Abstract: A discharge lamp lighting apparatus includes: an inverter circuit including a switch circuit and a high-voltage transformer; a step-up circuit connected at the input stage of the inverter circuit; a control circuit to output a switch circuit controlling signal and a step-up circuit controlling signal; an on-off switching circuit connected at a input voltage line; and a switch signal buffering circuit connected between the control circuit and the switch circuit and adapted to relay the switch circuit controlling signal. A drive voltage is applied to the control circuit without going through the on-off switching circuit, and a drive voltage is applied to the switch signal buffering circuit via the on-off switching circuit. With such a structure, an excess rush current is inhibited from flowing into the discharge lamp thereby preventing its electrode wear and therefore increasing the product life of a lamp and enhancing reliability while achieving cost reduction and downsizing.

Abstract: A ballast with circuitry to allow the level of the lighting device to be adjusted, a separate direct current input and a sensing circuit within the ballast to lower the light level and thus the amount of power required from the direct current input when the normal line power fails. The system includes placing a sensing device within the ballasting circuitry housing and using a fiber optic conductor to conduct the light into the ballast from an external source. The system further includes recharging the battery by supply current to flow out of the direct current input when the ballast is operating from line power.

Abstract: An LED driver circuit that sinks pure DC current through LEDs. According to the invention, a constant current sink circuit is coupled to a full bridge rectifier. The full bridge rectifier includes at least a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm. The first bridge arm and the fourth bridge arm are connected in parallel with the third bridge arm and the second bridge arm in opposite directions, respectively. The connection of the first bridge arm and the third bridge arm and the connection of the second bridge arm and the fourth bridge arm are connected in series. Each of the bridge arms may consist of at least one LED. The constant current sink circuit is used for sinking pure DC current. The LEDs can be driven by pure constant current and can provide desired luminance.

Abstract: A driving device for driving a light source module (12), includes an inverter circuit (15) for converting a received signal to a signal driving the light source module, a feedback and filter circuit (13) for feeding back currents flowing through the light sources and filtering radio frequency interference (RFI) signals of feedback currents, and a controller (14) electrically connected between the feedback and filter circuit and the inverter circuit. The feedback and filter circuit includes at least one filter for filtering the RFI signals of the feedback currents, and a resistor (R) for feeding back the current flowing through the light source module. The filter includes an impedance (Z11) including a first terminal designated as an input of the filter and a second terminal, and a capacitor (C11). The capacitor includes a third terminal designated as an output of the filter and a fourth terminal electrically connected to ground.

Abstract: A driving apparatus includes a DC-to-DC converter, a first LED series, a second LED series, a first constant-current circuit, a second constant-current circuit, and a feedback circuit. The DC-to-DC converter respectively outputs a direct-current voltage to one terminal of the first and the second LED series to generate a first potential and a second potential at the other terminal of the first and the second LED series according to a feedback voltage. The first and the second constant-current circuits are respectively coupled to the other terminal of the first and the second LED series and output a first current and a second current for driving the first and the second LED series according to a first and a second control signals. The feedback circuit uses the lower one of the first potential and the second potential as a feedback voltage.

Abstract: An inverter capable of switching working frequency for activating a lamp. The inverter comprises a voltage converter, a feedback circuit, a control unit and a frequency switcher. The voltage converter transforms a DC input voltage into a second AC voltage according to a control signal. The lamp is activated and generates a feedback current. The circuit converts the feedback current into the feedback voltage. The control unit for generating a first working frequency includes a resonance circuit having a specific resistance and capacitance, and a control device for generating the control signal according to a reference voltage, the first working frequency and the feedback voltage in a predetermined period. Then, the switcher changes the specific resistance and/or capacitance for enabling the control unit to generate a second working frequency. The control device outputs the control signal according to the second working frequency and the feedback voltage.

