CA1284172C - High wattage hid lamp circuit - Google Patents

Abstract

HIGH WATTAGE HID LAMP CIRCUIT
ABSTRACT OF THE DISCLOSURE
A lamp start, hot-restart and operating circuit for a high wattage, high intensity discharge lamp includes cascaded resonant circuits with capacitors and series-connected inductors connected to an AC source.
A pulse circuit including two pulse transformers supplies streamer-forming current, the secondary windings of the pulse transformers being connected in series with the lamp. When the lamp commences normal operation, the operating current energizes a relay to remove the capacitors and pulse circuit from the operating circuit, allowing the inductor to function as the lamp ballast.

Description

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TITLE: HIGH WATTAGE HID LAMP CIRCUIT
SPECI FICATION
This invention relates to an improved circuit for use ~i-th a high wattage high intensity discharge ~IID) lamp or startln~
the lamp, providing proper power ~o opera~e ~he lamp within -~he desired operating ranye and .instantly ~estarting the hot, deionized lamp if the lamp should be e~tinguished by a temporary power interruption or the like.
Background of the Invention The problems of starting and hot restarting a high intensity discharge lamp are well known and numerous circuits have been developed in efforts to solve the problems associated with such lamps. Most such circuits have been developed for the purpose of operating lamps of relatively low wattage, ~15 i.e. having rated powers ranging from less than 100 to a few hundred watts. Circuits developed for this purpose have not been suitable for use with high wattage HID lamps, particularly metal halide lamps. It has been found that such lamps require higher reionization voltage and energy, more intermediate or "carry through" voltage and energy than such circuits have been able to deliver, plus increased open circuit voltage to initiate and stabilize the arc.
Summary of the Invention Accordingly, the invention seeks to provide a circuit for starting, hot-restarting and operating a high wattage high intensity discharge lamp, the term "high wattage" being used to refer to lamps having power ratings of a~out 1000 watts or above.
Further there is provided such a circuit which will automatically deac-tivate itself after a predetermined interval if it is conneçted to a failed lamp.
Still further there is provided such a circuit in which the starting elements are deactivated in response to the flow of normal operating lamp current.
Further still the invention seeks to provide such a circuit which is reliable and can be constructed at reasonable cost.
Briefly described, the invention includes a lamp start, hot restart and operating circuit for a high wattage, high intensity discharge lamp, including a source of AC power and first and second cascaded resonant circuits connected between '~ .
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the source and the lamp for forming an arc-forming discharge current for the lamp, each of the resonant circuits including a series-connected inductive reactor. Pulse circuit means is coupled to the resonant circuits and to the lamp for producing a streamer-fonning pulse discharge current for the lamp, the pulse circuit means including first and second pulse transformers having their secondary windings connec-ted in series-aiding relationship and connec-ted in series with -the lamp, and a deactivating circuit responsive -to lamp operating current for deactivating the pulse circuit and the resonant circuits so that the reactors function as a ballast for the lamp during normal operation.

- Another aspect of the invention comprehends a start, hot restart and operating circuit for a high wattage, high intensity discharge lamp comprising the combination of a source of AC voltage having a power line and a common line, a first capacitor connected across the source between the power and common lines, first and second inductive reactors connected in series circuit relationship with each other and the power line and a second capacitor connected between the first reactor and the common line, the second capacitor having a value selected to resonate with the first reactor at a first frequency. A
third capacitor is connected between the second reactor and the common line, the third capacitor having a value selected to resonate with the second reactor at a second frequency. There is a high wattage, high~intensity discharge lamp and first and second pulse transformers each having a primary winding and a secondary winding with circuit means interconnecting the: lamp with the secondary windings of the pulse transformers with the lamp between the secondary windings. Pulse circuit means is connected to the second reactor and to the primary windings to provide pulse energy~across the lamp to start or restart:the:
lamp, the windings being connected so that the pulses produced thereby are in an aidlng phase re~iationship.

