Switching Power Source Beat Sound Reduction via Resonance Cycle Control
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Solution Overview
Problem
Conventional switching power sources generate undesirable beat sounds during light load running due to low switching frequencies, which are difficult to mitigate without increasing transformer size or switching losses.
Innovation Solution
A switching power source that sets the OFF-period of the switching element according to the resonance cycle of the transformer, reducing the number of switching operations and maintaining efficiency by controlling the ON-period to minimize energy stored per operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pause period is prolonged to reduce the number of switching operations, then switching losses are reduced, but the switching frequency drops to generate audible beat sounds
Solution Approach 1:
The patent applies periodic action by controlling the switching element to operate in periodic ON/OFF cycles during light load running. The control circuit generates periodic drive signals that turn the switching element ON for a predetermined period and then OFF, creating a periodic switching pattern. This periodic operation maintains the switching frequency above the audible range while reducing the number of switching operations compared to continuous switching, thereby achieving both energy efficiency and noise reduction.
Solution Approach 2:
The patent changes the operational parameters of the switching element by adjusting the ON-period and pause period dynamically based on load conditions. During light load running, the control circuit modifies the duty cycle and switching frequency parameters to optimize performance. Specifically, the ON-period is set to a value that stores minimal energy in the transformer, and the pause period is adjusted to maintain switching frequency above audible thresholds, thus resolving the contradiction between energy loss and noise generation.
2Use of energy by moving object
If the switching frequency is reduced to save power during light load running, then power efficiency is improved, but the transformer generates beat sounds in the audible range
Solution Approach 1:
The control circuit implements periodic switching action during light load conditions, where the switching element is activated in periodic bursts rather than continuously. This periodic operation reduces the average power consumption while maintaining the switching frequency within the ultrasonic range, preventing audible beat sounds. The periodic ON/OFF pattern allows the system to achieve power efficiency improvements without compromising acoustic performance.
Solution Approach 2:
The patent employs dynamic control of the switching frequency and duty cycle based on real-time load conditions. The control circuit dynamically adjusts the switching parameters to maintain optimal performance across different operating conditions. During light load running, the system dynamically sets the switching frequency above the audible threshold while adjusting the ON-period to minimize energy storage, thereby dynamically resolving the trade-off between power efficiency and noise generation.
3Productivity
If the ON-period is prolonged to increase energy per switching operation, then the number of switching times is reduced, but switching losses increase
Solution Approach 1:
The control circuit changes the ON-period parameter to an optimized value during light load running, setting it to a predetermined period that stores minimal energy in the transformer. This parameter adjustment reduces the energy dissipated during each switching operation while maintaining a reduced number of switching cycles. By optimizing the ON-period parameter, the system achieves lower switching losses without requiring a high number of switching operations, thus resolving the contradiction between productivity and energy loss.
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 beat sounds without enlarging the transformer or increasing switching losses, maintaining efficiency by optimizing the switching frequency to be higher than the mechanical resonance frequency, thus minimizing audible noise.
Implementation Method 1
a primary winding wire 105 of the transformer 104, a secondary winding wire 106 of the transformer 104... a transformer 104
Implementation Method 2
energy of one switching operation is increased by prolonging an ON-period of the switching element... the ON-period to minimize energy stored per operation
Implementation Method 3
The resonance frequency generated by mechanical vibrations of the transformer has, though dependent on a core shape of the transformer, a peak approximately at several kilohertz to several tens of kilohertz
Implementation Method 4
driving a switching element such as a field effect transistor (FET) with a predetermined drive frequency
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
In a switching power source, an OFF-period of switching is set according to a resonance cycle when a transformer is driven.