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240VAC in, for LED driving (Dimmable)

Posted by: lpizales on

Hi,

I'm making a High Bright LED driver using a TOP223. I need it to be dimmable with a PWM signal. I was thinking of using a Shunt resistor to sense de LED current and compare it with the PWM signal, filtered with a simple RC filter. Is this possible? any ideas?

Thanks,

Laureano Pizales

Comments

Submitted by PI-Tucker on 05/14/2009

Yes you can lowpass filter the PWM signal then use it as a reference for a constant-current loop. Your PSU must have a CVCC (constant voltage constant current) characteristic, wherein the CC setpoint is adjusted by the filtered PWM signal. The CV setpoint has to be slightly above the maximum anticipated LED voltage at full current.

Submitted by lpizales on 05/14/2009

Thanks for the quick response.