Abstract: A dimming ballast system wherein the light output of the lamp is controlled by a remote source. The ballast output voltage is regulated by a voltage control feedback loop, the dimming function being achieved by varying the set point of the control loop. The remote control signal, coded by interrupting the current flow to the ballast for a short period, is processed digitally by a microcomputer which generates information to vary the control set point. Circuit means are provided to control the filament voltage of the fluorescent lamps such that as the lamps are dimmed down, the filament voltage is maintained or slightly increased, thus prolonging lamp life and stabilizing the lamp light output.

Abstract: An apparatus for use in dimming florescent lamps by alternating cathodes operated with pulsating unidirectional arc currents for a duration that is long relative to the filament thermal time constant, but short in relation to the mercury migration time constant of the florescent lamp. The invention provides apparatus using full bridge switching and full bridge clamping topology in a trigger driver as well as a power driver to prevent low voltage power supply "ride up". The invention further provides means for sensing cathode heater current to detect a failed cathode and to control the phase switching to a good cathode if a cathode failure occurs. The invention further provides apparatus for a balanced-to-group ground lamp drive voltage for improved ignition of the lamp plasma and better lamp luminance uniformity when the lamp is operated dimly. A logarithmic amplifier is provided in a closed loop operation for analog compression and also to provide a logarithmic dimming response.

Abstract: A magnetic-type ballast powers two series-connected fluorescent lamps from a 277 Volt power line. Except when the lamps are loading the ballast, an electronic control circuit provides an intermittently interrupted short circuit across the two lamps: providing for socket voltages high enough to permit lamp ignition for a period of about 25 milli-seconds every two seconds or so, but keeping the average socket voltages low enough to satisfy safety requirements.When initially connecting power to the lamp-ballast combination, the control circuit enters its short circuit state and remains there for two seconds. Then, after two seconds, the control circuit switches into an open circuit, thereby permitting the voltage across the lamps to become high enough to cause lamp starting within a few milli-seconds. If the lamps fail to start, the electronic circuit reverts back to a short circuit within 25 milli-seconds.

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 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 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: An electron tube device comprising an electron tube having a line cathode, and an electric power source for supplying power pulses to the line cathode. The electron tube device comprises determination means for determining, during a power pulse, the value of a physical quantity which depends on the temperature of the line cathode, comparison means for comparing the value with a reference value and for supplying a control signal, and termination means to end the power pulse in dependence on the control signal. Consequently, the temperature of the line cathode is more stable.

Abstract: A starter circuit for a discharge lamp includes a current control circuit which initially has a low impedance so as to produce an initial cathode heating current for the lamp. The current control circuit is switched into a high impedance condition by means of a control voltage applied to its gate thereby causing a high voltage striking pulse to be applied across the lamp. A field effect transistor is effective to modify the control voltage to the gate such that the starting circuit is effective to produce a succession of starting pulses across the lamp during each half cycle of a rectified AC supply.

Abstract: A three pole relay which operates in response to the flow of normal operating current across fluorescent lamps to activate a coil, the coil coperating 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 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: In a head-up display apparatus for a vehicle, there are employed, a fluorescent display tube having a filament, a grid, and an anode positioned in a predetermined positional relationship; a power supply circuit for supplying a filament current to the filament of the tube and an anode voltage to the anode thereof; a display controller coupled to a display switch, for controlling the display tube so as to display various information of a vehicle on the display tube in response to a vehicle information signal and a switch signal of the display switch, the display switch being operated so as to display/erase the various information on/from the tube; and, a synchronized switching unit for controlling the supply of the filament current to the filament from the power supply circuit in synchronism with the switching signal of the display switch supplied from the display controller.

Abstract: A DC/AC converter for igniting and supplying a gas discharge lamp (1). The converter has two input terminals (C, D) intended to be connected to a DC voltage source, said input terminals (C, D) being connected together by means of a series arrangement including a load circuit comprising at least an induction coil (10) and a parallel arrangement of the lamp and a capacitor (12), as well as a first semiconductor switching element (13). The load circuit is shunted by a circuit comprising a second semiconductor switching element (14). The semiconductor switching elements (13, 14) are rendered alternately conductive and non-conductive by means of control circuits (13a, 14a). A second capacitor (11) is arranged in series with the induction coil (10) and the lamp. The second capacitor is shunted by a third switching element (15) which is non-conductive during the pre-heat period of the lamp electrodes (2, 3) and is conductive at least during ignition of the lamp.

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.

