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#11
November 29th 14, 01:37 AM
posted to rec.radio.amateur.homebrew,rec.radio.amateur.boatanchors
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High brightness LEDs?
In rec.radio.amateur.boatanchors rickman wrote:
On 11/28/2014 6:16 PM, Jerry Stuckle wrote: On 11/28/2014 5:24 PM, wrote: In rec.radio.amateur.boatanchors Jerry Stuckle wrote: On 11/28/2014 4:11 PM, wrote: In rec.radio.amateur.boatanchors Michael Black wrote: On Fri, 28 Nov 2014, wrote: snip Given that manufacturers want the least cost in a product, and the regulator in a light bulb would have no need for a variable regulator, and that these things are made in the millions, it would be extremely silly to assume that the regulator is anything other than a fixed regulator for LED's and is designed to handle the load of some fixed number of LED's. Once again, incorrect. Have you ever heard of "dimmable LED bulbs"? How do you dim without an adjustable regulator? You do realize that a dimmable light bulb is dimmed by changeing the supply voltage and not by anything else connected to the bulb? For incandescent, yes. But not for LED bulbs. If that were the case, why would some LED bulbs be dimmable and others not? To specifically answer your question, you design a regulator who's output is some precentage of the raw input as opposed to a regulator who's output is always equal to some reference voltage. Again, it all depends. And to be yet more specific, since LED brightness is proportional to current and resistors would waste power, the regulator would be a current regulator with an average current output proportional to the raw input voltage. Then why can't you use standard incandescent dimmers with LED bulbs? A lot of IC regulators can't handle high voltage. If nothing else, nobody saw the need, it was the solid state age. So dissipation issues aside, most regulators expect at most a relatively low DC voltage input. True for IC regulators. Hoever high voltage transistors exist these days which makes designing a high voltage regulator pretty trivial. Sure. But how do you handle the current requirements without some kind of transformer? Well, assuming you want some voltage greater than the wall plug maximum, the need for a transformer is pretty much a given unless some sort of voltage multiplying rectifier is sufficient for the need, which is where the current requirement becomes relevant. However, the subject was high voltage regulators, not where does the raw high voltage come from. And where do you get the current necessary to supply the LEDs in the bulbs? A typical LED required around 3V (usually 2.7V to 3.3V, depending on the LED)? A 9 watt LED would require 3 amps of current. Or, if the LEDs were in series, something less. But without a transformer, the current would still exceed that of an incandescent bulb. You obviously are unfamiliar with the structure of LED bulbs. You two are both speculating and have limited information to base either of your opinions on. Jim says, No, I am NOT speculating on anything. You do realize that a dimmable light bulb is dimmed by changeing the supply voltage and not by anything else connected to the bulb? which is not correct in that most dimmers work by reducing the phase angle of the applied AC or to reduce noise some simply don't turn on for entire half cycles. Yes, it is correct as it means that the average voltage is changed. Incandescent bulbs are thermal devices and the light ouput is directly proportional to the average applied voltage and don't care if the applied voltage is DC, a sine wave, or pulses derived from a sine wave. And dimmers do NOT work by changing the phase angle, they work by changing a thyristor phase control. See: http://en.wikipedia.org/wiki/Thyristor#Applications -- Jim Pennino |
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