Abstract: In a fluorescent lamp ballast, a source of high-frequency voltage is applied directly across a series-resonant L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means is operative to prevent the series-resonant L-C circuit from overloading the voltage source during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the series-resonant L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp.

Abstract: A monolithic MOS gate driver chip is described for driving high side and low side power MOSFETs in a gas discharge lamp ballast circuit. The chip includes a timer circuit for generating a square output at the natural frequency of resonance of the lamp ballast. Dead time circuits are provided in the chip to prevent the simultaneous conduction of both high side and low side MOSFETs. The chip may be housed in an eight pin DIP package.

Abstract: A capacitor (16) coupled in series with series coupled gas discharge lamps (11 and 12) will effectively block direct current from flowing through the capacitor (16). A detector circuit including a high impedance resistor (17) and transistor (18) provide an alternate path for a small direct current flow, thereby enabling a direct current voltage across the capacitor (16) to be detected. The presence or absence of this direct current voltage provides a reliable indicia of the existence or absence of a gas discharge fault.

Abstract: A control apparatus for a fluorescent lamp for detecting an end-of-life state of a fluorescent lamp for making it possible to take suitable countermeasures. In the control apparatus, a load circuit is formed of a capacitor connected between filaments of a fluorescent lamp and a choke coil connected in series with the filament, and there are provided a detection coil for detecting a tube current flowing through the load circuit and a detection circuit receiving an output voltage of a rectifier circuit rectifying the output of the detection coil for detecting a rise in the output voltage occurring when the output frequency of an oscillation circuit is modulated by a modulation circuit.

Abstract: A powder type electroluminescent (EL) device comprises a step-up circuit for charging a capacitive EL element during a charge period, discharge transistor for discharging electric charge from the EL element during a discharge period, a voltage detector for detecting the predetermined voltage of the EL element to generate a charge-up signal, and a control section for starting the discharge period responsive to the charge-up signal. Even if the equivalent capacitance of the EL element decreases or the loss in the EL element increases with an enviromental condition, deterioration in luminous intensity does not arise. Accordingly, a longer life of the EL device can be obtained.

Abstract: A ballast includes an inverter for providing an AC voltage to a discharge lamp. As the lamp approaches end-of-life a DC voltage component develops across the lamp. The ballast includes circuitry for monitoring the condition of each of the cathodes by measuring this DC voltage component. After a predetermined increase in this DC voltage component, the inverter is disabled in order to prevent excessive heating of the cathodes.

Abstract: A decorative light string having a bulb shunt system is described. The light string includes a plurality of light bulbs positioned within their respective sockets along a power line and in a series circuit. The shunt system includes at least two shunt members associated with each bulb/socket combination wherein a first shunt is positioned within the bulb envelope while a second shunt is positioned outside of the envelope, either in association with the lamp holder or within the socket. The combined initial resistance of the two shunts is preferably greater than the resistance of the bulb filament and the system is configured to shunt the electric current passing through the bulbs in the event of filament breakage and, in one embodiment, in the event the bulb member is removed from its associated socket.

Abstract: A device for protecting a ballast circuit from excess voltage and excess current includes a switch for disconnecting the ballast circuit from the power source and a control circuit for operating this switch; the control circuit monitoring a control point, from which control point a first resistor connects to a first terminal of the power source, a second resistor connects to a second terminal of the power source, and a third resistor connects to a point between the switch and the ballast, the switch being brought into off-state when the voltage between the control point and the first terminal of the power source exceeds a given value, thus leading to a hysteresis between an input voltage for switching the device off and an input voltage for switching the device back on again, with positive feedback being provided by the third resistor for decreasing the switch-off time and the corresponding switching losses.

Abstract: A circuit that includes a latch and an oscillator is attached to a common lamp control switch to cause the lamp to flash when the switch is manipulated in accordance with a prescribed pattern. The flashing draws attention to the lamp and is used, for example, in an emergency. In a first embodiment, the circuit is placed in parallel with the switch. In a second embodiment, the circuit is placed in series with the switch. In both embodiments, the circuit is small enough to fit within an existing switch box.

