Method and apparatus for disabling sodium ignitor upon failure of discharge lamp

Information

  • Patent Grant
  • 6642673
  • Patent Number
    6,642,673
  • Date Filed
    Tuesday, October 30, 2001
    22 years ago
  • Date Issued
    Tuesday, November 4, 2003
    20 years ago
Abstract
An ignitor disabling apparatus is provided to reliably and automatically disable a universal sodium ignitor with hot re-strike capability, or a 120 Hz pulse capability. The ignitor is configured to disable the ignitor portion of a HID lamp if the lamp fails to start. Timing operation of the disabling circuit is achieved using a power supply that ramps to a steady state to provide triggering of a timer circuit. A normally closed, solid state gating device is used for disabling the ignitor to minimize sparks. The disabling apparatus can be retrofit into an existing universal sodium ignitor.
Description




FIELD OF THE INVENTION




The invention relates generally to a disable circuit that stops the ignitor function of a high intensity discharge (HID) lamp ignition circuit. More particularly, the invention relates to an apparatus and method to control the timing and triggering of the disable function of the igniter circuit.




BACKGROUND OF THE INVENTION




High intensity discharge (HID) lamps such as metal halide (MH) and high pressure sodium (HPS) lamps have increasingly gained acceptance over incandescent and fluorescent lamps for commercial and industrial applications. HID lamps are more efficient and more cost effective than incandescent and fluorescent lamps for illuminating large open spaces such as construction sites, stadiums, parking lots, warehouses, and so on, as well as for illumination along roadways. An HID lamp comprises at least an arc-tube containing two electrodes, chemical compounds and a fill gas. The fill gas can comprise one or more gases. To initiate operation of the lamp, the fill gas is ionized to facilitate the conduction of electricity between the electrodes.




HID lamps can be difficult to start. An HID lamp such as a conventional HPS lamp uses a 2500 to 4000 volt pulse at least once per half-cycle and at selected times during the cycle in order to start, as set forth in a number of standards such as ANSI C78.1350 on HPS lamps, for example. An ignitor is used to provide the necessary pulses to start the conventional HID lamp. If the lamp is extinguished after lamp operation has elevated lamp temperature, the lamp cannot be restarted until after the lamp cools down and the fill gas can be ionized again. For many types of HID lamps, this lamp cooling period can be between approximately 40 seconds and 2.5 minutes, which can be considered unacceptable in situations where, for example, emergency lighting is desired.




A number of circuits have been developed to start or hot restrike HID lamps. These ignitors generally include resistors, pulse transformers and other components, in addition to a conventional ballast. These devices can reduce system efficiencies and substantially increase system cost.




An exemplary ignitor


100


is depicted in FIG.


1


. Terminals


102


and


104


of a lighting unit are connected to an AC power source


106


, as well as to a ballast


108


and a lamp


110


. The ballast


108


comprises a tap


112


and two winding portions


114


and


116


. The ignitor


100


has terminals which are connected to terminals


102


,


112


and


110


. A charging circuit for hot restarting a high pressure xenon HPS lamp or other HID lamp having similar hot restart requirements is provided which comprises a semiconductor switch


118


such as a silicon-controlled rectifier (SCR) or the like is connected so that one end of its switchable conductive path is connected to the end of the first portion


116


of the ballast. The other end of the conductive path of the SCR


118


is connected to the tap


112


via a storage capacitor


120


. A number of sidacs


122


or other breakdown devices are connected between the gate and the anode of the SCR


118


. A current-limiting resistor


126


is provided in series with the sidacs


122


and


124


. If the voltage on the capacitor


120


increases to a level which reaches or exceeds the threshold voltage of the breakdown devices


122


and


124


, the sidacs


122


and


124


become conductive, placing the SCR


118


in a conductive state. Accordingly, the capacitor


120


discharges through the portion


18


of the ballast. Because the winding portions


114


and


116


of the ballast are electromagnetically coupled, the portion


116


of the ballast operates as the primary of a transformer in that a voltage is induced in the winding portion


114


. The high voltage generated in the winding portion


114


of the ballast


108


is imposed on the lamp


110


. The relationship of the winding portions


114


and


116


is selected to create a voltage using the SCR


118


and the sidacs


122


and


124


which is sufficiently high to ionize the material within the arc tube of the lamp


110


.




