Question: Hello I have recently bought a driver for 50w white LED, I was wondering if it is possible to power 50W RGB LED chip via this driver? I know white LED has different amperage, my driver is for warm white and is 1.5A and similar driver for RGB coloured LED drives much lower at 650mA.

So my question is: Can I power my RGB array using this white LED driver? Is there a device such as "buck" or "step down" that would enable me to?

Answer: 
Assuming the RGB LED is somewhat similar to those on the first few pages when googled, with an array for each colour channel, it is possible that you could drive each of the channels somewhat inefficiently and at a more-or-less random colour by adding some ballast resistors so that the total current through each channel adds up to the current from your constant current source and the voltage across each channel and ballast resistor is the same.

What a single constant current source won't allow you to do is change the colour hue, so there is very little point in using an RGB LED with it rather than a white one.

If you don't want to control the channels individually, then you should be able wire it up with ballast resistors so the voltages and currents match the that of the white LED. One of the specs said [sic]

> 
> 50W White:
> 
> 
> Forward Voltage (VF): DC 32-34V
> 
> 
> Forward current (IF): 1750MA
> 
> 
> 50W RGB:
> 
> 
> DC Forward Voltage (VF): Red 16-19V, Greed 24-27V, Blue 24-27V
> 
> 
> DC Forward current (IF): 600MA
> 
> 
> 

So the blue and green channels would need to drop around 7V and the red around 15V at 600mA to match the white LED. So you'd be wasting around 17W of power to get a lower quality of light.

Buying resistors which can safely dissipate that power will cost about the same as a white LED which will perform the job better. This won't allow you to control the led channels individually - you need all three on for it to handle the power of the white led, so you won't even be able to have seven colours and off let alone the full depth a proper RGB driver would give.
Without links to datasheets for the driver and the LEDs, this answer is part speculation.

The "while LED driver" is most likely to be a constant current driver, and as stated, apparently drives 1.5 Amperes constant current. Now, if the "50 Watt RGB LED" (presumably a multi-chip module) is rated for 650 mA, then driving it with a 1.5 Ampere constant current source is a recipe for trouble:

If the RGB LED module has internal current regulation, the driver will raise drive voltage in an attempt to deliver its rated 1.5 mA, and since this would fail, the driver is likely to overheat or indicate a fault condition.

If, on the other hand, the RGB LED module does not have its own current limiting, then the driver will overload the LED's current capacity, leading to, most likely, an immediate demise of the LED.

LED drivers often have a **current-setting pin** or a mechanism for setting the actual current to be delivered to the load, with the driver's rating (1.5 Ampere in this case) being the maximum supported value. In this case, simply configure the LED driver's current setting to the desired current for the R or G or B of the RGB LED that needs to be driven.

Note, though, that the RGB LED would require separate constant-current drive outputs for each of the R, G and B channels. If the while LED driver is not a multichannel device, this isn't going to work.

Neither white nor RGB LEDs have anything inherently locking them into a "white LED driver" or a color LED driver: In fact, white LEDs are typically blue or UV LEDs on the inside, with a secondary phosphor to emit the white light. So the constant current driver simply isn't affected either way by the color of the LED.