Ijaz Ahmed wrote:
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With PWM, you can conrol the average current through load but you can't reduce the peak current unless you switch at zero crsossing.

That is, if PWM goes all the way as PWM. Run it through a simple low-pass filter (a capacitor plus a resistor to ground) and it turns into a neatly smooth analog signal like right from a DAC. Not as precise/linear but we don't really care about precision here, just so the output is mostly smooth. But it seems a solution of "all or nothing" like a triac or a relay won't work in that situation (I could just as well attach a schmidt trigger to a DAC output and it would waste the smoothness all the same) so we need more "linear" solution - like an optocoupler with somewhat linear characteristic.