Прозвёл тут кое-какие измерения и посчитал, что будет, если уменьшать яркость фонаря на МС-Е с директ-драйвом путём резистора в хвосте. Извините, что на английском, но переводить это ещё раз я пока не осилю. Числа, впрочем, понятны.
I'd just measure it.
Let's take two cells - fully charged @ 4.21V and half-empty @ 3.80V. That will provide more realistic measurements. Also I have good enough DMM, and direct driven MC-E module connected to cell with wires for easer voltage measurement. I have no 6.8 Ohm resistor but I found 4.7 Ohm, efficiency will be slightly better.
Charged cell with resistor: 0.290A
Empty cell with resistor: 0.215A
Charged cell direct drive: 3.00A
Empty cell direct drive: 2.050A
Also I measured currents in WF502B host and they were almost same so wires resistance id negligible.
Charged cell with resistor: 2.76V
Empty cell with resistor: 2.73V
Charged cell direct drive: 3.55V
Empty cell direct drive: 3.35V
Voltage was measured at emitter side, not at cell. Resistor voltage drop is 1.36V and 1.01, calculated from current.
And what do we have here? At direct drive emitter power is 10.65W and 6.87W at full and empty cells. At Lo mode emitter power is 0.80W and 0.57W. Wasted power at resistor is 0.39W and 0.21W, efficiency is 67% and 73%, average 70%. It is at par with worse multi-input drivers and remember - I used smaller resistance!
So even if LED voltage/current is taken in account, resistor dimming is noticeably less effective than current or PWM, thought cheaper and simpler.
ra4hvd,
почему не обычный Li-ion?
ra4hvd
1. максимальный кпд на любой яркости
Странное какое-то утверждение 😊