| With the development of electric vehicles,the demand of high-performance converters with wide-range output and large output power has been promoted.For the charging applications with large output power,the DC-DC converter based on SiC devices can be more easily to meet the requirement of high efficiency and wide voltage-gains than those complex converters based on Si devices.This paper mainly focuses on the research of DC-DC converter with wide-range output based on SiC devices.Firstly,a modified LLC converter with the hybrid structure of voltage-multipliers has bee proposed for the quick-charging applications with cars.Through the split of the secondary rectifying structure of full-bridge,the proposed converter has a novel operation mode,and can achieve the voltage gains of 2.5 times.The on/off of secondary switch can change the proposed converter between the hybrid rectifying mode and voltage-double mode.The operation principle and characterisctics of the proposed converter have been analyzed in detail.During the whole load range,the primary switches can achieve ZVS turn-on.And in different operation modes,the transformers have different power-distribution.In addition,the parameter design of the proposed converter has been studied.After the comparison,it's more appropriate to place the second resonant inductor on the outside than to be integrated into transformers.Secondly,according to multi-branch recombination optimization method,another modified LLC converter with the hybrid structure of voltage-multipliers for the voltage gains of 3.75 times has bee proposed.The operation principle and characterisctics of the proposed converter have also been analyzed in detail.And its design has been studied with an example.Compared with conventional three level LLC converters,the proposed converter has increased the efficiency obviously.Prototypes based on SiC devices are built with experimental results in detail to verify the analysis mentioned above,respectively. |
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