US3659146A - Auxiliary lighting system for use particularly with high pressure metal vapor lamps - Google Patents

Abstract

A stand-by lighting system for a high-pressure metallic-arc lamp circuit is provided which includes an auxiliary light source, a solid state switch for the emergency light, a switch control circuit for operating the switch in response to a predetermined arc lamp circuit condition in which the arc lamp fails to effectively light when normal operating voltage is applied thereto. The control circuit includes a relaxation oscillator for producing triggering pulses for effecting conduction of the solid state switch and energization of the auxiliary light when the above arc lamp circuit condition occurs.

Description

United States Patent Munson [451 Apr. 25, 1972 54] AUXILIARY LIGHTING SYSTEM FOR 3,309,563 3/1967 McKienzie ..31s ss USE PARTICULARLY WITH HIGH 3,486,068 12/1969 Dunn et al. ..315/88 PRESSURE METAL VAPOR LAMPS Primary Examiner-Ronald L. Wilbert [72] Inventor: Robert D. Munson, Jennings, Mo. Assistant E i r-V. P. McGraw [73] Assignee: Emerson Electric Co., St. Louis, Mo. Atwmey stanley Garber and wllham Meara [22] Filed: Feb. 20, I970 [57] ABSTRACT [21] Appl. No.: 13,119 A stand-by lighting system for a high-pressure metallic-arc lamp circuit is provided which includes an auxiliary light source, a solid state switch for the emergency light, a switch [52] US. Cl ..315/92, 315/93, 315/136 control circuit for operating the switch in response to a [51] Int-Cl 39/10 Hb41/46 redetermined arc lam circuit condition in which the are [58] Field oiSearch ..315/88, 127, 129, 135, 136, P

3 1 5/1 19 91 92 82 307/305, 317/3] lamp falls to effectlvely light when normal operatlng voltage is applied thereto. The control circuit includes a relaxation oscillater for producing triggering pulses for effecting conduction [56] References Cited of the solid state switch and energization of the auxiliary light UNITED STATES PATENTS when the above are lamp circuit condition occurs.

3,517,254 6/1970 McNamara ..3 /91 26 Claims, 4 Drawing Figures i i l /50 /4 /5z ma /28 4 26 H .6 I 04 /2u I 0a Patented April 25, 1972 3,659,145

2 Sheets-Shoat l 20 I /7 /9 /5 K W AUXILIARY LIGHTING SYSTEM FOR USE PARTICULARLY WITH HIGH PRESSURE METAL VAPOR LAMPS BACKGROUND OF THE INVENTION This invention relates to lighting systems and more particularly to auxiliary lighting means for a main lighting system.

In some lighting systems it is highly desirable or necessary to provide auxiliary lighting means upon failure of a main lighting source. For example, when a momentary electric power failure occurs in a lighting circuit containing a high pressure, metallic vapor, arc lamp, such as a mercury arc lamp, the lamp is extinguished upon the occurrence of the power outage and will not restart on the normal operating voltage when power returns to the lighting circuit unless or until the lamp has significantly cooled. The lamp cooling time necessary for restarting depends generally upon the type and size or rating of the lamp, and temperature conditions, and is generally of considerable duration, for example, several minutes. Momentary power outages are not uncommon occurences and may happen, for example, because of the tripping of circuit breakers as a result of current surges due to lightning, momentary overloading conditions, etc. The lack of light during such a cooling period of a lamp would be highly undesirable or intolerable in may lighting applications.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a novel lighting system containing a main lamp and wherein auxiliary lighting is automatically provided whenever the main lamp fails to light when power is supplied thereto.

Another object is to provide stand-by lighting means for a lighting circuit having an arc lamp therein wherein an auxiliary light source is automatically controlled to provide light during the cool-down period of an arc lamp following a momentary power outage, and wherein the auxiliary light source is automatically turned out in response to the restarting of the arc lamp.

Still another object is to provide stand-by lighting means of the abovementioned type wherein solid state components can be utilized, and the necessity for electro-mechanical devices, such as relays and the like, can be obviated.

These and other objects and advantages of the present invention will be apparent from the following description and accompanying drawings.

In accordance with one aspect of the present invention, auxiliary lighting means for a circuit having a main light source is provided which includes an auxiliary light source, switch means for controlling the energization of the auxiliary light source, and control circuit means responsive to the failure of the main light source to start when power is supplied thereto for operating the switch means to effect energization of the auxiliary light source the control circuit means including an impedance device connected electrically in series in the main light circuit, voltage sensing means for sensing a voltage across the impedance device and means for supplying a signal to the switch means in response to a change in voltage across the impedance device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating one embodiment of an auxiliary lighting system according to the present invention;

FIG. 2 is a schematic diagram of an auxiliary lighting system 2 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 of the drawings, there is shown a main lighting system or circuit 10 including a main light source 12, shown as a gas-discharge or are lamp, connected to an AC. voltage source 14, and an auxiliary or stand-by lighting circuit, indicated generally at 16.

