Abstract: A dimmer for a compact fluorescent lamp including a high-frequency switching circuit for generating PWM or other similar control signals and a filter with simple filtering elements. The dimmer circuitry is simple and can be built on a wall-mountable housing for retro-fitting even in an existing two-wire wall-socket.

Abstract: A ballast (10) for powering a gas discharge lamp load includes an inverter (200) and a protection circuit (400) for preventing start up of the inverter (200) in response to a ground fault condition wherein one or more of the ballast output connections (302,306) is coupled to earth ground.

Abstract: A ballast circuit for driving a fluorescent lamp is provided. The ballast circuit comprises: a self-oscillating circuit; and a series resonant circuit. The series resonant circuit comprises: an inductor; a capacitor; and two diodes. The arrangement of the series resonant circuit: a) causes less power to be dissipated by first and second lamp cathodes when a lamp is coupled to the ballast circuit and increases lamp life, b) protects the ballast circuit from self-destruction when no lamp is coupled to the ballast circuit, and protects the ballast circuit from self-destruction when either the first, second, or both cathodes of a lamp coupled to the ballast circuit have failed.

Abstract: The operating frequency of a ballast is sufficiently far from resonance that, when a compact fluorescent lamp is dimmed to about one percent light output level, the ballast is operating with an open loop gain below a predetermined level, such as, for example, 15, and is operating with an output impedance greater than a predetermined level, such as, for example, the absolute value of the maximum negative incremental impedance of the lamp, and more preferably, greater than twice the absolute value of the maximum negative incremental impedance of the lamp. By changing the frequency to 85 kHz from 80 kHz, for example, the gain is maintained about the same whether the light output is at five percent or one percent, for example. This provides a stable control loop. In this manner, compact fluorescent lamps can be dimmed below about one percent light output, without dropping out and without observable flicker.

Abstract: An inverter circuit for a gas discharge lamp having a primary circuit having a DC voltage supply, a transformer, a switching circuit including a first switch and a second switch for controlling a conduction state of the inverter circuit; a tank circuit having a resonant inductor and a resonant capacitor, the lamp load being coupled with the resonant capacitor; and a capacitor coupled to the first and second switches for maintaining a voltage across a primary winding of said transformer. Accordingly, the required turns ratio of the transformer is reduced by half which reduces the power loss in the transformer, thereby improving circuit efficiency. In addition, energy stored in a leakage inductance, which is otherwise dissipated across the switches of the push-pull switch configuration in the prior art, is recovered or captured by the clamping capacitor, thereby preventing the occurrence of voltage spikes across the switches.

Abstract: A method and apparatus for reducing ripple current in a projector lamp comprising an electrical network comprising input terminals A and C, and output terminals B and D, including a first inductive element and a second inductive element, each inductive element having a first terminal and a second terminal, with the second terminal of the first inductive element electrically connected with the second terminal of the second inductive element at output terminal B, with the first terminal of the first inductive element connected to input terminal A, and the first terminal of the second inductive element connected to input terminal C; and a means for impressing a first source of switching potential from an external source at input terminal A, and a second source of switching potential from the external source out-of-phase with the first source of switching potential, at input terminal C such that a ripple current across the output terminals B and D is minimum.

Abstract: The invention relates to a rod-core transformer for use as a starting transformer in the cap of a high-pressure discharge lamp for a motor vehicle headlight. According to the invention, the rod-core transformer has at least two cores (2, 3) which are in the form of rods and are arranged alongside one another, and on each of which a multilayer secondary winding (4, 5) is wound, with the respective layers (4a, 4b, 4c, 4d) and (5a, 5b, 5c, 5d) being connected in parallel and being arranged one above the other without any offset. Furthermore the secondary windings (4, 5) are electrically conductively connected to one another, with their total resistance being at most 2 &OHgr;. The transformer according to the invention is particularly highly suitable for use as a starting transformer for high-pressure discharge lamps with a low operating voltage, for example halogen metal-vapour high-pressure discharge lamps which do not contain mercury.

