Power Converter Audible Noise Reduction via Frequency Skipping
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Solution Overview
Problem
Conventional switched mode power converters generate audible noise during low switching frequencies due to mechanical resonance of transformers, particularly at frequencies below 20 kHz, which is undesirable during light load conditions.
Innovation Solution
A controller for power converters that skips certain switching frequencies or adjusts current limits to prevent switching within the audible noise range, using an audible noise window circuit and reduction circuit to manage switching parameters and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced during light load conditions to improve efficiency, then power dissipation is reduced, but audible noise increases due to mechanical resonance of transformers
Solution Approach 1:
The patent dynamically changes the switching frequency parameter based on load conditions. During light load conditions, the controller adjusts the switching frequency to fall outside the audible noise range (below 20 kHz or above 20 kHz) while maintaining efficient operation. This resolves the contradiction by modifying the frequency parameter to eliminate audible noise without significantly compromising efficiency.
Solution Approach 2:
The patent implements dynamic adjustment of switching frequency based on real-time detection of audible noise conditions. The controller monitors load conditions and automatically adjusts the switching frequency to avoid the audible range, creating a dynamic system that adapts to changing conditions rather than using a fixed frequency approach.
2Object-generated harmful factors
If the switching frequency is increased to avoid audible noise range, then audible noise is reduced, but power dissipation increases during light load conditions
Solution Approach 1:
The patent changes the switching frequency parameter to fall below the audible noise range (below 20 kHz) during light load conditions. This lower frequency operation reduces audible noise while maintaining lower power dissipation compared to operating at higher frequencies, thus resolving the contradiction between noise reduction and energy efficiency.
3Device complexity
If conventional power converters operate at fixed switching frequencies, then control is simplified, but audible noise cannot be avoided during light load conditions
Solution Approach 1:
The patent implements a dynamic frequency adjustment mechanism that modifies the switching frequency based on detected audible noise conditions. The controller includes circuitry that monitors for audible noise and automatically adjusts the switching frequency to eliminate it, creating a dynamic control system that adapts to changing operational conditions rather than using a fixed frequency approach.
Solution Approach 2:
The patent incorporates a feedback mechanism where the controller monitors operational conditions and audible noise levels, then adjusts the switching frequency accordingly. This closed-loop control system detects when audible noise is present and automatically modifies the switching frequency to eliminate it, providing feedback-based adaptation without requiring complex external control circuits.
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
Effectively minimizes audible noise by ensuring the power switch operates outside the audible noise range, maintaining efficiency and reducing power dissipation during light load conditions.
Implementation Method 1
a high voltage alternating current (ac) input is converted to provide a well-regulated direct current (dc) output through an energy transfer element
Implementation Method 2
Conventional switched mode power converters generate audible noise during low switching frequencies due to mechanical resonance of transformers
Data Source
AI summary
A controller for use in a power converter includes a drive circuit coupled to generate a drive signal to control switching of a power switch of the power converter in response to a feedback signal to control a transfer of energy from an input to an output of the power converter. An audible noise window circuit is coupled to generate a frequency skip signal in response to the feedback signal. The frequency skip signal is activated in response to a frequency of a feedback request signal responsive to the feedback signal being within an audible noise window. An audible noise reduction circuit is coupled to output a reduction signal in response to the frequency skip signal. The drive circuit is coupled to generate the drive signal in response to the reduction signal from the audible noise reduction circuit.