LLC Converter Burst Mode Sleep Time Adjustment
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Solution Overview
Problem
LLC converters experience efficiency drops and acoustic noise issues during light load conditions due to transient load operations, as they operate at maximum switching frequency and dissipate significant energy, compromising both efficiency and acoustic performance.
Innovation Solution
A system and method that generate a switching signal with burst and sleep times for LLC converters, adjusting the sleep time to maintain constant output power during burst mode operations, balancing efficiency and acoustic performance by calculating the sleep time based on output load current and voltage, thereby optimizing duty cycles and reducing audible noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LLC converter operates at maximum switching frequency under light load conditions, then power delivery responsiveness is improved, but efficiency deteriorates due to significant energy dissipation
Solution Approach 1:
The patent implements burst mode operation where the converter switches between active burst periods and sleep periods. During burst periods, the converter operates at maximum switching frequency to deliver power rapidly. During sleep periods, switching is reduced or stopped to minimize energy dissipation. This periodic alternation between high-activity and low-activity states resolves the contradiction by achieving both fast power delivery responsiveness and low energy loss under light load conditions.
2Power
If LLC converter operates at maximum switching frequency under light load conditions, then power delivery capability is improved, but acoustic noise increases above audible threshold
Solution Approach 1:
The burst mode operation creates periodic switching activity with defined burst durations and sleep intervals. By controlling the duty cycle and timing of these periodic bursts, the converter maintains adequate power delivery capability while the intermittent nature of operation reduces continuous acoustic noise generation. The sleep periods allow mechanical vibrations to subside, thereby mitigating audible noise while preserving power delivery capability during active bursts.
3Loss of energy
If burst time is extended to maintain constant output power, then efficiency is improved, but acoustic noise increases above minimum audible threshold
Solution Approach 1:
The patent dynamically adjusts both burst time and sleep time based on load conditions and efficiency requirements. The controller monitors converter efficiency and acoustic noise levels, then adaptively modifies the burst mode parameters. When efficiency needs improvement, burst time is extended; when acoustic noise approaches audible thresholds, sleep time is increased or burst power is reduced. This dynamic parameter adjustment resolves the contradiction by optimizing the trade-off between efficiency and acoustic noise in real-time.
Solution Approach 2:
The controller changes operational parameters (burst time, sleep time, duty cycle) to maintain efficiency while controlling acoustic noise. By varying these parameters based on monitored conditions, the system can operate at optimal efficiency points without consistently exceeding audible noise thresholds, thus resolving the contradiction between efficiency improvement and noise mitigation.
Data Source
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AI summary
In described examples, a system (100) includes an LLC converter to convert an input DC voltage to an output DC voltage. A burst generator (120) generates a switching signal having a burst time and a sleep time to operate the LLC converter (110) when output load current of the LLC converter (110) is below a predetermined threshold. A burst power calculator (140) adjusts the sleep time for the switching signal, such that output power of the LLC converter (110) during the burst time is held substantially constant with respect to changes in the output load current.