Abstract: A power supply with an inverter capable of avoiding the inverter from producing excessive high voltage when a load is detached or the load impedance is greatly increased. The inverter is energized by a fixed DC voltage source and includes at least one switching element and an L-C resonant circuit. The switching element is driven to turn on and off and cooperative with the L-C resonant circuit to produce a high frequency AC voltage at an inverter output for driving a load. The inverter includes first and second clamping diodes connected in series across the DC voltage source in anti-parallel relation thereto with the first and second diodes defining therebetween a first connection point. Also included in the inverter is a pair of first and second impedance elements which are connected in series across the inverter output to provide a divided voltage indicative of an output voltage of the inverter with the first and second impedance elements defining therebetween a second connection point.

Abstract: An electronic circuit is provided to improve the performance of a conventional power supply for driving a He-Ne laser. In order to avoid an undershoot of the DC current due to operation of the feedback circuit at driving start of the laser, a feedback interrupting circuit is provided in the power supply which compares a detected voltage with a first reference voltage smaller than a predetermined voltage to produce a resultant voltage when the detected voltage is larger than the first reference voltage. The resultant voltage is charged at a charging circuit with a charging time constant to produce a charged voltage. The charged voltage is compared with a second reference voltage having a predetermined voltage level, and the feedback circuit is prevented from producing the control signal during the time interval when the charged voltage is smaller than the second reference voltage.

Abstract: In a fluorescent lamp ballast, a high-frequency AC voltage is applied directly across a tuned L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means prevents the series-resonating L-C circuit from overloading the source of AC voltage during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp, while at the same time removing the cathode voltage.

Abstract: A circuit and method for protecting a voltage inverter circuit is disclosed. The circuit comprises a first comparison circuit capable of comparing a first reference voltage to a voltage indicative of the load current of the voltage inverter. When the comparison circuit signals that the first reference voltage is greater than the load voltage, a disable circuit coupled to the first comparison circuit disables the voltage inverter. In the preferred embodiment, the inverter provides power to a cold cathode fluorescent lamp which, if damaged, can harm the inverter.

Abstract: A circuit for high-frequency operation of a discharge lamp. The circuit includes a load branch provided with terminals for connection to the discharge lamp and with an electrode heating transformer having a primary winding and secondary windings. Each secondary winding is shunted by a branch comprising an electrode of the discharge lamp. At least one switching element generates a high-frequency current through the load branch from a supply voltage. A control circuit generates a control signal for rendering the switching element conducting and non-conducting at a high frequency. A dimmer circuit is coupled to the control circuit for adjusting the frequency of the control signal. Each branch shunting a secondary winding of the transformer also includes an inductive element and a capacitive element and has a resonance frequency which is different from the resonance frequency of the load branch.

Abstract: A protection circuit for electronic ballasts which use charge pump power factor correction includes a switch with an overvoltage sensor, a resistor and a diode. In the event of a fault condition, the switch disables the charge pump power factor correction, while the resistor and diode prevent the switch dissipating unduly large amounts of energy.

Abstract: A circuit is disclosed to implement an energy saving electronic ballast (1A) for driving a fluorescent lamp or tube (2). The circuit is characterized by a high power factor, low harmonic distortion and minimized radio frequency interference. The circuit includes a unique DC power supply (4) comprising a high pass filter (8), which receives an AC input signal, a diode bridge rectifier (6) and a high speed diode rectifier (D2) which cooperates with the bridge rectifier to provide the power supply with first and second rectification stages. A current regulating capacitor (C4) for driving the fluorescent lamp or tube is connected to the DC power supply between the first and second rectification stages. A trigger and high frequency oscillator are provided after the second rectification stage of the power supply to provide the DC current necessary to operate the ballast circuit.