With further reference to

FIG. 1

, a charging circuit


144


for the capacitor


120


is connected between the tap


112


and the terminal


102


at the other side of the AC power source


106


. This charging circuit preferably comprises two diodes


128


and


130


, a pumping capacitor


132


and two radio frequency chokes


134


and


136


connected in series between the tap


112


and the terminal


102


. Two diodes


138


and


140


are connected between the capacitors


120


and


132


and are poled in the opposite direction from the diodes


128


and


130


.




The charging circuit


144


depicted in

FIG. 1

provides for the controlled, step-charging of the storage capacitor


120


. During one half cycle of the AC power source


106


, a current flows through the chokes


134


and


136


, the capacitor


132


and the diodes


128


and


130


to charge the capacitor


132


. The capacitor


132


is selected to be relatively smaller than the capacitor


120


(e.g., 0.047 microfarads (μF) versus 5 μF). On the next half cycle of the AC power source


106


, the capacitor


120


is charged and the voltage across the capacitor


132


increases the incoming half wave from the AC power source


106


so as to provide energy on the order of 2.7 microjoules to the storage capacitor


120


. Since the capacitor


120


requires more energy due to its relative size, the capacitor


120


can be provided with energy from both the incoming AC signal and the capacitor


132


in one cycle. On the next half cycle, the capacitor is charged again and delivers energy to the capacitor


120


again on the subsequent half cycle. Thus, the charge on the capacitor


120


is increased with each alternate half cycle using a pumping action.




When the capacitor


120


reaches the breakdown voltage of the sidacs


122


and


124


, the sidacs become conductive and therefore render the SCR


118


conductive. The capacitor


120


therefore discharges through the portion


116


of the ballast


108


to generate a high voltage in the portion


114


of the ballast. The large magnitude of the capacitor


120


discharges significantly more energy into the magnetic field of the ballast


108


as compared with a conventional HID lamp ignitor and therefore excites the ballast


108


to a relatively high degree. The highly excited ballast


108


, with its corresponding collapsing magnetic field, pushes the lamp into a discharge state and therefore a low impedance state so that the discharge state can be maintained by the normal AC power source


106


. The discharging capacitor


120


produces current flow which is in the same direction as the continued current flow produced by the collapsing field, and which is provided through the lamp as the SCR


118


is turned off by the instantaneous back voltage bias placed on the capacitor


120


by the same collapsing field energy. The resistor


152


can be connected in series with the SCR


118


to cause the peak of the high voltage pulse to be lower and the base (i.e., width) of the pulse to be longer. The resistor


152


limits the high voltage and therefore reduces dielectric stress to allow the use of lower cost magnetic components.




The ignitor


100


depicted in

FIG. 1

further comprises an HPS lamp starting circuit comprising a capacitor


146


connected in series with a resistor


148


and a sidac


150


or similar breakdown device. The resistor


148


is connected to the junction between the inductors


134


and


136


and the capacitor


132


. The ignitor


100


comprises a current-limiting resistor


152


in series with the parallel combination of the SCR


118


and the sidacs


122


and


124


.




The above-mentioned HID lamps should be provided with a disabling circuit such that, if the lamp fails to start, the disabling circuit would discontinue the hot or cold strike used to initiate the HID lamp. This feature is useful in prolonging the life expectancy of the ignitor, helps protect the ballast system, and provides the ability to apply HID ignitors to harsh and hazardous environments.




Accordingly, a need exists for a reliable means of disabling the ignitor portion of a HID lamp, and an accurate method to time when the disablement of the ignitor occurs. Further, a need exists for a power supply for proper operation of semiconductor devices used in the disabling circuitry, and a solid state contact in the lamp circuit that will not release sparks when actuated by the disabling circuit.