Abstract: A current equalizer assembly for LCD backlight panel comprises at least a differential current choke and at least a capacitor. The capacitor is arranged striding on a terminal (B) at a primary coil and on a terminal (D) at a secondary coil of the differential current choke so as to equalize the current flowing through every cold cathode fluorescent lamp (CCFL) connected to the differential current choke and the lightness thereof accordingly. Moreover, the capacitance of the stridden capacitor is replaceable by the intrinsic stray capacitance when the inductance of the differential current choke is properly selected.

Abstract: A ballast circuit for driving a fluorescent lamp is provided. The ballast circuit comprises: a self-oscillating circuit; and a series resonant circuit. The series resonant circuit comprises: an inductor; a capacitor; and two diodes. The arrangement of the series resonant circuit: a) causes less power to be dissipated by first and second lamp cathodes when a lamp is coupled to the ballast circuit and increases lamp life, b) protects the ballast circuit from self-destruction when no lamp is coupled to the ballast circuit, and protects the ballast circuit from self-destruction when either the first, second, or both cathodes of a lamp coupled to the ballast circuit have failed.

Abstract: A reliable and efficient circuit for lighting a discharge lamp is described. An inverter accepts a direct current supply voltage and outputs an alternating current lamp voltage to drive the discharge lamp at a relatively high frequency. In one embodiment, the inverter includes semiconductor switches in a full-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. In one embodiment, the inverter includes semiconductor switches in a half-bridge configuration, a transformer feedback circuit to control the semiconductor switches, and a series L-C resonant circuit. The inverter can drive multiple discharge lamps in a parallel configuration. A bypass circuit can also be coupled across a cathode of the discharge lamp to extend the life of the discharge lamp. The bypass circuit activates when a lamp cathode wears out.

Abstract: A discharge lamp starter includes a DC/DC converter. The DC/DC converter includes a forward section for producing a first output voltage that is determined by a power supply voltage and a turn ratio of a transformer, and a flyback section for producing a second output voltage that is determined by an inductance of a primary winding of the transformer and a current flowing through the primary winding. The DC/DC converter generates its output voltage by adding the first output voltage and the second output voltage. The configuration can reduce the size of the discharge lamp starter.

Abstract: A circuit for controlling current during run-up of a high pressure discharge lamp (140) comprises a buck converter (120) for generating a buck current to drive the high pressure discharge lamp and a control circuit (202) coupled to the buck converter (120) for varying the duty cycle of the buck current during run-up is disclosed. A method for controlling current in an electronic ballast during run-up of a high pressure discharge lamp comprises steps of detecting (501) lamp ignition, providing (502) a buck current to drive the lamp, and varying (504) the duty cycle of the buck current during run-up to control (506) the current in the lamp is also disclosed.

Abstract: An electronic control (1) for a discharge lamp (D), which is arranged to be connected to a source of alternating current (L,N), having a source frequency, the control having a first and second terminal (J,K) for supplying an electrical power output to operate the lamp; a capacitor (T) is in series with the first terminal, having a capacitance sufficiently small to limit a current flow from the first terminal at the source frequency of less than 30 mA.

Abstract: An energy saving electronic control circuit for fluorescent tubes, where it controls the tubes' light output. This system uses a half-bridge topology, which is supplied from an AC to DC current source obtained from the mains supply. The switching transistors are driven at rather high frequencies. An inductor is connected in series with a capacitor, forming an LC circuit, which is connected to the junction between the switching transistors and these resonant at the same switching frequency of the transistors. At least one tube is connected across one capacitor, in other words in series with the inductor at one end and at the center junction of a passive half-bridge formed by two capacitors in series.

Abstract: A circuit to start an HID lamp in a high-frequency start mode and, after starting, to operate the lamp in a low-frequency operating mode is controlled, during the high-frequency start mode, to drive the lamps with a voltage that includes a high-frequency component to ignite the lamp and a unipolar or bipolar offset component to keep the lamp ignited during a transition from the high-frequency start mode to the low-frequency operating mode.

