摘要 |
<p>A ballast adaptor circuit which makes it possible to use a known rapid start ballast, designed for operating two T12 (38 mm diameter) fluorescent lamps, for operation of two T8 (26 mm diameter) fluorescent lamps (14, 15) by means of a simple modification that does not require cutting wires or extensive rewiring of the ballast device. The adaptor circuit comprises an auxiliary circuit including a tuned series-parallel LC network (21, 24) connected in parallel with either one or both of the lamps. The LC network is tuned to supply an odd harmonic current to the lamps (14, 15), preferably the seventh harmonic. Improved starting is achieved by adding a series RC circuit (27, 28) and a SIDAC trigger device (29) to the network to produce voltage pulses at the peaks of the AC supply voltage.</p> |