CA1294666C - Ignitor disabler - Google Patents

Abstract

RLM:nls RLMP3:b ABSTRACT

An ignitor disabler includes means for means for disabling the ignitor; means for triggering said means for disabling the ignitor after passage of a predetermined amount of time, said means for triggering, having a timing component for measuring the predetermined amount of time, which timing component begins time measuring operation only under certain, predetermined conditions; and means for resetting the timing component of said means for triggering upon lamp ignition.
In its preferred embodiment, the starter specifically includes AC threshold voltage establishing means and a field effect transistor for ensuring a timing capacitor is effectively discharged to zero volts.

Description

IGNITOR DISABLER

This invention relates to ignitor disablers, and more particularly, to iynitor disablers which are suitable for disabling ignitors employed in igniting and operating circuits for high intensity discharge lamps, particularly of the high pressure sodium type.
High intensity discharge (HID) lamps are used in many applictions because of their long life and high efficieny for converting electrical energy to light. The principal types of HID lamps are mercury vapour, metal halide and high pressure sodium (HPS).
Mercury, metal halide and HPS lamps all operate similarly during stablized lamp operation. The visible output results from the ionization of gases within an envelope and which must be broken down before there is any flow of ionization current. For this reason, a high open circuit voltage must be applied to a HID lamp for igniting and this voltage is substantially higher than the operating voltage and the available line voltage.
Another characteristic of HID lamps is that they exhibit negative resistance. That is, when operating their resistance decreases with the applied voltage. As a result, such devices .

5654b/1 1 ~2,~ i66 require an impedance means in their power supply circuit for limiting the current flow to a predetermined value.

Because of the high starting or igniting voltage requirement and the negative resistance characteristic, HID lamps are provided with ignitin~
and operatin~ circuits which provide a relatively high open circuit voltage, a lower operating voltage and impedance means for current limitation. A ballast between the power supply and the lamp typically serves as the impedance means in igniting and operating circuits for HID lamps. For some HID lamps, such as mercury vapor lamps, igniting voltages are on the order of two times the operating voltage. The igniting voltage is generated by the ballast acting in conjunction with a capacitor. For other types of HID
lamps, such as HIPS lamps, wherein the required igniting voltages are typically more than ten times the operating voltages, more complex igniting mechanisms are required. Examples of starting or igniting circuits for such lamps are disclosed in U.S.
Patent 4,322,660 to Johnson and U.S. Patent 4,683,304 to Hitchcock. The Johnson patent discloses lamp, said apparatus having a single capacitor in s0ries with a blocking diode and a charging resistor. When the voltage of the capacitor reaches a predetermined voltage e~ceeding the zener voltage of a parallel zener diode, the capacitor discharges through a ballast which is connected in autotransformer relationship therewith to provide the high voltage ; pulse to start the lamp.

, .

