US3740609A

US3740609A - Arrangement for the ignition and alternating current supply for a gas-and/or vapor discharge lamp

Info

Publication number: US3740609A
Application number: US00198838A
Authority: US
Inventors: J Moerkens
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1970-11-21
Filing date: 1971-11-15
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19
Also published as: NL7017064A; AU3579071A; FR2115886A5; DE2155488A1; AU458022B2; CA997411A; JPS5014469B1; GB1331821A; ES397181A1; BE775614A; DE2155488B2

Abstract

The invention relates to an arrangement for igniting and supplying a discharge lamp, particularly a long low-pressure mercury vapor discharge lamp of about 2.5 meter. Said lamp has a relatively high ignition voltage so that it can not be ignited with the aid of a normal glow discharge starter. According to the invention a circuit is used in which with the aid of a diode branch a voltage doubling is effected at which the lamp can be ignited. In addition this circuit includes a resistor having a positive temperature characteristic which, after ignition of the lamp, renders the diode branch inoperative. By using the voltage doubling, a glow discharge starter can be used which must, however, be proportioned for a voltage which is generally higher than the conventional voltage. The invention relates to an arrangement for the ignition and alternating current supply of at least one gas and/or vapor discharge lamp which includes two electrodes. An arrangement of this kind is generally provided with a stabilizing capacitor which, in the operating condition, is connected in series with the lamp, a series arrangement of a diode and a resistor being provided which in that condition is shunted by a branch including the lamp and is connected in series with the capacitor. A known arrangement of the kind mentioned above is described, for example, in U.S. Pat. No. 2,134,439. A drawback of this known arrangement is that once the value of the resistor arranged in series with the diode is adjusted, the so-called dark period of the lamp is rather long (at a low resistive value of the resistor), or the lamp starts with difficulty (at a high resistive value of this resistor). A long dark period means that the lamp does not emit light during a fairly large fraction of a period of the alternating supply voltage. This is detrimental as regards the luminous value of such a lamp, hence for considerations of efficiency. A difficult or very slow starting discharge lamp is likewise a drawback. An object of the present invention is to obviate or at least to mitigate the mentioned drawbacks. According to the invention an arrangement for the ignition and alternating current supply of at least one gas and/or vapor discharge lamp which includes two electrodes comprises a stabilizing capacitor which in the operating condition is connected in series with the lamp and in which a series arrangement of a diode and a resistor is present which in that condition is shunted by a branch including the lamp and which is connected in series with the capacitor. The invention is characterized in that the resistor is of the type having a positive temperature characteristic which in case of the arrangement being switched on, but the lamp not yet being ignited, has a resistive value which is at most twice the resistance of the shunting lamp branch in the ignited condition of the lamp, and in which in the situation of the lamp being ignited the resistive value of the resistor having a positive temperature characteristic is at least twenty times the resistance of the shunting lamp branch. An advantage of this arrangement is that during the starting operation the resistor having a positive temperature characteristic (P.T.C. resistor) has a relatively low resistive value. As a result the capacitor is charged quickly. This is effected through the diode. A voltage doubling across the lamp electrodes, thus occurring in a next half period of the supply voltage, may then lead to a quick ignition of this lamp. When, however, the lamp is ignited the P.T.C. resistor will exhibit a relatively high resistance value. Consequently, with the lamp ignited, the current flowing through the diode branch is then very low relative to the lamp current. As a result, the situation in the operating condition of the lamp is not much different from that of an ordinary capacitively stabilized lamp circuit. This means that the dark period of the lamp is relatively short and that substantially no direct current components in the operating condition are present in the lamp current. It is feasible that the lamp is not only stabilized through a stabilizing capacitor but through a combination of a capacitor and a coil. This coil might be located, for example, between the capacitor and a supply terminal. It is also feasible that this coil is present in series with the lamp, namely in the so-called shunting lamp branch which is connected in parallel with the series arrangement of the diode and the P.T.C. resistor. One solution to bring the P.T.C. resistor to a highly resistive condition when the lamp is ignited is to utilize the fact that upon the ignition of the lamp the current flowing through the diode branch and hence the current flowing through the P.T.C. resistor is slightly increased. This leads to an extra heating of this resistor so that it achieves a relatively high resistive value. Furthermore it is feasible to realize the high resistive value of the P.T.C. resistor in the operating condition of the lamp is realized by bringing this resistor into close heat contact with the lamp. It can be achieved that in