Abstract:
A non-arcing electrical switch for use with an auxiliary light source for a gaseous discharge lamp includes a current sensing component, a timer power component, an off-delay timer, a voltage control component, and a phase control component. When the light output from the gaseous discharge lamp is interrupted, or during the initial warm up of the gaseous discharge lamp, the non-arcing electrical switch activates an auxiliary lamp to supply temporary illumination. The electrical switch has improved reset reliability and repeatability while decreasing the reset period required during momentary interruptions of the gaseous discharge lamp. Furthermore, the electrical switch requires no negative or minus power supply in order to initiate reset and operates at voltages of less than two volts.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a non-arcing electrical switch. More particularly, the present invention pertains to an auxiliary lighting circuit for use with a gaseous discharge lamp. 
     An auxiliary lighting circuit generally refers to a circuit which activates a lamp, usually incandescent, when the primary lighting means is interrupted or fails. Auxiliary lighting circuits are widely used on gaseous discharge lamps to provide light in the event the gaseous discharge lamp fails or is interrupted. 
     Due to their high efficiency and long life span, gaseous discharge lamps are commonly used in retail displays, gymnasiums, factories, hallways, outdoor sports lighting, streets, parking areas, and bridge underpasses. Commonly known examples of gaseous discharge lamps include fluorescent and High Intensity Discharge (HID) lamps, such as metal halide, sodium, and mercury vapor lamps. 
     Light can be produced in these discharge lamps by establishing an arc through a gas, a process known as electric discharge, or gaseous discharge. However, it can take several seconds for the arc to be established, and several minutes until full light output is reached. If power to the gaseous discharge lamp is interrupted, the discharge lamp must be allowed to cool for a time, usually several minutes, before the arc can be reestablished and normal operation resumed. 
     To compensate for the lack of light during the period of time when the discharge lamp is not illuminated or is in a low luminescence condition, a standby, or auxiliary, incandescent lamp is typically connected to the discharge lamp to provide auxiliary lighting. The auxiliary lighting circuitry senses the state of the discharge lamp and energizes the secondary/auxiliary lamp. When power is applied, the auxiliary lamp illuminates while the discharge lamp has time to cool then restrike/relight, at which time the auxiliary lamp is extinguished. A time delay feature keeps the auxiliary lamp on during the discharge lamp&#39;s warm up period prior to automatically turning off the auxiliary lamp. The auxiliary lamp typically operates from a 120 V AC  supply. 
     Previous auxiliary lighting circuits, however, are severely limited in their range of application. Typically, they are designed to measure specific voltage levels to determine the status of the discharge lamp. Also, the previously known auxiliary discharge lamps have no general applicability to other lamps aside from the gaseous discharge lamp to which it is connected. Furthermore, known auxiliary lighting circuits that are capable of detecting current rather than voltage may need levels of load current to be relatively high in order to detect it. In addition, the repeatability, reliability, and speed of reset timers in known auxiliary lighting circuits are a concern. 
     Accordingly, there is a need for an improved auxiliary lighting circuit for use with a lamp, particularly with a gaseous discharge lamp. Desirably, such an auxiliary lighting circuit can detect lower load currents than formerly was possible with known auxiliary lighting circuits, has reduced reset times during power interruptions, and has improved reset reliability and repeatability. In addition, it is desirable to have an auxiliary lighting circuit that maintains the auxiliary lamp voltage at 120 V, regardless of input voltage and can operate a timing circuit at 2 V or less. 
     BRIEF SUMMARY OF THE INVENTION 
     The auxiliary lighting circuit includes five (5) distinct sections: 
     a current sensing circuit which includes high current diodes which convert current flowing through a gaseous discharge lamp into a useable voltage; 
     a timer power supply circuit which includes a rectifier diode, a filter capacitor, a current limiting resistor and voltage limiting diodes that convert the AC voltage provided by the current sensing circuit into a useable +1.98 V DC  regulated power supply; 
     an off delay timer circuit including a light emitting diode (LED) which maintains an on-state of the auxiliary lighting source for a pre-determined period of time, allowing the load, in this case a gaseous discharge lamp, to achieve full intensity before extinguishing the auxiliary light source; 
     a voltage control circuit which monitors the output voltage supplied to an auxiliary lamp via lead wires by turning ‘on’ or ‘off’ a triac located in the phase control circuit so as to maintain a constant AC voltage to an auxiliary lamp, regardless of the input voltages impressed upon the lead wires; and 
     a phase control circuit including the triac referred to previously, as well as a capacitor, a diac, and a resistor divider network, which determines what portion of the AC sine wave will be directed to the auxiliary lamp and which portion of the AC sine wave will be blocked so as to maintain an average AC voltage sufficient to operate an auxiliary lamp. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The benefits and advantages of the present invention will become more readily apparent to those of ordinary skill in the relevant art after reviewing the following detailed description and accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of a timed circuit embodying the principles of the present invention; 
         FIG. 2  is a schematic diagram of a non-timed circuit embodying the principles of the present invention; 
         FIG. 3  is a block diagram of the timed circuit embodying the principles of the present invention; and 
         FIG. 4  is a block diagram of the non-timed circuit embodying the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated. 