In the main lighting circuit 10, the lamp 12 is connected by a pair of voltage supply leads l7 and 18 to source 14 through an arc lamp ballast, shown as a conventional ballasting reactor 19, and a manually operated light switch 20. The lamp 12 may be, for example, a high pressure metallic vapor arc lamp such as a conventional mercury arc lamp. One well-known type of mercury arc lamp includes mercury and argon in a quartz burner. As is well-known, some form of ballasting, such as obtained by reactor 19, is needed to limit current flow in the main circuit 10 because of the voltage and current charac teristics of an arc lamp circuit.

As previously mentioned herein, a high pressure are lamp, such as lamp 12, requires aconsiderable amount of restarting time or cool-down time. For example, if the electric power supplied to lamp 12 from source 14 was interrupted for even a short time, such as a fraction of a second, the lamp 12 would not normally restart on its normal operating voltage for several minutes after the operating voltage has been re-applied. Such power interruptions may occur, not only because of lightning and overloading conditions, but also, because the light switch 20 may, for example, be inadvertently operated in some cases.

The auxiliary circuit 16 automatically provides light during the above are lamp cool-down periods as well as when the lamp l2 permanently fails or burns-out. The circuit 16 is shown in FIG. 1 including an auxiliary light source circuit, indicated generally at 21, which includes an auxiliary light source shown as an electric lamp or bulb 22 connected in series with a lamp switch 24 across the AC. supply leads l7 and 18. The lamp 22 may be of any suitable type, preferably of the quick starting type, for example, of the incandescent type. The switch 24 of circuit 20 is shown as a solid state or semiconductor type switch illustrated as a silicon controlled rectifier (SCR) type thyristor. Switch 24 has its main terminals or cathode and anode connected in series with lamp 22, and its control or gate electrode, indicated at 24g connected to a switch control circuit, indicated generally at 26, and which controls the actuation or operation of switch 24 by providing control signals therefor in response to predetermined conditions in the main lamp circuit 10, as will be explained in detail hereinafter.

The control circuit 26 includes condition sensing means shown as a voltage divider 27 having a pair of sensing resistors 28 and 29 connected in series with each other across the arc lamp l2, and a trigger or gating circuit 30 connected to the divider for supplying signals to the gate circuit of rectifier 24 to control the conduction of the rectifier. The trigger circuit 30 is shown as a relaxation oscillator which includes a capacitor 31 and a switch 32 that is shown as a bilateral semiconductor switch, such as a diac. Capacitor 31 is connected in series with the switch 32 across the primary winding 34 of a transformer 35 that has a secondary winding 36 connected between the gate and cathode of the silicon-controlled rectifier 24. The capacitor 31 is also connected across the resistor 29 through an adjustable resistor 38 so that the trigger circuit 30 is responsive to the voltage drop across resistor 29. Resistor 29 provides an input signal to the input circuit of the oscillator 30, and the output circuit of the oscillator is coupled to the switch actuating or gate circuit of the silicon-controlled rectifier 24.

When the voltage drop across resistor 29 is at a predetermined magnitude the capacitor 31 charges to the breakdown voltage value of diac 32 to fire or trigger the diac to its conducting or low impedance state on each half cycle of the supply voltage. This produces triggering pulses across secondary winding 36 which is connected between the gate and cathode of the rectifier 24 to effect triggering of the rectifier to its conducting or low impedance state and thereby voltage is applied to lamp 22.

When switch 20 is closed under normal operating conditions, the voltage applied to the arc lamp, 12 is, of course, sufficient to start it. The voltage across the lamp 12 is maximum when switch 20 is closed but almost immediately drops to a minimum value and then slowly rises to the normal operating value near the end of the warm-up period, which period may be approximately 5 minutes. The ballast l9 limits the current flow in circuit 10 to a desired value and provides the desired current and voltage slopes.

The values of resistors 28 and 29 of voltage divider 27 are such that the voltage drop across resistor 29, which is proportional to that of arc lamp 12, is insufficient to produce triggering pulses in the circuit when the arc lamp 12 is operating on its normal operating voltage. Whenever the lamp l2 fails to light while the voltage of source 14 is applied thereto, the voltage across the lamp 12 and voltage divider 27 is a maximum. Under these conditions, the voltage across resistor 29 reaches a predetermined value which is sufficient to charge capacitor 31 to the designed breakdown voltage of diac 32 on each half cycle of the supply voltage. The discharge of capacitor 31 through diac 32 and the primary winding 34 produces triggering pulses on the secondary winding 36 to effect conduction of silicon-controlled rectifier 24 which effects the supply of half wave current from the supply voltage source 14 to the lamp 22. Thus, the lamp 22 is automatically turned on in response to an excess voltage across lamp 12 whenever arc lamp 12 fails to conduct current or light with. electric power supplied thereto from source 14. a

Should the arc lamp 12 subsequently start, for example, after a cool-down period of time, the voltage across the arc lamp and the divider 27 decreases to a value which is below that necessary to effect conduction of diac 32. Under these conditions, the triggering pulses for rectifier 24 stop so that it becomes non-conductive and the auxiliary lamp 22 is turned off. The auxiliary lamp 22 is thus automatically turned on whenever arc lamp 12 fails to start when source 14 supplies normal voltage to circuit 10, and is automatically turned .off when the arc lamp starts. Not only does the auxiliary circuit 16 .provide light during the cool-down periods of the arc lamp following a momentary power failure on the circuit 10, but also will provide light should the arc lamp 12 permanently fail or burn-out."

