US3407334A

US3407334A - Starting and operating circuit for arc discharge lamps requiring a high starting voltage

Info

Publication number: US3407334A
Application number: US554595A
Authority: US
Inventors: Oliver G Attewell
Original assignee: McGraw Edison Co
Current assignee: Cooper Industries LLC
Priority date: 1966-06-01
Filing date: 1966-06-01
Publication date: 1968-10-22
Anticipated expiration: 1985-10-22

Description

Oct. 22, 1968 o G. ATTEWELL. 3,407,334

STARTING AND OPERATING CIRCUIT FOR ARC DISCHARGE LAMPS REQUIRING A HIGH STARTING VOLTAGE Filed June 1, 1966 IN VEN TOR.

0 50/67 6. flZtezz/eZZ United States Patent 3,4ll7,334 STARTING AND OPERATING CIRCUIT FOR ARC DISCHARGE LAMPS REQUIRING A HIGH STARTING VOLTAGE Oliver G. Attewell, South Milwaukee, Wis., assignor to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed June 1, 1966, Ser. No. 554,595 9 Claims. (Cl. 315-278) ABSTRACT OF THE DISCLOSURE Pulse generating circuit means for generating a high voltage pulse for starting an arc discharge lamp requiring a high starting voltage. The circuit means produces a voltage pulse in first coil means of an inductive device to produce a high voltage pulse in a magnetically coupled second coil means to deliver a high voltage pulse to the discharge device. The pulsing circuitry becomes ineffective when the discharge device is conductive. The circuit means may be used with discharge device voltage supplies which include reactor-type ballasts, autotransformers or isolation transformers.

This invention relates to a circuit for starting and operating, a high intensity, are discharge lamp and particularly to lamps requiring a high starting voltage.

The visible light output from gaseous discharge devices results from the ionization of gases confined Within an envelope and which must be broken down before there is any flow of ionization current. As a result, the voltage required to ignite such lamps is much higher than that required to maintain ionization. For this reason, a high open circuit voltage must be applied to the device for starting and this voltage is substantially higher than the operating voltage and the available line voltage.

Another characteristic of arc discharge devices is that they have a negative resistance characteristic. That is, when operating their resistance decreases with the applied voltage. As a result, such devices also require impedance means in their power supply circuit for limiting the current flow to a predetermined desired value.

Because of these characteristics, are discharge devices are provided with starting and operating circuits which provide a relatively high open circuit voltage, a lower operating voltage and impedance means for current limitation. For example, mercury vapor lamp starting circuits generally include a ballast transformer and a capacitor and provide a starting voltage which is in the order to two times the operating voltage. Such prior art lamp starting circuits, however, are not suitable for recently developed high intensity lamps, such as those of the ceramic discharge and metallic halide types, wherein the required starting voltage is in the order of ten times the operating voltage.

It is an object of the invention to provide a new and improved lamp starting circuit.

Another object of the invention is to provide a lamp starting and operating circuit which provides a relatively high ratio of lamp-starting to lamp-operating voltages.

A further object of the invention is to provide a lamp starting and operating circuit in which substantially conventional ballasts may be employed.

These and other objects and advantages of the instant invention will become more apparent from the detailed description thereof taken with the accompanying drawings, wherein:

FIG. 1 illustrates the invention with respect to a high reactance autotransformer;

FIG. 2 illustrates the application of the invention to a constant wattage autotransformer;

FIG. 3 illustrates the application of the invention to an isolation high reactance transformer;

FIG. 4 illustrates the application of the invention to an isolation constant wattage transformer; and

FIG. 5 illustratesthe application of the invention to a reactor.

