LM3445: PWM dimming tolerence

Hello,

It can but it will depend on how it is set up. The LM3445 has a minimum on time, around 160-170 nS typical which has to be taken into account.

Do you plan on using this as a buck or some other topology? What switching frequency range were you considering? The lower the better for higher PWM dimming resolution. Same is true for the PWM frequency, the lower the better. You may see non-linear dimming that low due to the inductor charging rate.

Probably best to get your operating conditions, type of converter (buck, flyback, etc) LED stack voltage, current and go from there.

Regards,

Hi Irwan,

I have plan to used as a buck, now have no any prefer switching frequency, just want check LM3445 can support TRAIC dimming can support to ~1% dimming, is LM3445 angle detect can support it? Or need how low switching frequency can support it?

And LM3445 can support TRIAC dimming and analog dimming at the same time?
I want to choose one lowest current output from TRIAC or analog, is it possible?

Vin= 100 ~ 277Vac, output : 20W,(max. 25W) output 7 * LED, ~21Vdc

Thanks!
Jeff

Hi Jeff,

It can support dimming down to 1%.  Are you planning on using the Valley Fill method?

LM3445 can support both at the same time with external circuitry.

Universal input triac dimming will be difficult due to the EMI filter and damper capacitor.  The EMI capacitor value will be determined at low input voltage making the high voltage triac interfacing more difficult.

Regards,

Hi Irwin,

Could you please provide your contact e-mail to me, due to my customer have few questions, I think will more faster to clarify.

Thanks!

Jeff