CA1135423A - Starting circuit for gaseous discharge lamps - Google Patents
Starting circuit for gaseous discharge lampsInfo
- Publication number
- CA1135423A CA1135423A CA000353506A CA353506A CA1135423A CA 1135423 A CA1135423 A CA 1135423A CA 000353506 A CA000353506 A CA 000353506A CA 353506 A CA353506 A CA 353506A CA 1135423 A CA1135423 A CA 1135423A
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- circuit
- voltage
- diode
- ballast
- lamp
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Abstract
STARTING CIRCUIT FOR GASEOUS DISCHARGE LAMPS
Abstract of the Disclosure A starting circuit suitable for sodium vapor street lamps is disclosed. The circuit includes a voltage doubler which periodically fires pulses through the lamp ballast. The pulsing is controlled by a neon lamp con-nected to a gate anode of a triac. When the triac fires the capacitors which form the voltage doubler are shorted across to produce the starting pulse.
Abstract of the Disclosure A starting circuit suitable for sodium vapor street lamps is disclosed. The circuit includes a voltage doubler which periodically fires pulses through the lamp ballast. The pulsing is controlled by a neon lamp con-nected to a gate anode of a triac. When the triac fires the capacitors which form the voltage doubler are shorted across to produce the starting pulse.
Description
~ ~ ~ 5~ ~ 3 j Background of the Invention This invention relates to the field of lamp starting circuits. More particularly, it relates to circuits designed for initiating operation of gaseous discharge lamps such as the sodium vapor type commonly employed for street lighting.
Such lamps require high voltage starting pulses in order to initiate the ionization process. Subsequent operation of the lamps is maintained by a large ballast connected in series with the AC voltage source.
Lamp starting circuits are known in the art and see, for example, the patents discussed in the prior art statement which ~ollows. A principal drawback of the prior art is the inability of these designs to ~rot:ect the starting circuit from premature failure where the lamp or power factor capaci-tor fails. Under those conditions the starting circuit repea~edly fires in an effort to light the lamp and in many cases this causes overheating of the starting circuit lead-ing to premature component failure.
I Another disadvantage of the existing circuits is
Such lamps require high voltage starting pulses in order to initiate the ionization process. Subsequent operation of the lamps is maintained by a large ballast connected in series with the AC voltage source.
Lamp starting circuits are known in the art and see, for example, the patents discussed in the prior art statement which ~ollows. A principal drawback of the prior art is the inability of these designs to ~rot:ect the starting circuit from premature failure where the lamp or power factor capaci-tor fails. Under those conditions the starting circuit repea~edly fires in an effort to light the lamp and in many cases this causes overheating of the starting circuit lead-ing to premature component failure.
I Another disadvantage of the existing circuits is
2~ that in order to prevent current flow through the trigger circuit isolation comPonentS are required as, for example, the use of an inductance which has a high impedance at the pulse frequency. Also, presently available circuits do not provide means whereby a service technician can rapidly check and service a lamp which is not properly operating. Instead, the technician must check each component of the operating circuit, the starting circuit and the lamp until he determines the source of the problem. It would be desirable to provide a starting circuit which includes indicator means permitting
3 the technician to rapidly determine the source oi a lamp ~L35~L23 failure thereby to quickly affect repair or replacement.
It is accordingly an object of an aspect of the present invention to provide an improved lamp starting circuit in which the starting circuit components are not subject to premature failure in the event that the lamp or an associated component fails thereby inducing repeated starting pulses.
An object of an aspect of the invention is to provide an improved starting circuit in which current does not pass through the circuit after the starting pulse has been produced until the circuit resets itself and is ready to begin recharging.
An object of an aspect of the invention is to provide a starting circuit embodiment in which high impe-dance isolating components are not required to protect thecircuit against the high voltage pulses produced.
An object of an aspect of the invention is to provide a starting circuit which includes indicator means permitting a technician to rapidly determine whether the starting circuit is performing satisfactorily or is defec-tive.
