Abstract: The present invention relates to a system and a method for high-voltage switching for a computed tomography apparatus. The system comprises an oscillating circuit with a non-linear inductor and a capacitor. The inductor and the capacitor are connected in series, and the capacitor is connected to a high-voltage line of a high-voltage power supply. The inductor comprises an inductance that decreases with increasing current through the inductor, such that the inductance of the inductor significantly chances during a resonant operation of the oscillating circuit, thereby providing essentially a square voltage applied to the capacitor. The square voltage modulates the high-voltage of the high-voltage generator thus switching high-voltage levels applied to an electrode of a computed tomography system.

Abstract: A system including a vehicle having a motive electrical power path; a power distribution unit including a current protection circuit disposed in the motive electrical power path, the current protection circuit including a breaker/relay, the breaker/relay including: a fixed contact, a moveable contact, and a physical opening response portion responsive to a current value; a current source circuit electrically coupled to the breaker/relay and structured to inject a current across the fixed contact; and a voltage determination circuit electrically coupled to the breaker/relay and structured to determine at least one of an injected voltage amount and a contactor impedance value, wherein the voltage determination circuit comprises an analog hardware filter having a cutoff frequency selected in response to a frequency of the injected current.

Abstract: UV hard-surface disinfection system that is able to disinfect the hard surfaces in a room, while minimizing missed areas due to shadows by providing multiple UV light towers that can be placed in several areas of a room such that shadowed areas are eliminated and that can be transported by a cart that is low to the ground such that the towers may be loaded and unloaded easily by a single operator. The system is able to be controlled remotely, such that during activation of the system, no operator is present, and to automatically cut power to all towers in the event that a person enters the room.

Abstract: Various techniques are provided for implementing a lighting device variable control using a variable inductor. In various examples, the variable control may be implemented with a plurality of continuous or stepped settings. The variable control may be adjusted by a user-actuated movement of a part of the lighting device, such as the depression of a tail cap or another appropriate physical control to change the inductance of the variable inductor. An oscillating signal may be induced in a variable inductor circuit that includes the variable inductor. The oscillating signal may exhibit characteristics, such as frequency, that change with the inductance of the variable inductor. Such characteristics may be measured to determine a setting of the variable control and which may be used to adjust the brightness or other attributes of the lighting device.

Abstract: Systems and methods for measuring ambient and laser temperature in heat assisted magnetic recording (HAMR) systems are provided. One such system includes a slider having a write head, a laser diode coupled to the slider and configured to direct energy to a magnetic medium, and a preamplifier circuit including a voltage measurement circuit configured to measure a voltage drop across the laser diode, and a current measurement circuit configured to measure a current through the laser diode, where the preamplifier circuit is configured to store calibration information including a plurality of temperatures corresponding with measurements of the voltage drop across the laser diode and measurements of the current through the laser diode, and calculate a temperature based on the measured voltage drop across the laser diode, the measured current through the laser diode, and the calibration information.

Abstract: An LED driver system including an input receiving a rectified AC conductive angle modulated voltage on a rectified node, a converter, a low-pass filter, and AC detector, and a driver network. The converter is coupled to the rectified node and includes a power switching device coupled to a switching node, in which the power switching device is controlled to convert the rectified AC conductive angle modulated voltage to an output voltage and output current. The low-pass filter is configured to filter voltage of the switching node to provide a filtered voltage. The AC detector receives the filtered voltage and provides a current sense signal indicative thereof. The driver network controls duty cycle of the power switching device based on the current sense signal.

Abstract: The present invention includes a first DC converter converting AC voltage, into DC voltage while correcting a power factor, and a second DC converter electrically isolating the first DC converter from an LED group load, and converting the DC voltage, into a predetermined DC voltage and supply the resultant voltage to the LED group load. The second DC converter includes a current detection circuit disposed on the secondary side, and detecting current flowing into the LED group load, an error amplifier amplifying an error between a detected current value detected and a reference current value, a signal transmission isolation element transmitting a control signal based on an output signal from the error amplifier, to the primary side, and a switching element transferring power to the secondary side through the transformer by being turned on/off according to the control signal.

Abstract: The present invention includes a first DC converter converting AC voltage, into DC voltage while correcting a power factor, and a second DC converter electrically isolating the first DC converter from an LED group load, and converting the DC voltage, into a predetermined DC voltage and supply the resultant voltage to the LED group load. The second DC converter includes a current detection circuit disposed on the secondary side, and detecting current flowing into the LED group load, an error amplifier amplifying an error between a detected current value detected and a reference current value, a signal transmission isolation element transmitting a control signal based on an output signal from the error amplifier, to the primary side, and a switching element transferring power to the secondary side through the transformer by being turned on/off according to the control signal.