the operating condition the hot lamp heats the P.T.C. resistor in such a manner that it is in the high resistive condition. The gas and/or vapor discharge lamp is, for example, a lamp which is not provided with preheated electrodes. It is, for example, a high-pressure discharge lamp. An arrangement according to the invention preferably serves for igniting and supplying a lamp whose two electrodes are of the preheated type and that those ends of the two lamp electrodes which are remote from the supply are connected together through a glow discharge starter, the ignition voltage of the glow discharge starter being greater than 90 percent of the effective value of the supply voltage. An advantage of this preferred embodiment is that special discharge lamps such as, for example, low-pressure mercury vapor discharge lamps of a type having a relatively high ignition voltage, can be ignited by means of a glow discharge starter. As a rule other provisions, for example, transformers or electronic starters are required for the ignition of this kind of lamp. In a given embodiment of the above-mentioned preferred arrangement the glow discharge starter is proportioned in such a manner that its contact (formed by two electrodes) already close at a power of less than 0.5 Watt. An advantage thereof is that in the situation when the arrangement is switched on but when the lamp is not yet ignited the current flowing through the glow discharge starter and hence the current flowing through the P.T.C. resistor can be maintained low. This has the advantage that the P.T.C. resistor can readily be maintained in its relatively low resistive condition. The following may serve to explain this. In a situation in which a lamp, having preheated electrodes, and a glow discharge starter are used the capacitor charged through the diode and the P.T.C. resistor in the starting situation will always discharge to a slight extent through the glow discharge in the glow discharge starter. Since a balanced state is reached in which the additional charge of the capacitor, is always equal to the discharge of the capacitor the current flowing through the glow discharge starter is actually the same as the current flowing through the P.T.C. rEsistor in that situation. In a special arrangement according to the invention relating to the ignition and supply of a discharge lamp provided with preheated electrodes and a glow discharge starter which connects those ends of the two lamp electrodes which are remote from the supply together and in which the ignition voltage of the glow discharge starter is more than 90 percent of the effective value of the supply voltage and in which the glow discharge starter already closes at a power of less than 0.5 Watt, the arrangement is preferably intended for
connection to a voltage supply of approximately 220 Volts and the lamp is a low-pressure mercury vapor discharge lamp having an operating voltage of approximately 180 Volts while the ignition voltage of the glow discharge starter is more than 230 Volts. An advantage of the last-mentioned preferred arrangement is that such a known low pressure mercury vapor discharge lamp, having a length of about 2.5 meters, can be ignited and supplied in a simple manner. In a further preferred embodiment of an arrangement according to the invention the thermal capacity of the P.T.C. resistor is so small that when the arrangement is switched on, but after the lamp is extinguished, within 5 seconds after said extinguishment the temperature of the resistor will have decreased so far that the resistive value of said resistor is at most twice the resistance of the shunting lamp branch in the ignited condition of the lamp. An advantage of this prefered embodiment becomes manifest when considering the case where the operating lamp is switched off and is immediately thereafter switched on again. In that case the temperature of the P.T.C. resistor still has a high value so that this resistor is in the so-called high resistive range. When it is ensured that in this situation with the lamp extinguished this resistor has decreased so rapidly in temperature, i.e., within 5 seconds, to a resistive value which is suitable to start the lamp again, an arrangement is obtained which causes the lamp to ignite rapidly after the arrangement has been switched on again. An arrangement according to the invention may be used, for example, for igniting and supplying one discharge lamp. However, it is alternatively possible to ignite and supply a plurality of series-arranged discharge lamps with the aid of an arrangement according to the invention. In a special embodiment of an arrangement according to the invention intended for the ignition and supply of a plurality of series-arranged discharge lamps which are provided with preheated electrodes, each lamp is shunted by a glow discharge starter whose ignition voltage is larger than 0.9.(1/n) times the supply voltage, where n represents the number of series-arranged lamps. An advantage of the last-mentioned embodiment is that when the sum of the ignition voltages of a plurality of discharge lamps closely approximates or exceeds the value of the supply voltage, a simple ignition with the aid of glow discharge starters also is possible. For obtaining a relatively high ignition voltage of the glow discharge starter the electrodes of this starter may consist of, for example, a material having a high work function. In an arrangement according to the invention a glow discharge starter is preferably used whose filler gas mainly consists of hydrogen. An advantage of this starter is that the electrodes need not be

