I would like to dim an Innolux at065tn14 LCD backlight via an PWM signal generated by an arduino pro mini. The driver board has an pt4103 Step-Up Converter to drive the backlight of the LCD display. I'm having trouble dimming the display via the enable pin of the pt4103 with any frequency < 1 Khz.

I've cut the original trace to the enable pin of the PT4103 and connected the enable pin to one of the PWM pins of the arduino. Dimming the backlight works, but it causes severe distortion of the image with lines and stripes rolling over the screen.

How can i prevent the distortion which is caused by the PWM?

This is the board (vs-ty2662-v1 als known as PCB800099):

vs-ty2662-v1 lcd driver board

  • \$\begingroup\$ Welcome to EE.SE. The PWM for dimming needs to be synchronized with your video re-trace timing, which I do not know if it is available on a pin. You need the schematic to this board. \$\endgroup\$ – Sparky256 Mar 19 '18 at 22:01
  • \$\begingroup\$ Thanks and thank you for your suggestion! i'm just starting with electronics. Maybe there is a pin on the RTD2662 which exposes this timing? I'll check the documentation \$\endgroup\$ – Laurens Alers Mar 20 '18 at 8:43
  • \$\begingroup\$ I've tried a new approach by building my own PT4103 circuit based on the PT4103 documentation which seems to dim the display, but the image shown is darker when controlled by an external PT4103 circuit. Another approach I've tried is to cut into the existing circuit and apply DC voltage to the feedback pin this doesn't seem to work well either. What is the way to dim an AT065TN14 display? \$\endgroup\$ – Laurens Alers May 12 '18 at 19:19

I was able to get this board to dim the backlight by using a filtered PWM signal attached to the FB pin (see option no. 3. in the PT4103 documentation). I've cut the feedback trace close to the PT4103 and soldered a wire directly to the FB pin and to the right side of the 1R0 resistor near the PT4103.

By using the suggested circuit for a filtered PWM signal in the PT4103 documentation i was able to get the backlight to dim without any problems by using a 10Khz PWM signal and changing the dutycycle.

vs-ty2662-v1 filtered PWM backlight dimming

Filtered PWM signal schematic

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  • \$\begingroup\$ Congratulations on solving your issue :-) Could you improve your answer by including relevant schematics (e.g. a relevant excerpt from the PT4013 documentation that you mention) and drawings / photos of the modifications that you made? It is harder for someone to read words and try to imagine what you did, than to see diagrams & photos (a picture is worth a thousand words etc.). Thanks for responding to your original question with this update and again, congratulations :-) \$\endgroup\$ – SamGibson May 15 '18 at 16:46
  • \$\begingroup\$ Thanks for your feedback, i've added a schematic from the PT4103 documentation and a photo of the board i've modified. I hope my solution is clear now. Please note i'm not an electrical engineer, i've follwed the instructions from the PT4103 documentation. \$\endgroup\$ – Laurens Alers May 16 '18 at 7:32

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