Selecting The Best LED Driver for Dimming LED Strip

When selecting a dimmable LED driver for use with an LED strip, it is recommended that you select an LED driver with a PWM output.

Some LED drivers dim your LED strip by varying the amplitude of the output current. 

This type of LED driver suffers from a phenomenon known as 'dead travel'

Dead Travel

To achieve a satisfactory dimming result, LED drivers that do not have a PWM output need to be loaded up to their maximum capacity (PSA recommends 90~95%). 

If the load is lower than 90% you most likely will find the dimming performance to be unsatisfactory.

For example, if you place a 120-watt load on a 240-watt LED driver, nothing will happen until you turn the dimmer switch down to about the halfway mark.

If you then turn the dimmer past the halfway mark you will find the light suddenly drops down to very low, making it impossible to adjust the light to the required light level.

PWM Output

LED drivers with a PWM output dim the lights by varying the duty cycle of the output. 

In layman's terms these LED drivers are cycling the output on and off at a very fast rate, this can be typically anything from 300 ~ 1.4Khz. 

To dim the light the LED driver extends the momentary period the output is 'off' and reduces the 'on' time. The above diagram shows the output duty cycle of an LED driver with the ON period being about 50% of one cycle. This means the LEDs would be at about 50% brightness in this instance. 

The key advantage LED drivers with a PWM output have, is that they will dim evenly regardless of the load placed on the LED driver. 

Dimming LED Strip

Non-PWM Output LED Drivers

If you do not use an LED driver with a PWM output, you have to work out exactly what length of strip you can use with your LED driver, to ensure that it is loaded to its maximum rating to achieve even dimming.

This task is harder if you are controlling multiple LED drivers from one controller. Each of the LED drivers will need to be loaded to exactly the same capacity, so that they dim synchronously.

For example, if you are using a 150 Watt LED driver and a 240 Watt LED driver, you would need to ensure you loaded each of the LED drivers as follows:

150 Watt driver:  actual load required is 142.5 Watts

240 Watt driver: actual load required is 228 Watts

The actual load values shown above are equal to 95% of the maximum capacity of the LED driver. 

So if your LED strip is rated at 12.5W per metre, you would need 11.4 metres for the 150-watt driver and 18.24 metres for the 240-watt LED driver.

Typically the LED strip is cut to length on site, during installation. Sometimes it is necessary to cut the strip a bit longer, or shorter than originally anticipated. This means the load on the LED driver has been changed and the dimming performance could be affected.

LED Drivers with PWM Output

If your LED driver has a PWM output you can relax.

Under normal circumstances, Power Supplies Australia recommends that you only load up an LED driver to 80% of its maximum rating. This is to allow headroom for spikes in the AC supply. 

LED drivers with a PWM output allow you to continue to follow this rule. 

During installation, if the length of the LED strip does end up being different to that originally calculated the dimming performance of the LED driver will not be affected.  

LED Drivers Stocked by Power Supplies Australia with PWM Output

Power Supplies Australia stocks two different series of LED drivers, with a PWM output. The main difference between the two is the dimming technologies used. 

Dimming with Leading or Trailing Edge TRIAC Dimmers

If you want to dim your LED driver from a leading edge (TRIAC) dimmer, or trailing edge dimmer you will need to select an LED driver from the Power Source PDV series. 

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Most dimmer switches found in Australian homes will be either a leading edge, or trailing edge type dimmer. These work by chopping the AC input into the LED driver.

The PDV series LED drivers are available in two variants:

• IP20 rated for indoor installation (30 Watt and 75 Watt)
• IP66 rated for outdoor installation (100 Watt, 150 Watt, 200 Watt, 240 Watt, 300 Watt and 360 Watt)

All models are available with either a 12V, or 24V output. 

Follow the below link to browse the range of PDV series LED drivers, compare models, download data sheets and place online orders:

AC Phase Cut Dimmable LED Drivers

It should be noted that any LED driver installed outdoors should not be mounted in direct sunlight. This could cause the temperature inside the LED driver to soar above its maximum operating temperature. This could potentially lead to a failure, which would not be covered by the warranty. 

Do not submerge LED drivers that are labelled as 'waterproof' or 'weatherproof'.

Other Types of Dimmable LED Driver

Power Supplies Australia also stocks the MEAN WELL PWM series LED drivers. As the series name suggests, these too have a PWM output.

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The PWM series LED drivers have a plastic body and are IP67-rated, so they offer good protection against water and dust ingress.

It should be noted that the plastic enclosure is not UV stabilised, so could become brittle if installed outdoors. 

As we have already mentioned above, any LED driver installed outdoors should not be mounted in direct sunlight. This could cause the temperature inside the LED driver to soar above its maximum operating temperature. This could potentially lead to a failure, which would not be covered by the warranty. 

Do not submerge LED drivers that are labelled as 'waterproof' or 'weatherproof'.

The PWM series LED drivers are available in 40 Watt, 60 Watt, 90 Watt and 120 Watt variants.

Power Supplies Australia carries the 12V and 24V models in stock. Other output options are available as special order items.

For non-standard voltages that we need to order in, there is a minimum order quantity requirement of 200+ pieces and the lead time is typically 12 weeks. This is because a special version of the PWM series is required with Australian approvals and it is manufactured to order. You may see stock of other voltages offered for sale by international online sellers. Be careful, these are unlikely to have the required Australian electrical safety approvals.

All of the MEAN WELL PWM series LED drivers are available with MEAN WELL's 3-in-1 dimming.

This means the LED driver is compatible with the following types of dimmer switches and controllers:

• 0-10V (or 1-10V) dimmer switches (such as the D1-10). If a 1-10V dimmer is used the LED driver will only dim down to 10%.
• Home automation and lighting control systems that use either a 0-10V output, or PWM control signal. (Includes 1-10V controllers, but these will only dim down to 10%)
• Potentiometers, or fixed value resistors.

The 120-watt version of this LED driver is also available with a DALI dimming option. The 60 WATT version will soon be available with the DALI dimming option.

Click HERE to browse the PWM series LED drivers, compare models, download datasheets and place online orders.

Warranty

Both the Power Source PDV series LED drivers and the MEAN WELL PWM series LED drivers come with a 5-year warranty.

Have a Question?

If you have any questions about selecting the right LED driver for your application please do not hesitate to contact Power Supplies Australia.

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