功率变换器风冷系统优化的仿真研究

Simulation Research on Optimization of Air-cooling System for Power Converter

针对高功率密度半导体开关器件的温升问题,研究了功率变换器的风冷系统散热性能表现,基于ANSYS ICEPAK仿真分析了热界面材料(Thermal interface material,TIM)对分立式SiC MOSFET温升以及散热器热阻的影响作用,提出了三种风道设计方案,从风机效率、降温效果、多器件温度一致性三个方面给出综合评价。研究结果表明,TIM热导率越高,SiC芯片温度越低,但温度的下降存在极限,氮化铝陶瓷垫片与常规硅胶片相比可降温约14.2%;散热器热阻与TIM热导率呈变化率递减的非线性关系,过高热导率的实际意义有限,应结合热设计成本综合考虑TIM选择;合理分配风机风量比单纯提高气流速度的散热效果更佳,混合射流的变截面双风道设计方案具备更高的风机效率以及良好的温度一致性,与无风道相比芯片温度可再次降低约13.7%,其综合表现最优。研究工作为后续开展功率开关器件的热管理试验提供了参考依据。

Aiming at the temperature rise problem of high power density semiconductor switching devices,the thermal performance of air-cooling system for power converter was investigated.The effects of thermal interface material(TIM)on temperature rise of discrete SiC MOSFET and heat sink resistance were analyzed based on ANSYS ICEPAK simulation.Three air duct design schemes were proposed.A comprehensive evaluation was given from three aspects:fan efficiency,cooling effect and temperature consistency of multiple devices.The results show that the higher thermal conductivity of the TIM,the lower the temperature of the SiC chip.The AlN ceramic gasket can be cooled by about 14.2%compared with the conventional silicone sheet and this temperature drop is limited.The simulation results show a nonlinear relationship between heatsink resistance and TIM thermal conductivity with decreasing rate of change.The practical significance of overhigh thermal conductivity is limited and TIM selection should be considered in combination with thermal design cost.Reasonable distribution of fan air volume is better than simply increasing the airflow speed.The variable section dual duct design of the mixed jet cooling provides higher fan efficiency and good temperature consistency.Compared with no air duct,the chip temperature can be reduced again by about 13.7%,and its comprehensive performance is the best.This research work provides a reference for subsequent experiments on thermal management of power switching devices.