System dynamics model of high-power LED luminaire

Optical properties of LEDs are sensitive to junction temperature. From the principle of solid-state lighting, the luminance of LED is induced from two physical mechanisms: energy effect and optoelectronic effect. Both effects are related to junction temperature. The understanding of system dynamic behavior in junction temperature is quite important for lighting control design. The system dynamics model of a high-power LED fixture for energy effect was derived and identified in the present study using step response method. Both theoretical and experimental analyses have shown that the thermal system dynamics model of the LED fixture is 4th-order with three zeros and can be reduced to a first-order biproper system. The instantaneous jump of junction temperature dominates the thermal behavior of LED at the beginning of the step input. The optoelectronic effect was induced mainly from the current input and the junction temperature. Combining the two physical effects, an electric-heat-optical system dynamics model of LED luminaire was finally proposed which is the basic system dynamics model for LED luminance control.