Title:
ARRANGEMENT FOR IGNITING AND SUPPLYING A GAS-AND/OR VAPOUR DISCHARGE LAMP
United States Patent 3836816


Abstract:
A supply circuit for a discharge lamp includes a glow starter tube and a photosensitive resistor in parallel across the preheated electrodes of the discharge lamp. The photo-resistor is exposed to the light from the starter tube whereby its impedance drops sharply to increase the heating current of the lamp electrodes and thereby reduce the electrode warm up time. An inductor in series with the discharge lamp combines with the subsequent opening of the starter tube electrodes to generate a voltage ignition pulse for the discharge lamp.



Inventors:
HECK C
Application Number:
05/311442
Publication Date:
09/17/1974
Filing Date:
12/01/1972
Assignee:
PHILIPS CORP,US
Primary Class:
Other Classes:
315/101, 315/DIG.5
International Classes:
H01J61/54; H05B41/04; (IPC1-7): H05B39/00; H05B41/08
Field of Search:
315/DIG.5,100,94,99C,101,156,158,234,261,283
View Patent Images:



Primary Examiner:
Kaufman, Nathan
Attorney, Agent or Firm:
Trifari, Frank Franzblau Bernard R.
Claims:
What is claimed is

1. A supply circuit for an electric discharge lamp having at least two preheated electrodes comprisng, a pair of input terminals adapted for connection to a source of electric current, an inductor, means connecting said inductor in series with the lamp across said input terminals, a glow discharge starter, means connecting said glow discharge starter across the lamp electrodes, a photosensitive element having a negative coefficient of resistance and located to receive at least a part of the light emitted by the glow discharge starter, the illumination received by said photosensitive element from the glow discharge starter being greater than all of the illumination received from other light sources including said discharge lamp, and means connecting an auxiliary branch circuit including said photosensitive element in shunt with the glow discharge starter.

2. A supply circuit as claimed in claim 1 wherein said input terminals are adapted for connection to a source of AC current, said circuit further comprising a capacitor connected in series with the lamp and inductor across the input terminals and a rectifier element included in said auxiliary branch circuit.

3. A supply circuit as claimed in claim 2 wherein said rectifier element is connected in series with said photosensitive element across the glow discharge starter, said circuit further comprising, a resistor, means connecting said resistor between the junction of said rectifier element and one end of said photosensitive element and a second junction between the other end of the photosensitive element and the glow discharge starter.

4. A supply circuit as claimed in claim 3 further comprising a second resistor connected in series with the photosensitive element and between the two junctions.

5. A supply circuit as claimed in claim 1 wherein said inductor comprises a first winding of a transformer, said transformer including a second winding connected in series with the glow discharge starter across the lamp electrodes.

6. A supply circuit as claimed in claim 1 wherein the input terminals are adapted for connection to an AC source of approximately 220 volts and the lamp comprises a low-pressure mercury vapor discharge lamp having an operating voltage of approximately 180 volts, and wherein the ignition voltage of the glow discharge starter is at least 230 volts effective.

7. A supply circuit as claimed in claim 1 wherein said glow discharge starter and said photosensitive element are mounted within a common light-tight envelope.

8. A supply circuit as claimed in claim 7 further comprising a rectifier element connected in series with said photosensitive element across the glow discharge starter.

9. A supply circuit as claimed in claim 1 further comprising a rectifier element connected in series with said photosensitive element across the glow discharge starter.

10. A supply circuit for an electric discharge lamp having at least two preheated electrodes comprising, a pair of input terminals adapted for connection to a source of electric current, an inductor, a glow discharge starter, means connecting said inductor, said two electrodes and said glow discharge starter in series circuit across said input terminals so that a heater current for the lamp electrodes flows through the glow discharge starter, a photosensitive element whose impedance varies with the light incident thereon and located to receive the light emitted by the glow discharge starter to vary its impedance therewith, and means connecting said photosensitive element in shunt with the glow discharge starter to provide a second path for the flow of heater current through the discharge lamp electrodes, said photosensitive element being arranged so that its impedance is substantially independent of the light emitted by the discharge lamp.

11. A supply circuit as claimed in claim 10 wherein the input terminals are adapted for connection to a source of AC voltage and wherein the ignition voltage of the glow discharge starter is higher than the operating voltage of the discharge lamp.