     It should be further understood that the title of this section of this specification, namely, “Detailed Description Of The Invention”, relates to a requirement of the United States Patent Office, and does not imply, nor should be inferred to limit the subject matter disclosed herein. 
     To control the auxiliary lamp/light source, an auxiliary lighting circuit is used. The auxiliary lighting circuit of the present invention has five (5) components: a current sensing component, a timer power component, an off-delay timer component, a voltage control component, and a phase control component. Each component and their interrelation is described below. 
     Current Sensing Component 
     Referring to  FIGS. 1 and 3 , shown on the far right side is an embodiment of the current sensing component of the auxiliary lighting circuit. The current sensing component is formed from current sensing leads, J 4  and J 5 , four (4) diodes, three (3) of which are in series, D 14 , D 15 , and D 16 , and one which is in parallel, D 13 , and reversed biased. The current sensing leads J 4 , J 5 , detect current running through a gaseous discharge lamp and utilize a portion of this current to power the auxiliary lighting circuit. Because current available from gaseous discharge lamps is typically of sufficient power to greatly damage a circuit, the current needs to be reduced in order to protect the auxiliary circuit. Diodes D 14 , D 15 , and D 16  act to limit the available power from the discharge lamp to the auxiliary circuit, dropping the power to a usable level. 
     When a load is connected between the current sensing leads J 4  and J 5 , a voltage drop of approximately 2.4 V is observed between the anode of diode D 14  (J 5 ) and the cathode of diode D 16  (J 4 ). As one skilled in the art knows, each diode exhibits approximately a 0.8 volt drop during the positive portion of the AC sine wave. During the negative portion of the AC sine wave, the voltage is blocked by diodes D 14  through D 16 , but is allowed to pass through diode D 13 . This diode configuration permits a small amount of energy to be extracted from the load without adversely affecting the lamp operation. Current limiting resister R 11  also acts to limit the power available to the auxiliary circuit. 
     As the diodes in the current sensing circuit are non-inductive in nature, (such as that of a current transformer), and do not require a primary-to-secondary transfer ratio (such as that of a current transformer) the current sensing circuit can operate as effectively from a DC potential as it can from high frequency AC potentials. 
     The present invention is an improvement to the known current sensing circuits associated with auxiliary lighting devices because the present invention is able to detect substantially lower load currents, where such lower load currents may range between direct current (dc) and frequencies far beyond the typical 50/60 Hz. 
     Timer Power Supply 
     Referring again to  FIGS. 1 and 3 , the positive portion of the 2.4 volts made available from the current sensing circuit is passed into rectifier diode D 12 , while the negative portion of the 0.8 V is blocked by D 12 . This configuration forms a crude DC power supply. Filter capacitor C 8  has been incorporated into the circuit to ‘smooth’ the DC ripple component seen at the cathode of D 12 . 
     As the energy for the power supply is derived directly from the load circuit, several amperes may be available at the cathode of D 12  and positive side of filter capacitor C 8 . For this reason, a current limiting resistor R 11  has been placed in series with the remaining portion of the circuit. 
     To further limit the peak voltage (V p ) available at current limiting resistor R 11 , three (3) general-purpose diodes, D 9 , D 10  and D 11  have been connected in series and placed across the power supply immediately after the current limiting resistor R 11 . Due to the losses of diode D 12  and current limiting resistor R 11 , the maximum voltage made available from the timer power supply component would be less than 2.0 V DC . 
     Off Delay Timer Circuit 
       FIGS. 1 and 3  illustrate the DC voltage provided by the timer power supply circuit that is applied to timing capacitor C 7  via charging resistor R 10 . This forms the time base upon which the remainder of the timing circuit relies. During initial application of voltage to the timing circuit, LED in opto-coupler IC 2  is off, and the timing circuit cannot influence the operation of the voltage control circuit or the phase control circuit. 
