EP0049466B1 - Low energy starting aid for high intensity discharge lamps - Google Patents
Low energy starting aid for high intensity discharge lamps Download PDFInfo
- Publication number
- EP0049466B1 EP0049466B1 EP81107750A EP81107750A EP0049466B1 EP 0049466 B1 EP0049466 B1 EP 0049466B1 EP 81107750 A EP81107750 A EP 81107750A EP 81107750 A EP81107750 A EP 81107750A EP 0049466 B1 EP0049466 B1 EP 0049466B1
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- EP
- European Patent Office
- Prior art keywords
- starting
- pulse generator
- electrodes
- pulse
- spiral line
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/54—Igniting arrangements, e.g. promoting ionisation for starting
- H01J61/547—Igniting arrangements, e.g. promoting ionisation for starting using an auxiliary electrode outside the vessel
Definitions
- the invention relates to a light source, comprising a high pressure sodium discharge lamp including a discharge tube having first and second electrodes, sealed therein at opposite ends for receiving AC power and enclosing a fill material under high pressure which emits light during discharge, pulse generating means operative to provide at an output thereof a high voltage, short duration pulse of predetermined energy, and a starting aid electrode coupled to the output of said pulse generating means and disposed in close proximity to an outer.surface of said discharge tube for providing an ionization path between said electrodes when said starting aid electrode is energized by that pulse generating means.
- Such a light source- is known from US-A-4179640.
- High intensity discharge lamps such as high pressure sodium lamps, commonly include noble gases at pressures. below 133 ⁇ 10 2 Pa (100 Torr). Lamps containing noble gases at pressures below 133 ⁇ 10 2 Pa (100 Torr) can be started and operated by utilizing an igniter in conjunction with a lamp ballast.
- the lamp ballast converts the ac line voltage to the proper amplitude and impedance level for lamp operation.
- the igniter provides pulses which assist in initiating discharge.
- the igniter is a relatively large and heavy circuit and is typically built into or located near the lamp ballast.
- a high voltage pulse is typically coupled to the discharge tube by a conductor known as a starting aid, as shown in the above-mentioned U.S. Patent No. 4,179,640 issued December 18, 1979 to Larson et al.
- the starting aids shown in the prior art have had the form of a wire wrapped around the discharge tube in a spiral configuration or a wire harness surrounding the discharge tube.
- a starting aid electrode which is a conductor with a generally straight portion extending from a region proximate to one of the main electrodes towards a region proximate to the other main electrode.
- Starting aid configurations which more efficiently couple the starting pulse to the discharge lamp are desirable for several reasons.
- the physical size and cost of the starting pulse generator circuit can be reduced. Physical size of the starting circuit is of particular importance when it is desired to include the starting circuit within the outer jacket of the lamp.
- more efficient coupling of the starting pulse facilitates starting of discharge lamps having higher starting pulse energy requirements.
- the object of the invention to provide a light source of the type as mentioned above, which has a starting wire configuration so that only minimal pulse energy for the ignition of discharge is required.
- this task is solved by a light source as mentioned above, which is characterized in that said starting aid electrode is a conductor including a generally straight portion extending from a region proximate to one-of said electrodes towards a region proximate to the other of said electrodes, whereby said ionization path is generated by applying the AC voltage between the first and second electrodes and by applying at said starting aid electrode a high voltage pulse with respect to one of the first and second electrodes, said high voltage pulse being supplied by the pulse generating means.
- said conductor is supported by the outer surface of said discharge tube.
- a high intensity light source is shown in FIG. 1 and includes a high pressure discharge lamp 10, a spiral line pulse generator 12, a switch 14, and an elongated conductor 20.
- the discharge lamp 10 is a high pressure sodium lamp and includes a discharge tube 22, typically made of alumina or other transparent ceramic material, having electrodes 24 sealed therein at opposite ends.
- the discharge tube 22 encloses a fill material, typically including sodium or a sodium amalgam and a noble gas or mixtures of nobles gases, which emits light during discharge.
- the electrodes 24 receive ac power from a lamp ballast at a voltage and current suitable for operation of the discharge lamp 10.
- An output 26 of the spiral line pulse generator 12 is coupled to one end of the conductor 20, typically a fine wire, which is located in close proximity to an outer surface of the discharge tube 22.
- the configuration of the conductor 20 is of importance in efficient starting of the light source of FIG. 1 and is described in greater detail hereinafter.
- the spiral line pulse generator 12 receives electrical energy from a source of voltage V o which can be the ac input to the discharge lamp 10.
- the switch 14 is coupled to the spiral line pulse generator 12. In a manner which is fully described hereinafter, the spiral line pulse generator 12, after closure of the switch 14, provides at its output a high voltage, short duration pulse which initiates discharge in the discharge lamp 10.
- the spiral line pulse generator 12 is shown in simplified form in FIG. 2 for ease of understanding.
- a pair of conductors 30 and 32 in the form of elongated sheets of conductive material are rolled together to form a multiple turn spiral configuration.
- FIG. 3 is a partial cross sectional view of the spiral line pulse generator 12 illustrating the layered construction of the device.
- a four layered arrangement of alternating conductors and insulators, including the conductors 30 and 32 and a pair of insulators 34 and 36, is rolled onto a form 38 in a multiple turn spiral configuration.
- the form 38 provides mechanical rigidity.
- the conductors 30 and 32 are separated by dielectric material at every point in the spiral configuration.
- FIG. 2 schematically shows the conductors 30 and 32.
- the conductor 30 runs from point 40 to point 42 while the conductor 32 runs from point 44 to point 46.
- the switch 14 is coupled between the conductors 30 and 32 at or near the points 40 and 44.
- a voltage V o is applied between the conductors 30 and 32.
- a field reversing wave propagates along the transmission line formed by the conductors 30 and 32.
- the potential difference between the points 42 and 46 is nV o , where n is the number of turns in the spiral configuration, due to the absence of cancelling static field vectors.
