LIGHTING SYSTEM UTILIZING HIGH INTENSITY DISCHARGE LAMPS
United States Patent 3723808
A lighting system is disclosed in which high intensity discharge lamps (e.g. mercury vapor lamps) are operated in combination with other lamps (e.g. incandescent lamps) to afford consistent and improved lighting. Somewhat-conventional ballast circuits are disclosed for energizing a high intensity discharge lamp in any of three states including warm-up, illumination and recovery. Another lamp is then included in the system, to be energized under the control of the potential developed across the high intensity discharge lamp, referenced to a base potential that is somewhat intermediate to the extreme levels developed across the discharge lamp during its various phases of operation, as provided by the ballast circuit. Embodiments with both autotransformer and dual winding transformer ballast circuits are disclosed, along with various sources of the intermediate base potential.
US Patent References:
Fluorescent lamp circuit
Keiser et al. - April 1948 - 2439976
/3125705.html
Feinberg et al. - March 1964 - 3125705
Method for igniting several fluorescent lamps and circuit arrangement for carrying out this method
Elfers - March 1968 - 3372301
Fluorescent tube lighting system
Nathanson - August 1961 - 2996644
Fluorescent lamp circuit
Keiser et al. - April 1948 - 2439976
/3125705.html
Feinberg et al. - March 1964 - 3125705
Method for igniting several fluorescent lamps and circuit arrangement for carrying out this method
Elfers - March 1968 - 3372301
Fluorescent tube lighting system
Nathanson - August 1961 - 2996644
Application Number:
05/148375
Publication Date:
03/27/1973
Filing Date:
06/01/1971
View Patent Images:
Export Citation:
Assignee:
Smoot-Holman Company (Inglewood, CA)
Primary Class:
Other Classes:
315/144, 315/178
International Classes:
H05B35/00; H05B39/00
Field of Search:
315/DIG.5,97,144
Primary Examiner:
Kaufman, Nathan
Claims:
What is claimed is
1. An illumination system comprising:
2. An illumination system according to claim 1 wherein said ballast circuit comprises a transformer.
3. An illumination system according to claim 2 wherein said ballast circuit includes a capacitor.
4. An illumination system according to claim 2 wherein said transformer is an autotransformer.
5. An illumination system according to claim 4 wherein said means for providing a base-level potential comprises a tap into said autotransformer.
6. An illumination system according to claim 4 wherein said ballast circuit further includes a ballast choke.
7. An illumination system according to claim 1 wherein said lamp system comprises at least one incandescent lamp.
8. An illumination system according to claim 1 wherein said lamp system includes relay means for performing switching control operations.
9. An illumination system according to claim 1 wherein said ballast includes a two-winding transformer and a capacitor, and wherein said means for providing a base-level potential comprises a tap on said transformer.
10. An illumination system according to claim 9 wherein said auxiliary lamp system includes a relay.
1. An illumination system comprising:
2. An illumination system according to claim 1 wherein said ballast circuit comprises a transformer.
3. An illumination system according to claim 2 wherein said ballast circuit includes a capacitor.
4. An illumination system according to claim 2 wherein said transformer is an autotransformer.
5. An illumination system according to claim 4 wherein said means for providing a base-level potential comprises a tap into said autotransformer.
6. An illumination system according to claim 4 wherein said ballast circuit further includes a ballast choke.
7. An illumination system according to claim 1 wherein said lamp system comprises at least one incandescent lamp.
8. An illumination system according to claim 1 wherein said lamp system includes relay means for performing switching control operations.
9. An illumination system according to claim 1 wherein said ballast includes a two-winding transformer and a capacitor, and wherein said means for providing a base-level potential comprises a tap on said transformer.
10. An illumination system according to claim 9 wherein said auxiliary lamp system includes a relay.
Description:
BACKGROUND AND SUMMARY OF THE INVENTION
Illumination systems utilizing high intensity discharge lamps, e.g., gaseous discharge lamps such as mercury vapor units, have been in widespread use for some time. However, systems relying solely upon such lamps generally have two characteristics which present problems in certain applications. First, when such lamps are initially energized, a warm-up period of several minutes is required before any substantial illumination is provided. Second, if, for any reason, an operating discharge lamp is momentarily deenergized (as by power dip) a recovery period that is even longer than the warm-up period is required before the lamp is again functionally operative. In general, these considerations are somewhat characteristic of high intensity discharge lamps.
