Abstract: In a microwave oven, a magnetron is powered by way of a self-oscillating flyback converter circuit, which operates at a conversion frequency controllable over a range of frequencies up to about 35 kHz. The converter circuit is powered from a DC voltage derived from full-wave-rectification and filtering of ordinary 120 Volt/60 Hz power line voltage. The output of the converter is applied to the magnetron by way of a flyback transformer.In one preferred configuration, the output fromthe flyback transformer is applied dirrectly to the magnetron--without the use of an intermediary rectifier. As a result, current to the magnetron is provided inthe form of triangularly-shaped pulses with a duty-cycle of about 60% and with a crest-factor of less than 3.5.In a second preferred configuration, the output from the flyback transformer is rectified and filtered by a capacitor-inductor combination, with the result of providing a nearly constant-magnitude current to the magnetron.

Abstract: An electronic ballast for tungsten lamp tubes is operable even when one of the tungsten lamp filaments is broken or missing. The transformer negative feedback oscillator which drives the tungsten filaments includes parallel connection to one of the filaments through a resistor of one of the filaments and parallel connection to the other filament through a tuning circuit to make the circuit operable when one of the filaments is broken or missing. The tuning circuit, in addition to providing a closed circuit when one of the tungsten filaments is missing, also enables the intensity of the light to be adjusted.

Abstract: A plug-in starting aid for generating high voltage pulses in the ballast circuit of high intensity discharge lamp comprises interconnected electrical components mounted in a frame of insulating material. The frame has three terminals projecting out one side and engageable in the cooperating terminals of a connector block in which the starting in may be plugged in. The terminals are also engageable by standard mating wire terminals when the starting aid is used without a connector block.

Abstract: An improved ballast circuit for fluorescent lamps includes an electronic bilateral triggering device and a capacitor connected in series combination across the secondary winding output terminals of a ballasting transformer and in shunt with the fluorescent lamps. The triggering device and the capacitor operate to produce high frequency oscillations superimposed on the high AC voltage applied across the lamp cathodes to improve the capacitive coupling between the lamps and their mounting fixture during starting. The triggering device becomes nonconductive to effectively remove itself and the capacitor from the starting circuit while the lamps are lit.

Abstract: An apparatus for energizing a fluorescent lamp having two filament electrodes. The apparatus comprises a rectifier circuit responsive to an AC voltage for providing DC voltage and a transformer having at least a primary winding and a secondary winding for providing transformed power to said lamp. A switch intermittently connects said DC voltage to said primary winding to develop current pulses at an ultrasonic frequency. Said secondary winding is coupled to said filament electrodes to both heat said filament electrodes and establish a potential thereacross for initiating and maintaining an arc therebetween.

Abstract: A hybrid ballast apparatus for starting and operating a plurality of series-connected discharge lamps and which provides protection against electric shock. The ballast apparatus includes first and second bidirectional thyristors connected in parallel with first and second ones of said lamps, respectively, and a trigger control circuit for simultaneously triggering the thyristors into conduction. Each lamp has two filaments and means are provided for connecting an L-C ballast device, the lamp filaments and the first and second thyristors in a series circuit across the AC supply voltage terminals. If one end of a lamp is removed from its socket, the series circuit is opened so that the maximum voltage at any lamp electrodes is limited to the AC supply voltage.

Abstract: A high-intensity discharge (HID) metal vapor lamp and starting apparatus includes a metal vapor lamp having an outer envelope containing a gas filled arc tube, the fill gas including xenon, the arc tube having a pair of spaced electrodes with a starting aid surrounding the arc tube intermediate the electrodes, a non-linear dielectric element shunting the spaced electrodes and a ballast means and an electrical conductor coupling the spaced electrodes to a base member connected to a low voltage source whereby starting of the metal vapor lamp from a low voltage source is effected.

Abstract: A ballast-inverter circuit for a discharge lamp with preheatable electrodes. The lamp is connected to the supply voltage input terminals via a ballast impedance. A triac provides a preheat current path for the lamp electrodes and has a gate electrode connected to an RC timing circuit. A PTC resistor is coupled between one input terminal and the timing circuit to trigger the triac so as to heat up the lamp electrodes and assist the lamp to ignite. The PTC resistor heats up until its resistance is so high that the timing circuit is no longer able to trigger the triac into conduction. The electrode preheat circuit is effectively disconnected from the lamp electrodes when the lamp is in operation.

