Interleaved LLC Converter Duty Cycle Control for Power Balancing
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Solution Overview
Problem
Interleaved LLC converters connected in parallel at both the input and output sides face challenges in balancing power transfer due to component tolerances, leading to inefficiencies and potential operational failures.
Innovation Solution
The method involves operating each leg of the bridge inverter of the first LLC converter with a duty cycle of 0.5 and at least one leg of the bridge inverter of the second LLC converter with a duty cycle different from 0.5 to balance power transfer, without requiring additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all LLC converters are operated with a duty cycle of 0.5 at the same frequency, then the control is simple and symmetric, but power transfer becomes unbalanced due to component tolerances
Solution Approach 1:
The patent applies asymmetry by operating different LLC converters with different duty cycles. Specifically, the first LLC converter operates with a duty cycle of 0.5 while the second LLC converter operates with a duty cycle different from 0.5 (e.g., 0.4 or 0.6), creating an asymmetric control strategy that compensates for component tolerances and achieves power transfer balancing between the parallel converters.
2Reliability
If duty cycle is varied to balance power transfer, then power balancing is achieved, but control complexity increases
Solution Approach 1:
The patent applies local quality by selectively applying different duty cycles to specific converters based on their individual power transfer characteristics. The controller monitors the power transfer of each LLC converter and adjusts the duty cycle of individual converters (e.g., setting D1=0.5 and D2≠0.5) to achieve local power balancing without requiring complex system-wide control adjustments.
3Reliability
If component tolerances are reduced to achieve better matching, then power transfer balancing improves, but manufacturing cost increases
Solution Approach 1:
The patent applies parameter changes by modifying the operating duty cycle parameter of the LLC converters to compensate for component tolerances. Instead of requiring tightly matched components, the system changes the duty cycle parameter (e.g., from 0.5 to 0.4 or 0.6) to achieve power transfer balancing, thereby avoiding the need for expensive precision components or complex passive balancing circuits.
Data Source
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AI summary
An interleaved LLC converter arrangement includes two or more LLC converters for transferring power from an input side to an output side, wherein the two or more LLC converters include a first LLC converter and a second LLC converter connected in parallel on the input side and on the output side and wherein each LLC converter includes a bridge inverter at the input side. For balancing the power transfer among the LLC converters if for example the second LLC converter transfers more power from the input side to the output side than the first LLC converter, each leg of the bridge of the bridge inverter of the first LLC converter is operated with a duty cycle of 0.5 and at least one leg of the bridge of the bridge inverter of the second LLC converter is operated with a duty cycle different from 0.5.