In the operation of a discharge lamp with a ballast circuit, during the initial starting or warm-up period, a glow discharge occurs between a main electrode of the lamp, and a starting electrode. The glow discharge involves a relatively small current and serves to ionize gas within the lamp, thereby reducing the resistance between the two main electrodes. When the resistance becomes sufficiently low, an arc strikes across the main electrodes, which in a mercury vapor lamp vaporizes the mercury to provide ionized current-carriers. With the arc established, the initial glow discharge is extinguished and the lamp becomes functionally operative.
After the arc strikes, the lamp operates efficiently to provide illumination. However, if, for any reason, the arc is extinguished, as in the event of a momentary power failure, it will not restrike until the unit has cooled (recovered) to a point of reduces pressure inside the lamp. Consequently, a recovery interval of several minutes longer than the initial warm-up starting period is required to restore illuminating operation. Thus, as indicated above, discharge lamps generally may be in any one of three distinct energized states, e.g., (1) glow discharge warm-up operation, (2) established arc, functionally operative, or (3) recovery prior to glow discharge.
In the past, high intensity discharge lighting systems have generally incorporated auxiliary lighting circuits embodying incandescent or fluorescent lamps, for operation during intervals when the discharge lamps were energized; however, not functionally operative. Various control circuits and devices, such as photocells, diodes, relays and so on, have been employed in the auxiliary lighting circuits, with the result that such circuits have generally been relatively expensive. Consequently, relatively few of the discharge luminaires in prior installations have been supported by other-type auxiliary lamps. Also, prior conventional installations (in which high intensity discharge lamps are supported by other lamps) have been limited to appropriate circumstances. For example, such systems are not particularly effective for installations involving relatively low ceilings. Also as prior systems employing both high intensity discharge lamps and other lamps conventionally extinguish the other lamps when not in use, "burned-out" other lamps are not always apparent. That is, for example, a discharge lamp may fail at a critical time, only to result in the energization of a "burned-out" incandescent lamp.
High intensity discharge lamps also present certain other difficulties in some applications. Specifically, such lamps tend to provide light that is somewhat deficient in red-orange components. Also such light tends to be stroboscopic, which light is sometimes objectionable. Additionally, somewhat conventional high intensity discharge systems often afford a reactive load, resulting in a less than optimum power factor for consumer.
In general, the present system employs other or auxiliary lamps to supplement discharge lamps during all periods of operation. Essentially, the other lamps are powered under control of the discharge lamps and associated ballast circuits, whereby additional structure is minimal, e.g., additional lamp sockets. Accordingly, the system is economical, as well as effective as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which constitute a part of this specification, exemplary embodiments exhibiting various objectives and features hereof are set forth, specifically:
FIG. 1 is a circuit diagram of a first embodiment of a system constructed in accordance with the present invention;
FIG. 2 is a schematic diagram of a second embodiment hereof;
FIG. 3 is a schematic diagram of a third embodiment hereof;
FIG. 4 is a schematic diagram of a fourth embodiment hereof;
FIG. 5 is a schematic diagram of one form of component which may be employed in the various embodiments of FIGS. 1 - 4; and
FIG. 6 is a schematic diagram of another component which may be embodied in the systems of FIGS. 1 - 4.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT
Referring initially to FIG. 1, there is shown a high intensity discharge lamp, e.g., mercury vapor lamp 12 (extreme right) which is represented by a symbol as repeatedly utilized herein. In accordance with convention, the lamp 12 incorporates a starting electrode (not shown) and two main electrodes, the operation of which is well known in the prior art and described above. The discharge lamp 12 is energized from a source of alternating-current power applied at terminals 14 (extreme left) through a ballast circuit or network 16 as generally indicated. An auxiliary lamp system 18, incorporating other lamps, is connected between the discharge lamp 12 and the ballast network 16 as will be described in detail. In general, the other lamps in the system 18 operate at substantially full power during the warm-up and recovery states of the discharge lamp 12. However, when the discharge lamp 12 is functionally operative to provide illumination, the other lamps operate at a reduced level of power to supplement the discharge lamp 12.
