Fluorescent Lamp Dimming Progress Report

The three types of fluorescent lamp dimming systems used today are variable voltage, variable impedance, and variable time. From the standpoint of performance, the variable-time system has proved superior. However, early variable-time dimming systems utilized the thyratron as the controllable switch, and the cost, size, and reliability of the system limited its success. With the introduction of the silicon-controlled rectifier, an economical, reliable, and compact variable-time fluorescent dimming system was made possible. A special dirmning ballast was designed to be used with the silicon-controlled-rectifier dimming control; this design is discussed in detail. The associated circuitry required by the silicon-controlled rectifier when used in a fluorescent dimming system is also included.