CA1042498A - Thermal regulator ballast - Google Patents
Thermal regulator ballastInfo
- Publication number
- CA1042498A CA1042498A CA211,094A CA211094A CA1042498A CA 1042498 A CA1042498 A CA 1042498A CA 211094 A CA211094 A CA 211094A CA 1042498 A CA1042498 A CA 1042498A
- Authority
- CA
- Canada
- Prior art keywords
- circuit
- capacitance
- ballast circuit
- ballast
- power
- Prior art date
- 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.)
- Expired
Links
Classifications
-
- 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
- H05B41/36—Controlling
-
- 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
- H05B41/36—Controlling
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
- H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
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- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A ballast for regulating current through at least one gaseous discharge lamp responsive to thermal conditions around the ballast. A capacity circuit including a power capacitance is utilized to provide at least a part of the current regulation. The capacity circuit is responsive to a change in temperature and is capable of switching either abruptly or gradually from one capacitance level to another capacitance level. The impedance of the capacity circuit is therefore increased as the temperature increases thereby limiting current through the at least one gaseous discharge lamp during a high temperature situation. Furthermore, this decrease in current has little, if any, overall effect on the light output of the lamp.
A ballast for regulating current through at least one gaseous discharge lamp responsive to thermal conditions around the ballast. A capacity circuit including a power capacitance is utilized to provide at least a part of the current regulation. The capacity circuit is responsive to a change in temperature and is capable of switching either abruptly or gradually from one capacitance level to another capacitance level. The impedance of the capacity circuit is therefore increased as the temperature increases thereby limiting current through the at least one gaseous discharge lamp during a high temperature situation. Furthermore, this decrease in current has little, if any, overall effect on the light output of the lamp.
Description
~04~
There is provided a ballast circuit for thermal regula-tion of at laast one gaseous discharge lamp~ More particularly there i~ provided a ballast including a capacity clrcuit which may ~e switched ~xom one capacitance level to another ~apacitance level in response to a temperaturel change.
In the fluorescent ballast art, it i~ de~irable to operate at ca~e temperatures no gr~ater than 90 C. Temperature~
much greater than thiS cause reduced life, ~ometimes cause noise, and may cause other problems related to exce~sive temperature~.
Several means have been employed to provide thermal protection for ballasts. One of these is kn~wn as a single shot end of life thermal protector. This protector could be placed in a circuit relationship with the core and coil and/or the ballast capacitor so that if the temperature of the ballast or its surroundings became too high ~hen the ballast would be taken out of the line. That is, the cir~uit would be open.
~owever, once the circuit i5 opened the ballast is generally removed permanently from the line.
Recycling protector3 also have been used and are widely u~ed in the motor industry~ They allow the circuit to open during a temperature overload and reclose after the temperature lowers. However, these types of devices are less reliable than the 3ingle shot technique and are more expensive.
Furthermore, recycling protectors cause the lamp to switch off thereby darkening the room and also shortening lamp life.
When a new building is under construction, a lighting system is one o~ the flrst things to be installed in~ide the building so that the workmen can see to do their work. Quite often the lighting system employes gaseous discharge lamps~
e.g. fluore~cent type, which require ballasts. These in~talla-; tions usually occur long before the air conditioning or other ventiliation systems are actuated. Under these conditions it is not uncommon for the combination of the ballast heat, the ~IL0~9~
fixture heat and the air in the ~naircondltioned room to cauRe ballaqt ca~e temp~ratures to exceed 110 C wherea~ ~luorescent ballasts ~hould normally operate between 90 and 95 C. ~rhi~
would cause a ~ingle shot protectc~r to trigger and the ballast would have to ba replaced~ It i~ therefore desirable to provide a thermal regulation mean~ whereby the ballast case temperature is thermally regulated rather than taken out of the line when the temperature exceeds a predetermined value.
U~ing ballasts operating ~luore~cent lamp~ on an average lighting fixutureO only about 20% of the input power i~
di~sipated in the ballast it3elf. Approximately 10% of the power i~ liberated as visible lightO The remaining 70% of the input power appears as heat liberated by the lamp within the ~ixture.
~herefore the primary source of balla~t case heat and fixture heat comes from the lamps themselves. m e most ef~ective means, therefore, for controlling the ballast thermal environment i5 to control the power dissipated in the lamp80 One might be~ieve that to reduce the power in a lamp would cause the light output of the lamp to also be reduced. However, between certain temperature ranges, thi~ is not true.
FIG. 7 shows a curve relating the light output o a typical fluorescent lamp to the ambient temperature. It can be ; seen that it is a characteristic o this fluorescent lamp having - fixed input power to operate at maximum light output near 25~ C
ambient and at lower light outputs on either side of the 25 C
point. It follows, therefore, that if a decrea~e in ambient temperature around the lamp from 70 C to 25 C results in a 20% increase in light output, then the light losses caused ~y the lowering of lamp power a certain percentage could nearly be compensated for because of the lamp characteristic.
One ~f the ob~ects of the invention is to provide a thermally-regulated ballast circuit.
There is provided a ballast circuit for thermal regula-tion of at laast one gaseous discharge lamp~ More particularly there i~ provided a ballast including a capacity clrcuit which may ~e switched ~xom one capacitance level to another ~apacitance level in response to a temperaturel change.
In the fluorescent ballast art, it i~ de~irable to operate at ca~e temperatures no gr~ater than 90 C. Temperature~
much greater than thiS cause reduced life, ~ometimes cause noise, and may cause other problems related to exce~sive temperature~.
