Abstract: A method and apparatus for transferring energy to a gas by means of a glow discharge. A transmission line is charged to a voltage of approximately twice that of the steady-state voltage of the glow discharge. A prepulse voltage source, having a higher voltage sufficient to initiate the glow discharge, is first connected to the discharge electrodes. After the discharge is initiated by the prepulse, the transmission line is connected and transfers its energy to the discharge. In a second embodiment, the transmission line is replaced by a capacitor.

Abstract: Various embodiments of direct current (D.C.) ballasting circuits for low wattage high pressure sodium (HPS) vapor lamps are disclosed. In one ballast embodiment a negative going high voltage pulse is applied directly to the H.P.S. lamp cathode during the starting operation and the ballast circuit preferentially diverts a major portion of the HPS lamp current around a high-voltage transformer during normal operation so as to reduce the resistive heating of the transformer. In a second ballast embodiment, capacitors are arranged into voltage multiplying circuit for generating the high D.C. starting voltage along with diodes that reduce the power dissipation of the ballast circuit.

Abstract: A luminous gas filled tube system has a direct current source, a pulse transformer secondary winding, the emitter-collector path of a transistor, and the gas filled tube connected in series. The voltage of the source is below the ionization potential of the gas in the tube but adequate to supply current when the gas is ionized. A pulse source is connected for selectively generating a high voltage pulse in the winding of magnitude such that, when added to the voltage from the source, the ionization potential of the gas is exceeded. A starter circuit is provided for selectively actuating the pulse source to initiate ionization of the gas in the tube. A variable resistor is provided for selecting the amount of current flowing in the series circuit at any level below a maximum rating of the transistor.

Abstract: A series controlled electronic flash of automatic emission control type includes a switching element connected in series with a commutating switching element for selectively charging a commutation capacitor. A trigger signal is repeatedly applied to a main switching element, the commutating switching element and the charging switching element in a given sequence to enable a continued emission at substantially constant brightness level to be obtained from a flash discharge tube. A trigger capacitor may be connected with pair of switching elements for charging and discharging the trigger capacitor. A trigger signal may be repeatedly applied to the pair of switching elements for charging and discharging the trigger capacitor, to the main switching element, to the commutating switching element and the commutation capacitor charging switching element in a given sequence, thereby allowing a multiple emission to be obtained intermittently and at a high rate from the flash discharge tube.

Abstract: A lamp control circuit particularly suited for scale illumination in cathode-ray tube display devices provides stabilized lamp control impervious to temperature fluctuations for either constant or pulsed operating modes.

Abstract: A low-pressure mercury vapor discharge lamp comprises a tubular bulb having an inside diameter of from 22 mm to 35 mm, an electrode-to-electrode distance of from 400 mm to 1,200 mm, and an inner surface coated with a phosphor. A rare gas including Kr and a mercury vapor source are sealed in the bulb, which is energized by an igniting device having a high-frequency power supply connected to a DC power supply for generating a substantially sinusoidal high-frequency output voltage, and a quiescent period generator connected to the high-frequency power supply and including a switch 17 turned on and off at least once during each half cycle to provide a quiescent period and thereby produce a substantially square wave high-frequency output voltage having rise and fall times of 2 .mu.s or less.

Abstract: A plurality of groups of linearly adjustable control potentiometers control respective lights of a given light scene in a given area. A particular group of potentiometers to control the scene is selected by a respective push-button switch on the control panel. Each of the potentiometer control sliders has an LED which is illuminated when its group of potentiometers is selected. Each of the control potentiometers controls a respective dimmer control circuit. Respective fader circuits are connected to each dimmer control circuit. All fader circuits are adjusted by a single potentiometer having a logarithmic response function. The single adjustment potentiometer is mounted on the control panel. All of the dimmer control circuits are remotely located from the control panel. The control panel is covered by a solid cover or a translucent cover through which only illuminated LEDs on the potentiometer sliders are visible.

Abstract: A lighting control device is incorporated in an electric bulb socket (FIG. 2) and uses a rotary switch 2 to connect a mains terminal 10 to the bulb via a direct link, a diode 6 or a triac-diac circuit 4,5 R,C.sub.2 to provide different levels of illumination.

Abstract: Protection device for electrical incandescent lamps provided with elements which upon switching on electric voltage limit the current strength during a switching-on interval. The device further includes a control unit with a controllable current valve (10) and timing means (19, 20) for the control of the current through the lamp upon switching-on so that a delayed increase of current is obtained from zero to a chosen operating current over a predetermined time interval.

