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(11) | EP 1 133 215 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Method and ignition circuit for switching a high pressure lamp on and off |
(57) The invention relates to a method and an ignition circuit for switching a high pressure
lamp on and off. A load circuit is capable of being short-circuited by means of a
switch (3), which is connected in series with a primary winding (1) of a pulse transformer
(1, 2) and whose on-off control is also used for generating ignition voltage pulses
through a secondary winding (2) to a lamp (L). Upon a controlled closing of the switch
(3) conductively for an extended period of time, a current ballast (Lk) will be subjected
to a through-going short-circuit current for the load circuit and the lamp voltage
falls to such a low level that the lamp is turned off. This lamp turn-off function
can be used both for switching off a normally burning lamp and for terminating an
abnormal status of gas discharge of a lamp not ignited between ignition attempts,
in order to give the lamp a chance to cool down prior to another ignition attempt. |