Thank you. Thank you very much. You explain very clearly^^. I use a 1W led with 3.1~3.4V forward voltage so I use 5V supplyThe circuit was working as logical voltage, only the low and high, and the Q2 as a switch not a resistor to do the voltage divider.
The circuit was used for the current source component, if the power is providing a voltage source, it could be damage the LEDs, you can see the circuit and tell me how do you decide the +V power and the Vf of LEDs?