Abstract: A lamp stand with multi-stage light modulation includes plural resistors annularly arranged to form a circular space. The resistors have terminals soldered on the outer walls of U-shaped contact blades, with an empty position terminal provided in the circular space. A light-modulating controller extends in the lamp stand, having a rotor formed with plural slopes on an outer wall for rotor copper strips to rest thereon. A trigger diode is connected to the gate of a triac AC switch and a capacitor is connected to the trigger diode and the paralleled terminals of the resistors and to the main terminals of the triac AC switch. The light-modulating controller is rotated to let the rotor copper strips contact the contact strips of the resistors to turn on power and charge the capacitor. Different resistance values change the breakdown speed of the DIAC and control the gate of the TRIAC to change the voltage effective value of the lamp, thus reaching a goal of light modulating.

Abstract: A power supply connectable to a power source and to a gas-discharge tube. The power supply includes a transformer having a primary winding, a secondary winding, and first and second switches. The switches receive first and second drive signals, respectively, and switch power to the primary winding. The power supply further includes a controller interconnected to the first and second power switches. The controller is operable to generate the first and second drive signals for a time period. For a first time interval of the time period, the controller transitions the first and second drive signals from a first frequency to a second frequency. For a second time interval of the time period, the controller generates the first and second drive signals at the second frequency. For a third interval of the time period, ceases generation of the varying signal.

Abstract: An auxiliary lighting system for a high-intensity discharge lamp. In one embodiment, the auxiliary lighting system has an auxiliary light source, an HID lamp status circuit having an input for connection to a status signal representative of the operational state of a high-intensity discharge lamp wherein the HID lamp status circuit determines whether the status signal meets predetermined signal criteria, a switch circuit having a first state that effects application of a voltage source to the auxiliary light source, and a second state that isolates the voltage source from the auxiliary light source, and a control circuit responsive to the HID lamp status circuit for controlling the switch circuit. The control circuit has a first state when the HID lamp status circuit determines that the status signal meets the predetermined signal criteria and a second state when the HID lamp status circuit determines that the status signal does not meet the predetermined signal criteria.

Abstract: An electronic operating device for discharge lamps is disclosed in which an output terminal is connected via a coupling capacitor (CB) to a reference potential (E). An electric component (VC) which acts as a voltage source is inserted in series with the coupling capacitor (CB) in order to reduce the potential of an output terminal. The electric component (VC) consists in one embodiment of an inductor which is coupled to the lamp inductor.

Abstract: A photo-thermal epilation apparatus enables the efficient delivery of a high energy light pulse of a sufficiently short duration to a selected follicle to effect permanent hair removal. The apparatus includes a flash lamp powered by a power supply module having an energy storage module interposed between the power supply module and the flash lamp. The energy storage. module, which has an output or network impedance matched to the flash lamp, produces a flattened and extended current pulse that is coupled from the energy storage module to the flash lamp in order to the energize the flash lamp to produce the desired high energy light pulse. An optical system, which includes a tapered needle-less probe, is included to receive the light pulse produced by the flash lamp and efficiently deliver the light pulse to a selected hair follicle to effect the photo-thermal epilation of the associated growth support tissue.

Abstract: A circuit arrangement and control thereof for igniting a high intensity discharge (HID) lamp, for reducing the variation of the resonant ignition voltage under the parasitic capacitive loading condition, and for increased circuit stability. The high frequency ignition voltage is only applied to the lamp during an ignition phase. The variation of the magnitude of the resonant ignition voltage with respect to the parasitic capacitance at the lamp leads is minimized by inserting a damping resistor in series with the ignition resonant capacitor. In a normal operation after ignition, the charge and/or discharge current of the ignition resonant capacitor is bypassed through a bypass device instead of flowing through a current sense resistor, so that only a chopper current flows through a sensor by paralleling a relatively high impedance resistor with the sensor.