Still another aspect of the invention comprehends a method~
of starting, hot restarting and operating a high intensity discharge lamp comprising the steps of connecting a p~lurality of series inductive elements and shunt capacitors to form a ", ., :

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plurality of cascaded resonant circuits between a line source of AC power and a high intensity lamp for producing an arc-forming current build~up for the lamp, tuning the cascaded resonant circuits to successively higher harmonics of the line source, connecting a pulse circuit including first and second pulse transformers -to the last o the resonant circuits ~or producing a streamer-Eorming current th~ough the lamp, energizing the resonant circults and pulse circuit to form successive streamer and arc forming currents to ignite the lamp, sensing lamp operating current and deactivating the pulse circuit and the resonant circuits in response to lamp operating current to allow the series inductive elements to function as a standard ballast for the lamp during normal lamp operation.

Although the circuits of the present invention were initially developed for high wattage lamps, it has subse~uently been found, somewhat surprisingly, that the same techniques employed therein can be used with lower voltage inputs to operate larnps rated~at lower power levels. Thus, the circuits are quite flexible and can readily be adapted to operate lamps in the range of about 250 watts to about 2000 watts.

Brief Description of the Drawings In order~to impart full understanding of the manner in which these and other objects are attained in accordance with the invention, particularly advantageous embodiments thereof will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:
Fig. l is a schematic circu1t diagram, partly in~block form, of a start, hot restart and operating lamp circuit in accordance with the invention; ~ ~ ~
Fig. 2 is a more detailed schematic circuit diagram of a further embodiment of a lamp circuit;
Fig. 3 is a schematic circuit diagram, partly in block form, showing a similar circuit used with a high reactance transformer or lag ballast; and Fig. 4 is a schematic circui~ diagram, partly in block form, of a circuit similar to Fig. l~employing a di~ferent form of deactivation means, shown with Fig. l.

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' ~2~4~72 DÇ~Eie~io~_o~ P~,ferred ~mbodiments Referring first ~o Fig. 1, the circuit thereo~
includes a tQrminal 10 whlch is ~onneated to a power ~ in the cirauit and a te~minal 11 which i5 aon-nected to a common line. Terminals 10 and 11 are connectable to a 480-volt AC,source. A capacitor 12 is connected d~rectly aoross the termlnal~ 10 and 11.
First and ~econd inductive reactoxs 14 and 16 are connected in series cixcuit relationship with each ot~er in the power line. Each o~ these reactors is deslgned, for a 1500-watt HID lamp, to have a reactance of about 84.9 m~ at the line ~requency and, preferably, the reactors are substantially identical to each other.
A capacitor 18, also ha~ing a value of about 20 micro~arads, i.s connected ~rom the power line between reactors 14 and 16 to the common llne through a no~mally closed contact set indicated generally at 20 which is actuated by energization of the winding of an electromagnet~c relay 22 connected in series in the common line.: Relay 2~ is a current responsive relay designed to~be energiz~d:when normal lamp operating current ~lows therethrough.
At the sther slde of reactor 1~, a capacitor 24 having a value of about 5 microfarads is connQcted between the powQr line and common ltne through a normally closed contact set 23 of relay 22. Also at the same side o~ reactor 16j an arc streamer generator circuit 26 is connected between the power line and the common line through a contact set 25 of relay 22.~
Circu~t 26 1ncludes a high-voltage pulse circuit for initiating: an arc ~treamer through a lamp. The output o~ circuit 26 is delivered to he prlmary winding~ of two step-up pulse transformQrs 28 ~nd 29, ~he secondary windings of which~are connected ln seri s'with each :

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other and wit~ high intensity discharge ~amp 30. The secondary windings of the pulsQ trans~ormers are connecte~ with khe lamp in between them and are pha~ed 60 that they are aiding as lndiaated by the polarization markings on th~ drawing.
Capacitor 12 ~erves as a power ~otor correating capacitor during normal operakion and ~sti~ens" the AC
eource during hot restartlng. Accordingly, this capacitor remains in the circuit at all times.
~he values o~ capacitors 18 and 24 are selected to resonate with reactors 14 and 16 at seleoted ~reguPn-cies to produce 6paci~ic current patterns in the circuit during the etart and hot-restart modes of operation. However, when the lamp has gone into full ignition and operaki~g ourrent flows ~hrough relay 22, contact sets 20 and 23 are opaned, removing capacitors 18 and 24 from operation and leaving reactors 14 and 16 to function a~ the reactor ballast during nor~al lamp operation. For a 1500-watt lamp, capacitor 18 is seleated to resonate with reactor 14 at approximately tha ~econd harmonic of the line voltage ~raquency.
Similarly, capacitor 24 re~onates with reactor 1~ at approximately the fourth~harmonic. When llne voltage : i8 applied, the open circuit voltage between point C at the output e~de of reactor 16 and the common line is approximately 700 volts ~MS as compared with the 480 volts applied to terminals 10 and 11.
This high, sine wave open circuit voltage supplies arc streamer generator circuit 26 which supplies relatively high~ frequency pulse energy through both pulse transformers 28 and 29 to the lamp. These high voltage pulses cause the formation of a streamer within the lamp and, once the streamer has been formed, the~
intermediate frequency ~oltage from capacitor 24 :