Abstract: A plasma lamp apparatus includes a post structure with a material overlying a surface region of the post structure, which has a first end and a second end. The apparatus also has a helical coil structure configured along the post structure. The apparatus includes a bulb with a fill material capable of emitting electromagnetic radiation. A resonator coupling element configured to feed radio frequency energy to at least the helical coil causes the bulb device to emit electromagnetic radiation.

Abstract: The present invention includes a first DC converter converting AC voltage, into DC voltage while correcting a power factor, and a second DC converter electrically isolating the first DC converter from an LED group load, and converting the DC voltage, into a predetermined DC voltage and supply the resultant voltage to the LED group load. The second DC converter includes a current detection circuit disposed on the secondary side, and detecting current flowing into the LED group load, an error amplifier amplifying an error between a detected current value detected and a reference current value, a signal transmission isolation element transmitting a control signal based on an output signal from the error amplifier, to the primary side, and a switching element transferring power to the secondary side through the transformer by being turned on/off according to the control signal.

Abstract: A projection device includes: a projector unit that has at least a light source and a projection optical system housed in a chassis; a control unit that is assembled with a chassis separate from the chassis of the projector unit; and a rotation support member that rotatably supports the projector unit and the control unit around a rotation axis that extends perpendicular to a surface of the chassis of the projector unit and a surface of the chassis of the control unit, with these surfaces facing to one another.

Abstract: In an instant start ballast, dimming control is provided over a range of operation in which lamps driven by the ballast do not require external cathode heating. An interface circuit (92) includes a winding (90) that is inductively coupled to windings (68, 70) of an inverter circuit (12). The interface circuit (92) also includes a variable impedance in parallel with the winding (90) where the variable impedance includes a transistor (96) and a Zener diode (98). By varying an input voltage across control leads (94), the apparent inductance of the winding (90) is varied. This variance affects the switching frequency of the inverter circuit (12) affecting the frequency of a drive signal provided to the lamps. Thus the instant start ballast can be dimmed without use of multiple ballasts and/or external cathode heating.

Abstract: Methods and apparatus for powering a dimmable ballast operating a gas-discharge bulb in a cold cathode mode of operation, that is, without requiring heating of filaments. The ballast circuit includes a rectifier, bypass capacitor, driver circuit, and a tank circuit that includes a resonant circuit that are configured to ionize a light source, such as a fluorescent lamp, every half cycle of the input voltage. The bypass capacitor supplies energy to produce a high frequency current introduced into the resonant circuit to continually recycle energy in the resonant circuit, resulting in a ballast with a high power factor. A tank circuit comprising a tapped inductor operating in a non-saturated or limited saturated mode provides additional voltage to the bulb to ionize the bulb. The ballast may be dimmed and combined with other energy savings circuitry.

Abstract: In an instant start ballast, dimming control is provided over a range of operation in which lamps driven by the ballast do not require external cathode heating. An interface circuit (92) includes a winding (90) that is inductively coupled to windings (68, 70) of an inverter circuit (12). The interface circuit (92) also includes a variable impedance in parallel with the winding (90) where the variable impedance includes a transistor (96) and a Zener diode (98). By varying an input voltage across control leads (94), the apparent inductance of the winding (90) is varied. This variance affects the switching frequency of the inverter circuit (12) affecting the frequency of a drive signal provided to the lamps. Thus the instant start ballast can be dimmed without use of multiple ballasts and/or external cathode heating.

Abstract: To dim a high intensity gas discharge (HID) lamp an inductance is connected in series with said HID lamp. The inductance functions as a ballast. The HID lamp is supplied by a frequency adjustable AC voltage supply. Since the impedance of the inductance is dependent on the frequency of the supply voltage, the current through the inductance is dependent on said frequency. Thus, the lamp current may be controlled by changing the frequency of the supply voltage, while the voltage is kept high kept high to prevent the lamp from extinguishing. The method and circuit of the present invention are suitable for driving a number of HID lamps simultaneously. Further, the HID lamp may be dimmed to about 20% of its nominal power, depending on the type of HID lamp. Dimming may be performed substantially instantly without extinction of the lamp.

