Starter circuit for pre-heated gas discharge lamp - uses series choke coil inducing HV pulse for ignition of lamp and logic stage detecting voltage across lamp to detect ignition for controlling heating current

摘要

The circuit has the heating current supplied to the lamp (LA) at each zero transition of the supply current half wave of given polarity, as long as the discharge lamp is not ignited, with a logic stage determining the voltage across the lamp during the opposite polarity halfwaves, to detect the lamp ignition. The lamp is connected in series with a current limiting choke coil (L1) in which a HV probe for ignition of the lamp is generated. Pref. the logic stage uses two NAND gates (G.2, G.3) providing a RS flip-flop responding to the heating current dropping below a given threshold value to control a semiconductor switch (TR1) for interrupting the heating current and generating the HV ignition pulse via the choke coil. ADVANTAGE - Reduces time between starting lamp pre-heating and lamp ignition and can be used for lamps with different ignition voltages without modification.