BRIEF DESCRIPTION OF THE DRAWINGS




The various aspects, advantages and novel features of the present invention will be more readily comprehended from the following detailed description when read in conjunction with the appended drawings, in which:





FIG. 1

is a schematic diagram of an exemplary existing ignitor;





FIG. 2

is a schematic diagram of a circuit having a HID lamp restrike function integrated with a disabling function in accordance with an embodiment of the present invention;





FIG. 3

is a schematic diagram of an universal sodium ignitor constructed in accordance with an embodiment of the present invention





FIG. 4

is a schematic diagram of a timer with an external trigger constructed in accordance with an embodiment of the present invention;





FIG. 5

is a schematic diagram of an analog trigger mechanism constructed in accordance with an embodiment of the present invention





FIG. 6

is a schematic diagram of a power supply with an advantageous ramp up operation constructed in accordance with an embodiment of the present invention; and





FIG. 7

is a schematic diagram of an isolated solid state switch mechanism constructed in accordance with an embodiment of the present invention.











SUMMARY OF THE INVENTION




One aspect of the present invention is to provide a reliable means to disable ignitor operation for operation in harsh and hazardous environments.




Yet another aspect of the present invention is to provide accurate method to time when the disable operation occurs.




Still another aspect of the present invention is to provide a novel method to trigger the start of the time interval.




Another aspect of the present invention is to provide a power supply for proper operation of semiconductor devices.




Another aspect of the present invention is to provide a solid state, normally closed contact that will give no sparks when actuated.




Another aspect of the present invention is to provide the ability to retrofit an existing HID sodium lamp with disable circuitry.




DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT





FIG. 2

depicts a disabling circuit


200


provided in accordance with an embodiment of the present invention. Disabling circuit


200


is provided to operate a normally closed triac


392


(

FIG. 7

) in order to disable the igniter


300


of

FIG. 3

of a HID lamp upon failure to start the lamp. By way of an example and as described below, the node


202


in the disabling circuit


200


can be provided in the ignitor


300


, as shown in FIG.


3


. This disabling feature is useful in prolonging life expectancy of the ignitor, helping to protect the ballast system, and providing the ability to apply HID igniters to harsh and hazardous environments by encapsulating the disabling circuit


200


and igniter


300


of

FIG. 3

in a can, for example, or any other appropriate encapsulating product.




With continued reference to

FIG. 2

, the disabling circuit


200


comprises a monostable timer


340


(FIG.


4


), a triggering circuit


350


(FIG.


5


), a power supply


360


(FIG.


6


), and an isolated solid state switch


380


(FIG.


7


). Accordingly, when power is applied to the ignitor


300


of

FIG. 3

, both legs (e.g., the hot restrike function


302


, and the standard pulse ignitor


304


) of the ignitor begin operation. This allows the power supply


360


to ramp up to a threshold voltage, thus initiating the triggering function of the trigger circuit


350


which, in turn, begins the timer


340


. Upon expiration of a pre-selected period of time (e.g., 180 seconds or any other appropriate period of time), the timer


340


activates the solid state switch


380


which, in turn, activates the triac


392


, thereby removing power from the ignitor


300


and disabling the ignitor


300


.




The ignitor


300


of

FIG. 3

produces two types of pulses, as mentioned above, a hot re-strike pulse generated by circuitry


302


and a standard pulse ignitor generated by circuitry


304


. The major difference between a standard ignitor


304


and a hot restrike ignitor


302


is that a restart ignitor produces a pulse which is higher in voltage and contains significantly more energy than a pulse generated by a standard ignitor (e.g. on the order of 700 volts). The hot re-strike ignitor is indicated generally at


302


and is a DC ignitor that charges and discharges in one direction only. The rectifiers


305


produce a DC level that increases with each successive half-cycle of the ballast (not shown) secondary voltage. Capacitor


306


is employed in a pumping arrangement to increase the voltage on capacitor


308


to preferably twice the peak open circuit ballast voltage. When the voltage on capacitor


308


reaches a sufficient level to break-over the semiconductors


310


, transistor


312


is gated on. The charge in capacitor


308


carries through the tap


314


of the ballast (not shown), thus creating a voltage transformation loop. This high current provided through the tap produces a large voltage on the secondary of the ballast across the sodium lamp. The secondary voltage of is sufficient amplitude such that under certain conditions, the sodium lamp hot re-starts essentially instantly.




