Abstract:
A high frequency system for gas discharge lamps includes a method of, and apparatus for, controlling the operation of a plurality of gas discharge lamps and provides; a reduction in starting and operating voltage and current; an increased range of dimming; and improved efficiency and reliability.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention. 
     This invention relates generally to systems and methods of operation of gaseous discharge lamps and is more particularly directed to systems incorporating methods and apparatus for operating gaseous discharge lamps from a variable source of high frequency energy in the spectrum above that audible to the human sense organs. 
     2. Prior Art. 
     Representative prior art relating to the general field of my invention may be seen in the following patents: 
     
         ______________________________________Patent No.   Issued   Title           Patentee______________________________________3,889,153   6/10/75  Power Source For                            Pierce            Fluorescent Lamps            And The Like3,896,336   7/22/75  Solid State     Schreiner et al            Fluorescent Lamp            Ballast System4,127,798   11/28/78 Lamp Circuit    Anderson4,207,497   6/10/80  Ballast Structure                            Capewell et al            For Central High            Frequency Dimming            Apparatus4,207,498   6/10/80  System For Energizing                            Spira et al            And Dimming Gas            Discharge Lamps4,210,846   7/1/80   Inverter Circuit                            Capewell et al            For Energizing And            Dimming Gas Discharge            Lamps4,222,096   9/9/80   D-C Power Supply                            Capewell et al            Circuit With High            Power Factor______________________________________ 
    
     In the realm of my experience with the subject matter of the above noted prior art, a number of deficiencies have arisen which are obviated by the novel and unobvious methods and apparatus of my invention as will be set forth below. 
     Among the deficiencies perceived in the prior art are a lack of ability to &#34;light&#34; the individual lamp connected to a source of high frequency power in a random sequence; to provide a substantial equality or balance of the light output of individual lamps when &#34;lit&#34; and to provide an effective dimming range of more than 50% of the maximum brightness of a given lamp. 
     BRIEF DESCRIPTION OF THE INVENTION 
     A method and apparatus for practicing the method will be set forth in detail below, however, briefly, my invention includes the concept and apparatus of providing a plurality of gaseous discharge lamps to be operated from a variable source of high frequency alternating current with one or the other of inductive or capacitive ballast devices which are substantially equal in number to provide a substantially unity power factor and which typically include a reactive element for alleviating or preventing the existence of assymmetry in the operation of a given gaseous discharge lamp and in which the values of the components are chosen to provide individual resonant frequencies that are greater than 10 percent above or below the frequency of the variable source of alternating current. 
     My invention further comprises protective devices and operational conditions under which the voltage of the variable source of alternating current is substantially that of the running voltage of the plurality of lamp units connected in parallel to the source of energy and include level responsive and timing means for initiating or re-initiating the operation of a given system after an overload condiditon so that at the initiation of operation, the voltage, or potential, of the variable source of alternating current energy gradually increases from a reduced value to the desired operational value. 
     In a typical application of the principles of my invention, a plurality of lamp units, consisting of a substantially equal number of units exhibiting capacitive or inductive ballast characteristics are connected in parallel to a source of high frequency alternating current energy of approximately 28.5 kilohertz that is controlled to provide an output voltage of approximately the rated running voltage of the gaseous discharge lamps contained in the lamp units and which is provided with a means for varying the output voltage from a lower value to the higher running value during a predetemined period of time for initial &#34;lighting&#34; of the individual lamp units, under which conditions, the individual lamp units may be observed to &#34;light&#34; in sequence (as may be confirmed by observing a substantially uniform low value of current approaching the running current of a given system) and which provides for &#34;lighting&#34; or starting of the individual lamp units at about the same voltage as the running voltage, and substantial balance in the light output of each of the lamp units for a given level of input voltage. 
     My invention further provides for an increased dimming range beyond the 50% normally attained with known systems by the addition of a reactive element disposed in proximity to and for coaction with an inductive portion of a lamp unit so as to react to an asymmetrical operation that is detrimental to individual lamps and which tends to prevent operation at low voltages required for increased dimming range and to effectively form a block as to any DC potentials existing between the electrodes of an individual lamp. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic and diagrammatic representation of a high frequency source of alternating current energy; 
     FIG. 2 is a schematic and diagrammatic representation of a complete high frequency lighting system embodying a power supply as in FIG. 1 as well as a plurality of gaseous discharge lamps; 
     FIGS. 3A, B, C and D are electrical schematic drawings and a sketch illustrating the manner in which the individual sheets of drawings may be assembled into a full composite drawing of a power supply for use with my invention; 
     FIGS. 4A, B, C, D and E are electrical schematic drawings and a sketch indicating the manner in which the individual sheets may be assembled to form a composite drawing of a further embodiment of a power supply for use with my invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to FIG. 2 of the drawings, a variable energy power supply is indicated generally by reference character 10 and includes a pair of output terminals 11 and 12 connected in circuit with essentially like pluralities of inductive, 13, or capacitive, 14, gaseous discharge lamp units, each including a gaseous discharge lamp 15, through conductors 16 and 17. 
     In FIG. 2 inductive gaseous discharge lamp unit 13 is shown comprised of an inductor 19 and capacitor 20 connected in series with a gaseous discharge lamp 15 which includes a capacitor 21 connector in parallel therewith. Capacitive gaseous discharge unit 14 includes a capacitor 23 connected in series with a gaseous discharge lamp 15 which, in turn, is connected in parallel with the series combination of inductor 24 and capacitor 25. 
     In the inductive and capacitive gaseous discharge lamp units 13 and 14 the following values were obtained for use in a system operable at a nominal frequency of 28.5 kilohertz; 
     
