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1. (WO1998051133) CIRCUIT ARRANGEMENT FOR OPERATING A DISCHARGE LAMP

Pub. No.:    WO/1998/051133    International Application No.:    PCT/IB1998/000555
Publication Date: Fri Nov 13 00:59:59 CET 1998 International Filing Date: Wed Apr 15 01:59:59 CEST 1998
IPC: H02M 7/5383
H05B 41/282
Applicants: KONINKLIJKE PHILIPS ELECTRONICS N.V.
PHILIPS AB
Inventors: BUIJ, Arnold, Willem
MICHIELS, Hendricus, Franciscus, Petrus
Title: CIRCUIT ARRANGEMENT FOR OPERATING A DISCHARGE LAMP
Abstract:
A circuit arrangement according to the invention for operating a discharge lamp (I) comprises a self-oscillating DC/AC converter (II) provided with a series arrangement A of a first and a second switching element (1, 1', respectively) between a first and a second input terminal (2, 2', respectively) for the connection to a DC voltage source (III). The series arrangement A supplies an alternating current Ib to a load branch having output terminals (6a, 6b) for connection of the discharge lamp (I) during nominal operation. The circuit arrangement according to the invention is in addition provided with a starter circuit ST comprising means (15, 12') for generating a DC voltage component between the control electrode (1c') and the main electrode (1a') of the second switching element (1'). The starter circuit ST is also provided with means M which comprise an auxiliary switch (25). The means M bring the first switching element (1) into a conducting state if the amplitude of the alternating current Ib is low compared with the amplitude during nominal operation. The means M counteract damage to the switching elements (1, 1') and promote the initiation of the nominal operational state.