Analogue Dimming of light - current sink type

Discussion in 'General Electronics Chat' started by arjun sureshbabu, Apr 19, 2017.

  1. arjun sureshbabu

    Thread Starter New Member

    Apr 17, 2017
    Hello All,

    I am using TLC7226CN (4 channel Digital to Analogue converter IC) to convert 8 bit digital signal to 0-10V analogue signal which is given to a RECOM constant current LED light driver (RACD-150A) and it works well. Recently because of higher wattage requirement, I bought Thomas Research LED driver (PLED-200W). When I connected this driver, there is no effect of 0-10V dimming signal and the led light (connected to the output of the driver) started blinking. Looking at the datasheet I got to know that the Thomas Research Driver needs current sinking type dimming signal. I am bit confused. The DAC IC is of sourcing type. I am not sure how to convert the existing circuit to current sinking type. Can anyone help me out on this?

  2. crutschow


    Mar 14, 2008
    The PLED-200w data sheets says you need to sink 2mA (purple wire).

    Any standard op amp can do that.
    But depending upon the supply voltages available it may need to be a rail-rail type.

    Just connect the op amp as a gain of +1 follower to the DAC output.
    Last edited: Apr 19, 2017
  3. ThomasResearchDude

    New Member

    Apr 21, 2017
    Agree here with Crutschow, the output amp on the DAC is not appropriate to the task.I can add that the 2mA figure is the maximum source current for a single TRP driver; in reality, they typically run around 1.6mA. Recom folks suggest their dimming works both PWM and 0-10V, which explains why it works with your DAC.