In the circuit of FIG. 1, the arc lamp 12 may be, for example, a lamp which normally operates at l volts (RMS) with a starting potential requirement of about 200 volts (peak). The voltage of AC. source 14 may be, for example, 220 volts or higher. The auxiliary lamp 22 may be, for example, a I I0 volt incandescent lamp where the source voltage is 220 volts since silicon-controlled rectifier 24 provides half wave voltage. The normal RMS voltage appearing across arc lamp l2 may be, for example, about 135 volts and the peak value about 200 volts. The relative values of sensing resistors 28 and 29 are, of course, chosen so that the oscillator 30 will not operate until the arc lamp voltage exceeds a predetermined value that is substantially greater than the peak lamp voltage, in this case, 200 volts and which predetermined value does not occur under ordinary operating conditions unless arc lamp 12 is extinguished and power is applied to it. The peak voltage across sensing resistor 29 when the arc lamp circuit voltage exceeds the above predetermined value or is abnormally high should exceed the designed peak breakdown voltage value of diac 32 to thereby produce trigger pulses for operating the silicon-controlled rectifier 24. Some common diacs (e.g. 1N54l l) have breakdown voltage values between 26 and 38 volts (peak). Resistor 38 is adjustable to vary the firing angle of diac 32 and control the firing angle of the rectifier 24.

Referring now to the embodiment in FIG. 2, a main lighting circuit 40 is shown including a power supply which includes a conventional voltage doubler circuit 41 for supplying direct current to an arc lamp 42. The voltage doubler 41 includes input terminals 44 and 45 connected to an alternating current source 43, output terminals 46 and 47 connected to lamp 42, a pair of capacitors 48, and 49 in series between terminals 46 and 47, and a pair of half-wave rectifiers or diodes 50 and 51. The diode 50 is connected between input terminal 44 and output terminal 46, and diode 51 is connected between input terminal 44 and output terminal 47, the diodes being poled to pass current on opposite half cycles of the supply voltage of source 43. The source 43 may be a conventional 277-volt alternating current source and the arc lamp 42 may be a typical 135-volt arc lamp. At the output terminals 46 and 47 of doubler 41 is a full-wave pulsating direct current voltage which, of course, will have a peak value sufficient to start the arc lamp 42. Because a voltage doubler provides current regulation or I has poor regulation," i.e., the voltage output drops considerably as current is drawn from it, the voltage output at terminals 46 and 47 decays to limit the circuit current. Thus, the doubler 41 provides sufiicient starting voltage for are lamp 42 and also inherently provides ballasting.

In FIG. 2, theauxiliary lighting circuit is indicated generally at 55 and is similar to circuit 16 in FIG. 1. The circuit 55 includes a silicon-controlled rectifier 56 and an auxiliary lamp 57. Condition sensing voltage divider resistors 58 and 59 are secondary winding 66 connected between the gate and one main terminal of the rectifier 56 to provide actuating signals to the gate terminal for controlling the conductive state of the triac. The capacitor 62 is connected across the divider resistor 59 through an adjustable resistor 68.

The operation of the auxiliary circuit 55 in FIG. 2 is also similar to that of circuit 16in FIG. 1. When the arc lamp 42 is operating, the voltage drop across the conducting lamp and resistor 59 is relatively low and the voltage across the capaci tor 62 is below that necessary to fire or effect conduction of diac 63. Under these conditions, the rectifier 56 and therefore the auxiliary lamp 57 are non-conductive.

Whenever the arc lamp 42 fails to start or operate, the impedance and voltage across it is relatively high because of the regulation of the voltage doubler supply source 41. The voltage across divider resistor 59, under these conditions, is sufficiently high to effect operation of the relaxation oscillator circuit including capacitor 62 and diac 63. The capacitor 62 continuously charges to the breakdown voltage value of diac 63 and discharges through primary winding 64 producing triggering pulses across secondary winding 66 to gate or effect conduction of the rectifier 56 on one half cycle of the voltage of source 43 so that half wave voltage is applied to lamp 57 to light it. In this case, the lamp 57 may be a conventional incadescent l l0-volt lamp. By adjusting the firing angle of rectifier 56 or the charging rate of capacitor 62 by adjustment of resistor 68, the voltage on auxiliary lamp 57 may be adjusted to an effective 1 l0-volt value.

