CA1130852A - Variable low frequency dimming for high intensity gaseous discharge lamps - Google Patents
Variable low frequency dimming for high intensity gaseous discharge lampsInfo
- Publication number
- CA1130852A CA1130852A CA330,874A CA330874A CA1130852A CA 1130852 A CA1130852 A CA 1130852A CA 330874 A CA330874 A CA 330874A CA 1130852 A CA1130852 A CA 1130852A
- Authority
- CA
- Canada
- Prior art keywords
- lamp
- voltage
- frequency
- ballast
- network
- 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
- H05B41/38—Controlling the intensity of light
- H05B41/39—Controlling the intensity of light continuously
Landscapes
- Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
VARIABLE LOW FREQUENCY DIMMING FOR
HIGH INTENSITY GASEOUS DISCHARGE LAMPS
ABSTRACT OF THE DISCLOSURE
A dimming network for an HID lamp and ballast including a variable frequency generator for increasing the impedance of a primarily inductive ballast connected to the lamp and thereby reducing the current therethrough for the same applied voltage level.
HIGH INTENSITY GASEOUS DISCHARGE LAMPS
ABSTRACT OF THE DISCLOSURE
A dimming network for an HID lamp and ballast including a variable frequency generator for increasing the impedance of a primarily inductive ballast connected to the lamp and thereby reducing the current therethrough for the same applied voltage level.
Description
~3~\85Z
BACKGROUND OF THE INVENTION
_ Field of the Invention This invention pertains to lamp dimming and more parti-cularly to providing HID lamps with lamp dimming control without having to provide existing or conventional lamp-and-ballast networks with additional wiring or components.
Description of the Prior Art It has been discovered that providing HID lamps with less than rated current, but at the same voltage level, such lamps can operate very efficiently at lower light intensity than their rated value. It is desirable, for instance, to be able to turn down HID lamps in areas that are little used. Turning off the lamps in such areas is often undesir-able because having more than ambient light is frequently preferred to having no light at all. Furthermore, if the lamps were completely turned off, a relatively long warm-up time is required to bring the lamps back to full illumination.
Examples of such use include a warehouse installation, a parking lot installation, a tennis court installation after hours of regular use, and a street lighting installa-tion at late hours when there are virtually no automobiles on the road.
Heretofore, it has been common to provide dimming by having a ballast capable of at least partial current bypass operation. When less than full current goes through the lamp, because some of the current is bypassed around a portion of the ballast reactor, then the lamp dims. The amount of current bypass controls the amount of dimming.
The usual method or technique of providing this bypass is to utilize a ballast having at least two separate inductors :113~8S2 and to connect a yated semiconductor device, such as a gated triac, around one of them~ The gating of the triac determines the degree of bypass, and hence the amount of lamp current.
Many devices may be used to gate the bypass semiconductor.
Some of these devices use separate wiring to the semiconductor.
Others use superimposed signals to perform the gating. But, in both instances there is a requirement to add to the existing installation, either in the form of additional wiring, additional electronic components, or both.
Therefore, it i~ a fea~ure of the present invention to provide improved dimming of an HID lamp by a control system utilizing the same ballast components, same wiring and same voltage source used in a lamp network not having dimming as a part thereof.
It i8 another featur~ of the present invention to provide improve~ dimmlng of an HID lamp already installed wlthout dlmming provl~lon wlthout having to add additional oompon~nto or wlrlng to tho ~n~tallation.
SUMMARY OF THE INVF.NTION
_ In one broad aspect, the invention comprehends a dimmer circuit for controlling the amount of current through an HID lamp. The circuit includes variable frequency means for producing an ac voltage at substantially , ~'`' ~13~85Z
constant amplitude and variable in frequency, which variable frequency means includes a network for producing a square-wave, ac voltage, and ballast means connected to -the variable frequency means and to the lamp. The ballast means is primarily inductive, and a voltage from the variable frequency means at a frequency greater than power line frequency increases the effective impedance of the bàllas-t means, and thereby reduces the effective current through the lamp compared with the application of the same voltage level at power line frequency.
In a preferred embodiment of the invention a variable frequency generator i~ uged to provide power at a constant voltage level and over a frequency range from about 60 Hz to 180 Hz. One convenien~ generator inclu(ies a switching network for selectively providing first a positive voltage value and then a comparable negative voltage value, the resulting waveform being a square wave.