In general terms the invention comprises apparatus for igniting and operating discharge means from an A.C. source wherein the discharge means is characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of the source, and including first means in circuit between the source and the discharge means and constructed and arranged to normally provide the discharge means with an output voltage substantially equal to its operating voltage, second means operative when the discharge means is nonconductive for deriving from the source a substantially predetermined voltage and for pulsing the first means with at least a portion of the predetermined voltage to momentarily produce a starting voltage which is substantially higher than the normal output voltage from the first means to render the dis charge means conductive, the second means being rendered ineffective when the discharge means is conductive. More specifically, the first means may comprise first and second portions wherein one portion is adapted to be pulsed by the second means to produce a starting voltage at the other portion which substantially equals the pulse times a constant value.

Referring now to the drawings in greater detail, FIG. 1 shows the invention applied to a high reactance transformer having a magnetic core 11, magnetic shunts 12, a primary winding P and a secondary winding S which is inductively coupled to the primary P. The secondary winding S is schematically illustrated as being divided into a first portion S1 and a second portion S2 by a tap 13, although those skilled in the art will appreciate that two separate windings may be also-employed.

A pair of

conductors

14 and 15 connect the primary winding P across a suitable A.C. source (not shown) such as a cycle, volt alternating supply. In addition, a capacitor C1 shunts the primary winding P.

One end of the primary winding P is connected by conductor 16 to. the tap 13 while

conductors

17 and 18 respectively connect the other ends of the primary winding P and the secondary winding portion S2 to the opposite ends of the discharge device or lamp D. A resistor R and a switching device, symbolized by a biswitch B, are connected in series between

conductors

18 and 17 and across the lamp D. As those skilled in the art will appreciate, a biswitch is a solid state circuit device which presents an open circuit when less than a predetermined breakdown voltage is applied across it and a substantially short circuit when it is subject to a voltage equal to or greater than its breakdown voltage. It will also be understood that while the invention is illustrated with respect to a biswitch, other types of mechanical and electronic switching devices such as relays and silicon controlled rectifiers may also be employed.

It will be appreciated that before the lamp D has started, it will present an open circuit to the transformer T which will then act as an autotransformer. As a result, a secondary voltage will be induced in the winding S2 which, in addition, to the input voltage across primary winding P, will be applied across the lamp D and the series combination of the resistance R and biswitch B. This combined voltage will, however, be insufiicient to start the lamp D which requires a starting voltage in the order of several times the line voltage. For example, a

400 watt ceramic discharge type lamp will require a starting voltage in the order of 2,500-4,000 volts peak while line voltage will be in the order of 120 volts RMS. The secondary voltage induced in' winding S will also be-appliedacross the series combination of the resistor R, and the capacitor C2. This will cause capacitor C2 to begin charging at a rate governed by the time constant of the RC circuit consisting of resistor R and capacitor C2. As capacitor C2 charges, the potential at point 19 will increase until it reaches the breakdown potential of the biswitch B whereupon the impedance of the latter will drop substantially to zero to effectively connect point 19 to the conductor 17. This will, in effect, place the line voltage plus the voltage on capacitor C2 across the winding S1 which then induces, by autotransformer action, a voltage in the secondary winding S2. Because the turns ratio between the windings S2 and S1, a relatively high voltage will be induced in winding S2 which will be added to the line voltage and the total applied across the lamp D. This voltage impulse will be suflficient to cause the lamp to break down and begin conducting current. When the lamp becomes conductive, so that current flows in

conductors

17 and 18, the output voltage of the transformer will fall to the lamp operating voltage. As a result, the potential at point 19 during succeeding half cycles will not rise to a suflicient high value to fire the biswitch B so that it remains in its open circuit condition while the lamp D conducts.

The capacitor C1, which is connected across the primary winding P, provides a low impedance path for the discharge current from capacitor C2 during the voltage impulse generation just discussed.