Abstract: A plurality of cold cathode fluorescent lamps (CCFLs) for a backlight of a display device are connected, each in series with a respective variable inductance, in parallel to an AC supply from a power converter. Each variable inductor comprises a first inductor in series with the CCFL, a second inductor inductively coupled to the first inductor, and an AC switch for selectively shorting the second inductor. A capacitor in parallel with the first inductor forms a resonant circuit tuned to the AC supply frequency when the switch is open. Each switch is opened and closed with a controlled duty cycle to provide individual control of an average current of each CCFL.

Abstract: A plasma-generation power-supply device includes a transformer connected to an alternating-current power-supply, a rectifier connected to the transformer, an inverter connected to the rectifier, a reactor inserted in series in a power line of an ozonizer that is supplied with power from the inverter, and a controller that controls the inverter. The controller detects the current flowing to the ozonizer with a current detector and provides a control that keeps power applied to the ozonizer constant.

Abstract: An electronic ballast operates a gaseous discharge lamp. The electronic ballast includes a filter circuit for removing noise from an electrical power signal. The power factor of the filtered power signal is adjusted by a power factor correction circuit. The power factor correction circuit includes a programmable inductor circuit having a plurality of selectable inductance values for varying the amount of power factor adjustment to accommodate operation of different lamp types and/or different lamp wattages. A power supply circuit converts electrical power received from the filtered power signal to provide low level power for operating the electronic ballast. An output circuit receives the corrected power signal produced by the power factor correction circuit and produces an electrical signal to ignite and operate the discharge lamp.

Abstract: The invention improves an operating method, already described in the prior application 198 39 329.6, for a silent discharge lamp L, in which, using the forward transformer principle, a voltage pulse effecting a forward ignition is impressed from a primary circuit P via a transformer T into a secondary circuit S containing the silent discharge lamp L, and the secondary circuit S thereafter executes a half wave which, as a consequence of the polarization, leads to a back ignition in the discharge lamp L. The improvement consists essentially in that an inductance of the transformer T which governs a transformer current is temporally varied.

Abstract: Ballast circuitry is provided for powering a gaseous discharge lamp which has a range of possible parasitic loading capacitances associated with it. The circuitry includes a reactive source of ignition pulses which stores sufficient energy to charge the highest value of parasitic loading capacitance in the range to at least the minimum ignition voltage of the lamp. A voltage clamping element limits the peak voltage of the ignition pulses, even at the lowest value of parasitic loading capacitance in the range, to a maximum permissible voltage that may be applied to the lamp. The reactive source and the voltage clamping element cooperate to automatically provide high-energy ignition pulses to the lamp, with peak voltages well within permissible limits, over the entire range of parasitic loading capacitances.

Abstract: In an electronic ballast, a rapid start fluorescent lamp is powered by being parallel-connected with the tank-capacitor of a series-resonant LC circuit. Beating power for the lamp's cathodes is obtained by way of loosely-coupled auxiliary windings on the tank inductor of the LC circuit. In case the fluorescent lamp were to be disconnected or otherwise were to fail to properly load the series-resonant LC circuit, due to so-called Q-multiplication, the magnitude of the voltage develped across the tank-capacitor would normally increase to a high and potentially destructive level. However, due to feedback operable to cause the inverter frequency to increase as a function of the magnitude of the voltage across the tank-capacitor, the magnitude of this tank-capacitor voltage is limited to a level substantially lower than what otherwise would be the case.

Abstract: A drive circuit arrangement for a gas discharge lamp includes a) a self resonating inverting for providing a drive voltage across a load impedance, the inverter having a pair of field effect transistors which operate in anti-phase, b) a tank circuit for canceling the reactive component of the load impedance coupled to the inverter, c) a voltage division circuit which provides a given fraction of the drive voltage to the gates of the field effect transistors, and d) a phase shifting means comprising an inductance in series with the tank circuit for shifting the phase of the given fraction of the drive voltage. The voltage division circuit is provided with a voltage limiter which in operation provides a further phase shift to the given fraction of the drive voltage when the drive voltage exceeds a given threshold value, increasing the resonant frequency of the inverter and limiting the peak drive voltage.

Abstract: To provide for automatic switch-over between a power phase and a holding se in operation of a discharge lamp (EL), a choke or ballast coil (L), serially connected to the discharge lamp, is constructed to have, with respect to current flow therethrough, a non-linear reactance value; the choke or ballast coil is wound on a core which, for example, can be a E-core in which the center leg is of reduced cross-section with respect to the outer legs; or, if one is a torroidal coil on a ring core, the ring core is preferably made of two core elements of different magnetic characteristics, connected together, for example by an adhesive, in which one core element is of low permeability material, such as iron powder or permaloy with high saturation magnetization, and a second core is formed of ferrite with low saturation magnetization.