         ______________________________________Reference Character           Component______________________________________19              1.70 millihenry inductor20              .66 microfarad capacitor21              .0166 microfarad capacitor23              .022 microfarad capacitor24              1.7 millihenry inductor25              .66 microfarad capacitor15              Sylvania Type F13DTT gaseous           discharge lamp (13 watt, 65           volts line voltage).______________________________________ 
    
     It may be noted that capacitors 20 and 25 are connected in series with inductors 19 and 24 respectively and are preferably more than ten times the capacity of capacitors 21 or 23. 
     Referring to FIG. 1 of the drawings a schematic and diagrammatic representation of a typical power supply, such as indicated by reference character 10, may include a source of DC power 28 operably connected to a control means 31 and to an oscillator 30 that is in turn connected to an inverter 27 having an alternating current output of approximately 28.5 kilohertz for connection to gaseous discharge lamp units 13 and 14 and to an output current sensing means 29. 
     As set forth below, the source of DC power may be, for example, a battery, as might be encountered in many portable power supply systems in trucks, boats, etc., or an AC power rectifying means as may be used in typical residential or commercial applications normally connected to commercial alternating power networks. It will also be seen that the two examples of power supplies set forth below in FIGS. 3 and 4 have common elements whereas one or the other may require fewer or more functions for satisfactory operation. 
     However, at this point in the description of my invention, it may be seen that a plurality of essentially like numbers of inductive and capacitive gaseous discharge lamp units 13 and 14 are connected in parallel to the output of a variable energy power supply, indicated generally by reference character 10. The values of the components are selected so that none of the gaseous discharge lamp units 13 or 14 will be resonant at the nominal operational frequency of a given system, in the case of the present embodiment, 28.5 kilohertz. Another way of describing the frequency characteristics of lamp units 13 and 14 is that they are designed to present a resonant frequency characteristic that is greater or less than the nominal operational frequency of high frequency power supply 10 by a factor or more than 10%. 
     While the illustrated embodiment shows gaseous discharge lamps 15 (FIG. 2) as including filaments, it is anticipated that other forms such as low pressure sodium, &#34;instant start&#34; fluorescent and high pressure lamps, such as the &#34;Brite Arc&#34; marketed by Sylvania may be used. 
     The operation of my system will be described first assuming all of the gaseous discharge lamp units have been satisfactoritly energized and are emitting light energy at the highest level possible. If this is what is desired by the user, no further action is required. However, under many conditions of operation, the user desires to reduce the amount of illumination as by dimming the gaseous discharge lamp units to a desired level and, in this event, control 31 is utilized to reduce the voltage supplied from power supply 10 and the level of illumination output of gaseous discharge lamp units may be reduced to a value considerably less than 50% of the maximum level. Typically, this is accomplished by reducing the direct current voltage level of source 28 to inverter 27 (as in FIG. 3 of the drawings, and maybe accomplished by connecting a transformer or the like (not shown) to the output terminals 11 and 12 of inverter 27 to thereby vary the voltage level of the high frequency alternating current energy). 
