Abstract: Fluorescent type lamps are arranged to have high frequency power derived from standard, commercial A.C. sources either directly or from power levels distributed from a master ballast. When the master ballast is employed, it functions as an interface between the primary power source and a distribution network to one or more modules so as to relieve the modules of operations such as initial power form conversions, filtering and power factors correcting which require large components. The module or modules driven by the master ballast output are contained within the lamp envelope or attached as an extension of the lamp envelope. The module is formed of elements mounted as a miniaturized unit configured to fit within the lamp envelope or to attach to the end of the envelope. The module includes oscillator components mounted on an envelope board so as to form an assembly with a cross-section compatible with the perimeter of the envelope itself.

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: A ballast circuit for driving fluorescent lamps characterized by a minimum of components has a power transformer constructed to present a source impedance integrated with the transformer and in series with the lamp load sufficient to regulate the load current to within 10% for a selected maximum wattage fluorescent lamp load, such as 18 or 36 watt, and any lesser fluorescent lamp loads. The transformer has a high voltage secondary winding with a reflected impedance at least 6.0 times greater than the reflected impedance of the selected worst case fluorescent lamp wattage load. The integrated magnetics design of this ballast also provides passive short circuit protection, filament current reduction after lamp strike, and cold temperature start-up with a minimum of circuit components.

Abstract: Radiated emission is reduced in a vacuum fluorescent tube having a pulsed filament current in a variable frequency range above audible frequencies. A driver circuit produces a fixed width pulse of filament current when triggered by a random frequency generator. The frequency generator comprises a shift register and XOR gates intercoupled to generate a random series of logic outputs, a filter to produce a randomly varying voltage from the logic outputs, and a voltage-to-frequency converter responsive to the filter voltage to yield a random frequency in the required range. The random frequency triggers the driver and clocks the shift register.

Abstract: Method and apparatus for igniting fluorescent lamps at a predetermined temperature of their cathodes. In the present invention, it is the resistance of the cold lamp cathodes that is always measured and ignition occurs as a result of the relationships or conditions of the cold resistance to the hot resistance or the voltage relationship of cold to hot, so that the absolute value has no influence and correct preheating is achieved with all types of lamps.

Abstract: A method is provided in which a relatively cold lamp filament may be turned on for a brief period of time, then turned off, then turned on again, then off again, and this process repeated for successively longer periods of on time, until eventually the filament power is left on continuously. This "pulse starting" may be controlled by a programmable microcontroller in association with a power supply to the lamp filament. The result is a longer lasting lamp filament.

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

Abstract: A fluorescent lamp starter which includes: a series circuit to be connected to a power source for supplying an AC voltage, including a ballast and a fluorescent lamp equipped with electrodes; a transistor having a collector and an emitter connected through a diode between the electrodes on an opposite side of the fluorescent lamp in which the power source is not connected; a control voltage supply means having a resistance means and a capacitor, which are operated by a voltage between the collector and the emitter of the transistor; and a transistor base control means for switching the transistor by a total voltage of a part of a voltage generated in the resistance means of the control voltage supply means and a voltage generated in the capacitor thereof.

Abstract: A power supply for a VF display generates a DC filament voltage from a battery by either a switched transformer supply or a monolithic regulator circuit. Where a higher-than-battery voltage is needed for anode and grid voltages, another monolithic regulator circuit or the switched transformer is used. An H-switch develops an alternating voltage from the DC voltage and applies it to the display filament. A controller for the H-switch is a logic circuit including flip-flops which toggle in response to a low frequency pulsed dimmer signal to synchronize the filament half cycles with the dimmer phases. Slew rate control ramps the H-switch control signal to produce a trapezoidal waveform in the filament current having reduced radio frequency emissions.

