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):
Best Answer
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.