SERIES REGULATED POWER SUPPLY FOR ARC DISCHARGE LAMPS UTILIZING INCANDESCENT LAMPS
United States Patent 3813576
A series regulated power supply for an arc discharge lamp is disclosed whereby at least one incandescent lamp is connected in series with the arc discharge lamp to establish a first current level. At least one other incandescent lamp is connected in shunt with the first lamp to establish a second current level. The incandescent lamps provide current regulation for the arc discharge lamp.
US Patent References:
Gaseous electric discharge arc lamp
Pirani et al. - November 1935 - 2020737
Gaseous electric discharge device
Abernathy - August 1943 - 2327755
Blinking light arrangement
Lanata - January 1961 - 2967976
Gaseous electric discharge arc lamp
Pirani et al. - November 1935 - 2020737
Gaseous electric discharge device
Abernathy - August 1943 - 2327755
Blinking light arrangement
Lanata - January 1961 - 2967976
Application Number:
05/273750
Publication Date:
05/28/1974
Filing Date:
07/21/1972
View Patent Images:
Export Citation:
Assignee:
RCA Corporation (New York, NY)
Primary Class:
Other Classes:
315/72, 315/49
International Classes:
H05B41/40; H05B41/38; H05B37/00
Field of Search:
315/DIG.5,DIG.7,58,71,72,179,205,149,152,49
Primary Examiner:
Saalbach H. K.
Assistant Examiner:
Dahl, Lawrence J.
Attorney, Agent or Firm:
Norton, Edward Tripoli Joseph J. S.
Claims:
What is claimed is
1. A circuit for operating an arc discharge lamp, from a source of potential, said arc discharge lamp passing a first level of current conduction during one condition and a second level of current conduction during a second condition, said circuit comprising:
2. The circuit according to claim 1 wherein said second means comprises a movable shutter means in proximity with said arc discharge lamp, said shutter means being positioned to substantially block the light from said arc discharge lamp when the current through said discharge lamp is at said first level of current conduction and said shutter means being positioned to substantially pass the light from said arc discharge lamp when the current through said arc discharge lamp is at said second level of conduction.
3. The circuit according to claim 2 further comprising means for operatively coupling said shutter means and said connecting means for simultaneously passing the light from said arc discharge lamp and establishing said second current level.
4. The circuit according to claim 3 wherein said means for coupling the shutter means and said connecting means includes a timing means for maintaining said second current level through said arc discharge lamp for a predetermined period of time.
5. The circuit comprising:
6. The circuit according to claim 5 wherein said second means comprises a shutter means in proximity with said arc discharge lamp and being arranged to block the light from said arc discharge lamp when the current through the arc discharge lamp is at said first level of current conduction and said shutter means being positioned to pass the light from said arc discharge lamp when the current through said arc discharge lamp is at a said second level of conduction.
7. The circuit according to claim 6 further comprising means for operatively coupling said shutter means and said connecting means for simultaneously passing the light from said arc discharge lamp and establishing said second current level.
8. The circuit according to claim 7 wherein said means for operatively coupling said shutter means and said connecting means includes a timing means for maintaining said second current level for a predetermined period of time.
1. A circuit for operating an arc discharge lamp, from a source of potential, said arc discharge lamp passing a first level of current conduction during one condition and a second level of current conduction during a second condition, said circuit comprising:
2. The circuit according to claim 1 wherein said second means comprises a movable shutter means in proximity with said arc discharge lamp, said shutter means being positioned to substantially block the light from said arc discharge lamp when the current through said discharge lamp is at said first level of current conduction and said shutter means being positioned to substantially pass the light from said arc discharge lamp when the current through said arc discharge lamp is at said second level of conduction.
3. The circuit according to claim 2 further comprising means for operatively coupling said shutter means and said connecting means for simultaneously passing the light from said arc discharge lamp and establishing said second current level.
4. The circuit according to claim 3 wherein said means for coupling the shutter means and said connecting means includes a timing means for maintaining said second current level through said arc discharge lamp for a predetermined period of time.
5. The circuit comprising:
6. The circuit according to claim 5 wherein said second means comprises a shutter means in proximity with said arc discharge lamp and being arranged to block the light from said arc discharge lamp when the current through the arc discharge lamp is at said first level of current conduction and said shutter means being positioned to pass the light from said arc discharge lamp when the current through said arc discharge lamp is at a said second level of conduction.
7. The circuit according to claim 6 further comprising means for operatively coupling said shutter means and said connecting means for simultaneously passing the light from said arc discharge lamp and establishing said second current level.