Following amplification, the variable frequency voltage is applied to a lamp-and-halla~t network having a primarily inductive component. A~ the frequency is increased, the ~3C)8~i2 current is decreased, for the same applied voltage level, and, therefore, the lamp of the network is di~ ecl.
BRIEF DESCRIPTION OF TIII~ DRAWINGS
So that the manner in which the above-recited features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be under-stood in detail, more particular description of the invention briefly summarized above may b~ had by reference to the embodiments thereof which are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawing~ illustrate only typical embodiments of the invention and are therefore not to be ~onslderod limiting of its scope, for the invention may admit to other equally effective embodiments.
In ths Drawing~:
Fig. 1 is a ~impl~ied block diagram of a preferred embodiment of the pres~nt invention.
Fig. 2 is a simplified schemat~c diagram of one inductive ballast-and-lamp network in accordance with the pre~ent invention.
Fig. 3 i~ a ~implified schematic diagram of a second inductive ballast-and-lamp network in accordance with the present invention.
Fig. 4 is a simplified schematic diagram of a variable frequency, square-wave generator in accordance with the present invention.
Fiq. 5 is a simpli~ied block and schematic diagram of a switchi~g network ~e~ul in th~ network shown in Fig. 4~
I)ESCRIPTION OF PR13FEFlREl:) FMBODIMEN'l`S
____ .
Now referring to the drawin~s and first to Fic~. 1, a dimming circuit is shown in accordance with the present invention. Lamp 10 is connected to a ballast network 12 comprising both an inductive and a capacitive component for operational purposes not involved directly wi~h this invention, as is well known in the art. ~he drive voltage which is normally applied to the network is the power line voltage at a nominal 60 Hz~ In the circuit shown, power is provided from variable frequency generator 14 including a square-wave voltage forming network 16 for reasons hereafter explained.
The output from generator 14 is applied to a voltage amplifier 18 to produce an output level suitable for powering the lamp~and-ballast network.
In operation, the output from variable frequency generator 14 o~n be beRt under~tood as being irst at a predetermined level applled to the lamp-and-ballast network at a nominal 60 Hz. The lamp and balla6t components present a complex inductive load under quiescent operating conditions that establish a nominal full brightness current. When the variable frequency generator is adjusted to increase the frequency, the voltage level remaining the same, then the inductive load becomes greater and, hence, the current becomes Qmaller. In notational language, E=IZ, wherein E
equals the applied voltage level; I equals the current through the lamp and inductive ballast; and Z equals the impedance of the total load. The inductive component of impedance can be further represented by j2~fL, wherein j indicate~ that this component i~ 90 degrees out of phase from the resistance component; 2~ and L are constants for a given inductor; and f eguals frequency. Hence, when E
remains constant and f is increased, I then decreases.
decreasing current through lamp 10 reduces th~ light intellsity therefrom. Ilence, an increase in fre(3~ ncy r~snlts in dimming of the lamp.
Two possible arrangements of all inductive load in coln-bination with lamp 10 are shown in l`i(Js. 2 and 3. In each case inductor 20 is in series with the lamp. In I`i(~. 2, capacitor 22 is in series with inductor 20 and lamp 10. In Fig. 3, capacitor 24 is connected across lamp 10.
Fig. 4 is a simplified schematic diagram of a network suitable for development of a square-wave signal for operatiny in accordance with the present invention. The applied line voltage at 60 Hz is applied to bridye 32, which is illustrated in simplified form. The output thereErom for the operation of a typical HID lamp network is a resultant 400-600 dc voltage, capacitor 34 acting as a filter component for the bridge output.
A capacitor divider aomprising identical capacitors 36 and 38 (which alternately can be equalized or balanced) establishes a mid-point 37 therebetween at zero vclts.
Theae capacitors have low impedance values for all operatiny frequencies of interest and provide low impedance buffering with regard to voltage changes. Switches 40 and 42 are electronic switches which open and close in alternate fashion to first present an output of first polarity at terminal 39 with respect to the zero-volt terminal 37 and then an output of second polarity with respect thereto~ If the total dc level is 600 volts, then the peak of each polarity would be 300 volts~ The switching rate of switches 40 and 42 determines the frequency of the square wave output.