- the output voltage waveform of the spiral line pulse generator 12 is shown in FIG. 4.
- the operation of the spiral line pulse generator is described in further detail in U.S. Patent No. 3,289,015 and in Fitch et al., Novel Principle of Transient High Voltage Generation, Proc. IEE, Vol. 111, No. 4, April 1964.
- the operation and properties of the spiral line pulse generator 12 can be expressed in terms of the following parameters:
- the capacitance of the spiral line and its effective output capacitance are given by:
- the stored energy is:
- the characteristic impedance of the strip line composing the spiral is:
- the spiral line pulse generator 12 it is preferable to include the spiral line pulse generator 12 within an outer jacket of the light source. In this situation, the spiral line pulse generator 12 must meet certain additional requirements. It is important that the spiral line pulse generator 12 have a compact physical size. Furthermore, when the spiral line pulse generator 12 is included within the outer jacket of the light source, it must be capable of withstanding the considerable heat generated by the discharge lamp. In a typical application, the spiral line pulse generator 12 must be capable of operation at 200°C.
- the discharge lamp can be started by output pulses of less than ten kilovolts in amplitude by increasing the energy content of the pulse. Since output pulses of maximum amplitude and minimum duration are not necessarily required, the spiral line pulse generator design requirements and the switch speed requirements described hereinabove can be relaxed.
- the conductors were aluminum foil having a thickness of 1.8 x 10- 3 cm (0.0007") and a width of 1.27 cm (0.5") and the insulators were polyimide film dielectric having a thickness of 1.2 x 10- 4 cm (0.00048") and a width of 2.54 cm (1").
- the two conductors, separated by the two insulators, were wound on a cylindrical form having a diameter of 1.78 cm (0.7"). Approximately 130 turns were to provide a capacitance of approximately 0.5 micro- farad.
- the insulators were wider than the conductors to prevent arcing between turns at the edges of the conductors.
- a light source configuration providing automatic operation is illustrated in schematic form in _ FIG. 5.
- a discharge lamp 50 corresponds exactly to the discharge lamp 10 shown in FIG. 1 and described hereinabove.
- a spiral line pulse generator 52 shown symbolically in FIG. 5 corresponds to the spiral line pulse generator 12 shown in FIGS. 1, 2, and 3 and described hereinabove.
- AC power is coupled to electrodes 54 at opposite ends of the discharge lamp 50 and is coupled through a current limiting resistor 56 to one end of one conductor of the spiral line pulse generator 52.
- the output of the spiral line pulse generator 52 is coupled to one end of a conductor 58 located in close proximity to an outer surface of the discharge lamp 50 but not coupled to the electrodes 54.
- a self-heated thermal switch 60 includes a bimetallic switch 62 having a normally closed contact 64 and a normally open contact 66 and further includes a heater element 68.
- the normally open contact 66 of the bimetallic switch 62 is coupled to the one conductor of the spiral line pulse generator 52.
- the normally closed contact 64 of the bimetallic switch 62 is coupled through the heater element 68 and through a normally closed disabling switch 70 to the ac input.
- a common contact 72 of the bimetallic switch 62 and the other conductor of the spiral line pulse generator 52 are coupled to ground.
- the disabling switch 70 is a bimetallic switch which is located in proximity to the discharge lamp 50 and senses the temperature of the discharge lamp 50.
- a starting circuit 76 comprising the spiral line pulse generator 52, the resistor 56, the thermal switch 60, and the disabling switch 70, has an output 78, which is the output of the spiral line pulse generator 52, coupled to the conductor 58.
- normally open contact 66 provides a short circuit across the conductors of the spiral line pulse generator 52, thus producing at the output of the spiral line pulse generator 52 a high voltage, short duration pulse which initiates discharge in the discharge lamp 50.
- the heat produced by the discharge in the lamp 50 causes the disabling switch 70 to open, thereby disabling the thermal switch 60.
- the switch 70 remains in the closed position and the bimetallic switch 62 cools since the heater element 68 is no longer energized.
- the bimetallic switch 62 cools to a predetermined temperature, it switches back to the normally closed contact 64 and current again flows through the heater element 68.
- the temperature of the heater element 68 and the bimetallic switch 62 again rises and causes switching of the bimetallic switch 62 to the normally open contact 66 and a second high voltage, short duration pulse is generated by the spiral line pulse generator 52. This process continues automatically until a discharge is initiated in the discharge lamp 50.
- the bimetallic switch 62 must provide a low inductance short circuit across the spiral line pulse generator 52 for optimum performance of the spiral line pulse generator 52.
- the configuration of FIG. 5 provides automatic generation of starting pulses until a discharge is initiated in the discharge lamp 50.
- FIG. 6 A physical embodiment of the light source shown in schematic form in FIG. 5 is illustrated in FIG. 6.
- the discharge lamp 50 is enclosed by a light transmitting outer jacket 80. Power is received by a lamp base 82 and conducted through a lamp stem 84 by conductors 86 and 88 to the electrodes of the discharge lamp 50.
- the conductors 86 and 88 are sufficiently rigid to provide mechanical support for the discharge lamp 50.
- the starting circuit 76 is located in the base region of the outer jacket 80 surrounding the lamp stem 84. This location of the starting circuit 76 is chosen to minimize blockage of light emitted by the discharge lamp 50.
- the starting circuit 76 includes the spiral line pulse generator 52, the resistor 56, the thermal switch 60 and the switch 70 connected as shown in FIG. 5.
- the output 78 of the starting circuit 76 is coupled to the conductor 58 which is located in close proximity to an outer surface of the discharge lamp 50.
- the location of the starting circuit 76 as shown in FIG. 6 is advantageous because the generally cylindrical shape of the spiral line pulse generator 52 is compatible with the annular space available in the lamp base.
- the spiral line pulse generator 52 can become too large for inclusion within the outer jacket 80.
- the starting circuit 76 can be located external to the outer jacket 80, for example, in the light fixture in which the light source is mounted.
