CA1125839A - Emergency/normal lighting circuit for a gaseous discharge lamp - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A circuit is provided including a reactor for operating a fluorescent lamp from AC line voltage and including a high frequency inverter for operating the lamp from a battery upon failure of line voltage. The inverter also serves to start the lamp during normal conditions, that is, when AC
line voltage of sufficient value is available to the lamp.

Description

~ 5~39 58-BD-6336 The present invention relates to a circuit for operating a gaseous discharge lamp from -the AC mains as well as from an auxiliary DC source, and more particularly, to a circ~lit for operating such a lamp under normal corlditions at power frequency from an AC line source of electrical enexgy in conjunction with a reactor ballast, and, under emergency conditions, at high frequency from an inverter powered by an auiliary DC electrical energy source.
A power failure, no matter what the cause may be, amy very well jeopardize human life due to lighting system failure. There are therefore, many installations which require some type of emergency ligh-ting system which will automatically come into operation upon the occurrence of a power failure; the high efficiency of a fluorescent lamp makes it especially valuable for use in such a system.
Presently available emergency lighting systems are generally of the type using a transistor switching inverter and wherein a single fluorescent lamp, or group of lamps, is used both for normal AC operation of the lighting system 2Q and for the emergency system, a battery being used as the power source for energizing the transistor inverter and the lamp, or lamps, upon loss of AC line voltage. Ideally, such an inverter is of the high efficiency type and is provided with means for controlling its operation; such a system is disclosed and claimed in U.S. Patent No.3,921,005 dated November 18, 1975 - Watrous, assigned to the assignee of the present invention.
When attemps were made to apply an emergency lighting system, such as for example that described in U.S. Pat.No.
3Q 3,906,243 dated Sept/16/1975 - Herzog, assigned to the ~ZS~3~ 5~-BD-6336 assignee of the present invention, to fluorescent lamps in the size range of 20 watts and less for operation in the rapid start mode, the isolated secondary winding of the ballas-ts was found to have too low an impedance at high ~requency.
Designing this winding with a suficient~ hiyh impedance makes it large, with too high an open circuit voltage (causes rapid s~art lamps to instant start) and hence lossy.
Examining other ways of starting fluorescent lamps suggests the use of a manual starter, a gas-filled bi-metal starter or a solid-state equivalent. While the manual starter is compatible with a high frequency emergency inverter, where emergency lighting is needed, a manual starter is not desirable nor suitable. Both the gas-filled bi-metal starter and the solid state equivalent will act to short out the frequency inverter rather than start the fluorescent lamp in the emergency modeO This means that, if the fluorescent lamp could be started with the reactor, but without the normally employed starting methods, an emergency/
normal lighting system coula be developed for 20 watt or 2Q lower wattage lamps and as well as for the overseas market where, with the 220 V AC supply, reactor ballasts are employed for la~ps up to the 65 watt level~
It is desirable, therefore, to provide a lighting system wherein a high frequency inverter is compatible with a reactor ballast for operating a gaseous discharge lamp both from the AC mains, and upon the failure thereof, from an auxiliary DC source.
Accordingly, it is an object of the present to pxovide a lighting system including a circuit having a reactor for 3~ operating a gaseous discharge lamp during normal conditions from the AC mains, and having a controlled transistor switching inverter for starting the lamp during normal conditions and for starting and operating the lamp during j~ 58-BD--6336 emergency conditions: ie, when the AC line voltage has d~opped below a predetermined level.
In accordance with the present invention, there is provided a circuit for operating a gaseous dischar~e lamp from a source of AC line voltage, and al~ernatel~, from an auxiliary DC electric energy source. Means are provlded including a reactor for connection to such an AC line voltage source for operating the lamp at power frequency during normal conditions when the AC line voltage ls above a first predetermined level. Means are also provided in~
cluding an inverter connected to the DC electrical energy source for starting the lamp during normal conditions and for starting and operating the lamp during emergency con-ditions upon failure of the AC line voltage. The inverter supplies AC electrical energy to the lamp at a frequency substantially higher than the power frequency.
The accompanying drawing is a detailed schematic re-presentation of the preferred embodiment of the circuit of the present invention.
2Q In accordance with the present invention and referring now to the drawin~l there is shown a circuit for operating a gaseous discharge lamp from a source of AC line voltage and, upon the failure thereof, from an auxiliary source of DC electrical energy. Means are provided including an inverter lO connected to a source of DC electrical energy such as battery 14 of starting the gaseous discharge lamp, such as fluorescent lamp 12, during emergency conditions, inverter 10 supplying AC electrical energy to the lamp 12 at a frequency substantially higher than the AC line power frequency. Means are also provided including a reactor 16 arranged for connection through a pair of input terminals l and 2 to a source of AC line voltage, such as for e~ample ~z5~3g 53-~D-6336 220 volts, for operating the lamp 12 at line power frequency, for example, 50 Hz, during normal conditions: that is, when the AC line voltage is above a first predetermined leve~.
Emergency conditions are hereby defined to be when the ~C
line voltage falls below a second predetermined level.
Inverter 10 is of the tuned type and includes a pair o transistors QA and QB capable of operation in a low-loss switching mode. Means are providea enabling the transistors to operate in the low loss switching mode and includes inductor Ll, a buffer inductance, connected serially with battery 14. A first transformer Tl serves to couple the inverter 10 wi~h the lamp 12 and is resonated with capacitances C101 and C102 to set the operating frequency of the inverter and to establish a sinusoidal output voltage. Inductor Ll is electxically connected at point 22 with a center tap on primary winding P of transformer Tl. Means are provided for controlling the inverter 10 and which takes the form of a controller 20, in the preferred e~bodiment, a ten pin integrated circuit (IC). Further details ~f this integrated circuit controller may be held by above reference to U.S.
Patent No. 3,921,005 - Watrous, assigned to the assignee of the present invention. Controller 20 includes means supplying base drive for switching transistors QA and QB at zero collector voltage: tha-t is, when the instantaneous voltage across capacitor C101 is zero. As the primary voltage across transformer Tl varies at fundamental frequency, the voltage at point 22 and hence across inductor Ll varies at twice the fundamental frequency. The current through Ll is DC with a second harmonic component. This same current 3Q is alternately carried by the two transistors QA and QB.
~hile the transistors are required to switch collector current, they do so at essentially zero collector voltage ~z5~3~ 58-BD-6336 with a resultant low power dissipation.
Means are included providing timing information to the controller 20 for effecting switching of the respective transistors QA and QB is step with the natural reso~ant frequency of the inverter and takes the Eor~l oE an ~-uxiliar~
winding S2 magnetically coupled with the primary winding P of first transformer Tl. Thus, controller 20, and more specifically, a zero crossing detector set circuit therein, tracks the resonant frequency of first transformer Tl and insures that transistor switching occurs when the voltage across capacitor C101 is zero.
Higher efficiency can be achieved in inverter 10 by making the base drive of the respective transistors pro-portional to the collector current thereof. To this end there is included means providing a feedback current to the controller 20 to effect transistor base drive proportional to transistor collector current, which in the preferred embodiment, takes the form of a feedback transformer T2.
Transformer T2 has a feedback winding D magnetically coupled to the respective collectors of the transistors QA and QB
through a pair of windings A and B, respectively. Thus, the power consumed by the controller 20 can be limited to that required to start and control the oscillation of the inverter 10.
A high leakage reactance transformer T3 is provided for connecting the inverter circuit 10 to the 220 volt 50 Hz line voltage source. Circuit means are provided for monitoring the AC source voltage and for coupling the secondary winding S of high reactance trans~ormer T3 with a non-linear load during one half cycle of the AC source voltage to supply charging current for battery 14. Half-wave charging current is supplied to the non-linear load, ~583~ 58-BD-6336 bat-tery 14, through diode D101 and is limited in magnitude by the reactance of the transformer T3. Because of this transformer reactance, the sinusoidal voltaye of the terminals of winding S is clamped at the battery voltage when D101 conducts. On the alternate half c~cle, dlode ~103 conductors halfwave current through indicator lamp 24 and the dual-prong battery plug 26. The battery must be plugged in and the 220 volts AC available to energize lamp 24 in-dicating that the battery 14 is charging. Using the alternate half cycle reduces the volt-amp rating of the transformer T3.
For monitoring AC source voltage, means are provided for coupling secondary winding S of transformer T3 with a linear load during an alternate half cycle. To this end, during the half cycle alternate from that in which the battery 14 is charge, capacitor C104 is charged through diode D102.
This provision of a single secondary windings S associated with transformer T3 for providing, in a substantial nonin-teracting manner, a voltage proportional to the AC voltage and for providing energy to charge battery 14 is disclosed 2Q and claimed in U.S. Patent No. ~ 5C~3 dated ~e~u4~y~/iq~ and is assigned to the assignee of the present invention. The resultant DC voltage is connected to pin 7 of controller 20 through a linear load comprising resistor divider R104 and R105. The DC voltage at terminal 7 is proportional to the average value of the 50 Hz supply voltage and is not influenced by the aforesaid clamping action of the ~attery. A zener diode D120 is connected in circuit between diode DlQ2 and capacitor C104 as shown to prevent the battery voltage from battery 14 from keeping 3Q inverter lQ biased off. Furthermore, a heater winding H is provided on transformer T3 for heating filament 27 of lamp 12 for assisting in starting the lamp.