Abstract: An autoconverter comprises a step-up regulating unit and following inverter so that a charging switch of the step-up regulating unit is synchronously controlled as a function of the voltage at one of the switches of the inverter. With the invention, a particularly simple synchronous control of the charging switch designed as a MOS power transistor is provided.

Abstract: A gas discharge lamp ballast circuit operates at high frequency and is fed from a mains supply through a rectifier having a smoothing capacitor. The invention provides for the load to include an inductor and to return to the rectifier supply at a position isolated from the smoothing capacitor by one or more diodes, and for there to be a discharge path from the smoothing capacitor through the load to charge a control capacitor, and lower the load voltage to allow a rectifier current flow to the load. The smoothing capacitor is charged by current flowing from the inductor during a relaxation phase, to a voltage higher than the peaks of the rectifier. The smoothing capacitor voltage is maintained by proportioning the control capacitor size to cause rectifier current, and not smoothing capacitor discharge, to supply circuit and load losses.

Abstract: Improved programming and control device for modified lead ballast for HID lamp. The basic ballast comprises a high reactive transformer and capacitor connected intermediate the transformer and lamp. An additional inductor and AC switch connect in parallel with the capacitor and the switch is opened and closed to vary the lamp current to control lamp output. The improved device comprises a parameter measuring means which measures a lamp operating parameter and converts same into output electrical signals. These signals are compared to a reference signal to generate error signals. The error signals are integrated by a capacitor and a potential which is indicative of the integrated signals is slowly developed at one capacitor terminal. A ramp capacitor is charged each half cycle of energizing potential. When the ramp capacitor potential crosses over the potential displayed at the one terminal of the integrating capacitor, a comparator means generates an output signal.

Abstract: An inverter with a dc-source has a charging condenser connected through a charging diode and a charging inductor to the dc-supply. A charging switch is periodically closed by a control component with a variable keying ratio to connect the charging inductor to the dc-supply. The inverter includes an AC voltage converter with two alternatingly controlled switches supplied with power by the charging condenser, hereinbelow identified as the primary switch and the secondary switch, which are in a series circuit in parallel with the charging condenser. In this arrangement, the control component for the charging switch of the charging regulator is synchronized with a square wave voltage at one of the switches of the alternating voltage converter. The charging switch operates at the same switching frequency as the alternating voltage converter.

Abstract: A device for illuminating the area surrounding a door lock or other relatively small area includes in a preferred embodiment a housing that is mounted on the door or other surface adjacent the area to be illuminated, the housing having a translucent portion through which an electrically energized lamp emits light. The lamp is energized by a battery connected thereto by an electronic circuit having a time-delay sub-circuit for de-energizing the lamp at the expiration of a prescribed time period. The time-delay sub-circuit further includes a means for varying the period of time that the lamp is energized.

Abstract: A circuit arrangement for operating a high-pressure gas discharge lamp (14) with high frequency current in which a direct voltage is supplied to a transistor bridge (5 to 8) having a transverse branch in which is arranged a choke coil (13). The clock (switching) frequency of the transistor bridge is varied within each period of the AC mains alternating voltage in dependence upon the current derived from the AC mains voltage.

Abstract: A switching transistor (5) has its collector connected to a common junction (J) with a load (6), typically an ignition coil (8). A first driver transistor (11) connected through the base-emitter path of a second driver transistor (12) to control the conduction state of the switching transistor. A signal source (20, 21) alternatingly, causing the driver transistor to be blocked or conductive.

Abstract: Intensity regulator, especially a light regulator which can be adapted to the regulation of the light intensity of both compensated and uncompensated illuminators connected to the alternating-current mains. The regulator comprises one or more switch elements (S1, S2) disposed in a circuit between the mains and an illuminator (L) as well as a control logic circuit (4) for the switch element or elements, said circuit upon the intensity regulation breaking the supply current at least once on each half-cycle when current has been conducted from the O-moment of a half-cycle to the moment according to a set value. On one hand, a problem is the elimination of current peaks produced by voltage differences at a switch-on moment and, on the other hand, the arrangement of a control for the switch elements.

Abstract: A ballast circuit for direct current gaseous electrical discharge devices includes a rectifying bridge, and an inductive ballast for storing excess energy. The rectifying bridge uses a pair of thyristors which must be gated on for the bridge to supply rectified voltage to the inductor and device. Gating is delayed at the beginning of each half-cycle to allow the inductor to discharge most of its stored energy.

