Do LED Bulbs Need a Transformer? (A Must Read!)

The internal components of LED bulbs are designed to work with low voltage (e.g. 12V or 24V). Depending on where you live your mains voltage would typically be rated 110-24-v, which brings us to why an LED bulb would need a transformer. Let me explain.

Do LED bulbs need a transformer? Yes, so long as an LED bulb is mains-powered, it will need a transformer to reduce mains voltage (240V) to the desired level relative to the bulb being powered, somewhere between 12V and 24V.  

What Are LED Transformers?

If you’ve been around electronics for a while, then transformers must be a common sight. Transfers are used to transfer electricity from one circuit to another. In addition, they can also be used to step down current. 

The idea behind transforming high-voltage currents to lower currents in the case of LEDs is to make the current safer and easier to manage. LED transformers employ the same strategy to power the diodes that produce light. 

When you tear down a transformer, what you’ll find are two interconnected coils. The primary coil connects to your mains, while the secondary connects to the LEDs. The primary coil in the LED transformers would have more windings than the secondary one, this ensures that the secondary coil has a lower voltage. Due to the design of the coils, the transformer can easily increase or decrease currents as needed by the LED circuit. 

The two most common LED transformers are magnetic transformers and electronic transformers. We will discuss them further down the line. However, first, we need to discuss when transformers are necessary.

There are two major types of LED transformers, they are magnetic and electronic transformers. I will discuss more on them later in this article, but before then, we’ll discuss whether or not transformers are necessary.  

Which LED bulbs require a transformer?

Did you recently replace your traditional bulbs with LEDs? If so, you must have noticed the light is housed within a plastic unit. In most light bulbs, the LED housing will contain all the electronic driver components required to power the bulb. 

This implies that you need not worry about any drivers/transformers as these are all part of the light bulb unit. If a bulb is designed with an integrated LED driver it can be used without the addition of an external transformer. Some examples of such bulbs include:

  • Bayonet bulb caps (e.g. B22)
  • Screw type bulbs caps (e.g. E26, E27)
  • Twist and lock style caps (e.g. GU10, GU24)

We often refer to transformers as drivers in the context of LEDs. 

However, it is more appropriate to think about transformers in the terms of LED lighting projects requiring a more powerful external supply.

Now you know what a transformer is and when it is necessary for use with LED bulbs, but do you know the differences between an LED driver and a transformer? Let’s get into that. 

What is the difference between an LED driver and an LED transformer?

When you have a transformer sitting between mains power and an LED bulb in an electrical circuit, you can think of both LED drivers and LED transformers playing the same role (i.e. Helping to reduce the current within the bulb to safer and manageable levels). But that’s where the similarities end, these two electrical components are distinctly different.

If you’re in the UK, your home should be supplied with mains power of around 240v. Let’s put things into perspective, LEDs designed for domestic use require 12-24 volts to run, which is a significantly reduced power supply, which is also crucial to the lifespan of the unit. This means the LED bulb will need a driver/transformer, The main difference between LED drivers and LED transformers is the power output: 

LED Drivers

In LED drivers, there is an upper power output of 100w – 200w. By implication, LED drivers are ideal for small LED lighting setups. Some LEDs may require 2-4V DC. However, a larger number of LEDs will require a much higher voltage. In such situations, an LED transformer can be installed. 

LED Transformers

LED transformers can regulate a lot more electrical power. The transformers are easily a solution for larger-scale LED lighting projects such as strip lighting (also known as ‘LED tape’).

LED Light Transformer Types

As we have previously mentioned, there are two common types of LED transformers. However, we should mention that different environments and use cases may require a more specialized form of LED transformers. Nevertheless, in this section of the guide, we will cover the types of transformers most available to you.

As I earlier mentioned, there are two common types of LED transformers available to you. But keep in mind, there are other more specialized forms of LED transformers depending on the use case. 

Magnetic Transformers:

These transformers are easily a favorite amongst professionals, all thanks to their reliability. They consist of primary and secondary coils. A noteworthy bit of their design is that the windings in the secondary coil are less than the windings in the primary coil.

