TRANSFORMER

摘要

A transformer is described for use in a static inverter in association with one or two switching devices, typically transistors, as in a high frequency switching series ballast circuit for a gas discharge lamp 12. The transformer produces an output for control of the transistor 13 which changes in sense as a function of the flux level in the transformer core. The arrangement is applicable to figure "8" cores, such as are assembled from two "E" cores, and requires only a single aperture 28 located at the base of the central leg. Control is effected by a single primary 16 and single secondary winding 17 wound through the aperture. With two switching devices, two apertures are normally provided. In operation, transistor 13 is switched on at 22KHz by an oscillator 20 and current flows therethrough to the aperture primary winding 16, main winding 15 in series therewith, and lamp 12. The windings 16 and 15 produce fluxes phi c and phi m that reinforce over one area (31), Fig. 4A (not shown) adjacent the aperture 28, eventually producing saturation there. The main flux phi m is thereupon diverted to pass round the aperture in the opposite sense, Fig. 4B (not shown), thereby reversing the current induced in the aperture secondary winding 17 and turning the transistor 13 off. Current to the lamp 12 is, however, maintained until the transistor 13 is again turned on, by current flow through a diode 19 and the main winding 15. Trigger pulses from the oscillator 20 are fed to a third winding 18 in the aperture 28.