     As current begins to flow through the current sensing circuit by way of J 4  and J 5 , the timer power supply circuit provides a DC voltage to resistor R 10 , increasing the voltage potential across capacitor C 7 . Due to this high sensitivity configuration, it must be noted that capacitor C 6  is connected in parallel with timing resistor R 10 , and is provided to reduce electrical noise which may initiate false triggering of the timing circuit, due primarily by high frequency interference at current sensing leads J 4  and J 5 . Similarly, capacitor C 5  is in parallel with pull-up resistor R 5 , and performs the same function. 
     The collector of PNP transistor Q 2  controls the LED of opto-coupler IC 2 . Transistor Q 2  is typically held in a non-conductive or off-state by holding the base of Q 2  at or near its emitter potential by pull-up resistor R 5 . As transistor Q 2  is in an ‘off’ state, the collector of Q 2  is ‘open’ and rests at supply minus (−) potential. Consequently, NPN transistors Q 3  and Q 4  are held in an off-state as a result of pull-down resistor R 7 , where the bases of transistors Q 3  and Q 4  are held at or near their emitter potential. 
     During the charging cycle, the voltage across timing capacitor C 7  increases until the base bias threshold voltage of NPN transistor Q 5  is reached. As transistor Q 5  is a Darlington-type transistor, the threshold voltage will be typically 1.00 V DC . As transistor Q 5  is forward biased or turned on, the collector of transistor Q 5 , previously held high by resistor R 5  and R 8 , is now pulled down to supply minus (−). As the collector of transistor Q 5  is pulled down to supply minus (−), a negative voltage is also applied to the base of transistor Q 2 , forward biasing or turning on Q 2  which in turn forces the collector of transistor Q 2  up to supply plus (+). As collector of transistor Q 2  is pulled up to supply plus (+), current begins to flow through LED of opto-coupler IC 2  as a result of voltage potential available from the power supply circuit. With collector of transistor Q 2  now at supply plus (+), so too, are the base terminals of transistors Q 3  and Q 4 . As transistors Q 3  and Q 4  are forward biased or turned-on, the collectors of Q 3  and Q 4  are pulled down to supply minus (−). The two functions occur simultaneously. 
     The collector of transistor Q 3 , now at supply minus (−) potential, holds transistor Q 2  in a conductive or on-state by forcing the base of Q 2  below that of its emitter voltage, providing the LED of opto-coupler IC 2  with an uninterrupted voltage source after the timing cycle has completed. Transistor Q 4 &#39;s collector is pulled to supply minus (−), discharging timing capacitor C 7  via current limiting resistor R 9 . With the timing cycle completed, the LED of opto-coupler IC 2  is held on by a simple latch circuit formed by PNP transistor Q 2  and NPN transistor Q 3 . This transistor configuration also provides for virtually instant reset periods when current flow through current sensing leads J 4  and J 5  has been interrupted, as transistor Q 2  and Q 3  cannot sustain the latched state for more than a few microseconds after power is removed. 
     The present invention&#39;s timing circuit dramatically reduces the timer reset period required during momentary power interruptions, improves reset reliability and repeatability. The timing circuit no longer requires a negative or minus power supply voltage to initiate reset, and operates at voltages of less than two (2) volts. 
     Voltage Control Circuit 
       FIGS. 1 and 2  show a voltage regulator and phase control circuit that permit operation with input voltages ranging between 120 V AC  and 277 V AC  while maintaining a nominal auxiliary quartz lamp voltage of 120 V AC . 
     It is understood that the voltage control circuit has no appreciable influence on the phase control circuit, provided the line input voltages remain at or below 135 V AC . As the input voltage applied between J 1  and J 3  exceeds 135 V AC , however, the following sequence of events occurs. 
     Line input voltages in excess of 135 V are passed through triac Q 1  to output terminal J 2 . This excessive output voltage at terminals J 1  and J 2  induces a potential across voltage dependent resistor ZNR 1 . Capacitor C 4  is placed in series with ZNR 1  and provides current limiting to the remainder of the control circuitry, as voltage dependent resistor ZNR 1  exhibits reduced resistance as voltage potential increases. 
     Output voltages in excess of 135 V are passed through current limiting capacitor C 4  and voltage dependent resistor ZNR 1 , into a full-wave bridge rectifier network comprised of rectifier diodes D 5 , D 6 , D 7  and D 8 , with the return path being terminated at ground/common J 1 . 
