How Does a Lamp Ballast Work?

Unlike incandescent bulbs, fluorescent and high-intensity lights use lamp ballasts to illuminate the gas-filled bulb chambers and to regulate the current flowing through the lamp. Basic neon lights and light-emitting diode bulbs (LEDs) use a fixed resistor as the lamp ballast, while other lighting devices use more complex electronic and computerized ballast controls. Find out more below about how a lamp ballast works.

Fixed Resistor as Ballast

The fixed resistors employed in neon signs and LED bulbs have a large resistance capacity compared to the amount of current that usually flows through the lighting device. The resistor is able to control the current so the light works correctly and continuously without overheating. Should a surge in the current occur, the resistor rises in temperature to absorb the extra current. If the current is too strong, the resistor will fail and the light will go out.

Self-Adjusting Ballasts

To prevent ballast failure self-adjusting ballasts were developed that can rise in temperature and resistance capability or reduce their temperature and resistance as the voltage decreases. These self-adjusting ballasts even out the changes caused by surges or drops in electric current, protecting the light's electrical circuit from failure, and result in net energy savings over the lifetime of the lighting device.

Digital Lamp Ballasts

Digital high-intensity lights (DHID) are controlled by a ballast equipped with a microprocessing circuit to provide the most efficient starting power to the bulb and the most sustainable electric flow while the light is in use. The DHID ballast has proven more effective than magnetic or simpler self-regulating ballasts in controlling light production as the lamp bulbs age, and can be connected to motion detectors to reduce light levels when an area is not in use.

Electronic Ballasts

Electronic ballasts adjust the power frequency upward from the standard electrical current of 60 Hz and can boost it to 20kHz. This helps eliminate flicker in fluorescent light tubes, which has been shown to aggravate symptoms in people suffering from epilepsy. The lamp itself works more efficiently due to operating at a higher frequency.

Reactive Ballasts

Reactive ballasts are also called magnetic ballasts, due to a magnetic capacitor added to the power inductor to manage the electrical power being used by the lamp. Reactive ballasts used to start and sustain large light installations can be huge, and may emit a noticeable hum while operating.

Fluorescent Light Ballast Types

Instant-Start Ballast

This energy-efficient ballast is used in circumstances where lights are rarely turned off. The instant start ballast does not heat the fluorescent light cathode ray tubes when it starts, but provides a jolt start with 600 volts of concentrated electric energy.

Rapid-Start Ballast

A rapid-start fluorescent light ballast warms the bulb cathodes and applies electricity to the gas in the bulb at the same time. It is most useful where lights vary between full brightness and dim light several times during the day.

Programmed-Start Fluorescent Ballast

Improving on the rapid start ballast, programmed-start fluorescent ballasts provide steady heat to the gas-illuminating filaments, then to the bulb cathodes. The programmed start ballast allows the light to turn off and on over the longest period, and sustains the bulb's useful lighting for longer than other ballasts.