With continued reference to

FIG. 3

, the regular ignitor


304


is an AC ignitor. It charges and discharges through the series combination of capacitors


316


and


317


, and resistor


318


in an alternating fashion. The voltage produced across capacitor


317


is sufficient to break-over semiconductor


320


. A current pulse is provided at least once per half-cycle in both directions through the tap


314


of the ballast (not shown). In addition, this current pulse preferably provides a high voltage pulse across the sodium lamp in the direction of the ballast (not shown) secondary voltage every half-cycle.




The series combination of resistor


322


and rectifiers


324


and


326


provide a means of storing DC energy in the ballast capacitor (not shown) to facilitate the hot re-start ignitor


302


of the lamp (not shown). Both ignitor legs


302


and


304


feed through the RF chokes


328


. If the current through these chokes is terminated, then the pumping action of the ignitor


302


and pulsing action of


304


ceases to function, thus enabling the triac to open at point


202


in FIG.


3


. Placing the triac


392


at node


202


in

FIG. 3

, thus enabling the triac


392


to de-activate, therefore producing the current disruption.




The triac


392


located with in the disable circuit


200


can be opened to cause the ignitor


200


to cease operating. The location of the disable circuit within the ignitor circuit is preferably at point


202


of FIG.


3


. This particular insertion point


202


is advantageous because it provides for the protection of the low voltage semiconductors in the disable circuit


200


by placing the circuit inside the RF chokes


328


and away from the two above-referenced ignitor pulses that vary from 3.5 KV to over 7 KV. The disable circuit


200


is self-contained within the same parameters and connections to which the ignitor


200


is subject. The disable circuit preferably maintains its connections internal to the ignitor


200


itself. Thus, the entire package can be configured to have only three external connections, that is, LAMP, TAP, and COM.




Another aspect of the invention is the selection of the appropriate length to allow the ignitor to function before it disables. Since the majority of all sodium lamps will re-ignite after approximately 90 seconds, the interval disable time period is selected to be at least twice this period (i.e., a 180-second disable interval). Accordingly, the timer includes a timing cycle of approximately 180 seconds, for example. In addition, there are primarily two modes of operation of the timer


340


: astable and monostable. An embodiment of the present invention employs the monostable mode which is a method by which a 555 timer is preferably provided. An RC time constant is employed to place the timer output at high for a given duration, set by the RC time constant, and then return the output to low.




However, the timer's timing cycle does not begin until an external trigger, such as the triggering circuit in

FIG. 5

, starts the operation. The trigger voltage generated by the triggering circuit preferably starts at a level greater than that of Vthresh (FIG.


4


), and then decreases below this level before rising above it once again. When the trigger voltage rises above the level of Vthresh, the timing cycle begins. The duration of the cycle is given by the following equation:






τ
:=

R
·
C
·

ln


(

Vcc

Vcc
-
Vth


)







τ
:=

1.1
·
R
·
C











wherein capacitor


342


=47 microfarads, t=180 seconds and resistor


344


=3.4 megohms (approx,) Resistor


344


is preferably 3.9 megohms which is the closest standard value. It is desirable to start the time duration immediately upon the application of power to the ignitor system. Accordingly, a trigger/control mechanism is needed to provide the means to start the timer operation. As described above, the three conditions employed to appropriately begin the operation of a timer


340


via an external trigger pulse


346


are:




1. Vtrig≧Vthresh during time


1






2. Vtrig≦Vthresh during time


2






3. Vtrig≧Vthresh during time


3






To achieve state


1


above, a pull-up resistor


358


is applied to the trigger pin


346


of the timer


340


. Thus, the voltage at the trigger pin


346


is on the order of Vcc. To achieve state


2


above, a transistor


348


of the trigger circuit


350


of

FIG. 5

is also connected to the trigger pin


346


. When gated, even for a short duration, the transistor


348


pulls pin


346


to ground. To achieve state


3


above, the transistor


348


is turned off. The pull-up resistor


358


allows the trigger pin


346


to rise to Vcc again.