Abstract: A method and circuit arrangement dynamically calibrate a photosensitive control for a light source that includes a voltage divider circuit coupled to a resistive light detector and configured to output to a comparison circuit a variable voltage signal that varies with the resistance of the resistive light detector. To calibrate the photosensitive control, a variable impedance circuit in the voltage divider circuit is adjusted to null out any changes in voltage caused by feedback from the controlled light source. The amount of correction is proportional to the amount of light feedback. Based on the amount of correction needed, a new reference voltage is selected that will accurately detect the next dusk to dawn transition while the light feedback is present.

Abstract: An apparatus for operating a plurality of discharge lamps is to be designed so as to be more cost-effective. A first current control device, in particular a heat-sensitive resistor having a positive temperature coefficient, is connected in parallel with a first contact device for electrically connecting a first discharge lamp. Furthermore, a second contact device for electrically connecting a second discharge lamp is connected in parallel with a second current control device, the first and second contact devices being connected in series. A defined preheating period for the lamps can therefore be achieved. By using a sequential starting capacitor in parallel with one of the lamps, impermissible load current surges may be avoided.

Abstract: A direct-current dimmer switch with low noise. A direct-current switch is turned on relatively slowly to avoid noise generation. Input capacitance of the direct-current switch device works in conjunction with a switch input series resistor to avoid a sharp turn-on characteristic. A set-point is compared against a voltage ramp to generate a pulse provided to the switch input. Essentially the full voltage is supplied to the load during the pulse. In one embodiment, a field-effect transistor with a low series resistance is used as the direct-current switching device. The ramp is generated by an integrator that is turned off at zero crossings of the alternating input line voltage to re-set the integrator. In a further embodiment a detector, such as a passive infra-red detector, is used to turn on the dimmer switch at a pre-set level.

Abstract: This invention relates to a power supply that integrates a rectifier/filter's circuitry and a converter's circuitry with an inverter to reduce space occupied and increase power efficiency. The power supply includes: a rectifier/filter, a DC-DC converter and a DC-AC inverter. The rectifier/filter, connected to an alternating current (AC) input terminal, converts the input AC into a direct current (DC). The DC-DC converter and the DC-AC inverter are parallel to each other with one end concurrently connected to the rectifier/filter's output and the other end respectively outputting the desired powers. As such, DC-DC converter reduces the converted DC voltage to lower DC voltages to power all circuits except for the lamp and DC-AC inverter converts the converted DC voltage into higher AC voltage output to drive the lamp.

Abstract: A direct-current dimmer switch with low noise. A direct-current switch is turned on relatively slowly to avoid noise generation. Input capacitance of the direct-current switch device works in conjunction with a switch input series resistor to avoid a sharp turn-on characteristic. A set-point is compared against a voltage ramp to generate a pulse provided to the switch input. Essentially the full voltage is supplied to the load during the pulse. In one embodiment, a field-effect transistor with a low series resistance is used as the direct-current switching device. The ramp is generated by an integrator that is turned off at zero crossings of the alternating input line voltage to re-set the integrator. In a further embodiment a detector, such as a passive infra-red detector, is used to turn on the dimmer switch at a pre-set level.

Abstract: The present invention relates to a driving system for multiple lamps, which comprises a plurality of lamps including one master lamp and at least one slave lamp, an inverter circuit for converting DC power to AC power to be supplied to said plurality of lamps, and at least one current balancing circuit having an impedance device coupled to each of the slave lamp, so that the equivalent impedance varies with the current values of said master lamp and each of said slave lamps to thereby balance the currents in said master slave lamps.

Abstract: A sensor circuit detects a current supplied to a set of light-emitting diodes and produces a current reading dependent on the temperature of .operation of these light-emitting diodes. The sensor circuit comprises first and second serially interconnected resistors also connected in series with the set of light-emitting diodes. The sensor circuit also comprises a temperature-dependent impedance connected in parallel with one of the first and second resistors. At least a portion of the current through the set of light-emitting diodes flows through the sensor circuit to enable the first and second serially interconnected resistors and the temperature-dependent impedance to produce a variable voltage signal representative of the current through the set of light-emitting diodes, this variable voltage signal being dependent upon temperature. The above sensor circuit finds application in a substantially constant intensity light source.

