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Ballasts, Transformers, and Drivers

Lighting sounds like a simple thing. Plug a lightbulb into a socket and turn on the switch, right? While incandescent lights are often that simple, energy-efficient and high-power lighting requires a little more effort (and some extra devices) for installation and operation. At some point or other, you’ve probably heard of ballasts, transformers, and drivers. While they aren’t all the same thing, they all serve a similar function for the systems they operate. Allow us a moment to illuminate the differences.


What They’re Used For: Fluorescent and HID lights, Outdoor Signage

What They Do: Control current and limit power surges to protect the lamp

Fluorescent and HID lamps are both very susceptible to variations in electrical current on their circuits. Both types of lighting also have different power demands during their power on cycle. The cost to power a fluorescent lamp throughout the day is less than how much power it takes to start the lamp initially. Many types of HID lamps also have set power-up and anti-cycling requirements. The heat from an HID lamp makes it susceptible to damage if not given enough time to cool before restarting.

All of these special considerations are taken into account by the lamp’s ballast. Different ballasts offer different options. Some allow for rapid restarting of lamps, or fast on-times (usually at the expense of lamp-life), while others promote longevity for the individual lamps but require a little extra time to warm up. In the end, these lamps regulate the power heading to your lights by regulating current flow. The ballast is also responsible for detecting demands placed on the circuit and giving necessary protections during startup.

Ballasts come in multiple designs, your electrician can help you identify the type of ballast needed for your application, but the type of ballast (and the types of lamps it’s capable of operating) are typically listed on a label found on the ballast itself. Many fixtures come with a built-in slot for a ballast as well.


What They’re Used For: LED lights

What They do: Control current or voltage to operate sensitive electronics

While electrical drivers have existed in onboard circuits for a while (they regulate power on the board and allow for changes in different circuits), they’ve become essential as a dedicated device for LED lighting systems. Electrical drivers regulate voltage and current to ensure proper operation of LED lights and devices.

LED drivers typically come in two forms, Current Limiting and Voltage Limiting. As the names imply, the power regulation is done by controlling the maximum and minimum voltage or current levels being sent to the device. According to Ohm’s Law, if you hold either the voltage or the current at a set level then, since the resistance in the circuit is not going to change, you will control how much power is going to the device.

LED drivers do just that. By controlling either the voltage or the current, they prevent dangerous overloads for LED systems that are connected to home and building wiring.


What They’re Used For: Almost everything

What They Do: Change voltage levels

Transformers are one of the most common electrical devices in any system. The power brick connected to your laptop? It has a transformer inside. Those large cylinders on the transmission pole outside? Also transformers.

While they aren’t disguised as anything, these transformers do a very important job: they convert voltage from one level to the next. Your home operates on 120 volts of AC electricity. A transformer steps this voltage down to make it usable by a device. While your incandescent lights can use 120V for light, your phone computer operates on 5 and 12 volts of DC electricity.

Likewise, the 33 kV transmission line outside is too high for use in the home, so the transformer steps the voltage down for use in the home.

Ballasts, transformers, and drivers all work to regulate power for devices. Each has its own uses and applications but they’re still very similar. If you have any other questions about these devices, or think you may need a replacement for an existing installation, don’t hesitate to call a professional electrician.