USRE32904E - Power supply for gas discharge devices - Google Patents
Power supply for gas discharge devices Download PDFInfo
- Publication number
- USRE32904E USRE32904E US07/204,421 US20442188A USRE32904E US RE32904 E USRE32904 E US RE32904E US 20442188 A US20442188 A US 20442188A US RE32904 E USRE32904 E US RE32904E
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- transistor
- base
- supply circuit
- winding
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
- H05B41/14—Circuit arrangements
- H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
- H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
- H05B41/282—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices
- H05B41/285—Arrangements for protecting lamps or circuits against abnormal operating conditions
- H05B41/2851—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the circuit against abnormal operating conditions
Definitions
- This invention relates to a low current, high voltage power supply for neon signs or other similar gas discharge devices and in particular to a solid state power supply which is far more efficient and less costly than conventional high voltage transformers used to excite gas discharge devices.
- Gas discharge devices such as tubes for neon signs, require a high voltage, typically between five to ten thousand volts or more, to stimulate the gas atoms therein sufficiently to emit radiation in the visible spectrum.
- a high voltage typically between five to ten thousand volts or more
- such high voltages are generally produced by a low frequency step-up transformer connected to a standard 60 Hz power line.
- the resulting transformers are expensive, heavy and generally bulky.
- the power supply of the invention utilizes a unique solid state free-running power oscillator to generate a high frequency power signal which drives a compact, light-weight high frequency transformer.
- the transformer delivers a sufficient high voltage to excite the inert gas within a gas-filled tube in order to cause it to produce light. In this manner, the conventional bulky, low frequency step-up transformer is eliminated.
- the transformer is of the type having leakage reactance. It has a primary winding, a feedback winding, and a secondary winding connected to the gas-filled tube.
- a transistor is employed, having its collector connected to the transformer primary winding and its base connected to the transformer feedback winding to provide a base current drive. When voltage is applied to the base of the transistor, the transistor conducts until the transistor comes out of saturation from increasing collector current.
- a solid state switch is connected to the primary winding and is activated when the transistor comes out of saturation in order to remove the base drive to render the transistor non-conductive. The switch also provides a path for rapid evacuation of charge carriers stored in the base-emitter junction of the transistor to rapidly render the transistor non-conductive.
- the switch comprises a second transistor having its base connected to the transformer primary winding and its collector connected to the base of the first transistor in order to provide the rapid evacuation path for the base-emitter junction of the first transistor.
- the emitter of the second transistor is directly grounded.
- FIG. 1 is a schematic circuit diagram of one embodiment of the invention.
- FIG. 2 illustrates representative current and voltage wave forms produced by the circuit of FIG. 1.
- the neon sign supply of the invention is shown generally at 10 in FIG. 1.
- the supply 10 includes a power supply 12, a start-up circuit 14, a high frequency oscillator 16 connected to an output load 18, typically a neon tube or other similar device and a safety bypass circuit 17.
- the power supply 12 consists of a bridge rectifier 20 and a filter capacitor 22.
- the rectifier 20 is connected to a conventional 120 volt alternating current supply (not illustrated) through leads 24 and 26.
- the positive output of the power supply 12 is directed on line 28 to the start-up circuit 14 and the oscillator 16, while the negative output of the power supply 12 is connected to "ground" of the neon supply 10.
- the start-up circuit 14 consists of the parallel combination of a capacitor 32 and resistor 34 connected at one end to the line 28 and at the other end in series with a resistor 36.
- the resistor 36 is connected through the parallel combination of a charging capacitor 38 and resistor 39 to the ground 30. It is also connected to a diac 40 in series with a current limiting resistor 42 on a line 44 leading to the oscillator 16.
- the start-up circuit 14 operates as a relaxation oscillator in which the capacitor 38 is charged until the voltage across the capacitor 38 exceeds the threshold trigger voltage of the diac 40. The diac 40 then conducts, and when the current through the diac 40 has substantially stopped due to completion of the charge on the capacitor 38, the diac switches off, commencing a new and repetitive charge cycle. If the oscillator 16 is not previously in oscillation, the repetitive discharge cycles of the diac 40 initiate such oscillation.
- the frequency of oscillation of the start-up circuit 14 is not critical, generally and preferrably having a period initially of 200 Hz and later settling to a steady state of 10 to 20 Hz.
- the oscillator 16 is a free-running high frequency oscillator comprising a power transistor 46, a low voltage switch transistor 48, an output and feedback transformer 50, and associated biasing and triggering circuit elements. It is preferred that the oscillator 16 nominally operate under load at a frequency of 25 KHz.
- the power transistor 46 is of a common type having collector-emitter breakdown voltage rating of approximately 1500 volts and a maximum collector current nominally of 2.5 amperes. Such a transistor is commonly found in a television horizontal output circuit, and transistors having a collector current between two and seven amperes are suitable in this invention.
