What is a Constant Voltage LED Driver?

3 September 2021

The answer is quite simple: It is a LED driver which allows the output current to fluctuate in order to maintain a constant voltage output to your LEDs.

There are two types of LED driver: Constant Voltage and Constant Current.

The type of LED driver you need to use purely depends on the way the LED manufacturer has designed their LED strip or LED lights.

Constant Voltage LED circuit designs

Low cost LED strips and lights are usually built according to a very simple design with power being supplied the LED strings coming from a constant voltage LED driver. A resistor is used on each string of LEDs to limit the current (as shown in the below diagram). This avoids damage to the LEDs if too much current is supplied.

simple constant voltage LED strip design


Although this design has a low level of complexity and is a low cost solution, it has poor current regulation and low efficiency.

If a LED within a string fails, or draws more current than it should this will cause an imbalance in the circuit, which will adversely affect the performance of the LED light.

Manufacturers of quality constant voltage LED lighting products will use a better design, which incorporates a constant current LED driver IC to supply the power to each string. (see diagram below).

constant voltage LED strip design

This design ensures that the optimum current is delivered to each LED string to ensure maximum efficiency. It is also able to cope with a single LED failure, as the constant current LED driver IC will detect the imbalance in the circuit and adjust its output accordingly.

Naturally it is more expensive to manufacture constant voltage LED products using this design, which is why you see a difference in the price of different LED strips.

For both of the above designs to work correctly they need the incoming voltage to remain constant.

This is where the constant voltage LED driver comes in. It incorporates circuitry to ensure that the voltage being supplied to the LED strip or light fitting remains constant, regardless of any fluctuations that may occur to the AC power being delivered from the wall socket.

To achieve this it allows the current to fluctuate.

Let’s take a look at how current and voltage relate to each other in LED drivers.

A 150 Watt 12V constant voltage LED driver would normally deliver the 12V at 12.5 Amps.

To calculate the power output (Watts) of a LED driver you multiply the voltage by the current.

So, 12V x 12.5 Amps = 150 Watts (12 x 12.5 = 150).

If we had a 150 Watt 24V constant voltage LED driver, it would deliver the 24V at 6.25 Amps.

24V x 6.25 Amps = 150 Watts (24 x 6.25 = 150).

So you can see there is a relationship between the current and voltage, when determining the power (Watts) in a circuit.

If there are fluctuations in the incoming AC power supply they will affect the DC output being supplied to the LED light strip or fitting. As it is the voltage that must remain constant the LED driver will allow the current to fluctuate accordingly so that the LED driver can compensate for the fluctuations in the incoming AC power and maintain the required constant voltage output.

If you find that you need a constant voltage LED driver, then we invite you to browse the range of products shown on this website. If you cannot find a model that is suitable, please do not hesitate to contact MEAN WELL Australia, we will only be too happy to advise you which model is best suited to your own particular application.