Abstract: An apparatus for applying a variable voltage to an electric load utilizes a transformer with several taps to provide different voltage levels for the load. The load is connected to alternate taps by a switching device, which is operated by a control device responsive to short interruptions in the power supply to the load. Short interruptions in power can be generated by rapidly turning one or more existing power switches in circuit with the load off and on again, so remote control is possible from several locations. Apparatus with the above structure is particularly suitable while employing a toroidal transformer for dimmer control of halogen lamps.

Abstract: In a fluorescent lamp ballast, a high-frequency AC voltage is applied directly across a tuned L-C circuit. The fluorescent lamp is connected in parallel with the capacitor of the L-C circuit and a voltage-limiting means prevents the series-resonating L-C circuit from overloading the source of AC voltage during any period when the lamp is not effective in providing circuit loading. When power is initially applied to the L-C circuit, a control means provides a short circuit across the capacitor; and, by way of a first current transformer, the resulting short circuit current is used for pre-heating the fluorescent lamp cathodes. After about 1.5 second, the control means provides for removal of the short circuit for a period of about 25 milli-seconds, thereby permitting the voltage across the capacitor to grow to a magnitude sufficient to ignite and operate the lamp, while at the same time removing the cathode voltage.

Abstract: A device for regulating the intensity of light emitted by a lamp includes a core of magnetic material, a first electrical circuit having a primary inductor wrapped around at least a portion of the core of magnetic material, and a second electrical circuit having a secondary inductor wrapped around at least a portion of the core of magnetic material. The first electrical circuit is designed for electrical connection to the lamp, and the primary inductor is arranged in the first electrical circuit in a manner such that a variation in the inductance of the primary inductor will cause a corresponding variation in the intensity of light emitted by the lamp. The second electrical circuit includes a control device (e.g.

Abstract: The invention relates to an inverter powering a lamp that uses a switch to vary the resonance of the resonance circuit for starting and for operating.

Abstract: A device for regulating the intensity of light emitted by a lamp includes a variable inductor configured to surround a portion of the lamp and electrical circuitry arranged to connect electrically the variable inductor to the lamp in a manner such that a variation in the inductance of the variable inductor will cause a corresponding variation in the intensity of light emitted by the lamp while the lamp is electrically connected to the variable inductor.

Abstract: This reactor ballast is used for controlling a lamp and comprises a core and winding connected in circuit with the lamp and inductively coupled to the core for developing a magnetic field in the core when the winding is traversed by electric current. The core forms a magnetic circuit for the magnetic field comprising two parts in series with each other in the magnetic circuit, one part being of metallic magnetic material and the other being of ferrite material. A control arrangement is provided for varying the temperature of at least a portion of the ferrite part in a predetermined temperature range just below the Curie point of the ferrite material where its relative permeability decreases steeply in response to small temperature increases.

Abstract: A control circuit is disclosed that can be used to control the light intensity of a fluorescent lamp. A first embodiment of the control circuit includes one variable inductor and a plurality of fixed inductors. A switch is used to connect one of the inductors to the fluorescent lamp in parallel. The intensity of the light output from the lamp is varied either by adjusting the inductance of the variable inductor, or by switching between the fixed inductors. A second embodiment uses a variable capacitor in place of the variable inductor and uses fixed capacitors in place of the fixed inductors.

Abstract: A dual feedback control system for a Class-D power circuit maximizes efficiency by controlling the magnitude and phase angle of the resonant load circuit using two separate feedback loops. The first feedback loop changes the value of a first variable capacitor in response to difference in magnitude between the actual load impedance and the desired load impedance. The second feedback loop changes the value of a second variable capacitor in response to the phase difference between the actual phase angle and the desired phase angle. In this way, the real and imaginary components of the load impedance are controlled so that the Class-D circuit is in tune, and hence efficiency is maximized, over a wide range of load impedances. The dual feedback control of the present invention may be advantageously employed in the ballast of an electrodeless HID lamp system.

Abstract: In one aspect of the present invention a capacitor is placed in series with the ballast and the lamp. The capacitor lowers the impedance during lamp starting and is shorted out when final arc conditions of the lamp are reached. Method and device for improvement of lumen maintenance of high intensity discharge lamps through minimizing the wall blackening during lamp starting is disclosed. Reducing the electrode material sputtering during the thermionic arc phase of the lamp starting process was achieved by decreasing the cathode fall voltage. The cathode fall voltage in these lamps was decreased by increasing the current flowing through during the starting phase. The increase of starting current was achieved by increasing the open circuit voltage or by decreasing ballast impedance.

