the LNK chip seems to be exactly the sort of thing you're hoping that the LED drivers would supply. A small and only marginally regulated replacement for "ye old" 60Hz transformer and DC rectification circuit, that converts AC line voltage to something appropriate for the input to Arduino-like circuits, in a hopefully cheap circuit. That's what it says in the datasheet:
LinkSwitch-LP switcher ICs cost effectively replace all unregulated isolated linear transformer based (50/60 Hz) power supplies up to 3 W output power.
dhenry is also correct that it's a gated oscillator circuit. It says THAT in the datasheet too:
Unlike conventional PWM (pulse width modulation) controllers, it uses a simple ON/OFF control to regulate the output voltage.
With the suggested circuit having 220uF of output capacitance, and probably running that gated oscillator "as needed"
A lot of the confusion seems to surround the use and mis-use of the term "constant current" WRT power supplies.
A proper LED driver should a TRUE constant-current supply, holding the current constant by varying the output voltage "quite a bit", in order to accommodate at least variations in Vf
of the LED string, and perhaps a relatively wide range of number of LEDs in series. You can see this on chips specifically designed to be LED drivers; for example the Allegro Micro LC5220 series supports Vled
of 6 to 90V in its "buck mode" configuration. (Datasheet
) Meanwhile the "CCCV" supplies are more "Constant voltage first", with some current limiting capability, and "well defined behavior" as the current increases beyond the limit (unlike, say, a 7805-style regulator.) I don't know whether these chips are designed to be operated in their constant-current "operating region"; it looks more like the CC feature is a protection mechanism. It might take a power-supply engineer to figure it out :-(
So... Does a random "LED Driver Module" do anything useful, WRT powering hobby electronics? The fact that they're advertised as "3 x 1W driver" or similar implies a pretty low output voltage range, so they're probably not "true" constant-current drivers. And there's no sign that any two supplies operate similarly, or use the same circuits. You might get lucky, or you might not, and I don't think there is any way to tell without either getting much more detailed specifications than tend to be listed on eBay, or actually buying one and analyzing the circuit and/or behavior.
Given the average level of Power-supply-design expertise of Arduino forum readers ("nil"), I find the suggestion that they might be able to use some random cheap LED-driver module from eBay as a power supply to be ... dangerous
. That's probably the reason that tempers in this thread are running a bit hot.