In some cases, and particularly where resistor 68 is adjusted to lower the voltage applied to lamp 57, there may be a noticeable flicker in the light from lamp 57 because of variations in the voltage applied on subsequent cycles of supply voltage 43. This flicker may be eliminated by synchronizing the charging of capacitor 62 to the reversal of the supply voltage 43. A transistor 61 connected across capacitor 62 and a transformer 67 provide this synchronization. The primary of transformer 67 is connected across source 43 and the secondary provides a low voltage which, in turn, provides base current to transistor 61 during the time when the bottom terminal of source 43 is more positive than the upper terminal thereof. This base current causes'transistor 61 to conduct and hold capacitor '62 discharged until the upper source terminal becomes more positive than the bottom terminal. At this time capacitor 62 begins to charge at a rate determined partially by the setting of variable resistor 68. Since the charge cycle always starts at the time when the source voltage 43 reverses and since capacitor 62 is always discharged at that time, there will be no noticeable flicker in lamp 57.

Where desired, the rectifier 56 may be a well-known bilaterally conducting semiconductor, such as a triac type thyristor instead of the silicon-controlled rectifier shown. In such case, an alternating voltage is applied to the auxiliary lamp 57. The source 43 voltage and lamp rating should, of course, be of suitable values. Where a triac is used, the transistor 61 and transformer 67 may be omitted from the circuit.

In the embodiment shown in FIG. 3, a main lighting circuit 69 is shown including a transformer, shown as an autotransformer 70, having one end terminal and an intermediate tap connected to an alternating current source 71, and with the end terminals connected to supply power to an arc lamp 72. A power factor correction impedance device shown as a capacitor 73 is connected in series with the lamp 72. In this case, the source 71 may be, for example, an alternating current source of l volts and the lamp 72 a typical mercury arc lamp with a rating of 135 volts. The autotransformer 70 may step-up the circuit voltage to the value necessary to start lamp 72 where desired and also provide the lamp ballasting necessary to limit the current flow. The transformer 70 in FIG. 3 should have a relatively large leakage reactance to regulate the arc lamp current. The transformer 70 may have an output voltage, for example, of 220 volts. Where the value of the voltage of source 71 is sufficient for proper operation of lamp 72, the transformer need not be a step-up transformer.

An auxiliary lamp circuit, indicated generally at 74, is shown including an auxiliary lamp 75, which may be a l 10 volt lamp, connected in series with a switch 76 across the output terminals of transformer 70. The switch 76 is shown as a silicon-controlled rectifier that is controlled by a switch control circuit 78 which produces signal pulses in response to a predetermined circuit condition in main circuit 69 in which the arc lamp 72 is non-conductive or not on," but voltage is supplied to the main lamp circuit 69.

The switch control circuit 78 includes a resistor 80 connected in series with a capacitor 81 across the output of transformer 70, and a capacitor discharge circuit which includes a diac switch 82 and a load resistor 83 connected in series across the capacitor 81 and with resistor 83 connected between the gate and cathode of the silicon-controlled rectifier 76. When the voltage on capacitor 81 is permitted to increase to the predetermined breakdown voltage value of diac 82, capacitor 81 discharges through resistor 83 to thereby provide a triggering or gating pulse at the gate of rectifier 76 to effect conduction thereof and to tum-on auxiliary lamp 75.

The voltage on capacitor 81 is controlled by a voltage control or clamping circuit 85 which includes a transistor 86 connected in series with a blocking diode 87 across the capacitor 81 to provide either a short-circuit or a high impedance in parallel with capacitor 81 with respect to one half cycle of the voltage of main circuit 69. A diode 89 is also connected in parallel circuit relation with capacitor 81 and poled to clamp or provide a constant short-circuit across capacitor 81 with respect to the opposite half cycle of the main circuit voltage. Thus, when transistor 86 is conductive, capacitor 81 is substantially shorted during both positive and negative half cycles of the supply voltage.

In order to sense an arc lamp failure in the main circuit 69, a voltage divider circuit 91 is provided which includes resistors 92 and 93, and a direct current blocking capacitor 94 all connected in series across the power factor capacitor 73. The base electrode of transistor 86 is connected to the upper end of resistor 92 and the emitter electrode is connected through blocking diode 87 to the opposite end of resistor 92, whereby the conductivity of transistor 86 is controlled in response a predetermined polarity of voltage across resistor 92.

Under normal operating conditions when the arc lamp 72 is on and providing light there is an alternating voltage drop across capacitor 73 which results in an alternating current flow in the divider network across capacitor 73 causing a voltage drop across resistor 92. The alternating voltage drop across resistor 92 provides a forward bias current on one half cycle from base to emitter to thereby cause the transistor to be conductive on one half cycle of the supply voltage. Since diode 89 is conductive on the opposite half cycle, the capaci tor 81 cannot charge up to the voltage necessary to cause diac 82 to conduct on either half cycle. Thus, when arc lamp 72 is on, there is no triggering pulse for the controlled rectifier 76, and the auxiliary lamp 75 remains unenergized.