An illustrative set of components which may be employed for starting a 400 watt ceramic discharge type lamp needing a voltage spike of 2,5004,000 volts peak and one microsecond wide at 90% of maximum from a 120 volt RMS A.C. source are as follows:

P=l48 turns; S1=17l turns; S2=9 turns;

FIG. 2 shows the application of the invention to a constant wattage system which is the same as the system illustrated in FIG. 1 except that a series capacitor C3 has been connected between the other end of the winding S2 and the lamp D to provide a net capacitive reactance in the lamp circuit. This insures that leading current flows in the secondary winding S to provide constant wattage to the lamp D in the manner well known in the art.

FIG. 3 illustrates the application of the invention to an isolation high reactance transformer 10 having a primary winding P, a magnetic core 11, a secondary winding S inductively coupled to the primary winding P and magnetic shunts 12 for providing the necessary leakage reactance. The resistor R and the biswitch B are connected in series with each other and between conductors l8 and 17'. One side of capacitor C2 is connected to the junction 19 between resistor R and biswitch B and the other end thereof is connected to tap 13 which divides the secondary winding S into a first portion S1 having a few turns and a second portion S2 having the remaining turns.

The primary winding P may be connected across a suitable source of A.C. (not shown) whose voltage magnitude will depend upon the parameters of the system. For example, if the biswitch B has a breakdown potential of 240 volts peak then winding P will be connected to a 120 volt RMS system assuming a transformation ratio between windings S and P of two.

When the lamp D is nonconductive so that no secondmy current flows in winding S of FIG. 3, a secondary voltage will be induced which will cause charging current to flow the capacitor C2. This will cause the potential at point 19 to begin rising until it exceeds the breakdown voltage of biswitch B. Upon the latter event, point 19 will be elfectively connected to conductor 17 whereby the entire capacitor voltage will be placed across the winding S1. This, in turn, will induce a voltage in the relatively larger winding S2 due to autotransformer action which voltage will cause the lamp D to break down and begin conducting. Transformer 10 will then act as a high reactance device causing the voltage across the lamp D to fall to its operating level which will be insufficient to maintain the biswitch B in its breakdown state. As a result, biswitch B will return to its open circuit state to effectively remove the starting circuit from the lamp supply system.

FIG. 4 illustrates how the invention may be applied to an isolation constant wattage system. The device illustrated in FIG. 4 is identical with that illustrated in FIG. 3 except that a series capacitor C3 is connected between the other side of the secondary winding S and the lamp D. The capacitor C3 insures that leading current will flow in secondary winding S to provide the constant wattage effeet in the manner well known in the art.

FIG. 5 illustrates how the invention may be applied to a reactor type ballast L having an iron core 20. One side of the reactor L is connected to one side of the source by conductor 21 and the other side of said reactor is connected to one side of the lamp D by conductor 22. The other side of the lamp D is connected by conductor 23 to the other side of the source (not shown). The source may be a suitable A.C. source whose voltage magnitude will dictate the choice of the biswitch B. Assuming that the source is 60 cycle A.C., 240 volt RMS the biswitch B will have a breakdown voltage of 240 volts peak. The resistor R and the biswitch B are connected in series with each other and between conductors 22 and 23 and capacitor C2 is connected between junction point 19 and a tap 24 which divides inductor L into a relatively small winding L1 and a relatively large winding L2. In addition, a capacitor C4 is connected between conductors 21 and 23.

In operation of the embodiment of FIG. 5, the lamp D will initially present an open circuit across resistor R and biswitch B. As a result capacitor C2 will charge until the potential at point 19 exceeds the breakdown voltage of biswitch B. As discussed hereinabove, this will place the capacitor voltage across the relatively small winding L1 which, in turn, will induce a relatively high voltage in the larger winding L2 by autotransformer action. The voltage induced in winding L2 will then provide a relative large voltage impulse across the lamp D through the relatively low impedance capacitor C4. The lamp D will then ignite causing current to flow through the inductor L which will then lower the lamp voltage below that required to hold biswitch B in its breakdown state.

