MEAN WELL LED Driver with PWM Output

3 September 2021
mean_well_led_driver_with_pwm_output

Some lighting manufacturers stipulate that a dimmable LED driver with PWM output should be used, when dimming their light fittings.

A LED driver with PWM output is also preferable when dimming different lengths of LED strip.

If you need a LED driver with a PWM output, then you need the MEAN WELL PWM series LED drivers.

MEAN WELL PWM Series LED Driver

 

You will find the complete range listed on this website, under constant voltage LED drivers.

You may see the term “PWM signal” referred to on other MEAN WELL LED drivers that feature MEAN WELL’s patented 3-in-1 dimming technology. This does not mean that the LED driver has a PWM output. It means that it is compatible with PWM type dimming controllers.

We understand that this can be somewhat confusing, so let us explain in more detail what we mean.

What is a PWM signal?

First of all let us explain what a PWM signal actually is.

PWM stands for Pulse Width Modulation. This is a digital type of signal that has a duty cycle, which is the proportion of time when the output voltage is on relative to the entire period of time. It is expressed in percentage, with 100% being fully on and 0% being fully off.

This type of signal is commonly used in sophisticated electronic control circuitry, including dimmable LED drivers.

The below diagrams give you a visualisation of what the signal looks like at different output levels.

PWM output of LED drivers
PWM Signal Duty Cycles

 

MEAN WELL uses PWM signals for two completely different tasks:

1: Dimming control

If you have been browsing through the range of Australian approved MEAN WELL LED drivers on this website, you may have noticed that many of them feature 3-in1 dimming. This is a patented MEAN WELL feature.

Basically it means that the LED driver is compatible with 3 different types of dimming controller. Including dimming controllers that have a PWM output. The LED driver automatically detects the incoming dimming control signal and varies the current amplitude (with the exception of the PWM series LED driver) of the LED driver in order to dim the lights.

2: Control of the DC output

With the MEAN WELL PWM series LED driver, a PWM signal is used to control the DC output. Unlike all of the other MEAN WELL dimmable LED drivers, the current amplitude is not varied to control the light output.

Instead the output is switching on and on at a very fast rate. So fast that it is not detectable to the human eye. This rate of switching is controlled by a PWM signal. As the dimming control is turned down the rate of switching reduces. This causes the LED lights to DIM.

What is the benefit of a PWM output?

The simple answer is that it gives you even dimming of the LED lights, regardless of the load you have on the LED driver.

With the LED drivers that vary the current amplitude to effect the dimming, you need to match your load as closely as possible to the maximum load of the LED driver to ensure even dimming (we suggest you use 90~95% of the rated output)

 Also, if you are using multiple LED drivers to drive different lengths of LED strip, you need to ensure all of the LED drivers are loaded to the same capacity.

For example, of you have 3 LED drivers powering 3 different lengths of LED strip, all would need to be loaded to 95% of their rated maximum capacity in order for them to dim simultaneously. Otherwise they will start to dim at different times. This usually means spending quite a bit of time working on the design to ensure you end up with equally loaded LED drivers. And then you have to hope nothing changes at the time of installation.

By using a PWM signal to control the output, the LED drivers will give you even dimming regardless of the load on the LED driver. This is why if you are dimming LED strip, we recommend you look at the MEAN WELL PWM series as your first option.

If you have any questions about using and installing a MEAN WELL LED driver, please contact MEAN WELL Australia.