TPS61196: Duty variation of PWM dimming

K.Hamamoto

Part Number: TPS61196

We found some unknown phenomenon during the Duty cycle is reduced.

The cathode voltage is increased to over 20V during the duty is reduced from 100% to 50% slowly. (The cathode voltage is 1V when the Duty is 100%)

Then OVP is triggered and shutdown.

The voltage will be stable at 1V(cathode) it the duty is reduced to 50% before the voltage is increased to 20V.

We have no idea about this phenomenon. Could you give us any advice for this? (This does not depend on PWM frequency.)

Regards,

Koji Hamamoto

over 6 years ago

0 Sheng Jin over 6 years ago

TI__Expert 3340 points

Hi,

when you say cathode, which pin you referred to? what is the LED string max forward drop voltage? what is your OVP resistor divider setting to? the OVP setting may be too high which trigger the ~3V threshold hold when duty cylce reduced.

-sheng

0 K.Hamamoto over 6 years ago in reply to Sheng Jin

Guru 12155 points

Hi Sheng,

Thank you for your reply.

I understand there is not enough information on the previous post. I got some detail from the customer.
Can we talk with e-mail if it is possible? Because the some information is confidential.

Regards,
Koji Hamamoto

0 Sheng Jin over 6 years ago in reply to K.Hamamoto

TI__Expert 3340 points

sure, please send email to Caryss Li <caryss-li@ti.com>, and keep me (sheng.jin@ti.com) in the loop too. thanks!

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TPS61196: Duty variation of PWM dimming