Abstract: The present invention describes a method and apparatus for a swept frequency switching gas discharge tube supply which produces a "crawling effect" in gas discharge tubes containing neon, argon or mercury gases or other gases and which has a means for eliminating the "bubble effect". To produce the "crawling effect", the driving frequency of the switching supply is swept from a higher frequency to a lower frequency thereby causing the excitation point to move from the electrodes on both ends of the dual electrode gas discharge tube to the center of the gas discharge tube. By varying the base switching frequency of the supply, the bubble effect which plagues some displays can be eliminated.

Abstract: A power source device includes a voltage converting means to input side of which a DC voltage source is connected and to output side of which a capacitance element and a load circuit are connected, while a control circuit is connected to the voltage converting means and the load circuit, the latter circuit having a load impedance made lower upon starting of a load in the load circuit than that in stable lighting of the load, wherein such control constant as oscillation frequency and duty are made to be substantially constant at the time of the starting and stable lighting of the load, and a switching means in the voltage converting means is turned OFF when the capacitance element has a voltage below a predetermined value.

Abstract: A power supply for high voltage, low current gas discharge tubes such as neon, argon, and mercury vapor. A free running, flyback oscillator, converts D.C. voltage energy into radio frequency energy by means of a compact, ferrite transformer and associated circuitry. The primary winding is tuned by a resonant capacitor and driven by a power transistor. A high voltage, centertapped winding of a ferrite transformer drives the gas tube load directly. A feedback winding arranged across the transistor base and emitter junction sustains oscillation and controls the drive level of the transistor by means of a regulating circuit which controls the amplitude of the current. Oscillator starting is achieved by means of an on-off switch which supplies a single starting pulse to the power transistor or by means of a time delayed starting pulse.

Abstract: An embodiment of the present invention is a lighting system including a sense transformer with two primaries and a secondary for receiving alternating current (AC) from a power source, a low ohmage resistor placed across the sense transformer secondary winding for preventing saturation of the core of the sense transformer, an analog comparator for detecting when ground-fault signals in the sense transformer secondary winding exceed a threshold voltage and digital counters for testing whether or not a ground-fault condition persists longer than three consecutive half-cycles of the received alternating current from the power source.

Abstract: The invention relates to a high-pressure discharge lamp (2) provided with a discharge vessel (3) with a ceramic wall (3a) and provided with a bimetal element (11) which rests against the discharge vessel wall in the cold state of the lamp, and which is removed from the discharge vessel wall during lamp operation. The discharge vessel is surrounded by an outer bulb (30) with intervening space (6), in which space a solid-state getter (15) is provided. According to the invention, the solid-state getter is provided on the bimetal element.

Abstract: A transformer has a primary winding connected in series with a direct current source, a solid state switch and a current sensing resistor. A reactive element is coupled to the primary winding to form a resonant circuit. A high voltage for exciting a gaseous discharge device is produced across a first secondary winding of the transformer. A second resistor couples a terminal of the direct current source to one plate of a storage capacitor that has another plate connected to a second terminal of the direct current source. The one plate of the storage capacitor also is connected to a second secondary winding of the transformer. The control circuitry for the power supply is biased by voltage stored across the capacitor.

Abstract: A circuit (100) for driving an instant-start fluorescent lamp (102) has an inverter (103, 132) and a series-resonant LC oscillator (146, 152). A capacitor (190) begins charging after power-up of the circuit and when its voltage reaches a certain level causes breakdown of a diac (192), which discharges the capacitor into an inverter transistor (132) to trigger operation of the inverter. Re-triggerring of the inverter is prevented by a diode (194) which subsequently discharges the capacitor cyclically, and by a capacitor (186) which enables a transistor (180) at a predetermined time following power-up. The occurrence of a subsequent fault condition causes a capacitor (210) to charge and to enable a transistor (196) which disables the inverter. Charging of the initiating capacitor (190) is prevented by an open circuit between terminal connectors (160, 162) if the lamp is not present.

