LM3445: Min Ton of LM3445

gz wu

Part Number: LM3445

Hi,

I find there is a minimum on-time(about 200ns) for the LM3445.Min Ton matter means we have worse line regulation spec when TRIAC level is min.

Because Min ton is fix,LED voltage tolerance also effect min Iout.How to achieve constant Iout against Vin Vbuck Vout.

over 3 years ago

0 Sean Zhou over 3 years ago

TI__Mastermind 22745 points

Hi gz,

The maximum switching frequency attainable is limited only by the minimum on-time requirement (200 ns). Worst case scenario for minimum on time is when VBUCK is at its maximum voltage (AC high line) and the LED string voltage (VLED) is at its minimum value.

This is a normal phenomenon for the switching device, it was limited by the control logic circuit and there is no good way to solve it but you can try to connect some serial diodes with the load to decrease the bad effects. But this will lead to bad efficiency.

Sean

0 gz wu over 3 years ago in reply to Sean Zhou

Prodigy 190 points

Hi,

Do you have other ways to improve output current regulation when TRIAC level is min? We don't want to reduce efficiency.

Thany you!

0 Sean Zhou over 3 years ago in reply to gz wu

TI__Mastermind 22745 points

Hi gz,

I'm sorry that's the normal behavior for the TRAIC dimmer controller and we can't improve the output current regulation, but increasing the output capacitor that may be a little helpful.

Sean

0 gz wu over 3 years ago in reply to Sean Zhou

Prodigy 190 points

Hi Sean：

I tried to increase output capacitor.But it can't improve the output current regulation:LineRegulation.xlsx

If you have other advice,please tell me.

Thanks for the advice.

B/R

0 Sean Zhou over 3 years ago in reply to gz wu

TI__Mastermind 22745 points

Hi gz wu,

Thanks for your feedback, but we are really sorry that we also don't have many more suggestions for your requirement.

Sean

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LM3445: Min Ton of LM3445