As semiconductors, LEDs require a minimum voltage to be applied across their junction before current flows, generating light. This minimum voltage is commonly referred to as the threshold voltage or turn on voltage. Increasing forward current increases the flux output of the LED Array. However, the relationship between flux performance and forward current is not linear. For example, doubling forward current does not lead to the doubling of flux output. The figure shown here depicts a typical flux versus current plot. This non-linear relationship of flux vs. forward current (or LED efficacy vs. forward current) is referred to as “droop.” As shown by the graph, the LEDs become less efficient at higher driver currents. Driving an LED array at a fixed current will allow for a maintained level of efficiency.