High Power White LED Model

[edwintsu]

How to model the high power white led?

Could we parallel the low power white led for high power?

E.g 500mA=10x50mA

Low power white led model
************************************************************************
.MODEL WLED D
+IS=1E-30 N=1.923 RS=32.09 EG=3.6 CJO=63.87P
+M=0.1513 VJ=2.02 FC=0.5 ISR=1.304m Nr=3.4MEG BV=12 IBV=369.5U
+TT=432.8N XTI=5
************************************************************************

 

[mesutyeni]

Since the semiconductor material is not a perfect conductor, some resistance is in series with this constant voltage load, see Figure 2.4. This means that the voltage drop will increase with current. The ESR (equivalent series resistance) of a low power 20mA LED is about 20 ohms, but a 1W350mA LED has an ESR of about 1–2 ohm (depending on the semiconductor material used). The ESR is roughly inversely proportional to the current rating of the LED. The ESR will have production variations too.

The ESR can be calculated by measuring the increase in forward voltage drop divided by the increase in current. For example, if the forward voltage drop increases by from 3.5V to 3.55V (a 50mV increase) when the forward current goes from 10mA to 20mA (a 10mA increase), the ESR will be 50 mV/10mA=5 ohms.

the Zener diode is shown as a perfect device. In reality, Zener diodes
also have ESR, which can be higher than the ESR of an LED. For initial testing of an
LED driver, a 5 W, 3.9V Zener diode can be used to replace the (white) LED. If the driver is not working as planned the Zener diode may be destroyed, but this is far less costly than destroying a power LED. Since the Zener diode does not emit light, the test engineer will not be dazzled.

 

[mesutyeni]

Its from the Book...

 

[shogun]

For high power applications you essentially need a current source for each LED. I do not believe that it is a good viable solution to place several low power LED's in parallel without somesort of a series resistor.

 

[edwintsu]

Thank you for your repley. I will try the method mentioned by mesutyeni.