     The DC voltage provided by the bridge rectifier D 5 -D 8  is smoothed or filtered by filter capacitor C 3 , passed through current limiting resistor R 4  to the LED of opto-coupler IC 1 , forward-biasing or turning on the NPN transistor located within the opto-coupler IC 1 . The NPN transistor within IC 1  discharges energy stored within capacitor C 2 , causing a current to flow through bridge rectifier diodes D 1 , D 2 , D 3  and D 4 , reducing the voltage potential between the gate and MT 1  (Main Terminal  1 ) of triac Q 1 . 
     Reducing the voltage differential between the gate and MT 1  correspondingly reduces the output voltage made available at MT 1  of triac Q 1 . As this output voltage is reduced (as measured between terminals J 1  and J 2 ), current no longer flows through current limiting capacitor C 4 , voltage dependent resistor ZNR 1 , bridge rectifier D 5 -D 8 , current limiting resistor R 4  or LED of opto-coupler IC 1 . As LED of IC 1  is no longer illuminated, NPN transistor of IC 1  forward conduction ceases, allowing triac Q 1  to return to full conduction or on-state. 
     Repeating the previously described cycle from the on-state to the off-state occurs at a rate of 120 times per second when provided with a 60 Hz line voltage supply. Additionally, the gate of triac Q 1  may be triggered at various points within the rise and fall of the sine wave, forming a simple phase control circuit. 
     It must be noted that the NPN transistor contained within opto-coupler IC 2  is electrically connected in parallel with the NPN transistor contained within opto-coupler IC 1 , and where voltage control circuit exclusively controls IC 1 , off delay timer circuit IC 2  will override the functions of the voltage control circuit by bringing the gate and MT 1  of Q 1  to the same electrical potential, forcing triac Q 1  into a non-conductive or off state until such time as the current flow via current sensing circuit is removed, resetting the timer circuit. 
     Voltage Control Circuit without Timer 
       FIGS. 2 and 4  illustrate the voltage control circuit without the timer circuit. As current begins to flow through current sensing leads J 4  and J 5 , the DC voltage provided by the power supply circuit is applied to the LED of IC 2 , causing NPN transistor of IC 2  to become conductive (turn on), which in turn ‘shorts-out’ the rectifier bridge comprised of diodes D 1 -D 4 , and as described, forces the voltage potential at resistors R 1  and R 2  to that of triac Q 1  main terminal  1  (MT 1 ), causing triac Q 1  to enter a non-conducting or off-state so as to extinguish the auxiliary lamp. 
     Phase Control Circuit 
       FIGS. 1-4  illustrate a voltage regulator and phase control circuit that permit operation with input voltages ranging between 120 V AC  and 277 V AC  while maintaining a nominal auxiliary lamp voltage of 120 V AC . 
     Referring to  FIGS. 1 and 2 , phase controlling triac Q 1  terminals MT 1  and MT 2  are connected in a series configuration between 120-277 V AC  line voltage via J 3  and the auxiliary lamp via J 2 , which in turn is connected to the common or neutral of the line voltage at J 1 . 
     Referring now to  FIG. 1 , note that capacitor C 1  and resistors R 1 , R 2  and R 3  form a voltage divider network connected between MT 1  (main terminal  1 ) and MT 2  (main terminal  2 ) of triac Q 1 , and at the termination of C 1  and R 1  is also connected to diac 1  (a bi-directional 32-volt trigger or break-over device) which in turn is connected to the gate of triac Q 1 . 
     A voltage increase between terminals MT 1  and MT 2  of triac Q 1  impresses the voltage rise upon diac 1  via resistors R 1 , R 2 , and R 3 , momentarily forcing triac Q 1  into conduction via Q 1  gate, allowing line voltages to flow to the auxiliary lighting source. It should be noted that during this portion of the cycle, capacitor C 1  is low enough in value and does not adversely influence the forward voltages induced by resistors R 1 , R 2 , and R 3 . 
     As the line voltage sine wave again rises above zero potential, the cycle described above is repeated at the rate of 120 times per second (60 Hz), placing triac Q 1  in a fully conductive state and providing full line voltage to the auxiliary lamp. Capacitor C 1  provides a slight phase angle shift to the gate of triac Q 1 , as the voltage provided by resistors R 1 , R 2  and R 3  increases at the rise of each half of the AC sine wave. 
     The circuit described above represents a normal on-state of the auxiliary lamp control, based upon line input voltages of between 100 and 135 V AC . 
     All patents referred to herein, are hereby incorporated herein by reference, whether or not specifically done so within the text of this disclosure. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. 
     From the foregoing it will be observed that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.