In accordance with one aspect of this invention there is provided a starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between a voltage supply and said lamp, said starting circuit comprising: (a) a voltage doubler circuit con-nected in circuit with said ballast and said lamp for storing a voltage approximately twice the peak value of the voltage supply when said lamp is nonconducting, said volt-age douhler including: (i) a first circuit arm having acapacitor and diode in series, said diode conducting in a ~L35~;~3 first direction, (ii) a second circuit arm having a capa-citor and diode in series, said diode conducting in the opposite direction to the first diode, (iii) sald first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, whereby one of said capacitors will charge to the value of said voltage supply during each half cycle of the AC supply voltage, (b) trigger means connected in shorting relation across said voltage doubler for selec-1~ tively discharging the charge stored in said doublercircuit through a portion of said ballast to produce a high voltage starting pulse to initiate conduction in said lamp.
In accordance with another aspect of this inven-tion there is provided a starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between said lamp and a voltage supply, said circuit comprising: (a) a voltage doubling circuit includ-ing: (i) a first circuit arm having a capacitor and diode in series, said diode conducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode conducting in the opposite direction to the first diode, said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, (b) trigger means for discharging said doubler circuit through a portion of said ballast to produce a high voltage starting pulse connected to the mid-point of the capacitor and diode in each of said first and second circuit arms, and triggering is effective for sho~ting the mid-points together to place said capaci-tors in series to produce said high voltage pulse through said ballast.
-2a-1~35~:3 Other objects and advantages of the invention will be apparent from the remaining portion of the specification.
Prior Art Statement The closest prior art patents of which applicant is aware are: U.S. Patent No. 3,917,976 to Nuckolls, UO S.
Patent No. 3,976,910 to Owens et al, U. S. Patent No.
It is accordingly an object of an aspect of the present invention to provide an improved lamp starting circuit in which the starting circuit components are not subject to premature failure in the event that the lamp or an associated component fails thereby inducing repeated starting pulses.
An object of an aspect of the invention is to provide an improved starting circuit in which current does not pass through the circuit after the starting pulse has been produced until the circuit resets itself and is ready to begin recharging.
An object of an aspect of the invention is to provide a starting circuit embodiment in which high impe-dance isolating components are not required to protect thecircuit against the high voltage pulses produced.
An object of an aspect of the invention is to provide a starting circuit which includes indicator means permitting a technician to rapidly determine whether the starting circuit is performing satisfactorily or is defec-tive.
In accordance with one aspect of this invention there is provided a starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between a voltage supply and said lamp, said starting circuit comprising: (a) a voltage doubler circuit con-nected in circuit with said ballast and said lamp for storing a voltage approximately twice the peak value of the voltage supply when said lamp is nonconducting, said volt-age douhler including: (i) a first circuit arm having acapacitor and diode in series, said diode conducting in a ~L35~;~3 first direction, (ii) a second circuit arm having a capa-citor and diode in series, said diode conducting in the opposite direction to the first diode, (iii) sald first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, whereby one of said capacitors will charge to the value of said voltage supply during each half cycle of the AC supply voltage, (b) trigger means connected in shorting relation across said voltage doubler for selec-1~ tively discharging the charge stored in said doublercircuit through a portion of said ballast to produce a high voltage starting pulse to initiate conduction in said lamp.
In accordance with another aspect of this inven-tion there is provided a starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between said lamp and a voltage supply, said circuit comprising: (a) a voltage doubling circuit includ-ing: (i) a first circuit arm having a capacitor and diode in series, said diode conducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode conducting in the opposite direction to the first diode, said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, (b) trigger means for discharging said doubler circuit through a portion of said ballast to produce a high voltage starting pulse connected to the mid-point of the capacitor and diode in each of said first and second circuit arms, and triggering is effective for sho~ting the mid-points together to place said capaci-tors in series to produce said high voltage pulse through said ballast.
-2a-1~35~:3 Other objects and advantages of the invention will be apparent from the remaining portion of the specification.
Prior Art Statement The closest prior art patents of which applicant is aware are: U.S. Patent No. 3,917,976 to Nuckolls, UO S.
Patent No. 3,976,910 to Owens et al, U. S. Patent No.
4,072,878 to Engel et al, and U. S. Patent No. 3,889,152 to Bodine et al.