8. The circuit according to claim 7 wherein said means for operatively coupling said shutter means and said connecting means includes a timing means for maintaining said second current level for a predetermined period of time.
Description:
The present invention relates generally to power supplies for arc discharge lamps and more particularly to a series current regulated supply utilizing incandescent lamps for the current regulating element.
Power supplies of the type discussed herein are especially useful in the field of photolithography. That is, applications where a photoresist substance must be exposed to a certain light intensity. Power supplies of this general nature may be found in the production of integrated circuits and printed circuit boards. In such applications it is extremely important to expose the light sensitive substances to the same light intensity throughout a production run. In terms of the source which energizes the light, such as an arc discharge lamp, it is important to supply the lamp with substantially the same current for each exposure operation throughout the production run.
The usual series pass element in the prior art, for power supplies of the present type, is an inductive circuit element. One of the problems with the utilization of an inductive element, or a plurality of inductive elements, as the series pass device is that the high voltage transients generated by the collapsing field drastically reduces the life of the arc discharge lamp.
Another prior art arrangement is the utilization of a ballast resistor in series with the arc discharge lamp. This arrangement, however, does not provide any current regulation for the arc discharge lamp.
The present invention provides a power supply with good current regulation as well as insuring a long life for the light source. Another advantage of the present invention is its low cost and light weight due to the arrangement of the circuit elements.
In accordance with the present invention a circuit is provided for operating an arc discharge lamp from a source of potential. The discharge lamp passes a first current level during one condition and a second current level during a second condition. The circuit comprises at least one incandescent lamp which is connected in series with the arc discharge lamp, for establishing the first current level. At least one other incandescent lamp is also provided. Means are provided for connecting the at least one other lamp in shunt with the at least one lamp for establishing the second current level.
IN THE DRAWING
FIG. 1 is a partial schematic and partial block diagram of the preferred embodiment of the invention; and
FIG. 2 is a graph which compares the ballast characteristics of an inductor, a resistor and an incandescent lamp.
Referring now to FIG. 1, there is provided a pair of input terminals 10 and 11 and a ground terminal 12. In the particular embodiment shown in FIG. 1 the signal applied to input terminals 10 and 11 is a 220 volt, 60 Hz signal.
A first plurality of incandescent lamps L 1 and L 2 are connected in parallel with each other and one end of the parallel combination is connected to input terminal 10.
The other end of the parallel combination of incandescent lamps L 1 and L 2 is connected to one terminal 13 of an arc discharge lamp 14. In the particular embodiment shown, arc discharge lamp 14 is a mercury arc lamp having the commercial designation H 100A 4/T. The other terminal 15 of the arc lamp 14 has a connection back to input terminal 11.
The circuit thus far described shows a plurality of parallel connected incandescent lamps L 1 and L 2 connected in series relationship with the main light source, namely arc discharge lamp 14.
There is also provided a second bank or plurality of parallel connected incandescent lamps L 3 and L 4 . One end of the parallel combination of lamps L 3 and L 4 is also connected to input terminal 10. The other end of the parallel combination of lamps L 3 and L 4 is connected to a normally open switching device S.
Switching device S may be a mechanical switch, such as a relay, or an electrical switch, such as a thyristor. The function of switch S is to provide a connecting means between the first plurality of incandescent lamps L 1 and L 2 and the second plurality of incandescent lamps L 3 and L 4 such that when the switch S is selectively closed all of the incandescent lamps will be in parallel with each other with the total parallel combination of lamps L 1 - L 4 in series with the arc discharge lamp 14. In the embodiment of FIG. 1, the incandescent lamps used are 150 watt, 230 volt commercially available lamps.
In addition, there is provided a movable shutter SH. In one position the shutter SH substantially blocks the light emanating from arc discharge lamp 14 while in another position the shutter SH substantially passes the light from arc discharge lamp 14. A shutter control mechanism 16 is provided to move the shutter SH from its normally light blocking position to its light passing position.
There is also provided in FIG. 1 a timer 17 which is operatively coupled to the shutter control 16 and the switch S. In many applications it is desirable to have the shutter SH passing light from the arc lamp 14 for the same period of time that the normally open switch S is closed.
In operation the circuit just described functions in the following manner. When input terminals 10 and 11 are connected to a source of potential, say 220 volts at 60 Hz, and switch S is open, a certain current level is established through the arc discharge lamp 14. This certain current level is termed the standby current and is determined by the number and type of incandescent lamps in series with the arc lamp 14.
