Multi-Phase LLC Converter Control for Wide Voltage and Symmetric Currents
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Solution Overview
Problem
Conventional multi-phase converters face limitations in voltage range, asymmetric current profiles, and efficiency due to frequency constraints, especially when operating at lower voltages or light loads.
Innovation Solution
A control method for multi-phase converters that includes a boost operation mode with periodic shorting of the secondary side circuit and a phase-reduction mode to adjust operating phases, allowing for symmetric currents and improved efficiency by storing energy in resonant inductors and reducing operating frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switching frequency is increased to meet lower voltage requirements, then voltage range is improved, but efficiency deteriorates due to practical limits of switch characteristics
Solution Approach 1:
The patent applies periodic action by implementing a boost operation mode that periodically shorts the secondary side circuit within each switching time period. This periodic shorting allows the converter to achieve voltage boosting without requiring continuous high-frequency switching, thereby maintaining efficiency while expanding the voltage range. The periodic nature of this operation enables the system to operate at lower frequencies while still achieving the desired voltage conversion ratio.
2Ease of operation
If conventional control methods are used, then converter operation is simple, but current profiles become asymmetric causing half-wave-asymmetry
Solution Approach 1:
The patent deliberately introduces asymmetry in the control strategy to achieve symmetry in the current profiles. By implementing phase-reduction operation mode where specific primary switch legs are controlled to be simultaneously OFF while others operate, the system creates asymmetric switching patterns that result in symmetric half-wave current profiles. This approach maintains control simplicity while achieving the desired current symmetry through carefully designed asymmetric switching sequences.
3Adaptability or versatility
If switching frequency is increased for light-load operation, then voltage requirements are met, but frequency increases are limited by switch characteristics
Solution Approach 1:
The patent applies dynamics by implementing a dynamic operation mode that can switch between different phase configurations. The system dynamically adjusts the number of operating phases based on load conditions and voltage requirements. During light-load operation, the system can reduce to fewer active phases while maintaining appropriate switching frequencies within the capabilities of the switch characteristics, thereby achieving voltage adjustment without exceeding frequency limits.
4Ease of operation
If conventional modulation techniques are used, then control is straightforward, but gain-value cannot exceed one limiting voltage conversion
Solution Approach 1:
The patent applies parameter changes by introducing a boost operation mode that fundamentally changes the operating parameters of the converter. By periodically shorting the secondary side circuit and implementing phase-reduction modes, the system achieves voltage conversion ratios greater than one. This parameter change approach maintains relatively straightforward control through modified modulation techniques while significantly expanding the voltage conversion capability beyond the conventional gain-value limit of one.
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 method enhances voltage range, achieves symmetric currents, and increases efficiency by preventing saturation and reducing frequency demands, while protecting the converter from damage.
Implementation Method 1
a shorting step in a boost operation mode, comprising shorting the secondary side circuit by controlling a plurality of secondary switches of separate secondary switch legs to be simultaneously ON, wherein the shorting step is repeated periodically within one switching time period T
Data Source
AI summary
The disclosure concerns a control method for operating a multi-phase converter with a number N of phases, N being at least three, said converter including a transformer, a primary side circuit which includes primary switch legs with primary switches connected to a primary side of the transformer, and a secondary side circuit which includes secondary switch legs each with at least one secondary switch connected to a secondary side of the transformer, the method including: a boost operation mode including a shorting step of shorting the secondary side circuit by controlling a plurality of secondary switches of separate secondary switch legs to be simultaneously ON, said shorting step is repeated periodically within one switching time period T; and/or a phase-modification operation mode including a phase-reduction step of reducing an operating phase of said converter by controlling all primary switches of at least one primary switch leg to be simultaneously OFF.