What factors affect the junction temperature of an LED?
Calculating junction temperature The efficiency of solid-state lighting devices depends heavily on the junction temperature, which in turn, primarily depends upon three factors: the applied power; the thermal resistances between the LED junction and the ambient temperature; and the ambient temperature itself.
What is the difference between junction temperature and ambient temperature?
The ambient temperature refers to the temperature of the surrounding environment (typically air) when the device is powered. The junction temperature refers to the temperature of the silicon die within the package of the device when the device is powered.
How does Junction to ambient temperature of led change?
The junction temperature decreases as the thermal flux moves from the junction to ambient. The amount of thermal resistance in the path of the thermal flux determines how quickly the flux flows measured by how much the temperature is reduced for the amount of heat generated (°C/W).
How is junction temperature calculated from the ambient?
Junction temperature (or channel temperature) can be calculated from the ambient using the following equation. *Rth (j-a): Thermal resistance of “junction-to-ambient” varies depending on the type of circuit board. For reference, provided below is the Table of Thermal Resistance by Package” based on the use of ROHMs standard circuit board.
How does junction temperature affect maximum current consumption?
When the same current is applied, the junction temperature also rises as the ambient temperature goes up. This diminishes the applicable current subsequently. Maximum current consumption is influenced by thermal resistance and the ambient temperature as well.
How is the maximum forward current of a led determined?
The maximum forward current is determined by the thermal resistance between the LED junction and ambient. It is crucial for the end product to be designed in a manner that minimizes the thermal resistance from the solder point to ambient in order to optimize lamp life and optical characteristics.