What Is an LED Driver? How to Choose the Right One

An LED driver (also called an LED power supply or LED transformer) is the part of an LED light that turns mains electricity into the DC power that LEDs need, and keeps that power steady. A wrong or failing driver is a common cause of an LED strip or downlight that flickers, runs dim or fails early. This guide explains what a driver does and how to pick one.

What is an LED driver?

An LED driver is a power supply that converts 230V AC mains into DC and regulates it so the LEDs get a steady current or voltage. Without it, LEDs overheat and become unstable, which leads to poor performance or early failure. Almost every LED light has a driver, either built in or as a separate box.

Think of it as cruise control for the LED. LEDs are sensitive to the current that flows through them: too much and they run hot and wear out quickly, too little and they look dim. The driver holds the output where the LED was designed to run, even when the mains supply varies a little.

Do all LED lights need a driver?

Almost all do, but you do not always see it. Screw-in and plug-in bulbs, such as E27 and GU10 LED bulbs, have an internal driver inside the base, so they connect straight to a normal 230V lamp holder. LED strips, panel lights, many downlights and outdoor fittings use an external driver: a separate box wired between the mains and the light.

Some low-voltage lamps also need an external supply. Our 12V MR16 LED bulb, for example, runs from a separate 12V supply rather than straight from 230V mains.

External drivers have one practical advantage. The driver often fails before the LEDs do, and a separate driver can be replaced on its own instead of replacing the whole light fitting.

Constant current vs constant voltage: what is the difference?

Every LED driver is either constant current (CC), constant voltage (CV), or able to work in both modes. A constant current driver fixes the current (for example 350mA or 700mA) and lets the voltage vary. A constant voltage driver fixes the voltage (usually 12V or 24V) and lets the current vary. The LED's datasheet or label tells you which one it needs.

Constant current drivers

A CC driver keeps the current constant by adjusting its output voltage. It is the usual choice for downlights, panel lights and single high-power LEDs, where the LEDs are wired in series. Series wiring gives good control and efficiency, but if one point in the chain breaks, none of the LEDs on that chain will light.

Some CC drivers have a selectable or adjustable output, such as stepped values of 350mA, 500mA and 700mA, or a range such as 0 to 500mA. Set the driver to the LED's rated current or slightly below it, never above. Running an LED at a slightly lower current can extend its life; running it above its rating wears it out much faster.

Constant voltage drivers

A CV driver supplies one fixed voltage. It is what you need for LED strip lights, because a strip is made of short sections wired in parallel, and each section already has its own current-limiting resistor or regulator. The driver's voltage must match the strip exactly: a 12V strip needs a 12V driver and a 24V strip needs a 24V driver.

Mean Well's LPV-60 series is a typical example of a CV LED power supply. Its official datasheet lists a constant voltage design, a 90 to 264V AC input (which covers Singapore's 230V mains), and 60W models at 12V / 5A and 24V / 2.5A.

How do I choose the right LED driver for an LED strip?

Match three numbers: voltage, wattage and current. The driver's output voltage must equal the strip's voltage (12V or 24V). Its wattage must be higher than the strip's total load, which is the watts per metre multiplied by the length. Then check that the rated current covers the load. Leave headroom so the driver does not run at full power.

1. Find the strip voltage. It is printed on the strip or reel, usually 12V or 24V. Never connect a 12V strip to a 24V driver: it will overheat and fail. A 24V strip on a 12V driver will run dim or not light at all.
2. Work out the total load in watts. Multiply the watts per metre by the number of metres you will install.
3. Pick a driver rated above that load. A driver running at its full rated output runs hotter and has a shorter life, so leave a margin.
4. Check the current. Amps = watts ÷ volts. The driver's rated current must be higher than the result.
5. Check the location. Indoors in a dry cabinet or false ceiling, or somewhere damp or outdoors that needs a waterproof rating (see the IP section below).

Worked example: sizing a driver for a COB LED strip

Our COB LED strip is rated at 11W per metre and comes as a 12V 5m reel or a 24V 10m reel.

The same method works for our SMD 2835 LED strip (also 11W per metre, in 12V or 24V). Note that 230V neon and 230V waterproof strips are a different system: they are rated for mains voltage, so they do not take a 12V or 24V driver.

On long runs, the far end of a low-voltage strip can look dimmer than the start because of voltage drop along the strip. Feeding power to both ends, or splitting it into shorter runs that are each fed directly from a driver, keeps the brightness even. Check the strip maker's recommended maximum run length.

How do I choose a constant current driver for downlights and panels?

Read the LED module's label or datasheet for its rated current (in mA) and its forward voltage range. Choose a CC driver whose output current matches the rated current and whose output voltage range covers the module's voltage. The driver's power rating should be at least the module's wattage.

In practice, most downlights and panel lights come with a matched driver, and the manufacturer specifies which driver to use with each fitting. When one fails, the safest replacement is the same model, or a driver with the same output current, a voltage range that covers the module, and an equal or higher wattage. If you are replacing the LED board itself, see our LED replacement modules.

Can you dim an LED driver?

Only if the driver is sold as dimmable. A non-dimmable driver or LED connected to a dimmer may flicker and can be damaged. Check the label or datasheet for the word dimmable and the dimming method, such as TRIAC (phase-cut), 0-10V or DALI, and make sure your dimmer or controller uses the same method as every driver on that circuit. For LED strips, use a dimmable power supply or a strip dimmer fitted between the power supply and the strip.

What do IP ratings mean for LED drivers?

The IP (ingress protection) rating has two digits. The first is protection against solids and dust, and the second is protection against water. A driver inside a dry false ceiling does not need a high rating, but one in a bathroom, kitchen, balcony or outdoor area should be rated for damp or wet conditions.

• IP65: dust-tight and protected against water jets, suitable for areas that may be splashed or rained on.
• IP67: dust-tight and protected against temporary immersion in water.

Read the datasheet notes as well as the rating. Mean Well's LPV-60 datasheet, for example, describes the series as fully encapsulated to IP67, but notes it is suitable for indoor use, or outdoor use without direct sunlight exposure, and should not be immersed in water for more than 30 minutes.

Do LED drivers need the Safety Mark in Singapore?

Yes. Singapore's Consumer Product Safety Office lists lamp control gears, which include LED drivers, as Medium Risk controlled goods under the Consumer Protection (Safety Requirements) Regulations. LED drivers are tested against IEC 61347-2-13, and suppliers must register them before sale. When buying a driver in Singapore, look for the SAFETY Mark on the product.

The CPSO list of controlled goods gives the current standard for each product category. The CPSO also states that household electrical appliances must be tested, registered and affixed with the SAFETY Mark before they can be sold in Singapore.

When should you replace an LED driver?

A failing or overloaded driver is a common cause of LED lights that flicker, blink on and off, or stop working while the LEDs themselves look undamaged. Before replacing the driver, note its output type (CC or CV), output voltage or current, and wattage from its label, and match or exceed them with the new one.

Switch off the power before touching any driver. Plug-in strip adapters are easy to swap yourself, but drivers wired into the ceiling or a fixed circuit should be replaced by a licensed electrical worker.

Need help matching a driver to your lights?

Send us the label or a photo of your LED strip, downlight or old driver and we will help you work out the voltage, wattage and current you need. Contact 123 LED Lighting or visit us at Sim Lim Tower.

Need help choosing LED lighting for your home or office? Ask our team.