| 摘要 |
<p>Two (or more) gas discharge lamps (10, 110), each in series with a choke ballast (18, 118) across A.C. supply terminals (16a, 16a) are started by a single starter circuit (70), the lamps being connected to the starter circuit through respective rectifying diodes (150, 152). The starter circuit (70) operates with rectified half-cycles of the A.C. supply, and resistors (154, 156) balance the cathode heating currents between the two lamps. Preferably the starter circuit is rendered ineffective in a failed-lamp condition, and to this end (per DE-OS 28 16 415) it includes a thyristor (26) triggered by a control circuit which includes a capacitor (32) effective to increase the instantaneous applied voltage which is required to trigger the thyristor with successive cycles of the applied voltage after initial switch-on of the circuit. A Zener diode (30) is in series with the capacitor (32).</p> |