Electronic Transformer:

Typically smaller and lighter when compared to its magnetic transformer counterpart. These transformers are miniature in form and are coupled with an inverter. The role of the inverter is to convert the frequency while the transformer changes the direction of the current. To give you a clearer illustration, let’s consider running a current from a 120-volt power outlet with 60Hz, it will increase to around 20K Hz. Though smaller, I do not recommend that you install these transformers in any LED lighting setup. 

Alternative LED transformers:

Dimmable Transformers:   Since transformers can regulate voltage, they can also be used to dim LED lights. 

Indoor Transformers: These transformers are smaller in size when compared to outdoor ones. They are easier to conceal. Manufacturers often equip them with fault protection. Furthermore, they are known to be very effective despite their size. 

Outdoor Transformers:  Unlike indoor transformers, these transformers are manufactured with heavy-duty waterproof housing. Therefore, they are impervious to rain, snow, etc. You can find some with IP69 ratings.  

How far away should I house the LED transformer?

When planning your LED lights setup, a critical issue to address is the acceptable maximum distance at which your power supply should be positioned from the LED light strip. 

Here’s why distance matters, the further an LED transformer is from the LED light strip, the more likely you are to experience a dip in power supply reaching the strip. 

However, it all depends on the quality of the electrical cabling connected to the lighting strip, including the load capacity of the cable. The next section provides you with cable gauges and the corresponding length for the best results. 

Maximum distance of LED transformer from the lighting strip by cable type

0.75mm 5m

1mm 10m

1.5mm 15mm

2.5mm 20m

Can multiple LED strip lights be powered by a single transformer?

Yes. Multiple LED strip lights can be powered by a single transformer, so long as the load limit of the transformer is not exceeded by the total wattage of the connected LED light strips. Flickering and dimming are some of the side effects of an overloaded transformer. So be sure to check with a professional before loading up that transformer. 

Do all LED downlights need a separate driver?

Bulbs designed for use in wet places (such as pools and bathrooms), must be IP rated. By implication, each sealed bulb must consist of an LED driver, with no external transformer required. 

Before purchasing and installing LED downlights in other areas of the home such as kitchen ceilings, you must consider the electrical fitting. In cases where the ceiling is designed to house an MR16 bulb (a double-pin bulb), you must install a separate driver alongside the bulb. If you need a detailed guide on drivers for MR16, you can check the manufacturer’s product information or any reputable retail vendor of the product before purchase. 

Can I Install an LED Transformer?

Yes, you can install an LED transformer as long as you adhere to best practices. However, I do recommend that you consult with a professional before embarking on a large-scale lighting project. This will ensure that you’re properly guided on how to safely manage an external power supply fed through an LED transformer.

Frequently Asked Questions

How many transformers do I need for LED lights?

To determine how many transformers you need for your LED light setup, here’s what you need to do:Sum up the amount of LED tape you have in meters and multiply this by the wattage of the LED tape you have, again per meter. Let’s look at a typical example, 7m of 4.8w LED tape: 7 x 4.8w = 33.6w, the required transformer capacity would be 60w. 

Can I use a 12V transformer for LED?

Yes, you can use a 12v transformer with your LEDs. I recommend a magnetic transformer in this case. Previously used AC transformers used with halogen MR16 bulbs usually require a minimum of 15 or 20 watts to operate effectively.

Are LED transformers AC or DC?

LED transformers/drivers work to regulate and deliver safe and manageable currents used to ‘drive’ runs of LED strip lighting. Like traditional transformers, they transform mains voltage alternating current (240v AC) to a lower voltage. 

Do LED light strips require an LED driver or a transformer?

Most LED strips on the market will require a constant voltage supply to function, and this is typically supplied with basic AC/DC transformers, However, the power can also be supplied with LED drivers (e.g. DALI dimmable).

Do MR16 LED spotlights require an LED driver or a transformer?

Not necessarily, the LED MR16 spotlights require a constant voltage power source. This is usually 12V DC but many will also accept 12V AC. 

Do GU10 LED bulbs need a transformer?

No, they shouldn’t, GU10 bulbs are halogen bulbs originally, these bulbs can be powered directly through mains voltage. Pretty much any LED GU10 bulbs you get will be rated for line voltage as well and are direct drop-in replacements. If there’s a need for an external driver, it’ll be stated on the product box, as well as the line voltage.