I am fairly new to the world of LEDs and electronics in general, so I apologize for my ignorance in advance. After browsing the forum for a while and reading a few articles I have come to believe that the forward voltage of an LED is the minimum voltage it must be driven at in order to produce light. I am currently looking to buy a Nichia 219A and perform an LED swap on one of my AAA lights, however the datasheet suggests that the forward voltage is 3v. I find this puzzling since I have another light which uses an AAA battery to drive a Nichia 219B which also appears to have a high forward voltage. Evidently I am missing something elemental and must appeal to you fine fellows for elucidation.
The Vf of any led varies with current. Data sheets will list it for a specific current but usually also show a graph of voltage vs current. Boost driver raise a low input voltage to Vf for a set current and buck drivers lower a high input voltage to Vf for the set current. Linear drivers have same input and output current and burn off excess voltage as heat. Boost drivers have higher input current than output current and buck drivers have lower input current than output current.
I thought this might be the case, but now I must ask a profoundly stupid follow up question. My understanding is that the current drawn is determined by the circuit (in this case principally the LED + driver as I understand it) and the voltage is determined by the power source (AA battery). Voltage from what I have read is analogous to water pressure, so how is it possible for an electrical circuit (the driver) to amplify the voltage (i.e “water pressure”)? What would be the analogue of this in the hydraulic analogy? Also, what effect would this have on the current would it diminish it?
Think of it in terms of wattage supplied. To get 3V @1A from a 1.5 V cell a boost driver draws more than 2A from the cell and uses an inductor to convert the extra current into more voltage. There isn’t a hydraulic analog since there flow is the constant but a pressure washer is the closest thing to it where low pressure/slow speed becomes high pressure/high speed. The water flow in still equals the water flow out though. In electronics it’s the energy that’s conserved, not voltage or current.
and must appeal to you fine fellows for elucidation.