Abstract: A closed-loop control system for a Class-D power amplifier circuit, having a variable output resonant circuit impedance, maintains high-efficiency operation by using the phase angle between the resonant load voltage and current to control tuning of the resonant circuit. The resonant load circuit voltage and current are supplied to a phase detector for detecting the phase angle therebetween and for generating a voltage proportional thereto. The output voltage from the phase detector is compared to a reference voltage by an error amplifier. The resulting error voltage is employed as the input signal to control circuitry for tuning the output resonant circuit. Such a control system is suitable for maintaining high-efficiency operation of an electrodeless high intensity discharge lamp system.

Abstract: A power supply circuit for an electric discharge lamp driven by an A.C. power supply has a regulating transformer connected in parallel with a current limiting reactor and an electric discharge lamp interconnected in series. The tap of the regulating transformer is connected by a condenser and an auxiliary reactance interconnected in series to the connection between the current limiting reactor and the electric discharge lamp. By adjusting the tap of the regulating transformer the performance of the lamp can be influenced within a wide range. In place of the regulating transformer an electronic phase shifter may also be used, which is particularly advantageous when regulating speeds are required that cannot be achieved by means of an electromechanically adjustable regulating transformer.

Abstract: A fluorescent lamp ballast comprises a self-oscillating inverter with saturable transformer means in its positive feedback circuit. The saturation flux density of the magnetic material used in this saturable transformer means determines the frequency of inverter oscillation. A permanent magnet is rotatably mounted adjacent the saturable transformer means and is used by way of cross-magnetization to adjustably affect the saturation flux density of the magnetic material, thereby correspondingly to adjust the frequency of oscillation: the more cross-magnetizing flux provided to the magnetic material from the permanent magnet, the smaller the saturation flux density and the higher the frequency of oscillation.Current for the fluorescent lamp is attained from the inverter's squarewave voltage output by way of a series-excited parallel-loaded tuned L-C circuit, thereby providing for a lamp current of magnitude dependent upon the frequency of inverter oscillation.

Abstract: In a ballast for operating one of a high-pressure sodium-vapor and a mercury-vapor lamp from a source of electric power, the ballast has a first one of a condenser and an inductor connected to be in series between the lamp and the source of electric power. A second of the one of the condenser and inductor is connected in a path that is connected in parallel with the first one of the condenser and inductor. A timer is connected to the source of electric power and a relay is in path for closing the path, the timer providing a predetermined time only to the relay for opening the path, whereby the electric power consumed by the ballast for operating the lamp is reduced when the relay has opened the path.

Abstract: In a self-oscillating inverter-type fluorescent lamp ballast, the inverter's output is a squarewave voltage of frequency controllable about 30 kHz. The squarewave voltage is applied across a series-connected high-Q L-C circuit. The fluorescent lamp is connected in parallel with the tank capacitor of this L-C circuit. Before the lamp ignites, the magnitude of the voltage developing across the tank capacitor is a sensitive function of the frequency of the squarewave voltage and is controlled to a suitable level by correspondingly controlling the frequency of the squarewave voltage to be higher than the natural resonance frequency of the unloaded L-C circuit. After the lamp has ignited, the magnitude of the lamp current is a sensitive function of the frequency of the squarewave voltage and is controlled to a suitable level by correspondingly controlling the frequency of the squarewave voltage.

Abstract: A circuit for a Xenon lamp is disclosed comprising an inductor having first, second and third connectors between one terminal of the lamp and a power line, said first connector being connected to said power line, means connecting the third connector to a second terminal of the Xenon lamp, means including control conducting means connected between said second connector to either of said first and third connectors, and means for controlling the control conducting means to control shunting of said inductor between first and second power lines to control power input to the Xenon lamp.

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 lag ballast for a high intensity discharge lamp includes a transformer providing voltage at either of two levels. Triacs tied to the transformer supply current at the desired voltage level through either of two inductances. The triacs are controlled by a comparison circuit so that a low voltage and high current are supplied to the lamp during startup and a lower current and higher voltage are supplied as the lamp approaches its normal operating temperature.