The control of the transistor


348


gate signal is an important aspect of an embodiment of the present invention. Transistor


348


is controlled via the DC charge of capacitor


352


via resistors


354


and


356


. Resistor


356


provides a means for the gate to go to ground when no current flows through resistor


354


(i.e. a pull down resistor). Whittle Vcc charges to a steady DC level, so does capacitor


352


. Current flows through the resistor


354


and the capacitor


352


series combination, thereby tuning on the transistor


348


. The trigger pin


346


is therefore pulled to ground. When capacitor


352


has approximately reached the level of Vcc, it allows no more current to pass. This effectively turns off the transistor


348


. As mentioned above, transistor


348


turns off and the timer's trigger pin


346


rises to Vcc, thereby starting the timer's


340


timing cycle. An embodiment of the present invention employs a high pass filter via capacitor


352


and resistor


354


and a power supply as described in detail below (e.g., one that ramps up to its steady state), to directly supply the gate current needed in order to properly turn on and off the transistor


348


. When the power supply


360


ramps up, the high pass filter gates the transistor


348


. When the power supply maintains a steady state, the high pass filter provides no current to the gate of the transistor


348


. The gate is therefore pulled to ground via the resistor


356


and the transistor


348


is turned off.




The power supply


360


of

FIG. 6

is important to the application of the timer


340


described above. The power supply


360


has two characteristics that achieve proper operation of the timing circuit


340


. First, it has a steady state, regulated voltage that has at least the minimum required DC for proper operation of the timer (e.g., on the order of 4.2 volts). Second, the power supply ramp up to the steady state is of sufficient frequency that the high pass filter passes current to the transistor


348


, thus activating the trigger and timing cycle. A rectifying bridge


362


is preferably provided to gain DC current to the power supply regulating circuit


360


. A two-stage circuit is employed to ensure a high degree of regulation and the proper current draw through capacitor


364


which drops the open circuit voltage (OCV) of the ballast (not shown) from 400 V peak to about 10 V peak when measured at the diode bridge


362


. Resistor


366


is preferably provided across the output of the bridge


362


to ensure that enough current is drawn to produce the open circuit voltage and to discharge any residual charge left on capacitors


368


and


374


. There is no bandwidth limitation to the charge of capacitor


368


. Thus, whatever voltage peak is produced across resistor


366


, the capacitor


368


achieves this level in one cycle. In other words, the charge current to capacitor


368


is not regulated or limited by a resistor. The zener diode


370


has been placed across the output of the bridge


362


to provide over-voltage protection and pre-regulation of the second power stage. The low pass filter combination of resistor


372


and capacitor


374


gives the required ramp up on the voltage output of the power supply


360


. The charge frequency of capacitor


374


is fast enough to overcome the bandwidth limitation of the transistor control. The charge frequency is:








f=


1/(2*π*(


R


8


*C


6))=800 kHz.






Zener diode


376


has been placed across the output of the power supply


360


to regulate the steady state condition at no more than 6.2 VDC. This protects the timer circuit


340


from failure.




The timer


340


, the trigger circuit


350


, and the power supply


360


work in conjunction with each other to operate the solid state switch mechanism


380


illustrated in FIG.


7


. The switch mechanism


380


is employed to operate the triac


392


at point


202


of ignitor


300


. The switching mechanism substantially comprises a two stage opto-isolater


390


, and a triac


392


. The gate of the triac


392


is controlled by the output of the opto-isolator


390


. There are two opto-isolaters contained in one package, connected in a cascaded fashion; therefore, the state of the first device determines the state of the second.




The opto-isolater


390


has DC inputs on line


345


and solid state contacts that are normally closed. The typical state for the disable circuit


200


is to allow the ignitor to operate normally. However, upon expiration of the timer


340


, the control of the first of the opto-isolaters


390




a


is high, and the triac


392


is on. When the control goes low on line


345


, opto-isolater


390




a


has a shorted output, thus activating the input of


390




b


. By activating


390




b,


the output of


390




b


opens, thus allowing no current through the triac


392


, and therefore disabling the ignitor


300


. The triac


392


remains off until the input


44




390




a


goes high and once again activates the triac


392


.




The reliability of the disable feature is extremely consistent. Accordingly, the entire system is not sensitive to component variation, since the power supply


360


is regulated and the timer


340


is accurate. The largest concern is the tolerance of the components on the timer


340


portion. Timers can vary from lot to lot and the disable time interval may vary from ignitor to ignitor on the order of 5%, (i.e., typically about a 30-second difference between the fastest disable and the slowest disable). However, the design constraint of the timer


340


being twice the maximum re-strike (e.g., 180 seconds) time provides an ample buffer to overcome the tolerance issues of any timer circuit.




