Abstract
Using a new transistor inverter, fluorescent lamp ballast of light weight and high efficacy is achieved.
The inverter is composed of a power transistor, a semiconductor diode, two small inductors, two capacitors and trigger unit which drives the power transistor.
Switching the power transistor with LC circuit, a. c. power of 15-20 k Hz is generated to operate fluorescent lamp.
The inverter has features suitable for a ballast.
(1) Output voltage is much higher than the source voltage and decreases with decreasing value of load resistance. Hence it is possible to operate the lamp with source voltage lower than tube voltage.
(2) Output current is approximately constant at lower value of load resistance. The characteristics is favorable to regulating the lamp current.
(3) Output power depends on the trigger frequency. The characteristics is useful for dimming or lighting controls and also useful for regulating the lamp power against the fluctuation of source voltage.
Using the inverter, the 20 watt lamp ballast with 24 volts source and the 80 watt lamp ballast with 100 volts source are made.
The ballast is simple compared with other electronic ballasts. Single power transistor is employed and step-up transformer is not used.