Description

United States Patent 1 Moerkens June 19, 1973 ARRANGEMENT FOR THE IGNITION AND ALTERNATING CURRENT SUPPLY FOR A GAS-AND/OR VAPOR DISCHARGE LAMP [75] Inventor: Jozef Cornelis Moerkens, Emmasingel, Eindhoven,

Netherlands [73] Assignee: U'.S. Philips Corporation, New York,

[22] Filed: Nov. 15, 1971 [21] Appl. No.: 198,838

[30] Foreign Application Priority Data Nov. 21, 1970 Netherlands 7017064 [52] US. Cl. 315/200, 315/201, 315/273,

' 3l5/DIG. 5 [51] Int. Cl. I'IOSb 41/00 [58] Field of Search 3315/1316. 5, 200,

[56] References Cited UNITED STATES PATENTS 3,328,721 6/1967 I-Ienenkamp et al.... 3l5/DIG. 5 UX Primary Examiner-Roy Lake Assistant Examiner1ames B. Mullins Attorney-Frank R. Trifari [57] ABSTRACT The invention relates to an arrangement for igniting and supplying a discharge lamp, particularly along lowpressure mercury vapor discharge lamp of about 2.5 meter. Said lamp has a relatively high ignition voltage so that it can not be ignited with the aid of a normal glow discharge starter.

According to the invention a circuit is used in which with the aid of a diode branch a voltage doubling is effected at which the lamp can be ignited. In addition this circuit includes a resistor having a positive' temperature characteristic which, after ignition of the lamp, renders the diode branch inoperative. By using the voltage doubling, a glow discharge starter can be used which must, however, be proportioned for a voltage which is generally higher than the conventional voltage.

11 Claims, 3 Drawing Figures Patented June 1 9, 1973 2 Sheets-Sheet 1 Fig.2

lNvlaNt'ok.

JOZEF C.MOERKENS AGENT Patented June 19, 1973 3,740,609

2 Sheets-Sheet 2 R (PIC) 4000 v 0 l 2000 r AGENT ARRANGEMENT FOR THE IGNITION AND ALTERNATING CURRENT SUPPLY FOR A GAS-AND/OR VAPOR DISCHARGE LAMP The invention relates to an arrangement for the ignition and alternating current supply of at least one gas and/or vapor discharge lamp which includes two electrodes. An arrangement of this kind is generally provided with a stabilizing capacitor which, in the operating condition, is connected in series with the lamp, a series arrangement of a diode and a resistor being provided which in that condition is shunted by a branch including the lamp and is connected in series with the capacitor.

A known arrangement of the kind mentioned above is described, for example, in US. Pat. No. 2,134,439. A drawback of this known arrangement is that once the value of the resistor arranged in series with the diode is adjusted, the so-called dark period of the lamp is rather long (at a low resistive value of the resistor), or the lamp starts with difficulty (at a high resistive value of this resistor). A long dark period means that the lamp does not emit light during a fairly large fraction of a period of the alternating supply voltage. This is detrimental as regards the luminous value of such a lamp, hence for considerations of efficiency. A difficult or very slow starting discharge lamp is likewise a drawback.

An object of the present invention is to obviate or at least to mitigate the mentioned drawbacks.

According to the invention an arrangement for the ignition and alternating current supply of at least one gas a'nd/or vapor discharge lamp which includes two electrodes comprises a stabilizing capacitor which in the operating condition is connected in series with the lamp and in which a series arrangement of a diode and a resistor is present which in that condition is shunted by a branch including the lamp and which is connected in series with the capacitor. The invention is characterized in that the resistor is of the type having a positive temperature characteristic which in case of the arrangement being switched on, but the lamp not yet being ignited, has a resistive value which is at most twice the resistance of the shunting lamp branch in the ignited condition of the lamp, and in which in the situation of the lamp being ignited the resistive value of the resistor having a positive temperature characteristic is at least twenty times the resistance of the shunting lamp branch.

