Hi A LED is indeed a diode. It's current changes pretty fast as voltage changes. It's voltage drop also highly temperature dependant. Driving one with a constant voltage and no current limiting is a very tough proposition. You would need to feedback the temperature of the device and adjust the supply accordingly.
It's much easier to do this some sort of current feedback. Compared to raw rectified AC, current regulation will also keep you from blowing out the entire array when there's a spike on the supply line. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Tuesday, September 18, 2012 11:45 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 100 watt & higher LED power supply... On Tue, Sep 18, 2012 at 5:56 AM, Michael Baker <mp...@clanbaker.org> wrote: > Time-Nutters-- > > OK-- So flicker would be objectionable running off a > rectified 110VAC line. My thinking was to find > a way around needing a current limiter that would > waste energy as heat. Even if flicker were not a problem what happens if the AC line voltage goes up? How to prevent over driving the LEDS. Or a voltage spike on the AC mains. I think you ned some kind of line regulation. Andin a 100W system you will have heat. The LED's current draw depends on temperature so you'd need some load regulation too. Or another way around the need for regulation is to run the LEDS at reduced power so there is a large safety margin for heat and line voltage variation. But then you need more LEDs for the same amount of light. A constant current DC power supply is not that hard nor expensive but if LEDs are cheap enough just get 2X more of then and run them at 1/2 rated current. Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