Nuckolls discloses two starting circuits both of which employ a capacitor discharged by means of a switch through a portion of the lamp ballast~ In one embodiment -2b-~359L~
the switch is a neon tube while in the other embodiment a triac is employed. An inductor and load resistor are placed in series across the lamp, the latter acting as a high im-pedance at the starting pulse frequency. Owens et al dis-closes a starting circuit in which a capacitor is charged upafter a triac is fired, the starting pulse being produced during charging of the capacitor through the lamp Dallast.
Engel et al discloses as prior art a circuit similar to Nuckolls in which a capacitor is discharged through the ballast when a neon tube triggers an SCR. Bodine et al is also similar to Nuckolls and fires a capacitor through the large ballast when a diac triggers SCR 21.
Brief Description of the Drawings Figure 1 discloses a first embodiment of the start-ing circuit according to the invention.
Figure 2 discloses the voltage doubler circuit forming a portion of the Figure 1 circuit.
Figure 3 discloses the trigger circuit of the Figure 1 embodiment.
~;: 20 Figure 4 is a waveform diagram useful in under-` standing the operation of the circuit.
Figure 5 is a second and preferred embodiment of the invention.
Detailed Description Referring to Figure 1, a circuit according to a first embodiment of the invention is illustrated. The start-ing circuit is arranged to be connected in circuit with the ~' standard lamp components found in a typical streetlight assembly. Thus, a gaseous discharge lamp 10 which may be f sodium vapor or other similar type is provided with a ~L~3~;23 ballast transformer Tl and a power fac-tor capacitor Cpf.
A standard 115 volt AC power source is connected across supply terminals 12 and 14 and in the operating state of the lamp provide the current for its illumination. The starting circuit includes a pair of capacitors Cl and C2 and diodes Dl and D2. Capacitor Cl is in series with diode Dl between center top terminal 16 and terminal 18. Similarly, capacitor C2 is in series with diode D2 between terminal 18 and la~.,p terminal 20. Terminal 18 is connected to terminal 14, according to the first embodiment, by means of an in-ductor Ll. The networ~ thus far described constitutes avoltage doubler circuit and the o~eration of this portion of the circuit will be described with reference to Figure 2.
Connected ln shorting relation across one side of the capacitors Cl and C2 is a triac 22 including a gate or control electrode 24. Also connected across the capacitors is an RC network including resistors Rl and R2 which form a ~i voltage divider and a capacitor C3 connected to the mid-point 23 of the resistors and to one of capacitors Cl or C2.
Also connected to the mid-point 23 of the voltage divider is one electrode neon bulb 26. The other electrode of the neon bulb is connected to the triac gate 24 as illustrated. The components just described form the trigger circuit effecti~e for firing a pulse from the voltage doubler through the transformer Tl to initiate operation of the lamp 10. The operation of the trigger circuit is described in connection with Figure 3.
~ ~eferring now to Figure 2, the operation of the voltage doubler will be described. ~hen power is applied 3 to terminals 12 and 14 the AC output, during one half of the ~135~L23 , .
power waveform, will be negative with respect to terminal 14. Cl will then charge up to approximately the line voltage through the inductor Ll, diode Dl and the portion of the transformer Tl located between terminals 12 and 16. The
Nuckolls discloses two starting circuits both of which employ a capacitor discharged by means of a switch through a portion of the lamp ballast~ In one embodiment -2b-~359L~
the switch is a neon tube while in the other embodiment a triac is employed. An inductor and load resistor are placed in series across the lamp, the latter acting as a high im-pedance at the starting pulse frequency. Owens et al dis-closes a starting circuit in which a capacitor is charged upafter a triac is fired, the starting pulse being produced during charging of the capacitor through the lamp Dallast.
Engel et al discloses as prior art a circuit similar to Nuckolls in which a capacitor is discharged through the ballast when a neon tube triggers an SCR. Bodine et al is also similar to Nuckolls and fires a capacitor through the large ballast when a diac triggers SCR 21.
Brief Description of the Drawings Figure 1 discloses a first embodiment of the start-ing circuit according to the invention.
Figure 2 discloses the voltage doubler circuit forming a portion of the Figure 1 circuit.
Figure 3 discloses the trigger circuit of the Figure 1 embodiment.
~;: 20 Figure 4 is a waveform diagram useful in under-` standing the operation of the circuit.
