LED Drivers – Constant Voltage or Constant Current?

LED Drivers – Constant Voltage or Constant Current?

There are two main types of LED drivers (also known as LED power supply); constant voltage (CV) and constant current (CC).

Constant Voltage

Constant voltage drivers used in LED lighting applications mainly usually have an output voltage of 12V or 24V DC. The main type of LED lighting that uses constant voltage is LED strip but some LED lamps and LED downlights also require constant voltage so it is important to check.

There are many types of power supplies available, ranging from plug-in laptop style to industrial din rail mount power supplies. Although many of these power supplies will work perfectly well they are not designed for use in lighting applications and don’t meet EN61347-2-13. Our latest range of Mean Well or Sun Power LED drivers are specifically designed for LED lighting applications and can even be dimmed!

Constant Current

Constant current drivers are commonly used to power LED downlights and higher output LED fittings and are available in various outputs, mainly 350ma or 700ma. Most of the complete LED downlights such as the Halers H2 or EcoLED featured on our website come complete with constant current LED drivers. These type of drivers supply the LED with a constant regulated current and ensure that no over current or under current occurs thus allowing the LED(s) to perform under optimum conditions.

When wiring multiple LEDs to a single constant current LED driver you must wire them in series as shown in the example below:

Efficiency

To achieve the optimum performance, maximum lifetime and efficiency from your LED driver we recommend loading to be around 70-85%.

Dimming

If you are looking to dim your LED strips or downlights, please contact us to discuss your requirements as we are able to supply a complete range of dimmable LED drivers, corresponding 1-10V dimmer switches and many other controllers. When loading 1-10V dimmable versions loading should be nearer to 100% as possible to achieve a wider dimming range.

Recently added to our range are mains dimmable LED drivers which will dim with leading edge and trailing edge switches. These are new to the lighting industry and are much easier to wire than 1-10V as you don’t need to install additional cables. These drivers are available in 3 wattages; 20W, 45W and 80W, for higher loads the drivers can be synced so you could have 3x80W drivers to run a 240W load, or more if required. Another advantage of using mains dimmable LED drivers is that when using systems such as Lutron you no longer need to order the 0-10V add on unit which saves on costs.

Drivers for LED Strips

If you are unsure about which power supply to use for your LED strip runs please contact us for advice. Feel free to send us a drawing or rough sketch showing what you want to do. We will do the rest and provide you with an easy to follow wiring diagram. We also offer a great range of DMX drivers and many LED controllers including Wi-Fi for Iphone control or RF including multi channel controllers that allow multiple LED strip runs to be controlled from one remote control.

Or if you already know the length of LED strip you require then try using our power supply tables:

LED Strip 12V Power Supply Tables

30 LEDs Per Metre (7.2W Per Metre)
Length of Strip Total Wattage Power Supply
Up to 10 Metres 72W

Plug In 72W

Up to 13 Metres 100W

Meanwell LPV-100-12

Up to 22 Metres

160W

High Efficiency 160W

High Efficiency LED driver 160W

 

60 LED Per Metre (14.4W Per Metre)
Length of Strip Total Wattage Power Supply
Up to 5 Metres 72W

Plug In 72W

Up to 7 Metres 100W

Meanwell LPV-100-12

Up to 18 Metres 264W

High Efficiency 240W

High Efficiency LED driver 240W

24 Metres 350W

High Efficiency 350W

High Efficiency LED driver 240W

Longer runs of colour changing strip will also require the use of an amplifier. The amplifier allows longer runs to be controlled using one controller. More than one power supply can also be used on the same run.

Please contact us for further advice on: 01706 521188 or send us a drawing when attempting longer, more complicated runs.

Low Voltage Transformers

Low voltage transformers operate on alternating current only, AC to AC and have an out put which is usually 12 volts. Unlike an LED driver which converts the incoming AC voltage to a DC output voltage, low voltage transformers simply drop down the output voltage.

They have been used extensively with low voltage MR16 halogens for years but with the arrival of GU10 (mains voltage) and LED lamps they have become less popular. Most MR16 LEDs still require 12V AC to allow them to be easily retrofitted in place of halogen.

Some low voltage transformers won’t work with LEDs at all, some will work but not dim them and some such as the Philips Certaline or Varilight range work perfectly, possibly down to minimum load requirements.

About the Author: Chris Horridge

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