Study On The Influence Of Distributed Capacitance On The Characteristics Of High Frequency Transformer

The large-scale application of high frequency transformer has emerged in recent years with the rapid development of power electronics technology.Because of the small size,light weight and high efficiency of the high frequency switching power supply,all kinds of high-frequency switching power supply have been widely used.The high frequency transformer is the key component of the electric energy conversion.It plays an important role in the switching power supply,such as voltage conversion,circuit isolation and energy transmission.However,with the continuous improvement of the switching power supply frequency,the influence of the distributed capacitance of the transformer on the circuit can not be ignored.The switching frequency of the switch is very high,which results in the rapid change of the energy inside the transformer.Under the influence of the distributed capacitance,it is easy to form large instantaneous over current,resulting in the loss and damage of the power device in the circuit.Moreover,the distributed capacitance can easily vibrate with inductance in the circuit and form new electromagnetic interference,thus affecting the performance of the power supply.Therefore,it is of great practical significance to study the influence of distributed capacitance on high frequency transformer.In this paper,the distributed capacitance of the high frequency transformer is looking as the research object.And this paper is focusing on the influence of how to calculate the distributed capacitance and distributed capacitance effect on high frequency transformer power transmission and the distributed capacitance influence of the switching power supply of the three aspects.First of all,from the high-frequency transformer equivalent circuit,electromagnetic equation two aspects of high-frequency transformer analysis,listed the high-frequency transformer matrix equation,which making a theoretically understand of the high frequency transformer operation principle.Secondly,in view of the shortcomings of the Parallel plate capacitance calculation formula existed.A new formula is proposed which is for calculating the distributed capacitance of circular wire windings with small interlayer spacing.From the point of view of electrostatic field energy,the energy calculation is carried out with two adjacent wires as the basic unit.Design experiment and finite element simulation,through the comparison of measured data,simulation data and calculation data,verify the accuracy of the calculation formula.And the new formula is become a powerful complement to the calculation formula of parallel plate capacitance.Thirdly,the transformer prototype is made and the equivalent circuit parameters of the actual prototype are obtained.The simulation of the equivalent circuit of the high frequency transformer under no-load condition is carried out by using Simulink simulation software,and the influence of the distributed capacitance on the energy transmission of the transformer is analyzed.Finally,the flyback switching power supply is taken as an example to analyze the influence of distributed capacitance on the operation of the circuit.In this paper,a flyback switching power supply is designed and fabricated,and the currents spike of the primary winding of the transformer are measured with different distributed capacitance parameters flyback transformers.The simulation results of the Simulink simulation software are also given to illustrate the influence of the distributed capacitance on the operation of the circuit.