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[ LM3445 ] LED Current Fine Tuning

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: LM3445

[ LM3445 ] LED Current Fine Tuning

Hi,

Can anyone help me to understand the way of fine tuning of LED current?

My customer is designing the LED lighting as below.

  • LM3445
  • Isolated Flyback (like LM3445-120VAC EVM)
  • 5 or 6 LM3445s are in one system.

What they are concerned is, when the TRIAC dimmer (or user) turns down the brightness,

(this means, LED current goes to minimum)

the unit-to-unit variation of brightness could be getting more obvious for human eye.

In order to prevent this, customer would like to have a capability to adjust the LED current one-by-one.

Do you have any ideas to implement fine tuning feature with something like variable resistor?

Thank you for your support in advance.
Regards,
Ken

  • 0
    TI__Expert 5130 points

    Hi Ken,

    You can put a variable resistor in parallel with FLTR2 resistor (R15) to set different power set points, although this will impact the entire dimming range.  If the customer is only interested in changing the set point at low light level, they can develop a circuit using DIM signal to load the output. I have attached a circuit for your reference.

    Best regards,

    Victor