Several means have been employed to provide thermal protection for ballasts. One of these is kn~wn as a single shot end of life thermal protector. This protector could be placed in a circuit relationship with the core and coil and/or the ballast capacitor so that if the temperature of the ballast or its surroundings became too high ~hen the ballast would be taken out of the line. That is, the cir~uit would be open.
~owever, once the circuit i5 opened the ballast is generally removed permanently from the line.
Recycling protector3 also have been used and are widely u~ed in the motor industry~ They allow the circuit to open during a temperature overload and reclose after the temperature lowers. However, these types of devices are less reliable than the 3ingle shot technique and are more expensive.
Furthermore, recycling protectors cause the lamp to switch off thereby darkening the room and also shortening lamp life.
When a new building is under construction, a lighting system is one o~ the flrst things to be installed in~ide the building so that the workmen can see to do their work. Quite often the lighting system employes gaseous discharge lamps~
e.g. fluore~cent type, which require ballasts. These in~talla-; tions usually occur long before the air conditioning or other ventiliation systems are actuated. Under these conditions it is not uncommon for the combination of the ballast heat, the ~IL0~9~
fixture heat and the air in the ~naircondltioned room to cauRe ballaqt ca~e temp~ratures to exceed 110 C wherea~ ~luorescent ballasts ~hould normally operate between 90 and 95 C. ~rhi~
would cause a ~ingle shot protectc~r to trigger and the ballast would have to ba replaced~ It i~ therefore desirable to provide a thermal regulation mean~ whereby the ballast case temperature is thermally regulated rather than taken out of the line when the temperature exceeds a predetermined value.
U~ing ballasts operating ~luore~cent lamp~ on an average lighting fixutureO only about 20% of the input power i~
di~sipated in the ballast it3elf. Approximately 10% of the power i~ liberated as visible lightO The remaining 70% of the input power appears as heat liberated by the lamp within the ~ixture.
~herefore the primary source of balla~t case heat and fixture heat comes from the lamps themselves. m e most ef~ective means, therefore, for controlling the ballast thermal environment i5 to control the power dissipated in the lamp80 One might be~ieve that to reduce the power in a lamp would cause the light output of the lamp to also be reduced. However, between certain temperature ranges, thi~ is not true.
FIG. 7 shows a curve relating the light output o a typical fluorescent lamp to the ambient temperature. It can be ; seen that it is a characteristic o this fluorescent lamp having - fixed input power to operate at maximum light output near 25~ C
ambient and at lower light outputs on either side of the 25 C
point. It follows, therefore, that if a decrea~e in ambient temperature around the lamp from 70 C to 25 C results in a 20% increase in light output, then the light losses caused ~y the lowering of lamp power a certain percentage could nearly be compensated for because of the lamp characteristic.
One ~f the ob~ects of the invention is to provide a thermally-regulated ballast circuit.
- 2 -, ~L0~4~8 Another object is to provide a ballast circuit having a capacity circuit whereby the capacitance sub~tantially changes in re~pon~e to a change in ambient temperature.
Anothsr obj~ct i~ to provide a ballast circuit having a capacity circuit for lncreasing the ballast c~rcuit impedance in respon~e to an increa~e in ambient temperature with little effect on light output.
Still another object is to provide a thermally regulated ballast operating near normal temperatures for providing a long balla~t life.
In accordance wit~ one form of this invention there i5 provided a ballast circuit for regulating the curr~nt through at least one gaseous discharge lamp over a range of ambient temperatures. A pair o input leads connect the baLlast circuit to a source of operating power. A transf~rmer i9 connected to the i~put leads. A capacity circuit including a power capacitance is connected between the tran~former and at least one lamp. ~he capacity circuit fur~her includes a m~ans for varying the total effective capacitance of the capacity circuit responsive to the ambient temperature whereb~ lamp power i5 substantially decreased in response to an increase in ambient temperature.
~he subject matter which is regarded as the inven~ion is ~et forth in t~e appended claLms. The invention itself, however, together with further ob~ects and advantages thereo may be better understood by reference to the following description taXen in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic circuit diagram of a ballast circuit showing a capacity circuit in block form.
FIG. 2 is a schematic circuit diagram of one embodiment of the capacity circuit as shown in FIG. 1.
Anothsr obj~ct i~ to provide a ballast circuit having a capacity circuit for lncreasing the ballast c~rcuit impedance in respon~e to an increa~e in ambient temperature with little effect on light output.
Still another object is to provide a thermally regulated ballast operating near normal temperatures for providing a long balla~t life.
In accordance wit~ one form of this invention there i5 provided a ballast circuit for regulating the curr~nt through at least one gaseous discharge lamp over a range of ambient temperatures. A pair o input leads connect the baLlast circuit to a source of operating power. A transf~rmer i9 connected to the i~put leads. A capacity circuit including a power capacitance is connected between the tran~former and at least one lamp. ~he capacity circuit fur~her includes a m~ans for varying the total effective capacitance of the capacity circuit responsive to the ambient temperature whereb~ lamp power i5 substantially decreased in response to an increase in ambient temperature.
~he subject matter which is regarded as the inven~ion is ~et forth in t~e appended claLms. The invention itself, however, together with further ob~ects and advantages thereo may be better understood by reference to the following description taXen in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic circuit diagram of a ballast circuit showing a capacity circuit in block form.
FIG. 2 is a schematic circuit diagram of one embodiment of the capacity circuit as shown in FIG. 1.
