US2856563A - Starting circuit for lamps - Google Patents

Description

Oct. 14, 1958 C. M. RIVELY STARTING CIRCUIT FOR LAMPS Filed April 16, 1953 GAS OR VAPOR LAMP GAS OR VAPOR LAMP INVENTOR CLAIR MIOIAEL RIVELY United States Patent STARTING CIRCUIT FOR LAMPS Clair Michael Rively, Rockaway, N. J., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application April 16, 1953, Serial No. 349,179 Claims. (Cl. 315-205) This invention relates to starting circuits for lamps containing ionizable atmospheres and more particularly for such lamps which have cold cathodes.

It is well known that gas and vapor lamps have a small resistance while they are conducting, and although the voltage drop across the lamp may be constant, it is also small. Contrasted with this are the high voltages which are required for these lamps to are and start conducting.

In the past, it has been common practice to heat the electrodes (cathodes) of these lamps to reduce the starting voltages required. By heating, the cathodes were caused to emit electrons and these electrons, accelerated by the line voltage applied to the lamp, ionized the gas or vapor molecules contained in the lamp until there was sufficient ionization to support a columnar discharge. Automatic switches were used to deenergize the cathodes either after a predetermined period of time or after conduction had started in the lamp. The heating of the cathodes required a noticeable period of time and this delay in the lighting of the lamps and the erratic action of the automatic switches is well known.

Cold cathode starting of such lamps, to this time, has not been feasible, particularly in starting high intensity lamps such as those used for motion or still picture projection, for searchlights, and for highway lighting. These lamps quite often contain a gas or vapor which is under many times atmospheric pressure and voltages of the order of 40,000 or 50,000 volts are often required to ionize these lamps.

An object of this invention is to provide starting circuits for gas or vapor filled lamps, which circuits overcome the disadvantages stated above.

Another object of this invention is to provide reliable starting circuits for lamps containing ionizable atmospheres, which circuits provide instantaneous starting without the use of mechanical switches.

Other objects and advantages of the invention will hereinafter becomes more fully apparent from the following description of the annexed drawings, which illustrate a preferred embodiment, and wherein:

Fig. l is a schematic illustration of a circuit embodying this invention in which the lamp is operated by alternating current; and

Fig. 2 is a schematic illustration of a circuit embodying this invention in which the lamp is operated by direct current.

Referring now to Fig. l in detail, terminals 10 are provided for connecting a lamp 11 to a source of alternating current 12 through a ballast 13 by means of leads 14 and 15. This is the normal supply circuit for a gas or vapor lamp.

The starting circuit of this invention as illustrated in Fig. 1 comprises a step-up transformer 16 Whose primary winding 17 and a capacitor 19 are connected in series across the leads l4 and at a point between the ballast 13 and the lamp 11. The value of the capacitor 19 is such that, with full line voltage across the primarycapacitor series branch, this branch is tuned at the line frequency. The secondary winding 18 of the transformer 16 forms a part of an oscillatory loop 20 and is connected in series with an electric discharge device 21 (shown as a spark gap), and a capacitor 22 is connected in parallel with the secondary winding 18. A pulse transformer 23 has it primary winding 24 in the loop 20 in series with the secondary Winding 18 and the discharge device 21. The secondary winding 25 of the pulse transformer 23 is inserted in the line 14 inseries with the lamp 11 and across it is connected a protective spark gap 26. Across the lines 14-15, adjacent the ballast 13, is connected a capacitor 27 which acts as a return or filter for any high frequency oscillations produced in the starting circuit. A single connection 30 is provided between the primary winding 17 and the secondary winding 18 to prevent the oscillatory loop 20 from floating.