Abstract: The invention relates to a method for adjusting at least one operating parameter of an operating unit (EVG), equipped with a microcontroller (MC), for electric lamps. The adjusting method according to the invention includes a closed loop which carries out a successive correction of at least one drive parameter, stored in the microcontroller (MC), for the voltage transformer of the operating unit (EVG). There is no need for an adjusting resistor.

Abstract: A sensor circuit detects a current supplied to a set of light-emitting diodes and produces a current reading dependent on the temperature of operation of these light-emitting diodes. The sensor circuit comprises first and second serially interconnected resistors also connected in series with the set of light-emitting diodes. The sensor circuit also comprises a temperature-dependent impedance connected in parallel with one of the first and second resistors. At least a portion of the current through the set of light-emitting diodes flows through the sensor circuit to enable the first and second serially interconnected resistors and the temperature-dependent impedance to produce a variable voltage signal representative of the current through the set of light-emitting diodes, this variable voltage signal being dependent upon temperature. The above sensor circuit finds application in a substantially constant intensity light source.

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 system for providing one-step dimming of indicator lights in an illuminating indicating device while allowing adjustable control of the general illumination of the device. The system includes a first current drain (176) coupled to an indicator light source (32-42) for drawing a first current through the indicator light source. A second current drain (186), controlled by control circuitry (198), couples to the indicator light source (32-42) for selectively drawing additional current through the indicator light source (32-42). In a preferred embodiment, the first current drain (176) couples to the second current drain (186) to regulate the additional current draw by the second current drain (186). Preferably, the control circuitry (198) is responsive to an illumination signal to prevent the additional current draw during a low ambient light condition. For general illumination of the indicator device (10), an illumination light source (56-60) responsive to the illumination signal may also be included.

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: A power regulator system provides power to an electrical load. A power level selector generates a reference signal which indicates a desired power level for the electrical load, and a control circuit connected with a AC power source interrupts flow of the AC current for periods of time responsive to a reference system from the power selector. A filtering circuit filters the output of the control circuit and generates therefrom a second output AC circuit which is smooth relative to this interrupted AC circuit. This smooth AC output is applied to the load. A relay is provided to prevent overload conditions from forming adjacent the load in the circuit. Various types of sensors may be used as the power level indicator, such sensors including the light detector as movement detectors, and other electrical sensors.

Abstract: A compact dimmable fluorescent lamp apparatus that connects with at least one fluorescent lamp and with an input power source that supplies an AC input voltage. The lamp includes a rectification stage for rectifying the AC input voltage, a dimming stage for generating a dimming signal indicative of lamp brightness, and a ballast circuit that is in electrical communication with the rectification stage and the dimming stage. The ballast circuit is arranged for connection with the lamp for applying power variably to the lamp and includes a resonant circuit stage that electrically connects with the lamp and that generates a high frequency voltage in response to the input voltage. The resonant circuit varies the level of power supplied to the lamp in response to the dimming signal, thereby attaining a selected level of lamp brightness.

Abstract: A modulation circuit (Q.sub.1) supplies a correction current (i.sub.2) to an S-shaping capacitor (C.sub.23) to modulate the voltage across a deflection winding (L.sub.H) for correction of inner raster distortion. The frequency of the correction current is lower than line frequency for the correction of inner pincushion or barrel distortion. For correction of second order inner pincushion or barrel distortion, the frequency is higher than line frequency. The direction of the correction current in the S-capacitor can be made the same or opposite to the deflection current, resulting in an additive or a subtractive correction. The amount of the inner correction is adjustable independent of the outside raster correction. The modulation circuit is driven by deflection energy and is independent of the flyback transformer (T.sub.20).

Abstract: A current feedback type discharge lamp lighting device including a switching circuit which switches an impedance of an impedance device in accordance with the number of connected discharge tubes. In the discharge lamp lighting device, a tube current for each of the connected discharge tubes is maintained constant, and the discharge lamp lighting device tends to not be effected by stray capacitance.

