Kelvin writes to inform us of a tutorial site:
Would like to recommend this blog site, The Signal Path. The videos there provide very good explanation about the topics covered. The most recent one is using op-amp to generate PWM signal. The previous one on oscillator was also very informative.
Do check it out.
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Awesome topic! I’ve been looking for example circuits to generate PWM without a processor or even a dedicated LED driver chip (usually such chips are rather expensive and come in inconvenient packages intended for cell phone manufacturers instead of DIY types). Unfortunately, spending 33:47 watching videos seems like too little information for the time investment. Where is the link to a quick circuit schematic? Admittedly, the videos are nice when you need help deciphering the circuits, but what if you just want to cut to the chase?
By the way, Maxim has some nice parts which combine boost regulation, constant current supply, processor I/O, and even analog brightness control. The boost allows you to string several LEDs in series so they share current, with the advantage that they’ll all have exactly the same current and therefore matching brightness. The constant current is set by a precision resistor, and is handy for driving LEDs, where current is more important than exact voltage. Finally, the I/O allows connection to the PWM output of a processor but it also allows a proportional voltage (from a pot) on the same pin to control brightness. Thus, the chip can actually run standalone. Unfortunately, it’s a tiny 3x3mm package with no pins that you can touch with a soldering iron or test meter probes. Thus, you can see why I’d like to build something similar without the inconveniences.