- 3 -, ~ 58-BD-6227 ~0~L~4~8 FIG. 3 is a Ychematic circuit diagram o~ another embodiment of the capacity circuit shown in FIG. 1.
FIG. 4 is a schematic ci.rcuit diagram of ~till another embodiment of the capacity circuit: shown in FI&. 1.
FI~. 5 is a schematic circuit diagram o~ still ~nother embodiment of the capacity circuit: shown in FIG. 1.
FIG~ 6 is a schematic circuit diagram of still another embodiment of the capacity circuit shown in FIG. 1. ~ ;
FIG. 7 is a graph showing the ~lationship between ~:
light output and ambient temperature near a fluorescent lamp.
FIG. 8 is a graph showing the relationship between the capacitanc~ and ambient temperature of a capacity compensation circuit.
Re~erring n~w to FIGo 1~ there is provided input terminals 1 and 2 adapted to receive input power for operating the ballast circuit. Input terminals 1 and 2 are ~urther conneted across primary winding 3 which is a part of tran ~ormer 4.
Transformer 4 further includes secondary winding 5. Secondary winding 5 i5 connected to capacity circuit 7 at terminal 8.
Terminals 8 and 11 are shown for ilLustrative purpos~s. Capacity circuit 7 includes a p~wer capacitance for aiding in ballasting a pair of gaseous di~charge l~mps 9 and 10. Capacity circui~ 7 also includes a means ~or substantially changing the e~fective capacitance of the capacity circuit 7 in re~ponse to a ~hange in temperature. This provides for thermal reg~lation of the ballast circuit.
Th2 ef~activa capacitance i3 the capacitance across texminals 8 and 11. This e~fective capacitance will substantially decrease as the temperature aroun~ capacity circuit 7 increases. :~
Thi decrease in capacitance w~ll result in an increase in net impedance of ~he ballast circuit~ The increase o~ impedance results in lass power consumed by the lamps 9 and 10. Since 9~
70% of the input power i~ di~sipated by the lamps, a sub tantial decrea~e in power will re~ult in al substantial decrea~e in ambient temperature. A~ shown in FIG. 7, a decrease in t~mp~ra-ture toward 25 C will result in highar light output at a fixed lamp power dissipation. The net re~ult i9 that the light output will remain nearly constant: while the temperature i~
lowered.
~he capacity circuit may include, but is not limited to, any of the circuits shown in FIGS. 2-6. It furthermore may only include a power capacitance means itself having the characteri tic of a reduction in capacitance as the ambient temperature increases. In order for this circuit to be extremely effective the decrea~e in capacitance should be approximately 15 to 20 percent for a change in tempsrature between 25 C to 70 C, however les~er changes in capacitance would be al~o advantageous, e.g. greater than about 7 percent.
The graph in FIG. 8 ~how.s illu~tratively how the - capacitance o~ the capacity circuit may decrea3e nearly 20 percent bekween 25 C and 70 C. This decrease in capacitance and the re~ultLng increase in impsdance will not substantially effect the light oukput of a fluore~cent type lamp. Again the grap~ in FIG. 7 illu~trates this. A ~luorescent lamp whose ambient i~ at 70 C will generate less light than a fluorescent lamp whose ambi~nt i~ 25 C) as~uming the power input is constant. By using thi~ khermal regulation technique the power dissipated by the lamp will decrease because o~ the increase ; in impedance in the balla3k circuit. However, as the lamp power is decreased the temperature of the ambient around the lamp will also begin to decrease and the lighk oukput should remain abouk the same.
The remainder of the circuit of FIG. 1 includes gasaou~ di~charge lamp 9 cvnnected to capacity circuit 7 at point ll~ Gaseous discharge lamp 9 has ~ilaments 12 and 13.
_ 5 _ Sfl-BD-6227 10~ L98 Filament 12 i8 connected to filament winding 14. Filament winding 14 is magnetically coupled to primary winding 3 to provide pre-hea~ for filament 12~ Filament ~3 i~ connected to filament winding 15. Filament winding 15 is ~ so magnetically coupled to primary winding 3 to provide filament pre-heat filament 13. Starting capacitor 16 i~ connected across lamp 9 at filaments 12 and 13. Lamp 10 includes filamant~ 17 and 18.
Filament 17 is also coupled to ~ilament 13 of lamp 9 and to filament winding 15 for providing pre heat. Filament 18 of gaseous discharge lamp 10 is connected to filament winding 6 for providing pre-heat for lamp 12. Secondary windlng 6 is connected to prlmary winding 3.
The circuit of FIG. 2 shows one embodiment of the capacity circuit which may be connected to the circuit of FIG. 1 across terminals 8 and 11. Power capacitance means 19 is connected between terminals 8 and 11 to help provide ballasting for lamps 9 and 10 and ~urther to provide power factor cvrrection. Circuit branch 20 is connected in parallel with power capacitance means 19. ~nis circuit branch 20 includes thermistor 21 which is a positive temperature coefficient resistor (PTC) well known to those skilled in the art. The second capacitor 22 is connected to the thermiskor 21 and is al~o included in circuit branch 20. Thermistor 21 may be of the type which either gradually increases its resistance as the temperature incxeases or undergoes an abrupt re~istance change whereby the capacitance means 22 is abruptly switched out of a circuit relationship with capacitor 19 when the temperature exceeds a predetermined value. With normal operating temperature ~ ;
of fluorescent ballast cases (90-95 C), capacitance means 22 is in a circuit relation with capacitance means 19 whereby the effective capacitance is relatively high.