Abstract: A fluorescent lamp operating circuit includes a high frequency electronic ballast circuit for providing a controlled output to a fluorescent lamp load. A control signal is detected from the power line carrier which includes binary data indicative of the illumination level desired. The control signal comprises a multi-bit binary signal which is detected by the control circuit and used to control the frequency of the power supply circuit so that the fluorescent light illumination level may be dimmed over a wide range.

Abstract: A starter circuit for a fluorescent tube lamp is connected between the cathode heaters of the tube to provide an initial heating current and then changes to a high impedance to ignite the tube. The circuit is fed by raw rectified a.c. and has a main thyristor requiring a high holding current to maintain the initial conduction. The current through the main thyristor sets up a voltage across a series diode which triggers a second thyristor to reduce the gate voltage of the main thyristor. The main thyristor ceases conduction when the current falls below the holding value and the inductive ballast impedance then produces a high energy striking pulse for the tube. The pulse voltage is limited to increase its duration. One embodiment generates a single pulse only each time the circuit is switched on and another embodiment produces pulses for a period of time before becoming quiescent. The main thyristor and the voltage limiting means are embodied in a monolithic semiconductor structure.

Abstract: A starter circuit for use with a fluorescent lamp includes an inductor coupled in series with the lamp electrodes and a semiconductor bilateral trigger, such as a Sidac, connected between the lamp electrodes. The semiconductor bilateral switch is selected to conduct electricity at a value below the instantaneous peak voltage applied and to cease conduction at a level above the operating voltage of the lamp. When the voltage reaches the predetermined level at which the semiconductor switch turns on, current is conducted through the electrode and the bilateral trigger. When the bilateral switch turns off, a large voltage pulse is generated in the inductor which voltage pulse appears at one of the lamp electrodes. A voltage potential is therefore set up across the electrodes to the lamp fixture which is grounded ionizing ionizable material, for example, mercury, within the lamp.

Abstract: To provide for reliable ignition of low-pressure discharge lamps, particularly compact fluorescent lamps, operated at high frequency, for example in the order of about 45 kHz, an ignition circuit is connected in parallel to the lamp and serially with the electrodes (16, 17) thereof, which comprises a limiting capacitor (19) and the parallel circuit of a positive temperature coefficient (PTC) resistor (20) and a starting capacitor (18). The two capacitors (18, 19), together with an inductance (13, 14) in the operating circuit of the lamp, and a further capacity formed by a blocking capacitor (15), after preheating of the lamp electrodes by current flowing through the initially cold PTC resistor, will cause voltage rise across the resonance capacitors (18, 19) which will cause ignition of the lamp.

Abstract: A starter circuit for a fluorescent tube lamp is connected between the cathode heaters of the tube to provide an initial heating current and then changes to a high impedance to ignite the tube. The circuit is fed by raw rectified a.c. and has a main thyristor requiring a high holding current to maintain the initial conduction. The current through the main thyristor sets up a voltage across a series diode which triggers a second thyristor to reduce the gate voltage of the main thyristor. The main thyristor ceases conduction when the current falls below the holding value and the inductive ballast impedance then produces a high energy striking pulse for the tube. The pulse voltage is limited to increase its duration. One embodiment generates a single pulse only each time the circuit is switched on and another embodiment produces pulses for a period of time before becoming quiescent. The main thyristor and the voltage limiting means are embodied in a monolithic semiconductor structure.

Abstract: A film video player includes an electronic strobe light operable for repetitively firing a flash tube, to flash illuminate a solid state image sensor via a high-intensity light pulse projected onto photographic film at the vertical retrace rate of a standard television signal. A current sink circuit is provided for drawing a flash tube simmer current, to maintain an arc in the flash tube between sensor-illuminating pulses. Sensing circuitry, coupled to a junction common to the flash tube and the current sink circuit, produces a control signal corresponding to whether or not the flash tube is conducting simmer current. Switching circuitry, responsive to the control signal at the vertical retrace rate, (1) causes the overriding of the operation of a flash tube trigger circuit when the control signal indicates that the flash tube is conducting simmer current, and (2) causes the operating of the trigger circuit when the control signal indicates that the flash tube is not conducting simmer current.