12. A supply circuit as claimed in claim 10 further comprising a vapacitor connected in series with the inductor, the two lamp electrodes and the glow discharge starter across the input terminals, and a rectifier element connected in series with the photosensitive element across the glow discharge starter whereby the capacitor-rectifier combination cooperate to provide a voltage multiplier effect across the electrodes of the glow discharge starter.

13. A supply circuit as claimed in claim 12 further comprising an impedance element connected in shunt with the photosensitive element and in series with the rectifier element across the input terminals.

Description:
The invention relates to an arrangement for igniting and supplying a gas and/or vapour discharge lamp provided with at least two preheated electrodes in which two input terminals of the arrangement are connected through a series arrangement of the discharge lamp and at least an inductor, one lamp electrode being electrically connected through a glow discharge starter to the other electrode. The invention also relates to an auxiliary starter, particularly suitable for an arrangement of this kind.

A known arrangement of the above-mentioned kind is described, for example, in the book "Fluorescent lamps and lighting" by Elenbaas, Philips Technical Library 1959 page 122.

A drawback of the known arrangement is the sometimes relatively long period elapsing until the instant when the lamp electrodes have achieved a sufficiently high temperature to be able to ignite the lamp at a voltage peak occurring between these electrodes when the contacts of the glow discharge starter open.

An object of the invention is to provide a quick heating of the lamp electrodes and thereby a quick ignition of the lamp.

According to the invention an arrangement for igniting and supplying a gas- and/or vapour discharge lamp provided with at least two pre-heated electrodes in which two input terminals of the arrangement are connected through a series arrangement of the discharge lamp and at least an inductor, and in which one lamp electrode is electrically connected through a glow discharge starter to the other lamp electrode, is characterized in that the glow discharge starter is shunted by an auxiliary branch which includes a photosensitive circuit element having a negative resistance coefficient onto which at least part of the light from the glow discharge of the glow discharge starter is incident, the photosensitive circuit element being arranged in such a manner that the glow discharge starter supplies the photosensitive circuit element with an illumination which is larger than the illumination supplied to the photosensitive circuit element by the gas- and/or vapour discharge lamp combined with other light sources, if any.

In this respect a photosensitive circuit element having a negative coefficient is understood to mean a circuit element whose impedance decreases when light is incident on it. Examples of such circuit elements are, for example, photosensitive resistors, photosensitive diodes and photosensitive semiconductor switching elements such as, for example, photosensitive transistors.

An advantage of an arrangement according to the invention is that a glow discharge is produced in the glow discharge starter after the input terminals have been connected to a suitable supply source and that part of the light from this glow discharge is incident on the photosensitive circuit element so that this element is brought from a state having a relatively high impedance (for example, high-resistive state) to a state having a relatively low impedance (for example, low-resistive). Since the photosensitive circuit element is connected in parallel with the glow discharge starter, the total current through these parallel circuits will increase and hence increase the pre-heating current of the lamp electrodes. As a result the desired effect is achieved. When the glow discharge starter contacts have contacted each other due to the thermal development in this starter and the bimetal character of the glow discharge starter electrodes, the glow discharge will be extinguished and the photosensitive circuit element, for example, a photosensitive resistor or light dependent resistor (LDR) will resume its high impedance. When, some time afterwards, these electrodes move away from each other again in known manner by cooling of the glow discharge starter electrodes, the abrupt current reduction thereby produced, combined with the inductance in series with the discharge lamp, will realize a voltage peak between the lamp electrodes whereupon the lamp can ignite. When the lamp does not ignite for the first time, a glow discharge is again produced in the starter, etc., so that then a new starting attempt is automatically made. The presence of the photosensitive circuit element influences the abrupt current reduction to a small extent because this circuit element has had the possibility during the period immediately preceding - in the closed state of the glow discharge starter contact - to become slightly higher resistive again. After ignition of the lamp the voltage across the glow discharge starter decreases to the operative voltage of the lamp and the glow discharge starter thereby remains extinguished and the photosensitive circuit element, for example, the LDR remains highly resistive.

Screening of the LDR from the light of the ignited discharge lamp is effected, for example, by placing an opaque screen between the lamp and this LDR. A further possibility is to build the glow discharge starter together with the LDR in a closed part of the luminaire in which the said discharge lamp is used, or, for example, by arranging the LDR at a very large distance from the discharge lamp.