Abstract: A circuit for starting and operating a discharge lamp, such as a compact fluorescent lamp, at high frequency from a 60 Hz AC supply. The circuit includes a DC power supply coupled to a pair of AC input terminals for generating a DC voltage. An oscillator coupled to the DC power supply includes a pair of semiconductor transistors and a drive transformer having a primary winding and at least one secondary winding. A load coupled to the output of the oscillator comprises a series combination of the primary winding of the drive transformer and a tank circuit including a tank inductor and a tank capacitor. Suitable means for connecting a discharge lamp in parallel with the tank capacitor is provided. An oscillator sensing and controlling circuit responsive to various lamp failure modes is coupled to the secondary winding of the transformer and reduces the output of the oscillator after a predetermined time delay by shunting the base of either one of the semiconductor switches of the oscillator.

Abstract: Apparatus for operating a discharge lamp comprising a high frequency circuit, sensing means for sensing the absence of an electrical connection between the circuit and the lamp and control means for receiving a non-connection signal and for sending a decrease control signal to the high frequency circuit for decreasing the high frequency power supplied to the lamp in response to the non-connection signal. The sensing means senses the absence of an electrical connection between the circuit terminal to which an electric potential is applied which is less than that applied to the other circuit terminal. By sensing the electrical non-connection between the circuit terminal having the lower potential, it is not necessary to sense the absence of a connection at the other end of the lamp.

Abstract: The present invention describes a method and apparatus for a high frequency switching gas discharge tube supply which suppresses or eliminates the "bubble effect" in gas discharge tubes containing neon or argon-mercury gas or other gases and which eliminates the migration of mercury or other migratory gases toward one electrode over time. To prevent mercury migration to one electrode over time within an argon-mercury gas discharge tube, a line frequency bias voltage is induced on the high frequency, high excitation voltage resulting in a gas discharge tube display which is uniform in intensity of light over the length of the tube.

Abstract: A protection circuit compatible with an electronic stabilizer of a discharge apparatus, for preventing damage to circuit elements due to an excessive voltage at the premature ignition of a discharge tube, comprises an intermittent switching circuit coupled to a thyristor for periodically turning on or off the thyristor. In the intermittent switching circuit, a first contact point of a relay switch is coupled to the cathode of the thyristor and a resistor, a condensor and a gate of a transistor are connected in parallel from a second contact point of the relay switch and a relay coil and a channel of said transistor are serially connected from the power source and a base of another transistor is coupled to a third contact point of the relay switch, said other transistor controlling the operation of a transistor which drives the discharge tube.

Abstract: A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Abstract: An inverter is powered by the pulsed DC voltage obtained by unfiltered full-wave rectification of the AC power line voltage provided from an ordinary electric utility power line. The output of the inverter is a 30 kHz squarewave voltage having an instantaneous absolute magnitude that is proportional to that of the AC power line voltage. By way of a step-down voltage transformer, the 30 kHz squarewave inverter output voltage is applied to the filament of a low voltage incandescent lamp.

Abstract: A circuit for starting and operating a discharge lamp, such as a compact fluorescent lamp, at high frequency from an 60 Hz AC supply. The circuit includes a DC power supply coupled to a pair of AC input terminals for generating a DC voltage. An oscillator coupled to the DC power supply includes a drive transformers having a primary winding. A load coupled to the output of the oscillator comprises a series combination of the primary winding of the drive transformer and a tank circuit including a tank inductor and a tank capacitor. Suitable means for connecting a discharge lamp in parallel with the tank capacitor is provided. A voltage sensing circuit responsive to failure of the lamp, is coupled to an oscillator controlling circuit which reduces the output of the oscillator after a predetermined time delay by shunting the drive transformer. Upon replacement of the failed lamp, normal operation of the oscillator is resumed without having to disconnect the AC supply.

