Abstract: A circuit arrangement for preheating electrodes of a discharge lamp connected in series with a ballast by means of a supply voltage of alternating polarity. The circuit arrangement is provided with a switching element (S) which shunts the lamp and which is operated by means of a control signal. A circuit portion (II) adjusts both the phase and the frequency of the control signal in dependence on whether the ballast is inductive or capacitive. The electrodes of the lamp are preheated in a short period both for an inductive ballast and for a capacitive ballast.

Abstract: An ignitor circuit for a gas discharge lamp includes a transformer and means for generating pulsatory voltages across a primary winding of the transformer to generate ignition pulses by means of a secondary winding of the transformer. The ignitor circuit further includes first means for measuring an amplitude of the ignition pulses, and second means for changing the pulsatory voltage across the primary winding, and thus changing the amplitude of the ignition pulses, in dependence on the measured amplitude of the ignition pulses. The ignitor circuit is capable of generating a suitable ignition pulse over a wide range of connection cable lengths.

Abstract: A transformer (10) which forms part of a lamp ignition switching device has at least its primary winding (12) composed of a foil. Moreover, the transformer has an air core. In this way a satisfactory coupling, which is also maintained at high temperatures, is obtained between the primary (12) and the secondary (11) winding. This switching device is very suitable to be built in a lamp and to ignite the lamp at a high temperature.

Abstract: A high-pressure sodium discharge lamp comprising a discharge vessel (3) provided with an external auxiliary electrode (11) and a built-in electric starting circuit including an electric circuit comprising a transformer winding (35a), a capacitor (33) and a semiconductor switching element (34). The circuit is connected in series with a resistor (32) electrically parallel to the discharge vessel (3) and with the transformer (35) electrically connected to the external auxiliary electrode (11). The semiconductor switching element (34) is an uncontrolled voltage-dependent breakdown element of the thyristor type having a breakdown current smaller than 1 mA at a breakdown time shorter than 10 .mu.s. The resultant lamp starts very reliably and its build-in starter dissipates only a very low power.

Abstract: In a circuit for an inductively stabilized discharge tube (1) provided with two preheatable electrodes (2, 3) the ends of one electrode (2) are connected via a first capacitor (22) and a second capacitor (24), respectively, to the corresponding ends of the other electrode (3). The second capacitor (24) remote from the supply is shunted by a PTC resistor (23). The discharge tube (1) and inter alia the PTC resistor (23) form part of a lamp unit. The discharge tube (1) ignites readily even at low ambient temperatures. In the lamp operating condition, the influence of the PTC resistor (23) is neglible.

Abstract: An electronic device (20-61) for the starting and a.c. operation of a capacitively stabilized discharge lamp (7) includes a controlled semiconductor switching element (22) which, in the operating condition of the lamp, is briefly conductive in each half cycle of the AC supply. The control circuit of the semiconductor switching element (22) includes a second switching element (25) which, during the starting procedure of the lamp, ensures that the semiconductor switching element (22) is made conductive only every alternate half cycle thereby to improve the ignition of the lamp.

Abstract: The invention relates to a d.c. to a.c. converter comprising two transistors (22, 25) and an output transformer (21). This converter also includes an auxiliary d.c. voltage source (43) and is provided with an auxiliary winding (40) of the transformer (21) which connects the base of one transistor (22) to the base of the other transistor (25).According to the invention, the combination of the auxiliary d.c. voltage source (43) and a control circuit of the two transistors (22, 25) comprises a current blocking means (44) such that the converter can be supplied with a pulsed d.c. voltage. Consequently, that converter can be operated from a low frequency a.c. voltage mains via an auxiliary full-wave rectifier (5 to 8), which does not need to have a high value smoothing capacitor.

Abstract: The invention relates to an electric arrangement comprising two series-arranged discharge tubes which are provided with preheatable electrodes and which are stabilized by means of a relatively small ballast. The tubes are shunted by a semi-conductor switching element which operates in the operating condition of the tubes.According to the invention a control circuit of the semi-conductor switching element includes a non-linear circuit element which ensures that the discharge tubes do not ignite before the electrodes are in the warm state.

Abstract: The invention relates to a starter for igniting a low-pressure sodium lamp. The starter is provided with an oscillator circuit consisting of an electric coil, a first capacitor and a controlled semiconductor switching element.In accordance with the invention the starter also comprises a parallel circuit of a resistor having a positive temperature coefficient and a second capacitor, this parallel circuit and the oscillator circuit being in series. This series circuit is connected between two electrodes of the lamp. In the case where a defective lamp must be replaced by a new lamp--the supply voltage being switched on--in spite of the hot state of the resistor with positive temperature coefficient a plurality of starting pulses will nevertheless be passed through the second capacitor to the new lamp whereafter this lamp can ignite.