Research On High Performance MHz Level DC-DC Converter

Switching power supply has the advantages of small size,light weight,high efficiency and good stability.It is widely used in all kinds of electronic equipment.With the development of modern electronic equipment to miniaturization and light weight,the efficiency and power density of switching power supply have higher requirements.Due to the restriction of some electronic components,the further improvement of power density is restricted.This paper studies the isolation type high power density and high efficiency converter from several aspects,such as soft switching technology,magnetic integration technology,plane transformer technology and so on.Firstly,the suitable topology is selected.By comparing several commonly used isolated DC-DC power supply circuit topology structure,we choose flyback topology and confirm the continuous operation mode of inductance current.The active clamp mode is adopted to suppress the peak voltage of transistor and achieve zero voltage switching(ZVS).The working principle of high side active clamp flyback converter is analyzed,and the condition of realizing soft switching is calculated.The active clamp current mode control chip LM5026 is selected,and its peripheral circuit is designed.Secondly,a new type of Ga N switch device is used.GaN material transistor has obvious advantages in high speed switch and low on resistance.It doesn't need heat dissipation device to improve the power density of converter.In view of the narrow and low threshold range of the GaN transistor driving voltage,the GaN transistor special drive chip LM5113 is selected.The drive circuit with independent push-pull output can drive the GaN switch reliably.Finally,the planar transformer technology is used.The planar structure has larger heat dissipation area,which can reduce the hot spot of components and the thermal resistance of magnetic components.After the preliminary design,the leakage and loss of the planar transformer are simulated in the magnetic element design software Ansoft Pexprt and the finite element analysis software Maxwell 2D.According to the simulation design,the layout of the printed circuit board of the transformer is arranged.The leakage loss is tested and calculated,and the correctness of the design of the planar transformer is verified.The leakage inductance is applied to the resonance of active clamp to achieve magnetic integration and further improve the power density.A prototype of isolated switching power supply with input 24V,output 5V/6A,operating frequency of 1MHz,40mm*25mm*6mm,efficiency higher than 80%and power density of 5W/cm~3,is developed.The experimental results and analysis verify that the prototype is a high power density switching power supply with small size,light weight and good electromagnetic compatibility.