Additional low pass filters can be provided to filter out high frequency harmonics, switching transients and the like, since the cirGuit is frequency sensitive. The pro-duction of a square wave 1n the manner described eliminates ~3~8S2 the effect of line distortions and other superimpeded high frequencies that may be included on the power line. Alternative to the two-transistor switch network is a fu11 bridge.
Fi~. 5 illustrates a network suitable for operating ~s the electronic switching network of Flg. 4 just described.
It is understood, of course, tha-t t:he Fig. 4 network illustrates a preferred embodiment only; however, there are many alternate circuits of establishing a square wave voltage. This network includes a multivibrator 50 having two alternately produced output pulses, one of which is connected to the base of npn transistor 52 and the other of which is connected to the base of npn transistor 54. These two transistors are connected so that the emitter of transistor 52 is connec~ed to the collector of transistor 54.
Diode 56 ls connected across the collector-emitter of tran8istox 52 and diode 58 is connected across the collector-emittor of tran~i~tor 54. ~he collector of transistor 52 is connected to a positive bia~ voltage and th~ emitter of transistor 54 ~s connected to a negative bias. The output i8 connected to the junction between the diodes. Alternate conduction to saturation of transistors 52 and 54 causes the creation of the square-wave output previously described.
It is`readily apparent that although the description of the exemplary network has been with respect to the develop-ment of a square-wave voltage, a variable frequency voltage of any other configuration maintaining a predetermined rms level would satisfactorily operate in the manner just described. A square wave is readily generated and variable and hence its selection in the preferred embodiment. For example, a pulse width modulator may readily be used to change the nominal sine wave of the power line to a suitable square wave.
Moreover, the discussion of the preferred embvdiment indicates a preference for e primarily inductive ballast and 113~85Z
operating from a full bright 60 ~Iz fr(clu~ncy to ~ hi(~her frequency, where "full dim" operation occurs. 'I'he 60 llz frequency would be a fre~uency above thc reson.ln~ fre(luenc~y for the LC circuit (where the lamp current would be greatest:) and a relatively large capacitor would be errlployed. As t~e frequency is increased, operation would be further away from the resonant peak current. A full dim current is typically about one-third of a full bright current, so the full dim frequency would be about 180 Hz.
However, ~he same principle would apply to any frequellcy range of operation, 60 Hz only being selected for discussion purposes because of convenience. When the circuit operates with respect to higher ~requencies, however, the components are smaller in size. If operating in the kHz range, it is better to operate above the acoustic frequency range for the lamp(s) to ensure ~table, and apparent noise-free operation.
An autotransformer connection can also be connected in con~unction with capacitor 24 and provides ready connection for higher open circuit voltage ~or startin~ purposes or for operating metal halide HI~ lamps.
The same principles discussed above would also apply to a primarily capacitive ballast connection. This would be because operation would be with respect to operating frequencies below the resonant frequency for the LC circuit. A 60 Hz frequency would be farther away than a 180 Hz frequency in this case. Or, as the frequency increases, operation is more and more toward the peak, hence achieving brighter operation. A relatively small capacitor is used in this case.
It is not practical to h~ve the operating current below 60 Hz since to go much lower than that would cause a visible flicker condition and even shut-off of ~he lamp.
~3(~35Z
Therefore, for a primarily capacitive ~allast, it would be advisable to select the component values such th~t full bright operation is at a voltage oper.ltion apE~lied at a frequency of 180 Hz and full dim operation is at a voltage operation applied at a frequency oï 60 Hz, assuming that the resonant frequency for the circuit is greater than 180 Hz.
Other frequency selections can be made operating in accordance with the principles just discussed.
Although inductive and capacitive ballast arrangements have been discussed above, it is apparent that any type of reactive type ballast can be used. For example, a lead peak regulating ballast is a popular type of ballast with which the present invention is useful.
One primary advantage of the present dimrning system just described over dimmlng systems in the prior art is that dimminy control can be provided without additional wiring to the lamp-and-ballast or lamp structure for the sole purpose of accommodating to providing lamp dimming. This means that existlng lamps can be readily provided lamp dimming by merely disconnecting the power factor capacitors to prevent a load from being connected across the switching transistors and by modifying the voltage devel~pment networ~ applying the power to the lamp or lamps in the manner discussed.