An advantage of this arrangement is that during the starting operation the resistor having a positive temperature characteristic (P.T.C. resistor) has a relatively low resistive value. As a result the capacitor is charged quickly. This is effected through the diode. A voltage doubling across the lamp electrodes, thus occurring in a next half period of the supply voltage, may then lead to a quick ignition of this lamp. When, however, the lamp is ignited the P.T.C. resistor will exhibit a relatively high resistance value. Consequently, with the lamp ignited, the current flowing through the diode branch is then very low relative to the lamp current. As a result, the situation in the operating condition of the lamp is not much different from that of an ordinary capacitively stabilized lamp circuit. This means that the dark period of the lamp is relatively short and that substantially no direct current components in the operating condition are present in the lamp current. It is feasible that the lamp is not only stabilized through a stabilizing capacitor but through a combination of a capacitor and a coil. This coil might be located, for example, between the capacitor and a supply terminal. It is also feasible that this coil is present in series with the lamp, namely in the so-called shunting lamp branch which is connected in parallel with the series arrangement of the diode and the P.T.C. resistor.

One solution to bring the P.T.C. resistor to a highly resistive condition when the lamp is ignited is to utilize the fact that upon the ignition of the lamp the current flowing through the diode branch and hence the current flowing through the P.T.C. resistor is slightly increased. This leads to an extra heating of this resistor so that it achieves a relatively high resistive value.

Furthermore it is feasible to realize the high resistive value of the P.T.C. resistor in the operating condition of the lamp is realized by bringing this resistor into close heat contact with the lamp. It can be achieved that in the operating condition the hot lamp heats the P.T.C. resistor in such a manner that it is in the high resistive condition.

The gas and/or vapor discharge lamp is, for example, a lamp which is not provided with preheated electrodes. It is, for example, a high-pressure discharge lamp.

An arrangement according to the invention preferably serves for igniting and supplying a lamp whose two electrodes are of the preheated type and that those ends of the two lamp electrodes which are remote from the supply are connected together through a glow discharge starter, the ignition voltage of the glow discharge starter being greater than percent of the effective value of the supply voltage.

An advantage of this preferred embodiment is that special discharge lamps such as, for example, lowpressure mercury vapor discharge lamps of a type having a relatively high ignition voltage, can be ignited by means of a glow discharge starter. As a rule other provisions, for example, transformers or electronic starters are required for the ignition of this kind of lamp.

In a given embodiment of the above-mentioned preferred arrangement the glow discharge starter is proportioned in such a manner that its contact (formed by two electrodes) already close at a power of less than 0.5 Watt.

An advantage thereof is that in the situation when the arrangement is switched on but when the lamp is not yet ignited the current flowing through the glow discharge starter and hence the current flowing through the P.T.C. resistor can be maintained low. This has the advantage that the P.T.C. resistor can readily be maintained in its relatively low resistive condition. The following may serve to explain this. In a situation in which a lamp, having preheated electrodes, and a glow discharge starter are used the capacitor charged through the diode and theP.T.C. resistor in the starting situation will always discharge to a slight extent through the glow discharge in the glow discharge starter. Since abalanced state is reached in which the additional charge of the capacitor, is always equal to the discharge of the capacitor the current flowing through the glow discharge starter is actually the same as the current flowing through the P.T.C. resistor in that situation.

In a special arrangement according to the invention relating to the ignition and supply of a discharge lamp provided with preheated electrodes and a glow discharge starter which connects those ends of the two 3 lamp electrodes which are remote from the supply together and in which the ignition voltage of the glow discharge starter is more than 90 percent of the effective value of the supply voltage and in which the glow discharge starter already closes at a power of less than 0.5 Watt, the arrangement is preferably intended for connection to a voltage supply of approximately 220 Volts and the lamp is a low-pressure mercury vapor discharge lamp having an operating voltage of approximately 180 Volts while the ignition voltage of the glow discharge starter is more than 230 Volts.

An advantage of the last-mentioned preferred arrangement is that such a known low pressure mercury vapor discharge lamp, having a length of about 2.5 meters, can be ignited and supplied in a simple manner.