- the collector of the transistor 46 is connected to the positive output line 28 of the power supply 12 through the primary 52 of the transformer 50.
- the base of the transistor 46 is connected through a biasing network 54 and a diode 56 to a transformer feedback winding 58, while the emitter of the transistor 46 is connected to ground through an emitter biasing network 60.
- the emitter biasing network 60 comprises the parallel combination of a resistor 62 and a by-pass capacitor 64.
- the capacitor 64 functions as a low impedance by-pass capacitor at the frequency of oscillation of the network 60, thereby producing a substantially constant direct current voltage at the emitter of the transistor 46.
- the resistor 62 can be replaced by a positive temperature coeffient resistance element which increases in resistance as a voltage across the element increases, such as a standard incandescent lamp. Substituting such a device for the resistor 62 permits the potential across the emitter bias network 60 to be varied as necessary to compensate for changing load and temperature conditions.
- the base bias network 54 is connected to the base of the transistor 46 and comprises the parallel combination of a by-pass capacitor 66 and a resistor 68. Similar to the biasing network 60, the resistor 68 may be replaced by an incandescent lamp to permit variance of the potential across the biasing network 54 as necessary. In addition, the resistor 68 can be replaced by a variable resistor or may be used in series with a variable resistor in order to set the quiescent biasing level of the transistor 46.
- the transformer 50 includes the primary 52, the feedback winding 58 and a secondary winding 70. Although illustrated only schematically in FIG. 1, the transformer is preferrably formed such that the windings 52, 58 and 70 are provided on a generally rectangular ferrite core comprised of two opposed U-shaped pieces formed to create a 0.05 inch air gap between respective adjacent ends of the U-shaped core members.
- the number of turns of each of the windings is set forth below in a table illustrating representative values of the various elements of the neon supply 10.
- the number of turns in the primary 52 is set, and the air gap is adjusted large enough to avoid core saturation and to establish a given inductance in the primary winding 52 which, in turn, establishes the frequency of oscillation of the oscillator 16, in conjunction with capacitor 72.
- the secondary-to-primary turns ratio is selected according to conventional transformer relationships to provide the requisite output voltage to excite the output load 18.
- Neon and other similar gas discharge tubes are known to possess a highly non-linear voltage-current characteristic wherein substantially no current passes through the tube until the threshold excitation voltage is achieved and, thereafter, substantial and excessive currents may result unless means for limiting such current are provided.
- a pure "constant voltage" power source without current limiting is unsatisfactory for use with gas discharge tubes.
- the geometry of the transformer 50 may be designed to provide the voltage source of this invention with inherent current limiting which functions, in essence, as a constant source under the low load resistance presented by an excited gas discharge tube. This feature is achieved in a conventional manner by positioning the primary 52 and secondary 70 windings on different poles of the transformer core thereby producing a leakage reactance between these windings. Thus, even under the most severe loading conditions (a short circuit of the output of the transformer 50), the maximum current is limited by this leakage reactance.
- the feedback winding 58 of the transformer 50 is connected through the diode 56 and the bias network 54 to the base of the transistor 46. As seen, the feedback winding 58 is also connected through the diode 56 to the collector of the transistor 48, for reasons described in greater detail below.
- the number of turns of the feedback winding 58 is selected to assure adequate feedback for oscillation and, more particularly, to force the transistor 46 into saturation over a substantial portion of each cycle as required to produce sufficient power output to drive the load 18.
- the diode 56 is positioned between the feedback winding 58 and the base bias network 54 in such polarity to generally block the reverse flow of current through the winding 58.
- the diode 26 preferrably is a fast recovery type of diode to prevent an instantaneous reverse current from flowing following initial reverse biasing of the diode.
- the primary winding 52 is connected to the base of the transistor 48 through a blocking and primary resonating capacitor 72.
- a resistor 74 and diode 76 are also attached to the base of the transistor 48, and the emitter of the transistor 48 is connected to the ground 30.
- the diode 76 is a clamping diode which limits the maximum base-to-emitter voltage of the transistor 48 to assure that the emitter-base breakdown voltage of the transistor 48 is not exceeded.
- the resistor 74 is connected in parallel with the diode 76 to provide a low impedance path effectively across the emitter-base junction of the transistor 48, thereby shunting, in a conventional manner, the collector-to-emitter leakage current of the transistor 48.
- the purpose of the transistor 48 is to aid in rapid turn-off of the transistor 46.
- the base biasing current is removed from the base of the transistor 46, charge carriers stored in the base-emitter junction of the transistor 46 normally remain, and are recombined in a natural recombination process. This recombination process results in a substantial turn-off delay and therefore gradual and dissipative turn-off of the transistor 46.
