Motor Driving Device Pre-Driver Circuit Consolidation
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Solution Overview
Problem
Existing motor driving devices for electric power steering systems are large due to the separate pre-driver circuits required for switching elements and relays, which increases the size and complexity of the device.
Innovation Solution
A motor driving device with a reduced number of pre-driver circuits by consolidating the second relay portion and motor relay portion into a single pre-driver circuit, allowing the controller to control and detect failures efficiently, thereby minimizing the device's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pre-driver circuits are provided for switching elements and relays, then each component can be controlled independently, but the size of the motor driving device increases
Solution Approach 1:
The patent combines the pre-driver circuits for the relays into a single integrated pre-driver unit that controls both the first relay portion and the motor relay portion. This merging approach reduces the total number of separate pre-driver circuits while maintaining the ability to independently control each relay through dedicated control signals, thereby reducing device size without sacrificing control independence.
Solution Approach 2:
The integrated pre-driver circuit is designed to perform multiple functions by controlling different relay portions through a unified structure. This multi-functional design allows a single pre-driver circuit to replace what would traditionally require multiple separate pre-driver circuits, achieving size reduction while preserving independent control capabilities through universal control interfaces.
2Ease of operation
If multiple pre-driver circuits are used for switching elements and relays, then each component can be driven separately, but the device complexity increases
Solution Approach 1:
The patent merges multiple pre-driver circuits into a single integrated pre-driver unit that controls both relay portions. This consolidation reduces the number of separate circuits and interconnections, simplifying the overall device architecture while maintaining separate driving capability through dedicated control signal paths to each relay portion.
3Loss of energy
If the power source relay is turned off during motor failure, then power supply can be cut off, but induced voltage from steering operation can still flow through closed circuit causing brake torque
Solution Approach 1:
The patent segments the power cutoff function into two distinct relay portions: the first relay portion that cuts off power supply from the power source, and the motor relay portion that specifically opens the closed circuit between the inverter portion and the motor winding group. This segmentation ensures that when motor failure occurs, both the power supply is cut off and the induced voltage brake torque is prevented by opening the return path, thereby eliminating the harmful effect of induced voltage.
Data Source
AI summary
In a motor driving device, a first relay portion is connected between a power source and an inverter portion, a second relay portion is connected between the first relay portion and the inverter portion, and a motor relay portion is connected between the inverter portion and a winding group of a motor. Inverter pre-driver circuits respectively drive switching elements of the inverter portion. A first pre-driver circuit drives the first relay portion. A second pre-driver circuit drives the second relay portion and the motor relay portion. A controller controls driving of the inverter portion, the first relay portion, the second relay portion, and the motor relay portion, and detects a failure of the first relay portion, the second relay portion, and the motor relay portion.