While particular embodiments of the invention have been shown, it will be understood that the invention is not limited thereto, since many modifications may be made. One example is that variable frequency generator 14 does not have to be set manually to achieve dimming, but may be part of an automated system. For example, it may be desirable to dim street lights when no automobiles are being sensed along a particular stretch of road~ A sensor network could provide the variable frequency voltage for effecting dimming and a return to full brightne~ when an approaching vehicle is ,~
113(~852 sensed. Moreover, the above discussion has beell with reg~rd HID lighting. Similar operation of fluorescent lamps, incandescent l.amp~ and LPS lamps can be provided. Ot.her modificati.ons also may be made and will. become apparent to those skilled in the art~
~,,.
BACKGROUND OF THE INVENTION
_ Field of the Invention This invention pertains to lamp dimming and more parti-cularly to providing HID lamps with lamp dimming control without having to provide existing or conventional lamp-and-ballast networks with additional wiring or components.
Description of the Prior Art It has been discovered that providing HID lamps with less than rated current, but at the same voltage level, such lamps can operate very efficiently at lower light intensity than their rated value. It is desirable, for instance, to be able to turn down HID lamps in areas that are little used. Turning off the lamps in such areas is often undesir-able because having more than ambient light is frequently preferred to having no light at all. Furthermore, if the lamps were completely turned off, a relatively long warm-up time is required to bring the lamps back to full illumination.
Examples of such use include a warehouse installation, a parking lot installation, a tennis court installation after hours of regular use, and a street lighting installa-tion at late hours when there are virtually no automobiles on the road.
Heretofore, it has been common to provide dimming by having a ballast capable of at least partial current bypass operation. When less than full current goes through the lamp, because some of the current is bypassed around a portion of the ballast reactor, then the lamp dims. The amount of current bypass controls the amount of dimming.
The usual method or technique of providing this bypass is to utilize a ballast having at least two separate inductors :113~8S2 and to connect a yated semiconductor device, such as a gated triac, around one of them~ The gating of the triac determines the degree of bypass, and hence the amount of lamp current.
Many devices may be used to gate the bypass semiconductor.
Some of these devices use separate wiring to the semiconductor.
Others use superimposed signals to perform the gating. But, in both instances there is a requirement to add to the existing installation, either in the form of additional wiring, additional electronic components, or both.
Therefore, it i~ a fea~ure of the present invention to provide improved dimming of an HID lamp by a control system utilizing the same ballast components, same wiring and same voltage source used in a lamp network not having dimming as a part thereof.
It i8 another featur~ of the present invention to provide improve~ dimmlng of an HID lamp already installed wlthout dlmming provl~lon wlthout having to add additional oompon~nto or wlrlng to tho ~n~tallation.
SUMMARY OF THE INVF.NTION
_ In one broad aspect, the invention comprehends a dimmer circuit for controlling the amount of current through an HID lamp. The circuit includes variable frequency means for producing an ac voltage at substantially , ~'`' ~13~85Z
constant amplitude and variable in frequency, which variable frequency means includes a network for producing a square-wave, ac voltage, and ballast means connected to -the variable frequency means and to the lamp. The ballast means is primarily inductive, and a voltage from the variable frequency means at a frequency greater than power line frequency increases the effective impedance of the bàllas-t means, and thereby reduces the effective current through the lamp compared with the application of the same voltage level at power line frequency.
In a preferred embodiment of the invention a variable frequency generator i~ uged to provide power at a constant voltage level and over a frequency range from about 60 Hz to 180 Hz. One convenien~ generator inclu(ies a switching network for selectively providing first a positive voltage value and then a comparable negative voltage value, the resulting waveform being a square wave.
Following amplification, the variable frequency voltage is applied to a lamp-and-halla~t network having a primarily inductive component. A~ the frequency is increased, the ~3C)8~i2 current is decreased, for the same applied voltage level, and, therefore, the lamp of the network is di~ ecl.
BRIEF DESCRIPTION OF TIII~ DRAWINGS
So that the manner in which the above-recited features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be under-stood in detail, more particular description of the invention briefly summarized above may b~ had by reference to the embodiments thereof which are illustrated in the drawings, which drawings form a part of this specification. It is to be noted, however, that the appended drawing~ illustrate only typical embodiments of the invention and are therefore not to be ~onslderod limiting of its scope, for the invention may admit to other equally effective embodiments.
