GB1300214A - Circuit arrangement for gas and/or vapour discharge lamps - Google Patents

Abstract

1300214 Starting and operating circuits for gas discharge lamps PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 March 1970 [22 March 1969] 13320/70 Heading H2H A circuit arrangement for starting and operating a high pressure mercury vapour discharge lamp 4 shunted by a series circuit including a capacitor 6 and thyristor 7, the thyristor being triggered by means of a breakdown device such as a Zener diode 9 whereby the capacitor discharges to generate high voltage pulses which are used to start the lamp 4. When the terminals 1, 2 are connected to an A.C. source and the terminal 2 is positive the capacitor 6 charges by way of a diode 8. During the next half period when the terminal 1 becomes positive and the sum of the applied voltage and the capacitor voltage reaches a value sufficient to break down the Zener diode 9 the thyristor 7 is triggered whereupon the capacitor 6 discharges through the thyristor and then becomes charged in the opposite direction. When the current through the thyristor becomes zero and thereby cuts off, the capacitor 6 then recharges in the original direction by way of the diode 8. The voltage peaks caused by the charging and discharging of the capacitor are applied to the lamp 4 and repeat until the lamp fires. When the lamp fires the voltage across the capacitor-thyristor circuit falls and the circuit then becomes inoperative. In other embodiments a transformer is placed in series with the lamp 4 and the secondary winding thereof connected to the thyristor trigger electrode. Furthermore the Zener diode 9 may be connected in series with the diode 8.