The circuit of FIG. 3 is another capacity circuit and shows a power capacitor 19 having a variable ceramic capacitor .i . ,. . :
.~ : -: .
~IO~LZ~9~
23 connected thereacro~s. C~ramic capacltor 23 may also b~ a non-variable t~pe. Ceramic capacitors have been deslgned to undaryo a capacitance change of UE~ to 60 percent between 25 C
and 100 C. By placing the ceramic capacitor 23 in parallel with the power capacitor l9 a reductiorl in lamp current of nearly lO
percent between a temperature range of 24 C and 67 C has been measured. '~he po~er dissipated by tne lamp and the temperature are then lowared.
The circuit of FIG. 4 1~ still another capacity circuit and shows power capacitor 19 connected in parallel with a series combination of bimetal switch 24 and capacitor 25. Switch 24 may also be made of a non-metal material which is temperature sensitive. Switch 24 will be closed during low tamperatures and will be opened during high temperatures.
The embodiment shown in FIG. 5 shows power capacitor l9 connectQd in parallel with the ~eries combination of electr~nic switch 26, which in this embodiment is ~rRlAc~ and capacitor 27.
A thermal responsive resistor 28 is connected to the gate of TRIAC 26 so as to switch on the TRI~C 26 at a predetermined low temperature level. When capacitor 27 is switched into the parallel circuit the overall capacitanca between leads 8 and 11 increa~es. TRIAC 26 turns off at zero ~urrent cros~ing, then switching capacitor 27 out o~ the parallel circuit. '~his cause~
the overall capacitance to decrease~ Thermistor 28 may be a well known thermal responsive switch such as a P~rc resistor.
The embodiment shown in FIG~ 6 shows power capacitor l9 connected in series with a second capacitor 29. An electronic switch, which is in this embodiment TRIAC 30, is connected across se~ond capacitor 29. A thermal responsive switch 31 is connected to the gate of TRIAC 300 When a predatermined temperature is sensed by thermal resistor ~witch 31 TRIAC 30 turns on. This e~fectively ~witches capacitor 29 out of the .. ~, . . .. . . .
;, :, ~, . : . . - , . .
~ 5~-~D-6227 1(~4~498 circuit. Other types of capaci-ty circuits may be utilized.
For example, the power capacitor alone may be utilized whereby the internal structure of the power capacitance is made so that its capacity increases as the temperature around it decreases.
A paper-askarel capacitor has been used in the prior art which undergoes, at the most, a 3~ decrease in capacitance for a temperature rise between 25 C and 70 C. This small change, however, was deemed insubstantial. This is, its effect on thermal regulation was insignificant.
la An askarel-filled polypropylene film dielectric capaci-tor has been developed which undergoes a seven or eight percent decrease in capacitance when the temperature around it goes from 25 C to 70 C. This film capacitor may be used as a power capacitor. While this drop in capacitance was helpful in decreasing the overall temperature of the ballast and lamp, it is further helpful in that a savings in materials for the ballast may be realized. If one is willing to leave the temperature at a fairly hiyh point, smaller than normal sized transformer wire may be used. Seemingly this would cause the 2Q temperature to in¢rease but it would be compensated or by the capacity circuit. Furthermore-, dif~erent types and less expensive core materials may be used which allow the ballast to heat up but again the capacity circuit would compensate for this temperature increase.
One of the most desirahle ranges for thermal regulation is a 15% to 2Q~ change in capacitance. With a 15% to 20% droop, a ballast operating with an undesirable 110 C case may be regulated back to 90-95 C ~Yithout a significant change in light output. Another one of the benefits of a 15% to 20% reduction in capacitance is that the ballast and lamp may be operated at least within 95 percent of its normal unre~ulated light output hetween 7Q C and 25 C ambient. This, again, takes advantage of the light output to temperature phenomena illu~trated in the graph shown ln FI~. 7 whereby the light output increaseY as the temperature decrease~ between 70 C and 25 C. It has been shown by tests on the various circuit~ shown in FIGS~ 2-6 that this 95 percent light output may be achieved in ~ome environments even though the capacitance has decreased between 15 and 20 percent.
The circuit shown in FIG. 1 and incorporating t~e spacific capacity circuit of FIG. 2 operates in the following manner: input power is received across terminals 1 and 2. Fila-ment winding 6, 14 and 15 are energized to pre-heat the lamp filaments. me voltage on primary winding 3 is ~tepped up acro s secondary winding 5 and, the primary winding. Starting capacitor 16 is charged through power capacitor 19 and gaseous discharge lamps 9 and lO (in this example fluorescent lamps~ are started. A current flows from input terminal l through secondary winding 5 and power capacitance l9 and further through the filaments of lamps 9 and 10 bacX to other side of prim~ry winding 3 and input terminal 2. As the ambient temperature around and i the balla~t and ~ixture begins to rise, thermistor 21, shown in FIG. 2, begi~s to show more resistance. This particular thermistor switches, i~e. 50 ohms at 25 C and 105 ohms at 100~ C. merefore capacitox 22 is switched out of electrical parallel with powex capacitor l9. The capacity circuit therefore has less capacitance between terminal~ 8 and ll at a high t2mperature than it does at a relatively low temperature~ This decrease in capacitance results in an increase in o~erall circuit impedance. Capacitance i~ related to impedance by the ~ormula Z - ~ . Since the impedance is increased, the current through the lamps and therefore the power di~sipated by the lamps is decreased. With less power being dissipated by the lamps the overall temperature in the fixture and near the ballast will begin to ~ecrease. Thi5 9~
combined decrea3e ln lamp power and decrease in ambiant temperature will allow the light output to remaln nearly constant. A~ the temperaturs decrea~es sufficiently, the thermistor 21 will ~ense that the temperature i8 decreasing and ~witch capacitor 22 bacX into the capacity circuit. Thi~
switching of capacitor 22 in or out of the capacity circuit results in the thermal regulation of the ballast circuit.