In ths Drawing~:
Fig. 1 is a ~impl~ied block diagram of a preferred embodiment of the pres~nt invention.
Fig. 2 is a simplified schemat~c diagram of one inductive ballast-and-lamp network in accordance with the pre~ent invention.
Fig. 3 i~ a ~implified schematic diagram of a second inductive ballast-and-lamp network in accordance with the present invention.
Fig. 4 is a simplified schematic diagram of a variable frequency, square-wave generator in accordance with the present invention.
Fiq. 5 is a simpli~ied block and schematic diagram of a switchi~g network ~e~ul in th~ network shown in Fig. 4~
I)ESCRIPTION OF PR13FEFlREl:) FMBODIMEN'l`S
____ .
Now referring to the drawin~s and first to Fic~. 1, a dimming circuit is shown in accordance with the present invention. Lamp 10 is connected to a ballast network 12 comprising both an inductive and a capacitive component for operational purposes not involved directly wi~h this invention, as is well known in the art. ~he drive voltage which is normally applied to the network is the power line voltage at a nominal 60 Hz~ In the circuit shown, power is provided from variable frequency generator 14 including a square-wave voltage forming network 16 for reasons hereafter explained.
The output from generator 14 is applied to a voltage amplifier 18 to produce an output level suitable for powering the lamp~and-ballast network.
In operation, the output from variable frequency generator 14 o~n be beRt under~tood as being irst at a predetermined level applled to the lamp-and-ballast network at a nominal 60 Hz. The lamp and balla6t components present a complex inductive load under quiescent operating conditions that establish a nominal full brightness current. When the variable frequency generator is adjusted to increase the frequency, the voltage level remaining the same, then the inductive load becomes greater and, hence, the current becomes Qmaller. In notational language, E=IZ, wherein E
equals the applied voltage level; I equals the current through the lamp and inductive ballast; and Z equals the impedance of the total load. The inductive component of impedance can be further represented by j2~fL, wherein j indicate~ that this component i~ 90 degrees out of phase from the resistance component; 2~ and L are constants for a given inductor; and f eguals frequency. Hence, when E
remains constant and f is increased, I then decreases.
decreasing current through lamp 10 reduces th~ light intellsity therefrom. Ilence, an increase in fre(3~ ncy r~snlts in dimming of the lamp.
Two possible arrangements of all inductive load in coln-bination with lamp 10 are shown in l`i(Js. 2 and 3. In each case inductor 20 is in series with the lamp. In I`i(~. 2, capacitor 22 is in series with inductor 20 and lamp 10. In Fig. 3, capacitor 24 is connected across lamp 10.
Fig. 4 is a simplified schematic diagram of a network suitable for development of a square-wave signal for operatiny in accordance with the present invention. The applied line voltage at 60 Hz is applied to bridye 32, which is illustrated in simplified form. The output thereErom for the operation of a typical HID lamp network is a resultant 400-600 dc voltage, capacitor 34 acting as a filter component for the bridge output.
A capacitor divider aomprising identical capacitors 36 and 38 (which alternately can be equalized or balanced) establishes a mid-point 37 therebetween at zero vclts.
Theae capacitors have low impedance values for all operatiny frequencies of interest and provide low impedance buffering with regard to voltage changes. Switches 40 and 42 are electronic switches which open and close in alternate fashion to first present an output of first polarity at terminal 39 with respect to the zero-volt terminal 37 and then an output of second polarity with respect thereto~ If the total dc level is 600 volts, then the peak of each polarity would be 300 volts~ The switching rate of switches 40 and 42 determines the frequency of the square wave output.
Additional low pass filters can be provided to filter out high frequency harmonics, switching transients and the like, since the cirGuit is frequency sensitive. The pro-duction of a square wave 1n the manner described eliminates ~3~8S2 the effect of line distortions and other superimpeded high frequencies that may be included on the power line. Alternative to the two-transistor switch network is a fu11 bridge.
Fi~. 5 illustrates a network suitable for operating ~s the electronic switching network of Flg. 4 just described.
It is understood, of course, tha-t t:he Fig. 4 network illustrates a preferred embodiment only; however, there are many alternate circuits of establishing a square wave voltage. This network includes a multivibrator 50 having two alternately produced output pulses, one of which is connected to the base of npn transistor 52 and the other of which is connected to the base of npn transistor 54. These two transistors are connected so that the emitter of transistor 52 is connec~ed to the collector of transistor 54.