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~L2~3~d72 provides Eu~fici~nt energy to cause an arc d~saha~ge to form wlthin the lamp, xemoving the streamer ~rom the lamp wall. This ~unction i5 prlmarily per~ormed by the fourth harmonic energy. Finally, once the discharge has been formed, a higher energy levsl at lower voltage, at tha second harmonic, produces a high current d~scharga through the lamp which is then maintained by the 60 Hz power supplied directly from the line. In the last portion of this operation, operatlng current i5 sQnsed by relay 22, opening contact sets 20 and 23 and also a normally alosed contact set 25 which is the common connection for arc streamer generator 26, removing capacitors 18 and 24 and leaving the line current at 60 Hz to maintain the arc. `.~
Circuit 26 also includes a time delay circùit wh~ch permits:pulsas to be applied for a predetermined intervalj such as five seconds, but if the lamp does not reach full ignition by the end of that intexval, the high voltage pulse circuit is deactivated and is latched out~of~ operation until the~line voltage is removed and restored. If the high voltage pulses from circuit 26,~ ln con~unction with the other currents disaussed, do not force the lamp into operation, there is a very strong probability that the lamp i~self has failed or reached the end of its useful life, or that there is a major problem with the lamp wiring. ~
Accordingly, the pulses are~terminated to a~id dama~e : to the clrcuitry or to ~he lamp mechanical components.
The series aiding connection o~f kha seconda~y winding ~of~pulse transformers~28~ and 29 allows doubling ~he hlg~ voltage and its energy:le~el~applied to the lamp without lncreasing th~ hlgh voltage to t~

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fixture and avo~ ding the electrical stress applied to those components.
Fig. 2 shows in somewhat greater detail a Gl~CUi~
which operates on the principle~ o~ Fig. 1. It will bQ
recognized that reackor~ 14 and 16, capacikors 12, 18 and 24, pulse transformers 28 and 29, and lamp 30 remain in tha same relative relationships and their ~unctinns are substantially unchanged. ~owever, arc streamer generator circuit ~6 i5 now shown as consist$ng of an on-tim~ detexmining circuit 32 and a pulse generating circuit 34. It will also be observed that the arrangement of relays i8 somewhat different, a : relay 35 having a contac~ set 37 arranged to respond tooperating curren~ and ~o open the circuit leading to capacitor 18 only. A separate relay 38, ronnected in parallel with xelay 36 to also respond to operating current, has a contact set 39 in the conductor which supplies not only capacitor 24 bu~ also timing circuit 32 and pulse circuit 34. Still further, a ralay 40 having no~mally closed con~act set 41 and 42 responds to the conclusion of the timing function in circuit 32 to remove capacitor 18, capacitor 24 and pulse circuit 34 ~rom the ~ystem at the~ conclusion of the timing interval.
Circuit 32 includes a controlled rectifier ~5CR) 44, the switchable conductive path of which is con-nected in series with the winding of relay 40 and also in series with a resis~or 46 and diodes 47 and 48 between the power and common lines. Diode 47 is also : 30 connected to a voltage divider circuit including resistor 49 a~d 50, t~e junction between these resistors being connected to a breakdown diode 52, which leads to the yats o~ SCR 44, and an RC c~rcuit includin~ resistor 53 and capacitor ~4.