Additionally, it should be noted that the disable circuit


200


, as shown in

FIG. 2

, can be retrofitted onto any existing universal sodium ignitor circuit, as shown in

FIG. 3

, when the disable feature is placed at point


202


of the ignitor


300


. This allows further flexibility for the disable circuit in accordance with an embodiment of the present invention.




Although only several exemplary embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.



Claims
  • 1. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition comprising a three state signal occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit.
  • 2. A circuit as claimed in claim 1, said timer circuit receiving a triggering voltage from said triggering circuit and said power supply generating a threshold voltage at said timer circuit, wherein said pre-determined condition comprises a first state wherein said triggering voltage is greater than said threshold voltage, followed by a second state wherein said triggering voltage is less than said threshold voltage, followed by a third state wherein said triggering voltage is greater than said threshold voltage.
  • 3. A circuit as claimed in claim 1, wherein said power supply comprises a capacitive device coupled in series to a plurality of rectifying devices and operable to reduce the open circuit voltage of a ballast associated with said lamp, said rectifying devices coupled in parallel to a resistor and capacitor combination operable to charge to a selected voltage, and a low pass filter operable to ramp up to said selected voltage and achieve a steady state to provide said predetermined condition.
  • 4. A circuit as claimed in claim 1, wherein said triggering circuit comprises a triggering output to supply a trigger voltage to said timer circuit, a transistor coupled in series to said input, and a plurality of resistive devices and a capacitive device in parallel to said output to said timer circuit.
  • 5. A circuit as claimed in claim 1, wherein said gating circuit comprises a control input from said timer circuit to said gating circuit coupled in series to at least one resistive device, and said resistive device coupled in series to a plurality of isolating devices, and said isolating device coupled in series to a gating device via at least one resistive device.
  • 6. A circuit as claimed in claim 1, wherein said selectable period of time is 180 seconds.
  • 7. A circuit as claimed in claim 1, wherein said timer comprises a NE 555 timer.
  • 8. A circuit as claimed in claim 1, wherein said plurality of ignitor circuits comprises a 120 Hz pulse circuit, and a hot re-strike pulse circuit.
  • 9. A circuit as claimed in claim 1, wherein said power signal comprises a minimum voltage for proper operation of said timer circuit, and a minimum frequency of said power signal to allow said power signal to activate said triggering device via said timer circuit.
  • 10. A circuit as claimed in claim 9, wherein said minimum voltage comprises 4.2 Volts.
  • 11. A method for disabling at least one of a plurality of ignitor circuits within a lamp, said method comprising:generating a timing signal via a timer circuit after a selected period of time; operating a power supply to ramp up to a regulated steady state voltage for operation of said timer circuit; activating a triggering device upon receiving a selected voltage from said power supply to activate said timer circuit; providing a three state signal to activate said timer circuit; and initiating a gating device upon expiration of said selected period of time to terminate operation of said at least one of a plurality of ignitor circuits.
  • 12. A method as claimed in claim 11, wherein said activating step further comprises:receiving a triggering voltage at said timer circuit from said triggering device; generating a threshold voltage at said timer circuit; and initiating said timer circuit for said selected period of time when a pre-determined condition occurs characterized by a first state wherein said triggering voltage is greater than said threshold voltage, followed by a second state wherein said triggering voltage is less than said threshold voltage, followed by a third state wherein said triggering voltage is greater than said threshold voltage.
  • 13. A method as claimed in claim 11, wherein said selected period of time comprises 3.5 minutes.
  • 14. A method as claimed in claim 11, wherein said regulated steady state voltage comprises 4.2 Volts.
  • 15. A method as claimed in claim 11, wherein said initiating step further comprises:receiving an input at said gating circuit upon expiration of said selected period of time; and terminating signaling at said gating circuit thereby stopping signaling at said at least one of a plurality of ignitor circuits upon receipt of said input.
  • 16. A method as claimed in claim 15, wherein said input comprises a low input.
  • 17. A method as claimed in claim 15, wherein said stopping step further comprises creating an open circuit condition at said gating circuit via a triac component.
