.
Just dial in the desired current or power you want, that's what matters. Power (and efficiency) is what gets the job done. Period.
Led voltage (Vf) can vary a lot. It varies from led to led even if they are the same type, and also varies with temperature (with a negative delta). Led Vf also increases with ageing. The voltages in the table are just gross insights of the possible values.
The extra current/power goes both into light and heat. The more you overdrive the led, the more goes inneficiently into heat.
You can also choose to drive them at less current and power, this way you will enjoy higher efficiency and longer led (and other parts) lifetime.
By the way, are you running the Bridgelux CoBs in parallel? Running leds in parallel can be a bad idea, as led Vf variation can result in very unequal current and power sharing. If so, special care you should take. At the very least all CoBs should be thermally coupled (all of them carefully mounted on the same heatsink).
If you want to make things really well done, you should drive each CoB with its own driver/supply. Commercially available drivers with around 1.5A of current output and the required voltages are more or less common.
You want to set the CC to the desired level. The voltage will vary, as pointed out by Barkuti.
Leds are voltage dependent on output but they have to have a source capable of flowing enough current to meet that voltage.
Look at this xhp50.2 test provided by djozz.
If you want to run a led at a certain current you must supply a associated voltage to reach that current along with enough overhead voltage to account for losses.
As barkuti pointed out you have voltage losses and differences in vf’s that can vary.
By adjusting the CC (constant current) to a set value it should insure the led will never see more current than what was set. No matter what variances happen in losses or vf’s.
When led’s and wires along with electronic components heat up their values change slightly.
Let everything run for a little while then set CC to the value you feel safe with.
For the datasheet they tested at both 25 and 85. This could be done with either properly sized heatsinks, or more likely, in a thermal chamber with precise temperature control. How exact will you be controlling the temperature? What is the tolerance you require—these have +/- 7%. Which bin designator is your device B,C,D?
Current is the most important parameter, not voltage and not watts. Notice in the Table 4 section how many times they use this term to describe the performance expectations. You need to read the entire datasheet including the curves in the figures, not just pull a selected line of data and expect that to be the “absolute precise truth”.
If the power supply is set to be in CC mode then the voltage it puts out is totally dependant on the resistance of the connected load, is that not true?
Power supply can be either supplying a constant current OR a constant voltage, not both at the same time, right?
The chart in post #1 notes the voltage of 52 volts as “typical”, not an absolute value.
That’s total true. Its a fact of ohm’s law I = V / R
What the OP is not taking into account is R is changing slightly so when it does, V has to change to supply the set current.
If in CV mode again R is changing slightly so It has to change I (current) to keep voltage constant.
Yes. Generally speaking, power supplies (or drivers) working in constant current sense output current via a sense resistor or shunt (sensing the voltage drop at the terminals of such component) and thence they increase or decrease the output voltage to cause whatever target output current to flow. When a driver or power supply in CC mode is in open circuit it will of course raise its voltage to its maximum. This is absolutely logical!
In practical terms yes, although I will still say power. Power is what gets the job done, not current. However, with leds it happens that Vf is quite constant, i.e. leds are not a linear or resistive load (their resistance to the flow of current is variable, not constant).
People like to get whatever stuff simplified, and this is 0K. However, it is also common for people to do stupid things as a consequence of their inability to understand certain stuff.
As an example, let's take a look at this advertisement:
In it there is this following comment by a customer:
Según las caracteristicas del controlador, la salida del driver es de 35-66 voltias DC. Pero la realidad es que la salida es de 81.5 voltios DC. Esto ha provocado una averia por un exceso de tension. Cuando recibí el paquete, confirmé su recepción sin comprobar la tensión de salida (que suponía era la correcta). Al ver el problema cómo ha pasado la protecion al comprador, no me dan ninguna solución. NO RECOMENDARíA ESTA MARCA A NADIE.
