There is a graph on the Meanwell hlg datasheets that shows you how load affects efficiency.
It is important to remember that dimming to 50% does not cut load to 50%. Even @ 100mA the
voltage of a 36v cob is still over 30v so the load is still ~120v combined, which is nowhere near 50% load of the 143v driver.
If you buy the hlg-
120h-c1050b driver, and throw 4 cobs on it, you will be at ~136v combined out of 148v max.
[This is the setup I currently run but 4 x 77v cxa3590 on a 120h-c500b]
Edit: aggressive autocorrect fixed
So at what point is the cob efficiency and driver efficiency dimmed become a problem. I'm looking at running 4 3590's at ~ 35w each with a hlg-185-c1400b driver. I think the number is correct. At work now. Will dim to get the 30 to 35 w each I want. The driver at full rated power is 94% efficient. What percentage will I lose in efficiency on the driver? Probably less than the gains on the cobs? The pwm supplies I am used to we use for motor control, standard power supplies, etc. Most are pwm switchers which are more efficient when loaded less. Not sure about these. Duty cycle less in most supplies means more efficiency. Less current less duty cycle on time of the pwm signal which forms the DC.