~Z5B3~ 58-BD-6336 Controller 20 includes means for turning on the inverter lQ when the AC line voltage is below the second predeter-mined level and for turning off the inverter 10 when the the AC line voltage is above the first predetermined le~el.
To accomplish these ends, controller 20 also includes a first sensor (in the form of an AC voltage inhibit subcircuit) ~or sensing the voltage of the AC line source and a second sensor (in the form of a low battery ~oltage inhibit subcircuit~ f~r sensing the DC battery voltage and includes logic means (in the form of a start-stop logic subcircuit) combining the .-outputs of the first sensor and the second sensor to enable inverter 10 when the battery voltage is above a predeter-mined level and the AC voltage is below the second pre-deter~ined level and to disable the inverter when the battery voltage is below a predetermined level or the AC line voltage is above first predetermined level.
Operation of the circuit including the inverter 10 during emergency conditions will now be discussed. Assuming that the inverter 10 is enabled to run, controller 20 supplies a small base drive signal to one of the transistors

2~ QA and Q~. Assuming further that this base drive is applied to QA, transistor QA turns on and current starts to flow through Ll, the center tap of the primary P of transformer Tl thence through P and through the A winding of feedback transformer T2, to transistor QA and thence back to the battery 14. The base drive originally supplied to tran-sistor QA is augmented by a current flow from winding D of feedback transformer T2 to the controller 20 to exit from pin 1 thereof ~hence to flow through the base of transistor QA. This base drive is proportional to the collector current 3Q of transistor QA and is designed to be adequate to keep the transistor in saturationO
At some volt-second product, feedback transformer T2 ,~

~5~3~ 58-BD-6~36 saturates sharply, suddenly reducing the output current of winding D thereof thereby reduciny the base drive to tran-sistors QA. A sudden rise in collector-emitter voltage on transistor QA sharply reduces the rate of current rise in this DC circuit. This change in collector current with respect to time reverses the polarity of the S2 winding o transformer Tl and hence the polarity of the voltage on pins

