Abstract: An amplifying-gate thyristor having an increased integrated circuit includes a main thyristor and an amplifying thyristor. The amplifying thyristor is of the gate turnoff-type. The main thyristor and the amplifying thyristor are such that the amplifying thyristor remains in the conductive state while the main thyristor is conductive. A control circuit turns off the amplifying thyristor when the current through the main thyristor is approximately its hold current.

Abstract: A diagnostic circuit monitors filament currents in hot cathode fluorescent lamps for detecting when the filament erodes to the point of breaking. When such a filament failure is detected, information is processed and a request is sent to replace the lamp before it actually fails. The diagnostic circuit is low power and low voltage and is electrically isolated from the high-voltage end of the lamp. Additionally, a simple circuit to regulate rms value of filament voltage without having to compute or otherwise measure the actual rms value is provided.

Abstract: An electronic ballast for a fluorescent lamp includes a delay triggered circuit which, upon expiration of a predetermined period during which the lamp filaments, constituting opposite electrodes of the lamp, are preheated, applies high frequency operating voltage across the opposite electrodes of the lamp beginning with a transition from a condition of no voltage to a condition of full rated voltage which occurs within one cycle of the high frequency voltage. The sharp transition from zero "glow current" to full "arc current" at the end of the preheating period has been found to increase the life of lamps in the number of on-off starts, particularly with respect to lamps of poor quality. The rapid transition is possible because the ballast uses the same inverter and transformer for supplying preheating and operating voltages. The operating voltage is applied between the opposite electrodes of the lamp via an electronic bi-directional switch, controlled by a preheating delay RC timing circuit.

Abstract: A circuit arrangement used with electronic ballast equipment has an inverter which supplies a high-frequency half-bridge voltage to at least one load circuit having a lamp throttle, a fluorescent lamp, an ignition capacitor, and a half-bridge capacitor. In order to pre-heat the coils of the fluorescent lamp in a short period of time, a switchable voltage source is activated. This voltage source is connected to the output of the inverter. The outputs of the voltage source are constructed as a pair, to which the electrodes and the fluorescent lamp are connected in parallel. This voltage source includes a transformer having a primary winding coupled to the inverter and is switched between non-conducting and conducting (energized) states by a switching stage. The secondary windings of the transformer are connected in parallel to the electrodes of the fluorescent lamp.

Abstract: A circuit arrangement for operating a discharge lamp comprising input terminals for connection to a supply voltage source. A load branch B has terminals for holding the discharge lamp and includes an inductive ballast. A device I is coupled to ends of the load branch and to the input terminals to generate a high-frequency voltage from the supply voltage furnished by the supply voltage source. A device II is coupled to the device I to adjust the power consumed by the discharge lamp, the frequency of the high-frequency voltage being dependent upon the adjusted value of the power consumption. A transformer having a primary winding and secondary windings with each secondary winding shunted by an electrode branch during lamp operation, which electrode branch includes an electrode of the discharge lamp. The primary winding forms part of a branch C which also includes a frequency-dependent impedance and which shunts the load branch.

Abstract: Start and operation of high pressure discharge lamps, in which a high-frequency starting voltage U.sub.HF and an operating voltage U.sub.B are furnished to the lamp electrodes includes the steps of: 1) turning on the high-frequency starting voltage U.sub.HF at a starting time t.sub.0 to ionize the lamp filling and preheat the electrodes; 2) turning on the operating voltage U.sub.B after a preheating interval .DELTA.t.sub.H, that is, at time t.sub.1 =t.sub.0 +.DELTA.t.sub.H ; and 3) turning off the starting voltage U.sub.HF at time t.sub.2 .gtoreq.t.sub.1, as a result of which the lamp is then operated solely by means of the operating voltage U.sub.B. As a result, the transfer phase for the development of the arc is shortened. Advantageously, the frequency of the starting voltage is selected such that the product of the frequency f of the starting voltage U.sub.HF and the spacing d between the electrodes meets the condition f.multidot.d.gtoreq.50 kHz.multidot.cm.

Abstract: The invention is directed to a method for controlling the emission current of an electron source and to a correspondingly controlled electron source. For this purpose, a parallel circuit comprising resistors 6 and field-effect transistors 7 is connected in the high-voltage circuit between the cathode 1 and the control electrode 2. The supply voltage for the field-effect transistors 7 is generated by voltage dividing the voltage across the resistors 6. The measurement of the emission current takes place at low-voltage potential and a control signal obtained from the measuring signal is optically transmitted via a light-conducting fiber or a light waveguide to the control circuit in the high-voltage part. The emission current control at high-voltage potential is provided without additional voltage supplies. Additional insulating transformers are therefore not required.

