TLC69610: TLC69610 + TLC69614, after adding the diffuser, there is an issue with uneven brightness.

Hi Adams,

Have you ever met this before? I think maybe you need to ask light diffuser vendor.

Also, I would like to check the scan frequency. What's the line frequency here?

BR, Gracie

Hi  Gracie,

I’m new to TI products and still unfamiliar with them, currently testing only with sample code.

I found a #define in system_info.h. Is this what you referred to as the scan frequency?

BR, Adams

Hi Adams,

Are you using 8scan for this board?

BR, Gracie

HI Gracie,

only one TLC69610 and 17 TLC69614.

BR, Adams

Hi Adams,

I notice you use 8scan lines in your code. So if SUB_PWM is 9bit, your scan line freq is 3.66KHZ. And right now your LED board is in low brightness. Could you pls measure the channel voltage(LED-) waveform?

BR, Gracie

Hi Gracie,

The measured waveform is as follows.

Hi 

I want the TLC69614 OUT waveform, not the MOSFET

Gracie

And pls change the scan line to 4 in your screenshot line#25

You are not using 8scan. So you waste half the time

BR, Gracie

Hi Adams,

I feel quite confused about your test conditions.

Our LED driver is a current sink, and should output constant current when VSAT is fulfilled. So in a certain PWM data, Only when current doesn't increase means the VLED is sufficient. You may also measure the LED driver OUT pin voltage. Datasheet has VSAT for different current output.

BR, Gracie

Hi Gracie,

We need to design the backlight panel's thermal dissipation,

so we want to observe the panel's maximum heat generation and overall power consumption.

That's why we tried increasing the VLED voltage to see if the overall current would rise accordingly.

Hi Adams, 

It seems in VLED=7V, LED driver is already in constant current sink. And maybe it can be lower using AHVC function of this device: setting Headroom and enable FB.

I hope you understand my point: With the VLED rising, current will not increase at a certain voltage is the way it works. It's normal.

BR, Gracie

Hi Gracie,

May I ask how we should correctly measure the maximum power consumption of the Back light board?

Additionally, as shown in the diagram, the FeadBack (FB) part is currently not included in the testing. Will this affect the measurement?

Hi Adams,

If you are using external DC power to supply VLED, you need to apply VLED to a value that the total current is just your setting and will not increase with VLED increase. That's your required VLED. If FB is included, then LED driver's AHVC algorithm will take care of this part and adjust VLED automatically to the value I described.

BR, Gracie

Hi Gracie,

I have a question regarding the data we received from our customer.

The VLED is labeled as 12A max, but when we supply power using a power supply, the power supply shows that the current does not exceed 0.5A.

There is a significant difference between these two values. What could be the reason for this?

Hi Adams,

Do you mean this LED board is tested 12A max at customer side while only 0.5A at your side?

Do you guarantee 0.7V for the OUT pin of the LED driver? For LED's Vf 5.8V, VLED needs to be at least 5.8+0.7+0.5(cable loss)=7V.

BR, Gracie

Hi Gracie,

The value is noted by the customer on the circuit diagram, but we don’t know the actual measurement they took. However,

Because we are unable to measure values that are the same or close to those of the customer.

Also, the 0.7V you mentioned—is it referring to the OUT pin of the TLC69614QRTWRQ1?  

Hi Adams,

Correct.

COuld you pls also contact some TI field team to help us identify your project? Or you can contact me via mail.

BR, Gracie 

Hi Gracie 

Could you please provide your email?

Hi Adams,

I have sent a friend request to you.

BR, Gracie