Abstract: An electronic control circuit for adjusting the control voltage of a device to be controlled, the control circuit comprising a primary coil, a control bus comprising means for adjusting the control voltage, parallel-connected with the first capacitor, the paralleling being further series-connected with the first secondary coil and a first control diode, and a control voltage supply circuit comprising a series-connected second secondary coil, a second control diode and a second capacitor. The primary coil is connected between a first node and a second node of the device to be controlled, and the nodes in the connection are selected such that the current in an electric circuit between them at least momentarily reaches the value zero.

Abstract: A power supply apparatus includes a direct current power source having a pair of terminals. First and second switching elements are connected in series between the pair of terminals of the direct current power. A load circuit, which includes a resonance inductance and a resonance capacitance, receives a high-frequency alternating current generated by a switching of the first and second switching elements. An unsaturated transformer has a first winding connected to the load circuit, and a second winding generating an induced voltage in proportion to a current flowing in the load circuit. A drive resonance circuit includes a capacitance, and an inductance of the second winding. The drive resonance circuit produces a resonance output to cause the first and second switching elements to alternately conduct. The power supply may be used in a ballast for a discharge lamp.

Abstract: The discharge lamp lighting apparatus includes: a direct current power supply E; switching elements Q1 and Q2 for switching a direct current supplied from the direct current power supply E so as to generate a high frequency current; a discharge lamp load circuit LAC1 which is constructed in a manner that a discharge lamp LA and a coupling capacitor C4 are connected in series, and the discharge lamp LA is lit by a high frequency current generated by the switching elements Q1 and Q2; a switching element control circuit IC1 for controlling the switching elements Q1 and Q2. The discharge lamp lighting apparatus is further provided with a protective circuit NP2 which distinguishes a fault of the discharge lamp LA by detecting a voltage generated in the coupling capacitor C4, and outputs a control signal to the switching element control circuit IC1.

Abstract: A ballast circuit for a single or multiple lamp parallel operation where at each lamp a condition may be controlled such that the amplitude of a resonant inductor current and an output voltage are almost constant in the steady state. The circuit consists of a half-bridge of a DC storage capacitor, a DC blocking capacitor, power transistors which alternately switch on and off and have a 50% duty ratio, and an LLC resonant converter having a resonant inductor and one or more resonant capacitors. The circuit also includes an output transformer providing galvanic isolation for a double path type power feedback scheme. The output transformer produces magnetizing inductance utilized for power feedback circuit optimization and is connected right after the resonant inductor of the half-bridge circuit.

Abstract: An arrangement in connection with a discharge lamp, the arrangement comprising an electronic ballast for igniting and burning the discharge lamp, and a voltage control device arranged to modify supply voltage of the ballast. The voltage control device is further arranged to include a power control signal in the supply voltage. The arrangement further comprises a power filter and a control filter for separating the power control signal from the supply voltage, the ballast being responsive to the power control signal in order to control the level of light of a fluorescent tube.

Abstract: An electronic ballast for operating a lamp with a high-frequency current is equipped with a load branch comprising two LC combinations. The LC combinations are dimensioned such that the shape of the high-frequency current is in between a sine shape and a square-wave shape. The efficacy of a lamp operated by means of the electronic ballast is high, while the RFI generated by the lamp is low.

Abstract: A ballast for powering a gaseous discharge lamp that has a required minimum ignition voltage and a permissible maximum ignition voltage. Via a cable through which ignition voltage pulses are delivered to the lamp. The ballast has a first state of operation wherein a first reactive energy source charges parasitic loading capacitance of the cable to a voltage that does not exceed the permissible maximum voltage of the lamp when the parasitic loading capacitance of the cable is within a first predetermined range of capacitances. The ballast has a second state of operation wherein the second reactive energy source charges the parasitic loading capacitance of the cable to at least the required minimum ignition voltage of the lamp when the parasitic capacitance of the cable is within a second predetermined range of capacitances.

