[mrob]

Follow your switching regulator or rectifier with some analog filtering, then a linear regulator to convert the remaining ripple to heat. It doesn't have to be very expensive, and only loses a little efficiency. I have LED light bulbs that work like this.

[mlyle]

> then a linear regulator to convert the remaining ripple to heat.

I've become much less of a fan of the "switchilinear" approach. The control loop of a linear regulator isn't fast enough to respond to fast switching frequencies; the regulator is effectively just a resistor in a filter network at that point.

Even if your switching frequency is in the regulator's loop bandwidth, the loop's gain at that frequency is almost certainly very low.

[codedokode]

Ususally they use PWM for controlling the brightness because LEDs change their spectrum with voltage change and this is undesirable. That's why PWM is used in laptop and smartphone screens.