconnected.
Innovation Solution
The apparatus determines the state of the gate driver power source voltage relative to the inverter device power source voltage using threshold values, allowing for precise control of switching between assist control, assist limit control, and assist stop control, preventing overheating of semiconductor switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional EPS stops assist control when any abnormality occurs in motor control, then safety is improved, but unnecessary shutdowns occur when only one phase is disconnected
Solution Approach 1:
The invention segments the abnormality detection into specific phases (U-phase, V-phase, W-phase) and specific components (FETs, gate drivers). By detecting which specific phase or component is abnormal, the system can determine whether assist control can continue using the remaining normal phases, rather than stopping all assist control when any abnormality occurs.
Solution Approach 2:
The invention changes the control parameter from a binary state (assist control on/off) to a multi-state system based on voltage thresholds. By comparing gate driver power source voltage against threshold values, the system determines whether to continue assist control, limit assist control, or stop assist control, allowing for graduated responses to abnormal conditions.
2Power
If EPS uses a separate gate driver power source to supply higher voltage to FET gates, then FET switching capability is improved, but voltage decrease in gate driver power source causes unnecessary assist stop
Solution Approach 1:
The invention introduces threshold voltage parameters to determine control mode. By comparing the gate driver power source voltage against predetermined threshold values, the system can distinguish between temporary voltage fluctuations and actual abnormalities, enabling appropriate control decisions (continue assist, limit assist, or stop assist) rather than unnecessary shutdowns.
Solution Approach 2:
The invention implements feedback by continuously monitoring the gate driver power source voltage and comparing it against threshold values. This feedback mechanism allows the control device to adjust assist control in real-time based on voltage conditions, ensuring stable operation when voltage is sufficient and appropriate limitation or shutdown when voltage becomes insufficient.
3Productivity
If EPS continues assist control when voltage threshold is not met, then assist availability is improved, but semiconductor switching elements overheat
Solution Approach 1:
The invention uses voltage threshold parameters to determine when to limit or stop assist control. By monitoring whether the gate driver power source voltage meets the threshold requirements, the system prevents overheating by stopping assist control before temperatures become dangerous, while still allowing assist control to continue when voltage conditions are sufficient.
Data Source
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AI summary
An electric power steering apparatus (1) includes an EPS actuator (10) that applies assist force to a steering system, and an ECU (11) that controls operation of the EPS actuator (10). The ECU (11) includes an inverter device (32), a gate driver circuit (31), a gate driver power source (29), a microcomputer (16), and the like. The microcomputer (16) switches assist control to assist stop control, based on an indication of a voltage decrease in the gate driver power source (29).