Electric Power Steering PCB Layout for Low-Noise Current Sensing
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Solution Overview
Problem
Existing electric drive devices and electric power steering devices suffer from noise superimposed on the detection value detected by a current detection element in the path from the current detection element to the control circuit, which affects the accuracy and performance of motor control.
Innovation Solution
The configuration of the electric drive device includes a shaft with a motor rotor and stator, a magnetic sensor for detecting rotation, and a circuit board with specific mounting areas for current detection elements and driver circuits, arranged to minimize wiring length and reduce noise interference, along with a heat sink for thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current detection element is placed close to the motor for accurate current detection, then the detection precision is improved, but the wiring path becomes longer and more noise is superimposed on the detection value
Solution Approach 1:
A signal amplifier circuit is introduced as an intermediary component between the current detection element and the control circuit. This amplifier circuit processes the detection value locally, allowing the detection element to be positioned close to the motor for accurate measurement while the amplified signal is then transmitted to the control circuit with reduced noise impact
Solution Approach 2:
The circuit board is positioned on the anti-load side of the shaft along the axial extension line, creating a spatial arrangement where the detection path and power transmission path are separated in different dimensional orientations. This reduces electromagnetic interference and noise coupling between signal lines and power lines
2Object-affected harmful factors
If the wiring path from the current detection element to the control circuit is shortened to reduce noise, then the noise interference is reduced, but the layout complexity of the circuit board increases
Solution Approach 1:
The circuit board is divided into distinct functional regions: a first region for the signal amplifier circuit and current detection elements, and a second region for the control circuit. This segmentation allows optimized placement of components to minimize wiring lengths for sensitive signals while maintaining overall system functionality and reducing layout complexity through organized zoning
Solution Approach 2:
Different regions of the circuit board are assigned different functional qualities - the first region is optimized for signal conditioning with minimal wiring to detection elements, while the second region handles control functions. This local optimization allows each area to be designed for its specific purpose, reducing overall system complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces noise superimposed on the detection value, leading to improved control of the electric motor and suppression of torque ripple, enhancing the operability of the electric power steering device.
Implementation Method 1
a magnetic sensor that detects rotation of the magnet
Implementation Method 2
a heat sink disposed between the circuit board and the electric motor
Implementation Method 3
a motor stator including a stator core that rotates the motor rotor and a plurality of coil groups that are divided into at least two systems of coil groups of a first coil group and a second coil group for every three phases and excite the stator core with three-phase alternating current
Data Source
AI summary
Provided are an electric drive device and an electric power steering device that reduce noise superimposed on a detection value detected by a current detection element in a path from the current detection element to a control circuit. The electric drive device includes a motor and an electronic control device including a circuit board. With a position on an extension line in an axial direction of a shaft as a reference position, a mounting area for a first motor driver circuit, a mounting area for a first current detection element, a mounting area for a plurality of drive elements of a first inverter circuit, and a disposition area for a first coil wiring are disposed in this order from the reference position to one side in a first direction.