The junction temperature of aLED module directlyaffects its longevity and output quality. The conventional approach that uses the heat transfer resistance network method is inaccurate and couldn’t take into account the complex geometry of the PCBA and theheat sink. Commissioned by the Lumega Goup, Originex developed a hybrid approach, where both the macroscopic lamp CFD model and the module levelmodel in which the LED unit module geometry is modeledin detailare both considered,allowing predictionsof the junction temperatureaccurately and cost effectivelyThis tool is used for a streetlamp heat sink and overall geometry optimization.
Transient nature convection inside the entire lamp is simulated assuming a uniform heat flux boundary condition at the contact surface between the heat sink and the backside of the LED PCBA. Geometry of the heat sink and enclosure is optimized to minimize the temperature gradient between the backside of the LED PCBA and the exterior surface of the enclosure, enhancing the effectiveness of the heat sink. The obtained temperature at this surface is then used as the boundary condition in the LED module level model, where the volumetric heat generation rate is specified for each die. The junction temperature is monitoredand compared to the manufacture recommendation.
This process of design optimization is iterated until desired junction temperature is achieved.