Fluorescent lamps are a very popular form of illumination, especially in offices and workplaces, but also increasingly in domestic applications. However, one drawback with fluorescent lamps in comparison with incandescent lamps, is that it is much harder to provide a dimmable lamp. The main reason for this is that a certain minimum voltage must be applied to the lamp in order for the discharge that is the source of illumination to occur. If the applied voltage goes below this minimum, the discharge may not strike and the lamp will simply go out. Thus controlling the lamp's power output by simply varying the applied voltage (as is done for incandescent lamps) is generally unsuccessful.
Conventionally fluorescent lamps are driven by ballast circuits. Originally such ballast circuits were electromagnetic, but more recently electronic solid-state ballast circuits have become preferred. Such electronic ballasts are effectively switched mode power electronic circuits and have a number of advantages including improved efficiency of the overall system, higher lumen output per watt and longer lifetime of the lamps.
USPTO Backgrounds
USPTO Backgrounds