Figure 5 is a second and preferred embodiment of the invention.
Detailed Description Referring to Figure 1, a circuit according to a first embodiment of the invention is illustrated. The start-ing circuit is arranged to be connected in circuit with the ~' standard lamp components found in a typical streetlight assembly. Thus, a gaseous discharge lamp 10 which may be f sodium vapor or other similar type is provided with a ~L~3~;23 ballast transformer Tl and a power fac-tor capacitor Cpf.
A standard 115 volt AC power source is connected across supply terminals 12 and 14 and in the operating state of the lamp provide the current for its illumination. The starting circuit includes a pair of capacitors Cl and C2 and diodes Dl and D2. Capacitor Cl is in series with diode Dl between center top terminal 16 and terminal 18. Similarly, capacitor C2 is in series with diode D2 between terminal 18 and la~.,p terminal 20. Terminal 18 is connected to terminal 14, according to the first embodiment, by means of an in-ductor Ll. The networ~ thus far described constitutes avoltage doubler circuit and the o~eration of this portion of the circuit will be described with reference to Figure 2.
Connected ln shorting relation across one side of the capacitors Cl and C2 is a triac 22 including a gate or control electrode 24. Also connected across the capacitors is an RC network including resistors Rl and R2 which form a ~i voltage divider and a capacitor C3 connected to the mid-point 23 of the resistors and to one of capacitors Cl or C2.
Also connected to the mid-point 23 of the voltage divider is one electrode neon bulb 26. The other electrode of the neon bulb is connected to the triac gate 24 as illustrated. The components just described form the trigger circuit effecti~e for firing a pulse from the voltage doubler through the transformer Tl to initiate operation of the lamp 10. The operation of the trigger circuit is described in connection with Figure 3.
~ ~eferring now to Figure 2, the operation of the voltage doubler will be described. ~hen power is applied 3 to terminals 12 and 14 the AC output, during one half of the ~135~L23 , .
power waveform, will be negative with respect to terminal 14. Cl will then charge up to approximately the line voltage through the inductor Ll, diode Dl and the portion of the transformer Tl located between terminals 12 and 16. The
5 charging path is indicated in Figure 2 and designated il.
During the second half of the AC waveform terminal 12 will be positive with respect to terminal 14 and capacitor C2 similarly charges up to the AC line voltage through trans-- former Tl J diode D2 and Ll. This charging path is indi-cated in Figure 2 and designated i2.
After one cycle of the AC voltage there exists a voltage of two times the line voltage between the points designated A and B in Figure 2. The trigger circuit to be described presently is effective for shorting points A and B together to produce a starting pulse which is applied through the transformer Tl to initiate operation of the lamp 10.
Referring to Figure 3, the trigger circuit operates in the following manner. After capacitors Cl and C2 have been charged up so that a voltage of two times the line voltage exists between points A and B, capacitor C3 begi~s charging since it is connected between point B and the mid-point 23 of the voltage divider formed by resistors Pl and R2. I~hen capacitor C3 has charged to a voltage equal to or exceeding the ionizing potential of neon lamp 26 flash-over occurs and the lamp conducts discharging capacitor C3 into the gate 24 of the triac 22. This turns the triac on shorting points A
and B together producing the desired starting pulse through the center tap terminal 16 and the portion of the ballast 3 between terminals 16 and 20. At the point of the flash-over ~3~ 3 i~ the neon lamp provides a visual indication of proper trigger circuit operation which can be readily viewed by a service technician in the event of a lamp malfunction. After the starting pulse has been produced and applied to the lamp the neon bulb ceases conduction terminating the trigger operation.
A principal advantage of the present invention is the manner of producing the pulse as compared with the prior art. The present invention, by shorling the capacitors in the voltage doubler circuit, produces a voltage pulse applied through a portion of the lamP ballast Tl to the lamp. Because the capacitors are shorted across, however, -the circuit can draw no additional current through the trigger circuit as long as the triac is conducting. This Eeature is important in the case where a lamp is defective or the power factor capacitor Cpf has failed. In prior art circuits these conditions often lead to premature failure of the starting circuit because the current passing through the start-ing circuit during its repeated operation when the lamp does not light causes over-heating. The present invention, however, avoids this heating and premature failure because of the unique construction which prevents current flow through the starting circuit duringtriac conduction thereby eliminating the need for the series resistor present in the prior art circuits.