- the pulse energy requirements for starting of the discharge lamp 50 increase as the pressure of the noble gas included within the lamp increases.
- a lamp having a xenon pressure of about 13.3,10 2 Pa (10 Torr) requires a starting pulse of approximately 2 to 5 millijoules while a lamp having a xenon pressure of about 400 x 10 2 Pa (300 Torr) requires a starting pulse of approximately 70 to 100 millijoules.
- the igniter commonly used in high pressure sodium lamp ballasts does not provide' pulses of sufficient voltage to start lamps containing noble gases at pressures above about 133.10 2 Pa (100 Torr). Therefore, such lamps cannot be used in standard high pressure sodium lamp fixtures.
- the starting circuit 76 is included within the outer jacket 80 of the light source and is tailored for effective starting of the discharge lamp 50. Therefore, the light source shown in FIG. 6 can be used with standard high pressure sodium lamp ballasts. Furthermore, since the starting circuit is self-contained within the light source, the configuration of FIG. 6 can be utilized with mercury lamp ballasts, which do not contain an igniter.
- FIG. 7 An alternative light source configuration providing automatic operation is illustrated in schematic form in FIG. 7.
- the discharge lamp 50 and the spiral line pulse generator 52 are connected as shown in FIG. 5 and described hereinabove except that the thermal switch 60 and the disabling switch 70 of FIG. 5 are replaced by a spark gap 90.
- the spark gap 90 is a two terminal device which is connected directly across the conductors of the spiral line pulse generator 52.
- the spark gap 90 is normally an open circuit but switches to a short circuit when a voltage greater than a predetermined value is applied to the device.
- the predetermined firing voltage of the spark gap 90 is selected to be slightly less than the peak ac input voltage so that the spiral line pulse generator 52 achieves maximum output voltage.
- a starting circuit 92 including the spiral line pulse generator 52, the resistor 58, and the spark gap 90, has an output 94 coupled to the conductor 58.
- the starting circuit 92 can replace the starting circuit 76 shown in the light source of FIG. 6.
- an ac voltage typically provided by a lamp ballast
- the voltage across the spiral line pulse generator 52 illustrated in FIG. 8A, increases until the firing voltage of the spark gap 90 is reached at time To.
- the spark gap 90 rapidly short circuits the spiral line pulse generator 52 and a high voltage, short duration pulse, illustrated in FIG. 8B, is provided at the output of the spiral line pulse generator 52 at time To as described hereinabove.
- a high voltage pulse is produced by the spiral line pulse generator on each half cycle of the ac input voltage, as shown in FIG. 88, until starting of the discharge lamp 50. After the discharge lamp 50 is started, the voltage supplied by the lamp ballast to the light source is reduced and the spark gap 90 does not fire.
- FIG. 7 provides several advantages. (1) Starting pulses are produced when maximum potential exists across the discharge lamp 50, thus maximizing the probability of starting. (2) Starting pulses are produced at 120 Hz until starting occurs. (3) The starting circuit stops functioning automatically after the discharge lamp 50 starts. (4) The number of circuit components is minimal.
- the configuration of the conductor 20 in FIG. 1 and the conductor 58 in FIGS. 5-7 is of importance in efficient starting of the light source described herein.
- Conductors, such as the conductors 20 and 58, used for starting of discharge lamps are commonly referred to as starting aids.
- the energy required in the output pulse of the spiral line pulse generator can be reduced.
- a reduction in energy requirements is beneficial in two ways. For a given discharge lamp, the size of the spiral line pulse generator can be reduced, thus resulting in easier packaging of the spiral line pulse generator and lower cost. Second, a given spiral line pulse generator can be used to start discharge lamps with higher noble gas pressures.
- FIG. 9A there is shown a discharge lamp 100, corresponding to the discharge lamp 10 shown in FIG. 1 and described hereinabove.
- the discharge lamp 100 includes a light transmitting discharge tube 102 having electrodes 104 sealed therein at opposite ends.
- a starting aid 106 in the form of a fine wire, is wrapped around the outer surface of the discharge tube 102 in a spiral configuration having several turns.
- the starting aid 106 is coupled at its ends to a pulse generator.
- an ionization path 108 is formed in the interior of the discharge lamp 100 between the electrodes 104.
- the ionization path 108 follows the path of the starting aid 106 and therefore is spiral in configuration.
- a discharge lamp 110 corresponding to the discharge lamp 10 shown in FIG. 1 and described hereinabove, includes a discharge tube 112 having electrodes 114 sealed therein at opposite ends.
- a starting aid 116 in the form of a conductive wire harness, is disposed around the outer surface of the discharge tube 112.
- the starting aid 116 includes a number of circumferential portions 118 which surround the discharge tube 112 and a number of interconnecting portions 120 which connect the circumferential portions 118, thus forming a harness.
- an ionization path 122 is formed within the discharge tube 112 between the electrodes 114.
- the ionization path 122 follows the path of the conductor which forms the starting aid 116.
- the ionization path 122 includes portions 124 which follow the circumferential portions 118 of the starting aid 116, and portions 126 which follow the interconnecting portions 120 of the starting aid 116.
- FIG. 10 there is shown a discharge lamp 130, corresponding to the discharge lamp 10 shown in FIG. 1 and described hereinabove.
- the discharge lamp 130 includes a transparent discharge tube 132 having electrodes 134 and 136 sealed therein at opposite ends.
- a starting aid 138 in the form of an elongated conductor in a generally straight configuration, is located in proximity to an outer surface of the discharge tube 132.
- the starting aid 138 is coupled to a generator of high voltage, short duration pulses and runs in a generally straight path between a region 140 proximate the electrode 134 and a region 142 proximate the electrode 136.
- the starting aid 138 can be mounted in proximity to the discharge tube 138 in any convenient manner which does not appreciably block the light output of the discharge lamp 130.
- insulating support brackets can be located at opposite ends of the discharge lamp 130.