A capaaiter 56 is connected ln parallel with the circui~ includ~ng the winding o~ relay 40 and SC~ 4~.
The vol~age aoross capaaitor 56 i8 limlted by a parallel-connected zener diode 58. As wlll be recog-nized by those #killed in the art, SCR 44 is rendered conductive when the voltage across capacitor 54 reaches a sufficiently high Yol~age to cause breakdown of diode 52 and, when SC~ 44 conducts, relay 40 is energized, open~ng contact sets 41 and 42. Opening contact set 42 re~oves~pulse circuit 34~ from~operation and openin~
contact set 41 removes capac~itor 18 from the circuit.
The charging current which develops the voltage on capacitor ~4 flows through diode 47, resistor 49 and resistor 53,~ the div~der~effect of resi~tors 49 and 50 determinlng t~e level of;the~charging current. Since diode 47 is con~ected to the~fourth~harmonic upply at the~output ~of reactor 16,~many~hal~-Cycles~;~of~currQnt are used to charge thR capac~tor. The ¢harqing is relativQly slow,~depending~upon~the ~alue~chosen ~or the components,; but it i8 lntentionally~màde BlOW SO
that the~pulse~aircuit has an adeguate~ opportunity to cause ignition~of lamp 30.~
Be~ore~SCR 44 is made conductlve, capa~citor 56 is charged through diodes 47 and ~8 and throu~h a limiting resistor 4~, the~voltage on capacitor~56 being limited by diode~ sa. Capacitor 56 acts as~a ~ilter capacitor and diode 48~prevents discharging~o~ capacitor~56~into the timing~aircuit lnclud~ng capaoitor 54.;~
After~SCR~44~has become conductlve, energ1z1ng current for~relay 40 ~s~suppl1sd~y~;the ha~-wave direct ourrent supply through~d~iod~ 47 and;~is ~maih~
tained~in the~nergized sta~e~by~he chargQ developed on capacltor s6~. ~Thus; the SCR~is ~alntalned in the~
conductiYe~s~ate and r¢lay 40 is kept ene~gi2ed.

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Energization of relay 40 xemoves the starting and restarting compon~nts from the system, allowing the apparatus to el~ctrically behave like a no~mal ballast having a ~ail2d lamp. As pr~viously indi~ated, relay 40 should not operate until the pulses ~rom circuit 34 have had an opportunity to put lamp 30 into operation and have not done so.
Circui~ 34 includes two high ~reguency triacs 60 and 62, triac 60 having a aonductive path which extends between the common line and the primary winding of pul~Q transformer 28. Similarly, triac 62 has a switchable conductivQ path batween the primary winding o~ pulse transformer 29 and the common line. The gate electrodes of the triacs are connected through resis-tor~ 64 and 65, respectively, and a breakdown diode 66.
Charging circuits for the gates include resistors 68 and 69 which are connected, respactively, to capaci~ors 70 and 71, the ~unction between resistor 68 and capacitor 70 baing connected to d~ode 66~ The supply, as prevlously indicated, comes through contac~ set 4~.
When the voltage across capacitor 70 reaches approximately 480 volts, the breakdown diode becomes conductive and triggers the gates o~ both ~riacs togeth~r, rendering them simultaneously conductive.
The energy stored in capacitors 70 and 71 is then dslivered through the energized triacs to the primary windings o~ the pulse transformers whioh are connected in a series aiding relationshlp, as shown, to cause ignition voltage doubl~ng and in-time phasing. Each 3 0 pUl8e trans~ormer has a primary-to-secondary ratio of approximately ~:tuxns to 200 turns. Resls~ors 68 and 69 determine the charging rate of the capacitorC 70 and 71 znd al~o i olate the di~charge o~ these capacitors, ~n a high ~requency sense, as they discha~ge through . ~ .

