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LM3445 No Triac Application

Other Parts Discussed in Thread: LM3445, LM3444

Hi

Our customer will use LM3445 without triac dimming.

Is the following circuit possible?

Please let me know if you have any questions.

Regards,

Koji Hamamoto

  • Koji:

     

        It is possible to use this circut to power the LM3445. You need small vaule resitor for R2, maybe around 10K for 120Vac input. The power loss on R2 is big. The excess current goes to zener diode D1.  It pulls more current than necessary from the line and hurts the power efficiency. So I don't recommend using this circuit to power LM3445.

     

    David Zhang

    Applications Engineer

    Lighting Power product

    Texas Instruments

  • HI David,

    What would you recommend for the customer?

    Regards,
  • John: My recommendation is to use the orignal circuit in the EVM.David Zhang
  • Hi 

    Could you provide us any reference circuits which is for no triac dimming application?

    Regards,

    Koji Hamamoto

  • HI Hamamoto-san,

    What David-san means is that any reference circuit for this device can work with or without triac dimmers. The triac dimmer is the wall switch which is outside the circuit. So the same circuit works with or without a triac dimmer.

    I hope this helps.

    Regards,

  • Hi Cummings-san,

    Thank you for your support.

    Our customer are considering how can we increase the efficiency at outside the circuit if not using triac dimmer.

    Due to the power loss on R2 as Daivid-san said, we are considering the other circuit.

    I guess it is possible to disconnect the line of the BLDR pin for reducing the loss of BLDR resistor if not using triac dimmer.

    ( The dimming is using PWM pin)

    (No triac dimmer)

    Can you provide us any advice about the method described above?

    Regards,

    Koji Hamamoto

  • Hi Hamamoto-san,

    I am not sure we can just disconnect the BLDR pin (David-san will have to confirm). One idea to help improve the efficiency might be to add a resistor in from the source of Q1 to Pin 10. Maybe around 100K (please note, this is just an idea and we have never tested this)?

    I hope this helps.


    Regards,

  • Hamamoto san:

     

        LM3444 is the non dimming version of LM3445. The reference design is AN-2083.

     

    David Zhang