Research Of Current Output Characteristics And Implementation Of ZCS Based On LCC Resonant Converter In The Full Gain Range

Electromagnetic launcher want to achieve high power output in a very short time.The power supply system must be able to achieve energy storage and rapid release to complete output power amplification of the input power.Currently,in many energy storage methods,capacitor energy storage is the most commonly used energy storage method for power supply system.In this paper,the high voltage charging power of capacitor energy storage is studied,and seeks new ways to improve the output characteristics of the power supply under the condition that the existing topology and the converter capacity remain unchanged.Firstly,the working process of LCC resonant converter dual-pulse and single-pulse output mode is analyzed.Through the analysis of the equivalent circuit model in each stage under different modes,the segmentation expressions of key variables in each stage are obtained.The characteristics of resonant frequency and output average current are discussed using the relational equations.Based on the relationship between the resonant frequency and the switching frequency,a critical discontinuous control scheme is proposed.The current output characteristics of the critical discontinuous control scheme and the traditional fixed frequency control scheme are studied.In the occasion where the constant current output characteristic and the output voltage linearity are required to be higher,a constant current output is realized by introducing a closed loop control of the output average current.Secondly,the small change of the output voltage during the switching period allows the power supply to operate in the double-pulse mode with high-precision linear charging.For the leakage phenomenon of the storage capacitor,the single-pulse mode is used for trickle charging to stabilize the output voltage and increase the stability of pulse to pulse repeatability.The realization conditions of soft-switching are studied,and the method of on-line adjusting the driving pulse width is proposed to realize the soft-switching in the full-gain range.In the specific realization of variable frequency and variable width,a piece-wise linear approximation algorithm based on digital control is proposed.By tracking the critical discontinuous switching cycle,the critical discontinuous control and the full-gain range soft switching is realized.Once again,the hardware and software design of the charging power supply was completed.The parameters of the resonant tank were calculated using the design index of the power supply.The parameters of the resonant tank directly used the parasitic parameters of the transformer to realize the integrated design of the resonant tank and the transformer.According to the current and voltage stress requirements of the switching device in the circuit,the main circuit device is selected reasonably.In order to ensure the safe and reliable operation of the system,over-voltage and over-current protection circuits are designed in the control system.Finally,the feasibility of the theoretical analysis and the proposed control scheme are verified by simulation and experiments.The experimental results show that the critical discontinuous control of resonant current and zero current soft switching in full gain range is achieved using a piece-wise linear approximation algorithm.The current output characteristics of the power supply are improved under the critical discontinuous control mode.At the same time,trickle charge is achieved by changing the input voltage and the introduction of output voltage closed-loop control.The experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed control scheme.