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TPS61196: Driving two LED strings with different Voltages

Ryan Delfino

Prodigy 150 points

Part Number: TPS61196

Hello there,

We plan to use part TPS61196 to drive below LEDs:

RED string of 28 LEDs with Vf =2V for a total of 56V
BLUE string of 28 LEDs with Vf =3.1V for a total of 86.8V

Is this possible with this part ?

If not, can you help suggest a suitable solution ?

Appreciate your response.

Thank you.

Regards,

Ryan

over 3 years ago

0 Sean Zhou over 3 years ago

TI__Mastermind 22745 points

Hi Ryan,

Since there is a big voltage difference between this two LED strings, I would not recommend just use this way since this will lead to a high thermal issue, I would recommend adding some resistors to match the voltage difference for the Red LED string. That would have better thermal performance.

BR

Sean

0 Ryan Delfino over 3 years ago in reply to Sean Zhou

Prodigy 150 points

Hi Sean,

Thank you for your advice, I appreciate it.

Can you help advice appropriate values for the resistors to match this RED LED string voltage difference ?

Thanks.

Regards,

Ryan

0 Sean Zhou over 3 years ago in reply to Ryan Delfino

TI__Mastermind 22745 points

Hi Ruay,

Please use the below equation to calculate the resistor:

R=(Difference voltage between two channels) / (Current for each channel)

BR

Sean

0 Ryan Delfino over 3 years ago in reply to Sean Zhou

Prodigy 150 points

Hi Sean,

Can you help check if below diagram is correct based from my understanding to your advice?

Thanks.

Regards,

Ryan

0 Sean Zhou over 3 years ago in reply to Ryan Delfino

TI__Mastermind 22745 points

Hi Ryan,

Yes, you have got the right circuit, please go on and any further question, please let me know.

BR

Sean