Considering the system of FIG. 1 in greater detail, the terminals 14 are connected through conductors 20 and 22 to the ends of a winding 24. A tap 26, located substantially at the center of the winding 24 is connected through a winding 28 and a capacitor 30 to one electrode 31 of the discharge lamp 12. The other electrode 33 (lower as shown) of the discharge lamp 12 is returned to the winding 24 at a common point with conductor 22. Another tap 32 on the winding 24 is connected through the auxiliary lamp system 18 to a junction point 34 that is located between the capacitor 30 and the electrode 31 of the discharge lamp 12.
In the operation of the system of FIG. 1, with the initial application of alternating-current power across the terminals 14, a current is established through the winding 24 which constitutes an autotransformer with the inductively-coupled winding 28. Accordingly, the potential across the discharge lamp 12 establishes a glow discharge therein with the result that a relatively low potential exists across the discharge lamp 12. For example, if the applied-power potential across the terminals 14 is 120 volts, the potential across the discharge lamp 12 during "warm-up" may be approximately 10 volts.
After the discharge lamp 12 becomes operative to provide illumination, it develops a substantial potential drop, e.g., 135volts. The voltage drop across the discharge lamp 12 will be even greater during recovery intervals when neither the arc nor the glow discharge is carrying current. Specifically, following the previous example, during the cooling operation of a recovery or restrike interval, the potential across the discharge lamp may approximate 240 volts.
The various voltage drops which may appear across the discharge lamp 12 are accommodated by the ballast network 16. For example, the autotransformer incorporating winding 28 limits the flow of current and also affords an elevated potential to strike the arc in the discharge lamp 12. Generally, various configurations for the ballast network 16 are well known in the prior art, and in accordance herewith, the auxiliary lamp system 18 is controlled in a desirable manner by the operating characteristics of the ballast network 16 and the discharge lamp 12.
The auxiliary lamp system 18 is referenced to a potential appearing at the tap 32 which is somewhat intermediate to the extreme potentials developed across the discharge lamp 12. For example, the tap 32 may provide a potential of approximately one-half the open-circuit restrike voltage drop across the discharge lamp 12 e.g., 120 volts. The provision of such a reference potential to the lamp system 18, which is in turn connected to receive the potential at the discharge lamp 12, accomplishes a particularly effective, desirable and efficient system.
Pursuing the exemplary voltages considered above with reference to FIG. 1, during the initial starting or warm-up interval, when the potential across the discharge lamp is some 10 volts, the potential across the lamp system 18 will be approximately 115 volts. Consequently, although the discharge lamp 12 is ineffective during such interval, the lamp system 18 is operating at an effective, full-power level. During illuminating operation of discharge lamp 12, the potential thereacross may raise to some 135 volts resulting in a drop in potential across the lamp system 18 to some 85 volts e.g., reduced power operation.
During low-power operation of the lamp system 18, the discharge lamp 12 provides light that is somewhat stroboscopic and red-deficient in nature. However, that light is effectively supplemented by the warmer steady light of the lamp system 18. Also, in the event of any failure in the lamp system 18, it is immediately noticeable affording an opportunity for replacement. Additionally, the resistive load offered by the lamp system 18 tends to improve the power factor of the overall system. Finally, it is also noteworthy that the low-power operation of the lamp system 18 results in long life for individual lamps, e.g., incandescent units, in the system 18.
As suggested, the lamp system 18 as well as a similar structure incorporated in the embodiment of FIGS. 2, 3 and 4 may take a variety of different forms. For example, as shown in FIG. 5, a relay 38 may be provided for interconnection between the tap 32 and the junction point 34, in order to control contacts 40 which in turn energize an auxiliary unit 42 including at least one other lamp. Alternatively, the lamp system 18 may simply comprise one or more incandescent lamps 44 (FIG. 6) mounted in close proximity to a discharge lamp 12, and variously connected to terminals 46 which are connected respectively to the tap 32 and junction point 34.