As indicated previously, the inductor Ll is con-nected between terminals 18 and 14 to present a high impedanceto the short duration high voltage pulse produced when the trigger circuit fires. This keeps the high voltage pulse from getting into the charging circuit.
Referring now to Figur~ 4, various waveforms pro-3 duced by the circuit and useful in understanding the operation ~L~35~3 thereof are illustrated. The AC input applied to terminals12 and 14 is illustrated as waveform 40. The voltages ob~
tained on the capacitor Cl and C2 after one cycle of AC
operation are illustrated as waveforms 42 and 44. From these waveforms it can be seen that at points A and B a voltage exists which is two times the input voltage.
I~aveform 46 illustrates the time varying~ voltage at the mid-point 23 of the voltage divider formed by resistors Rl and R2. Waveform 48 shows the manner in ~hich capacitor C3 charges to a voltage sufficient to cause ignition of the neon tube 26. At the point of flash-over the voltage on the capacitor and the neon tube (waveform 50) rapidly returns to zero as the capacitor discharges into the gate electrode of the triac. Waveform 52 indicates that the voltage between points A and B prior to firing the triac is appro~imately twice the line voltage and subse~uent to the triac firing rapidly drops to zero as the points are shorted to~ether.
j Waveform 54 is an approximation of the high voltage pulse, usually on the order of six ~V, produced when the triac shorts the capacitor and the pulse passes through a vortion of the auto transformer Tl.
The circuit of Figure 1 is advantageous in those situations where it is desired to make the starting circuit compatlble with existing lighting installations which permit connections to the lamp and the lamp ballast only at specified locations. The circuit of Figure 5 is preferred to those instances where new installations are being contemplated and ! will now be explained. The circuit of Figure 5 is substan-tially identical to the Figure 1 circuit. However, the 3 inductor Ll has been eliminated and the charging and trigger ~3~i~23 portions of the circuit are connected across terminals 12 and 16 of the transformer Tl rather than terminals 16 and 20 as was the case in the firs~ embodiment. In all other respects the structure of the circuit is the same as the first embodiment. The inductor Ll is omitted because the high voltage pulse cannot enter the charging circuit as was the case in the first embodiment as may be seen by tracing the discharging path through the circuit. ~hen the triac fires the capacitors discharge through terminal 12 and the ballast portion between terminals 12 and 16. Thls, in turn, induces a high voltage pulse in the ballast portion between terminals 16 and 20 which pulse is applied to the lamp. The high voltage pulse cannot enter the charging circuit since the circuit is no longer connected in the pulsing path as was the case in the first embodiment where capacitor C2 and diode D2 are connected in series across terminals 18 and 20.
A principal feature of the invention is the ability of a technician to rapidly determine the source of a lamp malfunction. This is possible by virtue of the use of the neon lamp as part of the trigger circuit. In order to test the starter circuit the sodium vapor lamp is merely unscrewed from its socket. If ~he neon lam~ flashes it is an indication that the voltage doubler circuit of Figure 2 is properly functioning, that the ballast Tl is receiving power and that the triac is triggering. When a functioning lamp is screwed into the socket an arc in the lamp will indicate that high voltage is reaching the lamp. When the lamp starts drawing ' current triggering will cease and the neon lamp will cease firing. If the power factor capacitor is bad, this condi-3 tion is indicated by firing of the neon lamP, and an arc in ~L~L359L~3~
a functioning sodium lamp but with no tendency for the lamp to start drawing current. This last condition is one which frequently causes failure in the prior art circuits because of DC continuity and the excessive duty cycle which exists causing excessive heating of ~he starting circuit components.
By contrast, the present invention's voltage doubler, once the capacitors are shorted across, draws no additional current until the supply voltage again passes through zero and the trigger circuit resets. This eliminates the need for a load resistor present in the prior art circuits and the possibility of the resistor failing due to the high ; duty cycle which occurs when a bulb fails to light and the starting circuit repeatedly fires over a long period of time.