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the pulse transformer primariea. Resistors 64 and 65 serve to limit the pea~ gating of the triacs and the peak sidac current, thereby protecting these devicQs, As indicated in connection with Fig. 1, the p~l~e transformers produce a h~yh voltage output ln kh~
s~condaries which is applied to the lamp to cause a ~tream2r which is then backed by high voltage ioniza-tion current delivered from reactors 1~ and 16 and their associated capacitors until, finally, with the lamp in full operation, the capacitors are removed from tha cirouit and maintenance current is supplled by the : 480 volt AC line supply. Again, if the pulses fail to lgnite the lamp, circuit 32 r~moves the pulse circuit by opening contact set 42. ~amp operation energizes relays 36 and 38 to remove all of the starting circuit components from operation.
It will ~also be observed that reactors 14 and 16 are provided with taps 73 and 74, respectively, which ar~ not connected to anything in the circult of Fig. 2.
These taps are provided so that, for a lOOO~watt lamp, a lower voltage and reactanca can be employed. By providing a tap in thi~ fashion, identical reactors can be used ~or either a 1000- or 1500-watt lamp with the other circutt component remaining the same. Using two 400-watt 240-volt high pres~ure ~odium reactors provides the correct lamp operating wattage for a 1000-watt devi~e properly ~apped.
~ig. 3 ~hows a circuit which is fundamentally similar to Fig. 2 except that a single reactor 76 i8 in 6eries with the pul~e trans~ormers and lampl and the supply iB prov~ed throuyh.~ lag ballast or high impedance transformer inaicated generally at 79 which allows the USQ of a lower source voltage. The tran~-~ormer 79 includes a prlmary windlng 78 having a : .
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capacitor 80 connacted in parallel therewith/ th~
primary winding ha~i~g a center tap so thak di~erent voltages can be applied thereko. End termlnal~ 82 and 83 can be connected to a 240-volt supply or, alternatively, terminals 83 and 8~ can be connected to a 120-volt 8uppl~. The ~econd~ry winding 85 also function~ as th2 first reactor equivalent in operation to reactor 14. Capacitor 80 per~orms the power ~actor corrQct~ on and energy storage function of capacitor 12 in the circui~s of Figs. 1 and 2. Capacitor 18 i5 conneat~d across the entire reactance transformer through contact ~ets 41 and 37, as ~efore.
Except ~or the transformer itself, which is a well-understood element in this context, the remainder o~ the circult performs as previously described in connection with Fig. 2. Accordingly, that description will not be repeated.
Fig. 4 shows~a circuit which is substantially identica} to Fig. 1 insofar as the start and hot restart circui~ arrangement and operation is concerned.
~owever, Fig. 4 introduces a di~feren~ technique for deactiva~ing th~ circui~ in ~he event that lamp ignitio~ i5 not achie~ed within a predetermined, xelati~ely short time. The cirauit components which arQ th~ ~ame as described in connection with Fig. 1 are identi~ied by the same reference numerals and will not ba de~cribed again. It will b¢ observed that relay 22 i~ eliminated asi are contact sets 20, 23 and 25.
Instead, the pul e cirouit 25 is connected ~o the common line and capacitors 18 and 24 are connected to the common l~ne, respectively, through:thermally activated normally closed contact sets~ indicated generally at 90 and 91 with~n:a thermal switch unit 92.
A po61tive temperature coefflclent resistance heater 94 ;

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i~ contained within device 92 so that it is in good heat conducting ralationship with contact set~ 90 and 91. Each o~ contact sets so and 91 can b~ a bimetallia deviae c~ a type which di~torts upon reaahlng a predetermined temperature, thereby opening the contact ~et.
In operation, when the circuit is energized and the lamp ha~ not yet ignited, a relatively high open-circuit voltage axists between the output side o~
reactor 14 and the common line. Thi~ high open ~ircuit voltage causes current ~low through resistor 94 which generates haat to elQvate the temperature o~ contact 6Qt8 gO ~nd 91. ~h~ current flowing at the high, open circult vol~age moves the resistance valua o~ the PT~
element 94 to a point on its operating curve at which the currenk level is high, generating sufficient heat to activate the contact sets and open the circuits within a matter of a Pew seconds. However, if the lamp becomes ~ully ignited and operating current begins to ~low, the voltage decreases with a concomitant decreasing level of current, allowing the device to remain dormant.
It will ~e observed that the presen~ invention involves the use of multiple inductances in conjunction with multiple capacitances to ~orm cascaded harmonic or tuned circuits to raise the available line voltage to a much higher voltage and to raise the capacltance energy level so that it is available to establish or reestab-lish a high ~ntensity thermal arc in a hot deionizad lamp. The voltages generated by these cascaded circuit are in parallel with the lamp. Thus, the level o~ the instantaneous lamp power consumption, which represents khe loading on the resonant circuits, serves to ensure adequate capacitive voltage and energy - - -'~ ' .' :

