Converter for feeding fluorescent tubes for the illumination of railway carriages

摘要

The converter for feeding fluorescent tubes for the illumination of railway carriages solves the problem of feeding fluorescent tubes for the illumination of mobile and stationary objects from a DC source. The essence of the converter according to the invention resides in the fact that the inductance of the primary winding (N1) of the transformer (TR1) and of the capacitors (C1, C7) forms a tuned circuit during the starting phase of the fluorescent tube (FC), which tuned circuit, excited by a MOSFET transistor (T2), generates a positive half-cycle of a sinusoidal voltage. This voltage starts the fluorescent tube (FC) via the secondary winding, which is composed of the windings (N2, N3, N4, N5). After the start of the tube (FC), the tuned circuit is damped and feeds the fluorescent tube (FC) with a constant alternating current. The voltage for heating the cathodes of the tube (FC) is supplied by the windings (M2, M4) of the transformer (TR1); this voltage is reduced during the on-phase. The converter according to the invention is realised with only one MOSFET switching transistor, one transformer and one pulse-width modulator with the application of an adaptive feedback. The novel solution without using an inductor and a push-pull circuit is more economic than the known solutions and, at the same time, has excellent technical properties. <IMAGE>