In a typical circuit, such as shown in Figure 1, the compo-nents will have the following values or be of the following types:
Diodes 1~.l4004 Cl, C2 .22mfd C3 1 .047mfd Rl, R2 lMohm Ll 2.12mh While I have shown and described embodiments of this invention in some detail, it will be understood that this description and illustrations are offered merely by way of example, and that the invention is to be limited in scope only by the appended claims.
3o
During the second half of the AC waveform terminal 12 will be positive with respect to terminal 14 and capacitor C2 similarly charges up to the AC line voltage through trans-- former Tl J diode D2 and Ll. This charging path is indi-cated in Figure 2 and designated i2.
After one cycle of the AC voltage there exists a voltage of two times the line voltage between the points designated A and B in Figure 2. The trigger circuit to be described presently is effective for shorting points A and B together to produce a starting pulse which is applied through the transformer Tl to initiate operation of the lamp 10.
Referring to Figure 3, the trigger circuit operates in the following manner. After capacitors Cl and C2 have been charged up so that a voltage of two times the line voltage exists between points A and B, capacitor C3 begi~s charging since it is connected between point B and the mid-point 23 of the voltage divider formed by resistors Pl and R2. I~hen capacitor C3 has charged to a voltage equal to or exceeding the ionizing potential of neon lamp 26 flash-over occurs and the lamp conducts discharging capacitor C3 into the gate 24 of the triac 22. This turns the triac on shorting points A
and B together producing the desired starting pulse through the center tap terminal 16 and the portion of the ballast 3 between terminals 16 and 20. At the point of the flash-over ~3~ 3 i~ the neon lamp provides a visual indication of proper trigger circuit operation which can be readily viewed by a service technician in the event of a lamp malfunction. After the starting pulse has been produced and applied to the lamp the neon bulb ceases conduction terminating the trigger operation.
A principal advantage of the present invention is the manner of producing the pulse as compared with the prior art. The present invention, by shorling the capacitors in the voltage doubler circuit, produces a voltage pulse applied through a portion of the lamP ballast Tl to the lamp. Because the capacitors are shorted across, however, -the circuit can draw no additional current through the trigger circuit as long as the triac is conducting. This Eeature is important in the case where a lamp is defective or the power factor capacitor Cpf has failed. In prior art circuits these conditions often lead to premature failure of the starting circuit because the current passing through the start-ing circuit during its repeated operation when the lamp does not light causes over-heating. The present invention, however, avoids this heating and premature failure because of the unique construction which prevents current flow through the starting circuit duringtriac conduction thereby eliminating the need for the series resistor present in the prior art circuits.
As indicated previously, the inductor Ll is con-nected between terminals 18 and 14 to present a high impedanceto the short duration high voltage pulse produced when the trigger circuit fires. This keeps the high voltage pulse from getting into the charging circuit.
Referring now to Figur~ 4, various waveforms pro-3 duced by the circuit and useful in understanding the operation ~L~35~3 thereof are illustrated. The AC input applied to terminals12 and 14 is illustrated as waveform 40. The voltages ob~
tained on the capacitor Cl and C2 after one cycle of AC
operation are illustrated as waveforms 42 and 44. From these waveforms it can be seen that at points A and B a voltage exists which is two times the input voltage.
I~aveform 46 illustrates the time varying~ voltage at the mid-point 23 of the voltage divider formed by resistors Rl and R2. Waveform 48 shows the manner in ~hich capacitor C3 charges to a voltage sufficient to cause ignition of the neon tube 26. At the point of flash-over the voltage on the capacitor and the neon tube (waveform 50) rapidly returns to zero as the capacitor discharges into the gate electrode of the triac. Waveform 52 indicates that the voltage between points A and B prior to firing the triac is appro~imately twice the line voltage and subse~uent to the triac firing rapidly drops to zero as the points are shorted to~ether.
j Waveform 54 is an approximation of the high voltage pulse, usually on the order of six ~V, produced when the triac shorts the capacitor and the pulse passes through a vortion of the auto transformer Tl.