Translation (more or less as I've been able, the above text could have been redacted better and still I had to fix some orthographic errors):
According to the characteristics of the controller, the output of the driver is 35-66 volts DC. But the reality is that the output is 81.5 volts DC. This has caused a breakdown due to excess voltage. When I received the package, I confirmed its receipt without checking the output voltage (which I assumed to be correct). After seeing the problem as it has passed the protection to the buyer, I am not given any solution. I WOULD NOT RECOMMEND THIS BRAND TO ANYONE.
I also wouldn't recommend it, its price is too high. :-D
Of course the resolution of the AliExpress tribunal is correct, suffice to say. If the above guy connected the driver to something and the load got killed by overvoltage obviously the fellow was doing something wrong, likely misunderstanding the basic principles of all this stuff.
To the above lad I'd say: mistake-stubborness can't help you, so don't feel embarrassed to admit your mistakes and learn properly. 
I have a power supply like that. Max voltage = 30 VDC and max current = 10 amp. Two knobs for each of voltage and current; a coarse and a fine adjustment. There is a CC and a CV indicator LED that illuminates to show what mode the power supply is in. If I was to just hook up a LED without regard to what was last set, I might very well cook that LED in less time than it takes to read this line.
The instructions read:
CONSTANT VOLTAGE MODE
- Turn the voltage regulator anti-clockwise to minimum position and the current regulator clockwise to maximum position.
- Press the power ON / OFF switch to ON.
- Turn the voltage regulator clockwise to that you are desirous of output voltage value.
- Connect the positive output terminal and negative output terminal with a load or similar component.
- The voltage regulator controls the output voltage indicator. Indicator shows that output voltage of the output terminals.
CONSTANT CURRENT MODE
- Turn the voltage regulator clockwise to maximum position and the current regulator anti – clockwise to minimum position.
- Press the power ON/ OFF switch to ON.
- Connect the positive output terminal and negative output terminal with a load or similar component.
- Turn the current regulator clockwise to that you are desirous of output current value.
- The voltage regulator controls the output voltage indicator. The current regulator controls the output current indicator.
Indicator show that output voltage and current of the output terminals.
RESTRICTED CURRENT PROTECTION MODE
- Press the power ON/ OFF switch to ON.
- Turn the current regulator anti-clockwise to minimum position then clockwise a little.
- Turn the voltage regulator clockwise to that you are desirous of output voltage level position (approx.1.5V).
- Link the positive and negative output terminals with a wire.
- Turn the current regulator clockwise to get the current level at which the restricted current protection will be active as
you desire. - Remove the wire linked to the positive and negative output terminals. Connect the positive output terminal and negative
output terminal with a load or similar component. - When the output current achieves the setting value of restricted current protection, and the restricted current protection
is active.
NOTE: After setting of the restricted current protection, if the current regulator is turned again, the restricted current protection
range will be changed.
C.C. AND C.V. INDICATOR (Only for the instrument with C.C. and C.V. INDICATOR )
The C.C. indicator is controlled by the constant current mode. Otherwise C.V. indicator is controlled by the constant voltage
mode.
they have a V-I curve, which is not linear, and it also depends on temperature, which depends on prior heat/time/power history
wle
Not at all, or not unless input cell pack discharge capacity or power delivery is insufficient, that is. Batteries handle unsteady loads very well. :-)
The 20 Ohms is the nominal resistance of the inrush current limiter device at room temperature or “cold” without any current. When the power supply is turned ON into the load circuit, the inrush current will be limited by this ICL resistance, so for your example, 75/20 = 3.75A.
This current produces a joule heating of I^2 x R= 281 Watts or J/sec, and this heat causes the resistance of the ICL to decrease since it has a Negative Temp Coeff.
The time to charge the input capacitor 440uF, is 6 x R x C, or about 55msec, so that is about 16J of heating for the inrush event.
Once the cap is charged then the DC/DC can come ON and charge up the output cap.
You would need to review the ICL datasheet to see the resistance vs temperature curve to know if you can leave it in the circuit, or will need a by-pass circuit or relay to take the ICL off-line once the inrush has completed.