Abstract: A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Abstract: A method and apparatus for automatically adjusting the light intensity output of a fluorescent lamp of a document scanner. The fluorescent lamp current level control apparatus comprises preheating circuitry for applying low voltage pulses of alternating polarity across filaments of the lamp, the low voltage pulses sufficient to preheat the filaments but insufficient to cause the lamp to fluoresce; high voltage circuitry for applying high voltage pulses of alternating polarity across the lamp, the high voltage pulses sufficient to cause the lamp to fluoresce; and control circuitry for receiving a first signal (PWM (D)) indicative of a desired level of current in the filaments, sensing a current indicative of the actual level of current in the filaments, and controlling the high voltage circuitry to cause the actual level of current to tend toward the desired level of current.

Abstract: A display device having a display tube including a cold cathode, for example a PN emitter (PNE), has the terminals of the PN emitter (PNE) coupled between first terminals of a first (CR1) and a second (CR2) current mirror. The first current repeater (CR1) is connected to an output of an amplifier (AMP) whose feedback input (FI) is connected to second terminals of the first (CR1) and second (CR2) current mirrors.

Abstract: A circuit, having a split primary transformer, for controlling the warm-up, ignition and normal operating stages of a fluorescent tube initially applies in phase voltages to opposite sides of the split primary transformer during a warm-up stage; during an ignition stage and during the normal tube operation, out of phase voltage waveforms are applied to opposite sides of the split primary of the transformer.

Abstract: A cathode that uses the tunneling effect of electrons through a layer of insulation consisting of alpha alumina in combination with a circuit to provide a pulsed current caused by a current interrupter within a frequency range of one to ten KHz.

Abstract: A fluorescent lamp system including a ballast with primary and secondary windings and a switch for each of the plurality of electrodes of the lamp system. Each switch is operable in response to the voltage across its associated lamp after its associated lamp turns on to interrupt the connection of an associated electrode to its associated heater winding, and wherein at least two of the plurality of switches conduct current which flows through a semiconductor conducting device before the lamps turn on.

Abstract: A fluorescent lamp system including a ballast with primary and secondary windings and a switch for each electrode of the lamp system. Each switch is operable in response to the voltage across its associated lamp after its associated lamp turns on to interrupt the connection of an associated electrode to its associated heater winding and wherein at least one of said heater windings is a portion of the secondary winding.

Abstract: A fluorescent lamp system including a switch for each electrode of the lamp system wherein each switch is operable in response to the voltage across its associated lamp after its associated lamp turns on to interrupt the connection of an associated electrode to its associated heater winding.

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: A microwave oven with an invertor control power source produces a microwave by the use of the magnetron in relation to the high frequency power generated by the invertor control power source. The heat sensitive ferreit beads provided on the lead wire for transmitting the high frequency power to the magnetron changes the inductance of the wire from the high level to the low level at around a threshold temperature lower than the working equilibrium temperature of the magnetron. The cathode filament current remains within the allowable range, and the moding of the magnetron is prevented. The magnetron can operate in a long life time.

Abstract: The invention described here is concerning a power supply device of a thermionic emitting cathode, an electron source in an electron vapor deposition plant. This device is provided with a transmitter whose secondary feeds the thermionic emitting cathode and whose primary is supplied with pulse width modulated and controlled heater current (I.sub.HC). The control of this heater current (I.sub.HC) is provided directly by introducing the heater current nominal value (I.sub.HC nominal) from the outside or in a manner that the current emitted (I.sub.EC) from the thermionic emitting cathode is monitored and fed galvanically decoupled to the controller. Here the galvanic decoupled connection is achieved by a pulse width modulated, optical signal.

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 method and system for providing a wide range of variable brightness levels for a vacuum fluorescent (VF) display by changing the duty cycle of the driving signal beyond the limits of normal driving techniques by varying the frequency as well as the on-time of the driving signal. The driving signal is multiplexed by a programmed driver microcomputer to drive a plurality of grids. Consequently, by varying the frequency, the multiplex period is also varied. The driver microcomputer communicates with a host microcomputer as well as drivers and grids of the VF display to control the VF display. In addition, the driver microcomputer samples a VF filament signal to synchronize the VF display multiplex frequency with the frequency of the VF filament signal to reduce flicker at low display brightness levels. The method and system achieve a continuously variable appearance of the VF display from full bright to barely discernable.