Abstract: To provide for automatic disconnect upon failure of a filament of one (E2) f the electrodes of a fluorescent lamp, an output terminal (P1) of a power rectifier is connected through the filament to a supply terminal (P3) of a push-pull frequency generator formed by two transistors (T1, T2). The fluorescent lamp (LP) has its other electrode (E1) connected to a common terminal between two transistors (T1, T2) of the high-frequency generator. A series resonance circuit (L1, C6, C8) is capacitor-coupled (C7) to the lamp. Upon failure of the filament of the first electrode (E2), or removal of the lamp from its lamp sockets, power supply to the transistor oscillator or frequency generator circuit is interrupted, so that the oscillator is deenergized; upon insertion of an operative lamp in the lamp circuit, the circuit is closed so that the fluorescent lamp is automatically started by the push-pull oscillator (3) formed by the two transistors (T1, T2) and associated circuitry.

Abstract: A DC/AC converter for igniting and supplying a gas discharge lamp (1) has two input terminals (C, D) intended to be connected to a DC voltage source. These input terminals are connected together by means of a series arrangement of a load circuit comprising at least the discharge lamp (1) and an induction coil (8), as well as a first semiconductor switching element (9). This load circuit being shunted by a circuit comprising a second semiconductor switching element (10). The switching elements (9, 10) are rendered alternately conductive and non conductive at a high frequency. The lamp is shunted by a third semiconductor switching element (12) which is conductive while the lamp electrodes (2, 3) are being pre-heated, whereafter the converter is rendered inoperative for a short period of time in order to ignite the lamp, which time is shorter than the time required to cool the lamp electrodes to below their emission temperature. The converter is thereafter rendered operative again.

Abstract: In a power-line-operated inverter-type fluorescent lamp ballast with a high-Q parallel-loaded resonant L-C circuit series-connected across the inverter's output, subject invention provides for means to prevent the destructive overload that may occur during the lamp starting period or if the lamp is removed or somehow fails to operate. In this ballast, the unfiltered pulsed DC output of a full-wave power-line-supplied rectifier means is applied to a pair of inverters: an auxiliary inverter for pre-conditioning the fluorescent lamp, and a main inverter for powering the lamp. The auxiliary inverter starts operating immediately upon application of power from the power line, and therefore immediately starts the process of pre-conditioning. The main inverter, however, is not started until after the lamp has completed its conditioning, at which time the lamp will adequately load the series-resonant L-C circuit and thereby prevent destructive overload.

Abstract: In a magnetron power supply for obtaining a high voltage for an anode by an inverter circuit, there is disclosed the improvement including a detector for detecting an AC output current of a secondary-side high voltage winding of a transformer instead of detecting an anode current (after being rectified) for the magnetron to control a magnetron output to a desired value. In this constitution, a current value is detected by clipping a positive or negative side of an output of the detector.

Abstract: A magnetron feeding apparatus includes an inverter circuit for converting DC power into high-frequency power; a high-tension transformer for converting the high-frequency power into high-tension power to be supplied to the magnetron; an output voltage detector for detecting the output voltage of the high-tension transformer; an input current detector for detecting the input current into the inverter circuit; a power controller for controlling the operation of the inverter circuit in response to the output voltage detected by the output voltage detector and the input current detected by the input current detector.

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: A power supply for a magnetron includes a rectifying circuit, a switching circuit, and a transformer. The rectifying circuit converts an ac-power source signal into a dc-power source signal. The switching circuit converts the dc-power source signal output from the rectifying circuit into a high-frequency signal in accordance with a driving circuit. A transformer connected to the switching circuit converts the high-frequency signal into a high-voltage high-frequency signal for driving the magnetron. The transformer includes a primary winding connected to the switching circuit, a secondary winding connected to the magnetron, a tertiary winding connected to a cathode heater of said magnetron, and a fourth winding connected to the driving circuit. The coupling coefficient between the fourth winding and the second winding is larger than the coupling coefficient between the fourth winding and the primary winding.

Abstract: A starting and operating circuit for a super compact fluorescent lamp includes ballast and discharge circuits for applying current to the filaments of the lamp and then apply starting pulses which enable the lamp to commence operation. The circuits include discharge devices and assure operation and proper starting of the lamp under low temperature as well as moderate temperature conditions.