     In the event of a malfunction or the existence of a transient condition which may cause the load connected to power supply 10 to draw a current greater than a predetermined maximum value related to the capacity of power supply 10, current sensing means 29 is operable to turn power supply 10 to an off condition. This is typically accomplished by inhibiting the operation of oscillator 30 on a temporary or permanent basis. When the operation of oscillator 30 is inhibited on a temporary basis, such as many occur during a momentary overload condition when the system is initially started, or energized, control 31 may be operable to temporarily reduce the level of energy supplied to inverter 27 from DC power source 28 and to allow the level to increase to the maximum value at a rate determined by a timing circuit (to be described below) so as to permit ignition of all of the gaseous discharge lamp units connected in the system. 
     In an operative embodiment utilizing the power supply of FIG. 3A-C and gaseous discharge lamps 15, a system has been operational in which the voltage applied to the gaseous discharge lamp units has been in the neighborhood of the typical running voltage, such as 65 volts for full illumination at the onset of initiation of operation.) Each of the gaseous discharge lamp units will then operate to provide an increased level of voltage across each of the lamps 15 contained therein, and each of the units will become operational in a more or less random sequential manner which has been observed to be in a non-predetermined sequence so that the current load remains at a low-average level and the current capacity of power supply 10 is not exceeded. However, should the current capacity, of a predetermined level as determined by, for example, current sensing means 29, be exceeded, oscillator 30 will be shut down and the starting sequence reiniated by reducing the voltage below the normal running voltage and allowing it to increase in a ramped, or gradual fashion, to assist in ensuring that the individual lamp units start in a random sequence. 
     Following the ramping of the applied potential, or voltage, control 31 may be operable to reduce the voltage to that desired by the user of the system so that the individual lamp units may be dimmed to a desired level of illumination. The time for &#34;ramping&#34; or starting the lamp units of a system may be in the range of 1/8 to 3 seconds. 
     Referring to FIGS. 3A, B, and C, a complete power supply is shown including an inverter 27, a source of direct current power 28, current sensing means 29, an oscillator 30 and a control 31. 
     While the disclosure of the composite schematic diagram of FIG. 3A-C is believed straightforward, a number of the components and their values are identified for the convenience of those skilled in the art in practicing my invention; 
     
         ______________________________________Reference Character           Component______________________________________36              Signetics type SG 3526N           integrated circuit37              Type 2N4403 transistor38              Type 2N7646 transistor39              Type 2N4403 transistor40              Type 2N4992 SCR41, 42          Type MTP8N20 FET transistors43              RCA type S4060M SCR44              1 microfarad capacitor45              270K ohm resistor46              20 microfarad capacitor47              270K ohm resistor48              5K potentiometer49              5K ohm potentiometer50              .1 microfarad capacitor51              417K ohm resistor52              1N4404 diode53              1N4404 diode54              1N4004 diode55              1N4004 diode56              20 V, 1 V Zener diode57              500 ohm potentiometer58              3.3K ohm resistor59              10K ohm resistor60              5.3K ohm resistor61              1K ohm potentiometer62              5 meg ohm potentiometer63              1N4004 diode64              200 microfarad capacitor65              5K ohm resistor66              1N4004 diode______________________________________ 
    