~ ~ L~

Hitchcock discloses an apparatus including two capacitors, two blocking diodes, a voltage sensitive symmetrical switch, and multiple resistances across which pulses are distributed. The aforementioned elements are electrically connected together with a tapped ballast reactor so that one of the capacitors charges through an impendance in the negative half-cycle, and thereafter, when line voltage goes positive, the other capacitor charges through an impendance equal to the sum of the multiple resistances. When the voltage of the capacitors reaches a predetermined voltage exceeding the ~reakdown voltage of the voltage sensitive symmetrical switch, the capacitors discharge. This discharge, because of an autotransformer relationship within the reactor, produces a high voltage pulse of predetermined height and width once per each cycle of the source voltage.
Notwithstanding the many similarities noted above between the various types of HID lamps, there are, however, unique rsquirements for HPS lamps which the ballast system typically provides. As discussed in the preceding paragraph, some type of electronic ignitor is used in conjunction with HPS
ballast coils to produce a high voltage pulse to start the HPS
lamp. In all cases, these electronic ignitors work on the principle of sensing whether or not the lamp is burning, and if not, the ignitor continuously supplies starting pulses to the lamp. Electronic ignitors are generally insensitive to reasons why the l~mp is not burning, and, accordingly, function in the same manner regardless whether non-burning of lamp is caused by lamp failure, by absence of lamp in the lamp socket, or by lamp "cycling'l off. Lamp cycling is a well-known phenomenon in which a lamp nearing the end of its life will light, burn for some time, go out, relight and repeat the cycle time after time, until the lamp ls either replaced or will fail to start at all. This phenomenon is caused because of a characteristic life trend of lamp operating voltage in HPS lamps. As an HPS nears the end of its life, its lamp operating voltage gradually increases. The normal end of such a lamp is when its lamp operating voltage gets so high that the ballast will no longer sustain operation. This condition usually manifests itself as an above-described "cycling" lamp. Further information about this phenomenon is set in an article entitled "Recommendations for Lamp Maintainance in High Pressure Sodium Luminaires", in Main-Lighter -- Official Publication of the InterNATIONAL
ASSOCIATION OF LIGHTING MAINTANCE CONTRACTORS, Volume 10, Number 7, page 1, (December 1982).
From the foregoing, it should be clear that there are a number of shortcomings in the prior art. In certain cases, e.g., when a lamp is cycling, failed or missing, ignitors in HID circuits continue to operate. Such futile operation shortens ignitor life, particularly in cases where the ignitor operates in conjunction with the ballast so that more than excitation power is drawn by the transformer, that is, to be more specific, where the ballst coil is stressed as a consequence of the ignitor operation. Cycling lamps can also cause problems by possibly avoiding easy detection of 5654b/12 ~2~

impending failure. A lamp may be "cycling on" when inspected and, hence, escape replacement. In situations where obtaining access to lamps is difficult and inspections are not frequent, such as when the lamps are used for roadway lighting, failure to detect a cycling lamp will inevitably lead to futile ignitor operation consequent aeterioration.
To overcome the above-described shortcomings in the prior art, and to provide other advantages and new features described in greater detail below, the present invention, either incorporated into or designed for retrofit into an igniting and operating circuit for a lamp, includ~s means for means for disabling the ignitor for the lamp, means for triggering said means for disabling the ignitor after passage of a predetermined amount of time, said means for triggering having a timing component for measuring the predetermined amount of time, which timing component begins time measuring operation only under certain predetermined conditions; and means for resetting the timing component of said means for triggering the lamp ignition.
Accordingly, one object that the present invention is to disable ignitors for HPS lamps under fault or no lamp conditions.
Another object of the present invention is to increase the effective lives of ignitors and ballasts in HPS lamps igniting and operating circuits by preventing lamp cycling and unnecessary high voltage insultation breakdown.

~5_ Yet another object of the present invention is to give a lamp user a clear indication of end of lamp life.
Still ye-t another object of the present invention is to provide a unit that is substantially independent of the ballast and can therefore be used in conjuction with any standard ballast ignitor currently commercially available for conventional HPS lamps.
A further object of the present invention is to provide an ignitor disabler unit that can be retrofitted to any existing installation at minimum cost, since the ballast does not have to be changed to accommodate the function.
Other objects, advantages, and new features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:
Figure 1 is block diagram of a igniting and operating circuit or HPS lamp, such circuit including therein an ignitor disabler according to the present invention;
Figure 2 is a block diagram showing subportions of an ignitor disabler according the present invention; and Figure 3 is a circuit diagram of a preferred embodiment of ignitor disabler according to the present invention, which embodiment is especially suitable for use in conjunction with conventional high pressure sodium lamps upto a 150 watt maximum.

DETAILED DESCRIPTION OF THE INVENTON

In Figure 1 is shown a schematic diagram of a circuit for connection across an AC source for igniting and operating a HPS lamp 10. The circuit includes an ignitor disabler 12 according to the present invention. The circuit comprises input terminals 14, 16 operable to be connected across the AC source and output terminals 18, 20 operable to have the lamp 10 connected across.
A convention ballast reactor 22 has a tap 24 intermediate the ends thereof which defines first and second winding portions, said first winding portion generally having a greater length than said second winding portion, and having a transformation ratio therebetween substantially greater than unity. The ballast reactor 22 is connected at its ends between input terminal 14 and output terminal 1~, with the second winding portion connected to the output terminal 18. Input terminal 16 electrically connects the output terminal 20. Details regarding this type of structure and its function are very well known to those skilled in the art and are discussed at length in numerous references, including U.S. Patent 4,107,579 to Bodine. Likewise those skilled in the art recognize the desirability in many cases of including a power correction capacitor (not shown) in HPS lamp circuits. As details regarding inclusion and placement of such a capacitor are well known, they are not discuss~d further herein.