When the lamp 11 is not lit, no current flows through the ballast 13 and full line voltage is applied across the primary winding 17 and the capacitor 19 by the supply lines 14 and 15. The primary winding 17 and the capacitor 19 resonate and a high voltage is produced across the primary 17. The high voltage in the primary winding 17 induces a still higher voltage in the secondary winding 18 of the transformer 16. The capacitor 22 is charged until the voltage across it approaches the open circuit voltage of the secondary 18,. at which time the discharge device 21 arcs over and conducts, discharging the capacitor 22. A high frequency current flows in the oscillatory loop 20 which in turn induces very high voltage pulses in the secondary winding 25 of the pulse transformer 23. These pulses are applied to the lamp 11 and ionize the atmosphere within the lamp to ignite it. The protective gap 26 is set at a value somewhat higher than the voltage required to start lamp 11 so that, if the lamp fails to ignite or if there is no lamp in the circuit, the gap will arc and dissipate the energy of the secondary 25 before the voltage can build up to a destructive value. The capacitor 27 forms a return path for the high frequency, high voltage starting pulses which are applied to the lamp and therefore tends to keep these pulses out of the alternating current source 12.

In an iron-core transformer, the inductances of the windings varies with the value of the currents flowing through them. Thus, when the voltage applied to the primary 17 changes, the current flow through it and its inductance both change. This change in the inductance of the primary 17 causes it to cease resonating with the capacitor 19, and the voltage induced in the secondary 18 is insufficient to cause the breakdown of the discharge device 21. This occurs when the lamp 11 lights.

Fig. 2 illustrates a modification of the circuit of Fig. 1 for use where it is desired to operate the lamp from a direct current source. The same reference numerals are used in Fig. 2 for those elements which are identical to the elements shown in Fig. 1. In this circuit, a lamp 11 containing an ionizable atmosphere is fed from a source of direct current 31. A saturable core step-up transformer 32 has a direct current saturating winding 34 connected across the ballast 13 and a primary winding 33 connected to a source of alternating voltage 37 through a series capacitor 36. The secondary 35 of the saturating transformer 32 forms a part of an oscillatory loop 20. Across the secondary winding 35 is connected a capacitor 22.

As in the operation of the device of Fig. 1, when the lamp 11 of Fig. 2 is not lit, the primary winding 33 of the transformer 32 and the capacitor 36 are in series resonan'ce and a large alternating voltage is produced across the primary winding 33. This voltage is multiplied by the action of the transformer, and across the secondary winding 35 there is induced a voltage several times that of the source 37 which, as explained above with respect to Fig. 1, causes the oscillatory loop 20 to generate highfrequency voltages and produce high voltage pulses in the secondary winding 25 to light the lamp 11.

When the lamp 11 conducts, a voltage drop, due to the lamp current flowing through the ballast i3, is produced across the ballast 13 and current flows through the saturating winding 34 of the transformer 32 thereby changing the inductance values of the transformer. When the inductance of the primary winding 33 is changed, it no longer resonates with thecapacitor 36, and the voltage of the primary winding 33, and consequently that of the secondary winding 35, is reduced. The value of the voltage across the capacitor 22 is then insufficient to cause the breakdown of the discharge device 21 and loop 20 ceases oscillation.

The above described circuits have proved to be reliable starting circuits for high intensity lamps containing mercury at pressures in the order of atmospheres and which required voltages in the order of 50 kilovolts for starting. These circuits are automatic, positive in their operation, require no moving parts and consume but negligible. power.

Obviously, many modifications and variations of this invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A lamp which contains an ionizable atmosphere in combination with a starting circuit therefor, said circuit comprisingv terminals for connecting said lamp to a source of direct current; a ballast in series with said lamp; a first transformer comprising a first primary winding, a first secondary Winding, and a saturating winding; terminals for connecting said first primary winding to a source of alternating voltage, said saturating winding being connected across said ballast; a second transformer comprising a second primary winding and a second secondary winding; and an oscillatory loop, said loop comprising said first secondary winding, said second primary winding, and an electric discharge device in series; said sec ond secondary winding being connected in series with said lamp.