A circuit has been built with the components shown in FIGS. 1 and 2 having the following set of value3:
Capacitor 19 - 3.4 MFd Capacitor 22 - 0.4 MFd Capacitor 16 - O.05 MFd PTC Resistor 21 R25OC - 50 Ohms.
Rl0ooc - 105 Ohms .
Primary Winding 3 - 823T, dia~ .0169"
Secondary Winding 5 - 1442T, dia. .0164"
Filament Winding 6 - 28T, dia. .0169"
Filament Winding 14 - 28T, dia~ .0169"
Filament Winding 15 - 28T, diaO .0169"
Lamp 9 ~ 40W rapid start fluore cent Lamp 10 ~ 40W rapid start fluorescent From the foregoing description of the lllustrative embodiments of the invention, it will be apparent that many :: :
modification~ may be made therein. For example, varlous type~
~: of capacity circuits may be used.w~ereby the thermal character- .
istics of the ballast circuit are substantially regulated. It will be understood, therefore, that the e embodiments of the invention are intended as an exemplification of tha invention - 30 only and that this invention is not limited thereto. It is also understood, therefore, that it is intended in the appended claims to cover all modifications that fall within the true spirit and scope o* ~his invention.
FIG. 4 is a schematic ci.rcuit diagram of ~till another embodiment of the capacity circuit: shown in FI&. 1.
FI~. 5 is a schematic circuit diagram o~ still ~nother embodiment of the capacity circuit: shown in FIG. 1.
FIG~ 6 is a schematic circuit diagram of still another embodiment of the capacity circuit shown in FIG. 1. ~ ;
FIG. 7 is a graph showing the ~lationship between ~:
light output and ambient temperature near a fluorescent lamp.
FIG. 8 is a graph showing the relationship between the capacitanc~ and ambient temperature of a capacity compensation circuit.
Re~erring n~w to FIGo 1~ there is provided input terminals 1 and 2 adapted to receive input power for operating the ballast circuit. Input terminals 1 and 2 are ~urther conneted across primary winding 3 which is a part of tran ~ormer 4.
Transformer 4 further includes secondary winding 5. Secondary winding 5 i5 connected to capacity circuit 7 at terminal 8.
Terminals 8 and 11 are shown for ilLustrative purpos~s. Capacity circuit 7 includes a p~wer capacitance for aiding in ballasting a pair of gaseous di~charge l~mps 9 and 10. Capacity circui~ 7 also includes a means ~or substantially changing the e~fective capacitance of the capacity circuit 7 in re~ponse to a ~hange in temperature. This provides for thermal reg~lation of the ballast circuit.
Th2 ef~activa capacitance i3 the capacitance across texminals 8 and 11. This e~fective capacitance will substantially decrease as the temperature aroun~ capacity circuit 7 increases. :~
Thi decrease in capacitance w~ll result in an increase in net impedance of ~he ballast circuit~ The increase o~ impedance results in lass power consumed by the lamps 9 and 10. Since 9~
70% of the input power i~ di~sipated by the lamps, a sub tantial decrea~e in power will re~ult in al substantial decrea~e in ambient temperature. A~ shown in FIG. 7, a decrease in t~mp~ra-ture toward 25 C will result in highar light output at a fixed lamp power dissipation. The net re~ult i9 that the light output will remain nearly constant: while the temperature i~
lowered.
~he capacity circuit may include, but is not limited to, any of the circuits shown in FIGS. 2-6. It furthermore may only include a power capacitance means itself having the characteri tic of a reduction in capacitance as the ambient temperature increases. In order for this circuit to be extremely effective the decrea~e in capacitance should be approximately 15 to 20 percent for a change in tempsrature between 25 C to 70 C, however les~er changes in capacitance would be al~o advantageous, e.g. greater than about 7 percent.
The graph in FIG. 8 ~how.s illu~tratively how the - capacitance o~ the capacity circuit may decrea3e nearly 20 percent bekween 25 C and 70 C. This decrease in capacitance and the re~ultLng increase in impsdance will not substantially effect the light oukput of a fluore~cent type lamp. Again the grap~ in FIG. 7 illu~trates this. A ~luorescent lamp whose ambient i~ at 70 C will generate less light than a fluorescent lamp whose ambi~nt i~ 25 C) as~uming the power input is constant. By using thi~ khermal regulation technique the power dissipated by the lamp will decrease because o~ the increase ; in impedance in the balla3k circuit. However, as the lamp power is decreased the temperature of the ambient around the lamp will also begin to decrease and the lighk oukput should remain abouk the same.
The remainder of the circuit of FIG. 1 includes gasaou~ di~charge lamp 9 cvnnected to capacity circuit 7 at point ll~ Gaseous discharge lamp 9 has ~ilaments 12 and 13.
