My goal is to drive an infrared LED like (this SFH 4727AS) to control IR remote controlled devices (for example a TV).

I can already output the signal on a pin of my microcontroller. The signal has a carrier frequency of 38kHz.

I am however limited to a 5V 1A power supply and would like to drive the LED as close to the 5W psu limit as possible.

I first thought about using a MOSFET like this AO3400A together with a resistor, but decided it was worth using an LED driver, do you agree?

Now I’m looking at this PAM2804 constant current LED driver but I’m not sure if I can just supply my signal to the EN pin. The EN pin is meant for PWM-dimming, so does that mean the output is smoothed to prevent flickering?

I’d love to hear your thoughts about how I should go about this. Thanks

  • silvio2402OPEnglish
    1·
    1 year ago

    Hey, thanks for your comment. I looked at using a resistor in series with the LED, but if my calculations were correct I could only power the LED less than 3W and 2W would be wasted.

    R = (Vs-Vf)/If = (5V-2.8V)/1A = 2.2Ω

    PLED = Vf*If = 2.8V*1A = 2.8W

    PResistor = Vs*If-PLED = 5V*1A-2.8W = 2.2W

    Let me know if the calculations are correct.

    Edit: Calculations

    • cmnyboEnglish
      1·
      1 year ago

      Those calculations are correct.

      Since the remote control signals are short and low duty cycle, you could use a capacitor to provide the peak current for the LED without going over the maximum current of the power supply.