In view of the above description of the system of FIG. 1, it will be apparent that a number of different design considerations may be applied to result in a variety of systems. For example, it may be desirable to employ a conventional two-winding transformer rather than an autotransformer unit. It may also be desirable to provide the reference level potential or voltage for the auxiliary lamp system 18 from a source external of the ballast network. Also, it may be desirable to vary the location of taps to the transformer 24, to accomplish various desired operating characteristics and accommodate different levels of potential. Thus, although a wide variety of systems utilizing the principles hereof will be readily apparent to those skilled in the art, additional specific examples of specific embodiments are disclosed by FIGS. 2, 3 and 4.
Considering the modifications of the embodiment of FIG. 2, wherein previously-identified components are similarly identified (as here throughout), the junction point 34 is connected through the lamp system 18 to receive an input at a terminal 50 in combination with a return terminal 52. Specifically, a base level potential is applied across the terminals 50 and 52, rather than to be provided from within the ballast circuit 16. The operation of the system of FIG. 2 is similar to that of the system of FIG. 1; however, the independent potential supplied across the terminals 50 and 52 is drawn from a source other than that which supplies the ballast network 16. However, the power applied to the auxiliary lamp system 18 is still controlled by the state of the discharge lamp 12.
FIG. 3 shows another embodiment of the present invention using an isolated dual-winding transformer and an independent potential source. Specifically, the terminals 14 are connected across the primary winding 56 of a transformer 58. The secondary winding 60, of the transformer 58, is connected in a serial loop incorporating a capacitor 62 and a discharge lamp 12. The auxiliary lamp system 18 is connected to a junction point 64 (between the lamp 12 and the capacitor 62) and to a terminal 50 which is connected to a base-level potential source 68, along with a return terminal 70.
The operation of isolated-winding conventional transformer ballast circuits is well known in the art of discharge lamps. Essentially, the transformer 50 in the ballast system of FIG. 3 operates in a somewhat conventional manner. However, the auxiliary lamp system 18 is energized by the potential difference that is developed between the junction point 64 and the applied-voltage terminal 50. Consequently, the operation of the lamp system is substantially as described above with reference to FIG. 1 wherein lamp system 18 is operative at full power levels during warm-up and restrike operations and is operative at a low-power level when the discharge lamp 12 is functionally operative, providing full illumination.
In still another embodiment (FIG. 4) as disclosed herein, an isolated two-winding transformer is employed and the base-level potential is provided from the ballast circuit. Specifically, the terminals 14 are connected across the primary winding 72 of a transformer 74 having a secondary winding 76. Common ends of the transformer windings 72 and 76 are joined by a conductor 78. The secondary winding 76 is connected in a loop with a capacitor 80 and a discharge lamp 12. The junction point 82 (between capacitor 80 and discharge lamp 12) is connected to the auxiliary lamp system 18, which is in turn referenced to a base-level potential provided from a tap 84 on the primary winding 72. Accordingly, the relatively-constant intermediate, base-level potential provided from the tap 84 references the potential to operate the lamp system 18 which is consequently controlled by the potential developed at the junction point 82. Again, the operation of the system is as described above in detail so that the lamp system 18 is continually operative; however, operates at a low-power level while the discharge lamp 12 is fully operative.
It may therefore be seen, that a wide variety of different possibilities for the present system are available. For example, with regard to FIGS. 1 and 4, the taps 32 and 84, respectively, may be variously placed to accomplish the desired base-level potential in relation to the input voltage. Of course, if desired, an additional winding portion may be added to the primary to accomplish greater flexibility. Also as well known in the art of ballast circuits, capacitors may be eliminated. It is also noteworthy that the system hereof is applicable to lamps of all wattages and may be incorporated for use with either a standard or a modified ballast. Finally, it should be appreciated that the other or auxiliary lamps will remain operative in the event of a total failure of associated discharge lamps. Of course, various other systems than those disclosed herein are clearly possible and, accordingly, the scope hereof is as defined by the claims set forth below.
