Research On Small Power High Power Density DC-DC Converter

DC-DC converter is widely used in various types of electronic devices.The tends of small power DC-DC converter is high frequency and miniaturization.The power density is difficult to be further improved by the restriction of some components.In this paper,isolated high-power density converter research is researched from the four ways:First,circuit topologyFlyback converter is selected by several commonly used isolated output switching power supply circuit topology comparison and analysis.Through the analysis of its working principle and working mode,we select the Discontinuous Current Mode.According to the performance index of DC-DC converter,the key components of the main power circuit are calculated and selected.Second,improve the switching frequencyHigh frequency can reduce the volume of magnetic components,the work frequency of the switch tube would be a 500 kHZ.The LM5022 control chip with 2MHz peak current control mode is selected,and the design and control mode of the chip peripheral circuit are introduced in detail.Flyback converter in the high-frequency shutdown,will have a large peak voltage,and RCD absorption circuit can ensure safe and reliable work of the switch tube.Third,the use of GaN switching devicesGaN material has the advantages of small on-resistance,less gate charge,less reverse recovery charge and minimal package,which has obvious advantages in high-speed switching and low on-resistance,and it is applied to high power density field.For the characteristics of GaN transistor drive voltage narrow,the single transistor dedicated single-chip driver chip LM5114 is selected,and the design of the independent push-pull output drive circuit can reliably and reliably drive GaN switch tube.Last,using a planar transformerThe planar structure of the core element has a large heat dissipation area,reducing the thermal resistance of the component hot spot and the magnetic element,and improving the power density.This paper summarizes its design steps and production methods.Through the flyback high-frequency transformer detailed design process,designed a plane transformer efficiency of 98.012%,whose size is 18 ×10× 6mm3.Through the above four ways,developed a 24 V input,5V / 5A output isolated DC-DC converter,whose size is 34 × 18 ×6mm3 and the power density is 6.8W / cm3 with the operating frequency of 500 kHz.The prototype of high power density DC-DC converter is small size,light weight,and good electromagnetic compatibility.