Abstract: An electronic ballast circuit for operating high intensity gas discharge tubes such as high pressure sodium, high pressure mercury and metal halide tubes, as well as ordinary fluorescent tubes. In the preferred embodiment, an inductance and a capacitance are connected in series with the load across the dc supply, with a solid state switch between the junction of the inductance and capacitance and the other side of the load, and a control circuit for the switch to operate the switch at a high frequency such as 20,000 hertz. Alternative embodiments omitting the capacitance and utilizing a transformer for the inductance are especially suited for less expensive units and for emergency lighting use. Power supply circuits with switching operated in conjunction with the previously mentioned switch provide for regulation of lamp output during start-up and for compensating changes in supply voltage coordinated with lamp aging.

Abstract: Three-transistor, four-terminal precision current source is switchable. Current is passed between two of the terminals in the presence of a switching signal on another terminal. While switched on, the current is regulated according to a reference voltage supplied to the remaining terminal.

Abstract: A circuit arrangement for different color light emission, comprises first series circuit of a first light-emitting element having a given color, a diode, and a resistor; and a second series circuit of a second light-emitting element having another color and a collector-emitter path of a transistor, where the transistor is responsive to an input control signal so as to change a current flowing therethrough. The first and second series circuits are connected in parallel and are interposed between two terminals of a power source. The impedance of the first series circuit is selected to be much greater than that of the second series circuit when the transistor is conductive. When the voltage of the input control signal is below a predetermined level, the transistor is kept nonconductive so that only the first light-emitting element is energized.

Abstract: Incandescent lamp driver circuit with current surge limiting and built-in test features.

Abstract: An electronic drive system for a discharge lamp is disclosed wherein the switching frequency of the chopper is reduced until the lamp striking voltage has reached about 70% of its rated value. The system includes a chopper transistor, a control for varying the transistors duty cycle and a smoothing inductance, freewheeling diode and smoothing inductor to smooth the chopper output. Current limiting is provided to prevent overcurrent within the chopper transistor, smoothing inductor or lamp.

Abstract: A method and circuit for operating an incandescent lamp are disclosed in which the operating voltage applied to the lamp alternates in a regular and abrupt manner between forward and reverse polarities. The magnitude of the voltage is substantially the same for the two polarities and, therefore, the luminosity of the lamp is substantially constant. However, lamp life is increased as compared to standard DC operation since the alternating polarity of the operating voltage reduces the rate at which the lamp fails due to lamp filament breakage.

Abstract: A flashlamp drive circuit 10 using an unsaturated transistor Q1 as a current mode switch to periodically subject a partially ionized gaseous laser excitation flashlamp 20 to a stable, rectangular pulse of current from an incomplete discharge of an energy storage capacitor C1. A monostable multivibrator MV1 sets the pulse interval, initiating the pulse in response to a flash command by providing a reference voltage to a non-inverting terminal of a base drive amplifier AV1; a tap on an emitter resistor R2 provides a feedback signal sensitive to the current amplitude to an inverting terminal of amplifier AV1, thereby controlling the pulse amplitude. The circuit drives flashlamp 20 to provide a square-wave current flashlamp discharge.

Abstract: A time-variable illumination control apparatus for a lamp permits light intensity to be gradually increased starting at a predetermined time. The intensity control includes a clock-timer to initiate time-variable power supply network. The illumination control apparatus is designed for use on mornings when a user would commonly arise before daylight. By setting the illumination control apparatus to gradually increase the light intensity of a lamp prior to awakening, the lamp simulates sunrise so that the eyes gradually adjust to the light while sleeping. Upon awakening, the eyes are fully adjusted to the light and eye discomfiture from a sudden increase in intensity is avoided.

Abstract: A frequency responsive power control system includes an improved isolator in series electrical connection with respect to a ballasted lamp load. The isolator has a high inductive impedance at low current for blocking ballast induced noise signals from interferring with proper operation of frequency responsive switching circuits in the system. In a particularly useful embodiment, the isolator is inductively matched to the capacitive characteristic of the ballasted lamp load so that the isolator-load circuit combination is resonant at a frequency sufficiently removed from any of the control system activation frequencies so as to block any noise signals induced by the ballasted load which might otherwise cause undesired activation of the switching circuits and flickering of the ballasted lamp loads. Under saturation current, with the switching circuit conducting, the isolator functions collectively with the load to provide an impedance which blocks control signals from reaching the load.