- the conductor which forms the starting aid 138 is of sufficient diameter to have mechanical rigidity, a single insulating support bracket can be used.
- the starting aid 138 can be affixed to the outer surface of the discharge tube 132 by cement capable of withstanding the heat generated by the discharge lamp 130.
- an ionization path 144 is formed in the interior of the discharge lamp 130 between the electrodes 134 and 136.
- the ionization path 144 follows the path of the starting aid 138 and thus runs in a generally straight path between the electrodes 134 and 136.
- the formation of the ionization path 144 is dependent upon the peak pulse voltage applied to the starting aid 138. Whether the degree of ionization develops further to form an arc discharge between the electrodes 134 and 136 depends upon the initial conductivity of the ionization path 144.
- Conductivity in turn depends on the degree of ionization and electron temperature and is directly related to the energy initially supplied by the starting pulse.
- very narrow high voltage pulses can, in some cases, produce ionization but can fail to produce sufficient conductivity in the ionization path 144 to induce further development of a self- sustained discharge.
- the ionization path 144 in FIG..10 is free of extraneous circumferential turns.
- the length of the ionization path 144 is less than either of the ionization paths 108 or 122, and less pulse energy is required to establish conditions suitable for arc formation or starting of the discharge lamp 130.
- thestarting aid 138 As shown in FIG. 10, is utilized, experiment has shown that a dischargetube containing 270-10' Pa (200 Torr) xenon can be started with a 25 kilovolt, 10 millijoules pulse of 10 nanosecond pulse width.
- the straight starting aid 138 shown in FIG. 10, enables reliable starting of high pressure sodium discharge lamps containing 400.10 2 Pa (300 Torr) xenon with 33 kilovolt, 15 millijoules pulses at a pulse width of 10 nanoseconds.
- starting aid 138 shown in FIG. 10, has been described in connection with a spiral line pulse generator, a starting aid having a generally straight configuration can be used with any pulse generator capable of generating the requisite high voltage, short duration pulses.
- the starting aid 138 is of particular importance when it is desired to minimize the size of the pulse generator or when it is desired to start discharge lamps having high energy starting requirements.
- a light source in which a spiral line pulse generator provides starting pulses of sufficient energy to start a discharge lamp containing high pressure noble gases.
- the spiral line pulse generator reduces the mass and volume associated with inductive starting circuits.
- the spiral line pulse generator has a physical configuration which can advantageously be included within a discharge lamp envelope.
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Description
- The invention relates to a light source, comprising a high pressure sodium discharge lamp including a discharge tube having first and second electrodes, sealed therein at opposite ends for receiving AC power and enclosing a fill material under high pressure which emits light during discharge, pulse generating means operative to provide at an output thereof a high voltage, short duration pulse of predetermined energy, and a starting aid electrode coupled to the output of said pulse generating means and disposed in close proximity to an outer.surface of said discharge tube for providing an ionization path between said electrodes when said starting aid electrode is energized by that pulse generating means.
- Such a light source- is known from US-A-4179640.
- High intensity discharge lamps, such as high pressure sodium lamps, commonly include noble gases at pressures. below 133·102 Pa (100 Torr). Lamps containing noble gases at pressures below 133·102 Pa (100 Torr) can be started and operated by utilizing an igniter in conjunction with a lamp ballast. The lamp ballast converts the ac line voltage to the proper amplitude and impedance level for lamp operation. The igniter provides pulses which assist in initiating discharge. The igniter is a relatively large and heavy circuit and is typically built into or located near the lamp ballast.
- It has been found that the inclusion in high pressure sodium lamps of xenon as the noble gas at pressures well in excess of 133·102 Pa (100 Torr) is beneficial to lamp performance. However, the pulse energy requirements for starting of the discharge lamp increase as the pressure of the xenon included within the lamp increases and the conventional igniter described above does not, by itself, produce reliable starting. Various approaches to starting discharge lamps containing high pressure xenon have been taken. A high voltage pulse is typically coupled to the discharge tube by a conductor known as a starting aid, as shown in the above-mentioned U.S. Patent No. 4,179,640 issued December 18, 1979 to Larson et al. The starting aids shown in the prior art have had the form of a wire wrapped around the discharge tube in a spiral configuration or a wire harness surrounding the discharge tube.
- From the EP-A-0,002,848, a starting aid electrode is known which is a conductor with a generally straight portion extending from a region proximate to one of the main electrodes towards a region proximate to the other main electrode.
- Starting aid configurations which more efficiently couple the starting pulse to the discharge lamp are desirable for several reasons. When starting pulse energy requirements are reduced by efficient coupling, the physical size and cost of the starting pulse generator circuit can be reduced. Physical size of the starting circuit is of particular importance when it is desired to include the starting circuit within the outer jacket of the lamp. Alternatively, more efficient coupling of the starting pulse facilitates starting of discharge lamps having higher starting pulse energy requirements.
- It is therefore, the object of the invention, to provide a light source of the type as mentioned above, which has a starting wire configuration so that only minimal pulse energy for the ignition of discharge is required.
- According to the present invention this task is solved by a light source as mentioned above, which is characterized in that said starting aid electrode is a conductor including a generally straight portion extending from a region proximate to one-of said electrodes towards a region proximate to the other of said electrodes, whereby said ionization path is generated by applying the AC voltage between the first and second electrodes and by applying at said starting aid electrode a high voltage pulse with respect to one of the first and second electrodes, said high voltage pulse being supplied by the pulse generating means.
- In preferred embodiments said conductor is supported by the outer surface of said discharge tube.
- Further preferred embodiments are disclosed in the further sub-claims.
