I am reading the following on an LED spec sheet.  Under electrical, it reads  "LED is 3W. 50,000 hour LED life, 700mA constant current Power Supply. LEDs must be wired in series."  I want to select a driver to power 3 of the...

posted in: Drivers Products Constant Current


Was this answer helpful?

Let us know!

The key words in that statement is ?CONSTANT CURRENT? and ?700ma?
 
Forget about Wattage with High Power LEDs when Sizing a driver;
Watch this brief video if you want to know why
If the forward voltage is 3.3VDC x 0.7A(700ma) = 2.3W (NOT 3W), which is why you size using Forward Voltage (Fv); When using a constant current driver and wired in series,, the LEDs are driven at the same Drive Current regardless of their Fv.

You would use the given Fv to size the driver, but if it was unknown, you could use he stated nominal wattage (if the spec sheet stated 3W driven at 700ma as an example) then 3W/0.7A = 4.3VDC ? so this is what you would use to size the driver UNLESS they give you the REAL Fv (because there is NO WAY it is 4.3)
 
Therefore add ??-700? at the end of the driver part number I gave you ? same price ? driver is sized the same way
When you wire LEDs in Series the Fv is accumulated
Therefore 4.3 VDC + 4.3 VDC + 4.3 VDC = 12.9VDC, therefore the 15VDC can be used
Semper Fi Model RPK-120-15D-700
120 VAC dimmable input and 700ma output drive current (15VDC max load)