The standby current illuminates incandescent lamps L 1 and L 2 and preferably is high enough to just start the arc discharge lamp glowing. At this time the shutter SH is in its normally blocking position and therefore little, if any, light from the lamp 14 shines on the photoresist material (not shown) which is to be exposed.
Now the timer 17 is set for the desired length of time which may be of the order of seconds or minutes depending upon the type of photoresist material to be exposed. The operation of the timer 17 causes the switch S to close and the shutter SH to move to the non-blocking position. With switch S closed a new current level through lamp 14 is established and the desired light intensity, depending upon the new current level, is allowed to shine on the photoresist material. The second current level depends upon the types and the total number of lamps in shunt with each other and in series with lamp 14.
Referring now to FIG. 2, which is essentially a graph of the A.C. ballast characteristic for: (a) an inductor L; (b) a resistor R; (c) incandescent lamps L 1 and L 2 in parallel; and (d) incandescent lamps L 1 -L 4 in parallel. In each case the curves show the current-voltage characteristic for the particular arrangement which is to be placed in series with the arc discharge lamp.
The curves show that for the operating voltage E 1 (RMS) which appears across lamps L 1 and L 2 , a certain standby current level I 1 (RMS) is obtained. When lamps L 3 and L 4 are switched or connected into the system a second current level I 2 (RMS), which is the operating current level, is established.
Since the incandescent lamps exhibit a leveling off characteristic, i.e., small changes of current for changes of potential around the operating voltage E 1 , the circuit shown in FIG. 1 provides a current regulating function. The curves show that the regulation provided by the incandescent lamps is substantially better than that which would occur from the use of an inductor or a resistor in series with the arc lamp 14.
It will be evident from the foregoing that one may select the number and wattage of the incandescent lamps to establish any desired first and second current levels for the arc lamp 14.
In actual practice the arc lamp 14 previously mentioned was operated at 150 watts during the standby condition and 300 watts during the exposure condition. Thus, by not being forced to stay on at the higher output level on a continuous basis, the useful life of the arc discharge lamps is significantly extended.
In addition, it has been found that the operation of arc discharge lamps at higher than rated levels, for short periods of time, as in the present application, does not shorten the life span of the lamp.
Finally, the disclosed arrangement provides an additional advantage in that the natural characteristic of the incandescent lamps provides a surge current at turn-on which is helpful in starting the arc discharge lamp.
Power supplies of the type discussed herein are especially useful in the field of photolithography. That is, applications where a photoresist substance must be exposed to a certain light intensity. Power supplies of this general nature may be found in the production of integrated circuits and printed circuit boards. In such applications it is extremely important to expose the light sensitive substances to the same light intensity throughout a production run. In terms of the source which energizes the light, such as an arc discharge lamp, it is important to supply the lamp with substantially the same current for each exposure operation throughout the production run.
The usual series pass element in the prior art, for power supplies of the present type, is an inductive circuit element. One of the problems with the utilization of an inductive element, or a plurality of inductive elements, as the series pass device is that the high voltage transients generated by the collapsing field drastically reduces the life of the arc discharge lamp.
Another prior art arrangement is the utilization of a ballast resistor in series with the arc discharge lamp. This arrangement, however, does not provide any current regulation for the arc discharge lamp.
The present invention provides a power supply with good current regulation as well as insuring a long life for the light source. Another advantage of the present invention is its low cost and light weight due to the arrangement of the circuit elements.
In accordance with the present invention a circuit is provided for operating an arc discharge lamp from a source of potential. The discharge lamp passes a first current level during one condition and a second current level during a second condition. The circuit comprises at least one incandescent lamp which is connected in series with the arc discharge lamp, for establishing the first current level. At least one other incandescent lamp is also provided. Means are provided for connecting the at least one other lamp in shunt with the at least one lamp for establishing the second current level.
IN THE DRAWING
FIG. 1 is a partial schematic and partial block diagram of the preferred embodiment of the invention; and
FIG. 2 is a graph which compares the ballast characteristics of an inductor, a resistor and an incandescent lamp.
Referring now to FIG. 1, there is provided a pair of input terminals 10 and 11 and a ground terminal 12. In the particular embodiment shown in FIG. 1 the signal applied to input terminals 10 and 11 is a 220 volt, 60 Hz signal.
A first plurality of incandescent lamps L 1 and L 2 are connected in parallel with each other and one end of the parallel combination is connected to input terminal 10.
