Measuring And Managing Thermal Output In LED

- Apr 30, 2019-

This is better than a standard tungsten bulb, which dissipates more than 90% of all input energy as excess heat, but it remains a problem within the LED lighting industry. An LED system with poor heat management characteristics will degrade more quickly and provide weaker performance over time. In response to this problem, lighting engineers have made significant advances in measuring and managing heat generation in LED light systems.

Thermal Management of LED Technology

Heat generation management in an LED light is first a function of balancing the thermal resistance of the LED substrate and the thermal impedance of individual LED system components. Thermal resistance is a ratio of the thickness of an LED circuit board divided by  its conductivity. The board typically has multiple layers, comprising copper, one or more dielectric materials, and metal substrates. Engineers measure the thermal resistance of each layer and add those values to calculate the system’s total resistance. In general, LED systems with higher total resistances will generate more heat, which requires engineers to heat sinks and other cooling technology to reduce heat buildup.

Measuring individual component impedance gives engineers a tighter picture of an LED system’s thermal management requirements. Those measurements comprise adding the heat generation along all parallel and series heat pathways within a system and combining those calculations across specific areas of the LED. When engineers have determined the combined thermal resistance and impedance of a system, they can design a more precise heat sink or cooling system that allows the LED to operate at its ideal temperature without long-term degradation or performance reduction due to excess heat.

 Cooling LED Lighting Fixtures

Lighting engineers have three options to cool an LED light. The first is to cool the heat path over the light casing at the junctions to its contact pins and to the light casing itself. This option provides a minimal window for cooling, however, and it is not the most effective option.

The second option is to cool conductor paths on printed circuit boards, and the third is to cool the metal cladding on the LED printed circuit board. Both of these options involve attaching heat sinks that draw heat away from the circuit board and allow that heat to be dissipated into ambient air. The criteria that engineers develop from measurements of resistance and impedance will dictate the optimum heat sink material and configuration.