Abstract: A fluorescent lamp is adjusted in illumination intensity by controlling the DC current in the lamp during each alternate direct current flow through the lamp. The magnitude of the current applied to the lamp is set each time the direction of current through the lamp is switched, and the current change between switch times is limited. Inductors are used as current change limiting devices so that in each direction of current flow through the lamp, the current can not rapidly change. The amount of current is set, and the direction of current flow is switched when a current monitor detects that the current through one of the inductors is equal to the current desired for the operating point of the lamp. In this way, uniform selectable illumination levels may be achieved even though the lamp is operating in the negative resistance portion of its resistance characteristic.

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: A light regulation system is provided wherein the light output of a fluorescent lamp(s) is regulated in accordance with the RMS value of the lamp arc current which is automatically adjusted to maintain a referenced ambient light level or arc current. The ballast and associated lamps of the system receive the full line voltage until the lamps are ignited and thereafter the current thereto is automatically limited by limiting the amplitude of the ballast current during the part of each AC voltage half wave that the lamps are ignited. Control between the minimum light level, wherein a minimum arc current flows during each half cycle, to the maximum light level is accomplished by permitting the minimum arc current which flows during the "lamps on" period of each half wave to increase to maximum arc current over a part or all of the period of each half wave that the lamps are on.

Abstract: Lamp modulating circuitry particularly useful for flashing fluorescent lamps in response to music or other audio signals employs an input filter to screen out signals having frequencies less than 20 hertz or greater than 200 hertz. An amplitude demodulator detects the peak amplitude of signals received from the input filter and develops a signal representing the envelope of the low audio frequencies. An automatic gain control compares the instantaneous and average signals derived from the amplitude demodulator and develops an average signal using an output filter. Signals transmitted past the output filter are used by lamp flashing circuitry to cause the output of a fluorescent lamp to be modulated.

Abstract: A circuit arrangement for starting and operating a discharge lamp by means of an electronic ballast includes a series arrangement of a PTC resistor and an ohmic resistor connected in parallel with an electronic switch of the ballast, with only the PTC resistor being in parallel with a control circuit of the electronic switch. The value of the ohmic resistor is 8 to 12 times the cold resistance of the PTC resistor.

Abstract: A solid-state electronic ballast circuit for supplying direct-current power to an electric discharge vapor lamp is disclosed. The source-drain channel of a Vertical Metal Oxide Semiconductor (VMOS) Field Effect Transistor (FET) is connected in parallel with a fixed ballast resistor, the parallel combination being connected in series with the lamp across a DC source. A resistance network controls the conductivity of a bipolar transistor, which in turn controls the conductivity of the VMOS channel, in response to variations in both lamp voltage and current. The ballast circuit may be manufactured as a part of the lamp bulb assembly, the ballast resistor taking the form of an incandescent lamp filament mounted in the same outer bulb with the vapor lamp arc tube. A variable resistance may be employed to manually adjust the level of illumination delivered by the lamp, or a light-sensitive phototransistor may be employed to deliver constant illumination.

Abstract: A light dimming system for simultaneously controlling the brightness of a plurality of two-terminal indicating lights, each having one terminal connected to receive a constant voltage relative to ground. The system includes a single dimmer control for producing an arbitrarily variable control voltage, and a like plurality of interface circuits, connected between the dimmer control and the other terminals of the indicating lights, respectively, for varying the voltage at the other terminals of the indicating lights proportional to the control voltage supplied to the interface circuits from the dimmer control.

Abstract: The present invention relates to power supplies, and more particularly, to a power supply which is particularly suitable for controlling a high intensity discharge (HID) lamp. In particular, the present invention relates to an HID lamp power supply which provides fast warm up for a cold lamp, regulation against line voltage fluctuations and a lamp starting circuit which provides extremely fast restart when the lamp is hot and has been turned off momentarily.

Abstract: An electrical energy conservation control method and apparatus are provided which produce efficient control of the light output of either incandescent or fluorescent lamps or the outputs of other electrical load devices under circumstances where the rated output is not required. The control method and apparatus combines electronic (transistor) switching techniques with the use of reactive circuit components to provide control of the magnitude of current flowing through the load device during the AC input voltage sine wave and to permit some current flow at all times during each voltage half wave. The control technique is non-dissipative in the sense that losses are virtually limited to switching transitions and passive circuit element losses. The control is accomplished by controlling the time period that a transistor is saturated full-on.