Should there be a momentary power outage such that are lamp 72 cannot immediately conduct or restart or if it permanently fails, lamp 72 acts as an open circuit with the full transformer output voltage across lamp 12 and no alternating voltage appears across the capacitor 73. Under these conditions, there is no forward bias on transistor 86 so that it is switched to its high impedance state. When the transistor 86 is in its high impedance or non-conducting state, capacitor 81 charges through resistor to the designed breakdown voltage value of diac 82 during one half cycle of the supply voltage to thereby produce triggering pulses across resistor 83 connected to the gate of the silicon-controlled rectifier 76. These signal or triggering pulses effect current flow through auxiliary lamp 75 on one half cycle of the supply voltage to produce the desired auxiliary light. Lamp 75 remains on until the arc lamp 72 or a replacement arc lamp lights. For example, should arc lamp 72 subsequently become conductive and relight, an alternating voltage exits across capacitor 73 to again provide forward biasing current for transistor 86 so that capacitor 81 is again by-passed or in effect short-circuited on both positive and negative half cycles of the supply voltage. Capacitor 81 therefore, can no longer charge up to the breakdown value of diac 82 so that the silicon-controlled rectifier becomes nonconductive and the current through the auxiliary lamp 75 ceases. Thus, the sensing circuit permits sufficient voltage to develop across capacitor 81 to produce trigger pulses for rectifier 76 in response to a decrease to zero or a minimum alternating voltage across capacitor 73 which occurs in response to a failure of lamp 72 to light, at which time, maximum voltage is across the lamp.

The direct current blocking capacitor 94 serves to prevent any charge on power factor capacitor 73 that may exist because of a momentary power failure, from effecting the control of transistor 86. Also, the capacitor 73 not only provides power factor correction for the main lighting circuit but, is also connected in the sensing circuit and provides the signal voltage for the auxiliary lighting circuit.

Referring now to FIG. 4, a main lighting circuit is shown including an alternating current supply source 102 connected between an intermediate tap and an end terminal of a step-up autotransformer 104, and an arc lamp 106 and a power factor correction capacitor 108 connected in series between the end terminals of autotransformer 104. An auxiliary lighting circuit 110, in this case, includes a pair of auxiliary lamps 112 and 113, such as incandescent lamps, connected in series with a bilaterally conducting switch 114, illustrated as a triac, across the output terminals of autotransformer 104. Where the supply source 102, for example, supplies 1 10 volts and the autotransformer 104 steps-up the arc lamp circuit voltage to 220 volts, each of the auxiliary lamps 112 and 113 may be a conventional l 10-volt lamp.

The triac 114 is controlled by a switch control or trigger circuit 118 and a relaxation oscillator 120 that is controlled by circuit 118. The oscillator 120 includes a capacitor 122 and a resistor 124 connected in series across the output of transformer 104, and a capacitor discharge circuit including a switch 126, shown as a diac, and a load resistor 128 connected in series with each other across capacitor 122. The gate circuit of triac 114 is connected across resistor 128 so that the conductivity of the triac 114 is controlled by gating pulses across resistor 128.

The clamping circuit 118, in this case, includes a pair of transistor circuits 130 and 132 connected across capacitor 122 of the oscillator circuit 120. Transistor circuit 130 includes a transistor 134 having its emitter and collector connected in series with a diode 136 across the capacitor 122. The transistor circuit l32 includes a transistor 140 having its 'emitterand collector connected in series with a diode 142 across the capacitor 122.

The base terminals of transistors 134 and 140 are connected together at a junction 143 between a pair of voltage divider resistors 144 and 146 that, in turn, are connected in series with a direct current blocking capacitor 150 across the power factor correction capacitor 108. Transistors 134 and 140 are shown respectively as PNP and NPN type transistors with the emitter-base circuits thereof coupled across the resistor 144 such that the transistors 134 and 140 are conductive on opposite half cycles of an alternating voltage across resistor 144. For example, when the upper end of resistor 144 becomes positive with respect to junction 143, transistor 134 is switched to its low impedance state while the other transistor is non-conductive or in its high impedance state. When the junction 143 becomes positive with respect to the upper end of resistor 144, transistor 140 switches to its low impedance state while transistor 134 switches to a high impedance state. With each of the diodes 136 and 142 poled to pass current on the conducting half cycle of its associated transistor, capacitor 122 cannot charge to the breakdown voltage value of diac 126 on either half cycle of the supply voltage when an alternating voltage exists across resistor 144.

When thearc lamp 106 is on during normal circuit conditions, an alternating voltage exits across the power correction capacitor 108, and an alternating voltage drop exists across resistor 144. Both sides of the capacitor 122, under these conditions, are clamped to one side of the transformer 104, that is, transistor circuits 130 and 132 are, in effect, short-circuits across capacitor 122 for both cycles of the supply voltage. The diac 126 remains non-conductive and no triggering pulses are applied to the gate of triac 114. Thus, triac 114 is non-conductive and lamps 1 12 and 113 remain'off.