Abstract: To provide for reliable starting of compact-type fluorescent lamps, or ot discharge lamps difficult to start, a voltage divider which is formed only by serially connected capacitors (C1, C2) is connected across the lamp (L), the junction point (5) of the voltage divider being connected to a charging circuit formed by a resistor (R1) and a capacitor (C3). The junction (4) between the charging resistor and capacitor (R1, C3) is connected through a diac (D) to the trigger or gate electrode (3) of a triac (T) connected across the lamp. Preferably, the capacity relationship of each one of the capacitors (C1, C2) of the voltage divider to the trigger capacitor (C3) is between about 1:1 and 1:5, desirably about 1:3. The time constant formed by the charge circuit (R1, C3), preferably, is between about 4 to 6 milliseconds, so that the charge time of the trigger capacitor (C3) is sufficiently long to provide multiple starting pulses to the triac (T) at peak values. A circuit to provide for polarity independence (FIG.

Abstract: A lighting circuit for an electric discharge lamp according to the present invention is constructed in such a way that a switching device is provided at an output terminal of a high frequency inverter which produces a substantially sinusoidal output voltage, and that, by controlling this switching device, an output to the low pressure electric discharge lamp is stopped at the rising part of the abovementioned output voltage in its half cycle, while the output is supplied to the low pressure electric discharge lamp at the voltage level in the vicinity of the maximum instantaneous value thereof. By use of the high frequency inverter of a smaller capacity and less radio noise than those in the conventional device, the operating efficiency of the low pressure electric discharge lamp can be increased.

Abstract: A method and apparatus for reducing the energy consumption of fluorescent lighting energized by an alternating voltage source comprising sensing for a particular amplitude of the alternating voltage and upon sensing such voltage amplitude establishing a given time period which is a fraction of a cycle of the alternating voltage. At the end of the given time period actively connecting the alternating voltage source to the fluorescent lighting whereby the lighting is energized for a portion of the cycle, and for a given time interval at the start of operation continuously actively connecting the alternating voltage source to the fluorescent lighting so that the components of the fluorescent lighting can efficiently warm up.

Abstract: Apparatus for starting and operating a high intensity discharge lamp includes a pair of terminals connectible to an AC service voltage source and coupled by a ballast to an HID lamp with a series connected gated switch and a non-linear dielectric element shunting the HID lamp, a series connected resistor and capacitor shunting the HID lamp and a bidirectional switch coupling the junction of the resistor and capacitor to the gate electrode of the gated switch whereby a delayed pulse of increased magnitude is applied to an HID lamp.

Abstract: A mode detector for microwave oven magnetrons is disclosed including means for sensing interruption of anode current and providing a discrete indication thereof. An alternative embodiment discloses means to count the number of such interruptions. A method of detecting incipient failure of the magnetron is disclosed wherein the discrete output of a mode detector is observed and a determination is made that an incipient failure exists when the mode detector output frequency exceeds a predetermined limit.

Abstract: Apparatus for use with a fluorescent lamp having a longitudinal axis and a filament winding at each end includes a pair of terminals formed for connection to a potential source with means for connecting one of the terminals to a filament winding, an incandescent lamp coupling the other terminal to the filament winding at the other end of the fluorescent lamp, a starting aid extending along the longitudinal axis of the fluorescent lamp and an impedance coupling the starting aid to the junction of the incandescent lamp and a filament winding of the fluorescent lamp.

Abstract: A discharge lamp lighting device comprises a discharge lamp (1) with a pair of filaments (101a, 101b), an inductive balast (2) coupled with said lamp (1) and a power supply, a non-linear dielectric element (4) coupled across said lamp (1), a semiconductor switch (3) coupled substantially parallel with said non-linear dielectric element (4), and delay means ((6,7,303c,304b,303d), (8,303c,304b,303b), (9,10,60), (6,11)) for shifting firing phase of said semiconductor switch (3) so that a spike voltage induced by said non-linear dielectric element increases gradually for every cycle of a power supply voltage.

Abstract: A starter circuit for fluorescent discharge lamps having a high reignition voltage with respect to a peak open circuit voltage wherein a timing and triggering circuit is utilized to delay the application of a the lamp voltage to a starter until the relatively high reignition voltage has passed and a normal lamp operating condition is in effect.

Abstract: A method of controlling the power output of a magnetron tube, and an electric power supply for supplying power to the tube. According to the method, power is continuously supplied to the magnetron heater. At the same time, a voltage is continuously applied across the anode and the cathode of the tube. This voltage across the anode and the cathode varies in cycles between a first value, which is substantially at or below the threshold voltage of the magnetron tube, and a second value, which is above the threshold voltage. The average magnetron power output is determined by the proportion of each cycle during which the voltage across the anode and the cathode is above the threshold voltage.

