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LED Driver Vs Power Supply
Dec 07, 2018

What is an LED Driver?

An LED driver is a self contained power supply which regulates the power required for an LED or array of LEDs. The light emitting diodes are low energy, lighting devices with a long lifespan and low energy consumption, hence the requirement for specialized power supplies.

What is an LED Power Supply?

Properly powering a light emitting diode (LED) or group of LEDs is different than powering most electronics. While most electronics require a constant voltage source, LEDs require a constant current source. Most power supplies will provide a set voltage, such as 5V, and have a maximum current rating. The power supply will maintain this voltage and provide enough current to meet the demand of the circuit it is powering. This means a dedicated power supply would need to be implemented to drive any LEDs in a circuit.

LED driver

Difference between an Constant Voltage LED Driver 42 and a regular AC/DC Power Supply 20


In speaking with my product manager and his contacts here is the answer I was given.


At the top level, there is great similarity between a Constant Voltage driver and a general-purpose AC/DC power supply, however, there are certain parameters/specs that LED lighting applications requires that general purpose application may not be concerned about, e.g. flicker, ripple, efficiency, surge protection and dimming


For example, The DLC fixture efficiency spec is one parameters and the CA title 24 flicker spec is another that are not as critical for most general purpose AC/DC Power Supply (CV) applications as they are in some LED lighting applications. These requirements change from one lighting application to another, and a general-purpose AC/DC power supply may or may not pass all the LED lighting application requirements.


Even if a minority of the AC/DC power supplies do meet all those requirements, they can only cover the Constant Voltage portion of LED lighting applications which is no more than 5% of the overall market, as the overwhelming majority of the LED lighting applications need Constant Current drivers.


When Do I Need a “Constant-voltage” LED Driver?

Most commercially available LED “light modules” are constructed by connecting a number of LEDs in series or parallel to form cluster or string configurations. In cases where these light modules include a “constant-current”driver as part of the assembly, an external “constant-voltage” driver or power supply is required. Low cost LED circuits control the currentflowing through the LED with a simple resistor. This is another case where a constant-voltage power source is required. Other examples where “constantvoltage”supplies have been employed include backlit ad signs, traffic information signs and large screen high definition LED displays, such as those described in this article: http://www.ledsmagazine.com/products/20877. 

LED power supply

When Do I Need a “Constant-current” LED Driver?

In cases where a manufactured cluster or string of LEDs does not include an internal “constant-current” driver, an external LED driver or power supply that provides a “constant-current” is required. Constant-current LED drivers are available in many different package configurations, ranging from integrated circuits to enclosed moisture-proof packages, depending on the application and the required output power.


Why do I need to use a driver for my LEDS ?

 Choosing the right supply is key to ensuring that you get the best performance from your LED. LEDs with their long lifetimes now mean that the perception is that the weakest link is now the power supply. Excelsys has chosen design techniques, market leading components and thermal management techniques in order to provide solutions for customers with lifetime matching figures. We also have incorporated a number of design features which fit in nicely with the LED market requirements. 

 IP67 rated, waterproof metal casing and will probably be potted

  LEDs are non-linear devices (If vs. Vf) with a forward voltage that is temperature dependent – needs to be controlled by regulating current 

 LEDs are low voltage DC devices with a forward voltage requirements. LEDs also require protection against damage 

 Incandescent light bulbs are purely resistive load, LEDs are not. Drivers are required to provide a power factor close to 1 over all line and load conditions. 

 High Efficiency (driven by lumens per Watt demand by Luminaire designers) 

 High Reliability 

 High Lifetime (Power supplies now perceived as the weakest link in the chain), needs to be in the 10’s of thousands of hours. 

 UL8750 approved 

 Future designs will have capability to communicate with the power supplies


Selecting an LED drivers

Current and voltage mode: The LED drivers are either constant current or constant voltage.

The Constant current drivers provide a fixed output current and may have a wide range of output voltages. An example of a constant current driver is one with 700mA output current and with an output voltage range of 4-13 V Dc drivers.

The constant voltage LED drivers provides a fixed output voltage and a maximum regulated output current. These are sued to power led systems that require a stable voltage of say 12 or 24 Volts DC. a typical driver may provide 24V and a maximum output current of 1.04A

Physical size: to ensure that it fits in the area it is to be fixed.

Ingress IP rating of the casing gives an indication of the environmental protection provided by the outer casing of the driver against ingress of moisture, dust and other objects or liquids.

Other factors considered include the power factor, maximum wattage, dimming ability and the compliance with international regulatory standards such as the UL1310 in regard to safety.

For more details, contact us at email: info@razorlux.com.