Constant Current Devices

[bstumm]

Can anyone point me towards some manufacturers or suppliers of low(er) cost LED Drivers for constant current? I realize the type of LED, voltage and current requirements are a factor too but just hoping to get to a place that doesn't charge an arm and a leg. Just a basic "these guys are pretty cheap" type of reply. I have searched the forums but most things I found are obviously based on a particular LED and application.

For anyone curious, I'm driving 18 LEDEngin 10W LEDs each at 15.5V and 700mA. Planning to run 3 LEDs in series from a 48V supply but am open to using a driver for each LED or a multi channel device that could power say 3 channels at 48V/700mA.

At the end of the day I'm actually going to be driving 3 segments of the 18 LEDs for total of 54 LEDs so I need a lot of constant current power... 600 Watts total approx.

 

[balou]

A simple resistor or a LM317 linear regulator in a constant current configuration could work.

 

[kmossman]

you can see the LM317 as a constant current device here;

http://diyaudioprojects.com/Technical/Voltage-Regulator/


You mentioned several different voltages - can you state the supply voltage?

The LM317, I believe has a max Vin of 40V. You can go discrete - the 2 transistor current regulator works very well.

Using resistors means getting high wattage resistors - a 3V Vd at 700mA requires at least a 5W resistor.

Keep in mind the LM317 needs a substantial delta V to work; if you need 24V out, it needs over 27V to work.

Ken

 

[J_C]

IIRC, LM317 doesn't have a 40V limit, that is just the max input-output difference it can tolerate ("Input-Output Voltage Differential" as stated in the National Semi datasheet).


According to the datasheet, at 700mA you should only need a couple volts headroom (drop across the regulator) instead of 3V or more, but that still seems too high to run a series of 3 x 15.5V from a 48V supply. Consider using an LDO regulator instead if a linear regulator is the path you decide on.