Thermal Runaway

All semiconductors, including LEDs, generate heat as a by-product of their operation. The more power the component consumes, the more heat has to be dissipated. If appropriate thermal management is in place, the component will not exceed its maximum operating temperature.
If the provisions for heat dissipation are inadequate, overheating will occur. In this case, the ability to conduct electricity increases and even more heat is generated. The increased heat dissipation leads to an even higher temperature, which further increases the ability to conduct electricity. This process, known as thermal runaway, continues until the component self-destructs.
Thermal runaway is controlled by using a constant current controller or LED driver.