While the invention has been illustrated and discussed with respect to a few types of lamp starting and operating systems, these are merely intended as examples, it being understood that other modifications will be apparent to those skilled in the art once the invention is known. Accordingly the invention is not intended to be limited thereby but only by the scope of the appended claims.

I claim:

1. Apparatus for igniting and operating discharge means from an A.C. source, said discharge means being characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of said source, first means having an input connected to said source and an output connected to said discharge means and constructed and arranged to normally provide a voltage at said output which is substantially equal to the operating voltage of said discharge means, said first means comprising an autotransformer having a primary winding coupled to said source and a secondary winding coupled to said output and divided into first and second coil portions having a transformation ratio between said first and second coil portions substantially greater than one, second means coupled to said source and operative to derive therefrom a substantially predetermined voltage, and third means coupled to one of said coil portions for pulsing said one of said coil portions with at least a portion of said predetermined voltage and for inducing in the other coil portion a voltagewhich is functionally related to said transformation ratio and the magnitude of said pulse to thereby momentarily produce a starting voltage at said output which is substantially higher than the normal output voltage to render said discharge means conductive, at least one of said second and third means being rendered ineffective when said discharge means is conductive.

2. The apparatus set forth in claim 1 wherein said second means comprises energy storage means coupled to said source for being charged and said third means comprises switching circuit means coupled to said energy storage means and operable when the amount of stored energy in said energy storage means reaches a predetermined value to apply at least a portion of the voltage of said energy storage means across said one of said coil portions.

3. Apparatus for igniting and operating discharge means from an AC. source, said discharge means being characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of said source, first means having an input connected to said source and an output connected to said discharge means and constructed and arranged to normally provide a voltage at said output which is substantially equal to the operating voltage of said discharge means, said first means comprising an isolation transformer having a primary winding coupled to said source and a secondary winding coupled to said output and divided into first and second coil portions having a transformation ratio between said first and second coil portions substantially greater than one, second means coupled to said source and operative to derive therefrom a substantially predetermined voltage, and third means coupled to one of said coil portions for pulsing said one of said coil portions with at least a portion of said predetermined voltage and for inducing in the other coil portion a voltage which is functionally related to said transformation ratio and the magnitude of said pulse to thereby momentarily produce a starting voltage at said output which is substantially higher than the normal output voltage to render said discharge means conductive, at least one of said second and third means being rendered ineffective when said discharge means is conductive.

4. The apparatus set forth in claim 3 wherein said second means comprises energy storage means coupled to said source for being charged and said third means comprises switching circuit means coupled to said energy storage means and operable when the amount of stored energy in said energy storage means reaches a predetermined value to apply at least a portion of the voltage of said energy storage means across said one of said coil portions.

5. Apparatus for igniting and operating discharge means from an AC. source, said discharge means being characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of said source, first means having an input connected to said source and an output connected to said discharge means and constructed and arranged to normally provide a voltage at said output which is substantially equal to the operating voltage of said discharge means, said first means comprising a reactor-type ballast connected in series circuit relation between said source and said discharge device and divided into first and second coil portions having a transformation ratio'between said first and second coil portions substantially greater than one, second means coupled to said source and operative to derive therefrom a substantially predetermined voltage, and third means coupled to one of said coil portions for pulsing said one of said coil portions with at least a portion of said predetermined voltage and for inducing in the other coil portion a voltage which is functionally related to said transforma tion ratio and the magnitude of said pulse to thereby momentarily produce a starting voltage at said output which is substantially higher than the normal output voltage to render said discharge means conductive, at least one of said second and third means being rendered ineffective when said discharge means is conductive.

6. The apparatus set forth in claim 5 wherein said second means comprises energy storage means coupled to said source for beingcharged and said third means comprises switching circuit means coupled to said energy storage means and operable when the amount of stored energy in said energy storage means reaches a predetermined value to apply at least a portion of the voltage of said energy storage means across said one of said coil portions.