A conventional ignitor, such as described in the prior art section above, is connected across a second winding portion of ballast 22 so as to e~ploit the inherent autotransformer relationship therein and thus be capable of generating a high voltage pulse to ignite lamp 10. As can be seen in Figure 1, this connection across the second winding portion of ballast 22 is accomplished by electrically connecting ignitor 26 at some point within its system to tap 24 and at some other point within its system to output terminal 18. Whereas in conventional igniting and operating circuits for HPS lamps the igniting apparatus also is directly in circuit with output terminal 20, in the circuit shown in Figure 1 a new element 12, the ignitor disabler according to the present invention, is inserted between ignitor 26 and output terminal 20. As is further shown in Figure 1, at some point the ignitor disabler system according to the present invention also connects to output terminal 18.

For clarity and convenience, at this point terminal connections to what can be considered an independent ignitor disabler system or retrofittable unit, are designated ignitor disabled terminals 28, ~ 25 30, 32. Referring to Figure 1, terminal 28 can be ; seen to electrically connect to some point within the ignitor 26 system, terminal 30 can be seen to electrically connect to output terminal 20, and 20, and terminal 32 can be seen to electrically connect to output terminal 18.
Referring now to Figure 2, the ignitor disabler 12 is shown therein in greater detail. Major subcomponents of the disabler 12 are depicted by individual blocks. Terminals 30 and 32 can be seen to electrically connect to a power supply portion 34. Power supply portion 34 is designed to convert alternating current from the ballast secondary winding to direct current. Accordingly, power supply portion 34 effective divides disabler 12 into an AC part 36 and DC part 38, the border between the respective part designated by dashed line 40. It is important to note that the time delay initiating portion 42 is depicted as operating within the AC
part 36 of disabler 12. The purpose and function of portion 42 and further details about this aspect of applicant's invention are discussed in greater detail below.

~ erminal 28 can be seen to electrically connect to a switch portion 44. Switch portion 44 is designed to generate an ignitor disabling signal for transmission to ignitor 12 via terminal 28 under certain predetermined conditions. Switch portion 44 is connected and triggered by a switch trigger portion 46. Under the certain pradetermined conditions, portion 46 is designed to trigger portion 44, thereby transmitting an ignitor disabling signal out of the disabler via terminal 2~. Under the teachings of the present invention, the present predetermined conditions involved passage of a _g_ ;

certain predetermined amount of time. Accordingly, switch trigger portion 46 includes a timing component for measuring time.
Switch trigger portion 46, already discussed as heing connected to switch portion 44 is also connected to a switch trigger reset portion 48. Switch trigger reset portion 4B is designed to sense through various connections which ultimately lead to terminals 30 and 32, across which lamp 10 is connected, lamp 10 ignition. Once switch trigger reset portion 48 senses lamp 10 ignition, it resets trigger portion 46 by, under the teachings of the present invention, stopping and immediately resetting to zero the timing component within the switch trigger reset portion.
Referring now back to time delay initiating portion 42, mentioned only briefly above, the portion 42 is designed, in part, to perform the opposite function of switch trigger reset portion 48. Whereas switch trigger reset portion 48 stops and immediatel~ resets to zero the timing component of switch trigger portion 46, time delay intiating portion 42 sets the timing component into operation. Once the timing component is set into operation, by means discussed immediately below, unless the reset portion subsequently senses lamp ignition and terminates time measurement, switch trigger portion 46 will trigger switch portion 44 and cause transmission of a disa~ling signal out of disabler 12. Two important aspects of portion 42 under the teachings of the present invention should be noted.
First, portion 42 includes means for establishing a threshold voltage. As discussed in the description of a preferred embodiment ~2~6~