_ 5 _ Sfl-BD-6227 10~ L98 Filament 12 i8 connected to filament winding 14. Filament winding 14 is magnetically coupled to primary winding 3 to provide pre-hea~ for filament 12~ Filament ~3 i~ connected to filament winding 15. Filament winding 15 is ~ so magnetically coupled to primary winding 3 to provide filament pre-heat filament 13. Starting capacitor 16 i~ connected across lamp 9 at filaments 12 and 13. Lamp 10 includes filamant~ 17 and 18.
Filament 17 is also coupled to ~ilament 13 of lamp 9 and to filament winding 15 for providing pre heat. Filament 18 of gaseous discharge lamp 10 is connected to filament winding 6 for providing pre-heat for lamp 12. Secondary windlng 6 is connected to prlmary winding 3.
The circuit of FIG. 2 shows one embodiment of the capacity circuit which may be connected to the circuit of FIG. 1 across terminals 8 and 11. Power capacitance means 19 is connected between terminals 8 and 11 to help provide ballasting for lamps 9 and 10 and ~urther to provide power factor cvrrection. Circuit branch 20 is connected in parallel with power capacitance means 19. ~nis circuit branch 20 includes thermistor 21 which is a positive temperature coefficient resistor (PTC) well known to those skilled in the art. The second capacitor 22 is connected to the thermiskor 21 and is al~o included in circuit branch 20. Thermistor 21 may be of the type which either gradually increases its resistance as the temperature incxeases or undergoes an abrupt re~istance change whereby the capacitance means 22 is abruptly switched out of a circuit relationship with capacitor 19 when the temperature exceeds a predetermined value. With normal operating temperature ~ ;
of fluorescent ballast cases (90-95 C), capacitance means 22 is in a circuit relation with capacitance means 19 whereby the effective capacitance is relatively high.
The circuit of FIG. 3 is another capacity circuit and shows a power capacitor 19 having a variable ceramic capacitor .i . ,. . :
.~ : -: .
~IO~LZ~9~
23 connected thereacro~s. C~ramic capacltor 23 may also b~ a non-variable t~pe. Ceramic capacitors have been deslgned to undaryo a capacitance change of UE~ to 60 percent between 25 C
and 100 C. By placing the ceramic capacitor 23 in parallel with the power capacitor l9 a reductiorl in lamp current of nearly lO
percent between a temperature range of 24 C and 67 C has been measured. '~he po~er dissipated by tne lamp and the temperature are then lowared.
The circuit of FIG. 4 1~ still another capacity circuit and shows power capacitor 19 connected in parallel with a series combination of bimetal switch 24 and capacitor 25. Switch 24 may also be made of a non-metal material which is temperature sensitive. Switch 24 will be closed during low tamperatures and will be opened during high temperatures.
The embodiment shown in FIG. 5 shows power capacitor l9 connectQd in parallel with the ~eries combination of electr~nic switch 26, which in this embodiment is ~rRlAc~ and capacitor 27.
A thermal responsive resistor 28 is connected to the gate of TRIAC 26 so as to switch on the TRI~C 26 at a predetermined low temperature level. When capacitor 27 is switched into the parallel circuit the overall capacitanca between leads 8 and 11 increa~es. TRIAC 26 turns off at zero ~urrent cros~ing, then switching capacitor 27 out o~ the parallel circuit. '~his cause~
the overall capacitance to decrease~ Thermistor 28 may be a well known thermal responsive switch such as a P~rc resistor.
The embodiment shown in FIG~ 6 shows power capacitor l9 connected in series with a second capacitor 29. An electronic switch, which is in this embodiment TRIAC 30, is connected across se~ond capacitor 29. A thermal responsive switch 31 is connected to the gate of TRIAC 300 When a predatermined temperature is sensed by thermal resistor ~witch 31 TRIAC 30 turns on. This e~fectively ~witches capacitor 29 out of the .. ~, . . .. . . .
;, :, ~, . : . . - , . .
~ 5~-~D-6227 1(~4~498 circuit. Other types of capaci-ty circuits may be utilized.
For example, the power capacitor alone may be utilized whereby the internal structure of the power capacitance is made so that its capacity increases as the temperature around it decreases.
A paper-askarel capacitor has been used in the prior art which undergoes, at the most, a 3~ decrease in capacitance for a temperature rise between 25 C and 70 C. This small change, however, was deemed insubstantial. This is, its effect on thermal regulation was insignificant.
la An askarel-filled polypropylene film dielectric capaci-tor has been developed which undergoes a seven or eight percent decrease in capacitance when the temperature around it goes from 25 C to 70 C. This film capacitor may be used as a power capacitor. While this drop in capacitance was helpful in decreasing the overall temperature of the ballast and lamp, it is further helpful in that a savings in materials for the ballast may be realized. If one is willing to leave the temperature at a fairly hiyh point, smaller than normal sized transformer wire may be used. Seemingly this would cause the 2Q temperature to in¢rease but it would be compensated or by the capacity circuit. Furthermore-, dif~erent types and less expensive core materials may be used which allow the ballast to heat up but again the capacity circuit would compensate for this temperature increase.
One of the most desirahle ranges for thermal regulation is a 15% to 2Q~ change in capacitance. With a 15% to 20% droop, a ballast operating with an undesirable 110 C case may be regulated back to 90-95 C ~Yithout a significant change in light output. Another one of the benefits of a 15% to 20% reduction in capacitance is that the ballast and lamp may be operated at least within 95 percent of its normal unre~ulated light output hetween 7Q C and 25 C ambient. This, again, takes advantage of the light output to temperature phenomena illu~trated in the graph shown ln FI~. 7 whereby the light output increaseY as the temperature decrease~ between 70 C and 25 C. It has been shown by tests on the various circuit~ shown in FIGS~ 2-6 that this 95 percent light output may be achieved in ~ome environments even though the capacitance has decreased between 15 and 20 percent.