Abstract: This is an electron emission with a semiconductor substrate having a p-type semiconductor layer whose impurity concentration falls within a concentration range for causing an avalanche breakdown in a least a portion of a surface of the semiconductor layer. A Schottky electrode is connected to the semiconductor layer. There are a means for applying a reverse bias voltage between the Schottky electrode and the p-type semiconductor layer to cause the Schotty electrode to emit electrons, and a lead electrode, formed at a proper position, for externally guiding the emitted electrons. At least a portion of the Schottky electrode is formed of a thin film of a material selected from metals of Group 1A, Group 2A, Group 3A, and lanthanoids, metal silicides of Group 1A, Group 2A, Group Group 3A, and lanthanoids, and metal borides of Group 1A, Group 2A, Group 3A, and lanthanoids, and metal carbides of Group 4A. A film thickness of the Schotty electrode is set to be not more than 100 .ANG..

Abstract: A ballast for providing a dimmable fluorescent lamp (42) has a potentiometer (46) connected to AC power source (10). The potentiometer (46) is connected to a dimming circuit (44). In response to changes in the resistance of the potentiometer (46), dimming circuit (44) causes the duty cycle of a pulse width modulator (18) to change, thereby dimming the fluorescent lamp (42). A dimming disable circuit (60) disables the dimming circuit (44) when power is initially applied to the ballast (6) so that the lamp (42) will ignite.

Abstract: A switchmode AC power controller for controlling the current through a load such as a large lamp array connected to an alternating current source. The controller contains an AC solid state switch, a synchro-flywheel, an output inductor and capacitor. The load current is controlled by triggering signals generated by a synchronized modulator.

Abstract: To provide for dimmer operation of a fluorescent lamp (L) with a minimum of circuit components, the d.c. output level at an output terminal (C1) of an energy supply source, such as a switched mode power supply (10, 10'), is controlled in accordance with the setting of a dimmer control (D). The voltage level at the output capacitor (C1) of the switched mode d.c. power supply furnishes supply voltage for an inverter (T1, T2) coupled to the discharge lamp. During lamp operation, a control unit (R) controls the level of the d.c. voltage supply for the inverter in accordance with the dimmer setting. This permits change of the brightness of the fluorescent lamp (L) in a range of from 5% to 100% of nominal value. Preferably, control of the supply voltage for the inverter is activated only upon occurrence of the ignition or arc-over phase, for example under control of a timing circuit (ZS), controlling a relay in the preheating circuit of the lamp.

Abstract: This invention suppresses the occurrence of interference in a very short period to prevent device destruction. An inverter circuit of this invention includes a crystal oscillator, which oscillates at a fixed frequency, a load-status detector, which receives a voltage and current to be applied to a load including an inductive or capacitive component and detects the status of the load, a voltage-controlled oscillator, which oscillates at a frequency corresponding to the load status detected by the load-status detector, and a switch, which selects the output of the crystal oscillator or the output of the voltage-controlled oscillator and supplies the selected output to the load. An electrodeless discharge lamp lighting device according to this invention uses an inverter circuit having the above structure.

Abstract: A bi-level control system includes a plurality of slave units, each for connection to a respective ballast and HID lamp of a plurality of HID lighting fixtures, and a common control unit. Each slave unit includes a switched capacitor and a slave relay which has one input connectable to a common line of an AC power supply branch circuit powering the fixtures and another input adapted for receiving a line voltage signal. The control unit includes an output connected to the control inputs of each of the slave units by a single control line and switchably connected to line voltage. Dimming of the HID lamp is accomplished by switching line voltage to the output of the control unit which causes the slave relay to switch the slave capacitor into circuit with the HID lamp and ballast. Use of a single control line connecting each of the slave units to the control unit greatly reduces wiring over known systems.

Abstract: A quick start ultraviolet emission unit with an elongated, electrode-type, mercury-filled, arc lamp having spaced end electrodes connected to an electrical power supply that connects to an alternating current power source and to each end electrode of the arc lamp for powering the lamp with an alternating current having a sinusoidal cycle, the unit includes a pulse generating, circuit means connected to said power supply for generating a high current, high voltage, electrical pulse added to the alternating current to the lamp during start-up and restart and a trigger circuit connected to the pulse generating circuit for triggering generated high current, high voltage electrical pulses at the peak potential in the sinusoidal cycle of the alternating current form the power supply.

