I am designing a high powered LED driver controlled by a microcontroller.
Now it would be very easy to make a constant current limiter so I don't burn out my LED. I have a bunch of LM317's and putting a resistor between ADJ and OUT gives me a circuit that limits the current.
I can then hook this up to a transistor in series, and use my microcontroller pin to switch it via PWM and get my LED controlled that way.
However I wanted to go a little further to see if I can run my LED's directly and not via PWM (i.e. switching them full on and then full off). This is likely to introduce more complexity into my circuit but I think I would learn something if I can get it to work.
Initially I was designing a variable current source (see here) but I have my LED's on hand now and after some testing I've discovered that they are quite bright even at very low current. It seems to me that linearly controlling voltage via the microcontroller would give me better control over brightness.
How can I provide my LED's with a PWM-controllable voltage? For instance I can get a precisely controlled steady voltage from PWM with a lowpass filter. But I obviously can't supply 1A or more that way. If I make a voltage follower with an op-amp, would I need a specific op amp that is rated for that current? (I have some op amps on order but they are "general purpose")
Could I put the lowpass filter on the side with the load current? (I had always been thinking about connecting the lowpass filter to the PWM signal rather than to the other side of the power transistor)
Any advice that is related to this topic is welcomed