Abstract: An attachment is provided for connection in fluorescent lamp circuits for reducing power consumption. The attachment is particularly designed for use with fluorescent lamp circuits having an encapsulated ballast including a transformer and capacitance. The attachment includes an isolation transformer with a capacitor and a resistor connected across the transformer, and an inductance connected in line with the primary of the ballast transformer with a resettable thermal switch connected to shut down the ballast transformer in response to high current overload conditions, and a surge voltage protection circuit connected through the thermal switch to shut down the ballast in response to a ballast power factor capacitor failure. The ballast and power reducer cooperate to produce a substantially square wave output resulting in increased system efficacy, reduced lamp lumen depreciation, and increased lamp life.

Abstract: A power supply line has two to four lead wires which are selectively connectable with terminals (10a-10d) of a transformerless AC-to-DC converter (A). The lead wire interconnection scheme is selected (FIGS. 1A-1D) in accordance with whether the line signal is single phase or three phase and whether the line voltage is 220 or 440 volts. The AC-to-DC converter produces a 620 volt DC, signal across its outputs (26, 28). A first inverter (B) converts to a pulsed AC signal and applies it across opposite phased primary windings (46a, 46b) of a step up transformer (C). Two pair of alternately phased secondary windings (48a-48d) and rectifier bridges (50, 52) provide a high voltage DC bias across a cathode (54) and an anode (56) of an x-ray tube (D). A summing junction (66) compares a voltage sensed across the x-ray tube with a reference voltage and generates a voltage deviation signal.

Abstract: A power control device for a microwave cooking oven includes a regulator of the anode voltage of the magnetron and a heater voltage source. The anode voltage regulator includes a d.c. voltage bridge-type converter, a transformer, a rectifier and a filter. The heater voltage source includes a half-bridge d.c. to a.c. voltage converter. The half-bridge and bridge converters are controlled each by signals coming from the respective generators of pulse sequences.

Abstract: A compact, low electrical noise power supply for fluorescent lights used in conjunction with a borehole television system. The outputs of first and second power sources are combined to initiate operation of the fluorescent light. After the operation of the light has been initiated, the second power source is disabled and the light is maintained in operation by the first source of electric power. In the preferred embodiment, the first source of electric power is a source of high voltage DC current and the second source of electric power is a high frequency oscillator. A transformer is provided to combine the outputs of the two sources of electric power. The operation of the oscillator is controlled by a momentary start switch which disables the oscillator after the light has been activated.

Abstract: A circuit for starting, operating and instant hot restarting of high intensity gaseous discharge lamps utilizes a conventional ballast, an ignition transformer and a pulse transformer. The ignition transformer is connected across the ballast output and is in circuit with a storage capacitor and a spark gap device which, in combination, provide high frequency, high voltage pulses to a pulse transformer which is in circuit with the high intensity gasesous discharge lamp. There are means to limit the duration during which the high frequency, high voltage pulses are applied to ignite the lamp and there is a current sensitive timing circuit breaker to protect the lamp and ignition circuit.

Abstract: The invention relates to an electric arrangement for operating a an electric discharge lamp (13) which is connected in series with a coil (14) and a switch (15) to a pulsatory direct voltage source. The combination of the lamp and the coil is shunted by a rectifier. The lamp is shunted by a capacitor (18) and the switch is periodically rendered conductive at an instant when the instantaneous voltage of the pulsatory direct voltage source is between 0.5 and 0.8 times the then required re-ignition voltage of the lamp. The voltage build up across the capacitor (18) after the switch has become conducting causes the lamp to reignite. The luminous efficacy of the lamp is comparatively high.

Abstract: A fluorescent lamp includes a circuit breaker having a sealed glass envelope with a pair of electrical conductors sealed therein, and a bimetal switch of U-shape form having one leg portion attached to one of the electrical conductors and a second leg portion forming a knife-edge contact with the other electrical conductors.

Abstract: A method for operating an ion source having a filament-cathode and an anode. The method includes supplying direct current electrical power between the anode and the filament-cathode characterized by substantially constant arc current there between and varying arc voltage on the filament-cathode. Direct current electrical power is also supplied across the filament-cathode. The value of the arc voltage is monitored and the magnitude of electrical power supplied to the filament-cathode is altered in response to detected changes in the arc voltage to return the arc voltage to substantially a preset reference value. The monitoring step and the altering step are carried out at regular preset intervals. The altering step includes deriving an filament power error signal as a prearranged function which includes the difference in values between the monitored arc voltage and the preset reference value multiplied by a predefined integral gain value.

Abstract: A high intensity discharge lamp having an inner tube in which a discharge takes place to produce visible light and ultraviolet radiation and an outer envelope which blocks harmful ultraviolet radiation. A mechanical switching element is provided to extinguish the discharge when the outer envelope is broken.

