Posted by Doug Root on 6th Aug 2021

Electronic Ballasts: Purpose and Types

Have you ever stood underneath an old fluorescent light bulb, enjoying the ambient flickering and buzzing constantly emitting whenever the light was switched on? If so, then you were in the presence of one of the marvels of engineering - a magnetic ballast.

Alright, so perhaps the term “enjoying” itself enjoys a bit of poetic license. Truth be told, the sounds and flickering emitted by most lights that use magnetic ballasts are somewhat more annoying than pleasant. - hence the reason for better, modern alternatives.

Nowadays, very few lights still use magnetic ballasts. Most of them use some sort of electronic ballast (of which there are many types). To get into this, we need to offer a bit of a preface - what is an electronic ballast in the first place, or more properly, what is a ballast at all?

What is the Point of a Ballast?

Despite the method of operation of a lighting ballast (electronic or otherwise) they all perform very similar basic and essential functions. Namely, the purpose of a lighting ballast is to regulate both the line voltage and the current supplied to a light bulb during its several phases of operation.

We mentioned “phases of operation” because ballasts don’t simply hold voltage and current steady all of the time. For example, for some lights, ballasts provide a higher startup voltage in order to get the lamp to light up. After the light has lit up and reached its full brightness, the voltage may dip to operating levels, after which point the current supplied can be constant.

The reason for the regulation of current is that some types of lamps, like fluorescent lamps and HID (high-intensity discharge) lamps, can only operate effectively within a given range of supplied power. For example, if some lights were to be operated without a ballast, they would quickly draw power until they burned out, without anything in the circuit to stop them from overdrawing.

In essence, and without getting too lost in the fine details of operation, the fact that a ballast regulates current and voltage enables the lamp in question to start up efficiently, reaching and then maintaining its advertising brightness. Then the current supplied to the lamp is held constant so that the light output will remain equally constant and will not flicker or dim unduly.

Ballasts not only ensure efficient operation and consistent light output, but they also help to ensure longer lamp life. A lamp without a ballast would overdraw power, overheating and damaging itself. In almost any instance, the lamp would burn out immediately, but lamps that have the appropriate protection of well-suited ballasts enjoy longer lamp life, more efficient operation and more consistent performance.

What Types of Lights Need Ballasts?

If you’ve ever performed the simple operation of replacing an indoor incandescent lamp or screwing a new halogen flood light into an outdoor socket, you probably noticed that there were no other steps to take. Simply get a light of the proper voltage and wattage specifications that fits the socket, screw it in, and you are good to go. There are no other in-depth alterations you need to make. Not all lights are like this, and there are two specific classes of lights that require ballasts - fluorescent lamps and HID (high-intensity discharge) lamps.

Fluorescent lamps operate via the very basic and interesting principle of fluorescence, whereby a material (known as a fluorescent) will glow with visible light when it is irradiated with ultraviolet light. The inside surfaces of fluorescent lights are coated with fluorescent materials - like phosphor powder, which glows then the inner tube sheds UV light onto it. This specialized cascade of events is far more involved than the simple electroluminescence of incandescent and halogen bulbs, thus requiring a ballast to operate efficiently.

For you homeowners, you may have noticed that CFLs, or compact fluorescent light bulbs, which were designed to help provide a reasonable, green alternative to incandescent light bulbs, seem to need no ballast. This is apparently the case, as most CFLs are plug and play replacements for incandescent lights. However, looks can be deceiving. CFLs actually contain ballasts within their design; they do actually need a ballast, it’s just that they already come with them.

All HID lamps require a ballast as well, although the specifics of their operation may vary according to the style of bulb. In addition, some HID lamps may have ballasts built in, and it’s important to note that some HID lamps can only be burned in specific fixtures and oriented accordingly. Contact us for help regarding this.

These main classes of light bulbs need ballasts - but what about everyone’s modern favorite, LEDs, which are not actually light bulbs at all - well, LEDs don’t specifically need ballasts, but that doesn’t paint the entire picture.

