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High Effeciency Constant Current Source

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I am looking for a high effeciency voltage controlled constant current source for driving and dimming 3W White LED's. I saw the solution provided by IanP over here but I think effeciency is an issue in that circuit as resistor R1 will dissipate considerable amount of power which is not desirable when using LEDs for lighting purpose. Effeciency is the most important issue.

Does anyone have a better solution?
 

i think you need switching power supply with current control output.
and one small resistor series with LED, for protection.
 

Can you show an example?
 

These are my specifications
Supply Voltage = 24V
Each LED Rating = 3.3V /1.05A
Desired Output Current Range = 0 - 2.5A
Output Voltage = 20-22V
Current Control Voltage Range = 0 - 5V

I intend to connect many LEDs in series so the voltage has been kept higher.
 

one simple way:
use LM2576 as voltage regulator.
configure it to produce 23 volt output.
use one series resistor of about 0.1-0.22 ohm 2W
use one current control at output.
 

Davood Amerion said:
use one current control at output.
Click to expand...
Thats where my problem starts. If I connect the above metnioned current control circuit, I'll loose effeciency which I don't want. Any ideas?
 

It seems you expecting me to comming there and design and make you circuit !!!!

:D:D:D:D
 

You can even post a sample schematic if you have it. It will save your time to come here and build it for me ;)
 

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