Development Of A 3kW Wide Range Input Communication Power Supply Based On LLC

DC/DC converters are often required to operate over a wide input voltage range,such as photovoltaic,wind energy,energy storage and electric vehicle charging stations.However,conventional LLC resonant converters have limitations in their gain characteristics and do not work properly in wide range input scenarios.In order to solve the adaptation problem of LLC resonant converter in wide range input,various researches have been conducted,mainly in terms of circuit structure and control strategy.Some studies use pre-stage or post-stage conversion and to improve the characteristics of the LLC resonant converter,using the method of changing the primary circuit structure may involve more complex circuit design and more devices,thus increasing the cost and losses.While the method using a combination of frequency conversion control strategy and phase shift control strategy can expand the input voltage range,this method may require higher computational and control complexity,which leads to lower system efficiency.In this paper,a full-bridge-half-bridge control strategy is studied,based on a full-bridge LLC resonant converter,which can adapt to a wide input voltage range and maintain high efficiency by smoothly switching the topology between the full-bridge and half-bridge to achieve a stable output voltage.This method has important practical significance and engineering value,and can be widely used in power conversion systems.First,this paper compares and models a full-bridge LLC circuit and a half-bridge LLC circuit.The resonance parameters of LLC under wide range input are designed,the efficiency of LLC circuit is analyzed and the optimal switching point is proposed.Secondly,this paper analyzes the implementation method of the full-bridge and half-bridge control strategy,including the control circuit and hardware design.The control circuit uses the PID control algorithm based on DSP control chip and the frequency and duty cycle full-bridge-half-bridge control strategy,and realizes the online adjustment of switching frequency and duty cycle.The flow chart of the control strategy and the configuration of the digital control system are also presented.Finally,the experimental verification of the designed LLC resonant converter is carried out to prove the stability of the LLC resonant converter under the full-bridge-half-bridge control strategy and to verify the effectiveness of the proposed control algorithm and hardware design.These results provide valuable reference and guidance for the practical application of the LLC resonant converter.