Abstract
When the full-bridge converter works under the light load condition, the power efficiency obtained by the theoretical model is much different from that of the actual converter. Facing with this situation, an improved power loss model based on the typical power loss model is proposed. In this paper, the typical power loss model is called typical model for short and the improved power loss model is called proposed model for short. Firstly, the antiparallel freewheeling diodes at the arms of full-bridge circuit are taken into account. Every barrier junction capacitance of Schottky diode in the rectifier circuit is neglected. Then, the turning-off loss of full-bridge and the core loss of inductive components (the transformer and the filter inductor) in the typical model are compensated and modified by combining the theoretical values with the measured input current under the minimum and the maximum output current. In addition, it also corrects the equivalent resistance related to the conduction loss of converter. Eventually, the proposed model is established. The rise time and fall time of the midpoint voltage of two arms, and the fluctuation degree of the reverse bias voltage related to the Schottky rectifier diodes are regarded as the local indexes. The conduction time of the metal oxide semiconductor field effect transistor (MOSFET) in each switching period, and the power efficiency of converter are regarded as the global indexes. Based on the analyses, the local indexes are compared qualitatively, while the global indexes are compared quantitatively. It is found that the differences of the local indexes between the proposed model and the experiment are smaller than those between the typical model and the experiment. Meanwhile, the global indexes of the proposed model are closer to the experimental results. Therefore, it can be further demonstrated that the proposed model is more approximate to the actual converter than the typical model.
Highlights
DC-DC converters have been paid much attention to in recent years
In the PV system, the maximum power point tracking (MPPT) methods are developed by the DC-DC converter
The full-bridge converter works under the light load condition that the filter inductor current operates in the continuous current mode (CCM)
Summary
DC-DC converters have been paid much attention to in recent years. They can be widely applied in many fields such as photovoltaic (PV) system, electric vehicle (EV) system, and so on. The power loss is mainly resulted from the switching loss and the conduction loss when the full-bridge converter works under light load condition. The AC resistance of winding at both sides of transformer and the equivalent AC resistance of filter circuit represent the overall conduction losses of full-bridge converter in the power loss model. In order to simplify the calculation of manual operation, the power loss model of full-bridge converter under light load is fully analyzed by using the Saber software. The proposed model is established by considering the antiparallel freewheeling diodes at the arms of full-bridge and ignoring the barrier junction capacitances of rectifier diodes It needs to be compensated and corrected the turningoff loss of MOSFETs, the equivalent core loss resistance of inductive components, and the equivalent conduction loss resistance of converter. Whether the proposed model is closer to the actual converter than the typical model is judged by a series of analyses and verifications
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