In a further preferred embodiment of an arrangement according to the invention the thermal capacity of the P.T.C. resistor is so small that when the arrangement is switched on, but after the lamp is extinguished, within 5 seconds after said extinguishment the temperature of the resistor will have decreased so far that the resistive value of said resistor is at most twice the resistance of the shunting lamp branch in the ignited condition of the lamp.

An advantage of this prefered embodiment becomes manifest when considering the case where the operating lamp is switched off and is immediately thereafter switched on again. In that case the temperature of the P.T.C. resistor still has a high value so that this resistor is in the so-called high resistive range. When it is ensured that in this situation with the lamp extinguished this resistor has decreased so rapidly in temperature, i.e., within 5 seconds, to a resistive value which is suitable to start the lamp again, an arrangement is obtained which causes'the lamp to ignite rapidly after the arrangement has been switched on again.

An arrangement according to the invention may be used, for example, for igniting and supplying one discharge lamp. However, it is alternatively possible to ignite and supply a plurality of series-arranged discharge lamps with the aid of an'arrangement according to the invention.

In a special embodiment of an arrangement according to the invention intended for the ignition and supply of a plurality of series-arranged discharge lamps which are provided with preheated electrodes, each lamp is shunted by a glow discharge starter whose ignition voltage is larger than O.9'(l/n) times the supply voltage, where n represents the number of series-arranged lamps.

An advantage of the last-mentioned embodiment is that when the sum of the ignition voltages of a plurality of discharge lamps closely approximates or exceeds the value of the supply voltage, a simple ignition with the aid of glow-discharge starters also is possible.

For obtaining a relatively high ignition voltage of the glow discharge starter the electrodes of this starter may consist of, for example, a material having a high work function.

In an arrangement according to the invention a glow discharge starter is preferably used whose filler gas mainly consistsof hydrogen.

An advantage of this starter is that the electrodes need not be modified, but the high ignition voltage is simply realized by admitting for this purpose the said filler gas or a gas mixture mainly containing hydrogen gas.

For obtaining a very high ignition voltage it is of course feasibleto use a combination of electrode material having a high work function and a gas mainly comprising hydrogen gas.

In order that the invention may be readily carried into effect, some embodiments thereof will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawings in which:

FIG. 1 shows a circuit diagram of an arrangement according to the invention and a lamp to be supplied from this arrangement;

FIG. 2 shows a circuit diagram of a second arrangement according to the invention and two lamps to be supplied from this arrangement;

FIG. 3 shows a graph in which the resistance R is plotted as a function of the temperature I of a P.T.C. resistor 'used in the arrangement of FIG. 1.

In FIG. 1 the referencenumerals 1 and 2 denote connecting terminals which are intended to be connected to an alternating current supply of approximately 220 Volts, 50 Hz. The terminal 1 is connected toa stabilizing coil 3. The other side of the coil 3 is connected to a capacitor 4. The capacitor 4 is connected to a series arrangement of a diode 5 and a resistor 6 having a positive temperature characteristic (P.T.C. resistor). The other side of the resistor 6 is connected to the connecting terminal 2 of the arrangement. The series arrangement of the diode 5 and the P.T.C. resistor is shunted by a low-pressure mercury vapor discharge lamp 7. The lamp 7 is provided with preheated electrodes 8 and 9. The ends of the electrodes 8 and 9 remote from the ter-' minals l and 2 are connected together through a glow discharge starter 10. The glow discharge starter is provided with two bimetal electrodes 11 and 12. Upon heating of the electrodes of the glow discharge starter by the glow discharge in the starter, these electrodes 1 1 and 12 bend towards each other. This starter is mainly filled with hydrogen percent with an addition of neon gas (30 percent). Thedischarge lamp 7 is a lowpressure mercury vapor discharge lamp rated at Watts. It has a length of about 2.5 meters.