Should the lamp 106 become extinguished and not relight with the voltage of "transformer 104 applied to theme lamp circuit, no alternating voltage will exist across the power factor capacitor 108 and therefore none across resistor 144; With no alternating voltageacross resistor 144, both transistors 134 and 140 will be maintained in their high impedance states so that capacitor 122 will charge through resistor 124 on each half cycle of the supply voltage. The capacitor 122 will charge up to the breakdown voltage value of diac 126 on each half cycle to produce a trigger pulse across resistor 128 to trigger triac 114 on each half cycle of the supply voltage and thereby provide alternating current to the auxiliary lamps 1 12 and 113 to produce light.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results obtained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An auxiliary lighting circuit for a main lighting system including a high pressure metallic vapor lamp, an alternating current power supply means including ballasting means, said auxiliary lighting circuit comprising auxiliary lamp means, semiconductor switch means having a pair of main terminals and a control terminal, means connecting said main terminals in series with said auxiliary lamp means across said. supply means, a relaxation oscillator circuit including capacitor means and output means including a semiconductor switching means, said switching means being conductive in response to a predetermined charge value on said capacitor means to produce a signal pulse at said output means, means connecting said control terminal to said output means to effect conduction of said switch means in response to a signal pulse at said output circuit, impedance means connected in series with said capacitor means across said power supply means to provide a capacitor charging path, semiconductor means coupled across said capacitor means, and control means for controlling the impedance of said semiconductor means to provide an effective short-circuit across said capacitor means to prevent'the charging of said capacitor means to said predetermined charge value in response to conduction of said arc lamp, and to provide a relatively high impedance across said capacitor means to permit said capacitor to charge to said predetermined value in response to a failure of said arc lamp to conduct current when power is supplied to said arc lamp, said control means including a capacitance means connected in series with said are lamp and voltage responsive means coupled across said capacitance means for providing a voltage for controlling the impedance of said semiconductor means in response to current flow in said arc lamp.

2. The auxiliary lighting circuit according to claim 1 wherein said semiconductor means comprises a transistor. to said transistor to provide an effective short-circuit across 3. The auxiliary lighting circuit according to claim 2 wherein said semiconductor means further includes a diode coupled across said capacitor means and oppositely poled with respect to said transistor to providean effective short-circuit across said capacitor means for one-half cycle of the supply voltage.

4. The auxiliary lighting circuit according to claim 2 further including a second transistor coupled across said capacitor means and conductive on opposite half cycles of the supply voltage relative to said first named transistor.

5. The auxiliary lighting circuit according to claim 4 wherein said semiconductor switch means comprises a triac.

6. The combination with a main lighting circuit including a high pressure metallic vapor lamp, capacitance means con nected in series with the vapor lamp to provide power factor correction for said lighting circuit, an alternating current voltage supply source including transformer means to supply power to said lighting circuit and provide ballasting means for said vapor lamp, of an auxiliary lighting circuit comprising an auxiliary lamp circuit including an auxiliary lamp, bilaterally conducting switch means having main terminals and a control electrode, means connecting said main terminals in series with said auxiliary lamp, and means for supplying power from said voltage supply source to said lamp circuit, relaxation oscillator means including capacitor means, output means including semiconductor switching means, said switching means being conductive in response to a predetermined charge value on said capacitor means to produce a signal pulse at said output means, means connecting said control terminal to said output means to effect conduction of said switch means in response to a signal pulse at said output circuit, impedance means, and means connecting said impedance means in series with said capacitor means to be energized bysaid supply source and to provide a capacitor charging path, a pair of semiconductor devices coupled across said capacitor means and related to conduct current on opposite half cycles of said supply voltages when conductive, and circuit means for controlling the conductivity of said devices including means coupled to said capacitance means and responsive to the voltage thereacross for effecting the conduction of both of said devices in response to an alternating voltage across said capacitance means to effectively provide short-circuits across said capacitor means to maintain said switch means nonconductive, and for effecting nonconduction of both of said devices in response to an absence of alternating voltage across said capacitance means to permit charging of said capacitor means to said predetermined charge value on both half cycles of said supply voltage to thereby effect conduction of said switch means on both half cycles of said supply voltage and energization of said auxiliary lamp.

7. The combination according to claim 6 wherein said semiconductor devices comprise transistors.

8. The combination according to claim 7 wherein reversely poled diodes are connected respectively in series with said transistors and poled to pass current on opposite half cycles of said supply voltage.

9. The combination according to claim 7 wherein said circuit means includes bias resistor means for said transistors connected in circuit with said capacitance means and the base electrodes of said transistors.

10. The combination according to claim 7 wherein said circuit means includes a pair of resistors connected in series with each other across said capacitance means, the base electrodes of said transistors being coupled to a first common circuit point, and means connecting one other terminal of each of said transistors to another common circuit point, and means connecting one of said resistors between said first and second common circuit points to control bias current flow through both of said transistors.

11. The combination according to claim 10 further including direct current blocking capacitance means connected in series with said resistors.

12.'In an auxiliary lighting means for a lighting circuit having a main light source, a voltage source electrically connected thereto, an impedance device electrically connected in series between said voltage source and said main light source, an auxiliary light source, switch means connected with said auxiliary light source for controlling the energization of said auxiliary light source, said switch means including signal responsive means for controlling the conductivity of said switch means, the improvement comprising solid state control means coupled to said lighting circuit for supplying a signal to said signal responsive means of said switch means, said control means comprising means for sensing a voltage across said impedance device and means for supplying a signal to said signal responsive means in response to a change in voltage across said impedance device.