Abstract: A discharge lamp circuit in which the lamp is substantially instantaneously started and in which the power consumption of the lamp after starting is reduced with substantially no vibration due to piezoelectric effects and caused by currents flowing through a nonlinear dielectric element. An inductive stabilizer is connected in series with one of the filaments of the discharge lamp and a nonlinear circuit is connected in parallel with the filaments of the discharge lamp. The nonlinear circuit is composed of a nonlinear dielectric element and a bidirectional switching means connected in parallel with the nonlinear dielectric element. A reverse-conductive circuit is connected in series with the nonlinear circuit and in parallel with the filaments of the discharge lamp, the reverse-conductive circuit including a reverse-conductive semiconductor switch mean which is conduction-controlled in the forward direction but which is always conductive in the reverse direction.

Abstract: Apparatus for starting and operating a discharge lamp includes a starting device having bimetals and a rigid conductive member forming a switch, a ballast coupling the switch to an AC source and a discharge lamp and a spark gap each shunting the starting device with the starting device bimetals and rigid conductive device hermetically sealed in a vacuum.

Abstract: Connected in parallel to the lamp through a fuse (10) is a triac (2) the control electrode of which is connected through a diac (3) to the tap (4) of a voltage divider likewise in parallel with the lamp. The first branch of the voltage divider contains, in addition to a fixed resistor (5), at least one variable series impedance (6) which may be either a capacitor or a voltage-dependent resistor. The second branch of the voltage divider is provided by a capacitor (7). A temperature dependent NTC resistance (8) bridges a portion of the first branch and all of the second branch of the voltage divider. For use with ballasts containing a choke, it is desirable to interpose a diode bridged by a NTC resistor in the first branch of the voltage divider adjacent to the tap.

Abstract: The invention provides a power source device for an ion source, including first to third power source units coupled to the anode, the cathode and the beam extraction electrode of the ion source. The second power source unit applies an alternating voltage across the cathode. An alternating heating current then flows through the cathode. Each cycle of the alternating voltage from the second power source unit has positive and negative components with preset levels which are generated with a predetermined time interval between them. The power source device further includes a control circuit for interrupting the operation of the first and third power source units during the predetermined time interval.

Abstract: The invention relates to starting and supplying a low-pressure discharge lamp which comprises two electrodes between which a main discharge path is formed, a shunt path being electrically in parallel with at least a portion of said main discharge path.In accordance with the invention the lamp is started by means of a glow-discharge starter which is shunted by a VDR the threshold voltage of which is lower than a value determined by the geometry of the shunt path, and is higher than the minimum voltage for starting a discharge in the main discharge path. The discharge then only starts in the main discharge path.

Abstract: A discharge lamp lighting device comprises a serial connection of an inductive ballast and a discharge lamp connected across an A.C. power source, and a switching circuit connected substantially in parallel to the discharge lamp and operable to carry out two consecutive ON/OFF operations in the beginning of each half cycle of the A.C. power source while the discharge lamp is in its lit condition. The switching circuit preferably comprises a full-wave rectifier connected substantially in parallel to the discharge lamp, a switching element connected between the output terminals of the rectifier, and a control circuit for controlling the ON/OFF operation of the switching element.

Abstract: A starting circuit for discharge lamps includes a current limit device, a full wave rectifier circuit and a Cockcraft-Walton's circuit which are connected between a d.c. discharge lamp having a cathode and an anode and the input terminals of an a.c. power source. Moreover, the Cockcraft-Walton's circuit is constructed by sharing a rectifier with the full wave rectifier circuit and a preheating circuit is provided for the cathode and includes another rectifier of the full wave rectifier circuit and a switching device.

Abstract: The disclosed firing device comprises a fluorescent lamp serially connected to an inductive stabilizer, a first semiconductor switch including an SCR connected across the fluorescent lamp, and a nonlinear dielectric element serially connected to a parallel combination of a PNPN switch as a second semiconductor switch and a discharging circuit across the fluorescent lamp. The discharging circuit may comprise a resistor alone. The first semiconductor switch may include a semiconductor diode and a PNPN switch and the discharging circuit may include a resistor connected across series combination of a semiconductor diode. Alternatively, the discharging circuit may include a Zener diode and a resistor serially interconnected.

Abstract: A ballast apparatus for series-sequenced gaseous discharge devices having series-connected filaments wherein a transformer is connected to a potential source and to a pair of series-sequenced gaseous discharge devices with a starting capacitor shunting one of the gaseous discharge devices and a circuit means series-connects a filament of each of the gaseous discharge devices to the transformer by way of a rectifier means.

