Speaker Noise Reduction via Offset Current in Compact Electronics
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Solution Overview
Problem
The reduction in size of electronic devices limits the placement of power sources relative to speakers, leading to noise generation due to induction currents in the first speaker during handset mode operation, as the H-field from radio frequency power causes noise recognizable by the user.
Innovation Solution
The electronic device incorporates a flexible board with a wire surrounding the coil area of the first speaker and a connection terminal connected to the printed circuit board, allowing the processor to recognize current values and generate offset currents through this wire to reduce noise, and includes a second amplifier connected to the second speaker, which can be used to offset the H-field when the device is in handset mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the power source is placed close to the first speaker to reduce device size, then the device size is reduced, but noise is generated due to induction currents in the first speaker
Solution Approach 1:
A second amplifier is introduced as an intermediary component to generate an offset current that counteracts the H-field produced by the power source. This mediator component enables the power source to be placed close to the first speaker without causing noise, as the second amplifier actively compensates for the harmful electromagnetic interference.
Solution Approach 2:
The second amplifier generates an offset current in advance to counteract the H-field before it can cause harmful induction currents in the first speaker. This preliminary anti-action prevents the noise generation that would otherwise occur when the power source is positioned close to the speaker.
2Object-affected harmful factors
If the power source is placed far away from the first speaker to avoid noise, then noise is reduced, but the device size increases due to limited PCB space
Solution Approach 1:
The second amplifier serves as a mediator that enables close placement of the power source while maintaining low noise levels. Without this intermediary, the power source would need to be positioned far from the first speaker, increasing device volume. The second amplifier allows compact integration by actively managing the electromagnetic interference.
Solution Approach 2:
The system dynamically adjusts the offset current parameter generated by the second amplifier based on the operating conditions. By changing the current parameter in response to power source positioning and operational mode, the system maintains noise reduction while enabling compact device design.
3Power
If the first speaker operates in handset mode with high power current, then output performance is improved, but induction current noise becomes recognizable to the user
Solution Approach 1:
The system employs feedback control where the second amplifier monitors the power current in the first speaker and adjusts the offset current accordingly. During handset mode operation, the feedback mechanism ensures the offset current matches the H-field variations, maintaining noise reduction while allowing high power output.
Solution Approach 2:
The second amplifier generates offset current in advance to counteract the strong H-field produced during handset mode. This preliminary anti-action prevents the formation of harmful induction currents in the first speaker, enabling high power operation without recognizable noise to the user.
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 effectively reduces noise in the first speaker by offsetting the H-field generated by the power current, improving the call quality and user experience by minimizing noise levels.
Implementation Method 1
an H-field may be generated by a power (e.g., radio frequency (RF) power) current of the electronic device. The H-field generated by the power current may cause an induction current to flow through a coil in the first speaker
Implementation Method 2
a second amplifier connected to the second speaker, which can be used to offset the H-field when the device is in handset mode
Data Source
AI summary
An electronic device includes: a housing; a first speaker in the housing; and a printed circuit board in the housing and surrounding at least a portion of the first speaker, wherein the first speaker includes: a coil area in which a coil for an operation of the first speaker is disposed; a flexible board on an outer portion of the coil area and including a wire surrounding at least a portion of the coil area; and a connection terminal at one end of the flexible board and electrically connected to the printed circuit board.