Hello all,
I am using TPS61196 to drive my backlight which require 56/58V and 600-720mA.
I am applying the schematic here also.
For the purpose my current per channel is set to about 114mA, where 5 channels are in parallel and I am using one 10M Ohm to ground.
What is the issue: >> When the PWM (20Khz), is at 100%, and I try to power it up, it starts with extremely high output voltage - about 76V, and keeps it that level, and the backlight is blinking.
Then I decrease the duty cycle of the PWM to about 70% and the blinking is stopped, then I increase again the PWM to 100% and it works fine with no blinking and the Vout is 56V.
I measured the IFBV of the 5 parallel channels and here is the voltage : That is when the blinking is present and the output voltage is 76V.
Then as I said, I decrease the PWM to about 60% or something, the blinking is gone, and then I increase the pwm back to 100% and this is now the IFBV voltage, (0.52V measured):
The output voltage is now 56V and everything works fine.
I did something that solved the problem, I set Iset to 160mA per ch, and 5*160 = 800mA in the range of IF of the panel, and there is no more blinking starting at PWM=100%.
But here is the question:
- No matter that the issue is solved by increasing Iset, I want to understand why it did not worked at 114mA per CH, because IT SHOULD WORK ANYWAY, despite of the current, as I decrease the PWM and then increasing it back to 100% and everything works fine.
The problem is with starting the TPS61196 at maximum PWM and the output voltage (76V) is quite above the panel voltage (about 56V). 
Thanks, Tsvetomir