The arrangement of FIG. 1 operates as follows. When the terminals 1 and 2 are connected to the said alternating current source of 220 Volts, 50 Hz, capacitor 4 is first charged through the diode 5 and the P.T.C. resistor 6. In the next half period of the supply voltage a double mains voltage is applied across the electrodes 8 and 9 of the lamp 7. The glow discharge in the glow discharge starter 10 ignites at this voltage. When this glow discharge has been maintained for some time, the bimetal electrodes 1 1 and 12 are heated in such a manner that they contact each other. Then a preheating current flows through the electrodes 8 and 9. Since the electrodes l1 and 12 now contact each other, further heat is not developed in the glow discharge starter 10. As a result this starter cools so that the contacts 11 and 12 move away from each other. At the instant of moving away a voltage pulse is produced in the coil 3 which cooperates in realizing high peak voltages between the electrodes 8 and 9 of the lamp 7. If the first separation of the contacts 11 and 12 moving away does not lead to an ignition of the lamp 7, a second starting attempt will now take place so that a glow discharge is produced again between the electrodes 11 and 12 of the glow discharge starter. The heat produced thereby again leads to closure of the bimetal contacts, etc. Due to the proportioning of P.T.C. resistor 6 it has been ensured that this resistor remains in its so-called lowresistive condition during the ignition period. This means that its resistive value is not more than twice that of the lamp 7. When the starting attempts have led to ignition of the lamp 7, the voltage between the electrodes 8 and 9 of lamp 7 decreases to the lamp operating voltage, which is lower than the ignition voltage of the glow discharge starter 10. The glow discharge starter then remains inoperative. In this case it is ensured that the current flowing through the P.T.C. resistor is so high that it comes into the so-called high resistive range. In this case the

branch

5, 6 has a negligible influence on the further course of the current. The lamp 7 then actually burns in series with the two ballasts 3 and 4. This situation hardly deviates from that of operating a normally capacitively stabilized discharge lamp. In a practical embodiment the lamp 7 was a low-pressure mercury vapor discharge lamp which required a peak ignition voltage of approximately 1,000 to 1,100 Volts for ignition; the operating voltage of this lamp was approximately 180 Volts and the lamp current was approximately 550 mAmps. The inductance of the coil 2 was approximately 1 Henry and the capacitance of the capacitor 4 was approximately 4.6 p.F. The P.T.C. resistor had a value of approximately 500 Ohm in the cold state, while in the situation with the lamp 7 ignited the P.T.C..had a resistance which was greater than 10,000 Ohms. See also FIG. 3. The glow discharge starter 10 was proportioned in such a manner that closure of its electrode contact occurred with certainty at a terminal voltage of more than 380 Volts, while closure of the contact took place between 250 and 380 Volts. The starter would always open for terminal voltages lower than 250 Volts. The current flowing through P.T.C. resistor 6 prior to ignition of the lamp 7 was approximately 8 mAmps and after ignition of the lamp 7 it was approximately 13 mAmps.

The thermal capacity of P.T.C. resistor 6 was chosen in such a manner that when the arrangement was switched off and immediately switched on again the resistor 6 achieved a resistance of approximately 500 Ohms after approximately 4 seconds. Thus this is the resistance in the so-called low resistive situation. Consequently a case was obtained which is comparable with that initially present prior to starting the lamp 7. Thus the lamp 7 was quickly ignited.

The position of the P.T.C. resistor in the installation is chosen in such a manner that with the lamp 7 ignited no heat is derived by a stream of air or a thermal conductor. It is feasible to arrange the P.T.C. resistor 6 together with the glow discharge starter 10 in one envelope.

If desired, the

series arrangement

5, 6 may be connected directly in parallel with the glow discharge starter l0, i.e., on the sides of the lamp electrodes 8 and 9 remote from the input terminals (1,2).

During the start the glow discharge starter required less than 0.5 Watt for theembodiment described.

The above-mentioned data show that the condition is satisfied that during the start the resistance of P.T.C. resistor 6 500 Ohm had a value which was less than twice the lamp resistance approximately 2 X (l80/0.55) 2 X 330) 660 Ohms. Furthermore it was found that during the operating condition the resistance of P.T.C. resistor 6 10,000 Ohms was more than twenty times the lamp resistance X 330) 6,600 Ohms. The ignition voltage of the glow discharge starter was larger than 250 Volts, thus more than percent of 220 Volts.