Illumination systems utilizing high intensity discharge lamps, e.g., gaseous discharge lamps such as mercury vapor units, have been in widespread use for some time. However, systems relying solely upon such lamps generally have two characteristics which present problems in certain applications. First, when such lamps are initially energized, a warm-up period of several minutes is required before any substantial illumination is provided. Second, if, for any reason, an operating discharge lamp is momentarily deenergized (as by power dip) a recovery period that is even longer than the warm-up period is required before the lamp is again functionally operative. In general, these considerations are somewhat characteristic of high intensity discharge lamps.
In the operation of a discharge lamp with a ballast circuit, during the initial starting or warm-up period, a glow discharge occurs between a main electrode of the lamp, and a starting electrode. The glow discharge involves a relatively small current and serves to ionize gas within the lamp, thereby reducing the resistance between the two main electrodes. When the resistance becomes sufficiently low, an arc strikes across the main electrodes, which in a mercury vapor lamp vaporizes the mercury to provide ionized current-carriers. With the arc established, the initial glow discharge is extinguished and the lamp becomes functionally operative.
After the arc strikes, the lamp operates efficiently to provide illumination. However, if, for any reason, the arc is extinguished, as in the event of a momentary power failure, it will not restrike until the unit has cooled (recovered) to a point of reduces pressure inside the lamp. Consequently, a recovery interval of several minutes longer than the initial warm-up starting period is required to restore illuminating operation. Thus, as indicated above, discharge lamps generally may be in any one of three distinct energized states, e.g., (1) glow discharge warm-up operation, (2) established arc, functionally operative, or (3) recovery prior to glow discharge.
In the past, high intensity discharge lighting systems have generally incorporated auxiliary lighting circuits embodying incandescent or fluorescent lamps, for operation during intervals when the discharge lamps were energized; however, not functionally operative. Various control circuits and devices, such as photocells, diodes, relays and so on, have been employed in the auxiliary lighting circuits, with the result that such circuits have generally been relatively expensive. Consequently, relatively few of the discharge luminaires in prior installations have been supported by other-type auxiliary lamps. Also, prior conventional installations (in which high intensity discharge lamps are supported by other lamps) have been limited to appropriate circumstances. For example, such systems are not particularly effective for installations involving relatively low ceilings. Also as prior systems employing both high intensity discharge lamps and other lamps conventionally extinguish the other lamps when not in use, "burned-out" other lamps are not always apparent. That is, for example, a discharge lamp may fail at a critical time, only to result in the energization of a "burned-out" incandescent lamp.
High intensity discharge lamps also present certain other difficulties in some applications. Specifically, such lamps tend to provide light that is somewhat deficient in red-orange components. Also such light tends to be stroboscopic, which light is sometimes objectionable. Additionally, somewhat conventional high intensity discharge systems often afford a reactive load, resulting in a less than optimum power factor for consumer.
In general, the present system employs other or auxiliary lamps to supplement discharge lamps during all periods of operation. Essentially, the other lamps are powered under control of the discharge lamps and associated ballast circuits, whereby additional structure is minimal, e.g., additional lamp sockets. Accordingly, the system is economical, as well as effective as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, which constitute a part of this specification, exemplary embodiments exhibiting various objectives and features hereof are set forth, specifically:
FIG. 1 is a circuit diagram of a first embodiment of a system constructed in accordance with the present invention;
FIG. 2 is a schematic diagram of a second embodiment hereof;
FIG. 3 is a schematic diagram of a third embodiment hereof;
FIG. 4 is a schematic diagram of a fourth embodiment hereof;
FIG. 5 is a schematic diagram of one form of component which may be employed in the various embodiments of FIGS. 1 - 4; and
FIG. 6 is a schematic diagram of another component which may be embodied in the systems of FIGS. 1 - 4.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT
Referring initially to FIG. 1, there is shown a high intensity discharge lamp, e.g., mercury vapor lamp 12 (extreme right) which is represented by a symbol as repeatedly utilized herein. In accordance with convention, the lamp 12 incorporates a starting electrode (not shown) and two main electrodes, the operation of which is well known in the prior art and described above. The discharge lamp 12 is energized from a source of alternating-current power applied at terminals 14 (extreme left) through a ballast circuit or network 16 as generally indicated. An auxiliary lamp system 18, incorporating other lamps, is connected between the discharge lamp 12 and the ballast network 16 as will be described in detail. In general, the other lamps in the system 18 operate at substantially full power during the warm-up and recovery states of the discharge lamp 12. However, when the discharge lamp 12 is functionally operative to provide illumination, the other lamps operate at a reduced level of power to supplement the discharge lamp 12.