- the transistor 48 being biased to conduct at the instant of desired turn-off of the transistor 46, the charge carriers stored in the base-emitter junction of the transistor 46 are rapidly evacuated through base-emitter reverse bias from the biasing network 54 and the conducting transistor 48.
- the rapid evaculation of the base-emitter junction of the transistor 46 occurs in a time period much shorter than that required for the natural recombination process, aiding the rapid turn-off of the transistor 46.
- the safety bypass circuit 17 causes the remainder of the supply 10 to revert to a low energy pulse mode which prevents any ensuing burns or a fire.
- the secondary winding 88 of the transformer 84 is connected to a diode 90 whose output is directed to a filter capacitor 94, and the gate cathode of a triac or silicon controlled rectifier 96.
- a triac is preferred.
- the triac 96 is connected to the feedback winding 58 of the transformer 50 and to the ground 30.
- the operation of the neon sign supply 10 is best illustrated and understood by reference to the curves of FIG. 2 in combination with the illustrated and described circuit of FIG. 1.
- the start-up circuit 14 When connected, line voltage on the leads 24 and 26 is rectified by the bridge 20 and appears across the capacitor 22.
- the start-up circuit 14 generates a series of pulses to initiate oscillation of the oscillator 16.
- the start-up circuit Preferably, the start-up circuit generates pulses at a frequency of 200 Hz, settling to a steady-state pulse generation of between 10 and 20 Hz.
- the pulses of the start-up circuit 14 have a negligible effect and may continue without altering oscillation of the oscillator 16.
- the curves shown in FIG. 2 are illustrated at various times designated T 0 , T 1 , T 2 , etc.
- the times indicated are not intended to represent any time value, but are merely to illustrate the relative values and polarities of circuit currents and voltages at any particular instant of time.
- the collector voltage V C begins to rise rapidly as the current I L begins to drop, and the negative base current I B begins to diminish. Since the transistor 46 remains in a non-conducting state, as the current I L continues to decrease, the collector voltage V C of the transistor 46 reaches a maximum at time T 3 , at which time the collector voltage begins to decrease. At the same time, the sign of dVc/ dt changes, reversing current through the transistor 48 emitter-base junction, causing the transistor 48 to cease conducting. The current I L in the primary 52 then goes negative, and the collector voltage V C of the transistor 46 decreases to zero, as the reverse current in the primary 52 reaches its maximum negative value.
- Osillation of the oscillator 16 is therefore halted. Once the oscillator 16 is halted, it is not restarted until another pulse is received from the diac 40, a period of several hundred milliseconds. If the fault condition across the secondary winding 70 has not cleared, a new pulse from the diac 40 only causes a new fault current, thus repeating the above sequence of initiation of the safety bypass circuit 17. The resulting continual repetition of activiation of the safety bypass circuit 17 prevents any significant power output level of the transformer 50.
- the output voltage of the transformer 60 can be altered in a well-known manner.
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Abstract
Description
______________________________________ TABLE OF COMPONENT VALUES ComponentValue ______________________________________ Transistor 46 1500 V collector-emitter, 2.5 A collectorcurrent Transistor 48 low voltage, 3.0 A switch Transformer 50 Primary 52 99 turnsFeedback 58 4 turns Secondary 70 3,400 turnsCapacitor 22 300microfarad Capacitor 66 470microfarad Resistor 68 10ohm Resistor 67 22 ohm Resistor 62 1.5 ohm Capacitor 64 470microfarad Diode 56 Fast recovery 1N4934 Capacitor 72 .033microfarad Resistor 74 1000ohm Diode 76 silicondiode 1N4001 Transformer 84 Primary 82 12 turns Secondary 88 20 turns Core .38" in diameter, with .187" hole and .124" thickness of Ferrite material Diode 901N914 Capacitor 92 4.7microfarad Resistor 94 470 ohmTriac 96 minimum 50 volt, 4-8 A anode current, 5 milliamp gate current ______________________________________
Claims (16)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/204,421 USRE32904E (en) | 1984-03-19 | 1988-06-09 | Power supply for gas discharge devices |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US59086884A | 1984-03-19 | 1984-03-19 | |
US06/637,916 US4613934A (en) | 1984-03-19 | 1984-08-06 | Power supply for gas discharge devices |
