Resonant Power Converter Controller for Acoustic Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional resonant power converters face challenges with switching frequency control for linear operation, soft switching, audio-susceptibility, and acoustic noise, particularly during burst switching at no-load conditions.
Innovation Solution
An integrated controller for resonant power converters modulates the switching frequency using feedback and feed-forward signals, incorporates a power management circuit for burst switching, and disables burst signals when operating in the audio band to reduce acoustic noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the switching frequency is controlled to higher or lower than the resonant frequency to adapt to load changes, then the power converter can deliver maximum power to the load, but the switching frequency change must be restricted to ensure linear operation and achieve soft switching
Solution Approach 1:
The patent employs feedback control by detecting the current through a sensing resistor and comparing it with a reference signal. The feedback signal is used to adjust the switching frequency dynamically, allowing the power converter to adapt to load changes while maintaining linear operation and soft switching conditions. The feedback mechanism ensures that the switching frequency is automatically adjusted within the required restrictions.
2Use of energy by moving object
If burst switching scheme is used for power saving at no load, then power consumption is reduced, but audio-susceptibility becomes poor and acoustic noise is generated
Solution Approach 1:
The patent uses periodic burst switching action to achieve power saving at no load conditions. By switching between on and off states in a periodic manner, the power converter reduces average power consumption while maintaining the ability to respond to load changes. The periodic action is controlled to avoid audio-frequency ranges that would cause acoustic noise and poor audio-susceptibility.
3Reliability
If leakage inductance of the transformer or additional magnetic components is employed as a resonant inductor, then circulating current is generated for soft switching, but the structure becomes more complex
Solution Approach 1:
The patent makes the transformer serve multiple functions: it provides galvanic isolation between primary and secondary sides, transforms voltage levels, and simultaneously functions as the resonant inductor for generating circulating current. By making the transformer multi-functional, additional separate magnetic components are eliminated, reducing overall device complexity while maintaining soft switching capability.
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 enables linear operation, improves audio-susceptibility, and reduces acoustic noise by dynamically adjusting switching frequency and burst signal duty cycles based on load conditions, enhancing power efficiency and noise reduction.
Implementation Method 1
The resonant inductor associated with a resonant capacitor forms a resonant circuit for the power converter to deliver the maximum power to the load
Implementation Method 2
An independent feedback terminal is coupled to the output of the power converter to receive a feedback signal through an optical-coupler
Data Source
AI summary
An integrated control circuit for a resonant power converter includes a minimum-frequency programming circuit connected a first resistor to program a minimum switching frequency of the power converter. A feedback circuit is coupled to a feedback terminal to receive a feedback signal for generating an adjustment signal. A maximum-frequency programming circuit connects a second resistor to determine a maximum switching frequency in response to the adjustment signal. An oscillator is coupled to the minimum-frequency programming circuit and the maximum-frequency programming circuit to generate an oscillation signal for determining the switching frequency of the power converter. A feed-forward circuit is connected to a feed-forward terminal to receive a feed-forward signal represents the input voltage of the power converter. The switching frequency is increased in response to decrease of the feedback signal, and the switching frequency is increased in response to the increase of the feed-forward signal.