Switching Power Source Light-Load Acoustic Noise Reduction
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Solution Overview
Problem
Switching power sources generate undesirable audible sounds during light-load running due to extended idle periods, which increase transformer resonance frequencies, leading to increased switching losses and size constraints when attempting to reduce these sounds.
Innovation Solution
A switching power source that varies the number of pulses in driving pulse groups during light-load running, using a pseudo-resonance method with a control IC to manage the switching element's operation, thereby reducing the FFT spectrum level across a wide frequency band without increasing transformer size or switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the idle period is extended to decrease switching frequency and reduce switching losses, then power saving is improved, but audible beat sounds are generated due to transformer resonance
Solution Approach 1:
The patent applies periodic action by dividing the idle period into multiple sub-idle periods interspersed with pulse groups. Instead of one long idle period, the system performs multiple short switching cycles separated by brief idle intervals. This periodic structure prevents the transformer driving current from forming a continuous delta-function waveform, thereby reducing harmonic wave components and audible beat sounds while maintaining reduced switching frequency for power saving.
Solution Approach 2:
The patent segments the idle period into multiple sub-idle periods and divides the switching operation into multiple pulse groups. By segmenting the continuous idle period into discrete intervals with pulse groups in between, the system avoids generating strong harmonic waves while still achieving the power-saving effect of reduced switching frequency. This segmentation transforms the harmful continuous waveform into a distributed pattern with reduced spectral energy.
2Use of energy by moving object
If the switching frequency is decreased to improve power saving during light-load running, then energy efficiency is improved, but the transformer resonance frequency enters the audible range producing disagreeable sounds
Solution Approach 1:
The system uses periodic action by implementing multiple pulse groups with idle periods between them during light-load operation. This maintains a low effective switching frequency for power saving while preventing the transformer resonance from settling into a continuous audible beat pattern. The periodic interruption distributes the energy across multiple shorter cycles rather than one long cycle.
Solution Approach 2:
The patent applies dynamics by adaptively controlling the switching frequency based on load conditions. During light-load running, the system dynamically adjusts to use multiple pulse groups with idle periods, optimizing for both power saving and noise reduction. This dynamic adaptation allows the system to switch between different operating modes to balance energy efficiency and acoustic comfort.
3Productivity
If the number of switching times is decreased by extending idle period, then operation efficiency is improved, but harmonic wave components increase causing audible resonance
Solution Approach 1:
The patent segments the switching operation into multiple pulse groups separated by idle periods. This segmentation prevents the formation of a single large delta-function waveform that would generate strong harmonics. By distributing the switching events across multiple smaller groups, the harmonic content is reduced while maintaining the overall reduced switching frequency for improved operation efficiency.
Solution Approach 2:
The system employs periodic action by repeating pulse groups at intervals separated by idle periods. This periodic structure with multiple short cycles instead of one long cycle reduces the spectral energy at resonant frequencies, thereby reducing harmonic wave components while maintaining efficient operation through reduced average switching frequency.
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 approach effectively reduces the production of disagreeable beat sounds from the transformer by controlling the transformer driving current waveforms, maintaining efficiency and preventing increased switching losses, while ensuring the transformer's mechanical resonance frequency is not exceeded.
Implementation Method 1
an alternating-current (AC) voltage input from a commercial alternating current power source 100 is input into a transformer 104 via a rectification unit 140, and a switching element 108 such as a field effect transistor (FET) performs switching operation at a predetermined frequency, based on a signal sent out from a control circuit 144, thereby a primary side of the transformer 104 is driven
Implementation Method 2
a switching element 108 such as a field effect transistor (FET) performs switching operation at a predetermined frequency, based on a signal sent out from a control circuit 144, thereby a primary side of the transformer 104 is driven. Then, the DC voltage V is generated by smoothing a voltage generated on a secondary side of the transformer 104
Implementation Method 3
the DC voltage V is generated by smoothing a voltage generated on a secondary side of the transformer 104 by a smoothing unit 141
Data Source
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AI summary
In a switching power source, in a state where a second voltage smaller than a first voltage is output from an output means by intermittently driving a switching means (108), the switching means (108) changes a number of driving times of the switching means (108) for each driving cycle when the switching means (108) is intermittently driven.