Burst Mode Control for Multiphase Power Converters
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Solution Overview
Problem
Existing switched mode power converters face challenges in reducing losses and noise during low load conditions, particularly in power factor correction circuits, due to subharmonics and ringing issues that are not effectively addressed by current burst mode routines.
Innovation Solution
A method for a switched mode power converter with a multiphase AC side that determines a block length based on the time span between changes in current-carrying conductors, allowing for blocking intervals to prevent power flow during low load conditions, thereby reducing noise and balancing current between phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high switching frequency is used to achieve power factor correction, then the power factor correction is effective, but audible noise and ringing of input filters occur
Solution Approach 1:
The patent applies periodic action by implementing a burst mode routine that operates in cycles, alternating between active power conversion periods and idle periods. This periodic operation at a lower effective frequency reduces audible noise and filter ringing while maintaining power factor correction capability through the controlled switching patterns during active periods.
2Loss of energy
If burst mode is used to reduce losses during low load conditions, then efficiency is improved, but subharmonics are generated in current or voltage signals
Solution Approach 1:
The patent employs feedback mechanisms to monitor the current and voltage waveforms during burst mode operation. Based on this feedback, the control system adjusts the timing and duration of burst periods to minimize subharmonic generation while maintaining low-loss operation during low load conditions.
3Loss of energy
If burst mode is used to reduce losses during low load conditions, then efficiency is improved, but noise and ringing problems occur
Solution Approach 1:
The patent applies periodic action by implementing a burst mode routine that operates in cycles, alternating between active power conversion periods and idle periods. This periodic operation at a lower effective frequency reduces audible noise and filter ringing while maintaining power factor correction capability through the controlled switching patterns during active periods.
4Ease of operation
If the burst length is fixed to correspond to 1/4 of each AC utility line cycle, then the control is simple, but the burst length does not adapt to variations in the input current waveform
Solution Approach 1:
The patent implements dynamics by making the burst length variable rather than fixed. The control system dynamically adjusts the burst length based on real-time detection of the input current waveform characteristics, allowing the converter to adapt to varying load conditions and maintain optimal performance across different operating scenarios.
Data Source
Figure 1a~1b
Figure 2a~2c
Figure 3a~3c
AI summary
A method for providing an output power of a switched mode power converter comprises the steps of determining a block length and, if a set value of the output power is below a first power threshold, preventing a power flow through the converter in each period of the multiphase AC voltage for at least one blocking interval. Each blocking interval has a duration of one block length. The switched mode power converter has a multiphase AC side with a number N of conductors for receiving a multiphase AC voltage. The number N of conductors is at least three. Power flows into the switched mode power converter through a combination of current-carrying conductors. The block length is defined by a time span between two subsequent changes of the combination of the current-carrying conductors.