Hello guys.
I have lots of Constant Current LED Driver like below picture:
I want to use them as a switching power supply, 5volts and 100mA.
Below picture is the IC that has been used in the Driver.
How can I use it as a switching power supply for Arduino.
Very thank you.
How convert a constant current source to constant voltage source.???
That seems difficult and a little "dangerous". What voltage do you measure with no load? How much current is it trying to "push-out"?
Do you understand the implications of [u]Ohm's Law[/u] with a constant current power supply?
It would probably be a good idea to add some over-voltage protection to your Arduino. 
Its not possible with that switcher chip, as it has no capability of stabilising the output voltage so it wont be regulated.
leoncorleone:
How convert a constant current source to constant voltage source.???
By sticking a voltage regulator on its output
mauried:
Its not possible with that switcher chip, as it has no capability of stabilising the output voltage so it wont be regulated.
Okay.But the chip has a current sense pin and senses the current with a resistor? I have to do something the cs pin senses a constant voltage in different currents . so can I change the resistor with a zener diode. Does it work?
thanks
saximus:
By sticking a voltage regulator on its output
I tried but did not work.
To be constant current that device pulls various tricks involving the nature of the transformer
magnetics / saturation curve, its optimized for driving a string of LEDs, I wouldn't expect it to play nicely for
a different use.
I just need 0.5 watts of its power. The power of driver is about 7 watts, so I do not think the transformer has any problems.
If you attach a string of LEDs, no, it won't have problems, as that is what its designed to manage.
Add some other kind of load, who knows what it will do? Remember its sensing the transformer
primary, which directly reflects the load impedance on the secondary.
The power of driver is about 7 watts
I guess it's intended to feed 4 to 7 "1W Power Leds" with constant 300 mA and 12 .. 21 V.
If the LEDs are fed in parallel to the Arduino, and these white power LEDs are not broken, you will have about 9.x Volts across three of them. This should be ok to go into Vin (and GND) of an Arduino, and will reduce the current through the LEDs only a litte bit.
But if the LEDs are missing or broken, it will hurt your Arduino.
There are devices showing 315 V DC output without load (on 230V AC input).
Guess why there's a 400V rated capacitor on the output side. No engineer spends 2 ct for nothing.
I wouldn't do it.