Diode 56 ls connected across the collector-emitter of tran8istox 52 and diode 58 is connected across the collector-emittor of tran~i~tor 54. ~he collector of transistor 52 is connected to a positive bia~ voltage and th~ emitter of transistor 54 ~s connected to a negative bias. The output i8 connected to the junction between the diodes. Alternate conduction to saturation of transistors 52 and 54 causes the creation of the square-wave output previously described.
It is`readily apparent that although the description of the exemplary network has been with respect to the develop-ment of a square-wave voltage, a variable frequency voltage of any other configuration maintaining a predetermined rms level would satisfactorily operate in the manner just described. A square wave is readily generated and variable and hence its selection in the preferred embodiment. For example, a pulse width modulator may readily be used to change the nominal sine wave of the power line to a suitable square wave.
Moreover, the discussion of the preferred embvdiment indicates a preference for e primarily inductive ballast and 113~85Z
operating from a full bright 60 ~Iz fr(clu~ncy to ~ hi(~her frequency, where "full dim" operation occurs. 'I'he 60 llz frequency would be a fre~uency above thc reson.ln~ fre(luenc~y for the LC circuit (where the lamp current would be greatest:) and a relatively large capacitor would be errlployed. As t~e frequency is increased, operation would be further away from the resonant peak current. A full dim current is typically about one-third of a full bright current, so the full dim frequency would be about 180 Hz.
However, ~he same principle would apply to any frequellcy range of operation, 60 Hz only being selected for discussion purposes because of convenience. When the circuit operates with respect to higher ~requencies, however, the components are smaller in size. If operating in the kHz range, it is better to operate above the acoustic frequency range for the lamp(s) to ensure ~table, and apparent noise-free operation.
An autotransformer connection can also be connected in con~unction with capacitor 24 and provides ready connection for higher open circuit voltage ~or startin~ purposes or for operating metal halide HI~ lamps.
The same principles discussed above would also apply to a primarily capacitive ballast connection. This would be because operation would be with respect to operating frequencies below the resonant frequency for the LC circuit. A 60 Hz frequency would be farther away than a 180 Hz frequency in this case. Or, as the frequency increases, operation is more and more toward the peak, hence achieving brighter operation. A relatively small capacitor is used in this case.
It is not practical to h~ve the operating current below 60 Hz since to go much lower than that would cause a visible flicker condition and even shut-off of ~he lamp.
~3(~35Z
Therefore, for a primarily capacitive ~allast, it would be advisable to select the component values such th~t full bright operation is at a voltage oper.ltion apE~lied at a frequency of 180 Hz and full dim operation is at a voltage operation applied at a frequency oï 60 Hz, assuming that the resonant frequency for the circuit is greater than 180 Hz.
Other frequency selections can be made operating in accordance with the principles just discussed.
Although inductive and capacitive ballast arrangements have been discussed above, it is apparent that any type of reactive type ballast can be used. For example, a lead peak regulating ballast is a popular type of ballast with which the present invention is useful.
One primary advantage of the present dimrning system just described over dimmlng systems in the prior art is that dimminy control can be provided without additional wiring to the lamp-and-ballast or lamp structure for the sole purpose of accommodating to providing lamp dimming. This means that existlng lamps can be readily provided lamp dimming by merely disconnecting the power factor capacitors to prevent a load from being connected across the switching transistors and by modifying the voltage devel~pment networ~ applying the power to the lamp or lamps in the manner discussed.
While particular embodiments of the invention have been shown, it will be understood that the invention is not limited thereto, since many modifications may be made. One example is that variable frequency generator 14 does not have to be set manually to achieve dimming, but may be part of an automated system. For example, it may be desirable to dim street lights when no automobiles are being sensed along a particular stretch of road~ A sensor network could provide the variable frequency voltage for effecting dimming and a return to full brightne~ when an approaching vehicle is ,~
113(~852 sensed. Moreover, the above discussion has beell with reg~rd HID lighting. Similar operation of fluorescent lamps, incandescent l.amp~ and LPS lamps can be provided. Ot.her modificati.ons also may be made and will. become apparent to those skilled in the art~
~,,.