Considering the system of FIG. 1 in greater detail, the terminals 14 are connected through conductors 20 and 22 to the ends of a winding 24. A tap 26, located substantially at the center of the winding 24 is connected through a winding 28 and a capacitor 30 to one electrode 31 of the discharge lamp 12. The other electrode 33 (lower as shown) of the discharge lamp 12 is returned to the winding 24 at a common point with conductor 22. Another tap 32 on the winding 24 is connected through the auxiliary lamp system 18 to a junction point 34 that is located between the capacitor 30 and the electrode 31 of the discharge lamp 12.
In the operation of the system of FIG. 1, with the initial application of alternating-current power across the terminals 14, a current is established through the winding 24 which constitutes an autotransformer with the inductively-coupled winding 28. Accordingly, the potential across the discharge lamp 12 establishes a glow discharge therein with the result that a relatively low potential exists across the discharge lamp 12. For example, if the applied-power potential across the terminals 14 is 120 volts, the potential across the discharge lamp 12 during "warm-up" may be approximately 10 volts.
After the discharge lamp 12 becomes operative to provide illumination, it develops a substantial potential drop, e.g., 135volts. The voltage drop across the discharge lamp 12 will be even greater during recovery intervals when neither the arc nor the glow discharge is carrying current. Specifically, following the previous example, during the cooling operation of a recovery or restrike interval, the potential across the discharge lamp may approximate 240 volts.
The various voltage drops which may appear across the discharge lamp 12 are accommodated by the ballast network 16. For example, the autotransformer incorporating winding 28 limits the flow of current and also affords an elevated potential to strike the arc in the discharge lamp 12. Generally, various configurations for the ballast network 16 are well known in the prior art, and in accordance herewith, the auxiliary lamp system 18 is controlled in a desirable manner by the operating characteristics of the ballast network 16 and the discharge lamp 12.
The auxiliary lamp system 18 is referenced to a potential appearing at the tap 32 which is somewhat intermediate to the extreme potentials developed across the discharge lamp 12. For example, the tap 32 may provide a potential of approximately one-half the open-circuit restrike voltage drop across the discharge lamp 12 e.g., 120 volts. The provision of such a reference potential to the lamp system 18, which is in turn connected to receive the potential at the discharge lamp 12, accomplishes a particularly effective, desirable and efficient system.
Pursuing the exemplary voltages considered above with reference to FIG. 1, during the initial starting or warm-up interval, when the potential across the discharge lamp is some 10 volts, the potential across the lamp system 18 will be approximately 115 volts. Consequently, although the discharge lamp 12 is ineffective during such interval, the lamp system 18 is operating at an effective, full-power level. During illuminating operation of discharge lamp 12, the potential thereacross may raise to some 135 volts resulting in a drop in potential across the lamp system 18 to some 85 volts e.g., reduced power operation.
During low-power operation of the lamp system 18, the discharge lamp 12 provides light that is somewhat stroboscopic and red-deficient in nature. However, that light is effectively supplemented by the warmer steady light of the lamp system 18. Also, in the event of any failure in the lamp system 18, it is immediately noticeable affording an opportunity for replacement. Additionally, the resistive load offered by the lamp system 18 tends to improve the power factor of the overall system. Finally, it is also noteworthy that the low-power operation of the lamp system 18 results in long life for individual lamps, e.g., incandescent units, in the system 18.
As suggested, the lamp system 18 as well as a similar structure incorporated in the embodiment of FIGS. 2, 3 and 4 may take a variety of different forms. For example, as shown in FIG. 5, a relay 38 may be provided for interconnection between the tap 32 and the junction point 34, in order to control contacts 40 which in turn energize an auxiliary unit 42 including at least one other lamp. Alternatively, the lamp system 18 may simply comprise one or more incandescent lamps 44 (FIG. 6) mounted in close proximity to a discharge lamp 12, and variously connected to terminals 46 which are connected respectively to the tap 32 and junction point 34.