The other end of the parallel combination of incandescent lamps L 1 and L 2 is connected to one terminal 13 of an arc discharge lamp 14. In the particular embodiment shown, arc discharge lamp 14 is a mercury arc lamp having the commercial designation H 100A 4/T. The other terminal 15 of the arc lamp 14 has a connection back to input terminal 11.
The circuit thus far described shows a plurality of parallel connected incandescent lamps L 1 and L 2 connected in series relationship with the main light source, namely arc discharge lamp 14.
There is also provided a second bank or plurality of parallel connected incandescent lamps L 3 and L 4 . One end of the parallel combination of lamps L 3 and L 4 is also connected to input terminal 10. The other end of the parallel combination of lamps L 3 and L 4 is connected to a normally open switching device S.
Switching device S may be a mechanical switch, such as a relay, or an electrical switch, such as a thyristor. The function of switch S is to provide a connecting means between the first plurality of incandescent lamps L 1 and L 2 and the second plurality of incandescent lamps L 3 and L 4 such that when the switch S is selectively closed all of the incandescent lamps will be in parallel with each other with the total parallel combination of lamps L 1 - L 4 in series with the arc discharge lamp 14. In the embodiment of FIG. 1, the incandescent lamps used are 150 watt, 230 volt commercially available lamps.
In addition, there is provided a movable shutter SH. In one position the shutter SH substantially blocks the light emanating from arc discharge lamp 14 while in another position the shutter SH substantially passes the light from arc discharge lamp 14. A shutter control mechanism 16 is provided to move the shutter SH from its normally light blocking position to its light passing position.
There is also provided in FIG. 1 a timer 17 which is operatively coupled to the shutter control 16 and the switch S. In many applications it is desirable to have the shutter SH passing light from the arc lamp 14 for the same period of time that the normally open switch S is closed.
In operation the circuit just described functions in the following manner. When input terminals 10 and 11 are connected to a source of potential, say 220 volts at 60 Hz, and switch S is open, a certain current level is established through the arc discharge lamp 14. This certain current level is termed the standby current and is determined by the number and type of incandescent lamps in series with the arc lamp 14.
The standby current illuminates incandescent lamps L 1 and L 2 and preferably is high enough to just start the arc discharge lamp glowing. At this time the shutter SH is in its normally blocking position and therefore little, if any, light from the lamp 14 shines on the photoresist material (not shown) which is to be exposed.
Now the timer 17 is set for the desired length of time which may be of the order of seconds or minutes depending upon the type of photoresist material to be exposed. The operation of the timer 17 causes the switch S to close and the shutter SH to move to the non-blocking position. With switch S closed a new current level through lamp 14 is established and the desired light intensity, depending upon the new current level, is allowed to shine on the photoresist material. The second current level depends upon the types and the total number of lamps in shunt with each other and in series with lamp 14.
Referring now to FIG. 2, which is essentially a graph of the A.C. ballast characteristic for: (a) an inductor L; (b) a resistor R; (c) incandescent lamps L 1 and L 2 in parallel; and (d) incandescent lamps L 1 -L 4 in parallel. In each case the curves show the current-voltage characteristic for the particular arrangement which is to be placed in series with the arc discharge lamp.
The curves show that for the operating voltage E 1 (RMS) which appears across lamps L 1 and L 2 , a certain standby current level I 1 (RMS) is obtained. When lamps L 3 and L 4 are switched or connected into the system a second current level I 2 (RMS), which is the operating current level, is established.
Since the incandescent lamps exhibit a leveling off characteristic, i.e., small changes of current for changes of potential around the operating voltage E 1 , the circuit shown in FIG. 1 provides a current regulating function. The curves show that the regulation provided by the incandescent lamps is substantially better than that which would occur from the use of an inductor or a resistor in series with the arc lamp 14.
It will be evident from the foregoing that one may select the number and wattage of the incandescent lamps to establish any desired first and second current levels for the arc lamp 14.
In actual practice the arc lamp 14 previously mentioned was operated at 150 watts during the standby condition and 300 watts during the exposure condition. Thus, by not being forced to stay on at the higher output level on a continuous basis, the useful life of the arc discharge lamps is significantly extended.
In addition, it has been found that the operation of arc discharge lamps at higher than rated levels, for short periods of time, as in the present application, does not shorten the life span of the lamp.
Finally, the disclosed arrangement provides an additional advantage in that the natural characteristic of the incandescent lamps provides a surge current at turn-on which is helpful in starting the arc discharge lamp.