Abstract
Interleaved LLC resonant converters are widely used in various fields. However, interleaved LLC converters under Pulse Frequency Modulation (PFM) will lose the regulation of individual phases, causing a load sharing problem. Existing load sharing solutions have limitations; for example, phase shedding and current sharing cannot be realized at the same time. This paper proposed a novel current sharing method for interleaved full-bridge LLC resonant converters. Based on Zero-Vector-Injection, the voltage applied to the resonant tank is controlled to compensate for the difference in gain caused by component tolerance. The modulation strategy is proposed to maintain soft switching after Zero-Vector-Injection, and the phase shedding technique is also used to improve the efficiency at a light load. The detailed theoretical analysis and implementation method are proposed and validated using simulations. Experiments are also carried out to verify the feasibility of the proposed strategy based on a 2-phase 1.8 kW prototype.
Highlights
High power density and simple structure, etc., the LLC resonant converter is widely applied in electric vehicles, high-power microwave systems, aerospace power supplies, communication power supplies, Micro-Grid and UPS equipment [1,2,3,4,5,6,7,8,9,10,11,12]
The resonant frequencies of each LLC converter are always different due to component tolerance, which makes the gain of each phase different under the same switching frequency, which results in uneven current [17,18]
Loops, but its current sharing accuracy is not as high as active current sharing method. When it In Reference [27], a passive current sharing method is proposed by adding a balancing transformer is applied to the multi-phases LLC converter, the design of its balancing transformer will have certain to the LLC converter
Summary
High power density and simple structure, etc., the LLC resonant converter is widely applied in electric vehicles, high-power microwave systems, aerospace power supplies, communication power supplies, Micro-Grid and UPS equipment [1,2,3,4,5,6,7,8,9,10,11,12]. In Reference [27], a passive current sharing method is proposed by adding a balancing transformer is applied to the multi-phases LLC converter, the design of its balancing transformer will have certain to the LLC converter This method does not require additional control loops, but its current sharing difficulties, and will make the hardware of the parallel system more complicated. A new active current sharing approach for interleaved LLC resonant converters is tank can be adjusted by Zero-Vector-Injection, which is another control freedom. A new active current sharing approach for interleaved LLC resonant converters is compensate for the gain difference caused by component tolerance The voltage applied to the resonant tank is adjusted by injecting zero vectors to compensate current sharing and phase shedding can be realized while retaining soft-switching capability.
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