Abstract: A method and apparatus for driving a fluorescent lamp is described wherein the fluorescent lamp is operated in the phanotronic, or hot-cathode, mode. The filament preheat current is decoupled from the arc current through synchronization of the filament voltage and arc voltage waveforms to provide sense windows during which the filament condition may be precisely and accurately determined. Sensing circuits provide correctional feedback to the filament voltage signal to provide optimal filament heating.

Abstract: The present invention discloses a control module that provides improved control over the ignition of a fluorescent lamp. In one aspect, the control module determines whether the lamp is lit and, when the lamp is not lit, determines whether the power supply line voltage is insufficient to sustain the lamp in a lit state after ignition. When the power supply line voltage is determined to be insufficient, the control module waits until the power supply line voltage rises to a sufficient level before igniting the lamp.

Abstract: A fluorescent lamp lighting circuit is disclosed in which an instant lighting is possible, and a high reliability is ensured. Further, the circuit is compact, and the cost is low. The fluorescent lamp lighting circuit according to the present invention includes a discharge circuit section including a choke coil serially connected to a filament of a fluorescent lamp. It further includes a lighting circuit section connected serially to the filament and the choke coil so as to be turned on at certain intervals by supplying the power, and so as to be turned off after the starting of the glow discharge of the fluorescent lamp. It further includes a protecting circuit section for turning off the light circuit section after certain repetition of on/off operations of the lighting circuit section.

Abstract: A feedback control system of ballast which has function to detect the number of lamp and is applied to an integrated circuit to control the ballast for a fluorescent lamp etc, and provides the ballast with the feedback control system which can detect the number of lamp, control ballast continuously by means of the n-lamp detector and soft start controller which produce the compensated current from the feedback current and direct link voltage. Therefore, the feedback control system can control the ballast accurately according to the load change such as the change of input voltage, number of lamp.

Abstract: A low-pressure mercury discharge lamp with a lamp vessel having a first lamp vessel portion (La1) with a first electrode (E11) and a first luminescent layer which radiates white light of a first color temperature during lamp operation and a second lamp vessel portion (La2) with a second electrode (E12) and with a second luminescent layer which radiates white light of a second colour temperature different from the first during lamp operation. The first lamp vessel portion and the second lamp vessel portion are interconnected by a connection which allows a filling of mercury and a rare gas in both portions to pass and together enclose a discharge space. The discharge space contains only one further electrode (E13) for both the first and second lamp vessel portions.

Abstract: There is provided a ballast for at least one gas discharge lamp havingan inverter which has two switches (S1, S2) in series, connected to a d.c. voltage source and switched with complementary timings, and a load circuit connected in parallel with one of the two switches (S1, S2) which load circuit includes a series resonant circuit (L1, C1) and the lamp (LA). Additionally there is provided a heating circuit (T, S3,R1) for current supply of the lamp coils, likewise connected to the inverter, which heating circuit includes a further periodically switchable switch (S3) for control of the heating current, whereby the heating circuit is likewise connected in parallel to one of the two switches of the inverter.

Abstract: The present invention is to provide a gas discharge tube which is properly lighted to improve the reproducibility of a satisfactory light emission state. The gas discharge tube includes an envelop for accommodating a hot cathode for emitting thermoelectrons, an anode for receiving the thermoelectrons, a focusing electrode having a focusing opening for converging paths of the thermoelectrons, and a discharge shielding member supporting the focusing electrode and the anode, the discharge shielding member further supporting a cathode box for surrounding the hot cathode while being electrically insulated from the focusing electrode. Since a lighting device for the gas discharge tube sets the focusing electrode to a zero or negative potential while an electric field is generated between the hot cathode and the anode, the lighting device will be certainly turned on.

Abstract: A ballast arrangement is disclosed for use in powering fluorescent and other gas discharge lamps. The ballast arrangement controls the arc voltage provide by an arc voltage oscillator independent of the filament voltage provided by a filament voltage oscillator. In this manner, safe maintenance condition during fault and interrupt condition are obtained. The full arc voltage is only applied to the lamp when the lamp filaments are warm or after a time period during which they are warmed. The filament pre-warming time reduces sputtering when an excitation or arc voltage in subsequently applied to induce lamp arcing.