Abstract: A hot restrike protection circuit provides complete shut down protection for a self-oscillating high intensity discharge lamp ballast of the type comprising a pair of complementary switching devices in a bridge configuration with a gate drive inductor in series with a second inductor, i.e., a control inductor, at the junction between the switching devices. The hot restrike protection circuit effectively comprises a three-terminal device for coupling across the control inductor. In particular, the HRP circuit comprises a sensing network for sensing voltage across the control inductor, a breakdown network for providing a breakdown path upon reaching a predetermined restrike voltage threshold across the control inductor, and a shutdown network for shutting down operation of the ballast until the lamp is sufficiently cool for restarting, thereby protecting ballast components during hot restrike, or re-ignition, of the lamp.

Abstract: A ballast circuit for an electrodeless lamp designed to use a phase dimmer signal to control output of the electrodeless lamp. Dimming ballast circuit includes a rectifier circuit for rectifying an input voltage from a phase dimmer source to generate a pulsed d.c. voltage on a d.c. bus. Ballast circuit further includes a converter control circuit coupled to the rectifier circuit for inducing an r.f. a.c. load current at approximately 2.5 MHz. The converter circuit includes first and second complementary converter switches serially connected between the bus and a reference node. The switches are connected together at a common node through which the a.c. load current flows. A driving inductor is connected at one end to the common node and operatively connected at the remaining end to the control node. A load circuit includes a resonant inductor connected at one end to the common node, with the resonant inductor mutually coupled to the driving inductor. An r.f.

Abstract: A half-bridge converter for operating a discharge lamp utilizes a non-linear coil in series with the discharge lamp. Suitable proportioning ensures an unambiguous relation between the frequency of the lamp current and the lamp power over a comparatively large range of lamp power.

Abstract: A high intensity discharge (HID) lamp driving circuit. The HID lamp driving circuit includes a first pair of switching devices connected to a high frequency resonant filter, and a second pair of switching devices connected to a ripple reducing filter. A HID lamp is connected between the first pair of switching devices and second pair of switching devices, with a dc power supply being connected to the first pair of switching devices and the second pair of switching devices. The first pair of switching devices and the second pair of switching devices are connected to a common ground with the dc power supply. The lamp driving circuit operates in a half bridge topology during a start-up operation mode of the lamp, and operates in a full-bridge topology during a steady-state operation mode of the lamp. The HID lamp driving circuit is operated in an active zero current switching scheme.

Abstract: A method and device for operating electronic ballasts for high intensity discharge lamps, the ballasts having a driver, two power switches, an LC series circuit, a driver controller, a current sensor, and a power sensor.

Abstract: A ballast circuit for supplying AC voltage and current to a gas discharge lamp, mounted in a troffer having a ground connection, upon the application of DC voltage and current. The circuit comprises: a transformer including a first and a second primary winding; first and second transistors, each having base, collector and emitter terminals, wherein the base terminal of each transistor is coupled to a drive terminal of the second primary winding; a constant current flow network coupled to the drive terminal so as to maintain the circuit in an oscillating mode; the first primary winding configured to be coupled across the lamp such that a capacitance at a first end of the lamp relative to the transformer is equal to a capacitance at a second end of the lamp relative to the transformer; and a current supply source coupled to the troffer ground connection. The circuit is configured such that a net current induced via the lamp and the current supply source into the troffer is substantially equal to zero.

Abstract: In a ballast circuit for operating a discharge lamp, two different lamp power levels are adjustable. The ballast circuit is equipped with a switch to optimize the amount of power feedback for the lamp power level. This enables total harmonic distortion and power balance to be optimized for more than one power level.

Abstract: A method and apparatus for regulating the lamp output voltage in a multiple (parallel) discharge lamp fixture irrespective of the number of operating lamps and based upon monitoring of the lamp filament current. A modification thereof provides constant and equal currents in the discharge lamps irrespective of the number of operating lamps.

