This derating curve is taken from the Smarts Power VT series data sheet. It shows that in ambient temperature of 60 degrees Celsius, the load on the LED driver cannot exceed 60% of its maximum loading limitation, for example, you had better carry with the total wattage of led bulb no more than 14.4Watt with one 24watt led driver under 60 degrees Celsius ambient temperature.
Like all electronic devices, the higher temperature of the LED driver in, the less efficient it provide. This means at higher temperatures you may need to reduce the load on the LED power supply. If the derating of the power supply has not been taken into consideration, they still will be overloading, even though the carried load may be less than the maximum power output rating. In a word, we recommend user leave a room of 20% of the LED drivers maximum rating to give the item a buffer.
To learn more about how does ambient temperature effect led driver.