3 and 4 of controller 20. This reversal of polarity signals the controller 20. This reversal of polarity signals the controller to change the base drive from transistor QA to transistor QB.
Controller 20 now applies a small amount of base drive through pin 9 to the base of transistor QB, and simultaneously connects the base of QA to the emitter thereof to hasten the turnoff process of transistor QA. Transistor QB starts to conduct as a result of this small base drive signal from the controller and current flows through winding B of feed-back transformer T2 to induce a current in winding D thereof and this current is supplied to the controller 20. Controller 20 now supplies th;s current as base drive out of pin 9 to the base of QB; thus the base drive of QB is proportional to the collector current thereof such that the transistor is kept ïn saturation.
The P winding of transformer Tl has some leakage re-actance and becomes an oscillating system with capacitor C101. This oscillating system goes through the next half-cycle and forces the current flowing through winding B of feedback transformer T2 toward zero and thus the base drive of transistor QB is also reduced. When the ~-oltage across 3Q winding P of transformer Tl, and thereby the voltage on winding S2 of that transformer, reaches zero, this event is signaled to the controller 20 which again switches the base ~ 5~3~ S8-BD-6336 drive circuitry to transistor QA from ~ and connects the base of QB to the emitter thereof to hasten the switching off of transistor QB. The circui-t is then ready to go through the next hal~-cycle with ~A conducting.
If switching could be accomplished in absolute zero time, the above described circuit operation would be entirely correct. However, normally the switching is accomplished in periods of less than one microseco~d and the current flow from battery 14 is essentially at a constant level with a small ripple content. ThiS ripple content is determined by the inductance of Ll which adds or subtracts from the battery voltage as applied to the tap of the primary P of transformer Tl. It is this inductor Ll which adjusts the voltage at point 22 in such a way that the transistors may be switched at zero collector voltage. As long as this inductance Ll has a value exceeding a critical value, this circuit will function as described. In the event that both transistors QA and QB are in the "off" state, the rate of current change in Ll forces the voltage thereacross to a value where zener diode D104 starts conducting to limit the voltage applied to the circuit. This clipping action rapidly reduces circu.it efficiency and hence is an operational mode to be avoided. Such clipping action can occur momen-tarily during the starting process or when the inverter is turned off and under these conditions represents an acceptable design operating condition.
The load for the inverter 10 including lamp 12 is connected to a winding Sl of transformer Tl. For fluorescent emergency lighting purposes, the ballast.ing is done by 3Q capacitors C102 which determine the load current th~ough the lamp 12. This capacitance in conjunction with C101 and inductance TlP determine the operational frequency of the ~S~3~ 58-sD-6336 system (the inductance of the P winding and a capacitance of C101 determine the oscillating frequency when Sl is unloaded). A double capacitive ballast system is used ~o reduce the voltage across a single unit thus to enhance the reliability of the complete system. The voltaye output o the inverter circuit is high enough to instant start 40 watt and 65 watt rapid start lamps under fairly adverse cOndi~ions~
~ s hereinbefore stated, charging of battery 14 is accomplished from winding S of 50 Hz transformer T3. This lQ is the same winding that applied DC energy to the indicator lamp 24. Current flows from the finish of winding S to the plus terminal of the battery 14 thènce through diode D101 and to the start of winding S. In the alternate half-cycle, current flows from the start of winding S through diode D103 to the lamp 24 thènce to the two-prong plug 26 and on to the finish of winding S of transformer T3. If the battery is not plugged in, the indicator lamp is not energized signifying that the system needs attention. Also, if the indicator lamp or its associated circuit becomes defective 2a. (open or shorted~, the main charging cycle for the battery is uninterrupted but the lamp 24 does not come on again, therefore signifying that the syatem requires attention:
the system however remains operational. In the event that the battery 14 is not connected in circuit and line voltage is exceedingly high, there exists the possibility that this voltage would be applied directly across pins 3 and 10 of the controller 20. Such a high voltage could be destructive to the IC; taking advantage of the current limiting charact-eristic~ of the winding S, zener diode D104 conducts so as 3Q to clip the peaks of this vol-tage wave through inductor Ll thereby to protect the IC controller 20. This means th~t the zener diode DlQ4 must be sized so as to dissipate ~Z5B~9 58-~D-6336 this expected energy.
Winding S of transformer T3 also supplies a half-wave rectified signal over a diode D102 and a zener D120 to filter capacitor C10~ and voltage divider network R10~ and R105 thence to apply a signal to pin 1 of con~rol.ler 20. ~
this half wave rectified voltage decreases with decreasiny the voltage, it finally reaches a point where the controller 20 is allowed to function; this is the inverter turnon point.
Because of the nature of the half-wave rectified signal and the differential in the IC controller 20, a hysteresis is inherent in the IC operation. Thus, the inverter "turn off" point as controlled by the AC line voltage will be higher than the inverter "turn on" point. By ajusting the ratios of R104 and R105, either the inverter "turn on" or "turn off" point may be controlled over quite a wide range;
however, both inverter "turn on" and "turn off" points may not be separately controlled because of the relatively fixed value of this built-in bysteresis. DC battery voltage or charging transformer winding voltage is applied between pins 3 and 10 of controller 20. This same voltage is applied across voltage divider R102 and R103 to pin 5 (second sensor~
