Switching Power Converter with Burst Mode Control
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Solution Overview
Problem
Switching power supplies face challenges in maintaining efficiency and reducing audible noise when operating at low power levels, as high-frequency switching can lead to difficulties in achieving low duty cycles and results in significant losses.
Innovation Solution
The implementation of a switching power converter that operates in a series of converter cycles with a duration of 1% or less of the pulse duration, varying the duration of the operating interval based on the power level, and adjusting the current envelope to approximate the pulse waveform, allowing for efficient power delivery during selected portions of the pulse duration and minimizing power delivery during the remainder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous high-frequency switching is used to maintain voltage regulation, then voltage control precision is improved, but switching losses increase and efficiency deteriorates at low power levels
Solution Approach 1:
The patent applies periodic action by transitioning from continuous switching to discontinuous periodic switching. The converter operates in bursts separated by idle periods, where each burst consists of multiple switching cycles. This periodic operation reduces average switching losses while maintaining voltage regulation through controlled duty cycles during active bursts, directly resolving the contradiction between continuous operation precision and energy efficiency.
2Loss of energy
If switching frequency is lowered to reduce switching losses, then energy efficiency is improved, but audible noise increases
Solution Approach 1:
The patent applies dynamics by making the switching frequency adaptive rather than fixed. The controller dynamically adjusts the switching frequency based on load conditions, operating in discontinuous mode at lower frequencies during light loads to reduce losses, and transitioning to continuous mode at higher frequencies during heavy loads to prevent audible noise. This dynamic adaptation resolves the contradiction between energy efficiency and noise reduction.
3Power
If duty cycle is reduced to operate at low power levels, then power delivery is reduced, but voltage regulation becomes difficult to maintain
Solution Approach 1:
The patent applies continuity of useful action by implementing discontinuous conduction mode with controlled bursts of switching activity. Instead of maintaining continuous low-duty-cycle operation, the converter performs concentrated bursts of energy transfer followed by idle periods. This approach maintains effective voltage regulation by ensuring sufficient energy transfer during active bursts while reducing average power delivery during idle periods, resolving the contradiction between low power delivery and voltage regulation.
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 enables efficient power conversion across a range of power levels while reducing audible noise and maintaining voltage regulation, even at low load conditions, by optimizing the operating interval and current envelope in response to changing power demands.
Implementation Method 1
a first DC-DC switching power converter for converting power received from the unipolar input for delivery to a first load via a first output at a first DC output voltage
Data Source
AI summary
A method and apparatus for efficiently converting power from an AC line is disclosed. The power converter supplies power to the load, performing power factor correction at nominal and high loads, i.e. above a predetermined output power threshold, and operating in an on-demand burst mode synchronized to the AC line at low loads, i.e. below a predetermined output power threshold. The duration of an operating interval during which power conversion takes place may be reduced and varied at low loads as a function of the output power demands to increase overall conversion efficiency. The operating interval may be centered about a peak in the input voltage waveshape for operating intervals that are less than a full rectification period. For operating intervals that are less than a full rectification period a modified power factor correction may be used, in which the input current waveshape approximates the input voltage waveshape during the operating interval.