- The invention will now be described with reference to the drawings:
- c FIG. 1 is a schematic diagram of a light source according to the present invention;
- FIG. 2 is a simplified schematic diagram of a spiral line pulse generator;
- FIG. 3 is a partial cross-sectional view of the spiral line pulse generator shown in FIG. 2;
- FIG. 4 is a graphic representation of the voltage output of the spiral line pulse generator of FIG. 2;
- FIG. 5 is a schematic diagram of a light source which provides automatic starting;
- FIG. 6 is an elevational view of a light source according to the present invention wherein the starting circuit is included within the outer jacket;
- FIG. 7 is a schematic diagram of another light source which provides automatic starting;
- FIG. 8 is a graphic representation of voltage waveforms which occur in the light source of FIG. 7;
- FIG. 9 is an elevational view, partly in cross- section, of high intensity discharge lamps illustrating starting aid configurations according to the prior art; and
- FIG. 10 is an elevational view, partly in cross- section, of a high intensity discharge lamp illustrating a low energy starting aid configuration.
- A high intensity light source is shown in FIG. 1 and includes a high
pressure discharge lamp 10, a spiralline pulse generator 12, aswitch 14, and anelongated conductor 20. Thedischarge lamp 10 is a high pressure sodium lamp and includes adischarge tube 22, typically made of alumina or other transparent ceramic material, havingelectrodes 24 sealed therein at opposite ends. Thedischarge tube 22 encloses a fill material, typically including sodium or a sodium amalgam and a noble gas or mixtures of nobles gases, which emits light during discharge. Theelectrodes 24 receive ac power from a lamp ballast at a voltage and current suitable for operation of thedischarge lamp 10. Anoutput 26 of the spiralline pulse generator 12 is coupled to one end of theconductor 20, typically a fine wire, which is located in close proximity to an outer surface of thedischarge tube 22. The configuration of theconductor 20 is of importance in efficient starting of the light source of FIG. 1 and is described in greater detail hereinafter. The spiralline pulse generator 12 receives electrical energy from a source of voltage Vo which can be the ac input to thedischarge lamp 10. Theswitch 14 is coupled to the spiralline pulse generator 12. In a manner which is fully described hereinafter, the spiralline pulse generator 12, after closure of theswitch 14, provides at its output a high voltage, short duration pulse which initiates discharge in thedischarge lamp 10. - The spiral
line pulse generator 12 is shown in simplified form in FIG. 2 for ease of understanding. A pair ofconductors line pulse generator 12 illustrating the layered construction of the device. A four layered arrangement of alternating conductors and insulators, including theconductors insulators form 38 in a multiple turn spiral configuration. Theform 38 provides mechanical rigidity. Theconductors - The operation of the spiral
line pulse generator 12 can be described with reference to FIG. 2, which schematically shows theconductors conductor 30 runs frompoint 40 topoint 42 while theconductor 32 runs frompoint 44 topoint 46. In the present example, theswitch 14 is coupled between theconductors points conductors switch 14, theconductor 30 has a uniform potential between thepoints conductor 32 has a uniform potential between thepoints switch 14 is rapidly closed, a field reversing wave propagates along the transmission line formed by theconductors points points points line pulse generator 12 is shown in FIG. 4. The output taken betweenpoint point 40 reaches a maximum voltage of 2nVo at t = 2T after the closure of theswitch 14. The operation of the spiral line pulse generator is described in further detail in U.S. Patent No. 3,289,015 and in Fitch et al., Novel Principle of Transient High Voltage Generation, Proc. IEE, Vol. 111, No. 4, April 1964. -
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- In optimizing performance of the spiral
line pulse generator 12, it is important to utilize low loss dielectric materials and conductors in order that the propagating wave maintain a fast rise- time compared to the transit time T of electromagnetic waves between the innermost turn and the outermost turn of the spiral line pulse generator. It is additionally important to maintain a large ratio of diameter to winding buildup (D/5) and to provide for a very low inductance switch to insure that the voltage between the conductors is switched in a time interval which is much shorter than T. The maximum permissible value of inductance for theswitch 14 is determined from the approximation known in the art that closure rise- time is approximately equal to L/Zo. Therefore, the following inequality must be met: L « TZo. For a typical design, L, the inductance of the switch, is on the order of one nanohenry or less. - As discussed hereinafter, it is preferable to include the spiral
line pulse generator 12 within an outer jacket of the light source. In this situation, the spiralline pulse generator 12 must meet certain additional requirements. It is important that the spiralline pulse generator 12 have a compact physical size. Furthermore, when the spiralline pulse generator 12 is included within the outer jacket of the light source, it must be capable of withstanding the considerable heat generated by the discharge lamp. In a typical application, the spiralline pulse generator 12 must be capable of operation at 200°C. - It has been determined that the energy content, rather than the amplitude or pulse width of the spiral line pulse generator output pulse, is the most important factor in effective starting of high pressure discharge lamps. The discharge lamp can be started by output pulses of less than ten kilovolts in amplitude by increasing the energy content of the pulse. Since output pulses of maximum amplitude and minimum duration are not necessarily required, the spiral line pulse generator design requirements and the switch speed requirements described hereinabove can be relaxed.
- In one example of a spiral line pulse generator, the conductors were aluminum foil having a thickness of 1.8 x 10-3 cm (0.0007") and a width of 1.27 cm (0.5") and the insulators were polyimide film dielectric having a thickness of 1.2 x 10-4 cm (0.00048") and a width of 2.54 cm (1"). The two conductors, separated by the two insulators, were wound on a cylindrical form having a diameter of 1.78 cm (0.7"). Approximately 130 turns were to provide a capacitance of approximately 0.5 micro- farad. The insulators were wider than the conductors to prevent arcing between turns at the edges of the conductors. Typically the voltage, ground, and output connections are made by means of tabs which are spot welded to the conductors during the winding of the spiral line pulse generator. When 200 volts is applied to this spiral line pulse generator, an output pulse of approximately 3500 volts and 30 nanoseconds is provided.