     Integrated cirucuit 36 is shown having a plurality of numbered terminals which are connected to and interconnected with the following compontents; 
     
         ______________________________________Reference Character            Component______________________________________70               22K ohm resistor71               10K ohm resistor72               1K ohm potentiometer73               1.8K ohm resistor74               100 ohm resistor75               2204F microfarad capacitor76               .005 microfarad capcacitor77               22K ohm resistor78               22K ohm resistor79               47K ohm resistor80               88 ohm resistor81               36K ohm resistor82               .01 microfarad capacitor83               3.3K ohm resistor______________________________________ 
    
     Other components in FIG. 3 may be indentified as follows, inverter 27; 
     
         ______________________________________Reference Character             Component______________________________________86                input transformer87                output transformer88                33 ohm resistor89                33 ohm resistor90                10K ohm resistor91                10K ohm resistor92                1N4936 diode93                33 ohm resistor94                150 picofarad capacitor95                1N4936 diode96                33 ohm resistor97                150 picofarad capacitor98                68K ohm resistor99                220 microfarad capacitor100               68K ohm resistor101               200 microfarad capacitor102               current transformer______________________________________ 
    
     In current sensing means 29; 
     
         ______________________________________Reference Character             Component______________________________________103               1K ohm potentiometer104               47 microfarad capacitor105               10K ohm resistor106               2N4992 diode107               10K ohm resistor108               .01 microfarad capacitor______________________________________ 
    
     Control circuit 31 provides for a dimming control through the adjustment of potientiometer 49 and the duty cycle of SCR 43 in DC power source 28 is thereby determined so as to effect control of the dimming. 
     In the embodiment of FIG. 3A-C, capacitor 75 is connected to terminal 4 on integrated circuit 36 to provide for a &#34;soft&#34; startup, or a &#34;ramping&#34; of the voltage rise of terminal 4 upon initial energization or connection of the apparatus of FIG. 3A-C to a source of alternating current. Capacitor 75 is discharged when power is turned off so that the &#34;soft&#34; start or &#34;ramping&#34; is restored to be available for the next starting procedure. 
     Referring to FIGS. 3A-C, the illustrated power supply, 28, is intended to be operational from a commercial power grid typically supplying a relatively low voltage, 100 volts, 60 cycle alternating current. This is connected to appropriate rectifiers through suitable filter means to provide DC power for control 31 and oscillator and 30 on one hand and converter 27 on the other hand. It may be noted that the level of power that may be supplied to converter 27 is controlled by the operation of SCR 43 in power supply 28, that is in turn controlled by the secondary winding of transformer T1, having a primary winding connected to semi-conductor 38 in control 31. An overcurrent shutdown is provided by the current sensing portion 29 of FIG. 3 and is operable to disable integrated circuit 36 in oscillator 30 at such time as a predetermined output current is exceeded. 
     The operation of control 31 is inhibited when the power supply of FIGS. 3A-C is initially started so as to provide full voltage to the lamp units to be energized. This is accomplished by rendering transistor 39 conductive for a predetermined time depending upon the time interval determined by capacitor 46 connected to transistor 37. 
     The following is a table of values for the various components utilized in the schematic drawing of FIGS. 4A-D. 
     
