1cecream:
Thx Grumpy_Mike. I have confirmed that the transformer is actually just a power supply (converts AC->DC) and does not contain any driver, so If I select an LED Driver that outputs constant current less than or equal to 650mA (the max current my LEDs take) I should be fine right?
That is a LED driver; it states it quite explicitly on the label. It is not a "transformer" and I'll guarantee that if you try to use it as a DC power supply that it won't work.
With regards to controlling it with PWM, either by switching the AC input or the DC output, that won't work with this type of driver either. Try a simple test: turn it on and see how long it takes for the LEDs to light up. It's just a fraction of a second but what you're seeing is the driver attempting to reach a stability in its current output causing the delay.
The driver states a "30 - 46VDC" output voltage but what that means is it's only stable when the Vf of your LED string is between 30 and 46Vf. If you have any 650ma LEDs you can try a simple test by just connecting a few of them (Vf outside of 30 - 46Vf) and what you'll see is the LEDs flickering. Again, the driver is not stable outside of 30 - 46Vf so you can imagine what would happen if you tried to PWM that output. It does not work like a typical DC transformer.