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 device having a power supply, a circuit for converting the output power from the power supply into a high-frequency power, a lighting circuit connected to a secondary side of a transformer of the high-frequency power converter circuit to light a fluorescent lamp, a circuit for preheating the filament of the fluorescent lamp, a switch circuit including diodes and at least one transistor connected in series with the fluorescent lamp in the lighting circuit, and a control circuit for turning off the transistor for a predetermined period when the power supply is turned on thereby turning off the lighting circuit to actuate the preheating circuit during this period. The control circuit turns on the transistor at the end of the predetermined period to thereby actuate the lighting circuit.

Abstract: For the magnetron in a microwave oven, a full-bridge inverter power supply 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 magnetron's thermionic cathode, and a second mode wherein both pairs of transistors self-oscillate in manner of a full-bridge inverter and then provide the magnetron's anode power as well as its cathode heating power. The first mode gets initiated immediately upon applying power to the power supply, but the second mode does not get initiated until about 5 seconds after the initiation of the first mode. That way, the cathode will have become fully thermionic prior to applying anode power to the magnetron.

Abstract: An improved power supply system of smaller size and lower cost than prior art supplies is described for starting and maintaining the running of a deuterium arc lamp at a constant current level; by use of switching circuitry with solid-state components the necessity of transformers, relays and timing circuits has been obviated with a resultant major reduction in size, cost and cooling requirements of the supply; an improved starting sequence lengthens lamp cathode life.

Abstract: An electronics circuit for improving the fault isolation of failures between an electron tube radio frequency (RF) amplifier and its high voltage power supply is disclosed. High voltage power supplies control their output voltage by comparing a feedback voltage against a reference. This comparison is used to develop an error voltage which, in turn, drives a pulsewidth modulator that corrects the feedback voltage to the reference. The output of a digital-to-analog converter (DAC) is used as the reference voltage. The DAC is driven by a counter which would count to the correct reference voltage represented by a specific count. The final count is determined by a comparator which compares the counter output to the desired final count and stops the counter when it is reached.

Abstract: A current control circuit for high voltage applications includes series-connected high and low voltage sources through which the current to be regulated flows. The low voltage source is a capacitor which is periodically recharged through a flyback transformer by a series of constant energy pulses having a very low duty cycle. The peak value of the flyback pulses are detected to provide a "condition signal" which is representative of the state-of-charge on the capacitor and can be used to protectively inhibit operation of the control circuit and can, in a variant of the circuit be used as an error control signal to maintain the current at a constant level. In the preferred embodiment a sensing capacitor is placed in parallel to the pulsed capacitor to detect the fluctuations in potential and form a sense current which is representative of the regulated current and which is used in a feedback loop to form a control signal for maintaining the regulated current constant.

Abstract: A multipulse starting aid for a high-intensity discharge lamp includes a spiral line, a bi-directional solid-state switch, or a spark gap, coupled to one of the ends of the spiral line, a resistance in association with the spiral line to provide an RC time constant. The time constant RC is so adjusted that, upon receiving the alternating current voltage from the appropriate source, a waveform of voltage is presented across the pair of terminals of the lamp, together with the series of pulses at the peak of each half cycle of the waveform. thereby enhancing the lamp startability.

Abstract: A rapid-start fluorescent lamp has a tubular envelope with a phosphor-coated inner wall, a pair of spaced electrodes and a pair of electrical leads sealed into the ends of the envelope with one electrical lead directly connected to the electrode and the other electrical lead connected through a bi-metal circuit breaker to the electrode with the circuit breaker formed to open-circuit at a given range of temperatures. Also, the discharge lamp is fabricated by preparing a phosphor coated envelope, forming a pair of end members having a pair of electrical leads, a bi-metal circuit breaker and electrode, sealing the end members into the envelope, heating and exhausting the envelope, heating the electrodes, dispensing a fill gas and mercury into the envelope, pinching off the exhaust tubes of the envelope and severing the fuse member of the circuit breaker.

Abstract: A power feed apparatus in which a means for by-passing the current reversely biasing the load is used for the normally used rectification means when the power converted by the transformer is fed to the reversely blocking characteristics like magnetron, whereby the price is lower and the shape is more compact without the use of the rectifier, because of the combination construction of the reverse bias current by-pass means and the inductance element provided in the load current path with respect to the non-linear load like the magnetron.

