Is there any single component to replace 8*7135s?
8 components take a lot of space on the driver board, I don't want to use FET since I need to limit the current to be around 3A.
Using 7*380mA components is not really a space saver.
It’s easy to create a constant current driver with a FET, opamp and voltage reference. And I’m sure that there are also linear constant current sinks in that range. Or use a constant current buck/boost regulator.
The device does not provide the power, it just controls it. For example FET that controls a lot more power is smaller
The electronics inside is small percent. Most of the size is package and the terminals are also huge wast of space since it is hard to solder 2 very close components.
From engineering point of view it is possible to make a 3A current limiter way smaller than 8 7135s but I am not sure it has a market.
I am out of my depth, but I have read FET can utilize two channels, one linear, one with PWM.
Also, according to maukka’s review here on the Noctigon KR4 only with E21A emitters,
…but I am unclear on whether this constant current/noPWM implementation in the Noctigon KR4 w/E21A is due to this “new type” of FET, or due to the noPWM version of Andúril it uses.
Hardest part would be to design the PCB and the choice of components. The KR4 uses a classic FET current sink controlled via an opamp.
Just because the die is small (it isn’t always small, depends on the power) doesn’t mean the rest is just for the pins. It has to sink all the heat away. That’s why power components have large thermal contact pads or several pins in parallel.
FET and PWM are different things. A FET is like a valve. You can close and open it fully and you will get no or all flow. You can open and close it fast to control the total throughput - this is PWM.
Or you open the valve only partly to restrict the flow. Just look at what comes out and open or close it a little bit more. This is a constant current regulator as used in the KR4. The downside is that the FET heats up.
AMC7135 do almost the same, but in a single package. They have a FET, a voltage reference and a resistor to measure the current. And they heat up because of the same reason.
The valve with water is a nice analogy. Opening and closing the valve very quickly causes the water hammer effect that might destroy your pipes, valves and fittings. Using PWM with a FET is similar, the high power switching causes electromagnetic noise.
Not sure what I wrote to suggest otherwise. As far as I know, FET drivers utilize PWM in nearly every light I have heard of with a FET driver, the Noctigon KR4 w/ E21A being the only exception I know of. PWM is not for its own sake, it is some other gain that is desired. Many don’t mind PWM, but it kind of sucks. My comment was to suggest to OP into looking into FET without using PWM.
To my understanding, FET as current regulator requires some kind of control loop, so by default a complected circuit with many components.
I am after the most simple and compact solution (does not have to be the most elegant) A component similar to AMC7135 but with higher current rating (single cell voltage)
What I’d really like to see is us come up with a good mid-power buck-boost similar to the Lume1 but at a lower cost and perhaps a bit more simplicity. Pipe dream, perhaps, but a guy can dream…