Does an LED Light - Like an LED Retrofit - Need a Ballast?

Part of this has to do with the fact that LED bulbs are not actually lightbulbs. An LED, or a light-emitting diode, is a device made of a semiconductor material that glows when a given current is run across it. This frees them from the need for ballast - but it’s worth noting that some LED retrofits are designed to be compatible with ballasts that are currently in place. For example, depending on what type of LED you get to replace your T8 fluorescent lights, it may already be compatible with the fluorescent ballast that is already contained in the circuit.

Also, LED lights are not entirely free from this consideration. LEDs need a special unit that is somewhat similar, at least conceptually, to a ballast, and is known as a driver. Like a ballast, an LED driver supplies a constant current and voltage to an LED, allowing it to perform at optimal luminosity while protecting it from overdrawing and heat damage.

What Makes It an Electronic Ballast?

To simplify things as much as possible, electronic ballasts are devices that use circuits to control the voltage and the flow of electricity to a lightbulb, in order to start it and to maintain its operation.

There are several different types of electronic ballasts that are used with fluorescent lighting technology, and two of the more common among them are instant and rapid start ballasts. Don’t let the confusingly similar names fool you; they are not the same.

Instant start ballasts use a sudden voltage spike to start the lamp, which, though it is effective at getting the lamp to start up quickly, produces a lot of wear on the lamp over time. A convenient alternative to the instant start ballast is the rapid start ballast, which, instead of a voltage spike, uses heat to warm up the lamp prior to starting it.

Rapid start ballasts are not particularly effective in the cold, and are not energy efficient, but they do a good job of getting a lamp to start up right away.

Then there are HID ballasts, most of which can be categorized as either pulse start or probe start ballasts. Pulse start HID ballasts, like instant start electronic fluorescent ballasts, use a spike in voltage to start the HID lamp. They are efficient and help to secure better lamp life as well.

By contrast, probe start HID ballasts use two electrodes to create an arc through the tube to start the lamp. They’re not particularly efficient and have a long startup delay, and they’re somewhat rough on the lamp, so many lighting specialists prefer the use of pulse start ballasts instead.

Are There Other Types of Ballasts?

In addition to the different types of electronic ballasts available for HID and fluorescent lamps, as mentioned in the last section, there are also magnetic ballasts, which some fluorescent lamps still use. These are the aging types of ballasts that result in slow startups, dim operation, flickering and buzzing.

Magnetic ballasts rely on the technology of a transformer to regulate the voltage supplied to the lamp, in order to hold it steady. Since this is less precise than the modern electrical means employed by electronic ballasts, magnetic versions provide slower start-up times, delays, noises, flickering, and other undue complications. For the most part, they are being phased out by newer, updated models.

Not Sure If It’s an Electronic Ballast? Try This!

Let’s just say for the sake of exploring an interesting topic that you aren’t sure whether a light, such as an old fluorescent tube light, is using an electronic ballast or a magnetic one. You can, of course, dive into the electrical infrastructure to see just what type of ballast your light is using - or you can try this trick. Just be aware that this is not a scientific assessment but only an interesting technique.

If you aren’t sure whether the light in question is using an electronic ballast or a magnetic one, just get out your smartphone camera. It may be able to give you a strong clue as to what you’re working with.

Switch on the light, turn on the camera, and point the lens of the camera at the light bulb. If you can see black bars or stripes on the light or running across the phone screen, as though the light is flickering, you are almost certainly working with a magnetic ballast. A light using an electronic ballast would look more or less normal.

Please note that this technique does not work well if the camera is too far away from the light. Ideally, the closer the camera is to the light, the better. You should get within about five feet, if you can. Any farther (such as with lights hung in ceilings or high bays) and you won’t really be able to use this technique.

Get in Touch with Us for More Information

Still absorbing all of this information about magnetic and electronic ballasts for lighting infrastructure? Don’t try to parse the details alone. We’re never more than a call away and you can reach us at 1-888-988-2852 whenever you need us - just get in touch with us and we’ll help answer any and all questions you have about ballasts or lighting in general!