Abstract: A digital cathode current control circuit for controlling the cathode current of a traveling wave tube (TWT) amplifier is disclosed. The cathode current control circuit includes circuitry for providing a comparison signal indicative of the occurrence and amplitude of TWT cathode current pulses; clocking circuitry responsive to the comparison signal for providing a clock signal delayed relative the occurrence of a cathode current pulse; comparison circuitry for comparing the comparison signal with predetermined reference signals indicative of a predetermined cathode current level, and for providing adjustment signals indicative of the adjustment of the TWT cathode current necessary to tend to achieve the predetermined cathode current; and counter circuitry clocked by the delayed clock signal for providing an output count in response to the adjustment signals.

Abstract: A discharge lamp operating device having a high frequency inverter is discharged. Connected to a secondary winding of an oscillation transformer of the high frequency inverter is a discharge current supply circuit having a switch for controlling supply of a discharge current to dim a fluorescent lamp. An electrode heating circuit is connected to secondary windings of the transformer to continuously heat electrodes. An oscillation frequency of the inverter is controlled such that it increases as a dimming factor is high and decreases as the dimming factor is low. A capacitor is connected in series with a path of an electrode heating current in the electrode heating circuit so that the heating current is increased when the dimming factor is high and decreased when it is low by utilizing a frequency dependency of an impedance of the capacitor.

Abstract: A metal vapor discharge lamp has a burner for sealing xenon gas, mercury and a light-emitting additive in a translucent ceramic tube, a starting device of a thermal switch type which has a series circuit of a thermal switch and a coil filament and which is connected in parallel with the burner, and an outer envelope for sealing the burner and the starting device therein. In the lamp, the following inequalities must be satisfied:13.3.ltoreq.P.multidot.(B/A).ltoreq.6650.05.ltoreq.d.ltoreq.0.122,200.ltoreq.T.ltoreq.2,800where A is the volume (cm.sup.3) of the outer envelope, B is the volume (cm.sup.3) of the burner, P is a gas pressure (Pa) at room temperature of xenon sealed in the burner, d is a diameter (mm) of the coil filament, and T is a temperature (K) of the coil filament during operation.

Abstract: A rapid-start fluorescent lamp system includes a ballast circuit, rapid-start fluorescent lamps and power reducing means for controlling the application of energy to the lamps. The power-reducing means controls the energy to N/O switches from the energy source upon ionization of the rapid-start fluorescent lamps.

Abstract: Apparatus and method for substantially equalizing the potential drop along a line cathode used in an electron beam source adapted for use in a flat display device. The apparatus and method ensure that electrons from a power source are fed through both ends of the line cathode, substantially simultaneously. Thereby, the potential drop along the axial length of the line cathode is decreased, improving the uniformity of brightness of the display.

Abstract: A rapid-start fluorescent lamp includes a circuit breaker having a sealed glass bottle, a pair of electrical conductors sealed therein and passing therethrough and a thermally sensitive bimetal switch within the glass bottle with the bimetal switch having a pair of leg portions of unequal length.

Abstract: An electrical device for igniting and supplying a low-pressure mercury vapor discharge lamp (11) provided with two preheatable electrodes (12,13). A series arrangement (12, 4, 14, 13) comprising the two lamp electrodes (12, 13), a PTC resistor (14) and a second winding (4) of a transformer fed back negatively with respect to a first winding (3) thereof is connected to a connection point of the first transforming winding. This series arrangement (12, 4, 14, 13) is further connected to a second connection point of the first transformer winding (3). Thus, the electrical device will readily ignite and supply the lamp and will also protect the PTC resistor of the electrical device should the lamp fail to ignite even with lamp electrodes that are uninterrupted.

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: High-pressure discharge lamps generating UV radiation are provided with an internal safety switch, that interrupts the current circuit through the lamp upon fracture of the outer lamp envelope. In lamps according to the invention the safety switch is a member of a material selected from the group consisting of zirconium-aluminum alloys, sintered zirconium powder and sintered mixtures of zirconium powder and nickel powder.

Abstract: A ballast and control circuit for use with fluorescent lights. The circuit aids energy efficiency by removing heater current flow once the lamp has ignited. The circuit also uses time delayed inductive storage to allow delivery to the lamps of increased operating current without a concurrent increase in power utilization.

Abstract: A duty cycle power control circuit for a magnetron including a power transformer having a primary winding, a secondary anode winding for supplying anode voltage to the magnetron and a secondary filament winding for energizing the filament of the magnetron. In the illustrative embodiment the power transformer primary winding comprises a main winding and a serially connected standby winding. Duty cycle controlled switching devices are effective in a standby state to connect the main winding in series with the standby winding across an external power supply and are effective in the power on state to disconnect the standby winding and connect the main winding directly across the external power supply.