Combined wide input and high efficiency DC-DC converter
Aiming at the problem that the input voltage of the vehicle-mounted DC-DC converter varies widely,a combined wide-input high-efficiency DC-DC converter was proposed.The converter consists of two parts:a flying capacitor(FC)type three-level Buck circuit and an LLC resonant circuit.The output port of the FC three-level Buck circuit is connected in series with the input port of the LLC resonant cir-cuit.By controlling the duty cycle of the FC three-level Buck circuit,the output voltage was adjusted to adapt to a wide input voltage range.At the same time,the three-level structure reduces the voltage stress of the power switches and reduces the loss;the LLC resonant circuit transmits all the power required by the load.Using fixed-frequency and open-loop control,high efficiency and stable gain were achieved while achieving electrical isolation.The topology,DC gain and working efficiency of the combined con-verter were analyzed in detail,and the efficiency characteristics were compared with the cascaded con-verter composed of the same circuit.According to the topology and working characteristics of the com-bined converter,a decoupling control strategy was proposed to achieve output voltage stability and flying capacitor voltage balance.Finally,an experimental circuit with 200-400 V input and 12 V/20 A output was built for verification.The experimental results show correctness and feasibility of the proposed com-bined converter.
combined converterflying capacitor type three-level BuckLLCwide input voltage rangehigh efficiencydecoupling control
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