Abstract: A ballast apparatus for series-sequenced gaseous discharge devices includes at least one pair of series-sequenced discharge devices having series-connected filaments with a first rectifier means coupling a filament of one discharge device to the transformer and a second rectifier means coupling the series-connected filaments to the transformer whereby current flow is inhibited until both discharge devices are secured in the fixtures and dangerous socket-to-ground voltages are prevented during discharge device installation.

Abstract: A built-in starter type fluorescent lamp socket in which the starter is entirely incorporated with the socket with no protruding parts and in which it is not necessary to replace the starter. The socket includes a socket body, pairs of starter contacts and power source contacts operatively positioned in the socket body for making connection with fluorescent lamp pins, and an electronic starter positioned in the socket body and connected to the starter contacts. The electronic starter includes a non-linear dielectric element and a thyristor coupled in parallel and across the starter contacts. The anode of the thyristor is coupled through a Zener diode to the common connection point between voltage division resistors also coupled across the starter contacts. The socket body may include a casing having lamp pin inserting holes and a cover for covering the rear side of the casing wherein the cover may be shaped in the form of a box in which the electronic starter is mounted.

Abstract: Disclosed is an electron beam current stabilizing device comprising a sensing element (12) responsive to the beam current deviation from the predetermined value, a saw-tooth voltage shaper (14) connected to a high-voltage transformer (2) of an acceleration voltage source and providing periodic saw-tooth voltage, smoothly sloping portions thereof being shaped starting from the moment when the voltage at the high-voltage transformer (2) crosses zero, an adder (13) whose one input is connected to the output of the sensing element (12), and the other input, to the output of the shaper (14), a threshold element (15) connected to the output of the adder (13), a differentiator (16) connected to the output of the threshold element (15) to shape the electric driving pulses when the smoothly sloping portions of the saw-tooth voltage cross at the output of the adder (13) the threshold level of the threshold element (15), a light source connected to the output of the differentiator (16) to convert the electric driving pu

Abstract: Fluorescent lamps are flashed by modulating the lamp operating current during a given half-cycle. The other half-cycle operation is unmodulated, thereby resulting in flashing from full lamp brilliance to substantially one-half lamp brilliance. In one embodiment, the modulating circuitry is placed in the line cord providing power to the lamp. The circuitry includes a gated diode and a resistor placed in parallel with each other. A full wave line cord embodiment employs a diode bridge. In another embodiment, the modulating circuitry is placed across the terminals of a conventional fluorescent lamp starter so that current is bypassed around the starter. With this embodiment of the invention, the discharge on half of the cycle is extinguished, but current flows through the lamp electrodes, thereby keeping them hot enough to emit electrons and prevent life-damaging high cathode fall.

Abstract: A fluorescent lamp starting device in which an electronic starter is provided in the form of a hybrid integrated circuit which is mounted in a standard glow starter case and which can be utilized in a standard glow starter socket of a fluorescent lamp fixture. A nonlinear capacitor and semiconductor switch are coupled in parallel with another and across the external terminals of the starter. The nonlinear capacitor is provided in the form of a thin plate while the semiconductor switch is provided on an IC substrate substantially equal in size to the nonlinear capacitor.

Abstract: An electronic device (20-61) for the starting and a.c. operation of a capacitively stabilized discharge lamp (7) includes a controlled semiconductor switching element (22) which, in the operating condition of the lamp, is briefly conductive in each half cycle of the AC supply. The control circuit of the semiconductor switching element (22) includes a second switching element (25) which, during the starting procedure of the lamp, ensures that the semiconductor switching element (22) is made conductive only every alternate half cycle thereby to improve the ignition of the lamp.

Abstract: The invention relates to a glow-discharge starter (10) having a bimetallic electrode (11) and a rare gas.According to the invention the glow-discharge starter also comprises a reversible getter (13) which, when the temperature increases, gives off a gas and, when the temperature decreases, absorbs the gas and the value of the gas pressure also determines the electric conductivity of the glow-discharge starter.A glow-discharge starter is thereby obtained in which undesired breakdown of the glow-discharge starter can be prevented by controlling the gettering temperature.

Abstract: A discharge lamp lighting circuit system comprises a discharge lamp, an intermittent oscillation circuit, and an arrangement for controlling the energy supplied for lighting the discharge lamp with a high power factor. The intermittent oscillation circuit is energized by a low frequency a.c. power supply, i.e. a commercial alternating current power supply, for intermittently generating a high frequency high voltage in each half cycle of the alternating current of the low frequency a.c. power supply. By supplying the low frequency alternating current voltage and the intermittent high frequency high voltage to the lamp the discharge lamp is reignited in each half cycle of the a.c. of the low frequency alternating current power supply and the lit state of the discharge lamp is sustained by the low frequency alternating current voltage.

