Study On Active Cooling Devices Based On Piezoelectric Actuators For High Power LEDs

LED(Light Emitting Diode)as the fourth generation light source has the advantages of small size,low energy consumption and long life.With rapid development of the LED lighting industry,the power and integration levels of LEDs have been increasing.As a result,the heat generated by LED packages also increases significantly.How to effectively reduce the chip junction temperature has become one of the important research problems in the LED industry.Piezoelectric fan is a new type of heat dissipation device,which has the advantages of small size,simple structure,low power consumption and low noise,etc.In this study,theoretical,simulation and experimental methods are used to carry out systematic research on piezoelectric fans.The specific research contents are as follows:(1)Vibration characteristics of the piezoelectric fan.Based on the piezoelectric theory and the vibration theory of the cantilever beam,the coupling relation between the piezoelectric parameters was analyzed,and the functional expressions of the natural frequency and the natural mode of the piezoelectric fan were obtained.The natural frequency and vibration amplitude of the piezoelectric fan were further computed by modal and harmonic responses of the fan using ANSYS Workbench software.Effects of the important parameters of each component of the piezoelectric fan on the vibration characteristics of the piezoelectric fan were studied.Finally,a corresponding experimental platform was built to measure the natural frequency,vibration amplitude,pressure and flow speed generated by the fan tip.The accuracy of the simulation was verified by comparing the experimental,analytical and simulation results.(2)Heat dissipation performance of piezoelectric fans.The heat dissipation performance of the cooling system composed of piezoelectric fans was analyzed by computational fluid dynamics(CFD)software FLUENT.In FLUENT,user defined functions(UDF)and dynamic grid technology were used to analyze the influence of plate shape,array mode,array spacing,distance between fan and heat source and other parameters on heat dissipation performance.The corresponding experimental platform was built to investigate the rectangular piezoelectric fan.The experimental and simulation results provided useful guidelines for future commercial applications of the piezoelectric fan.(3)A new type of embedded radiator structure based on combination of the piezoelectric fan and a heat sink.The heat dissipation process was simulated by FLUENT software,and influences of the number of piezoelectric fans and the vibration phase of fans on the entire device were analyzed.The combination form with superior heat dissipation performance was obtained.The simulation results were compared with experimental measurements on one of the radiators.The performance of the radiator for cooling high-power LEDs was further investigated to provide a benchmark for applications of combined piezoelectric fans and heat sinks in LED lighting systems.