LM3414HV: Led artefacts during pwm dimming at 20 kHz

Alexander Hellekes

Part Number: LM3414HV

Hi,

I use the lm3414hv in a pwm dimmed application. When i drive it at 20 kHz pwm i get led light visible artifacts (flicker) during the dim process.

Led current is 580mA, fsw 295kHz, L 100 uH, Vin 48 V, Vled 28V, Cin 6,8 uF, Cout 10 uF.

The current is despite PWM dimming CCM to prevent flicker effects.

does somebody have an idea why i get this artifacts and how i can fix it?

Thank you very much for any advise.

Alexander

over 4 years ago

0 Yuting Shao over 3 years ago

TI__Genius 13001 points

Hi,

Please increase the switching frequency to see if there is any change. Normally, is recommends to set switching frequency much higher than dimming frequency.

Robin

0 Alexander Hellekes over 3 years ago in reply to Yuting Shao

Prodigy 20 points

Hi Robin,

thanks for your reply.

unfortunately it is not reallye better when i increase fsw.

any other ideas?

is it possible that the driver is not suitable for CCM?

i took a look at the typical application example, it shows an example which operates in DCM during the PWM off time.

thanks,

Alex

0 Yuting Shao over 3 years ago in reply to Alexander Hellekes

TI__Genius 13001 points

Hi,

Please help capture the LX and inductor current waveform for analysis. Thanks!

Robin

Power management

Power management forum

LM3414HV: Led artefacts during pwm dimming at 20 kHz