Ballast for discharge lamps

摘要

A series circuit consisting of an inductance (L) and a fluorescent lamp (LL) is connected in the transverse branch of a switch bridge (SB). Two diagonally opposite switches (T1, T4) or (T2, T3) respectively of the switch bridge (SB) are in each case switched on. The current which is supplied to the switch bridge is regulated by a switched-mode regulator (K). The electrodes (E1, E2) of the fluorescent lamp are connected in series with a second switch (TVH) which is controlled to switch on for preheating of the electrodes. Starting takes place by multiple operation of a third switch (TZ) which cancels a short-circuit to the fluorescent lamp so that the inductance (L) produces a high starting voltage. The ballast can be constructed for a relatively large number of parallel fluorescent lamps. <IMAGE>