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What’s a PWM (pulse-wave modulated) lighting dimmer?

Pulse-width modulation (PWM) is a commonly used technique for controlling power to inertial electrical devices, like electric motors, and for LED lighting.

PWM dimmers for lighting create “pulses” of electricity –  turning the electrical energy on and off very quickly – much faster than your eye can detect, and this provides electricity in a very efficient manner.  PWM also allows you to adjust the lighting output by varying the energy of the pulses, and therefore vary the amount of energy received by the LED lamp. This is much more efficient than a rheostat, where the resistive load of the rheostat is used to control the energy going to the lamp.  In rheostats, this resistance wastes the energy that would otherwise have gone into the lamp as the rheostat dims the light.

For LED lighting, PWM dimmers are the best way to control lighting output using the least amount of energy.

In sizing a dimmer for your needs, take a look at not just the power consumption of the LEDs you’re using, but also look at the type of LEDs.  It makes a difference!

Most common LEDs, like smaller, 3mm, 4mm, 5mm or 8mm types, are very controllable using PWM dimmers.  Many types of LED fixtures, like convenience lamps, map lighting and some types of LED strip lights use these common, low power LEDs.

You should be aware that some of the newer, very bright LED types, like 5050 and 3528 LEDs are a little more difficult to control with PWM dimmers, or any type of dimmer for that matter.  They will dim pretty well but these types are more sensitive to the minimum power needed to illuminate them.  When a PWM Dimmer is connected to a 5050 LED, for example, it will control the lighting levels from 100% output down to about 30% output pretty well.  But at some point below a moderately low output level, the LED will receive insufficient power to stay illuminated and will turn off.

There’s nothing wrong with the LED – this just happens to be how they work and should be something you’re aware of when choosing LEDs and dimmers.