- The
low inductance switch 14, which is shown in FIG. 2 connected between theconductors line pulse generator 12, can alternatively be connected between theconductors points conductors conductors line pulse generator 12, the maximum voltage multiplication factor is obtained when the output is taken between the innermost turn and the outermost turn. - A light source configuration providing automatic operation is illustrated in schematic form in _ FIG. 5. A
discharge lamp 50 corresponds exactly to thedischarge lamp 10 shown in FIG. 1 and described hereinabove. A spiralline pulse generator 52 shown symbolically in FIG. 5 corresponds to the spiralline pulse generator 12 shown in FIGS. 1, 2, and 3 and described hereinabove. AC power is coupled toelectrodes 54 at opposite ends of thedischarge lamp 50 and is coupled through a current limitingresistor 56 to one end of one conductor of the spiralline pulse generator 52. The output of the spiralline pulse generator 52 is coupled to one end of aconductor 58 located in close proximity to an outer surface of thedischarge lamp 50 but not coupled to theelectrodes 54. Alternatively, the output of the spiral line pulse generator can be coupled to theelectrodes 54 of thedischarge lamp 50 in which case the ac power is coupled through a filter circuit to block the high voltage pulse from the source of power. A self-heatedthermal switch 60 includes a bimetallic switch 62 having a normally closedcontact 64 and a normally open contact 66 and further includes a heater element 68. The normally open contact 66 of the bimetallic switch 62 is coupled to the one conductor of the spiralline pulse generator 52. The normally closedcontact 64 of the bimetallic switch 62 is coupled through the heater element 68 and through a normally closed disabling switch 70 to the ac input. A common contact 72 of the bimetallic switch 62 and the other conductor of the spiralline pulse generator 52 are coupled to ground. The disabling switch 70 is a bimetallic switch which is located in proximity to thedischarge lamp 50 and senses the temperature of thedischarge lamp 50. A startingcircuit 76, comprising the spiralline pulse generator 52, theresistor 56, thethermal switch 60, and the disabling switch 70, has anoutput 78, which is the output of the spiralline pulse generator 52, coupled to theconductor 58. - In operation, when ac power, typically provided by a lamp ballast, is applied to the light source of FIG. 5, the spiral
line pulse generator 52 is charged through theresistor 56. At the same time, current flows through the switch 70, the heater 68 and the bimetallic switch 62, thus increasing the temperature of the heater element 68. The heater element 68 is in close proximity to the bimetallic switch 62 and causes heating of the bimetallic switch 62. When the heater element 68 reaches a predetermined temperature, the bimetallic switch 62 switches from normally closedcontact 64 to normally open contact 66. The closure of normally open contact 66 provides a short circuit across the conductors of the spiralline pulse generator 52, thus producing at the output of the spiral line pulse generator 52 a high voltage, short duration pulse which initiates discharge in thedischarge lamp 50. The heat produced by the discharge in thelamp 50 causes the disabling switch 70 to open, thereby disabling thethermal switch 60. - If, for any reason, the first spiral
line pulse generator 52 output pulse did not initiate discharge in thedischarge lamp 50, the switch 70 remains in the closed position and the bimetallic switch 62 cools since the heater element 68 is no longer energized. When the bimetallic switch 62 cools to a predetermined temperature, it switches back to the normally closedcontact 64 and current again flows through the heater element 68. The temperature of the heater element 68 and the bimetallic switch 62 again rises and causes switching of the bimetallic switch 62 to the normally open contact 66 and a second high voltage, short duration pulse is generated by the spiralline pulse generator 52. This process continues automatically until a discharge is initiated in thedischarge lamp 50. At that time the increase in temperature of thedischarge lamp 50 causes the switch 70 to open and thethermal switch 60 to be disabled. As discussed hereinabove, the bimetallic switch 62 must provide a low inductance short circuit across the spiralline pulse generator 52 for optimum performance of the spiralline pulse generator 52. The configuration of FIG. 5 provides automatic generation of starting pulses until a discharge is initiated in thedischarge lamp 50. - A physical embodiment of the light source shown in schematic form in FIG. 5 is illustrated in FIG. 6. The
discharge lamp 50 is enclosed by a light transmittingouter jacket 80. Power is received by alamp base 82 and conducted through alamp stem 84 byconductors discharge lamp 50. Theconductors discharge lamp 50. The startingcircuit 76 is located in the base region of theouter jacket 80 surrounding thelamp stem 84. This location of the startingcircuit 76 is chosen to minimize blockage of light emitted by thedischarge lamp 50. The startingcircuit 76 includes the spiralline pulse generator 52, theresistor 56, thethermal switch 60 and the switch 70 connected as shown in FIG. 5. Theoutput 78 of the startingcircuit 76 is coupled to theconductor 58 which is located in close proximity to an outer surface of thedischarge lamp 50. The location of the startingcircuit 76 as shown in FIG. 6 is advantageous because the generally cylindrical shape of the spiralline pulse generator 52 is compatible with the annular space available in the lamp base. When very high energy levels are required to start thedischarge lamp 50, the spiralline pulse generator 52 can become too large for inclusion within theouter jacket 80. In this instance, the startingcircuit 76 can be located external to theouter jacket 80, for example, in the light fixture in which the light source is mounted. The pulse energy requirements for starting of thedischarge lamp 50 increase as the pressure of the noble gas included within the lamp increases. For example, a lamp having a xenon pressure of about 13.3,102 Pa (10 Torr) requires a starting pulse of approximately 2 to 5 millijoules while a lamp having a xenon pressure of about 400 x 102 Pa (300 Torr) requires a starting pulse of approximately 70 to 100 millijoules. The igniter commonly used in high pressure sodium lamp ballasts does not provide' pulses of sufficient voltage to start lamps containing noble gases at pressures above about 133.102 Pa (100 Torr). Therefore, such lamps cannot be used in standard high pressure sodium lamp fixtures. In the configuration shown in FIG. 6, the startingcircuit 76 is included within theouter jacket 80 of the light source and is tailored for effective starting of thedischarge lamp 50. Therefore, the light source shown in FIG. 6 can be used with standard high pressure sodium lamp ballasts. Furthermore, since the starting circuit is self-contained within the light source, the configuration of FIG. 6 can be utilized with mercury lamp ballasts, which do not contain an igniter. - An alternative light source configuration providing automatic operation is illustrated in schematic form in FIG. 7. The
