Power Converter Out-of-Audio Control Loop for Audible Noise Reduction
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Solution Overview
Problem
Power supply converters often experience audible switching noise when operating in low or no load conditions due to burst switching patterns, which is undesirable in many applications.
Innovation Solution
A power converter with an out-of-audio control loop that includes a watchdog circuit and a pulse generator to provide negative current bursts through an inductor during a skip mode, ensuring the switching frequency remains out of the audible range and naturally transitions from skip mode to PWM mode to regulate the output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power converter operates in burst switching mode during low or no load conditions, then energy efficiency is improved, but audible switching noise is generated
Solution Approach 1:
The patent applies periodic action by implementing burst switching mode where the power converter operates in intermittent switching cycles during low or no load conditions. The controller enables the power switch to conduct current in periodic bursts rather than continuous operation, reducing average power consumption and improving energy efficiency while maintaining output voltage regulation through controlled switching intervals.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the switching frequency and duty cycle based on load conditions. During low or no load conditions, the controller modifies the switching parameters to operate in burst mode with extended off-periods, changing the temporal characteristics of switching to reduce audible noise while maintaining energy efficiency. The switching frequency is adjusted to remain outside the audible range.
2Object-generated harmful factors
If the switching frequency is reduced to eliminate audible noise, then audible switching noise is eliminated, but output voltage regulation becomes difficult
Solution Approach 1:
The patent implements feedback control through a controller that continuously monitors the output voltage and adjusts the switching duty cycle accordingly. The controller receives feedback about the output voltage level and dynamically modifies the switch control signals to maintain precise voltage regulation despite operating in burst switching mode with variable switching frequencies outside the audible range.
Solution Approach 2:
The patent applies dynamics by making the switching parameters adaptive rather than fixed. The controller dynamically adjusts the switching frequency and duty cycle based on real-time load conditions and output voltage requirements. This dynamic adjustment allows the system to maintain precise voltage regulation while operating at variable frequencies that remain outside the audible noise range.
3Loss of energy
If burst switching mode is used during low load conditions, then energy efficiency is improved, but output voltage may drift outside regulation range
Solution Approach 1:
The patent uses feedback control to monitor output voltage during burst switching operation and dynamically adjust switching parameters to prevent voltage drift. The controller continuously compares the output voltage against reference levels and modifies the duty cycle and switching timing to maintain voltage within the regulated range, ensuring reliability while preserving energy efficiency benefits.
Solution Approach 2:
The patent applies preliminary action by implementing predictive control mechanisms that anticipate voltage drift before it occurs. The controller adjusts switching parameters in advance based on detected trends in output voltage during burst mode operation, preventing voltage from drifting outside the regulation range while maintaining the energy-efficient burst switching pattern.
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 prevents net positive energy accumulation on output capacitors, avoiding runaway and improving energy efficiency by discharging the output voltage inductively, thus maintaining operation out of the audible range without forcing PWM mode.
Implementation Method 1
A switch circuit has an input terminal adapted to be coupled to an input voltage and at least one other terminal adapted to be coupled to an inductor. The switch circuit is configured to provide negative current from an output of the power converter through the at least one other terminal based on the at least one pulse.
Data Source
AI summary
A power converter includes a watchdog circuit having an input adapted to be coupled to a pause signal of a switching power supply. The watchdog circuit is configured to provide a start signal at an output thereof based on the pause signal indicating that the power converter has stopped switching for a threshold duration that is less than an audible range. A pulse generator circuit has an input coupled to the output of the watchdog circuit and is configured to generate at least one pulse based on the start signal. A switch circuit has an input terminal adapted to be coupled to an input voltage and at least one other terminal adapted to be coupled to an inductor. The switch circuit is configured to provide negative current from an output of the power converter through the at least one other terminal based on the at least one pulse.