Abstract: A DC power supply 44 for providing a desired filament voltage to a static filament in a vacuum fluorescent display 16 includes a voltage regulator 46 with an input and an output. The input couples to a source of ignition voltage 10 while the output couples to the base of a transistor 50. A first dropping resistor 52 connects between the source of ignition voltage 10 and the collector of the transistor 50. A second dropping resistor 54 connects between the emitter of the transistor 50 and the filament 20 of the VF display 16. Accordingly, a first current path to the filament 20 is defined through the first dropping resistor 52, the collector-emitter junction of the transistor 50, and the second dropping resistor 54. A second current path to the filament 20 is defined through the voltage regulator 46, the base-emitter junction of the transistor 50, and the second dropping resistor 54.

Abstract: Disclosed is a power-level selection circuit in combination with a lamp circuit including a fluorescent lamp having first and second cathodes with resistive-heating filaments each spaced at a respective end of a lamp tube; first and second power leads for respectively connecting the cathodes to an a.c. power source whose power can be selectively enabled and interrupted by a main power switch; and a ballast inductor in serial circuit with one of the power leads and including a plurality of filament-heating windings for supplying power to the cathodes. The power-level selection circuit is interposed between a first cathode and a filament-heating winding, and includes a power-receiving circuit coupled to the filament-heating winding to receive power therefrom. Further included is a filament-supply circuit for continuously supplying available power to the first cathode.

Abstract: To operate one or more serially connected low-pressure discharge lamps, tcally fluorescent lamps, a preheating circuit is provided to preheat the electrodes of the lamps (E1, E2, E3, E4), which changes from low-impedance to high-impedance state after the lamps have been preheated by controlling a semiconductor switch (Q3) in the heating circuit. In accordance with the invention, to eliminate reliance on the resistances of the lamp filaments themselves, which are subject to variation from lamp-to-lamp due to manufacturing tolerances, and later on, to changes due to aging of the lamp, and to provide for reliable switching of the semiconductor switch, a sensing impedance element (Z), which may be an ohmic resistor or a capacitor (Z', Z"), is serially connected to the switching path of the semiconductor switch (Q3) which, typically, is a field effect transistor (FET).

Abstract: To control preheating current flow through a fluorescent lamp supplied from high-frequency inverter (T1, T2, A) and a series resonance circuit, an electronic switching control circuit (SC) is connected to the preheating circuit of at least one electrode filament (E1, E2, E10, E20, E11, E21, E12, E22) of one or more of the fluorescent lamps. The switching control circuit senses the voltage across the pair of terminals (T1, T1', T2, T2') of the electrode filaments, or across all the electrode filaments. Since fluorescent lamp filaments have a positive temperature coefficient of resistance, the voltage across the filaments will rise as the filament or filaments of the lamp reach electron emission temperature. This rise in voltage is sensed, for example, by a threshold circuit which may include a Zener diode, and is used to break the preheating circuit.

Abstract: A metal halide lamp is employed, as a light source, in an optical device such as, for example, an illuminator or an image display. The optical device includes a discharge tube filled with mercury, at least one rare gas, and at least one metal halide, and a pair of electrodes spaced from each other and enclosed in the discharge tube. The optical device also includes an electric circuit, electrically connected to the pair of electrodes, for starting the discharge tube by applying thereto a higher voltage than a voltage to be applied at a steady state to thereby cause an arc discharge in the discharge tube. When the lamp is turned off, power supply thereto from the electric circuit is temporarily interrupted, and when the lamp cools after a first time interval has elapsed subsequent to the interruption of the power supply, a starting voltage is applied to the lamp via the pair of electrodes for a second time interval to cause redischarge.

Abstract: A power supply for a magnetron varies a power output level and prevents moding of the magnetron. To provide a variable power output, a microprocessor senses an anode current and voltage of the magnetron. Based on the sensed signals, the microprocessor adjusts the conduction angle of a thyristor to obtain the desired power level. The microprocessor also monitors the anode voltage for detecting moding of the magnetron. If moding is detected, the microprocessor adjusts the conduction angle of another thyristor to change the current supplied to the filament. By changing the filament current, the microprocessor effectively prevents the moding of the magnetron.