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: 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 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: 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: Ignition circuit for a gas discharge lamp. In the ignition circuit, the generating of uniform current pulses for ignition over the entire useful life of the gas discharge lamp is guaranteed. A control circuit is provided for holding constant the current-time integral of current pulses applied to the gas discharge lamp during ignition.

Abstract: A self-oscillating half-bridge inverter is powered from a power-line-operated DC voltage source by way of an EMI filter. The inverter is loaded by way of a series-tuned high-Q LC circuit connected across its output. A pair of fluorescent lamps is series-connected across the tank capacitor of the LC circuit. The inverter has two bipolar transistors, each driven by an associated saturable current transformer that provides for a transistor ON-time dependent upon the magnitude of an associated bias voltage. One of the transistors has a control arrangement connected in circuit with its associated saturable transformer and operative to control the magnitude of its associated bias voltage. As the magnitude of this bias voltage is controlled, the magnitude of the voltage across the tank-capacitor, as well as of the current available therefrom, is correspondingly controlled.

Abstract: A back-light device increases the level of luminance produced by a fluorescent lamp at low and high ambient temperatures by increasing the ballast capacitance at these temperatures. The ballast capacitor can include one or more capacitors made from ceramic or the like. The back-light device can be used with different types of video display apparatuses which employ a transmission-type video display plate.

Abstract: The junction temperature rise of a power MOSFET serially connected to a lamp whose resistance nonlinearly increases during turn-on is moderated by the use of control circuitry which initially sets up a relatively low essentially constant current flow through the lamp and transistor and then automatically after the lamp resistance reaches a preselected level, the lamp is allowed to draw significantly more current. The size and therefore cost of the power MOSFET is reduced significantly because the magnitude of the current spike generated by turning on the lamp is significantly reduced the use of the novel control circuitry.

Abstract: The present invention is directed to an illumination source (10) for illuminating an object (11) with light (16) of substantially constant intensity. The illumination source includes an electric light bulb (12) which is supplied with voltage from an adjustable- voltage power supply (14). The voltage supplied by the power supply (14) varies in accordance with the intensity of the light (16) radiated from the bulb (12), as sensed by a photodiode (24). The photodiode (24) is separated from the bulb by a length of lightguide fiber (26) into which light from the bulb is coupled by a glass rod (28). The fiber (26) and the rod (28) allow the photodiode (24) to be supplied with light from the bulb (12), yet to be thermally insulated therefrom, so as to avoid thermal run-away of the diode.

Abstract: A lighting control circuit is provided for controlling illumination and dimming of at least one light in a lighting circuit for operation at a selectable one of a plurality of applied voltages. The lighting control circuit includes a power supply circuit for receiving an AC line voltage input and for converting the AC line voltage to selectable rectified AC and DC power for delivery to the lighting control circuit. A timing generator circuit is also coupled with the power supply circuit and is responsive to a rectified AC sample from the power supply for generating and shaping an electrical timing signal. A timing comparator circuit is responsive to the electrical timing signal for generating a variable duty cycle output signal. A switching control circuit is coupled with the lighting circuit for gating current therethrough in accordance with the variable duty cycle output control signal.

Abstract: A self-oscillating half-bridge inverter is powered from a power-line-operated DC voltage source and has a series-tuned high-Q LC circuit connected across its output. A pair of fluorescent lamps is series-connected across the tank capacitor of the LC circuit. An EMI filter is positioned between the inverter and the power line, thereby to minimize electro-magnetic interference. This same EMI filter also acts to produce a control signal in case a ground fault current were to occur; which control signal is used for preventing the magnitude of the ground-fault current from exceeding acceptable limits.

Abstract: A regulation and intensity controller for prolonging the life of an incandescent lamp controls the root mean square voltage across the lamp by converting AC voltage to a DC voltage and by applying the DC voltage to the lamp through a switch and an inductor in series connection with the lamp. The switch is opened and closed according to a duty cycle that will produce a constant average voltage across the lamp. The switch is closed at fixed intervals and is opened by a circuit that is responsive to the instantaneous current through the lamp and to a voltage signal produced by integrating an error signal that represents the difference between the lamp voltage and a reference voltage. In this manner, the average voltage across the lamp is regulated and ripple is kept within a level such that the average voltage is a close representation of root mean square voltage. Additionally, the cycle-by-cycle current through the lamp is closely regulated.