discharge lamp 50 and the spiralline pulse generator 52 are connected as shown in FIG. 5 and described hereinabove except that thethermal switch 60 and the disabling switch 70 of FIG. 5 are replaced by aspark gap 90. Thespark gap 90 is a two terminal device which is connected directly across the conductors of the spiralline pulse generator 52. Thespark gap 90 is normally an open circuit but switches to a short circuit when a voltage greater than a predetermined value is applied to the device. In FIG. 7, the predetermined firing voltage of thespark gap 90 is selected to be slightly less than the peak ac input voltage so that the spiralline pulse generator 52 achieves maximum output voltage. A startingcircuit 92, including the spiralline pulse generator 52, theresistor 58, and thespark gap 90, has an output 94 coupled to theconductor 58. The startingcircuit 92 can replace the startingcircuit 76 shown in the light source of FIG. 6. - In operation, an ac voltage, typically provided by a lamp ballast, is applied to the configuration of FIG. 7. The voltage across the spiral
line pulse generator 52, illustrated in FIG. 8A, increases until the firing voltage of thespark gap 90 is reached at time To. Thespark gap 90 rapidly short circuits the spiralline pulse generator 52 and a high voltage, short duration pulse, illustrated in FIG. 8B, is provided at the output of the spiralline pulse generator 52 at time To as described hereinabove. By repetition of this process, a high voltage pulse is produced by the spiral line pulse generator on each half cycle of the ac input voltage, as shown in FIG. 88, until starting of thedischarge lamp 50. After thedischarge lamp 50 is started, the voltage supplied by the lamp ballast to the light source is reduced and thespark gap 90 does not fire. - The configuration of FIG. 7 provides several advantages. (1) Starting pulses are produced when maximum potential exists across the
discharge lamp 50, thus maximizing the probability of starting. (2) Starting pulses are produced at 120 Hz until starting occurs. (3) The starting circuit stops functioning automatically after thedischarge lamp 50 starts. (4) The number of circuit components is minimal. - As noted hereinabove, the configuration of the
conductor 20 in FIG. 1 and theconductor 58 in FIGS. 5-7 is of importance in efficient starting of the light source described herein. Conductors, such as theconductors - Various starting aid configurations are known in the prior art. Referring now to FIG. 9A, there is shown a
discharge lamp 100, corresponding to thedischarge lamp 10 shown in FIG. 1 and described hereinabove. Thedischarge lamp 100 includes a light transmittingdischarge tube 102 havingelectrodes 104 sealed therein at opposite ends. A startingaid 106, in the form of a fine wire, is wrapped around the outer surface of thedischarge tube 102 in a spiral configuration having several turns. The startingaid 106 is coupled at its ends to a pulse generator. Upon application of a high voltage, short duration pulse to the startingaid 106, anionization path 108 is formed in the interior of thedischarge lamp 100 between theelectrodes 104. Theionization path 108 follows the path of the startingaid 106 and therefore is spiral in configuration. - A similar configuration of a starting aid according to the prior art is shown in FIG. 9B. A
discharge lamp 110, corresponding to thedischarge lamp 10 shown in FIG. 1 and described hereinabove, includes adischarge tube 112 havingelectrodes 114 sealed therein at opposite ends. A starting aid 116, in the form of a conductive wire harness, is disposed around the outer surface of thedischarge tube 112. The starting aid 116 includes a number ofcircumferential portions 118 which surround thedischarge tube 112 and a number of interconnectingportions 120 which connect thecircumferential portions 118, thus forming a harness. When a high voltage, short duration pulse is applied to the starting aid 116, anionization path 122 is formed within thedischarge tube 112 between theelectrodes 114. Theionization path 122 follows the path of the conductor which forms the starting aid 116. Thus, theionization path 122 includesportions 124 which follow thecircumferential portions 118 of the starting aid 116, andportions 126 which follow the interconnectingportions 120 of the starting aid 116. - It has been found that the use of a straight wire starting aid results in superior starting of high intensity discharge lamps. Referring now to FIG. 10, there is shown a
discharge lamp 130, corresponding to thedischarge lamp 10 shown in FIG. 1 and described hereinabove. Thedischarge lamp 130 includes atransparent discharge tube 132 havingelectrodes aid 138, in the form of an elongated conductor in a generally straight configuration, is located in proximity to an outer surface of thedischarge tube 132. The startingaid 138 is coupled to a generator of high voltage, short duration pulses and runs in a generally straight path between aregion 140 proximate theelectrode 134 and aregion 142 proximate theelectrode 136. - The starting
aid 138 can be mounted in proximity to thedischarge tube 138 in any convenient manner which does not appreciably block the light output of thedischarge lamp 130. For example, insulating support brackets can be located at opposite ends of thedischarge lamp 130. When the conductor which forms the startingaid 138 is of sufficient diameter to have mechanical rigidity, a single insulating support bracket can be used. Alternatively, the startingaid 138 can be affixed to the outer surface of thedischarge tube 132 by cement capable of withstanding the heat generated by thedischarge lamp 130. - When a high voltage, short duration pulse, such as that generated by the spiral line pulse generator described hereinabove, is applied to the starting
