LinkSwitch-LP switcher ICs cost effectively replace all unregulated isolated linear transformer based (50/60 Hz) power supplies up to 3 W output power.
Unlike conventional PWM (pulse width modulation) controllers, it uses a simple ON/OFF control to regulate the output voltage.
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.
Go back and look at the very first page and the first few posts. With the exception of Lefty, all the posts are insulting and sarcastic.
Did it ever occur to you that it really **IS** a stupid idea to connect cheap unapproved devices to your power mains? Save $2, burn down the house.
Straight out, it is unlikely something like this can be used for a device needing a constant voltage.The topology, however, is likely a fly-back smps - assuming that it is isolated. That means the led string is floating above a current sampling resistor that controls the output voltage to maintain that constant current (thus constant voltage over the current sampling resistor - likely via a zener + optocoupler).So all you need to do is to identify that resistor and put in place a divider. That resistor is very easy to identify: it must be between the cathode (led-) and the ground.After that, you have turned this constant current regulator to a constant voltage regulator.