13. The improvement of claim 12 wherein the voltage source comprises a source of alternating current.

14. The improvement of claim 13 wherein said control means supplies a signal to said signal responsive means when the voltage drop across said impedance device is zero.

15. The device of claim 12 wherein said main light source includes a high pressure metallic vapor lamp.

16. The improvement of claim 14 wherein said signal supplying means of said control means comprises an oscillator circuit and said voltage sensing means comprises a clamping circuit for preventing the operation of the oscillator circuit when a voltage exists across the impedance device and for energizing the oscillator when no voltage exists across the impedance device.

17. The improvement of claim 16 wherein said oscillator circuit comprises a resistor and a capacitor connected electrically in series and said clamping circuit is coupled across said capacitor, said clamping circuit comprising variable impedance means and voltage responsive means coupled across said impedance device in said lighting circuit for controlling the impedance of said variable impedance means in response to a voltage across said impedance device.

18. The improvement of claim 17 wherein said variable impedance device comprises first semiconductor means connected to said voltage responsive means and biased to a low impedance state by said voltage responsive means when a voltage exists across said impedance device in said main lighting circuit during one half cycle of said power supply and a second semiconductor means connected to provide a low impedance path across said capacitor at least when a voltage drop exists across said impedance device in said main lighting circuit during the other half cycle.

19. The improvement of claim 18 wherein said voltage responsive means comprises a direct current blocking capacitor and a voltage divider connected across said impedance device of said main lighting circuit.

20. The improvement of claim 19 wherein said second semiconductor means includes a diode coupled across said capacitor and oppositely poled with respect to said first semiconductor means to provide an effective short-circuit across said capacitor for one half cycle of the supply voltage.

21. The improvement of claim 19 wherein said second semiconductor means is connected to said voltage responsive means and is conductive on opposite half cycles of the supply voltage relative to said first semiconductor means when a voltage exists across said impedance device in said main lighting circuit.

22. The improvement of claim 20 wherein said switch means comprises an SCR.

23. The improvement according to claim 21 wherein said switch comprises a triac.

24. The improvement of claim 17 in which said oscillator circuit comprises an output circuit including semiconductor switching means conductive in response to a predetermined charge value on said capacitor to produce a signal pulse at said control terminal of said switch.

25. The improvement of claim 12 in which said impedance device comprises a capacitor.

26. The improvement of claim 12 in which said voltage source comprises a transformer.

UNITED STATES PATENT OFFICE CERTIFICATE OF QOEQ'HQN Patent No. 3,659,146 Dated April 25, 1972 Inventor(s) Robert D. Munson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, lines 21 and 22, after "transistor." delete to said transistor to provide an effective shortcircuit across Signed and sealed this 29th day of August 1972.

( A Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR.

Commissioner of Patents Attesting Officer FORM PO-1050 (10- 9) USCOMM-DC 60376-P69 U.$. GOVERNMENT PIHNTlNG OFFICE: 1989 O-366-33A

Claims (26)

1. An auxiliary lighting circuit for a main lighting system including a high pressure metallic vapor lamp, an alternating current power supply means including ballasting means, said auxiliary lighting circuit comprising auxiliary lamp means, semiconductor switch means having a pair of main terminals and a control terminal, means connecting said main terminals in series with said auxiliary lamp means across said supply means, a relaxation oscillator circuit including capacitor means and output means including a semiconductor switching means, said switching means being conductive in response to a predetermined charge value on said capacitor means to produce a signal pulse at said output means, means connecting said control terminal to said output means to effect conduction of said switch means in response to a signal pulse at said output circuit, impedance means connected in series with said capacitor means across said power supply means to provide a capacitor charging path, semiconductor means coupled across said capacitor means, and control means for controlling the impedance of said semiconductor means to provide an effective short-circuit across said capacitor means to prevent the charging of said capacitor means to said predetermined charge value in response to conduction of said arc lamp, and to provide a relatively high impedance across said capacitor means to permit said capacitor to charge to said predetermined value in response to a failure of said arc lamp to conduct current when power is supplied to said arc lamp, said control means including a capacitance means connected in series with said arc lamp and voltage responsive means coupled across said capacitance means for providing a voltage for controlling the impedance of said semiconductor means in response to current flow in said arc lamp.

2. The auxiliary lighting circuit according to claim 1 wherein said semiconductor means comprises a transistor. to said transistor to provide an effective short-circuit across

3. The auxiliary lighting circuit according to claim 2 wherein said semiconducTor means further includes a diode coupled across said capacitor means and oppositely poled with respect to said transistor to provide an effective short-circuit across said capacitor means for one-half cycle of the supply voltage.

4. The auxiliary lighting circuit according to claim 2 further including a second transistor coupled across said capacitor means and conductive on opposite half cycles of the supply voltage relative to said first named transistor.

