Alternating current LED developed

"A South Korean semiconductor maker said it had pioneered an innovation that will allow energy efficient light-emitting diodes (LED) to light homes, officies and other buildings.

Seoul Semiconductor Co. said it was seeking a global patent for the "LED for AC", a LED that works on alternating current (AC) electric power and therefore can be widely used for general lighting requirements."

Full story here

Probably just 2 dies internally wired in reverse parallel. I would imagine quite a flicker at 60 Hz, as LEDs have no persistance and almost instant on time. Maybe they developed a phosphor with some persistance?
Rob

Probably put a high voltage diode in series with each too to prevent reverse breakdown.

I wonder how they're regulating current?

They had "AC LEDs" as far back as the 1970s; they consisted of two LED dice connected reverse-parallel of one another in the same package. Let's see if I have one on The LED Museum...BRB...


These unusual guys are "AC LEDs". They have two standard chemistry yellow-green LED chips inside, but they're connected opposite of one another. So when you connect them to a low voltage AC circuit, both chips glow alternately; one chip on the high side of the AC cycle, and the other chip on the low side. Because alternating current is usually found at 60Hz or higher, they appear to be both on at once.

Notice if you will, the unusual, flat gold plated leads, and the inverted conical case style. This case style ensures the LED can be seen from a wide viewing angle; and I'm uncertain as to why the leads were made that way. They honestly look like something that might be found in sophisticated telephone switching equipment from the 1970s.
If you just plugged one of these onto a board, it would orient itself as a right-angle emitter.

Here's a trick I learned in 1975 or so: Take an LED like this, and wire it in series with a standard C7 1/2 Christmas bulb. Add a clear case, and a pair of insulated meter test probes. You now have a test set that can indicate the presence of voltage from 2 volts to 120 volts, AC or DC.
If you don't have an AC LED, a pair of regular ones will work; just wire the two LEDs together so the cathode of one goes to the anode of the other; then hook the two remaining leads to each other in the same way; and treat it like a single LED in this circuit.

A dedicated fan of The LED Museum sent these unusual LED lamps to me.

This isnt that new! In europe they are developing lights to replace the existing incandescents. The problem is that they are expensive and are to bright. They dont have that smooth yellowish light.

-tom

LED based bulbs for use in indicating lights (for process control), have been around for some years. Some of these LED bulbs run from AC AND DC supplies up to around 240Vac.

I understood that these bulbs had some sort of rectifier built into them (apart from the LED's themselves)!?

[ QUOTE ]
cornkid said:
This isnt that new! In europe they are developing lights to replace the existing incandescents. The problem is that they are expensive and are to bright. They dont have that smooth yellowish light.

-tom

[/ QUOTE ]

Where did u find or see these ac bulbs ? i would be interested in one of them

i've thought of making an array that is wired for AC in reverse parallel a while back before i even knew of the concept...it sort of came upon me when i was researching what a rectifier was and then went...hmm, how many LEDs to drop 120VAC RMS...and so came upon an LED rectifier design that i never made cause i didnt have the moneyto buy that many white nichia LEDs...heh. then i found out about Chi Wing but we were too busy trying to figure out how to get a blue LED to replace all the panel and indicator orange backlighting in a few BMW cars. then we looked at the color wheel and went..doh! orange is a filter for blue...crap. that ended that.

Here is some info:

LED house light

-tom

Ya, I've seen xmas trees with leds and they flicker at 60hz very badly!!! I can see flicker of 75hz that most people can't see!! Drive me nuts!!!

[ QUOTE ]

Probably put a high voltage diode in series with each too to prevent reverse breakdown.

I wonder how they're regulating current?


[/ QUOTE ]

No need for the series HV diodes if the forward voltage is significantly less than the maximum allowed reverse voltage (I'd say a 2-3 volt margin would be plenty). Before the reverse voltage on LED "A" gets high enough to cause trouble, LED "B" turns on, and due to the highly nonlinear I-V curve, the reverse voltage on "A" never gets into the danger zone.

As for regulating current, my guess is they either have a built-in resistor (you can get indicator LEDs rated at 5V or 12V - they're simply LEDs with the resistor included in the package), or they have a string with enough lights that the forward voltage on each light never gets into the "handle of the hockey stick" part of the curve (I have a string of 70 Christmas lights - based on typical white LED voltages, these will never reach the forward voltage for them to draw their maximum rated current).