of the IC controller 20. When the voltage at pin 5 drops below a value determined by the construction of the IC, the controller 2Q stops driving transistors QA and QB thus shuttîng down the inverter 10. This voltage is normally set at approximately one half of the nominal battery voltage but it may be adjusted by the ratio of resistors R102 and R103.
A certain amount of hysteresis is implemented in the way this control function is done in the IC controller. This hysteresis provides clean on/off switching of the inveter.
After the inverter switches off, the voltage rises causing it to turn on again. This provides repeated flashing of the LZ5~339 58-BD-6336 fluorescent lamp which in turn indicates that the battery is discharged. ' As stated above, in the event that -the battery i5 not connected, the voltage across pins 3 and 10 o~ controller 20 will rise to a point which is the peak of the AC WaVQ yen-erated in winding S of 50 Hz transformer T3. This voltage might be excessive for the integrated circuit and therefore, when the voltage across pins 3 and 10 of controller 20 exceeds approximately 30 volts, an internal regulator in la the controller 20 shuts down the function of this controller in such a way as to minimize the voltage on variGus com-ponents of this integrated circuit. Thus, the application of too high a voltage to this inverter will inhibit its operation. This enhances the reliability of the sys-tem in that it distributes electrical stxess better in the in-tegrated circuit. Since the voltage occurring during operation across the transistors QA and QB is double the DC
battery supply voltage, by shutting off these transistors under abnormally high voltage conditions, the voltage is 2Q reduced simply to battery voltage, reducing the probability that the transistors QA and QB might fail under such highly abnormal conditions. If the voltage across the battery 14 rises above the zener voltage of D104, zener di`ode DlQ~ starts to conduct and voltage regulation will be accomplished by means of the inherent impedence of winding S of transformer T3. The voltage applied to the circuit is this limited to a safe value under quite severe over-Yoltage conditions. In the event the voltage continues to xise becau5e o~ a wrong voltage applied to the primary winding P o~ transformer T3 and with no battery ~n circuit, the most pr~bable mode of failure of zener diode ~104 is to short and this then crowbars the DC supply voltage to the ~5~3~ 58-BD-6336 inverter.
Operation of the circuit will now be discussed for normal conditions; that is, when the AC line voltage is above a first predetermined level. Assuming that ~C line voltage has already been applied to input terminals 1 and 2, a switch 28 is closed thereby allowing line voltage to be applied across the lamp 12 through reactor 16. Since no push-to-start button or voltage breakdown type of starting device has been supplied for startiny lamp 12, lQ in accordance with the present invention, means are provided for overriding the inverter controller for turning on the inverter to start the lamp during such normal conditions and for turning off the inverter after the lamp is operating from the AC line voltage. In the preferred embodiment this includes lamp voltage monitoring means in the form of a voltage breakdown device such as zener diode D122 connected serially with a pair of diodes D124 and D126 and a resistor RlQ7 across the lamp 12. ~ light emitting diode D130 is also connected serially with -this string and a capacitor 2Q ClQ`7 is connected in parallel with the diode string. The application of line voltage across the lamp 12 causes ~ener diode D122 to conduct thereby allowing the LED D130 to become operative. Photons emitted from the LED D130 effect the turning on of a phototransistor QP thereby allowing the discharge of t~le line monitoring capacitor C104 through a current limiting resistor R108. Since the integrated circuit controller 20 sees a loss of line voltage at pin 7, the inverter i5 allowed to turn on thereby effecting starting of the lamp 12. Upon lamp starting, after lamp voltage 3Q drops to the normal run level, zener diode D122 stops con-ducting there~y ef~ecting the turning off of the ~ED and the phototransistor QP. Means are provided for assuring ~ ~ ~ 5 ~ ~ 58-BD-6336 operation of inverter 10 for a predetermined time after lamp voltage reaches a normal run level. In the preferred embodiment, this includes RC timing means, including resistor Rl09 and capacitor C104, which functions to provide a time delay of predetermined value. Capacitor Cl04 then gradually charges over a charging resistor DlO9 and after a short dela~, pin 7 of the controller 20 senses an appropriate voltage and turns off the inverter lO. The choice of value of resistor RlO9 in combination with capacitor Cl04 may be varied to effect longer or shorter charging time of the capacitor.
Thus, the amount of delay time before the inverter turn off may be controlled to assure the adequate hot-spotting of the lamp to insure its long life. It should be no-ted that the LED D130 and the phototransistor QP form an optocoupler which advantageously may be provided in the form of an integrated circuit.
As can be seen, lamp 12 may be turned on and off by opening and closing switch 28 without activating the inverter lQ except for starting. The inverter therefore serves to 2Q start the lamp during normal conditions and also to start and operate the lamp during emergency conditions: upon failure of the AC line voltage.
With the arrangement as shown in the drawing, a lamp socket may function as a safety disconnect lampholder. As shown, means are provided in the circuit for connection to lamp 12 and include a first pair of terminals 32, 32l and a second pair of terminals 34, 34'. Terminal 32' is con-nected to ground through input terminal 2. When lamp 12 is removed from the circuit, the lamp voltage monitoring 3Q subcircuit including zener diode D122 is open circuited since its connection to ground through terminal 32 and lamp filament 30 is broken. ~s a result, during normal ~IL2~33~
58-BD-633~