Abstract: A driving circuit for a low-pressure discharge lamp, particularly a compact fluorescent lamp, features a heating transformer with two separate secondary windings, which are respectively permanently connected to the lamp electrodes, and furnish them with pre-heating current. Parallel to the primary winding of the transformer, there is connected a series circuit of an operating switch, a ballast inductor, and the discharge path formed between the lamp electrodes. The electrodes are connected to each other via a starter connected in parallel to the discharge path.

Abstract: A negative glow fluorescent lamp includes a light-transmissive envelope enclosing a fill material which emits ultraviolet radiation upon excitation, a phosphor coating on an inner surface of the envelope, the phosphor coating emitting visible light upon absorption of ultraviolet radiation, a cathode located within the envelope for emitting electrons, first and second cathode leads extending through the envelope, an anode located in the envelope and spaced from the cathode for collecting electrons and first and second diodes coupled between opposite ends of the anode and the first and second cathode leads, respectively. The glow lamp can include one or more insulating discharge barriers which surround the cathode and block electron bombardment of the cathode during positive half cycles of the AC voltage. The discharge barriers are preferably as large in area as is practical and can be coated with an ultraviolet-reflecting material or with a phosphor layer.

Abstract: A circuit for starting and operating fluorescent lamps from an a-c low frequency power source includes a reactive ballast means connected to ballast the lamps and having a non-linear characteristic for producing a plurality of harmonics of the power source frequency, and a capacitor and a cathode heating transformer connected in series and connected to receive power from said ballast means and resonant in a frequency range encompassing a plurality of said harmonics. This resonant voltage is applied across the lamps to aid the starting of their discharge and thereafter the lamps operate at the a-c power source frequency. The aforesaid resonance frequency range preferably is broad enough to encompass several harmonics of the power source frequency, for example the third through the ninth harmonics (180 to 540 Hz for a source frequency of 80 Hz). Preferably a switch is connected in series with the capacitor and cathode heating transformer for opening the cathode heating circuit when the lamps are operating.

Abstract: A ballast circuit for a discharge tube such as a fluorescent tube, mercury vapor, sodium vapor or metal halide lamp is disclosed. D.C. power is provided alternately between two output driver stages and an a.c. neutral return line. In output transformerless (OTL) embodiments of the invention, a series connection of a reactance circuit and the tube is connected between the push pull point and the a.c. neutral return line. In transformer embodiments of the invention, a primary winding of a transformer is connected in series with the reactance circuit. The tube or load is connected across an output winding of the transformer with the electrical effect that the load is in series with the reactance circuit. Alternative arrangements of transformer input windings are provided. The first includes two input primary windings wound in opposite directions with the circuit arranged such that current flows in one or the other of the input transformer windings on alternating half cycles of the control signal.

Abstract: A negative glow fluorescent lamp includes a light-transmissive envelope enclosing a fill material which emits ultraviolet radiation upon excitation, a phosphor coating on an inner surface of the envelope, the phosphor coating emitting visible light upon absorption of ultraviolet radiation, a cathode located within the envelope for emitting electrons, first and second cathode leads extending through the envelope, an anode located in the envelope and spaced from the cathode for collecting electrons and first and second diodes coupled between opposite ends of the anode and the first and second cathode leads, respectively. The glow lamp can include one or more insulating discharge barriers which surround the cathode and block electron bombardment of the cathode during positive half cycles of the AC voltage. The discharge barriers are preferably as large in area as is practical and can be coated with an ultraviolet-reflecting material or with a phosphor layer.

Abstract: A power supply for vacuum fluorescent displays has a source of a relatively high frequency signal which is provided to a power driver amplifier which is also supplied with a desired supply voltage. The output of the driver amplifier is a square-wave signal varying between approximately zero and the supply voltage; this signal is provided to the filament of the vacuum fluorescent display such that the filament is heated and is self-biased at a DC level which is substantially one-half the supply voltage level. Self-biasing a capacitor between the filament and ground, which also allows the RMS level of the voltage across the filament to be controlled by controlling the frequency of the output signal from the driver amplifier. The voltage may be regulated by comparing the RMS voltage across the filament with a reference and using the difference to control the frequency of oscillation of the source.