Abstract: A discharge lamp ballast for stabilizing wattage input into a discharge lamp at different levels in two or more ranges comprises a magnetic core forming a closed magnetic circuit. A main winding on the core may be used alone or with an extended winding switched in series, and be connected in series with the lamp across an alternating current source in a lamp operating circuit. A control winding on the core has a triac connected across it to vary the current and thereby the wattage supplied to the lamp in the operating circuit. A pair of gapped shunts, one located between the control winding and the extended winding, and the other between the extended winding and the main winding, assure a proportionally greater control effect on the series reactance in the lamp operating circuit when the extended winding is switched in than when it is not.

Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level of a gas discharge lighting arrangement having four or more gas discharge lamps with multiple ballasts. Load side control of each ballast is provided by a timed interval controlled impedance, serially coupled between the particular ballast and its associated lamps. A circulating inductor, coupled in parallel with each controlled impedance, provides a current path between the power source and the lamps at least during that portion of the AC waveform when the controlled impedances are non-conducting. The invention is equally operable at both 120 volt and 277 volt AC levels without major component changes.

Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level in gas discharge lighting arrangements. Load side control is provided by a timed interval controlled impedance, serially coupled between the ballast and the lamp(s). A circulating inductor, coupled in parallel with the controlled impedance, provides a current path between the power source and the lamp(s) at least during that portion of the AC waveform where the controlled impedance is in a substantially non-conducting state.

Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level in gas discharge lighting arrangements. Load side control is provided by a timed interval controlled impedance, serially coupled between the ballast and the lamp(s). A circulating inductor, coupled in parallel with the controlled impedance, provides a current path between the power source and the lamp(s) at least during that portion of the AC waveform where the controlled impedance is in a substantially non-conducting state.

Abstract: The invention is directed to a circuit and a method for efficiently controlling the output illumination level of a gas discharge lighting arrangement having four or more gas discharge lamps with multiple ballasts. Load side control of each ballast is provided by a timed interval controlled impedance, serially coupled between the particular ballast and its associated lamps. A circulating inductor, coupled in parallel with each controlled impedance, provides a current path between the power source and the lamps at least during that portion of the AC waveform when the controlled impedances are non-conducting. The invention is equally operable at both 120 volt and 277 volt AC levels without major component changes.

Abstract: A high intensity discharge ballast that provides instant restrike of hot high intensity lamps, rapid warm-up and normal ballasting functions so as to circumvent the deficiencies of heating and cooling cycles in high intensity discharge lamps which cycles are unacceptable in special applications such as graphic arts and stadium lighting.

Abstract: A dimmer switch for a fluorescent lamp having a gaseous discharge light bulb, the switch being adapted to be connected in a ballast circuit including the light bulb and comprising a tapped inductor having a plurality of coil segments connected in series with one another and a plurality of taps or terminals, one at each end of the inductor and one between each adjacent pair of coil segments, with a first one of the end terminals of the inductor being adapted to be connected in the ballast circuit. The switch further comprises a movable switch member for selectively connecting any one of the terminals other than the stated first end terminal in the ballast circuit, whereby, for a given ballast circuit input voltage, the impedance of the inductor as connected in the ballast circuit and thus the ballast circuit current may be varied to produce the desired level of light output of the bulb by adjusting said movable switch member.

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: Composite structure for use as an HID device ballast component and which performs the dual functions of voltage transformation and provision of ballasting reactance which can be cntrollably shifted in value. A multi-leg magnetic structure has a primary winding carried on a first leg thereof and an output winding carried on a second leg thereof. A control winding is carried on a third leg and a gap of predetermined dimensions is provided in the magnetic path which includes the third leg. The magnetic core member and the windings carried thereon display leakage flux paths of predetermined total permeance. A bilateral switch connects to the control winding and is operable to be closed once each half cycle of normal lamp operation. With the control winding closed, the counter mmf generated in the third leg decreases the inductive reactance of the structure by a predetermined amount, with the inductive reactance of the structure essentially established by the permeance of the leakage paths.

Abstract: High efficiency push-pull inverters minimize undesirable energy losses usually resulting from simultaneous conduction and imperfect switching of the transistor switching means. In each of the disclosed circuits, a saturable inductor and a diode are connected in parallel and across the base-emitter junction of each transistor. Voltage on the base of each transistor causes its associated saturable inductor to saturate, and the saturated inductor then terminates the flow of base current and provides a path for rapid evacuation of the charge carriers stored in the transistor base-emitter junction in order to render the transistor rapidly non-conductive. Each diode provides a drain path for current continuing to flow through its associated saturable inductor after junction evacuation. A novel triggering means initiates oscillation of the inverters.