Abstract: An improved starter switch which provides a rapid firing of a fluorescent lamp within 0.8 second has been found. An external appearance and the size of the present starter switch are almost the same as those of a prior glow switch which is slow to fire a fluorescent lamp, therefore, the present starter switch is replaceable to a prior glow switch by merely inserting the present starter switch to a socket of a prior glow switch. The present starter switch has a connector cap which is to be able to be engaged with a socket for a glow switch, a printed circuit board mounting circuit components and connected to said connector cap by lead lines, and a housing fixed to said cap and covering said printed circuit board.

Abstract: A screw-in fluorescent light unit having two light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a resistor is added to ballast the lamp for low light output. A bilateral switch device is connected across the resistor to facilitate lamp starting at the low light output.

Abstract: A screw-in fluorescent light unit having high and low light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a variable dimming circuit is added to ballast the lamp for variable low light output.

Abstract: Microwave oven with a self-regulating circuit operated from a low voltage a.c. source based upon a substantially constant current transformer and condenser series combination and having a return path for current on alternate half cycles. For defrosting food the magnetron is operated at partial power which is achieved by decreasing the voltage applied to the magnetron. This is done either by increasing the capacitive reactance in series with the secondary of the transformer or by decreasing the secondary voltage. Switching problems are solved by providing the arrangement of the invention at the grounded end of the transformer secondary. The self-regulating circuit is required to be of the type which has one end of the secondary winding grounded.

Abstract: A parallel circuit of a capacitor and a switching element is connected to a hot cathode discharge lamp lighting device using a high frequency and high voltage generating means for permitting the flow of current into the filaments of the hot cathode type discharge lamp only at the lamp starting time. The switching element of the parallel circuit is a current controlled resistance element, such as a switching semiconductor, having a break-over voltage V.sub.BO lower than the capacitor terminal voltage during the initial ignition period and higher than the capacitor terminal voltage during the reignition or operation period, whereby the filament current to the discharge lamp may be used for preheating of the filament in the initial ignition period. The filament current may be stopped or reduced by turning off of the switching element by raising the terminal voltage of the capacitor in the reignition period during normal operation.

Abstract: A fluorescent lighting device which includes a preheating type fluorescent discharge tube and as the ballast thereof an incandescent bulb. The fluorescent lighting device is ignited by the use of a pulse transformer and a neon tube. A semiconductor element may be used in place of the neon tube.

Abstract: A discharge lamp starting device such as for a fluorescent lamp in which a nonlinear capacitor is connected in parallel with a discharge lamp with a Zener diode connected in series with the nonlinear capacitor. A semiconductor switching device, such as a diode thyristor, is connected in parallel with the discharge lamp. Due to the presence of the Zener diode, the semiconductor switching device can have a wide range of threshold voltage so that the cost of the device is low.

Abstract: Energy-saving circuitry for a rapid-start fluorescent lighting system includes a reactance-modifying capacitor coupled in series with first and second fluorescent lamps and includes a filament switch which is operative to conduct filament heating current during starting of the first lamp. The filament switch is coupled between filaments at opposite ends of the first fluorescent lamp and triggers to a low impedance state in response to the lamp starting voltage. A capacitor bypass switch can be coupled in parallel with the reactance-modifying capacitor to reduce the impedance of the series circuit during lamp starting.

Abstract: A power source for operating gas discharge lamps and other loads at high frequency, typically utilizing a dc source or a rectified ac source to produce a high frequency output. An inverter with oscillator circuit and first transformer has the secondary or load winding connected to a second transformer which provides a feedback signal to the transistor of the oscillator circuit through another transistor which functions as a variable resistance in the base drive of the oscillator transistor for maintaining power to the load substantially constant. A third winding on the inverter transformer is used to provide a control signal to the base circuit of the variable resistance for protecting the circuit components during an open secondary or no load condition.

Abstract: A simplified power source for fluorescent lamps is characterized as that the filaments of the fluorescent lamps are connected in series with the primary winding of a transformer, an oscillator circuit and the power source so that the oscillating current will exert high voltage across the primary winding to start and drive the fluorescent lamps and when the fluorescent lamps are removed from their sockets, the oscillator circuit will be opened to prevent from occurring high tension for safety measure.