To drive LEDS, you have two options, each with their own pros and cons
a) linear
b) switching
a) linear, dissipates excess heat, simple (LM317) (or relatively simple)
b) switching, low dissipation, potential switching noise
To choose between these two, and then to choose which way to implement either, you need to look at your other constraints. Heat? Cost? Board area? Able to control finely? Design skills?
You can get integrated solutions for both methods. Maxim IC do a gazzillion drivers in both types, try sampling them for one or two.
Linear devices will always get hot. At 0.5A, with a few volts drop, you will always need to think about heatsinking, whether you use an integrated or discrete solution
FWIW, my personal preference for a linear multi-colour driver, and OK, it takes large board area, is a discrete solution. Each channel uses a TO-220 MOSFET, with a small resistor in the source to monitor sink current, driven by 1/4 of an LM324 op-amp, driving the gate to servo the source voltage to maintain the drain sink current, 3 channels uses 3 FETs and 3/4 of the LM324. The compare voltage to the 324 inputs allows you to set the currents. The heat dissiaption is spread over several big cheap devices. TO220s are good for 1 to 2 watts in free air, to 100watts on a heat sink, so it's scalable to many amps and higher voltages, still staying with cheap MOSFETs.
There are so many integrated LDO (low dropout) regulators available that can be configured as current sources that it would be futile for anybody other than you to start trawling through them. Look for voltage input range, heat dissipation, package size, AND ABILITY TO WORK WITH WHAT TECHNOLOGY STABILISATION CAPACITOR, ie ESR (ceramic, tant, alli elec), as you don't what them to oscillate in service.
To do without the heat, investigate integrated switching solutions.
The driver is inappropriate for the LED because the minimum voltage from the driver (18V) is greater than the minimum LED voltage at 600mA (3V). The driver is likely designed for LED arrays that have at least 6 dice in series, so 18V.
When you feed the particular LED die you mention with a constant current between 600 and 700mA you will get a voltage (assuming you have not destroyed the LED) that will be between 3V and 3.4V (or maybe the voltage is specified at a particular current).
If you do not exceed the recommended current, the LED voltage should not exceed the range given (it will actually drop a bit as the LED heats up).
You only get to pick either the voltage or the current. With an LED, you are expected to pick the current and the voltage across the LED will be a result of that current. If you tried to run the LED from a constant voltage supply you would have to find the voltage experimentally and it would not be stable (and could kill the LED).
Best Answer
The total forward voltages of all the LEDs is specced at 286V. this is the same as the output of the supply which means that the supply has essentially no wiggle room to account for manufacturing differences. This could result in damage to the supply and is not recommended. Either remove 12-20V of LEDs, or get a larger supply.