The circuit shown in FIG. 1 and incorporating t~e spacific capacity circuit of FIG. 2 operates in the following manner: input power is received across terminals 1 and 2. Fila-ment winding 6, 14 and 15 are energized to pre-heat the lamp filaments. me voltage on primary winding 3 is ~tepped up acro s secondary winding 5 and, the primary winding. Starting capacitor 16 is charged through power capacitor 19 and gaseous discharge lamps 9 and lO (in this example fluorescent lamps~ are started. A current flows from input terminal l through secondary winding 5 and power capacitance l9 and further through the filaments of lamps 9 and 10 bacX to other side of prim~ry winding 3 and input terminal 2. As the ambient temperature around and i the balla~t and ~ixture begins to rise, thermistor 21, shown in FIG. 2, begi~s to show more resistance. This particular thermistor switches, i~e. 50 ohms at 25 C and 105 ohms at 100~ C. merefore capacitox 22 is switched out of electrical parallel with powex capacitor l9. The capacity circuit therefore has less capacitance between terminal~ 8 and ll at a high t2mperature than it does at a relatively low temperature~ This decrease in capacitance results in an increase in o~erall circuit impedance. Capacitance i~ related to impedance by the ~ormula Z - ~ . Since the impedance is increased, the current through the lamps and therefore the power di~sipated by the lamps is decreased. With less power being dissipated by the lamps the overall temperature in the fixture and near the ballast will begin to ~ecrease. Thi5 9~
combined decrea3e ln lamp power and decrease in ambiant temperature will allow the light output to remaln nearly constant. A~ the temperaturs decrea~es sufficiently, the thermistor 21 will ~ense that the temperature i8 decreasing and ~witch capacitor 22 bacX into the capacity circuit. Thi~
switching of capacitor 22 in or out of the capacity circuit results in the thermal regulation of the ballast circuit.
A circuit has been built with the components shown in FIGS. 1 and 2 having the following set of value3:
Capacitor 19 - 3.4 MFd Capacitor 22 - 0.4 MFd Capacitor 16 - O.05 MFd PTC Resistor 21 R25OC - 50 Ohms.
Rl0ooc - 105 Ohms .
Primary Winding 3 - 823T, dia~ .0169"
Secondary Winding 5 - 1442T, dia. .0164"
Filament Winding 6 - 28T, dia. .0169"
Filament Winding 14 - 28T, dia~ .0169"
Filament Winding 15 - 28T, diaO .0169"
Lamp 9 ~ 40W rapid start fluore cent Lamp 10 ~ 40W rapid start fluorescent From the foregoing description of the lllustrative embodiments of the invention, it will be apparent that many :: :
modification~ may be made therein. For example, varlous type~
~: of capacity circuits may be used.w~ereby the thermal character- .
istics of the ballast circuit are substantially regulated. It will be understood, therefore, that the e embodiments of the invention are intended as an exemplification of tha invention - 30 only and that this invention is not limited thereto. It is also understood, therefore, that it is intended in the appended claims to cover all modifications that fall within the true spirit and scope o* ~his invention.
Claims (14)
1. A ballast circuit for regulating the current in at least one gaseous discharge lamp over a range of ambient temperatures comprising:
a pair of input terminals for connecting said ballast circuit to a source of pOeIer;
a transformer having primary and secondary windings;
said pair of input terminals being connected to opposite ends of said primary winding;
means for connecting said ballast circuit to the at least one lamp;
a capacity circuit connected between said secondary winding of said transformer and said means for connecting said ballast circuit to the at least one lamp;
said capacity circuit including a power capacitance means;
said capacity circuit including means adapted to substantially decrease the effective capacitance of said capacity circuit in response to a predetermined increase in the temperature to which said ballast circuit is subjected and to substantially increase the effective capacitance of said capacity circuit in response to a predetermined decrease in the temperature to which said ballast circuit is subjected, whereby said ballast circuit is thermally regulated with no more than an insubstantial change in light output of the at least one lamp.
a pair of input terminals for connecting said ballast circuit to a source of pOeIer;
a transformer having primary and secondary windings;
said pair of input terminals being connected to opposite ends of said primary winding;
means for connecting said ballast circuit to the at least one lamp;
a capacity circuit connected between said secondary winding of said transformer and said means for connecting said ballast circuit to the at least one lamp;
said capacity circuit including a power capacitance means;
said capacity circuit including means adapted to substantially decrease the effective capacitance of said capacity circuit in response to a predetermined increase in the temperature to which said ballast circuit is subjected and to substantially increase the effective capacitance of said capacity circuit in response to a predetermined decrease in the temperature to which said ballast circuit is subjected, whereby said ballast circuit is thermally regulated with no more than an insubstantial change in light output of the at least one lamp.
2. A ballast circuit as set forth in claim 1 wherein said capacity circuit further includes a second capacitance means associated with said power capacitance means, and a switch means for effectively switching said second capacitance means in and out of an electrical relationship with said capacity circuit.
3. A ballast circuit as set forth in claim 2 wherein said switch means is a positive temperature coefficient resistor connected in series with said second capacitor;
said series arrangement being connected in parallel with said power capacitance means.
said series arrangement being connected in parallel with said power capacitance means.