below, this threshold voltage can be used as a bench mark for establishment of the certain predetermined conditions which begin the measuring of time within the switch trigyer portion 46. For example, as in the preferred embodiment described below, this threshold voltage could be compared to the operating voltage of a lamp lO and systematically connected so as to begin the time measuring if and when the lamp operating voltage exceeds the threshold voltage. It should be remembered, as discussed in the background of the prior art section above, that a HPS lamp's operating voltage rises as the lamp nears the end of its life, so -that an operating voltage being greater than a threshold voltage is an effective timing trigger. A second important aspect of portion 42 it is designed to operate in the previously described AC part 38 of disabler 12. In conventional practice, threshold voltages are set in the DC parts of circuits. There are a number of advantages in establishing a threshold in the AC part of a circuit including less complexity of construction. These advantages, and the awareness that this exceedingly novel feature of applicant's invention, should become clear to those skilled in the art upon examination of the example of the preferred embodiment described immediately below.
Referring now to Figure 3, shown therein is a circuit diagram for preferred embodiment of the ignited disabler on the present invention. The topography is basically the same as in Figure 2 except for including some circuit details for pratical CHN-014076 1~ i PATENT
RLM:nls RLMP3;b application. Terminals 32, 30, 28 correspond to the identically numbered terminals in Ffgures 1 and 2.
The power supply portion of the circuit o~ Fig~re 3 comprises choke 5~ and rectifying diodes 52, 54. Of course, it 0~ should be readily apparent to those skilled in the art that alternating current dppl~ed across ter~;nals 3~9 30 will be converted ~o direct current by speration of diodes 52, 54.
The ti~e delay initiating portîon, which, as ~entioned above, performs an AC threshold function9 comprises dropping resistor 56 and zener d1Ode S8.
The sw;tçh portion o~ disabler 12 eomprises a bi-directiond1 trtode ~hyristor or triac 60. Triac 60 is inserted between terminal 28 and swi~ch tri3ger portion 46. In ~igure 3> the swltch tr1gger portion comprises resistor 62, 64, capacttor 66 ~nd field effect trans;s~or (FET) 68. Those skilled în ehe ar~ will appreciate ~hat the ~bove-identi~ied components cons~itute a conventional RC timing network whtch operates in conjunctlon with FET
68 to apply a "trigger" current to the gate of triac 60. In preferred embodiments o~ ~he present lnvention, Qf whtch the ~mbod;men~ o~ Figure 3 is an axa~ple, built in t~me delay wi11 be suf~ktent to accommodate momentary interruption o~ power resulting in l~mp outage. As is ~el1 known to those skilled ~n ~he ~rt, lamp ~nd fixture com~inations, af~er operatin~ fior some time and be~ng ex~ingu;shed, must coo1 down to a certain d~gree before ~he la~p ts capable of being reignited. In such hot res~rike circumstances, if RLM nls RLMP3:b sufficient ti~e is not a110wed for the igni~or ~o be in the on ~o~e during the cool down period, ~he high voltage pulses w;ll cQa~e before the lamp is capable of reignition resulting ~n lack of lamp re~trike, The various elements of the circuit depicted in Figure 3 05 are o~ such values and are so operatively connected to provide sufficient time for hot restrike of lamps.
A secon~ ~ET, designated FET 70, a resistor 72 and a capacitor 74 combine to form the switch trigger reset portion of the disabler. As those skilled in ~he art w~ll readily apprecia~e, the di5charge of timing capacitor 66 is perfor~ed by FET 70. As has been previous~y mentioned, 1n all previous circui~s serving the purpose of the circuit of the present invent~on, a bipolar ~ransistor has b~en us~d to d~scharge timing capacitors. This practice has left a voltage residue of approxi~ately 0.6 volts in capacltor 66. The use lS of FET 70 in the c;rcuit of the present inven~ion insures that timing capacitor 66 discharges to zero volts at all temperatures. A second aspec~ of the ~bove-described trigger reset por~ion that ~hose sk~lled in ~he art will readily appreciate is tha~ i~ is elec~rically incorpora~ed into the circuit shown in Figure 3 so that ~ET 70 resets or discharges timing capacitor 66 upon sensing of lamp 10 ignition accamplished based upon vol~age drop across lamp 10 connected a-ross terminals 30 and 32.
Various other circuit co~ponents, spec~fically, resistors 76, 78, 80, capacitor ~2 and zener diodes 84, 86 are incorporated into the circuit ~f the preferred embod;ment o~ ~he present invent~on CHN-014076 ~ 2~4~66 PAT~NT
RLM:nls RLMP3:b as position clearly set forth ln Figure 3 where they perform current resisting, filtering and vol~age limiting funct~ons in well known m~nner~ fully Ull~ dnd a~precl~tea Dy ~no~e skilled in the art.
By way of example only, a eircuit such as shown in F1gure 3 05 could be construct~d of co~ponents having designations or values as l~sted below.
~esignation Element ~umber ~Ye~ or Yalue Inductor 2~mH
52 ~iode tN4001 54 Diode ~N4001 56 Resistor 1~0K
58 Zener DirJde 75V, 1N5374 Triac T2300B
S2 Resistor lMES
64 Resistor 1.2K
66 Capaci~or 220uf. 10Y
68 ~ET 2N5640 72 Resistor 470K
7~ Capaeitor 0.1uf 76 Resistor 5 6~ W
78 Res~stor 220 Resistor 270 82 C~pacitor 220uf, 10Y
84 Zener Diode 6.8V, 1~53~2 ~6 Zener Diode 19Y, 1NS3 From the foregoing descrlption and fdentif k~tion o~
eircuit components, ~hose skilled in the art will readily appreoiat~
and understand operatlon of ~he presen~ly preferred embod~ment of the present inventionO Lamp 10 Yoltage passes through choke 50 which ~ilters the high voltage starting pulses from the 120 V.A.C. present at that point. Reslstor 76, placed in serles with choke 50, per~orms A Yaltage dropping and curr~nt limitin~ function ror the negatlve ~ 14 -RLM:nls ~ f~
06/09/87 ~-~J~ ~ ~ ~'~
RLMP3:b 6 V.D.C. supply. Zener d;ode 849 connected from the end of res;stor 7S to common, limits the voltage ~nd produces a square wave output p~aked at negative ~.8 ~olts. Thls square wave is cause to flow through a recti~er diode 52 insuring that only negative voltage is 05 present on fllter capacitor 8~ which is connected fr~m the anode of diode ~2 to common.
The timing circuit components are resistor 62 in series wi~h capacitor 66 connec~ed from the com~on to the nega~ive 6 vott power sUpply line. The common po~nt of the RC timing network is connected to the gate of FET 68 with the drain and supply ronnections of FET 6~ going to the co~mon and neyative 6 volt power supply lines.
When power is first applied to the clrcuit the gate of FET 68 is held low ~nd FET 68 is turned off. As capacitor ~6 charges, ~hrough current ~low from res~stor 62, FET 68 gate voltage increases until FET 68 turn5 on, and prevents current ~rom flowing into the gate terminal of triac 60.
Trid~ 60 c~ntruls the AC power to the lgn1tor 26. Trlac 60 exercises such cDntrol because it is in serles with the ~ommon and starter conne~tion point 2B as ~epicted in Figure 1. On ini~ial power up current flows into the gate of triac 60 vla re~ist~rs 7fi, 64 ~nd 78 which limit the current. As the timing circuit comes 1nto effect and FET 68 ~urns on, the triac 60 ga~e current cedses to flow and triac ~0 turns off preventing starter 26 fr~m-~unctionlng.