It is to be noted that it is known per se to incorporate a photosensitive element in a shunt across a branch including a discharge lamp having preheated electrodes. In this connection reference is made to U.S. Pat. No. 3,209,202. In this known case the photosensitive element does not, however, receive light from a glow discharge starter but receives much light from the discharge lamp.

In an arrangement according to the invention, intended for connection to an alternating voltage supply, the series arrangement including the lamp preferably comprises a capacitor between the input terminals and the auxiliary branch including the photosensitive circuit element incorporates a rectifier element.

An advantage of this preferred embodiment is that the capacitor-rectifier element combination may be used as a voltage doubler so that also the glow discharge starters required for discharge lamps having a relatively high operating voltage can realize a fast ignition.

In the case of the said preferred embodiment it is desired that the impedance of the photosensitive circuit element, when no light is incident on it, is not too large because otherwise the charge of the capacitor and hence the build-up of the double voltage would take a rather long period.

In a further improvement of the last-mentioned preferred embodiment a first junction between the rectifier element and one end of the photosensitive circuit element is connected through a further resistor to a second junction between the other end of the photosensitive circuit element and the glow discharge starter,

An advantage of this preferred embodiment is that the photosensitive circuit element, for example, the LDR, may have a very high resistive value when no light is incident on it because the capacitor current can than initially flow through this additional resistor.

In a further preferred embodiment a resistor in series with the photosensitive circuit element is present between the two junctions.

In that case the circuit of the arrangement may be simply proportioned in such a manner that the branch including the photosensitive circuit element, for example, an LDR, in case of an ignited glow discharge starter does not become so low resistive that the glow discharge in the glow discharge starter is immediately extinghuished again. The necessity of, for example, a grey filter between the glow discharge starter and the LDR is prevented by this preferred method.

In a further preferred embodiment of an arrangement according to the invention the inductor in the series arrangement connecting the input terminals and comprising the lamp has a winding of a transformer, the other winding of which is incorporated in the connection connecting the lamp electrodes and comprising the glow discharge starter.

An advantage of this embodiment is that a large preheating current for the lamp electrodes becomes possible.

In a special arrangement according to the invention intended for connection to an AC supply of approximately 220 Volt alternating voltage, in which the lamp is a low-pressure mercury vapour discharge lamp having an operating voltage of approximately 180 volts, the ignition voltage of the glow discharge starter is larger than 230 Volt effective. An advantage of this arrangement is that also, for example, the so-called 8 foot low-pressure mercury vapour discharge lamp can be ignited and supplied.

An auxiliary starter suitable for an arrangement according to the invention preferably includes a combination of a glow discharge starter and a photosensitive circuit element which are jointly surrounded by a substantially light-tight jacket. The photo-sensitive circuit element is then preferably included in series with a rectifier element in a circuit shunting the glow discharge tube of the glow discharge starter. An advantage thereof is the compact structure which may be substantially as small as that of the conventional glow discharge starter having a jacket but without a photosensitive circuit element.

The invention will be further described with reference to the accompanying drawing in which:

FIG. 1 shows an electrical circuit diagram of an arrangement according to the invention; and

FIG. 2 shows an auxiliary, starter according to the invention.

In FIG. 1, the reference numerals 1 and 2 are input terminals which are intended for connection to an alternating voltage supply of 220 Volts, 50 Herz. The reference numeral 3 denotes a low-pressure mercury vapour discharge lamp of approximately 85 Watts having a length of approximately 2.5 metres (approximately 8 feet) and an operating voltage of approximately 180 Volts. The lamp 3 has two pre-heated electrodes 4 and 5. The input terminal 1 is connected through a capacitor 6 and a winding 7 of a transformer 8 to one end of the lamp electrode 4. The other end of the lamp electrode 4 is connected through a further winding 9 of the transformer 8 to an auxiliary starter 10. The auxiliary starter includes a glow discharge starter 11 which is shunted by a capacitor 12 having a relatively low capacitance. The glow discharge starter 11 is furthermore shunted by a series arrangement of a diode 13, a fixed resistor 14 and a photosensitive resistor having a negative coefficient (LDR) 15. Furthermore an additional resistor 16 is connected in parallel with the series arrangement of the resistors 14 and 15. The glow discharge starter 11 and the branches connected in parallel therewith are furthermore connected through the electrode 5 to the terminal 2.

