10 reasons that may cause LED drivers to fail
Basically, the main function of the LED drive is to convert the input AC voltage source to an output voltage that varies with the LED
Vf (current source of positive conduction voltage drop). As a key component of LED lighting, the quality of LED drives directly affects the reliability and stability of the whole luminaire. In this paper, from the LED driver and other related technologies and customer application experience, sorting and analysis of lamps design and application of many failures:
1, without considering the change range of LED lamp Vf lamp, led to low efficiency, even instability
LED light load end, usually by a number of LED series parallel connection, its operating voltage Vo=Vf*Ns, where Ns represents the number of LED series. The Vf of LED varies with temperature. Generally, at constant current, Vf decreases at high temperature and Vf increases at low temperature. Therefore, when the high temperature, LED lamp load voltage corresponding to VoL, low temperature, LED lamp load voltage corresponding to VoH. In selecting the LED drive, you should consider the driver output voltage range of greater than VoL~VoH.
If the LED driver selected the maximum output voltage is lower than VoH, may lead to the maximum power at low temperature lighting is not up to the actual power required, if the LED driver selected the lowest voltage higher than VoL, the output may drive beyond the scope of work is high, the work is not stable, the lamp will be flashing etc..
But considering the overall cost and efficiency, we should not blindly pursue the ultra wide output voltage range of LED drives: the drive efficiency is the highest because the drive voltage is only in a certain range. Over the range, the efficiency and power factor (PF) will be worse, and the driver output voltage range is too wide, which will lead to higher costs and efficiency can not be optimized.
2 、 not considering the power margin and derating requirements
Generally, the nominal power of a LED drive refers to the data measured under rated and rated voltages. Considering the different customers have different applications, most of the LED drive power supply will provide in their product specifications on derating curve (common load vs temperature derating curve and load vs input voltage derating curve).