9~66~i The rese-t function is preformed by FET 70. A negative 25 V.D.C. supply, for the reset function, is generated by dropping the voltage and limiting the current, through the resistor 56 and the series zener diode 58. The diode 58 also determines a threshold vo:Ltage under which the reset is preformed. The voltage is squared by the zener diode 86 connected from the cathode of zener diode 58 to the anode of diode 52, and then rectified and smoothed by the diode 5~ and capacitor 74. This negative 25 V.D.C. is connected to the gate of FET 70 and controls the discharge of timing capacitor 66.
When the negative 25 V.D.C. is not present, which it would not be when the lamp is operating, resistor 72, connected from the gate of FET 70 to the common, pulls the gate of FET 70 high, turning the FET 70 on and discharging or resetting capacitor 66. When the negative 25 V.D.C. is present, as it would be if the lamp voltage is high or if the lamp is bad or if there is no lamp, the gate of FET 70 is pulled low turning it off and allowing capacitor 66 to charge up and perfcrm predetermined time delay, energi~ing starter 26.
At this point, practical operation of the ignitor disabler should be readily apparent to those skilled in the art. For example, when incoporated into or retrofitted in an igniting and operting circuit for an HPS lamp and a cold start (lamp) is undertaken, the ignitor disabler will have no effect and the lamp will start and operate normally. ~nder a cold start (unlamped~ condition with the ignitor disabler in the circuit the high voltage pulses will cease after the predetermined interval. If a lamp is screwed into a ~ ~.

