Analysis And Design Of Active Clamp Flyback Converter Based On GaN

The development of switching power supplies requires that while increasing frequency and reducing volume,it can further improve efficiency.As a third-generation wide-bandgap semiconductor,GaN devices have superior performance than traditional silicon devices.The active clamp flyback topology makes use of the leakage inductance energy in the flyback converter by adding a resonant loop.Therefore,it is of great significance to study the active clamp flyback converter based on gallium nitride in low power applications.The thesis proposes an active clamp flyback switching power supply system solution based on gallium nitride devices for MHz-level high-frequency applications according to the requirements of specified functions and performance indicators.Through the analysis of the characteristics and driving methods of GaN devices,it is pointed out that when using GaN devices as the switching devices of the converter,the parasitic inductance in the drive loop should be minimized and the drive chip should be selected reasonably.Secondly,the working principle of the active clamp flyback converter in each mode is analyzed in depth.the basic relationship in the active clamp flyback converter is derived.It is pointed out that in any mode,the primary inductor current must reverse zero crossing to stabilize the ZVS of the main switch,and the ZCS of the secondary diode can be realized when the converter works in DCM mode.Therefore,when the converter works under the primary side inductor current zero crossing DCM,the overall efficiency of the converter can be improved.Then,according to the design index,working mode and GaN device working loss analysis,design and select the main device parameters of the main power circuit,and classify the control circuit at high frequency.At the same time,the PCB layout of the GaN power supply circuit,drive circuit and main power part was designed in detail.Finally,a simulation platform was built based on the Simetrix simulation software,and a closed-loop simulation of the obtained design parameters was performed to verify the correctness of the theoretical analysis.Developed prototypes and conducted experimental studies,the result shows:Within a given input voltage and load resistance dynamic range,the converter efficiency can reach up to 96.28%,and it meets the given performance index requirements and has high power density.Fully explained the correctness of theoretical analysis and design methods.