Abstract: Disclosed is a novel switching circuit directed to use for limiting surge into lamp, comprising a diode circuit wherein two sets of diodes are connected in reverse-parallel; a resistive element connected in series with a lamp to limit the switch-on surge thereinto; a bidirectionally conductive element having a main current path connected in seried with an ac source through said resistive element, diode circuit and lamp; and a timing circuit having a time constant, said timing circuit triggering said bidirectionally conductive element with the voltage across said diode circuit to short-circuit said resistive element after a lapse of said time constant from switch-on.

Abstract: A flashlight is provided with a special circuit for limiting the surge current through the flashlight bulb. The circuit includes a secondary incandescent filament used to energize a transistor gradually upon the activation of flashlight. The transistor in turn gradually energizes the main bulb.

Abstract: A self-contained light sensor head (10) has a photodiode (18) operable to produce an electrical response proportional to light intensity, and an amplifier (20) that produces an output signal from the photodiode's response. The head (10) further includes a gain control circuit, for suitably controlling the gain of the output signal, and has noise and oscillation control circuits. The latter circuits permit the sensor to generate a low voltage output signal that is compatible for input directly to an analog computer.

Abstract: A load is provided, at all times when in operation, with a D.C. voltage having at least a minimum holding magnitude by: providing a source voltage having a peak magnitude greater than the holding magnitude; connecting the source voltage to the load only while the source voltage magnitude is greater than a preselected magnitude; charging from the peak source voltage magnitude an energy storage element while the load is connnected to the source voltage; energizing the load from the charged energy storage element whenever the source voltage magnitude is less than the preselected magnitude; increasing the effective impedance of the load whenever the load is energized by the storage element; and selecting the energy storage element to provide at least the holding voltage to the load during each time interval when the energy storage element is connected to the load.

Abstract: The present invention provides a power supply for lighting an incandescent lamp with high-brightness, comprising connecting a time constant circuit, rectifier, switching device so that the output of the rectifier is supplied to an incandescent lamp through the impedance for a period, determined by the time constant circuit, and that the switching device conducts and shorts the impedance after a lapse of the period to allow the incandescent lamp to receive the output of the rectifier by bypassing the impedance.

Abstract: An intrinsically safe battery pack arrangement for electrically powering electrical devices is disclosed. The power pack has a device for electronically determining a short in a cable or device and switching off the voltage to the power pack. The electronic device includes a transisterized circuit for sensing and controlling current through the cable. When the current exceeds a predetermined maximum, the circuit limits the current in the cable to a maximum value. The circuit is latched in the off position when the short is present for an extended time and the circuit may be reset after the short is removed and the problem corrected. This form of circuitry in power packs for use with mining equipment such as lamps, provides a unit which will not cause hazardous sparks when shorted thereby constituting an intrinsically safe device for use in mines.

Abstract: A current limited strobe charging circuit in which the charging current is automatically limited during the time required to reform the primary storage capacitor after a long period of non-use without materially effecting the current flow and time required to subsequently recharge the storage capacitor after it has been reformed includes a positive temperature coefficient resistor serially connected therewith to switch from a low resistance mode of operation to a high resistance mode of operation as a result of its own internally generated I.sup.2 R heat.

Abstract: A switch circuit is disclosed which warms-up a load prior to complete turn on. The circuit includes a single pole double throw switch and an amplifier. The input to the amplifier connects to the off throw of the switch and the amplifier is rendered nonconducting when the switch is off. However, when the switch is between its off and on position, as it is being thrown on, the amplifier conducts a half wave rectified warm-up current to the load. Then, when the switch is on, the amplifier is bypassed by a short circuit connecting between the on throw terminal of the switch and the load, and the load is driven to 100% capacity via this short circuit.

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.