4. A ballast circuit as set forth in claim 3 wherein said positive temperature coefficient resistor is substantially linear resistance with respect to temperature over a predeter-mined temperature range.
5. A ballast circuit as set forth in claim 3 wherein said positive temperature coefficient resistor is of the type which abruptly and substantially changes resistance at a predetermined temperature.
6. A ballast circuit as set forth in claim 2 wherein said switch means is a thermal responsive switch; said thermal responsive switch being connected in series with second capacitance means; said series arrangement being connected in parallel with said power capacitance means.
7. A ballast circuit as set forth in claim 6 wherein said thermal responsive switch is a bi-metal switch.
8. A ballast circuit as set forth in claim 2 wherein said switch means is an electronic switch having a control terminal; said electronic switch being connected in series with said second capacitance means; said series combination being connected in parallel with said power capacitance; a thermal responsive device connected to said control terminal of said electronic switch for controlling initiation of said electronic switch.
9. A ballast circuit as set forth in claim 2 wherein said switch means is an electronic switch having a control terminal; said second capacitance being connected in series with said power capacitance means; said electronic switch connected in parallel with said second capacitance means, and a thermal responsive device being connected to said control terminal of said electronic switch means for controlling initiation of said electronic switch.
10. A ballast circuit set forth in claim 1 wherein said capacity circuit includes a ceramic capacitor connected in parallel with said power capacitance means;
said ceramic capacitor being the type whose capacitance decreases as the temperature increases.
said ceramic capacitor being the type whose capacitance decreases as the temperature increases.
11. A ballast circuit as set forth in claim 1 wherein the change in overall capacitance of said capacity circuit is greater than 15% with a corresponding change in light output from the lamp of less than 5%.
12. A ballast circuit for regulating the current to at least one gaseous discharge lamp over a range of ambient temperatures comprising: a pair of input terminals for connecting said ballast circuit to a source of power;
a transformer having primary and secondary windings, said primary winding being connected to said pair of input terminals;
means for connecting said ballast circuit across the at least one lamp;
a power capacity circuit connected between said secondary winding of said transformer and said means for connecting said ballast circuit to the at least one lamp;
said power capacity circuit including means adapted to substantially change the effective capacitance of said power capacity circuit in response to a predetermined change in the temperature to which said ballast circuit is subjected for substantially changing the overall impedance of said ballast circuit so that said ballast circuit is thermally regulated with no more than an insubstantial change in light output of the at least one lamp.
a transformer having primary and secondary windings, said primary winding being connected to said pair of input terminals;
means for connecting said ballast circuit across the at least one lamp;
a power capacity circuit connected between said secondary winding of said transformer and said means for connecting said ballast circuit to the at least one lamp;
said power capacity circuit including means adapted to substantially change the effective capacitance of said power capacity circuit in response to a predetermined change in the temperature to which said ballast circuit is subjected for substantially changing the overall impedance of said ballast circuit so that said ballast circuit is thermally regulated with no more than an insubstantial change in light output of the at least one lamp.
13. A ballast circuit as set forth in claim 12 wherein the means for substantially changing the capacitance of said capacity circuit will cause at least a 15 percent change in capacitance in response to a predetermined change in tempera-ture.
14. A ballast circuit as set forth in claim 12 wherein said capacity circuit includes a thermal responsive switch means and a second capacitance means;
said second capacitance means associated with said thermal responsive switch means and said power capacitance means whereby said thermal responsive switch means controls the overall capacitance of said capacity circuit.
said second capacitance means associated with said thermal responsive switch means and said power capacitance means whereby said thermal responsive switch means controls the overall capacitance of said capacity circuit.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US41216773A | 1973-11-02 | 1973-11-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1042498A true CA1042498A (en) | 1978-11-14 |
Family
ID=23631873
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA211,094A Expired CA1042498A (en) | 1973-11-02 | 1974-10-09 | Thermal regulator ballast |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5078173A (en) |
| CA (1) | CA1042498A (en) |
| DE (1) | DE2451120A1 (en) |
| GB (1) | GB1485166A (en) |
| ZA (1) | ZA746373B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6316872B1 (en) | 1995-09-22 | 2001-11-13 | Gl Displays, Inc. | Cold cathode fluorescent lamp |
| US5834889A (en) | 1995-09-22 | 1998-11-10 | Gl Displays, Inc. | Cold cathode fluorescent display |
| US6201352B1 (en) | 1995-09-22 | 2001-03-13 | Gl Displays, Inc. | Cold cathode fluorescent display |
| CN1161819C (en) * | 1998-05-06 | 2004-08-11 | 泛海企业有限公司 | Cold cathode fluorescent lamp and display |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU3657078A (en) * | 1977-06-04 | 1979-12-06 | Hepworth Plastics Ltd | Pipe joint |
-
1974
- 1974-10-07 ZA ZA00746373A patent/ZA746373B/en unknown
- 1974-10-09 CA CA211,094A patent/CA1042498A/en not_active Expired
- 1974-10-28 DE DE19742451120 patent/DE2451120A1/en not_active Withdrawn
- 1974-10-30 GB GB47006/74A patent/GB1485166A/en not_active Expired
- 1974-11-01 JP JP49125568A patent/JPS5078173A/ja active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2451120A1 (en) | 1975-05-07 |
| ZA746373B (en) | 1975-10-29 |
| JPS5078173A (en) | 1975-06-25 |
| GB1485166A (en) | 1977-09-08 |
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