Circuit for operating one or more lour pressure discharge lamps

摘要

Two lamps (LP1,LP2) are connected in series and supplied with current from a resonant circuit contg. an invertor (Q1,Q2). Their electrodes (E1-E4) are preheated from an auxiliary circuit including a semiconductor switch (Q3) with a resistive element (Z) in series. The voltage drop across the series combination of the resistance and semiconductor drain-to-source path in the low-impedance condition is sufficient to hold the switch in its conductive state.