LM3445 circuit desgin review

mason moon

Prodigy 190 points

Other Parts Discussed in Thread: LM3445

Hi,

She designed LM3445 as attached file.

But it make a sound in this circuit.

If C1 capacitor changed 10uF/400V, it doesn't sound.

But C1 capacitor burned after few hours.

- LED Vf = 3.0V, LED Q'ty = 30ea

- Current = 500mA (max)

- P = 45W (90V*500mA)

Thanks & Regards

LM3445MM Circuit.pdf

over 8 years ago

0 David Zhang over 8 years ago

TI__Expert 3495 points

Mason:
Did she use SMD ceramic cap for C1 when there was a noise? She needs to use a film cap for C1. Since the power is 45W, I recommend using 0.22uF 400V through hole film cap. The 10uF/400V cap she used might have high ESR and got burned by the ripple currrent through it.
David Zhang

0 mason moon over 8 years ago in reply to David Zhang

Prodigy 190 points

Hi.

She changed hole film cap, but she wasn't solve.

Please review for bleeder curcuit part.

I think bleeder curcuit is problem.

Thank you!

0 David Zhang over 8 years ago in reply to mason moon

TI__Expert 3495 points

Mason:

Did the film cap still make noise? I don't think the through hole film cap makes noise. The noise must come from somewhere else. Was she able to identify the source of the noise? I don't see anything wrong with bleeder circuit.

David Zhang

Power management

Power management forum

LM3445 circuit desgin review