In FIG. 2 the

reference numerals

20 and 21 denote connecting terminals which are intended to be connected to an alternating voltage supply of, for example, 220 Volts, 50 Hz. Terminal 20 is connected to a coil 22 which in turn is connected to a stabilizing capacitor 23. Capacitor 23 is connected in a corresponding manner as in FIG. 1 to a series arrangement of a diode 24 and a P.T.C. resistor 25. Resistor 25 is of the same type as resistor 6 of FIG. 1. The other side of P.T.C resistor 25 is connected to the supply terminal 21. The series arrangement of diode 24 and P.T.C. resistor 25 is shunted by a series arrangement of two low-pressure mercury

vapor discharge lamps

26 and 27. These two lamps are each provided with two preheated electrodes which are denoted by

reference numerals

28, 29 and 30, 31, respectively. The sides of the

electrodes

28 and 29 remote from the

supply terminals

20 and 21 of the lamp 26 are connected together via a glow discharge starter 32. The ends of the

preheated electrodes

30 and 31 of the lamp 27 remote from the

supply terminals

20 and 21 are connected together through a glow discharge starter 33.

Lamps

26 and 27 are low-pressure mercury vapor discharge lamps of approximately 40 Watts each. The operating voltage of each of these lamps was approximately Volts. The

glow discharge starters

32 and 33 were practically the same. They contain a filler gas of neon and ignited in a voltage range of to Volts. Thus, these glow discharge starters ignited at more than 0.9-( l/n) X 220 Volt which at n 2 is equal to approximately 100 Volt. The inductor 22 had a value of approximately 1.2 Henry and the capacitor 23 had a capacitance of approximately 3.7 p.1 In the situation with the lamps not yet ignited, but the power switched on, the resistor 25 had a value of approximately 500 Ohms, but this resistance rose to approximately 10,000 Ohms when the

lamps

26 and 27 were ignited. The arrangement of FIG. 2 operates in approximately the same manner as that of FIG. 1, namely when a voltage is applied to

terminals

20 and 21 capacitor 23 will first be charged to a slight extent through the diode 24 and the resistor 25. During the next half period an approximately two-fold supply voltage will be present between the

electrodes

28 and 31. The two seriesarranged

glow discharge starters

32 and 33 then ignite. As a result a preheating current will flow through the electrodes 28 to 31. When the contact of at least one of the

glow discharge starters

32 and 33 opens, a voltage pulse is produced in the coil 22 which is applied across the lamp electrodes. When this has been repeated one or more times, the

lamps

26 and 27 will ignite, as a rule, one just after the other. Subsequently a larger current will flow through the P.T.C. resistor 25 which current brings this resistor to its highly resistive state. In that case the current flowing through the

circuit

24, 25 will again drop to a value which is negligibly low relative to the lamp current flowing through the

lamps

26 and 27.

When proportioning the P.T.C. resistors it will have to be taken into account whether the arrangement is used in a fitting and whether this fitting is open or closed. This is of importance for the temperature to be obtained, hence the resistivity, of the P.T.C. resistor in the operating condition, i.e., in the situation when the lamps operate.

The current intensity through the P.T.C. resistor 25 for igniting the

lamps

26 and 27 and the current intensity through the FTC. resistor 25 and that through the lamp branch after ignition of the

lamps

26 and 27 was approximately equal to that in. the corresponding branches of FIG. 1 so that in the case of FIG. 2 the condition imposed on the resistive ratio also is satisfied.

As is evident from the embodiments of FIGS. 1 and 2 it is possible to ignite a lamp having a relatively high ignition voltage or to ignite series arrangements of lamps which together have a relatively high ignition voltage with a glow discharge starter in a simple manner. This is because a voltage increase is used with the aid of a diode in which the diode branch is rendered substantially inoperative after ignition of the lamp (lamps).

What is claimed is:

l. A circuit for supplying an alternating current to at least one discharge lamp which includes two electrodes comprising, a pair of input terminals adapted for connection to a source of AC supply current, a stabilizing capacitor which in the operating condition of the lamp is connected in series therewith across the input terminals, a series arrangement of a diode and a resistor of the type havinga positive temperature characteristic, means connecting said series arrangement in shunt with a branch circuit including the lamp and in series with the capacitor, characterized in that the PTC resistor exhibits a resistance value with the power applied to said input terminals but the lamp not yet ignited which is at most twice the operating resistance of the shunting lamp branch, and wherein with the lamp ignited the resistive value of the PTC resistor is at least 20 times the operating resistance of the shunting lamp branch.

