Originally Posted by cirthix
It depends. Is the constant-current driver operating at constant current over many cycles or is it operating at constant current *while on*? I suspect the latter, with pwm dimming turning on and off the whole supply at a much lower frequency. If I had a catleap, I'd take it apart and probe it
Originally Posted by siberx
Do you actually have one of these monitors and have you examined its backlight and found it to be lacking? I own one and observe no flicker problems whatsoever, which is corroborated by my analysis of the backlight driver circuit. They're using a 330kHz current-controlled boost converter (two of them, in fact - half the LEDs run off each) to drive the backlighting; this results in no visible flicker whatsoever. There's some concern that their choice of circuit for controlling the brightness setting allows for some unevenness between each side of the monitor (one boost converter drives two-thirds of the LEDs on one half and one-third of the LEDs on the other), but other than this (which can be fixed with a mod) the backlighting seems fairly well implemented from a flicker prevention perspective.
Earlier posts of mine indicate some flicker around 150Hz or so; I suspect this is some oscillation in the output circuit, and the slight variance in brightness from this (not a full on/off cycle) is not visible at all even to my fairly flicker-sensitive eyes (hand wave test included).
Flicker test (max brightness, ~half brightness, min brightness):
Based on the technique outlined Here
2C Catleap model.
150Hz backlight frequency.
No flicker at full brightness.
~20% modulation at half brightness.
~60% modulation at min brightness.
Definitely has lower flicker modulation than other LED displays, but the comparatively low frequency also makes it more visible. I personally can see only minor flicker at 50% in peripheral vision, but I know from past experience it's enough to cause migraines. Currently trying to decide on best way to modify the display to eliminate all flicker.