Abstract: The input energy to a gas discharge lamp is controlled over a given range to obtain output light regulation in a controlled fashion for different kinds of gas discharge lamps, including fluorescent lamps, high intensity discharge lamps and others associated with any type ballast, including conventional non-dimming type ballasts. A suitable circuit switches each half wave of an input a-c wave form from some instantaneous value greater than zero to a substantially zero value and then back to a value greater than zero one or more times in each half cycle. The time duration of the substantially zero energy interval is varied to vary the total energy applied to the gas discharge lamps. In a preferred embodiment, a first high speed electronic switch is connected in series with the a-c source and lamp ballast and a high speed electronic shunt switch is connected across the a-c line and ballast input. The series switch is opened to produce the zero energy interval.

Abstract: A preset lighting device in which the number of common input and output terminals is reduced and which does not respond to a duplicate switch activation state so that a previously-determined lighting state as maintained until a valid activation state is present. A lighting element is provided for each of plural input switches which are in turn coupled to corresponding input/output terminals. A latch circuit is provided for each lighting element to maintain the lighted state until reset occurs. First and second gate circuits detect a duplicate switching state and control the activation of the lighting elements accordingly.

Abstract: A dimmer suitable for use to control the intensity of illumination of a lamp or lamps for illuminating an instrument panel provided in a compartment of a vehicle such as a motor car, comprises: a dimming transistor connected to a lamp or lamps to be dimmed for controlling an electric current supplied to said lamp or lamps, a switching circuit connected to said dimming transistor for generating pulses having a controllable duty ratio to cause said dimming transistor to turn `ON` on `OFF`, surge voltage sensing means for sensing a surge voltage applied to an electric source line, and transistor shutoff means for shutting off said dimming transistor in response to a signal from said surge voltage sensing means.

Abstract: The invention relates to a mixed light lamp arrangement intended to be connected to an a.c. power supply. The lamp arrangement comprises a rectifier bridge having output terminals interconnected by the mixed light combination consisting of a series arrangement of an incandescent filament and a discharge tube. The series arrangement is shunted by a branch comprising a capacitor and an anti-parallel arrangement of a diode and a thyristor with the thyristor being rendered conductive just prior to the end of each half cycle of the a.c. power supply. This results in a mixed light lamp wherein the capacitance of the capacitor can have a relatively low value and the luminous efficacy can be relatively high.

Abstract: An electric flash discharge device comprises a capacitor charged by a power source, a trigger device including an operating member for producing a trigger signal in response to the actuation of the operating member, and a discharge tube connected to the capacitor and trigger device so as to be triggered in response to the trigger signal to form a discharge circuit for the capacitor. A control signal generator is provided for providing a control signal in response to generation of the trigger signal, and a current control means is connected between the capacitor and the discharge tube for controlling, in response to the control signal, the discharge current flowing through the discharge tube so that the discharge current gradually increases from a low value to a peak value after initiation of the discharge as a function of the control signal.

Abstract: A bank of high power quartz iodine lamps is regulated so that changes in light output from the lamps for a 40 volt change in AC line voltage is reduced from 132% to 10%. To accomplish this, a regulating pulse width modulator is synchronized to the AC line so that pulse width modulated pulses are developed the trailing edge of which is coincident with the zero crossover points of the AC line voltage. The variable leading edge of these width modulated pulses is employed to control the firing point of semiconductor switching devices in series with the lamps, the average voltage across the lamps being sensed and employed by the regulating pulse width modulator to vary the width of the pulses in the correct direction to maintain the lamp voltage constant despite large changes in line voltage.

Abstract: A power source circuit for a flash discharge lamp which includes a booster-rectifier, a thyristor connected to the booster-rectifier on the side of a power source, a discharge capacitor connected to the booster-rectifier on the side of a load, a detecting element for detecting a voltage across the discharge capacitor, a trigger circuit and a control circuit. The control circuit is adapted to supply, to the gate of the thyristor, an AC signal of substantially the same phase as the power source and to stop the AC signal supply when the voltage of the discharge capacitor reaches a predetermined value, thereby preventing the thyristor from noise generation which would otherwise cause a malfunction in a computer which processes facsimile or like picture signals.