conditions, (when ~C line voltage is above a predetermined level) the inverter 10 will not turn on. As a further example, if the filament 27 end only of the lamp 12 is removed from the circuit, an individual coming lnto con~ac~
with the lamp pins connected to filament 27 will eff~c~-tuall~
contact ground since filament 30 is grounded; no electrical shock will result. If the filament 30 end only of lamp 12 is removed from the circuit, the inverter will not run and an individual contacting the lamp pins connected to lQ filament 30 will receive no electrical shock since the lamp will not ionize without starting assisting from the inverter.
Should lamp 12 be removed partially from the circuit during emergency conditions (when inverter 10 is operational), an individual contacting the lamp pins connected to filament 30 will be protected from severe electrical shock due to the fact that winding Sl of transformer Tl has been designed with a very low capacitance to ground thereby limiting current flow. This reduced capacitance to ground has been accomplished primarily by keeping the winding physically 2Q small and as electrically decoupled as possible from the outer case and other windings.
As sta~ed hereinbefore, the control circuit 20 may be fabricated as a single, monolithic, integrated circuit.
In this form, the use of slaved current sources is particularly practical. In the embodiment described in the aforementioned U.S. Patent No. 3,921,005 dated November 18, 1975, the current consumption and hence, power dissipation, in the controller 20 is essentially independent of battery voltage over the operating range. Furthermore, the control 3Q circuit can be matched to different power level inverters by scaling the currents in the control circuit.
The lighting circuit shown in the drawing has been ~ 15 -5i t33~ 58-BD-6336 , , constructed and has operated satisfactorily with components having the following value:
Transistors QA, QB D44C10 Trans:Eormer Tl Primary winding P, 50 turns, .0253" wire Load winding Sl, 1130 turns, .0063" wire Feedback winding S2, 3 turns, .0063" wire lû Transformer T2 Collector windings A and B, 6 turns ~0126" wire Output winding D, 240 turns, 0071" wire Transformer T3 Primary winding P, 3332 turns, .0045" wire Secondary winding S, 290 turns, .OQ80" wire Heater winding H, 66 turns, .01006" wire Inductor Ll 73 turns, ~032" wire Lamp 12 F40 T12 7~ RS
Battery 14 7 cells, 1/2 D, high temp Ni - Cd Reactor 16 KNOBEL #40-5340 Resistor R101 15K ohm 1/4 W
(all 5%1 R102 22K ohm 1/4 W .
R103 22K ohm 1/4 W
R104 lOOK ohm 1/4 W
R105 220K ohm 1/4 W
R107 lOQK ohm 2 W
R108 608K ohm 1/4 W
RlQ9 18K ohm 1/4 W