         ______________________________________Reference Character           Component______________________________________110             Output transformer111, 112        Input power terminals for           connections to a source of DC           power113             2.00 microfarad capacitor114             2.00 microfarad capacitor115             1.5KE39A diode116             1.5KE39A diode117             220 ohm resistor118             220 ohm resistor119             Type 1N 4936 diode120             Type 1N 4936 diode121             .01 microfarad capacitor122             .01 microfarad capacitor123             Type MTP3055A transistor124             Type MTP3055A transistor125             220 ohm resistor126             220 ohm resistor127             Type MTP3055A transistor128             Type MTP3055A transistor129             220 ohm resistor130             220 ohm resistor131             .33 microfarad capacitor132             .33 microfarad capacitor133             Type 2N 3706 transistor134             Type 2N 3706 transistor135             Type 2N 4403 transistor136             Type 2N 4403 transistor137             220 ohm resistor138             220 ohm resistor139             Type 2N 4403 transistor140             Type 2N 4403 transistor141             22 ohm resistor142             22 ohm resistor143             82 ohm resistor144             82 ohm resistor145             300 ohm resistor146             300 ohm resistor147             2.2K ohm resistor148             2.2K ohm resistor149             Type 2N 4403 transistor150             10K ohm resistor151             2.2K ohm resistor152             47K ohm resistor153             22K ohm resistor154             22K ohm resistor155             22K ohm resistor156             1K potentiometer157             470 ohm resistor158             .02 microfarad capacitor159             .005 microfarad capacitor160             Terminal for connection to a           source of positive direct           current voltage, nominally 12           volts161             Type 3524B integrated circuit           --oscillator162             Transformer163             470 ohm resistor164             Full wave rectifying bridge           comprised of type 1N 4001           diodes165             .47 microfarad capacitor166             1K ohm potentiometer167             22K ohm resistor168             Type 2N 4992 diode169             2.2K ohm resistor170             C103 SCR171             470 ohm resistor172             220 microfarad capacitor173             Type 1N 4000 diode174             100K ohm resistor175             10K ohm resistor176             Type 1N 4000 diode177             4.7K ohm resistor178             Type 2N 3706 transistor179             10K ohm resistor180             2.2K ohm resistor181             Type 2N 3706 transistor182             47K ohm resistor183             10K ohm resistor184             .47 microfarad capacitor185             Type 1N 4000 diode186             22K ohm resistor187             Type 2N 4992 diode188             2.2K ohm resistor189             Type C103 SCR190             470 ohm resistor191             Light emitting diode192             Type 1N 4000 diode193             Type 723 integrated circuit194             .068 microfarad capacitor195             15K ohm resistor196             .47 microfarad capacitor197             1K ohm resistor198             1K ohm potentiometer199             470 ohm resistor200             22K ohm resistor201             .01 microfarad capacitor202             Type 2N 4992 diode203             Type 1N 753 diode204             Light emitting diode205             470K ohm resistor206             2.2K ohm resistor207             Type 103 SCR208             Type 1N 4000 diode209             470 ohm resistor210             Type 723 integrated circuit211             .068 microfarad capacitor212             10K ohm resistor213             4.7K ohm resistor214             1K ohm resistor215             1K ohm potentiometer216             1K ohm resistor217             .47 microfarad capacitor218             10K ohm resistor219             Type 2N 4403 transistor220             2.2K ohm resistor221             85 ohm resistor222             Type 1N 4745A diode223             2.2K ohm resistor224             Type C103 SCR225             470 ohm resistor226             Light emitting diode227             Type 1N 4000 diode228             Type 1N 4000 diode______________________________________ 
    
     FIGS. 4A-D are similarly identified as including a convertor 27, current sensing means 29 and an oscillator 30, all of which is connected to a source of direct current energy, such as a battery (not shown). 
     The operation of the illustration of FIGS. 4A-D is generally similar to that described above in connection with FIGS. 1 and 3A-C and for specific details of operation, resort may be had to the fabrication of the apparatus therein illustrated. 
     In the power supply of FIGS. 4A-D, capacitor 172 is utilized to provide the &#34;ramping&#34; or &#34;soft&#34; start, gradually rising drive characteristics for oscillator 30 comprised of integrated circuit 161. The &#34;ramping&#34; on the initial startup is repeated each time the apparatus is shut down as for example, by disconnection from the power supply or by the sensing of an overcurrent at the output of convertor 27 at terminals 11 and 12.