The circuit of Figure 1 is advantageous in those situations where it is desired to make the starting circuit compatlble with existing lighting installations which permit connections to the lamp and the lamp ballast only at specified locations. The circuit of Figure 5 is preferred to those instances where new installations are being contemplated and ! will now be explained. The circuit of Figure 5 is substan-tially identical to the Figure 1 circuit. However, the 3 inductor Ll has been eliminated and the charging and trigger ~3~i~23 portions of the circuit are connected across terminals 12 and 16 of the transformer Tl rather than terminals 16 and 20 as was the case in the firs~ embodiment. In all other respects the structure of the circuit is the same as the first embodiment. The inductor Ll is omitted because the high voltage pulse cannot enter the charging circuit as was the case in the first embodiment as may be seen by tracing the discharging path through the circuit. ~hen the triac fires the capacitors discharge through terminal 12 and the ballast portion between terminals 12 and 16. Thls, in turn, induces a high voltage pulse in the ballast portion between terminals 16 and 20 which pulse is applied to the lamp. The high voltage pulse cannot enter the charging circuit since the circuit is no longer connected in the pulsing path as was the case in the first embodiment where capacitor C2 and diode D2 are connected in series across terminals 18 and 20.
A principal feature of the invention is the ability of a technician to rapidly determine the source of a lamp malfunction. This is possible by virtue of the use of the neon lamp as part of the trigger circuit. In order to test the starter circuit the sodium vapor lamp is merely unscrewed from its socket. If ~he neon lam~ flashes it is an indication that the voltage doubler circuit of Figure 2 is properly functioning, that the ballast Tl is receiving power and that the triac is triggering. When a functioning lamp is screwed into the socket an arc in the lamp will indicate that high voltage is reaching the lamp. When the lamp starts drawing ' current triggering will cease and the neon lamp will cease firing. If the power factor capacitor is bad, this condi-3 tion is indicated by firing of the neon lamP, and an arc in ~L~L359L~3~
a functioning sodium lamp but with no tendency for the lamp to start drawing current. This last condition is one which frequently causes failure in the prior art circuits because of DC continuity and the excessive duty cycle which exists causing excessive heating of ~he starting circuit components.
By contrast, the present invention's voltage doubler, once the capacitors are shorted across, draws no additional current until the supply voltage again passes through zero and the trigger circuit resets. This eliminates the need for a load resistor present in the prior art circuits and the possibility of the resistor failing due to the high ; duty cycle which occurs when a bulb fails to light and the starting circuit repeatedly fires over a long period of time.
In a typical circuit, such as shown in Figure 1, the compo-nents will have the following values or be of the following types:
Diodes 1~.l4004 Cl, C2 .22mfd C3 1 .047mfd Rl, R2 lMohm Ll 2.12mh While I have shown and described embodiments of this invention in some detail, it will be understood that this description and illustrations are offered merely by way of example, and that the invention is to be limited in scope only by the appended claims.
3o
Claims (10)
1. A starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between a voltage supply and said lamp, said starting circuit com-prising:
(a) a voltage doubler circuit connected in circuit with said ballast and said lamp for storing a voltage approxi-mately twice the peak value of the voltage supply when said lamp is nonconducting, said voltage doubler including:
(i) a first circuit arm having a capacitor and diode in series, said diode con-ducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode con-ducting in the opposite direction to the first diode, (iii) said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, whereby one of said capacitors will charge to the value of said voltage supply during each half cycle of the AC supply voltage, (b) trigger means connected in shorting relation across said voltage doubler for selectively discharging the charge stored in said doubler circuit through a portion of said ballast to produce a high voltage starting pulse to initiate conduction in said lamp.
(a) a voltage doubler circuit connected in circuit with said ballast and said lamp for storing a voltage approxi-mately twice the peak value of the voltage supply when said lamp is nonconducting, said voltage doubler including:
(i) a first circuit arm having a capacitor and diode in series, said diode con-ducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode con-ducting in the opposite direction to the first diode, (iii) said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capacitor ends, whereby one of said capacitors will charge to the value of said voltage supply during each half cycle of the AC supply voltage, (b) trigger means connected in shorting relation across said voltage doubler for selectively discharging the charge stored in said doubler circuit through a portion of said ballast to produce a high voltage starting pulse to initiate conduction in said lamp.
2. The starting circuit according to Claim 1 wherein said starting circuit includes impedance means for preventing the high voltage pulse from getting into the starting circuit.