Abstract: For triggering a discharge lamp powered by a d.c. source and having electrodes disposed in the lamp bulb, a power supply circuit is proposed having a triggering device where, after the start of heating of a cathode (which cathode is in the form of a heated cathode), the triggering device switches a triggering pulse to a discharge path of the lamp, which discharge path is formed by the two electrodes, and initiates a triggering phase, such that the triggering pulse at least partly overlaps in time with the heating phase of the cathode. In this way, reliable triggering of deuterium discharge lamps and hydrogen discharge lamps is possible, particularly in the case of a deuterium lamp having a relatively small opening, e.g. on the order of 0.3 mm.

Abstract: A lamp protective, electronic ballast includes a lamp voltage detector having a capacitor and resistor series connected across a discharge lamp. The junction of the resistor and capacitor is coupled to a voltage sensitive switch for detecting DC offset on the lamp and excessive AC voltage on the lamp. The switch is more sensitive to DC offset than to excessive AC voltage and is disabled while the lamp is started.

Abstract: An electrical arrangement is disclosed comprising a circuit to supply current to a discharge lamp. The circuit comprises a lower voltage source of alternating current in the form of a square wave generator. The current is fed to two transformers, the primary windings of which are connected in series, the transformers being physically located immediately adjacent the electrodes of a discharge tube. The secondaries of the transformers are also connected in series, and are connected to the electrodes of the discharge lamp. Only extremely short high-tension leads are provided extended between the secondaries of the transformer and the electrodes. Each transformer is a transformer having a coupling factor in excess of 0.

Abstract: A fluorescent lamp starter circuit includes a relay which forms a first circuit loop to detect the input voltage and to switch the relay from the normally-closed position to the normally-open position once the input voltage reaches the threshold level. The switching of the relay to the normally-open position opens the first circuit loop and closes a second circuit loop constituted partly by the relay to allow current to flow through and heat up the electrodes of the fluorescent lamp. After a certain time period, the relay, which is controlled by the discharging of a capacitor, is switched back to the normally-closed position to open the second circuit loop. The electrodes of the fluorescent lamp, after having been heated, begins to emit electrons and this lowers down the impedance that it represents so that the voltage across the first circuit loop is not sufficient to actuate the relay so as to maintain the relay at the normally-closed position.

Abstract: A circuit arrangement for preheating electrodes of a discharge lamp connected in series with a ballast by means of a supply voltage of alternating polarity. The circuit arrangement is provided with a switching element (S) which shunts the lamp and which is operated by means of a control signal. A circuit portion (II) adjusts both the phase and the frequency of the control signal in dependence on whether the ballast is inductive or capacitive. The electrodes of the lamp are preheated in a short period both for an inductive ballast and for a capacitive ballast.

Abstract: An energy efficient and cost effective electronic ballast circuit which lights a fluorescent tube but which avoids excessive voltages or pulsing of the tube. The starter circuit preheats the filaments for a time sufficient to ensure quick ignition upon application of an appropriate voltage, then ceases the flow of current after the tube is lighted to avoid wasting energy.

Abstract: The present invention relates to a gas discharge lamp lighting system in which a voltage source is provided for supplying an a.c. voltage across the lamp electrodes and, further, a source of stored d.c. voltage which is gated to the electrodes in synchronism with and additive to the a.c. voltage, in order to provide a resultant voltage across the electrodes of a magnitude sufficient to light the lamp.

Abstract: A series-resonant ballast for powering at least one gas discharge lamp (16) having heatable filaments (12,15) includes: DC voltage input terminals (B+,B-); an oscillating resonant converter (55,26,51,52,53) for producing high frequency voltage for application to the gas discharge lamp; a control circuit (58) able to receive a control signal from the DC input terminals and from the resonant converter and operable to initiate and stop the oscillations; and direct current blocking circuits (57,50) coupled across the filaments (12,15) and operable to stop flow of the control signal from the DC input terminals, thereby the ballast will not oscillate and will not draw any power from the DC input terminals, whenever the gas discharge lamp is: (i) removed from the output terminals, (ii) is defective, or (iv) is inoperative.

Abstract: An electrical arrangement is disclosed comprising a circuit to supply current to a discharge lamp. The circuit comprises a lower voltage source of alternating current in the form of a square wave generator. The current is fed to two transformers, the primary windings of which are connected in series, the transformers being physically located immediately adjacent the electrodes of a discharge tube. The secondaries of the transformers are also connected in series, and are connected to the electrodes of the discharge lamp. Only extremely short high-tension leads are provided extended between the secondaries of the transformer and the electrodes. Each transformer is a transformer having a coupling factor in excess of 0.

