Worse than typical PWM is running LEDs from AC mains power directly. I've seen this used in large, high-output panels. 20,000 lumens with 50/60 Hz flicker is ra

Worse than typical PWM is running LEDs from AC mains power directly. I've seen this used in large, high-output panels. 20,000 lumens with 50/60 Hz flicker is rather unpleasant to be around. And yes, two other ways to dim an LED are a switch-mode power supply with output current regulation, or a variable linear regulator. I'm familiar with both approaches being used in flashlight drivers, though PWM is also quite common. Good PWM designs tend to be over 10 kHz, which is nearly always invisible to the naked eye.