US07/204,421 USRE32904E (en) | 1984-03-19 | 1988-06-09 | Power supply for gas discharge devices |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US59086884A Continuation-In-Part | 1984-03-19 | 1984-03-19 | |
US06/637,916 Reissue US4613934A (en) | 1984-03-19 | 1984-08-06 | Power supply for gas discharge devices |
Publications (1)
Publication Number | Publication Date |
---|---|
USRE32904E true USRE32904E (en) | 1989-04-11 |
Family
ID=27394657
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US07/204,421 Expired - Lifetime USRE32904E (en) | 1984-03-19 | 1988-06-09 | Power supply for gas discharge devices |
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US (1) | USRE32904E (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5089752A (en) * | 1990-09-28 | 1992-02-18 | Everbrite, Inc. | High frequency luminous tube power supply with ground fault protection |
US5097182A (en) * | 1990-10-19 | 1992-03-17 | Kelly Allen D | Power supply for a gas discharge lamp |
US5204504A (en) * | 1988-08-26 | 1993-04-20 | Kabushiki Kaisha Toshiba | High-frequency heating apparatus including ringing effect suppressor for switching element |
US5300863A (en) * | 1992-08-14 | 1994-04-05 | Appleton Electric Company | Auxiliary lighting circuit for a gaseous discharge lamp |
US5619105A (en) * | 1995-08-17 | 1997-04-08 | Valmont Industries, Inc. | Arc detection and cut-out circuit |
US5680286A (en) * | 1993-03-09 | 1997-10-21 | Everbrite, Inc | Load fault detector for high frequency luminous tube power supply |
US5696670A (en) * | 1995-05-26 | 1997-12-09 | Webster Heating And Specialty Products, Inc. | Power supply for arc-discharge load |
US5814938A (en) * | 1996-08-05 | 1998-09-29 | Transfotec International | Cold cathode tube power supply |
Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3662249A (en) * | 1969-09-18 | 1972-05-09 | Philips Corp | Dc-ac converter |
US3700956A (en) * | 1971-01-04 | 1972-10-24 | Gte Laboratories Inc | Arc discharge lamp control circuit |
US3753075A (en) * | 1971-07-06 | 1973-08-14 | Hitachi K Ltd | Inverter |
US3978390A (en) * | 1974-07-03 | 1976-08-31 | U.S. Philips Corporation | Dc-ac inverter for supplying a discharge lamp |
US4220987A (en) * | 1978-12-29 | 1980-09-02 | Bell Telephone Laboratories, Incorporated | Converter drive circuit |
US4316242A (en) * | 1980-09-04 | 1982-02-16 | General Electric Company | Wide input range, transient-immune regulated flyback switching power supply |
US4443838A (en) * | 1980-12-01 | 1984-04-17 | Omron Tateisi Electronics Co. | Regulated single-ended self oscillating, DC-DC converter |
-
1988
- 1988-06-09 US US07/204,421 patent/USRE32904E/en not_active Expired - Lifetime
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3662249A (en) * | 1969-09-18 | 1972-05-09 | Philips Corp | Dc-ac converter |
US3700956A (en) * | 1971-01-04 | 1972-10-24 | Gte Laboratories Inc | Arc discharge lamp control circuit |
US3753075A (en) * | 1971-07-06 | 1973-08-14 | Hitachi K Ltd | Inverter |
US3978390A (en) * | 1974-07-03 | 1976-08-31 | U.S. Philips Corporation | Dc-ac inverter for supplying a discharge lamp |
US4220987A (en) * | 1978-12-29 | 1980-09-02 | Bell Telephone Laboratories, Incorporated | Converter drive circuit |
US4316242A (en) * | 1980-09-04 | 1982-02-16 | General Electric Company | Wide input range, transient-immune regulated flyback switching power supply |
US4443838A (en) * | 1980-12-01 | 1984-04-17 | Omron Tateisi Electronics Co. | Regulated single-ended self oscillating, DC-DC converter |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5204504A (en) * | 1988-08-26 | 1993-04-20 | Kabushiki Kaisha Toshiba | High-frequency heating apparatus including ringing effect suppressor for switching element |
US5089752A (en) * | 1990-09-28 | 1992-02-18 | Everbrite, Inc. | High frequency luminous tube power supply with ground fault protection |
US5097182A (en) * | 1990-10-19 | 1992-03-17 | Kelly Allen D | Power supply for a gas discharge lamp |
US5300863A (en) * | 1992-08-14 | 1994-04-05 | Appleton Electric Company | Auxiliary lighting circuit for a gaseous discharge lamp |
US5680286A (en) * | 1993-03-09 | 1997-10-21 | Everbrite, Inc | Load fault detector for high frequency luminous tube power supply |
US5696670A (en) * | 1995-05-26 | 1997-12-09 | Webster Heating And Specialty Products, Inc. | Power supply for arc-discharge load |
US5619105A (en) * | 1995-08-17 | 1997-04-08 | Valmont Industries, Inc. | Arc detection and cut-out circuit |
US5814938A (en) * | 1996-08-05 | 1998-09-29 | Transfotec International | Cold cathode tube power supply |
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