Abstract: A video projection system having a liquid crystal panel with a video image, a projection lamp with ON/OFF control, a zoom lens with a zoom control mechanism, a focusing lens with a focusing control mechanism, an audio system with a volume control, a projection-lamp light detector, a heat sensor, a variable-speed cooling fan, a control module having a microprocessor and a digital-to-analog converter, a display, a keypad, an alarm/annunciator, a power supply with ON/OFF control, and an infrared based remote control system able to control power ON/OFF, zoom, focus, picture, and sound volume.

Abstract: A universal electronic ballast system (10) is provided for actuating at least one gas discharge lamp (1900) having any one of a plurality of predetermined wattage ratings. Electronic ballast system (10) includes a filter circuit coupled to an AC power mains (100, 110) for substantially suppressing spurious signals passing into or from the power source. The filter circuit is coupled to a regulated switching power supply circuit (14) which generates a regulated boost voltage and draws a substantially constant in phase sinusoidal load current from the power source supplied to a switching circuit (16) which generates a regulated pulsating current at a predetermined frequency. Responsive to the regulated pulsating current a high voltage is induced in the primary windings (1710 and 1680) of induction transformer (T3). The high voltage is coupled to gas discharge lamp (1900) by means of the magnetic coupling betwen primary winding (1730) and secondary winding (1765) of the output transformer (T2).

Abstract: An improved electronic ballast inverter for a gas discharge lamp includes an oscillator having at least two switching transistors for operating the gas discharge lamp at a high frequency during steady-state operation, a triggering circuit for initiating the operation of the oscillator, and an electrical circuit connected to the oscillator for gradually increasing the base current of at least one of the switching transistors immediately after start-up in order to delay the gas breakdown and thereby to produce preheating of the gas discharge lamp during startup.

Abstract: A 50 Hz or 60 Hz AC line voltage is rectified and converted to a DC voltage signal by a fluorescent lamp light ballast system. The DC voltage signal drives a pair of transistors to alternate between ON and OFF states, thereby producing a high frequency signal. A resonant circuit of the light ballast system converts the high frequency signal into a high amplitude, high frequency voltage signal needed to excite a fluorescent lamp load into operation. A protective circuit is employed to stop the generation of the high amplitude, high frequency voltage signal when the lamp load is in a burnout condition or when the lamp load is being replaced.

Abstract: The invention provides a brightness control circuit for a periodically flashing xenon lamp. The intensity of the flashing lamp may be selected in response to the selection of a reference voltage. The control circuit has a power source in series with a thristor for selectively controlling an application of a voltage from a power source to a xenon lamp. A capacitor is coupled substantially in parallel with the xenon lamp in order to apply a voltage across the lamp. A comparator is responsive jointly to a charge level on the capacitor and a reference voltage. The comparator switches on/off the thyristor so that the switching voltage may be selected by selecting the reference voltage, thereby selecting the intensity of the reference voltage. The flashing lamp in this particular application is part of an airport runway approach system.

Abstract: A lighting apparatus for a neon lamp includes a direct current power supply with a relatively low voltage output. The direct current power supply actuates a pulse oscillator to produce a narrow pulse voltage train output. The narrow pulse voltage train output is amplified and is supplemented by the signal output of a glow control cirucit to drive the neon lamp into operation. The signal output of the glow control cirucit can be a pulsating voltage signal or a constant voltage signal to correspondingly cause the neon lamp to blink or glow constantly.

Abstract: A high frequency PWM power supply for luminous tubes including a low power constant frequency, uniform pulse width generator which charges the intrinsic input capacitance of an insulated junction power FET thereby switching a source of DC voltage across the primary of a high voltage transformer. A current sense resistor and load current compensator discharge the FET gate capacitance upon attaining a predetermined average luminous tube load current. The secondary power supply output includes a series capacitance to minimize tube end discoloration particularly prevalent in mercury luminous tubes. A ground fault detector employing the intrinsic secondary capacitance and transformer core with a dual-peak detector thereby providing enhanced accuracy and ground fault reliability.