2. A circuit as claimed in claim 1 wherein the lamp electrodes are of the preheated type, means connecting those ends of the two lamp electrodes which are remote from the input terminalsto a glow discharge starter, the ignition voltage of the glow discharge starter being at least 90 percent of the effective value of the AC supply voltage.

3. A circuit as claimed in claim 2, wherein the glow discharge starter includes a contact which is adapted to close at a power of less than 0.5 Watt.

4. A circuit as claimed in claim 2 and adapted for connection to a supply voltage of approximately 220 Volts and wherein said discharge lamp comprises a low-pressure mercury vapor discharge lamp having an operating voltage of approximately 180 Volts, and characterized in that the ignition voltage of the glow discharge starter is at least 230 Volts.

5. A circuit as claimed in claim 1, characterized in that the thermal capacity of the P.T.C resistor is so small that with the circuit switched on, but after the lamp has been extinguished, the temperature of said resistor will have decreased within 5 seconds after said extinguishment such that the resistive value of said resistor is at most twice the operating resistance of the shunting lamp branch.

6. A circuit as claimed in claim 1 wherein the lamp electrodes are of the preheated type, said circuit further comprising at least one other discharge lamp provided with preheated electrodes and connected in series with the first lamp across the input terminals, characterized in that each lamp is shunted by a glow discharge starter whose ignition voltage is at least 0.9/n times the supply voltage, where n represents the number of series-arranged lamps.

7. A circuit as claimed in claim 2, characterized in that the filler gas of the glow discharge starter is composed mainly of hydrogen.

8. An electric supply circuit for a discharge lamp comprising, a pair of input terminals adapted to be connected to a source of AC supply voltage, a capacitor, means connecting the capacitor in series with the lamp across said input terminals, a rectifier element, a resistor having a positive temperature characteristic, means connecting the rectifier element in series with the PTC resistor across the lamp electrodes and in series with the capacitor across the input terminals, said PTC resistor having a resistance value before ignition of the lamp which is at most twice the operating resistance of said lamp and with the lamp ignited said resistance value is at least twenty times the lamp operating resistance.

9. A circuit as claimed in claim 8 further comprising an inductor connected in series with said capacitor to said input terminals.

10. A circuit as claimed in claim 8 wherein the lamp electrodes are of the preheated type, said circuit further comprising at least one other discharge lamp with preheated electrodes and connected in series with the first lamp and capacitor across the input terminals, and circuit means providing a path for the flow of heating current through said lamp electrodes prior to lamp ignition.

11. A circuit as claimed in claim 10 wherein said circuit means includes a glow discharge starter in shunt with each lamp, each starter having an ignition voltage which is at least 0.9/n times the supply voltage, where n represents the number of series arranged lamps.

'g gg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 740, 609 Dated June 19, 1973 Inventor-( JOZEF CORNELIS MOERKENS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown'below:

col. 1, line40, after "in' insert the col. 2, line 17, cancel is realized col. 4, line 14, after the semicolon (7) insert and col. 5, line 20, cancel the" and, insert The col. 7, line l0, before "or" insert a coma 7 col. 7-, line 12, before "with" insert a comma col. 7, line 13, cancel "used" and insert' obtained Signed and sealed this 2nd day of April 197 4.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. G. MARSHALL DANN Attesting Officer I Commissioner of Patents

Claims

1. A circuit for supplying an alternating current to at least one discharge lamp which includes two electrodes comprising, a pair of input terminals adapted for connection to a source of AC supply current, a stabilizing capacitor which in the operating condition of the lamp is connected in series therewith across the input terminals, a series arrangement of a diode and a reSistor of the type having a positive temperature characteristic, means connecting said series arrangement in shunt with a branch circuit including the lamp and in series with the capacitor, characterized in that the PTC resistor exhibits a resistance value with the power applied to said input terminals but the lamp not yet ignited which is at most twice the operating resistance of the shunting lamp branch, and wherein with the lamp ignited the resistive value of the PTC resistor is at least 20 times the operating resistance of the shunting lamp branch.

2. A circuit as claimed in claim 1 wherein the lamp electrodes are of the preheated type, means connecting those ends of the two lamp electrodes which are remote from the input terminals to a glow discharge starter, the ignition voltage of the glow discharge starter being at least 90 percent of the effective value of the AC supply voltage.