Multi-Phase LLC Converter Control for Wide Voltage Range
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Solution Overview
Problem
Conventional multi-phase converters have limited voltage ranges, asymmetric current profiles, and efficiency is constrained by practical switching frequency limits, particularly in light-load operations.
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-modification operation mode that reduces the operating phase, allowing for symmetric currents and increased efficiency without increasing switching 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 where the secondary side circuit is shorted periodically within each switching time period T. This periodic shorting creates voltage boost effect without requiring continuous high-frequency switching, thereby maintaining efficiency while expanding the voltage range. The periodic nature of this operation allows the converter to achieve variable voltage gain while operating at optimal switching frequencies.
2Ease of operation
If conventional control methods are used, then converter operation is simple, but current symmetry deteriorates resulting in half-wave asymmetry
Solution Approach 1:
The patent applies dynamics by introducing a phase-modification operation mode that dynamically adjusts the number of operating phases based on the desired output voltage. The controller can switch between different phase configurations (e.g., three-phase, two-phase, single-phase operation) to maintain current symmetry across different operating conditions. This dynamic phase adjustment ensures symmetric current waveforms while preserving control simplicity through a unified control framework.
3Power
If all primary switches operate simultaneously, then power output is maximized, but voltage control flexibility deteriorates at light-load operations
Solution Approach 1:
The patent applies segmentation by dividing the converter operation into distinct modes: a boost operation mode for voltage enhancement and a phase-modification operation mode for phase reduction. The controller segments the switching control such that during phase-modification mode, only subsets of primary switches operate simultaneously rather than all switches. This segmentation allows flexible voltage control at light-load operations while maintaining the ability to deliver full power when all phases operate together.
Data Source
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AI summary
The invention concerns a control method for operating a multi-phase converter (1) with a number N of phases, N being at least three, said converter (1) comprising a transformer (2), a primary side circuit (3) which comprises primary switch legs (4) with primary switches (5) connected to a primary side (6) of the transformer (2), and a secondary side circuit (7) which comprises secondary switch legs (8) each with at least one secondary switch (9) connected to a secondary side (10) of the transformer (2), the number of primary and secondary switch legs (4, 8) respectively corresponding to a number of phases of the multi-phase converter (1), the control method comprising: a boost operation mode comprising a shorting step of shorting the secondary side circuit (7) by controlling a plurality of secondary switches (9) of separate secondary switch legs (8) to be simultaneously ON, wherein said shorting step is repeated periodically within one switching time period T; and/or a phase-modification operation mode comprising a phase-reduction step of reducing an operating phase of said converter (1) by controlling all primary switches (5) of at least one primary switch leg (4) to be simultaneously OFF, wherein said primary switch leg (4) is defined as OFF-leg and the other primary switch leg(s) (4) is/are defined as operating leg(s), and wherein the primary switches (5) of operating leg(s) receive a pulse pattern. The invention also concerns a multi-phase series resonant converter (1) and a multi-phase LLC resonant converter (101).