Abstract: An electronic ballast which will repeatedly try to ignite gas discharge lamps should they fail to ignite under conditions in which they should have ignited together with means rendering said electronic ballast incapable of trying to ignite said lamps after a predetermined period and said electronic ballast being rendered capable of again trying to ignite said lamps under prescribed conditions.

Abstract: A power supply for high voltage, low current gas discharge tubes such as neon, argon, and mercury vapor. A free running, flyback oscillator, converts D.C. voltage energy into radio frequency energy by means of a compact, ferrite transformer and associated circuitry. The primary winding is tuned by a resonant capacitor and driven by a power transistor. A high voltage, centertapped winding of a ferrite transformer drives the gas tube load directly. A feedback winding arranged across the transistor base and emitter junction sustains oscillation and controls the drive level of the transistor by means of a regulating circuit which controls the amplitude of the current. Oscillator starting is achieved by means of an on-off switch which supplies a single starting pulse to the power transitor or by means of a time delayed starting pulse.

Abstract: A main power supply device uses single phase, or three phase R, S, T; through rectification and filtration; each phase produces a different D.C. voltage so as to supply a respective voltage transforming device. The rectifier output of a step-down supply of the S, T, phase, in addition to supplying an astable square wave oscillator, so as to control signal outputs via a driving circuit, also supplies a tripping device, so as to control the high A.C. output from the high-voltage transformer of the transforming device. Any abnormal load can be detected by a detecting transformer and a protective circuit, so as to control cut-off of a transistor of a switching loop. A plurality of transforming devices are of the modular plate type; trouble-shooting can be performed easily, and the speed of maintenance is increased; the working safety is also enhanced.

Abstract: A power supply for high voltage, low current gas discharge tubes such as neon, argon, and mercury vapor. A free running, flyback oscillator, converts D.C. voltage energy into radio frequency energy by means of a compact, ferrite transformer and associated circuitry. The primary winding is tuned by a resonant capacitor and driven by a power transistor. A high voltage, centertapped winding of a ferrite transformer drives the gas tube load directly. A feedback winding arranged across the transistor base and emitter junction sustains oscillation and controls the drive level of the transistor by means of a regulating circuit which controls the amplitude of the current. Oscillator starting is achieved by means of an on-off switch which supplies a single starting pulse to the power transistor or by means of a time delayed starting pulse.

Abstract: In this invention, pulse generating means is adapted to emit a high-frequency pulse signal of a fixed duty ratio and a discharge tube is lighted by means of this pulse signal. The frequency of the pusle emitted by the pulse generating means is adjustable by adjusting means. Thus, one discharge tube lighting device of this invention can be used interchangeably for lighting discharge tubes varying in capacity. The lighting device is further capable of effecting adjustment of light in a wide range. Further, sequential potential forming means is adapted to allow a plurality of discharge tubes to be sequentially lighted with intervals. When a plurality of discharge tubes are to be lighted, therefore, the rectifying means necessary for the lighting is allowed to have only a small capacity. The high-voltage applying means for applying high voltage to the discharge tubes are connected to the electrodes disposed at the opposite terminals of the discharge tubes with connecting wires joined one each to the electrodes.

Abstract: A switched bridge circuit has semiconductor bridge elements (T1,T2) which are arranged to provide a commutated output from a d.c. source (+300V). The commutation is effected by a switching signal from a control circuit. The control circuit for switching the bridge elements is coupled with the output by a capacitor (C2) such that switching of the bridge elements is prevented while there is a flow of current through the capacitor, the current through the capacitor is indicative of a changing output voltage and a confirmation that the voltage across the bridge elements is not approximately zero or +300V.

