SMD LED 12v through 1mm

[bernardgreen]

BS! I have a high flux white LED sitting right here on my desk and it is made from a single die.

Single die with three or more LEDs constructed on it.

High flux LEDs do not have resistors in them either.

Neither do low flux LEDs ( other than constant current LEDs which have current limiting "active" resistors contructed on the die.

And PWM dimming from a current source eliminates the problem of the LEDs spectra changing in a mismatched way until the average current is very low.

Yes because the "brightness" is averaged out by the human eye from full intensity pulses separated by dark. Snag is the eye response is not linear.

You definitely don't change the brightness of LEDs by changing their voltage

You can by varying the voltage applied the the resistor and LED

http://preview.powerelectronics.com/mag/405PET24.pdf

 

[DetlefSchmitz]

I must admit that I was led to believe that recent white LEDs are actually designed to output in the ultra-violet range, and the packaging was loaded with fluourescent dies in combination.

 

[aptsys]

Single die with three or more LEDs constructed on it.

Source please?

I've worked in opto-electronics for years and even spent a month in Hong Kong at YesLED where we worked on a custom LED for one of our products and I can confirm the white LEDs are a single InGaN/GaN dies with a YAG:Ce type phosphor coating.

There are multi-chip LEDs out there, but they're just multiples of the same die.

White LEDs are not a single colour LED but are at least 3 single colour LEDs in the same package with the three colours mixed to produce white light. Each single colour LED has to be the right brightness compared to the other two to get the correct white result. The current in each single colour LED is set by a resistor for that colour.

High flux LEDs do not have resistors in them either.

Neither do low flux LEDs ( other than constant current LEDs which have current limiting "active" resistors contructed on the die.

You said it.

You can by varying the voltage applied the the resistor and LED

!= varying the voltage through an LED. You're still varying the current through the LED, but in a non-linear way, since you're now using the VI curve of a diode to adjust the brightness. PWM dimming is near linear for a large percentage of the slope.

 

[bernardgreen]

Single die with three or more LEDs constructed on it.

Source please?

Abstract from the IEEE library

A trichromatic phosphor-free white light-emitting diode (LED) has been implemented by using adhesive bonding scheme. The device has been operated as a three-terminal device with independent electrical control of an AlGaInP-based red LED chip and a GaN-based dual-wavelength (blue and green) LED chip. As 25mA and 60mA was injected into the red and blue-green LED chips at room temperature respectively, white light emission could be observed with CIE chromaticity coordinates (0.3330,0.3241), correlated color temperature Tc=5467K and optical power Фe=2.223mW. The electroluminescence measurements also show that the emitted white light is composed of blue, green and red lights, centered at around 452nm, 517nm and 632nm. The fabrication and the electrical and optical performances of such white LED were described.

That is three separate LEDs bonded to a substrate. I do have access to a document detailing the diffusion of three LED "devices" on a single die but it is covered by a non disclosure agreement. That method has, as you say, been replaced by UV LED exciting a phospher for most applications.

I've worked in opto-electronics for years and even spent a month in Hong Kong at YesLED where we worked on a custom LED for one of our products and I can confirm the white LEDs are a single InGaN/GaN dies with a YAG:Ce type phosphor coating.

My career goes way back before LEDs were produced. Developing methods to get the best out of the first generation of LEDs was one of my projects. It was a relief when manufacturers began grading devices by intensity. Then we could almost be sure that a row of 30 would all be similar in brightness if they were all from the same batch or grade.