Motor Unit Circuit Board Layout for EMC Performance
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Solution Overview
Problem
The miniaturization of motor units for on-vehicle use poses challenges in achieving high electro-magnetic compatibility (EMC) due to limited space and low wiring flexibility on circuit boards, making it difficult to satisfy the required EMC performance, especially since motor driving control circuits are prone to malfunction from external electromagnetic noise and contribute to electromagnetic interference (EMI).
Innovation Solution
A circuit board design for motor units that includes a substrate with a magnetic detection element and motor drive control IC arranged at a minor angle, along with a ground electrode and transistor, where the motor drive control IC and magnetic detection element are positioned close to the motor lands to reduce wiring lengths and impedances, and a discontinuous annular solid pattern on the back surface for improved grounding, thereby reducing electromagnetic noise and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the circuit board is miniaturized to reduce fan size, then the fan size is reduced, but the wiring flexibility and area for mounting electronic components are reduced, making it difficult to satisfy EMC performance
Solution Approach 1:
The patent utilizes the third dimension (vertical arrangement) by stacking electronic components on multiple layers of the circuit board. The motor drive control IC, magnetic detection element, and other components are arranged across different layers, allowing compact horizontal footprint while maintaining adequate wiring space and EMC performance through vertical separation of noisy and sensitive circuits.
Solution Approach 2:
The patent applies different grounding strategies to different regions of the circuit board. A ground electrode is provided in a first region, while a discontinuous annular solid pattern (ground pattern) is provided in a second region. This localized grounding approach optimizes EMC performance in specific areas without requiring complete grounding coverage, enabling miniaturization while maintaining reliability.
2Reliability
If the motor driving control circuit is shielded with a metal case to improve EMC performance, then electromagnetic noise shielding is improved, but the fan size increases
Solution Approach 1:
The patent extracts the electromagnetic shielding function from a separate metal case and integrates it into the circuit board structure itself. The discontinuous annular solid pattern (ground pattern) on the circuit board provides localized electromagnetic shielding and noise suppression without requiring an additional metal enclosure, thereby maintaining compact fan size while achieving EMC performance.
Solution Approach 2:
The patent merges multiple functions into the circuit board: the circuit board serves as both the electrical connection substrate and the electromagnetic shielding structure. The ground electrode and discontinuous annular solid pattern are integrated directly into the board, combining the functions of electrical grounding and electromagnetic noise shielding in a single component, eliminating the need for separate shielding cases.
3Reliability
If the motor driving control IC and magnetic detection element are positioned close to the motor lands, then wiring length and impedance are reduced, but the arrangement space is constrained
Solution Approach 1:
The patent resolves the arrangement constraint by utilizing vertical stacking across multiple circuit board layers. The motor drive control IC and magnetic detection element are positioned on different layers, allowing both components to be close to the motor lands (reducing wiring length and impedance) while avoiding horizontal space conflicts. This three-dimensional arrangement simplifies the overall layout complexity.
Data Source
AI summary
To improve the EMC performance of an electronic device on which a motor is mounted. A circuit board (12) comprises a substrate (130), lands (P4, P5) that are formed on a main surface (131) of the substrate (130) and are for connecting a coil (17) of the motor (11), a magnetic detection element (122) that outputs a detection signal corresponding to a position of a rotor (14) of the motor (11), and a motor drive control IC (121) that generates drive signals (VOUTA, VOUTB) for driving the motor (11) based on the detection signal, wherein the magnetic detection element (122) and the motor drive control IC (121) are arranged in a region (AR1) on a side of a minor angle (θ) formed by a first straight line (a) and a second straight line (b) among regions that are on the main surface and are defined by the first straight line and the second straight line when viewing the substrate (130) from the main surface side, the first straight line connecting the land (P4) and an axis of an output shaft of the motor (11), the second straight line connecting the land (P5) and the axis of the motor (11).