The two main types of lamp ballasts are electronic ballasts and magnetic ballasts. Magnetic ballasts are an older technology, but they still have applications in lamps that require a considerable amount of energy to operate. One advantage to electronic ballasts is that they do not cause light bulbs to flicker as much as magnetic ballasts.
Both types of ballasts have limited but very important functions. They are used to control the amount of energy that goes into a light bulb at one time. They also supply a starting voltage to the light bulb.
One of the most widely used types of electronic ballasts is the adaptable ballast. Adaptable ballasts are used in instances where several lamps need to be operated under one single ballast.
All HID, or "high-intensity discharge," lamps use ballasts. This includes lamps such as metal halide and high-pressure sodium lamps. Fluorescent light bulbs require ballasts to operate properly.
The Lighting Research Center claims that certain light bulbs hooked up to high-voltage sources of power would instantly overheat and burn out if the energy flow into the bulb were not restricted by a ballast.