Owon seems to follow the directions of manufacturer, there are two decoupling capacitors C40, C41 at the input supply , there is an inductor of 10uH between input and LX and so on.
The only that missing is the 1uF output capacitor that there is a position for that but it is empty The output voltage of this IC measured at position of C35 at 8.765Vrms with the Backlight to 0%.
This datasheet circuit is ok only in principle. But not in practice if look how it need do in real life.
About voltage in position of "missing" C35 (I recommend install there some small good ceramic capacitor instead of electrolytic what have nothing to do there - exept if want some decorative reasons). (in real it is not missing but it is in totally wrong place after long trace - if it is there near TFT Led connector.) Voltage is what it is. Important is current and it is current controlled. In 100% position current is around 200mA as described in Cimei-Innolux (TFT) datasheet. What voltage it give over series connected leds (voltage may vary dependent of led manufacture lot and temperature etc) is not very important. I have measured some amount different voltages in different individual scopes. (mostly some amount higher if I remember right)
In 2011 this circuit was this (and note: backlight brightness control range was more wide)
This circuit need good bypass capacitor in its input and its output. (there is not)
In some versions output capacitor is also behind long PCB trace and this is totally wrong and also as in many cases, there have been even crap electrolytic only alone, and this is just like nothing with these risetimes and frequencies. Just becouse they follow only this kind of datasheed principled schematics. (and same problem in some other circuits)
In this kind of SMPS, both current loops need be low inductance and if want avoid common mode noise in GND these current loops over GND need isolate from common GND area using "single point" connection so that this RF current do not fllood around ground. This PCB "topology" is terrible if think EMI. They have tried break all possible rules what can break if want design low EMI circuit.
Brightness control is different (freq/duty)
Input and output need bypass very tightly and as close as possible.
Today current sense resistor (R17 in this image) is typically 1R0.
22 Feb 2013, 18:54 Post subject:
--------------------------------------------------------------------------------
This old information is obsolete for 2012 and 2013 versions
2011 end, 2012 whole adapter board have been under development and it have changed many times! Sometimes less, sometimes radically.
Also in adapter board TFT backlight LED control have changed (many times) and freq are different. Also components are different. But still principle is same.
Last versions this circuit produce lot of noise and it need also modify on the aadapter board for less noise. (+ some other modifications for reducing GND noise.)
Backligt LED's current is important parameter and it need follow Innolux datasheet!
Also note, control IC have changed and it is not anymore 5126W.