aid 138, anionization path 144 is formed in the interior of thedischarge lamp 130 between theelectrodes ionization path 144 follows the path of the startingaid 138 and thus runs in a generally straight path between theelectrodes ionization path 144 is dependent upon the peak pulse voltage applied to the startingaid 138. Whether the degree of ionization develops further to form an arc discharge between theelectrodes ionization path 144. Conductivity in turn depends on the degree of ionization and electron temperature and is directly related to the energy initially supplied by the starting pulse. Thus very narrow high voltage pulses can, in some cases, produce ionization but can fail to produce sufficient conductivity in theionization path 144 to induce further development of a self- sustained discharge. In contrast to theionization path 108 in FIG. 9A and theionization path 122 in FIG. 9B, theionization path 144 in FIG..10 is free of extraneous circumferential turns. As a result, the length of theionization path 144 is less than either of theionization paths discharge lamp 130. - The reduction in requisite pulse energy has been shown by experiment to be roughly a factor of two for the starting
aid 138, shown in FIG. 10, as compared with the starting aids shown in FIGS. 9A and 98. This is generally consistent with the reduction achieved in the length of the ionization path by utilizing a straight starting aid. Using the prior art starting aid configuration illustrated in FIG. 9B, it . has been found that high pressure sodium lamps containing 270·102 Pa (200 Torr) xenon pressure require 35 kilovolt, 20 millijoules pulses, when the pulses are approximately 10 nanoseconds in width. A high pressure sodium lamp containing 400·102 Pa (300 Torr) xenon cannot be started within a reasonable voltage range using the starting aid shown in FIG. 98.Whenthestarting aid 138, as shown in FIG. 10, is utilized, experiment has shown that a dischargetube containing 270-10' Pa (200 Torr) xenon can be started with a 25 kilovolt, 10 millijoules pulse of 10 nanosecond pulse width. Thestraight starting aid 138, shown in FIG. 10, enables reliable starting of high pressure sodium discharge lamps containing 400.102 Pa (300 Torr) xenon with 33 kilovolt, 15 millijoules pulses at a pulse width of 10 nanoseconds. - It is to be understood that while the starting
aid 138, shown in FIG. 10, has been described in connection with a spiral line pulse generator, a starting aid having a generally straight configuration can be used with any pulse generator capable of generating the requisite high voltage, short duration pulses. The startingaid 138 is of particular importance when it is desired to minimize the size of the pulse generator or when it is desired to start discharge lamps having high energy starting requirements. - Thus there is provided by the present invention a light source in which a spiral line pulse generator provides starting pulses of sufficient energy to start a discharge lamp containing high pressure noble gases. The spiral line pulse generator reduces the mass and volume associated with inductive starting circuits. In addition, the spiral line pulse generator has a physical configuration which can advantageously be included within a discharge lamp envelope.
- Whilethere has been shown and described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (5)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US19378680A | 1980-10-02 | 1980-10-02 | |
US193786 | 1980-10-02 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0049466A2 EP0049466A2 (en) | 1982-04-14 |
EP0049466A3 EP0049466A3 (en) | 1982-09-15 |
EP0049466B1 true EP0049466B1 (en) | 1987-06-03 |
Family
ID=22715002
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81107750A Expired EP0049466B1 (en) | 1980-10-02 | 1981-09-29 | Low energy starting aid for high intensity discharge lamps |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0049466B1 (en) |
JP (1) | JPS5788695A (en) |
AR (1) | AR230350A1 (en) |
CA (1) | CA1167973A (en) |
DE (1) | DE3176240D1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19631188A1 (en) * | 1996-08-02 | 1998-02-05 | Heraeus Kulzer Gmbh | Discharge lamp arrangement |
DE102005061832A1 (en) * | 2005-12-23 | 2007-06-28 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | High pressure discharge lamp with improved ignitability and high voltage pulse generator |
DE102005061831A1 (en) * | 2005-12-23 | 2007-06-28 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | High pressure discharge lamp e.g. sodium high pressure lamp, has igniter with spiral-pulse-generator and charging resistor, where charging resistor is made from low temperature co-firing ceramic-material |
DE102006026749A1 (en) * | 2006-06-08 | 2007-12-13 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | High pressure discharge lamp with improved ignitability and high voltage pulse generator |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0002848A1 (en) * | 1977-12-16 | 1979-07-11 | Koninklijke Philips Electronics N.V. | Electrical high-pressure metal vapour discharge lamp |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1087933A (en) * | 1963-10-10 | 1967-10-18 | Atomic Energy Authority Uk | Improvements in or relating to electrical pulse generators |
US3569779A (en) * | 1968-12-23 | 1971-03-09 | Philips Corp | High voltage power supply for a flash discharge lamp |
US3890540A (en) * | 1974-02-19 | 1975-06-17 | John Ott Lab Inc | Apparatus for operating gaseous discharge lamps on direct current from a source of alternating current |
JPS5149579A (en) * | 1974-10-28 | 1976-04-28 | Hitachi Ltd | KOATSUNATORIUM URANPU |
GB1561621A (en) * | 1977-02-09 | 1980-02-27 | Gen Electric | Circuits for operating discharge lamps |
US4179640A (en) * | 1977-12-05 | 1979-12-18 | Westinghouse Electric Corp. | Hid sodium lamp which incorporates a high pressure of xenon and a trigger starting electrode |
NL7809055A (en) * | 1978-09-05 | 1980-03-07 | Philips Nv | GAS AND / OR VAPOR DISCHARGE LAMP. |
-
1981
- 1981-09-25 CA CA000386715A patent/CA1167973A/en not_active Expired
- 1981-09-29 EP EP81107750A patent/EP0049466B1/en not_active Expired
- 1981-09-29 DE DE8181107750T patent/DE3176240D1/en not_active Expired
- 1981-09-30 AR AR28693281A patent/AR230350A1/en active
- 1981-10-01 JP JP15493081A patent/JPS5788695A/en active Pending
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0002848A1 (en) * | 1977-12-16 | 1979-07-11 | Koninklijke Philips Electronics N.V. | Electrical high-pressure metal vapour discharge lamp |
Also Published As
Publication number | Publication date |
---|---|
AR230350A1 (en) | 1984-03-01 |
EP0049466A2 (en) | 1982-04-14 |
JPS5788695A (en) | 1982-06-02 |
DE3176240D1 (en) | 1987-07-09 |
EP0049466A3 (en) | 1982-09-15 |
CA1167973A (en) | 1984-05-22 |
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