CHN~014076 ~ G6 PATENT
RLM:nls 0~/09~87 RLMP3:b receptacle of a fixture under these cond~;on~, the lamp will not lgnite and it will be n~cessary ~o reset the disabler. Reset under these conditions would ent~l turning ~he po~er off and on again which will lead to the lamp ignit~ng and functioning normally. If d 05 short power interruption were to occur, a circui~ having ~he disdbler wlll extinguish the lamp, and a cool down period of 30 to 60 seconds will occur before ~he lamp retgnited. This is identtcal to operation o~ circuits without a disabler installed, as the disabler resets itsel~ ~u~omatically. If the la~p shall be f~ulty or if a 1amp parame~ers go beyond the capability of the ballast output, as in the case of a cycling "end of life" lamp, the disabler will disable the ignitor and, hence, increase its useful life. In a regular sys~em, on the other hand, the ~gnitor will con~inue to supply high ~oltage and rQduce the ignitor's operational life. It ~ay be noted that in the case of the cycling "end of life" larnp, s~itching the power off And ~n again resets the dlsabler and th~ la~p will rQignite and run for a cycle.
With regard to method of l'abrica~ion of a circul~ accord;ng to the present invent~on, a printed circuit board containing the circuitry as ~hown in Fi~ure 3 and po~ted in a can approximately

2-1~4 in~hes ti~es 1-1/2 1nche~ times ~-1/4 ~nches oval, wl~h ~hree leads protruding outside the can ~or connect~ng purposes can be ~onstruct~d by conventiona1 techniques. Further, thP can can be insul~ted by a polyolef;n heat shrink ~ube to prevent shor~ing to 2~ çurrounding c1rcuitry, also a conventional technique. An alternativ~

, CHN-014076 ~2~4~6 PAT~NT
RLM;nls RLMP3:b construction would be to cast the circui~ board in a potting co~pound without a sepdrate ~etal can.
A unique aspect of the ignltor disabler ~ the present invention is its independence fr~m the ballast. ~ecause of this 05 indPpendence, it can be used in conjunc~ion wlth any standard ballastJ1gnitor currently commercially available with appropriate adjustment of element values within the disabler. The preferred embodi~ent of Figure 3 can itself be used on any primary voltage from 12û volts to 600 volts without modification since it derives lts power from ~he ballast secondary winding which in all cases involvinq ta~ps of 150 wa~ts or lower is providing the 120 vo1~ open circui~
volta~e dictated by the arc tube voltage req~irement of such la~p5.
Further, in all potent~al embod1ments of the disabler ~f the present invention, becsuse each ;s a separate unit, each can b~ retrofitted to any existi~g installa$ion at ~inirnum cost, since the ballast does not have to be changed to accommodate the funct;on.
~bvious, numerous modifications and ~ariations of the pre5ent invention are possible in light of the above teachings. For : exa~ple, in the presently preferred embodiment sw~tch trigger portion46 ~n~ludes an FET 68. This component 68 could be eliminated ln future preferred e~bodiments of the present invention. Other chanyes may be made by c~rcuits to work w~th higher wa~tage HPS lamps. I~ is therefore to be understood that, wlthin ~he scope o~ the appendec;
claims, the preSent invention may be practiced otherwlse in a specifical1y descrlbcd hereinabove.

