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Abstract

A power supply for an electric insect trap having an electrocution grid and a fluorescent lamp for attracting insects to the grid employs an inverter to generate a high frequency alternating voltage. The alternating voltage is applied across the primary winding of a first transformer having a secondary winding for development of a current-limited voltage for operating the lamp. Due to large inductance, the secondary winding functions as a constant current source to the lamp, so that lamps having different voltage characteristics may be used in the same circuit. A high voltage transformer has a primary driven by the limited lamp current to produce a high voltage for the electrocution grid across its secondary winding. Current limiting is achieved, in part, by providing a selected amount of flux leakage between the primary and secondary windings of the first transformer. Alternately, current limiting for the high voltage transformer output is achieved by providing the high voltage transformer core with a selected amount of flux leakage. A capacitor connected in parallel with one primary winding of the high voltage transformer functions to filter out harmonics of the alternating voltage frequency or to cause the transformer to operate in a ferro-resonant mode. When operating in a pseudo-ferro-resonant mode, saturable, toroidal transformers for providing drive and feedback to switching transistors in the inverter are thermally coupled with the high voltage transformer core. Those toroidal core transformers function to change the frequency of the alternating voltage applied to the high voltage transformer to offset changes in its output caused by temperature induced changes in the saturation limits of its core. A capacitor for AC coupling the high voltage to a lamp cathode causes a field to be created between the lamp and the electrocution grid to assist in starting the lamp.

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