  • 18. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit; wherein said timer circuit receives a triggering voltage from said triggering circuit and said power supply generates a threshold voltage; wherein said pre-determined condition comprising a first state wherein said triggering voltage is greater than said threshold voltage, followed by a second state wherein said triggering voltage is less than said threshold voltage, followed by a third state wherein said triggering voltage is greater than threshold voltage.
  • 19. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit; wherein said power supply comprises a capacitive device coupled in series to a plurality of rectifying devices and operable to reduce the open circuit voltage of a ballast associated with said lamp, said rectifying devices coupled in parallel to a resistor and capacitor combination operable to charge to a selected voltage, and a low pass filter operable to ramp up to said selected voltage and achieve a steady state to provide said pre-determined condition.
  • 20. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit; said power signal comprises a minimum voltage for proper operation of aid timer circuit, and a minimum frequency of said power signal to allow said power signal to activate said triggering device via said timer circuit, and said minimum voltage comprises 4.2 Volts.
  • 21. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit; said gating circuit comprises a control input from said timer circuit to said gating circuit coupled in series to at least one resistive device, and said resistive device coupled in series to a plurality of isolating devices, and said isolating device coupled in series to a gating device via at least one resistive device.
  • 22. An ignitor disabling circuit coupled to at least one of a plurality of ignitor circuits within a lamp, said ignitor disabling circuit comprising:a timer circuit operable to generate a timing signal after a selected period of time, said timing signal being operable to disable at least one of said ignitor circuits; a power supply operable to provide a power signal to said timer circuit; a triggering circuit coupled to said timer and to said power supply, said triggering circuit operable to initiate said timer for said selected period of time upon occurrence of a pre-determined condition occurring at said timer circuit; and a gating circuit coupled to said timer, said gating circuit operable to disable said at least one of a plurality of ignitor circuits upon expiration of said selectable period of time at said timer circuit; said plurality of ignitor circuits comprises a 120 Hz pulse circuit, and a hot re-strike pulse circuit.
  • 23. A method for disabling at least one of a plurality of ignitor circuits within a lamp, said method comprising:generating a timing signal via a timer circuit after a selected period of time; operating a power supply to ramp up to a regulated steady state voltage for operation of said timer circuit; activating a triggering device upon receiving a selected voltage from said power supply to activate said timer circuit; and initiating a gating device upon expiration of said selected period of time to terminate operation of said at least one of a plurality of ignitor circuits, said activating step further comprising receiving a triggering voltage at said timer circuit from said triggering device; generating a threshold voltage at said timer circuit; and initiating said timer circuit for said selected period of time when a pre-determined condition occurs characterized by a first state wherein said triggering voltage is greater than said threshold voltage, followed by a second state wherein said triggering voltage is less than said threshold voltage, followed by a third state wherein said triggering voltage is greater than said threshold voltage.
  • 24. A method for disabling at least one of a plurality of ignitor circuits within a lamp, said method comprising:generating a timing signal via a timer circuit after a selected period of time; operating a power supply to ramp up to a regulated steady state voltage for operation of said timer circuit; activating a triggering device upon receiving a selected voltage from said power supply to activate said timer circuit; and initiating a gating device upon expiration of said selected period of time to terminate operation of said at least one of a plurality of ignitor circuits, said activating step further comprises receiving an input at said gating circuit upon expiration of said selected period of time; and terminating signaling at said gating circuit thereby stopping signaling at said at least one of a plurality of ignitor circuits upon receipt of said input, said stopping comprising creating an open circuit condition at said gating circuit via triac component.
CROSS-REFERENCE TO RELATED APPLICATION

The present invention claims benefit under 35 U.S.C. section 119(e) of a provisional U.S. Patent Application of Isaac L. Flory, and Christopher A. Hudson, entitled “Method and Apparatus for Disabling a Sodium Ignitor Upon Failure of Discharge Lamp,” Serial No. 60/246,594, filed Nov. 8, 2000, the entire contents of said provisional application being incorporated herein by reference. Related subject matter is disclosed in U.S. patent application Ser. No. 09/280,581, filed Mar. 30, 1999 now U.S. Pat. No. 5,972,449, the entire contents of said application being expressly incorporated herein by reference.

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Provisional Applications (1)
Number Date Country
60/246594 Nov 2000 US