LED Drivers

What are they and how do they work?

What is an LED Driver?

An LED Driver controls the proper current and voltage for an LED system. Each LED requires a certain voltage to turn on and a certain current that determines the intensity/light quantity. Previous light sources were thermal-effect heat emitters.

This thermal effect naturally provided a certain modulation so that the standard 50Hz from the mains usually did not cause a visible flicker. LED does not have this thermal effect. Want to know more about flicker?
A good LED Driver will provide a frequency high enough at a modulation the sufficient, to avoid unhealthy flicker. The LED Driver is thus the heart of the lamp and thus an essential part of a quality product. LED Drivers can be divided into 3 main groups.

Constant Current, Constant Voltage and Constand Power Output. There are also LED Drivers that use a combination of Constant Voltage and Constant Current.

What makes a good LED Driver?

LED Drivers come in many shapes and sizes. The quality ranges from wretched to outstanding. Price is usually a good indicator of quality. But certainly not always. A price can easily be inflated by inefficient distribution strategies.
Still, to get a good idea of the quality of an LED Driver, you can look at the things the LED Driver affects. Basically, these are the light and the electrical housekeeping of the circuit it is part of.

Frequency and modulation: a well-designed LED Driver has a secondary output frequency and modulation that is non-disruptive. More information or frequency and modulation read here: stroboscopic effect light

Intended service life and MTBF: A long service life obviously represents lower costs over the life of the product. In addition to the replacement cost of the product, there are also costs such as labor and other materials. In addition to target life, MTBF (mean time between failures / failure-free interval) gives about the probability within which a product will fail within its target life.

The project installed 100 LED Drivers that have 10,000 burning hours. Total time = 100*10,000 = 1,000,000 hours. The MTBF is 321,000 hours. This means that on average 3-4 LED Drivers fail under the test conditions. Over the course of a good 4 years, 3-4 defects can be expected to occur. Combined with the standard deviation, it is possible to monitor whether the dropout rate is within expectation.

Energy Efficiency: a well-designed LED Driver has good energy efficiency in its power class. This means lower energy consumption and therefore lower costs. Also, energy efficiency says something about the design of the LED Driver. High energy efficiency in the respective power class usually means better design. In addition, higher efficiency promotes longevity because less energy is lost to heat.

Power Factor & THD: the efficiency of the LED Driver in using the electrical energy it absorbs. A high power factor usually means a well-designed LED Driver. The advantage of a high power factor is the favorable capacity load it has on the power grid. The THD provides the other part for determining the capacity load of the grid. A high THD means greater harmonic distortion with consequences. Harmonic distortion can create safety hazards including failure of short-circuit protection.

Sleep consumption: since the new ERP regulation is in effect, in many situations LED Drivers are not allowed to consume more than 0.5 watts when the LED Driver is turned off.

Inrush current: many LED Drivers feature certain components that cause a current startup surge. This peak can be as much as 100 times the normal power consumption of the LED Driver. This startup surge is so powerful that it can damage electrical equipment or trigger the installation circuit breaker. A good LED Driver lists in its datasheet the maximum number of LED Drivers that can be connected to a given installation circuit breaker.

Dimmable/non-dimmable: the technique of dimming an LED Driver largely determines the load on the LED Driver and how it affects the power grid. The datasheet of a good LED Driver clearly explains how certain load affects THD and PF as well as frequency and modulation (when relevant).

Constant Current LED Driver

A Constant Current (CC) LED Driver provides a constant current. The voltage is variable and adjusts automatically, according to the requested voltage. Depending on the temperature and load, the requested voltage of the LED may vary. A CC LED Driver will overcome this variation due to the wider range voltage the CC LED Driver can supply. A lower voltage means lower power and therefore lower light output. This is something that should be considered in the design of the lamp.

Constant Voltage LED Driver

A Constant Voltage (CV) LED Driver provides a constant voltage. The current is variable and is usually determined by the demand in the system on the secondary side. A CV LED Driver will not compensate for the difference in voltage demand of an LED. This should be taken into account in the design of the lamp.

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Constant Power Output LED Driver

In systems where constant equal light output is important, under changing conditions, there is the Constant Power Output (CPO) LED Driver. For example, consider temperature change in a greenhouse where the plants require a minimal amount of energy. A CC LED Driver cannot compensate for this and a CV LED Driver could compensate for this through a dimmer. There are LED Drivers that are a combination of CV and CC. Using this technique has pros and cons and should be considered beforehand.