Claims (5)
1. A dimmer circuit for controlli.ng the amount of current through an HID lamp, comprisiny variable frequency means for producing an ac voltage at substantially constant amplitude and variable in frequency, said variable frequency means including a network for producing a square-wave, ac voltage, and ballast means connected to said variable frequency means and to the lamp, said ballast means being primarily inductive, a voltage from said variable frequency means at a frequency greater than power line frequency increasing the effective impedance of said ballast means, thereby reducing the effective current through the lamp compared with the application of the same voltage level at power line frequency.
2 . A dimmer circuit in accordance with Claim 1, wherein said square-wave production network includes a rectifier for changing applied ac line voltage to a dc voltage, electronic switch means connected to said rectifier for switching the output therefrom between a negative and positive level to produce said square-wave, ac voltage.
3. A dimmer circuit in accordance with Claim 1, wherein said ballast means includes a low impedance in series with the lamp.
4. A dimmer circuit in accordance with Claim 3, wherein said ballast means includes a large capacitor in series with said lamp.
5. A dimmer circuit in accordance with Claim 4, wherein said ballast means includes a small capacitor across said lamp.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US93688278A | 1978-08-25 | 1978-08-25 | |
| US936,882 | 1978-08-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1130852A true CA1130852A (en) | 1982-08-31 |
Family
ID=25469192
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA330,874A Expired CA1130852A (en) | 1978-08-25 | 1979-06-29 | Variable low frequency dimming for high intensity gaseous discharge lamps |
Country Status (9)
| Country | Link |
|---|---|
| AU (1) | AU526724B2 (en) |
| BE (1) | BE878227A (en) |
| CA (1) | CA1130852A (en) |
| DE (1) | DE2931794A1 (en) |
| ES (1) | ES483620A1 (en) |
| FR (1) | FR2434547A1 (en) |
| GB (1) | GB2029134B (en) |
| IT (1) | IT1117392B (en) |
| MX (1) | MX147513A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ZA83299B (en) * | 1982-01-15 | 1983-10-26 | Minitronics Pty Ltd | Electronic high frequency controlled device for operating gas discharge lamps |
| US4843627A (en) * | 1986-08-05 | 1989-06-27 | Stebbins Russell T | Circuit and method for providing a light energy response to an event in real time |
| DE19708187A1 (en) * | 1997-02-28 | 1998-09-03 | Uwe Unterwasser Electric Gmbh | Lamp circuit control |
| GB2477507A (en) * | 2010-02-03 | 2011-08-10 | Emil Blumer | Control of luminance of gas discharge lamp using variable frequency drive |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB720279A (en) * | 1951-08-09 | 1954-12-15 | Gen Electric Co Ltd | Improvements in or relating to circuits for operating electric discharge lamps |
| GB955656A (en) * | 1959-05-19 | 1964-04-15 | A E I Lamp And Lighting Compan | Operation of electric discharge lamps |
| US3836815A (en) * | 1972-05-24 | 1974-09-17 | Gen Electric | Emergency instant-start lighting system for arc discharge devices |
-
1979
- 1979-06-29 CA CA330,874A patent/CA1130852A/en not_active Expired
- 1979-07-09 GB GB7923899A patent/GB2029134B/en not_active Expired
- 1979-07-13 IT IT49748/79A patent/IT1117392B/en active
- 1979-08-04 DE DE19792931794 patent/DE2931794A1/en not_active Withdrawn
- 1979-08-13 BE BE0/196720A patent/BE878227A/en not_active IP Right Cessation
- 1979-08-17 FR FR7921310A patent/FR2434547A1/en active Pending
- 1979-08-20 AU AU50089/79A patent/AU526724B2/en not_active Withdrawn - After Issue
- 1979-08-23 MX MX179037A patent/MX147513A/en unknown
- 1979-08-24 ES ES483620A patent/ES483620A1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| IT1117392B (en) | 1986-02-17 |
| ES483620A1 (en) | 1980-04-01 |
| DE2931794A1 (en) | 1980-03-06 |
| FR2434547A1 (en) | 1980-03-21 |
| MX147513A (en) | 1982-12-10 |
| IT7949748A0 (en) | 1979-07-13 |
| BE878227A (en) | 1979-12-03 |
| GB2029134A (en) | 1980-03-12 |
| AU5008979A (en) | 1980-02-28 |
| GB2029134B (en) | 1982-11-03 |
| AU526724B2 (en) | 1983-01-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |