Research On Thermal Management And Parameter Optimization Of High Frequency Buck/Boost Converter

For power semiconductor devices installed on printed circuit boards(PCBs),it is common to drill thermal vias at the PCB board close to the devices and add heat sinks at the bottom of the PCB board to promote heat diffusion of the heat source device.The size and layout of the thermal vias,as well as the shape of the heat sinks,will affect the heat diffusion band of the heat source device.This article provides a detailed analysis of the effects of different parameters of thermal vias on the thermal resistance of PCB boards,as well as the effects of substrate thickness,fin length,fin spacing,and fin thickness of heat sinks on the performance of heat sinks,in order to optimize heat dissipation design.The main research content of this article is as follows:Firstly,design a 1MHz Buck/Boost circuit with a 380-400 V input,100V-200 V output and 200 W rated prototype is built.The power semiconductor devices and driver chips of the circuit are selected,and the driver circuit is optimized to reduce the probability of Gallium Nitride(GaN)misoperation;Analyze the conditions for realizing soft switching in the circuit.Optimize and analyze the inductance,determine the appropriate Litz wire diameter,magnetic core air gap,and the relationship between coil turns.Analyze the losses of the main loss devices in the circuit,including the switch transistor and inductance.Secondly,based on the theory of heat transfer,the main influencing factors of the heat transfer path and key fixed point temperature of the heating device were analyzed.Based on the characteristics of GaN,the inherent losses and temperature rise were analyzed,demonstrating the necessity of GaN thermal design.By establishing an equivalent thermal resistance network model for PCB and heat sink,the influencing factors of PCB and heat sink thermal resistance values were analyzed based on the three basic modes of heat transfer: thermal radiation,thermal convection,and thermal conduction,as well as their calculation formulas,and calculate their specific thermal resistance values.Based on thermoelectric analogy,solve the temperature of the heat source using the node temperature method.Use thermal simulation software Icepak to simulate and verify the import of PCB models.Secondly,based on the theory of heat transfer,the main influencing factors of the heat transfer path and key fixed point temperature of heating devices were analyzed.Based on the characteristics of GaN devices,the situation of their own losses and temperature rise was analyzed,demonstrating the necessity of thermal design for GaN devices.By establishing an equivalent thermal resistance network model for PCB and heat sink,the influencing factors of PCB and heat sink thermal resistance values were analyzed based on the three basic modes of heat transfer: thermal radiation,thermal convection,and thermal conduction,as well as their calculation formulas.The specific thermal resistance values were calculated.Based on thermoelectric analogy,the node temperature method was used to solve the heat source temperature.Use thermal simulation software Icepak to simulate and verify the import of PCB models。Then,optimize and analyze the overall circuit’s heat dissipation.Optimize the design of the PCB board’s substrate,heat dissipation thermal vias layout mode,copper plating thickness,heat dissipation thermal vias size,heat sinks type,substrate thickness,fin width,fin height,fin spacing,etc.Determine the heat dissipation plan based on the above analysis.Finally,based on the above analysis,the thermal vias and heat sink information of the PCB is determined.The correctness of the theoretical analysis is verified through thermal simulation of the thermal vias and heat sink.Through experimental testing and analysis of the experimental results,the correctness of the circuit design is verified,effectively ensuring safe and stable operation of the circuit,and avoiding thermal imbalance in GaN temperature.