Abstract: A traffic light control circuit of the type utilizing solid state thyristor switches with their control terminals driven by a diode bridge trigger network that includes switches for selectively interrupting one or both legs of the trigger network for energizing the traffic lights with either full wave power for normal daytime operation or half-wave power for night time operation at reduced brightness, thereby providing power savings for night time operation.

Abstract: Discharge lamp energization circuit to operate a discharge lamp 1 over two electronic switches 10, 11, for example high-voltage, high-current switching transistors, which alternately apply a d-c voltage connected across two capacitors 4, 5, in opposite polarity, to the lamp circuit. The capacitors have the same value, and the lamp circuit includes a serially connected inductance. The electronic switching transistors are supplied from a frequency constant square-wave generator 16, at frequency high with respect to power line frequency, for example within the audio or supersonic range, e.g. 7.5 kHz. A separate ignition or starting circuit may be provided or the series inductance 2 and a capacitor 20 connected in parallel with the lamp may form a series resonance circuit tuned to a low odd harmonic (3, 5 7) of the lamp operating frequency.

Abstract: A circuit for supplying controlled direct current power to an electric discharge vapor lamp during ignition, warm-up and normal operation. A bridge rectifier and a capacitor voltage doubler convert standard alternating current line voltage into a direct current voltage of adequate magnitude to operate the lamp. The lamp is connected in series with a semiconductor control circuit across the DC supply. The semiconductor control circuit operates as a resistive ballast whose effective resistance decreases as vapor pressure within the lamp increases during warm-up, thereby limiting lamp current to a safe value immediately after ignition while reducing the amount of power dissipated in the ballast circuit during normal operation for improved efficiency. In a second embodiment, the conductivity of the resistive ballast circuit is controlled in response to variations in both lamp voltage and lamp current to control the amount of power delivered to the lamp.

Abstract: The present invention relates to a lighting unit utilizing an energy efficient arc lamp as the main source of light supplemented by a standby filamentary lamp, the filament serving as a resistive ballast for the arc lamp during normal operation. The lighting unit is designed for functional similarity to an incandescent lamp, the filament providing immediate illumination when the lighting unit is first energized and continuing illumination until the arc lamp itself produces light. In accordance with the invention, if the arc lamp does not start within a predetermined period, the application of starting potentials produced through operation of a solid state switch and a high frequency step-up transformer is discontinued and the lighting unit rendered inactive. Exemplary means includes a positive temperature coefficient thermistor responsive to the temperature rise of the solid state switch.

Abstract: Power supply means for a laser flashtube or similar lamp (such as a continuous wave arc lamp) consists of high frequency switch means for providing a pulse train output from a direct current supply with provision for modulating the pulse width of said output and a filter which receives the modulated pulse train output for substantially removing high frequency ripple therefrom prior to passage of the resulting pulse train output to the flashtube or similar lamp. For supplying a simmer current to the flashtube or lamp the modulated pulse train output may be raised to a DC level for this purpose. The high frequency switch means may consist of at least one transistor or thyristor and the filter may consist of an inductor/capacitor arrangement.

Abstract: The emitted light intensity of an electronic flash tube is maintained constant over a given time period by connecting the electronic flash tube in series with an inductor and a switching element across the main capacitor for energizing the flash tube, with a diode being connected across the serially connected flash tube and inductor and a polarity opposite to the current flow from the main capacitor to the flash tube. The switching element is intermittently turned off and on in accordance with the intensity of the light emitted from the flash tube. While the switching element is being turned off, the flash tube is energized by the energy stored in the inductor in the form of a magnetic field. An auxiliary capacitor may be provided across the flash tube. The flash light intensity may be monitored by the measurement of the emitted light, or by the detection of the voltage across the flash tube, or by the detection of the current flowing into the flash tube.

Abstract: A gas discharge lamp is connected across an inductor and in series with a solid state switching device and a resistor, and this combination is connected across a rectified AC voltage source. This switching device is controlled by a monostabile multivibrator, the input of which is connected to the output of a comparator amplifier sensing the difference between the voltage drop across the above-mentioned resistor and a voltage which may be selected to vary light intensity. The secondary winding of a step-up transformer connected to a capacitive discharge device is placed in series with the lamp. Control circuitry is provided to apply a large ignition voltage to the lamp while preventing damage to the switching device by simultaneously holding it in its conductive state. A diode rectifier provides an alternate current path across the secondary winding to prevent the inductance of the secondary winding from affecting normal lamp operation.