Hi,

I am using TIP 127 for controlling current of led as load, i have connected the emitter to +12V and collector to led series of 4 (2.2 x 4= 8.8V) using SMPS.
The base is connected with pre set 10K resistance to GND of 12V.
data sheet says 5A with 120mA...maximum..

 

Hmm not sure what you are asking for here. Post your planned schematic please

 

sorry base was with GND only...
but how to control current i think TIP is not suitable for controlling current in between 300mA to 1.5A

 

Hello,

You have nothing to measure / control the current.
You could try the following circuit:

Bertus

 

Would it not be better to use PWM in this case. Then using the OPs method heat sink for the transistor will be required

 

have a look at this simple circuit.....

 

Ritesh, what LED has a forward drop of only 2.2V with a forward current of 1.5? All of the high-current LEDs I have looked at have much higher forward drops...

 

Ritesh, what LED has a forward drop of only 2.2V with a forward current of 1.5? All of the high-current LEDs I have looked at have much higher forward drops...

there are series of 4 led red and many series are connected in parallel....
i want to control current without using so many series resistance, as before bc337 was used which was working fine for low current ~250mA but now i want more brightness by controlling its current not using PWM because there will be many other led series for flashing on display .
i am using smps of 12v 4A