The LDR 15 can receive light from the glow discharge starter 11 (see the arrow in FIG. 1). In a given case the circuit elements 11 to 16 are positioned within a light-tight jacket. One object thereof is to screen the LDR 15 from the light of the lamp 3 and from the light of possible further light sources. The combination of the circuit elements 11 to 16 within the jacket 17 is shown in FIG 2. The connection lugs 18 and 19 (see FIG. 2) are the connection members for the auxiliary starter.

The operation of the circuit of FIG. 1 is as follows.

When the terminals 1 and 2 are connected to the alternating voltage source of approximately 220 Volts, a current having a low value will flow mainly through the circuit 1, 6, 7, 4, 9, 13, 16, 5, 2 the half cycle in which the terminal 1 is positive relative to the terminal 2. This current of low value charges capacitor 6 to a slight extent. During the next half cycles in which the terminal 2 is positive relative to terminal 1 nothing happens initially until at a given instant the ignition voltage of the glow discharge starter 11 is reached in one of the last-mentioned half cycles due to the continued charging of capacitor 6. A glow discharge is thereupon produced in this starter. The light therefrom is incident on the LDR 15 which thereby comes into a state of lower resistivity. Subsequently the capacitor will undergo a variation of charge in the half cycles when the terminal 2 is positive relative to terminal 1 due to a current flowing through starter 11 and in the next half cycles it will undergo an opposite charge variation due to a current which flows, inter alia, through the then low resistive branch 13, 14 and 15. These currents have a considerably higher value than at the instant prior to the light being incident on the LDR because the branch 13, 14, 15 has a lower resistive value than before.

The contacts of the glow discharge starter 11 will then close. This results in a strong pre-heating current through the electrodes 4 and 5 which had already been heated to some extent due to the contribution of the previous current through the LDR. When the contacts of the glow discharge starter 11 cool off again, the abrupt current reduction thereby produced generates a voltage peak between the lamp electrodes 4, 5 whereupon the lamp is ignited, possibly after one or more repetitions of the procedure described. Subsequently the voltage between the lamp electrodes 4 - 5 decreases to the operating voltage of approximately 180 Volts whereupon the glow discharge starter no longer ignites and no further light is incident on the LDR, also due to the jacket 17 and the base plate 17a (see FIG. 2).

In one embodiment the ignition voltage of the glow discharge starter 11 was more than 230 Volts effective. This glow discharge starter 11 could not sustain a glow discharge below this value of 230 Volts. The capacitance of the capacitors 6 and 12 were approximately 5 μ Farad and approximately 8,000 pFarad, respectively. The resistors 14 and 16 had a value of approximately 1 kOhm and 15 kOhm, respectively. When no light was incident on the LDR it had a resistance which was more than 10 M Ohm and in a state in which light was incident on it - by the glow discharge starter - it had a value of approximately 5 kOhm.

In situations where voltage doubling is not necessary for the ignition of the lamp, such as the case, for example, when for the given supply voltage of 220 Volts the lamp 3 is replaced between terminals 1 and 2 by a conventional 40 Watt low-pressure mercury vapour discharge lamp, the circuit elements 9, 13 and 16 and possibly also 6 may be omitted. In that case, however, the glow discharge starter 11 will have to be exchanged for a glow discharge starter having a slightly lower ignition voltage. In the latter case - likewise as in the circuit of FIG. 1 - the pre-heating current through the lamp electrodes may be slightly larger than in the absence of the LDR, and this larger pre-heating current enhances a rapid ignition of the lamp.

The given embodiment (see FIGS. 1 and 2) uses only one LDR. If necessary, several LDRs may be used in series or in parallel, for example, on either side of the glow discharge starter 11. To increase the light intensity on the LDR a small reflector within the jacket 17 may be used, if desired.

The photosensitive circuit element, for example, an LDR may alternatively be incorporated in a holder of the auxiliary starter, that is to say, in a holder which cooperates with the connection lugs 18 and 19 (see FIG. 2). In that case there will be a hole in the centre of the base plate 17a so that light from the glow discharge starter may pass through the hole and be incident on the photosensitive circuit element, for example, the LDR, located in the holder of the auxiliary starter.