Hi all,

Nice forum!

It has been many, many years since I did any electronic experimentation so please be gentle

I am developing a LED light test model. At this stage I am creating a test unit using a TI TPS61042 constant current LED driver. A smaller .pdf of the LED driver is attached.

I believe Figure 24 on Page 11 is want I want to start with however I will only be using 5 LED's, if that makes a difference.

I want to add a variable brightness control to go from 0 to 100%. Such as a rheostat. The diagram indicates I can do this via a PWM circuit to the CTRL pin. There is much more info on Pg.2 under the CTRL section.

I have been looking at dozens of PWM variations and now I am more confused.

Can anyone assist with a simple PWM I can add into this circuit?

Thx DD

Attached Files

TI tps61042 LED driver small.pdf (125.0 KB, 31 views)

 

You can try this simple circuit. R1 and R3 model a variable resistor, with the junction of the two model resistors being the wiper connection. The variable resistor controlls the duty cycle. Connect the "OUTPUT" wire to your chip.

Attached Thumbnails

 

__________________
You don't need a quadraphonic Blaupunkt -- you need a curve
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Hi BrownOut - thx for the circuit. So, to have variable control, I should replace R1 & R3 with possibly a 100k pot? If I want one with a switch on and off, same process?

Thx DD

 

Correct. The middle connection is the pot's wiper connection.

__________________
You don't need a quadraphonic Blaupunkt -- you need a curve
ball.