.

3i'3 Capacitor C101 .22 uf 50 V AC, 10 C102 (2) 5100 pf ~00 V, 5%
C104 2.0 uf 50 V, 20~
C105 .01 uf 100 V, 20%
C107 100 pf 500 V AC, 10 Diode D101, D102, D103, D126, D124 IN 4004 lA., 400 V
Diode Dlll, D115 DA 1701 .24, 25 V
Zener Diode D104, D120 20 V, 1 W 5%
lQ Zener Diode D122 150 V DC, 1 W, 5 Phototransistor QP ) IC Photocoupler HllA5 (GE) Control circuit 20 has been built and has operated satisfactorily in hoth discrete circuit form and as a monolithic IC; See U.S. patent No. 3,921,005 dated November 18, 1975 for details.
The illustrated embodiment was designed to operate a 4Q W rapid start fluorescent lamp from a 220 V, 50 Hz source an, in the emergency mode at 5500 Hz, from battery 2Q (for 100 minutes). This circuit has also successfully operated a 65 watt rapid start fluorescent lamp. Another circuit has been built and has operated a 20 W rapid start lamp from a 120 V, 60 Hz AC source and from a battery;
this circuit had the same component values as above, except for the following:
Resistor R107 47 K ohm, 2 W
RlQ9 10 K ohm, 1/2 W
Transformer T3 Primary P 1690 turns, .0063"

