PCB-Integrated Electric Filter for DC Motor Noise and EMI Reduction
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Solution Overview
Problem
Household appliances with electric motors face challenges in reducing motor noise and electromagnetic interference (EMI) to meet strict standards, such as BS EN 55014-2:1997, as existing solutions are inadequate in effectively addressing these issues.
Innovation Solution
A printed circuit board with an integrated electric filter that includes a conductive material coating for grounding, a freewheeling diode, X2Y capacitor, ferrite beads, and an RC filter, arranged symmetrically around the motor to provide comprehensive noise reduction and EMI filtering, with ventholes for heat dissipation and grounding to the motor chassis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an electric filter is added to reduce motor noise and EMI, then noise emission is reduced, but device complexity increases
Solution Approach 1:
The patent combines multiple filtering functions (common-mode filtering, differential-mode filtering, voltage overshoot protection) into a single integrated filter circuit. The filter integrates an X2Y capacitor for common-mode noise, ferrite beads for differential-mode noise, and RC snubber circuits for voltage overshoot, all within one circuit board assembly, thereby reducing overall system complexity while maintaining comprehensive noise reduction.
Solution Approach 2:
The filter circuit serves multiple functions simultaneously: it filters common-mode noise through the X2Y capacitor, filters differential-mode noise through ferrite beads, protects against voltage overshoot through RC snubber circuits, and provides grounding through conductive material. This multi-functionality reduces the need for separate components and simplifies the overall system design.
2Reliability
If a conductive material coating is applied to the printed circuit board for grounding, then grounding effectiveness is improved, but manufacturing complexity increases
Solution Approach 1:
The conductive material coating on the printed circuit board serves dual purposes: it provides effective grounding for the filter circuit and simultaneously acts as a shield for noise emissions. The coating is integrated into the board manufacturing process, eliminating the need for separate grounding wire installations and reducing overall manufacturing complexity.
3Reliability
If the printed circuit board is mounted directly to the motor chassis, then grounding is improved, but heat dissipation becomes a problem
Solution Approach 1:
The printed circuit board incorporates a porous or perforated structure that allows heat to pass through while maintaining electrical grounding contact with the motor chassis. The conductive material coating ensures electrical continuity for grounding purposes, while the porous structure provides thermal pathways for heat dissipation, simultaneously addressing both grounding effectiveness and heat management.
4Temperature
If ventholes are added to the printed circuit board for heat dissipation, then temperature control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The printed circuit board is segmented into multiple ventholes distributed across its surface, allowing heat to dissipate through various pathways. This segmentation approach reduces the precision requirements for each individual venthole compared to a single large opening, as the cumulative effect of multiple smaller ventholes achieves the desired heat dissipation while being more tolerant of manufacturing variations.
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
The solution effectively reduces noise emissions and complies with stringent noise and EMI requirements by providing a common ground, filtering common-mode noise, dissipating energy as heat, and reducing voltage overshoot, thereby enhancing the operational performance of DC motors in household appliances.
Implementation Method 1
the other side of the board with a conductive material via which a ground point common the electric filter and a chassis of the motor is accomplished
Implementation Method 2
A ferrite bead is an inductor which is constructed to become highly resistive at a design frequency range and current induced in the bead is advantageously dissipated as heat
Implementation Method 3
the X2Y capacitor is coupled in parallel to the motor, wherein any common-mode noise appearing on the motor terminals advantageously is filtered to the common ground formed by the motor chassis by the two capacitors comprised in the X2Y capacitor
Implementation Method 4
since the printed circuit board is mounted directly to the motor chassis, it is advantageous to provide the board with ventholes for dissipating heat from the motor
Data Source
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AI summary
The present invention relates to a printed circuit board (30) and an electric filter (20). The printed circuit board is arranged to accommodate electric circuitry on one side, the other side of the printed circuit board being arranged with an electrically conductive material via which a ground point common to the electric circuitry and a device contacting the conductive material is accomplished. The electric filter for filtering electric signals of a DC motor (40) comprises a freewheeling diode (D1) coupled in parallel to the motor, an X2Y capacitor (C4) coupled in parallel to the motor, wherein a ground terminal (MGND) of the X2Y capacitor is coupled to a chassis of the motor, a low pass filter comprising a ferrite bead (L1, L2) and a capacitor (C1, C2) connected to each motor terminal (M+, M-), and a resistor-capacitor (RC) filter (R1, C3) coupled in parallel to the motor.