3. The starting circuit according to Claim 1 wherein said voltage doubler is connected to the high voltage portion of the lamp ballast.
4. The starting circuit according to Claim 3 wherein said starting circuit includes impedance means for preventing the high voltage pulse from getting into the starting circuit.
5. The starting circuit according to Claim 1 wherein said ballast is an auto transformer and said voltage doubler is connected to said ballast between the supply terminal and the center tap terminal of said ballast, whereby the starting circuit is not present in the high voltage pulse path and impedance means is not required to protect the start-ing circuit against damage.
6. The starting circuit according to Claim 1 wherein said trigger means includes means for visually ob-serving when triggering occurs.
7. The starting circuit according to Claim 1 wherein said trigger means is connected to the mid-point of the capacitor and diode in each of said first and second circuit arms, and triggering is effective for shorting the mid-points together to place said capacitors in series to produce said high voltage pulse through said ballast.
8. The starting circuit according to Claim 1 wherein said trigger means includes:
(a) an RC timing network, (b) a triac having a gate electrode, (c) a neon tube connected between said RC network and the gate electrode of said triac, whereby the triac is operated to short said voltage doubler and produce said high voltage pulse when the RC net-work charges up to the flash-over value of the neon tube thereby enabling the triac and visually signalling that triggering has occurred.
(a) an RC timing network, (b) a triac having a gate electrode, (c) a neon tube connected between said RC network and the gate electrode of said triac, whereby the triac is operated to short said voltage doubler and produce said high voltage pulse when the RC net-work charges up to the flash-over value of the neon tube thereby enabling the triac and visually signalling that triggering has occurred.
9. A starting circuit for gaseous discharge lamps having associated therewith a lamp ballast in series between said lamp and a voltage supply, said circuit comprising:
(a) a voltage doubling circuit including:
(i) a first circuit arm having a capacitor and diode in series, said diode con-ducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode con-ducting in the opposite direction to the first diode, said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capa-citor ends, (b) trigger means for discharging said doubler circuit through a portion of said ballast to produce a high voltage starting pulse connected to the mid-point of the capacitor and diode in each of said first and second circuit arms, and triggering is effective for shorting the mid-points together to place said capacitors in series to produce said high voltage pulse through said ballast.
(a) a voltage doubling circuit including:
(i) a first circuit arm having a capacitor and diode in series, said diode con-ducting in a first direction, (ii) a second circuit arm having a capacitor and diode in series, said diode con-ducting in the opposite direction to the first diode, said first and second circuit arms being connected to the supply voltage at their diode ends and connected to the ballast at their capa-citor ends, (b) trigger means for discharging said doubler circuit through a portion of said ballast to produce a high voltage starting pulse connected to the mid-point of the capacitor and diode in each of said first and second circuit arms, and triggering is effective for shorting the mid-points together to place said capacitors in series to produce said high voltage pulse through said ballast.
10. The starting circuit according to Claim 9 wherein said trigger means includes:
(a) an RC timing circuit, (b) a triac having a gate electrode, (c) a neon tube connected between said RC network and the gate electrode of said triac, whereby the triac is operated to short said voltage doubler and produce said high voltage pulse when the RC net-work charges up to the flash-over value of the neon tube thereby enabling the triac and visually signalling that triggering has occurred.
(a) an RC timing circuit, (b) a triac having a gate electrode, (c) a neon tube connected between said RC network and the gate electrode of said triac, whereby the triac is operated to short said voltage doubler and produce said high voltage pulse when the RC net-work charges up to the flash-over value of the neon tube thereby enabling the triac and visually signalling that triggering has occurred.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353506A CA1135423A (en) | 1980-06-06 | 1980-06-06 | Starting circuit for gaseous discharge lamps |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000353506A CA1135423A (en) | 1980-06-06 | 1980-06-06 | Starting circuit for gaseous discharge lamps |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1135423A true CA1135423A (en) | 1982-11-09 |
Family
ID=4117134
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000353506A Expired CA1135423A (en) | 1980-06-06 | 1980-06-06 | Starting circuit for gaseous discharge lamps |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1135423A (en) |
-
1980
- 1980-06-06 CA CA000353506A patent/CA1135423A/en not_active Expired
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| MKEX | Expiry |