2. A lamp which contains an ionizable atmosphere in combination with a starting circuit therefor, said circuit comprising first terminals for connecting said lamp to a source of direct current; a ballast connected in series between one of said terminals and said lamp; a saturating transformer comprising a first primary winding, a first sec? ondary winding, and a saturating winding; said saturating winding being connected across said ballast; a pulse transformer comprising a second primary winding and a second secondary winding; a spark gap; an oscillatory loop comprising said first secondary winding, said spark gap and said second primary winding connected in series; a capacitor in parallel with said first secondary winding; said second secondary winding being connected in series with said lamp; second terminals for connecting said first primary winding to a source of alternating voltage; and a tuning capacitor in'series between said second terminals and said first primary winding.

3. An improved device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere, comprising: an operating circuit that includes conducting means and a ballast for conveying lamp operating current, an oscillatory means for accepting power conveyed thereto only when the voltage thereof exceeds a predetermined minimum voltage and for converting accepted input power to high frequency power, said oscillatory means coupled at its output to said operating circuit for providing high frequency lamp igniting power to said operating. circuit, and means for conveying power at a voltage exceeding said predetermined minimum voltage to the input of said oscillatory means and coupled to said ballast and responsive to flow of lamp operating current through said ballast to reduce automatically the voltage at the input of said oscillatory means below said predetermined minimum after said lamp is ignited, whereby said oscillatory means does not provide high frequency power to said operating circuit nor dissipate power within itself when said lamp is operating.

4. A device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as defined in claim 3 wherein said means for conveying power to said oscillatory means includes a transformer having a saturable core, the secondary of said transformer being coupled to said oscillatory means, and a condenser connected in series with the primary of said transformer and series resonant therewith at a particular frequency and at a particular flux density in the transformer core for conveying power at a voltage exceeding said predetermined minimum voltage to said oscillatory meanswhen the flux density in the transformer core is equal to said particular flux density, the flux density in the transformer core being responsive to flow of lamp operating current to render non resonant said series-connected transformer primary and said condenser thereby to reduce auto matically the voltage at the input of said oscillatory means below said predetermined minimum after said lamp is ignited.

5. A device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as defined in claim 3 wherein said oscillatory means includes an inductive reactance in series with a spark gap and a capacitive reactance connected across the seriesconnected inductive reactance and spark gap, whereby energy can oscillate at a high frequency between said inductive reactance and said capacitive reactance only when there is discharge across said spark gap, magnetic coupling means between said inductive reactance and said operating circuit to transfer high frequency power from said oscillatory means to said operating circuit, said means for conveying power to said oscillatory means being coupled to opposite ends of the parallel-connected combination of said capacitive reactance and series-connected inductive reactance and spark gap.

6. A device. for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as defined in claim 4 wherein said oscillatory means includes an inductive reactance in series with a spark gap and a capacitive reactance connected across the seriesconnected inductive reactance and spark gap whereby energy can oscillate at a high frequency between said inductive reactance and said capacitive reactance only when there is a discharge across said spark gap, magnetic coupling means between said inductive reactance and said operating circuit to transfer high frequency power from said oscillatory means to said operating circuit, the secondary of said transformer being coupled to opposite ends of the parallel-connected combination of capacitance and series-connected inductance and spark gap.

7. An improved device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as definedin claim 4 wherein the series-connected transformer primary and condenser are connected across said operating circuit on the lamp side of said ballast.

8. An improved device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as defined in claim 6 wherein the series-connected transformer primary and condenser are connected across said operating circuit on the lamp side of said ballast.

9. An improved device for conveying igniting and operating power to a lamp of the type containing an ionizable atmosphere as defined in claim 4 wherein said transformer further includes a coil which is connected directly across said ballast.

10. An improved device for conveying igniting and operating power to a lamp of the type'containing an ionizable atmosphere as defined in claim 6 wherein said transformer further includes a coil which is connected directly across said ballast.

References Cited in the file of this patent UNITED STATES PATENTS Ucar Apr. 24, 1923 Miller June 9, 1936 Edwards Jan. 3, 1939 Edgerton Aug. 16, 1949 Ankenman Jan. 17, 1950 Lord May 23, 1950 Breeding Nov. 8, 1955

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