5. The auxiliary lighting circuit according to claim 4 wherein said semiconductor switch means comprises a triac.

6. The combination with a main lighting circuit including a high pressure metallic vapor lamp, capacitance means connected in series with the vapor lamp to provide power factor correction for said lighting circuit, an alternating current voltage supply source including transformer means to supply power to said lighting circuit and provide ballasting means for said vapor lamp, of an auxiliary lighting circuit comprising an auxiliary lamp circuit including an auxiliary lamp, bilaterally conducting switch means having main terminals and a control electrode, means connecting said main terminals in series with said auxiliary lamp, and means for supplying power from said voltage supply source to said lamp circuit, relaxation oscillator means including capacitor means, output means including semiconductor switching means, said switching means being conductive in response to a predetermined charge value on said capacitor means to produce a signal pulse at said output means, means connecting said control terminal to said output means to effect conduction of said switch means in response to a signal pulse at said output circuit, impedance means, and means connecting said impedance means in series with said capacitor means to be energized by said supply source and to provide a capacitor charging path, a pair of semiconductor devices coupled across said capacitor means and related to conduct current on opposite half cycles of said supply voltages when conductive, and circuit means for controlling the conductivity of said devices including means coupled to said capacitance means and responsive to the voltage thereacross for effecting the conduction of both of said devices in response to an alternating voltage across said capacitance means to effectively provide short-circuits across said capacitor means to maintain said switch means nonconductive, and for effecting nonconduction of both of said devices in response to an absence of alternating voltage across said capacitance means to permit charging of said capacitor means to said predetermined charge value on both half cycles of said supply voltage to thereby effect conduction of said switch means on both half cycles of said supply voltage and energization of said auxiliary lamp.

7. The combination according to claim 6 wherein said semiconductor devices comprise transistors.

8. The combination according to claim 7 wherein reversely poled diodes are connected respectively in series with said transistors and poled to pass current on opposite half cycles of said supply voltage.

9. The combination according to claim 7 wherein said circuit means includes bias resistor means for said transistors connected in circuit with said capacitance means and the base electrodes of said transistors.

10. The combination according to claim 7 wherein said circuit means includes a pair of resistors connected in series with each other across said capacitance means, the base electrodes of said transistors being coupled to a first common circuit point, and means connecting one other terminal of each of said transistors to another common circuit point, and means connecting one of said resistors between said first and second common circuit points to control bias current flow through both of said transistors.

11. The combination according to claim 10 further including direct current blocking capacitance means connected in series with said resistors.

12. In an auxiliAry lighting means for a lighting circuit having a main light source, a voltage source electrically connected thereto, an impedance device electrically connected in series between said voltage source and said main light source, an auxiliary light source, switch means connected with said auxiliary light source for controlling the energization of said auxiliary light source, said switch means including signal responsive means for controlling the conductivity of said switch means, the improvement comprising solid state control means coupled to said lighting circuit for supplying a signal to said signal responsive means of said switch means, said control means comprising means for sensing a voltage across said impedance device and means for supplying a signal to said signal responsive means in response to a change in voltage across said impedance device.

13. The improvement of claim 12 wherein the voltage source comprises a source of alternating current.

14. The improvement of claim 13 wherein said control means supplies a signal to said signal responsive means when the voltage drop across said impedance device is zero.

15. The device of claim 12 wherein said main light source includes a high pressure metallic vapor lamp.

16. The improvement of claim 14 wherein said signal supplying means of said control means comprises an oscillator circuit and said voltage sensing means comprises a clamping circuit for preventing the operation of the oscillator circuit when a voltage exists across the impedance device and for energizing the oscillator when no voltage exists across the impedance device.

17. The improvement of claim 16 wherein said oscillator circuit comprises a resistor and a capacitor connected electrically in series and said clamping circuit is coupled across said capacitor, said clamping circuit comprising variable impedance means and voltage responsive means coupled across said impedance device in said lighting circuit for controlling the impedance of said variable impedance means in response to a voltage across said impedance device.

18. The improvement of claim 17 wherein said variable impedance device comprises first semiconductor means connected to said voltage responsive means and biased to a low impedance state by said voltage responsive means when a voltage exists across said impedance device in said main lighting circuit during one half cycle of said power supply and a second semiconductor means connected to provide a low impedance path across said capacitor at least when a voltage drop exists across said impedance device in said main lighting circuit during the other half cycle.

19. The improvement of claim 18 wherein said voltage responsive means comprises a direct current blocking capacitor and a voltage divider connected across said impedance device of said main lighting circuit.

20. The improvement of claim 19 wherein said second semiconductor means includes a diode coupled across said capacitor and oppositely poled with respect to said first semiconductor means to provide an effective short-circuit across said capacitor for one half cycle of the supply voltage.

21. The improvement of claim 19 wherein said second semiconductor means is connected to said voltage responsive means and is conductive on opposite half cycles of the supply voltage relative to said first semiconductor means when a voltage exists across said impedance device in said main lighting circuit.

22. The improvement of claim 20 wherein said switch means comprises an SCR.

23. The improvement according to claim 21 wherein said switch comprises a triac.

24. The improvement of claim 17 in which said oscillator circuit comprises an output circuit including semiconductor switching means conductive in response to a predetermined charge value on said capacitor to produce a signal pulse at said control terminal of said switch.

25. The improvement of claim 12 in which said impedance device comprises a capacitor.

26. The improvement of claim 12 in which said voltaGe source comprises a transformer.

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