Depends on the LEDs. At 5 amps and 7 mOhms, that’s 0.035 volts being dropped. It really depends on the LED but for the sake of discussion, let’s say we’ve got a triple SST-20 4000K (this is a FW3A driver, after all).
I’ll use maukka’s data
- At 5 amps that’s 1.67 amps per emitter with a total output around 467 lumens x3 = 1400 lumens
- That’s ~3.058 forward voltage
- If the PFET dropped 0.035 volts that leaves us 3.023 volts at the LEDs now
- At 3.023 volts that’s now around 429 lumens x3 = 1287 lumens
- 1400 - 1287 = 113 lumens lost
In this example, we lost around 8% of output (assuming I did any of this correctly). Not a huge loss, but for the enthusiasts in the crowd (the target for this driver), it’s not a small loss either.