In view of the above description of the system of FIG. 1, it will be apparent that a number of different design considerations may be applied to result in a variety of systems. For example, it may be desirable to employ a conventional two-winding transformer rather than an autotransformer unit. It may also be desirable to provide the reference level potential or voltage for the auxiliary lamp system 18 from a source external of the ballast network. Also, it may be desirable to vary the location of taps to the transformer 24, to accomplish various desired operating characteristics and accommodate different levels of potential. Thus, although a wide variety of systems utilizing the principles hereof will be readily apparent to those skilled in the art, additional specific examples of specific embodiments are disclosed by FIGS. 2, 3 and 4.
Considering the modifications of the embodiment of FIG. 2, wherein previously-identified components are similarly identified (as here throughout), the junction point 34 is connected through the lamp system 18 to receive an input at a terminal 50 in combination with a return terminal 52. Specifically, a base level potential is applied across the terminals 50 and 52, rather than to be provided from within the ballast circuit 16. The operation of the system of FIG. 2 is similar to that of the system of FIG. 1; however, the independent potential supplied across the terminals 50 and 52 is drawn from a source other than that which supplies the ballast network 16. However, the power applied to the auxiliary lamp system 18 is still controlled by the state of the discharge lamp 12.
FIG. 3 shows another embodiment of the present invention using an isolated dual-winding transformer and an independent potential source. Specifically, the terminals 14 are connected across the primary winding 56 of a transformer 58. The secondary winding 60, of the transformer 58, is connected in a serial loop incorporating a capacitor 62 and a discharge lamp 12. The auxiliary lamp system 18 is connected to a junction point 64 (between the lamp 12 and the capacitor 62) and to a terminal 50 which is connected to a base-level potential source 68, along with a return terminal 70.
The operation of isolated-winding conventional transformer ballast circuits is well known in the art of discharge lamps. Essentially, the transformer 50 in the ballast system of FIG. 3 operates in a somewhat conventional manner. However, the auxiliary lamp system 18 is energized by the potential difference that is developed between the junction point 64 and the applied-voltage terminal 50. Consequently, the operation of the lamp system is substantially as described above with reference to FIG. 1 wherein lamp system 18 is operative at full power levels during warm-up and restrike operations and is operative at a low-power level when the discharge lamp 12 is functionally operative, providing full illumination.
In still another embodiment (FIG. 4) as disclosed herein, an isolated two-winding transformer is employed and the base-level potential is provided from the ballast circuit. Specifically, the terminals 14 are connected across the primary winding 72 of a transformer 74 having a secondary winding 76. Common ends of the transformer windings 72 and 76 are joined by a conductor 78. The secondary winding 76 is connected in a loop with a capacitor 80 and a discharge lamp 12. The junction point 82 (between capacitor 80 and discharge lamp 12) is connected to the auxiliary lamp system 18, which is in turn referenced to a base-level potential provided from a tap 84 on the primary winding 72. Accordingly, the relatively-constant intermediate, base-level potential provided from the tap 84 references the potential to operate the lamp system 18 which is consequently controlled by the potential developed at the junction point 82. Again, the operation of the system is as described above in detail so that the lamp system 18 is continually operative; however, operates at a low-power level while the discharge lamp 12 is fully operative.
It may therefore be seen, that a wide variety of different possibilities for the present system are available. For example, with regard to FIGS. 1 and 4, the taps 32 and 84, respectively, may be variously placed to accomplish the desired base-level potential in relation to the input voltage. Of course, if desired, an additional winding portion may be added to the primary to accomplish greater flexibility. Also as well known in the art of ballast circuits, capacitors may be eliminated. It is also noteworthy that the system hereof is applicable to lamps of all wattages and may be incorporated for use with either a standard or a modified ballast. Finally, it should be appreciated that the other or auxiliary lamps will remain operative in the event of a total failure of associated discharge lamps. Of course, various other systems than those disclosed herein are clearly possible and, accordingly, the scope hereof is as defined by the claims set forth below.