Abstract: A driver for a electroluminous lamp includes a bridge switching circuit comprising four MOSFETS, the lamp and a series connected inductance being connected as the load on the bridge circuit. The switching of the transistors of the bridge circuit is controlled by logic circuitry which generates a two-phase, non-overlapping gating control signal which causes the MOSFETS to be switched in pairs whereby current will flow in alternate directions through the lamp.

Abstract: A power supply for high voltage, low current gas discharge tubes such as neon, argon, and mercury vapor. Free running, flyback oscillator, converts D.C. voltage energy into radio frequency energy by means of a compact, ferrite transformer and associated circuitry. The primary winding is tuned by a resonant capacitor and driven by a power transistor. A high voltage, centertapped winding of a ferrite transformer drives the gas tube load directly. A feedback winding arranged across the transistor base and emitter junction sustains oscillation and controls the drive level of the transistor by means of a regulating circuit which controls the amplitude of the current. Oscillator starting is achieved by means of an on-off switch which supplies a single starting pulse to the power transistor or by means of a time delayed starting pulse.

Abstract: A protective circuit for a fluorescent lamp includes a stabilizer circuit for preventing breakdown of the lamp as it becomes worn. Known stabilizers are high speed switching circuits which can break down and become unstable in certain conditions to cause an on-off cycling of the lamp. This is prevented by a protective circuit, according to the present invention, which incorporates a thyristor connected to a blocking transistor. A sensing element triggers the thyristor in response to an abnormal voltage or in response to an overheated condition. The thyristor then activates a transistor to open the lamp control circuit and to prevent its reclosing, thereby holding the lamp off.

Abstract: An inverter is powered by a magnitude-modulated DC supply voltage derived by rectification from an ordinary 120Volt/60Hz electric utility power line. The inverter powers a low voltage (12 Volt) incandescent lamp with a magnitude-modulated high frequency (30 kHz) voltage. The magnitude modulation on the high frequency voltage is proportional to the magnitude modulation on the DC supply voltage.

Abstract: A disabling circuit for deactivating a high pressure sodium lamp starting and operating circuit when the lamp exhibits end-of-life cycling includes a normally closed thermal switch connected to the starting and operating circuit is inoperative, the switch having contacts which open in response to an elevated temperature. A heating element is connected in parallel with the lamp so that the voltage across the lamp is applied to the heating element. The heating element is supported in a selected heat conducting relationship with the thermal switch so that a predetermined elevated temperature is reached and the contacts are opened only after the dissipation of an amount of energy resulting from repeatedly high lamp open-circuit voltage accompanying end-of-life cycling.

Abstract: The invention relates to an electronic converter for supplying a constant amplitude output voltage while taking from the main supply only a sinusoidal current in phase with the voltage. This device is constituted by an auto-oscillator comprising transistors 7a and 7b for which the duty cycle is automatically regulated, a first inductance 10 constituting an oscillator circuit to which the output energy is evacuated, and second inductance taking off part of the high frequency energy produced to reapply it, after rectification, in series with the mains voltage rectified by the bridge 13, so that the voltage between the common polarized terminals of the auto-oscillator becomes continuous and held at a potential at least equal to the peak mains voltage, which translates into a continuous output voltage envelope. This device is applicable to the production of electronic transformers, power supplies, electronic ballasts, etc., without necessarily requiring electrolytic smoothing capacitors.

Abstract: A control circuit for fluorescent lamps having gas filled tubes and a pair of discharge electrodes in the tubes includes a transformer, a gated switching device and a control signal generating circuit. The transformer has a secondary winding connected with the lamp discharge electrodes and a primary winding to which power is applied by the switching device when a gating signal is applied to its gating terminal. The control signal generating circuit normally controls the gating of the switching device by alternatingly applying, and then ceasing to apply, a control signal to the gating terminal. The control circuit is capable of continuing a current between the discharge electrodes once the lamp is conducting. The control circuit is further capable of "starting" a lamp by applying a high voltage to the discharge electrodes. The high voltage is generated when the gated switching device is not applying power to the primary winding.