Abstract: A transformerless power circuit for heating a filament of a fluorescent display comprises integrated circuit timing means comprising two timers having output terminals for developing alternating output signals of opposite polarity with respect to a d.c. bias-component of each output signal. The circuit also includes external resistor means, condenser means and voltage supply means for controlling the frequency of the timers. The circuit also includes d.c. bias component resistor means coupled to the output terminals for developing biascomponents of the same polarity at the display filament terminals with respect to a common reference potential for connection to a fluorescent display filament.

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: Apparatus for reducing the effects of beat frequencies in systems having multiple oscillators wherein a wide band frequency modulator operates to alter the frequency supplied by one of the oscillators at a rate high enough that any beat frequencies occur at rates undetectable to the human eye.

Abstract: A self-oscillating inverter-type fluorescent lamp ballast has two modes of operation: (a) a first mode in which the inversion frequency is about 70 kHz and is resonant with a first tuned circuit by which power is supplied to the cathodes of the fluorescent lamp; and (b) a second mode in which the inversion frequency is about 30 kHz and is resonant with a second tuned circuit by which main lamp power is supplied. When the ballast is initially powered-up, it starts operation in its first mode, thereby providing cathode heating power without yet providing main lamp power. About one second later, after the cathodes have reached full incandescence, the inverter automatically changes into its second mode, thereby providing main lamp power while at the same time removing cathode heating power. If for some reason the lamp were not to ignite within about 10 milli-seconds, the inverter reverts back into its first mode; thereafter cycling between its two modes until the lamp does ignite.

Abstract: A diming circuit for a hot cathode fluorescent lamp is operated in a push-pull mode whereby the hot filaments are alternately the cathode and the anode. Both filaments thus experience similar degradation with time at all brightness levels, thereby enhancing and lengthening the life of the lamp.

Abstract: In a voltage resonance type switching power source apparatus, which has a step-up transformer, a resonance capacitor connected in series with a primary winding of the transformer, and a transistor connected in parallel with the capacitor to cause a resonant oscillation current by the on-off operation thereof, an on signal of the transistor is produced in synchronism with a second signal, which is obtained by delaying a first signal depending on a voltage induced in a detecting winding provided in the transformer by a predetermined delay time.

Abstract: An arrangement for providing power to a cooking magnetron uses a ful wave bridge inverter circuit connected to a power transformer. The filament of the magnetron is energized by a secondary winding of the power transformer. The inverter controls the microwave output of the magnetron by duty cycle control. In order to stabilize filament power against variations due to changes in the inverter duty cycle, a saturable reactor is connected in series with the filament. The reactor has a control winding which changes the impedance of the reactor in order to compensate for variations in the power supplied by the power transformer. The control winding of the reactor may be supplied with a voltage dependent upon the magnetron current. Since the magnetron current depends on the duty cycle of the inverter, this voltage may be used to make the impedance of the reactor dependent upon the duty cycle.

Abstract: A system and associated method for operating a gas discharge lamp so as to provide a positive voltage-current characteristic. An AC or DC source is used to provide electron heating, without in itself providing ionization, of the lamp gas. Superimposed on this signal is a pulsed source of power having an average output power substantially less than the AC or DC source power for providing ionization of the lamp gas.

Abstract: A video apparatus capable of operating at different line deflection frequencies incorporates a CRT electron gun assembly heater supply voltage circuit that maintains a constant rms voltage level independent of the line deflection frequency. The heater supply includes a transformer winding located on the line deflection driver transformer. The duty cycle of the developed AC voltage waveform remains substantially constant independent of the line deflection frequency, so that the AC voltage may be applied to the heater circuit.

Abstract: A circuit for operating a discharge lamp (1) by means of a direct voltage. The circuit comprises direct voltage terminals (A,B) for connection of a direct voltage source, alternating voltage output terminals (K,L) for connection to the discharge lamp, a direct voltage/alternating voltage sine converter (3), and a current limiter (5) for limiting the current through the lamp in its operating condition. A controllable direct voltage converter (2) is coupled between the sine converter and the direct voltage input terminals.