.. 18 -,, ,~

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a circuit for igniting a high intensity discharge lamp, with a characteristic voltage that varies during phases of lamp operation, said circuit including in an igniting portion, an ignitor disabler comprising:
disabling means for the igniting portion during abnormal lamp operation;
triggering means for said disabling means after passage of a predetermined amount of time, said triggering means having a timing component for measuring the predetermined amount of time by means of a field effect transistor fully discharging a timing capacitor, which timing component begins time measuring operation only under certain, predetermined conditions;
resetting means for the timing component of said triggering means upon lamp ignition; and means for establishing a threshold voltage for the triggering means which threshold voltage is higher than the characteristic voltage of the lamp under normal operating conditions.

2. The invention as defined in claim 1 wherein said lamp is a high pressure sodium lamp and the certain predetermined conditions under which the timing component begins time measuring operations include all conditions in which the characteristic voltage of the lamp exceeds the threshold voltage.

3. The invention as defined in claim 2 wherein the ignitor disabler further comprises:
means for receiving AC power; and a power supply portion which converts alternating current to direct current effectively dividing the disabler into an AC part and a DC part.

4. The invention as defined in claim 3 wherein the means for establishing the threshold voltage acts on the AC part through the power supply portion.

An apparatus for connection across an AC
source for disabling an ignitor for a high intensity discharge lamp, said lamp having a characteristic voltage that varies during the life of the lamp, said apparatus comprising:
input terminals operable to be connected across said AC source and said lamp;
establishing means for a threshold voltage, which threshold voltage is higher than the characteristic voltage of the lamp under normal operating conditions;
means for producing an ignitor disabling signal at least when the characteristic voltage of the lamp exceeds the threshold voltage; the means for producing the ignitor disabling signal comprising;
switching means, triggering means for said switching means by means of a field effect transistor discharging fully a timing capacitor, means for measuring time from condition of presence of power within the apparatus and failure of lamp to ignite, means for automatically resetting said triggering means on condition of lamp ignition, and means for causing operation of said triggering means after passage of a predetermined amount of time in the absence of automatic reset of said triggering means.

output means operable to be coupled to said ignitor through which said ignitor disabling signal can be transmitted to said ignitor.

6. The apparatus of claim 5 further comprising means for sensing presence of power within the apparatus and failure of the lamp to ignite.

7. The apparatus of claim 6 wherein said means for sensing presence of power within the apparatus and failure of the lamp to ignite comprises threshold voltage establishing means acting on an AC part of the apparatus.

8. A circuit for a high intensity discharge lamp with a characteristic voltage that varies during the life of the lamp, comprising:
an ignitor connected to the lamp for igniting the lamp when the lamp is turned-off;
an ignitor disabler connected to said ignitor and to the lamp;
said ignitor disabler including detecting means for detecting abnormal operation of the lamp and generating means for a disabling signal, the generating means comprising;
switching means, triggering means for said switching means by means of a field effect transistor discharging fully a timing capacitor, means for measuring time from condition of presence of power within the apparatus and failure of lamp to ignite, means for automatically resetting said triggering means on condition of lamp ignition, means for causing operation of said triggering means after passage of a predetermined amount of time in the absence of automatic reset of said triggering means.
said detecting means connected to said generating means and said generating means connected to said ignitor; wherein said detecting means monitors the characteristic voltage of said lamp, and said generating means generates a disabling signal when said detecting means detects a voltage in excess of a predetermined maximum characteristic voltage for the lamp; and wherein said ignitor disabler disables said ignitor when said detecting means detects abnormal lamp operation by having said generating means transmit the disabling signal to said ignitor.

9. A circuit according to claim 8 wherein the abnormal operation of the lamp is the absence of ignition.

10. A circuit according to claim 8 wherein the abnormal operation of the lamp is the failure of the lamp.

11. A circuit according to claim 8 wherein the abnormal operation of the lamp is the cycling of the lamp.

12. A circuit according to claim 8 wherein said detecting means detests the AC voltage of the lamp.

13. A circuit according to claim 8 wherein the resetting means resets said triggering means when said resetting means receives a signal from said detecting means.

14. A circuit according to claim 13 wherein said detecting means only outputs a signal to said resetting means when the lamp is operating normally.

15. A circuit according to claim 14 wherein said detecting means does not output a signal to said resetting means when said detecting means detects abnormal operation of the lamp.

1286b/5-9