Abstract: A low component count and lightweight ballast usable with fluorescent lamp loads of widely different wattage has first and second inductors and first and second capacitors connected in a bridge circuit and can provide current regulation within a few percent for lamp loads between 14 Watt and at least 40 Watt. The two inductors can be wound on a single toroidal core for maximum compactness.

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 circuit for lighting a fluorescent lamp. The present invention takes into account the fastidious characteristics of the fluorescent lamp, and during the momentary lighting of the fluorescent lamp. In order to reduce the temperature fluctuations, a separate pre-heating power is supplied. The circuit includes: a first resonance circuit consisting of a first capacitor connected to the opposite ends of the fluorescent lamp, a resonance inductor, a second capacitor, a first switch and a DC power source, serially connected; a second resonance circuit consisting of a second switch, a first capacitor, a resonance inductor, a third capacitor and a DC power source, serially connected; a switch control circuit for activating the first and second switches in an alternate manner. Before the lighting of the fluorescent lamp, the first and second resonance circuits are put to a resonance state, while, after the lighting of the fluorescent lamp, the resonance is eliminated.

Abstract: A regulated current source is used to drive the cathodes of a hot cathode gas discharge lamp. In one embodiment, the regulated current source is time shared between the lamp cathodes and the lamp arc.

Abstract: An electron emission device is provided in which a drive current for driving an electron emission element is maintained at a constant level. The device comprises a transistor having its base provided with a divided voltage. The electron emission element is responsive to the transistor.

Abstract: A high-frequency electronic ballast for fluorescent lamps has a first inverter for controllably providing heating power to the lamp cathodes and a second inverter for controllably providing main lamp operating power. The two inverters are separately and independently controllable, thereby: i) to permit adjustment of lamp current so as to provide full or reduced light output in accordance with requirements, ii) to permit cathode heating power to be removed under conditions of providing full light output, thereby to maximize efficiency, and iii) to permit cathode heating power to be restored under conditions of reduced light output, thereby to prevent premature lamp failure.

Abstract: A circuit arrangement for the operation of a fluorescent lamp which is connectable to an alternating-current power supply, for example, the elctrical power supply on board an aircraft, including a switch which is located between the lamp electrodes, and which is actuatable through the intermediary of a control circuit whereby the lamp electrodes are heated when the switch is closed. A measuring element which is connected to the input of the control circuit determines the decreasing voltage at least at one of the lamp electrodes, and the control circuit will open the switch for the ignition of the fluorescent lamp only when the determined voltage is essentially constant, or has reached a threshold value.

Abstract: An electric circuit for glow discharge lamp which regulates lamp output according to changing environmental conditions includes a power lamp circuit electrically connected between an anode lead-in wire and a cathode to create a lamp voltage, a filament power circuit electrically connected to a pair of cathode lamp filament lead-in wires to create a filament voltage whereby said lamp voltage decreases with an increasing filament voltage due to lamp characteristics, and a sensing and control circuit for adjusting the filament voltage in accordance with changing environmental conditions for maintaining lamp voltage at a predetermined constant value.

Abstract: An electric circuit for glow discharge lamp includes a sensing and control circuit which senses the minimum of the lamp voltage wave form and adjust the filament voltage in accordance with sensed wave form and changing environmental conditions for maintaining lamp voltage at a predetermined constant value.

Abstract: A filament switch for a rapid start fluorescent lamp disconnects or reduces through phase modulation the heating current to a plurality of lamp filaments to save power. The switch uses a trigger in series with a voltage sensitive element and an impedance element, the switch being responsive to the difference between a lamp starting voltage and a lamp sustaining voltage for determining when and for how long the filaments are heated.

Abstract: A lighting device for a hot cathode fluorescent lamp used for a back light of a liquid crystal display or the like attempts to prolong the life of a lamp in a lighting device for a low consumption wattage fluorescent lamp. More specifically, the hot cathode fluorescent lamp is started while being pre-heated, and even after starting, a pre-heat current keeps flowing. The pre-heat current value after starting is set to be smaller than that at the time of starting for the purpose of optimizing the hot spot temperature. With employment of the configuration as described above, the lifetime of the hot cathode fluorescent lamp when used as a back light can extend to 10,000 hours or more.