dia. wire Secondary S 340 3Q turns. 0063" dia wire H 80 turns. 0126" dla. wire Zener Dioae D122 100 V, 1/2 W
I

~ 17 -~ ~ S ~ ~ 58-BD-6336 ~ IC Photocoupler - HllA5 (GE) Phototransistor QP ~
Capacitor C107 .001 uf, 200 V
C108 (not shown) .001 u~, 50 V (between base of phototransistor and pin 10 of controller 20) Reactor 16 89G988 (GE) While an embodiment and application of this invention have been shown and described it will be apparent to those lQ skilled in the art that modifications are possible without departing from the inventive concepts herein described. The invention, therefore, is not to be restricted except as is necessary by the prior art and the spirit of the appended claims.

Claims (5)

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

1. A circuit for operating a gaseous discharge lamp, the circuit comprising:
means including a reactor arranged for connection to a source of AC line voltage for operating the lamp at power frequency during normal conditions when the AC line voltage is above a first predetermined level;
means including an inverter connected to a source of DC electrical energy for starting the lamp during normal conditions and for starting and operating the lamp during emergency conditions when the AC line voltage is below a second predetermined level, the inverter supplying AC electrical energy at a frequency substantially higher than the power frequency;
means for controlling the inverter including a first sensor responsive to a signal related to AC line voltage for turning on the inverter when the AC line voltage is below the second predetermined level and for turning off the inverter when the AC line voltage is above the first predetermined level; and overriding means for turning on the inverter to start the lamp during normal conditions and for turning off the inverter after the lamp is operating from the AC line voltage;
the overriding means including means for monitoring voltage across the lamp and including means for effecting inverter turn-on when voltage across the lamp is above a predetermined level and for effecting inverter turn-off when the lamp becomes operational and the voltage thereacross is below another predetermined level.

2. The circuit of claim 1 wherein the means for monitoring includes a voltage breakdown device which upon conduction allows the activation of an optocoupler to effect removal of the signal from the first sensor thereby to turn on the inverter.

3. The circuit of claim 1 further comprising means for connection to the lamp including first and second pairs of terminals, one of the first pair of terminals being arranged for connection to ground, the voltage monitoring means being connected at one end to the second pair of terminals and at the other end to a second of the first pair of terminals such that, during normal conditions, when the lamp is removed from contact with the first pair of terminals, the voltage monitoring means is open-circuited and cannot function to effect inverter turn-on, thereby serving as a lamp safety disconnect.

4. A circuit for operating a gaseous discharge lamp, the circuit comprising:
means including a reactor arranged for connection to a source of AC line voltage for operating the lamp at power frequency during normal conditions when the AC line voltage is above a first predetermined level;
means including an inverter connected to a source of DC electrical energy for starting the lamp during normal conditions and for starting and operating the lamp during emergency conditions when the AC line voltage is below a second predetermined level, the inverter supplying AC electrical energy at a frequency substantially higher than the power frequency;
means for controlling the inverter including a first sensor responsive to a signal related to AC line voltage for turning on the inverter when the AC line voltage is below the second predetermined level and for turning off the inverter when the AC line voltage is above the first predetermined level;
overriding means for turning on the inverter to start the lamp during normal conditions and for turning off the inverter after the lamp is operating from the AC line voltage, and means for assuring inverter operation for a predetermined time after a lamp voltage reaches a normal run level.

5. The circuit of claim 4 wherein the means for assuring includes RC timing means providing a time delay in restoring the signal to the first sensor whereby inverter operation is assured for a predetermined time after lamp voltage reaches the normal run level.