7. Apparatus for igniting and operating discharge means from an AC. source, said discharge means being characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of said source; first means comprising inductance means having a magnetic core and magnetic shunts and comprising a primary winding connected across said source and a secondary winding divided into first and second coil portions having a transformation ratio therebetween substantially greater than one, one end of said primary winding and one end of said second coil portion being connected across said discharge means, the other end of said primary winding being connected to the junction between said first and second coil portions, said inductance means being constructed and arranged to normally provide at its output to said discharge means a voltage which is substantially equal to the operating voltage of said discharge means; second means comprising capacitor means coupled to said source for being charged and operative to derive therefrom a substantially predetermined voltage; and third means for pulsing said inductance means with at least a portion of said predetermined voltage to momentarily produce a starting voltage at said output which is substantially higher than the normal output voltage to render said discharge means conductive, said third means comprising a resistance and a switching circuit element connected in series circuit relation across said discharge means, the junction between said resistance and said switching circuit element being connected to one side of said capacitor means with the other side of said capacitor means being connected to one end of said first coil portion, and said switching circuit element being coupled to said capacitor means and operable when the amount of stored energy in said capacitor means reaches a predetermined value to apply at least a portion of the voltage of said capacitor means across said first coil portion for inducing in said second coil portion a voltage which is functionally related to said transformation ratio and the magnitude of said pulse; at least one of said second and third means being rendered ineffective when said discharge means is conductive.

8. The apparatus set forth in claim 7 wherein impedance means is connected across said source to provide a low impedance path for said pulse.

9. Apparatus for igniting and operating discharge means from an A.C. source, said discharge means being characterized by a relatively high starting voltage with respect to its operating voltage and the voltage of said source; first means comprising an isolation transformer havin a magnetic core and magnetic shunts and comprising a primary winding connected across said source and a secondary winding divided into first and second coil portions having a transformation ratio therebetween substantially greater than one, the ends of said secondary winding being connectedacross said discharge means, and said isolation transformer being constructed and arranged to normally provide at its output to said discharge means a voltage which is substantially equal to the operating voltage of said discharge means; second means comprising capacitor means coupled to said source for being charged and operative to derive therefrom a substantially predetermined voltage; and third means for pulsing said isolation transformer with at least a portion of said predetermined voltage to momentarily produce a starting voltage at said output which is substantially higher than the normal output voltage to render said discharge means conductive, said third means comprising a resistance and a switching circuit element connected in series circuit relation across said discharge means, the junction between said resistance and said switching circuit element being connected to one side of said capacitor means with the other side of said capacitor means being connected to the junction between said first and second coil portions, and said switching circuit element being coupled to said capacitor means and operable when the amount of stored energy in said capacitor means reaches a predetermined value to apply at least a portion of the voltage of said capacitor means across said first coil portion for inducing in said second coil portion a voltage which is functionally related to said transformation ratio and the magnitude of said pulse; at least one of said second and third means being render ineffective when said discharge means is conductive.

References Cited UNITED STATES PATENTS 2,717,335 9/1955 Sims et a1. 315289 X 3,037,147 5/1962 Genuit et al 315289 X 3,219,880 11/1965 Pett 315-289 X 3,235,770 2/1966 Wattenbach 3l5289 X 3,259,796 7/1966 Hallay 315-289 X JAMES W. LAWRENCE, Primary Examiner.

C. CAMPBELL, JR., Assistant Examiner.

Disclaimer 3,407,334.0Zz'ver G. Attewell, South Milwaukee, Wis. STARTING AND OPERATING CIRCUIT FOR ARC DISCHARGE LAMPS RE- QUIRING A HIGH STARTING VOLTAGE. Patent; dated Oct. 22, 1968. Disclaimer filed Nov. 2, 1970, by the assignee, McGmw-Edz'son Company. Hereby enters this disclaimer to claims 3, 4, 5 and 6 of said patent.

[Oficz'al Gazette February 9, 1971.]