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: With the AC voltage output from an inverter series-driving a high-Q parallel-loaded resonant L-C circuit, and with the parallel-connected load being of a type that needs to be conditioned before it will absorb power (as would be the case with loads such as magnetrons or fluorescent lamps), the inverter and/or the L-C circuit may be destructively overloaded during the time it takes for the load to become conditioned.In a power-line-operated inverter-type power supply with such a high-Q parallel-loaded resonant L-C circuit series-connected across its output, subject invention provides for means to prevent such destructive overload. In this power supply, the unfiltered pulsed DC output of a full-wave power-line-supplied rectifier is applied to a pair of inverters: an auxiliary inverter for pre-conditioning the load, and a main inverter for powering the load.

Abstract: A radar transmitter includes a ripple and droop reduction circuit to reduce the ripple and droop of the beam (power) supply. A beam supply filter capacitor is connected to the source of power and an operational amplifier has its balanced input ac connected across the beam supply capacitor. A transistorized amplifier stage inverts the signal from the operational amplifier and amplifies its absolute value up to the same level appearing across the beam supply filter capacitor. A transistorized follower stage is connected to the transistorized amplifier stage for receiving the inverted signal and producing a low impedance output for insertion in series with the beam supply filter capacitor for ripple and droop cancellation. A traveling-wave-tube is connected to the supply power capacitor which receives the ripple and droop free capacitor output and produces substantially consistent pulses for transmission.

Abstract: In a power-line-operated inverter-type power supply for the magnetron in a microwave oven, power is provided to the magnetron from the inverter by way of a series-excited resonant LC circuit, the magnetron load being connected in parallel with the tank capacitor of this L-C circuit. This arrangement provides for good matching between the output characteristics of the inverter and the operating characteristics of the magnetron. To prevent potentially destructive overload of the inverter, as may occur if the inverter's output voltage is series-applied to the resonant L-C circuit before the magnetron is ready to absorb power, inverter oscillation is not initiated until after the magnetron cathode has been heated to incandescence.

Abstract: The preferred embodiment provides such a fluorescent tube ignitor having a plurality of auxiliary electrodes provided in the periphery of the tube wall of each fluorescent tube, while the potentials of these auxiliary electrodes are set at a specific level equal to or lower than those of the low-voltage-applied filament circuits of each fluorescent tube. Integration and simplification of the preheat circuit at one-end of respective fluorescent tubes securely realizes a still smaller size of the ignitor, cost reduction, suppression of noise interference, and easier and faster start of illumination.

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 device to reduce power consumption in a rapid-start fluorescent lighting fixture having one or more lamps and a conventional ballast. The device includes a step-up isolation transformer, a capacitor connected in parallel with a bleed resistor and in series with a protective fuse all across the transformer. The device being mounted external of the ballast and wired in series between the ballast and the filament of a lamp to present a symmetrical load to the ballast circuit. In one embodiment the capacitor of the device is connected between the primary and secondary windings of the transformer by taps intermediate of the windings with an optimum connection at the center taps of the windings. In a second embodiment the capacitor is connected between either lead of the primary winding of the transformer and the center tap of the secondary winding.

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 dimming system for fluorescent tubes wherein counter electromotive forces generated during switch off of the tubes are used to maintain filaments of the fluorescent tubes heated during switch off periods of the tube, the dimming system having source terminals for connection to a source of power, the power having zero phases, load terminals for connection to the fluorescent tubes, a switch connected to the source terminals and to the load terminals for controlling the supply of power to the load terminals, a zero phase firing circuit connected to the switch for energizing the switch to supply power to the load terminals at the zero phases, a phase turn off circuit connected to the switch for deenergizing the switch to switch off power to the load terminals at phases of the power other than the zero phases, and a switch off filament heating control circuit connected to the switch for converting counter electromotive forces generated at switch off of the tube into power for supply to the filaments during switc