Abstract: A CRT display system is described wherein a measure of the beam current generated within the CRT is derived and the voltage across the cathode heater modified as a function of this measure. In this way the optimum voltage across the heater coils is maintained, thus preventing "cathode stripping" at times of peak beam currents, and optimizing the CRT's working lifetime.

Abstract: To decrease the losses in the starting circuit for a compact fluorescent p, a positive temperature coefficient (PTC) resistor (KL) is connected in a resonance circuit of the lamp and also connected to the power supply of the lamp through a diode, polarized in blocking direction with respect to direct current, so that, before the lamp fires, a-c provided from an inverter (INV) can pre-heat the electrodes (E1, E2) of the lamp (LP), which will also cause current flow through the PTC resistor (KL); upon heating of the PTC resistor, this d-c current decreases and the voltage across the electrodes of the lamp will rise. When the lamp fires, it will drop below the supply voltage of the operating circuit for the lamp, thus causing the removal of the PTC resistor from the current carrying circuit, thereby eliminating energy loss through that resistor, and heating of the operating circuit assembly.

Abstract: A three pole relay is shown which operates in response to the flow of normal operating current across fluorescent lamps to energize a coil which actuates a relay to open switches disposed in all of the filament lines associated with the lamp to shut off filament current while maintaining current flow across the lamps themselves.

Abstract: A gas discharge tube comprises an indirectly heated cathode structure including a hot cathode into which a heater is incorporated. During discharging, the heater is supplied with a discharge current so as to generate Joule heat which is used as a heat source for the hot cathode. To this end, in a drive circuit in which the heater is preheated with a heater power source to initiate the discharging and to light up the discharge tube, followed by supply of discharging power from a discharging maintaining power source, a preheating switch is inserted between the heater and heater power source, and is opened at a start of the discharging and kept opened thereafter.

Abstract: To prevent long-time current flow through a positive temperature coeffici resistor (KL) included in the heater circuit of one or more fluorescent lamps (LP, LP1, LP2), a relay is connected in circuit with the PTC resistor (KL), which will respond when the voltage across the capacitor (C4) reaches the level of d-c voltage derived from a relay rectifier (GL) and coupled to the PTC resistor itself. The relay operates a switch contact (S) which interrupts the current flow through the PTC resistor; the flow through the relay is small in comparison with the current flow through the PTC resistor, thereby saving energy and decrease in the heat loading on the circuit structure.

Abstract: A rapid start fluorescent system which has its starting capacitance connected to a tap on the secondary of the ballast transformer which tap is located at a predetermined number of turns of the secondary.

Abstract: A three pole relay is shown which operates in response to the flow of normal operating current across fluorescent lamps to energizes a coil which actuates a relay to open switches disposed in all of the filament lines associated with the lamp to shut off filament current while maintaining current flow across the lamps themselves.

Abstract: An apparatus is provided for driving a discharge lamp, the discharge lamp having first and second electrodes, each of the first and second electrodes having first and second terminals. The apparatus includes a switching circuit coupled to the first terminals of the first and second electrodes of the discharge lamp for supplying a high frequency signal to the discharge lamp for igniting the discharge lamp. A starting circuit is provided connected to the second terminals of the first and second electrodes of the discharge lamp and including an inductor and capacitor connected in parallel across the discharge lamp. Alternately, a thermister is provided between parallel connected conductor and capacitor and one of the second terminals of the first electrode of the discharge lamp. Furthermore, circuitry is provided which is connected between the switching circuit and the thermister for deactivating the switching circuit when the thermister is heated to a specified temperature.

Abstract: A full-bridge inverter ballast for a fluorescent lamp comprises two pairs of switching transistors and is conditionally operable to self-oscillate in either of two modes: a first mode wherein one of the two pairs of switching transistors self-oscillates in manner of a half-bridge inverter and powers the thermionic cathodes of the fluorescent lamp, and a second mode wherein both pairs of transistors self-oscillate in manner of a full-bridge inverter and then powers the main gas discharge of the fluorescent lamp. The first mode gets initiated immediately upon applying power to the ballast, but the second mode does not get initiated until about 1.5 seconds after the initiation of the first mode. The way, the cathodes will have become fully thermionic prior to applying main power to the fluorescent lamp.