oscillation to meet the lamp's needs ln hot restarting.
Further, the use o~ the sa~c ~asic indu~tance~ ~orm~ a controlled, sequential lamp electrical ~timulation which ~orces the lamp into rapid hot restart without damaging the lamp electrodes ~nd employs the induc-tances ~or stable normal opexation. The use o~ two ~ubstantially identical high voltage generator circuits connected, including the pulse trans~ormers, in a serie~ aiding fashion and synchronized to double the peak high voltage and energy is provided in a way which allows maller part ~izes and easier packaging.
Finally, the current responsive technique ~or deactivating the starting components when lamp operation has commenced relies upon lamp RMS current and causes the~ circult to revert to a lag ballast only when the lamp is completely restruck.
Whil~ certain advantageous embodiments have been chosen to illustrate the invention, it will be under-stood by thosQ skilled in the art that various changes and modi~ications can be made therein without departing from the scope o~ the invention as defined in the appended laims.

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Claims (13)

1. A lamp start, hot restart and operating circuit comprising the combination of a socket for receiving a high intensity discharge lamp;
a source of AC power;

first and second cascaded resonant circuits connected between said source and said lamp for forming an arc-forming discharge current for said lamp, each of said resonant circuits including a series-connected induc-tive reactor;

pulse circuit means coupled to said resonant circuits and to said lamp for producing a streamer-forming pulse discharge current for said lamp, said pulse circuit means including first and second pulse transformers having their secondary windings connected in series-aiding relationship and connected in series with said lamp; and deactivating circuit means responsive to lamp operating current for deactivating said pulse circuit means and said resonant circuits so that said reactors function as a ballast for said lamp during normal operation.

2. A circuit according to claim 1 and further including means for deactivating said pulse circuit means in the absence of lamp operating current after a predetermined interval of pulse discharge current.

3. A start, hot restart and operating circuit for a high wattage, high intensity discharge lamp compris-ing the combination of a source of AC voltage having a power line and a common line;

a first capacitor connected across said source between said power and common lines;

first and second inductive reactors connected in series circuit relationship with each other and said power line;

a second capacitor connected between said first reactor and said common line, said second capacitor having a value selected to resonate with said first reactor at a first frequency;

a third capacitor connected between said second reactor and said common line, said third capacitor having a value selected to resonate with said second reactor at a second frequency;
a high wattage, high intensity discharge lamp;

first and second pulse transformers each having a primary winding and a secondary winding;

circuit means interconnecting said lamp with said secondary windings of said pulse transformers with said lamp between said secondary windings; and pulse circuit means connected to said second reactor and to said primary windings to provide pulse energy across said lamp to start or restart said lamp, said windings being connected so that the pulses produced thereby are in an aiding phase relationship.

4. A circuit according to claim 3 wherein said first frequency is substantially equal to an even harmonic of said source.

5. A circuit according to claim 4 wherein said first frequency is substantially equal to the second harmonic of said source.

6. A circuit according to claim 5 wherein said second frequency is substantially equal to an even harmonic of said source higher than said second harmonic.

7. A circuit according to claim 4 wherein said second frequency is substantially equal to an even harmonic of said source higher than said first frequency.

8. A circuit according to claim 3 and further comprising circuit means responsive to lamp operating current for deactivating said pulse circuit means and said second and third capacitors.

9. A method of starting, hot restarting and operating a high intensity discharge lamp comprising the steps of connecting a plurality of series inductive elements and shunt capacitors to form a plurality of cascaded resonant circuits between a line source of AC power and a high intensity lamp for producing an arc-forming current build-up for the lamp, tuning the cascaded resonant circuits to successively higher harmonics of the line source, connecting a pulse circuit including first and second pulse transformers to the last of the resonant circuits for producing a streamer-forming current through the lamp, energizing the resonant circuits and pulse circuit to form successive streamer and arc forming currents to ignite the lamp, sensing lamp operating current, and deactivating the pulse circuit and the resonant circuits in response to lamp operating current to allow the series inductive elements to function as a standard ballast for the lamp during normal lamp operation.

10. A method according to Claim 9 and further including connecting the secondary windings the pulse transformers in aiding relationship with each other and in series with the lamp.

11. A method according to Claim 10 and further including deactivating the pulse circuit in the absence of lamp operating current after a predetermined interval of streamer-forming current.

12. A method according to claim 11 wherein the resonant circuits are deactivated by disconnecting the shunt capacitors.

13. A method according to Claim 9 which includes tuning the resonant circuits to even harmonics of the line source.