Abstract: An electronic ballast is configured to receive the input from a power source in order to control operation of a lamp connected to the electronic ballast. The ballast includes a positive side bus voltage line and a ground reference line. An input section is connected to the power source, to the positive side bus voltage line and the ground reference line. A complementary pair of switches, connected to bus and to the resonant network, is controlled by a gate drive network. The gate drive network receives feedback signals that is coupled to transformer and controls operation of the set of switches using the received and further processed signals. A triac dimmer is connected between the power source and the input section for providing a dimming capability. A resonant network includes at least a first resonant capacitor connected to the resonant network and to at least one of the positive side bus voltage line and the ground reference line.

Abstract: An electronic ballast for providing electrical energy to one or more fluorescent lamps having electrical discharge filaments. The ballast includes a pre-heating circuit having a first resonant frequency, coupled to pre-heat the filaments. An ignition driver circuit having a second resonant frequency is coupled to ignite an electrical discharge through a gas between the filaments. Power controller circuitry provides power to the pre-heating and ignition driver circuits in succession, so as to ignite the one or more lamps. The power controller circuitry first provides power to the pre-heating circuit substantially at the first resonant frequency and subsequently provides power to the ignition driver circuit substantially at the second resonant frequency, by a smooth operating frequency transition from pre-heating to ignition. The ballast also features a voltage-controlled pre-heating circuit, and circuit configuration capable of igniting the lamps even in the case where one or both of the filaments are broken.

Abstract: A preheating circuit for a fluorescent lamp is provided. The preheating circuit includes a filament detecting circuit indirectly detecting a filament resistance in a fluorescent lamp by measuring a filament voltage and a filament current, a pulse generation circuit providing pulses of one of a first frequency and a second frequency determined by the detected filament resistance and a specific filament resistance, and a filament resonance circuit operating the fluorescent lamp at an operating frequency determined by the pulse generation circuit. Therefore, the filament resonance circuit operates at the first frequency to preheat the fluorescent lamp when the detected filament resistance is smaller than the specific resistance. The filament resonance circuit operates at the second frequency to operate the fluorescent lamp when the detected filament resistance is one of a first value being larger than and a second value being equal to that of the specific resistance.

Abstract: An electronic ballast with a voltage-fed, LC or LLC resonant inverter for multiple gas discharge lamp independent operation which maintains a substantially constant voltage to a lamp or lamps connected to the ballast even during a transition period when a lamp or lamps is ignited, extinguished, added or removed. The ballast includes a feedback loop that maintains a substantially constant phase angle between the voltage and the current in an LC or LLC tank circuit, which has the effect of the ballast providing the substantially constant voltage output. The feedback loop obtains a current feedback signal and a voltage feedback signal from the tank circuit, and provides a phase shifted signal as a feedback correction signal which is the current feedback signal phase shifted by the voltage feedback signal that tracks phase angle changes with one, some or all of the lamps of a set thereof connected to the ballast, and during the transition period.

Abstract: A high-pressure discharge lamp has integrated in its base or base housing a circuit arrangement (SCH) which combines a starting device and a power reducing circuit which comprises a phase-gating control (PS). A capacitor (C2) connected in parallel with the lamp (L) provides a transfer voltage which is distinctly higher than the input voltage of the arrangement.

Abstract: A power-factor correction circuit of an electronic ballast for fluorescent lamps which includes an input full-wave rectification circuit for full-wave rectifying an AC input voltage from an AC input power source, a DC-link capacitor for supplying a DC-link voltage in response to an output voltage from the rectification circuit and a resonant inverter connected in parallel to the DC-link capacitor. The power-factor correction circuit comprises a charge pumping circuit disposed between the AC input power source and the rectification circuit, a valley-fill DC voltage supply circuit disposed between the rectification circuit and the DC-link capacitor, and a high-frequency full-wave rectification circuit disposed between the DC voltage supply circuit and the DC-link capacitor and connected to a secondary winding of a power transformer in the resonant inverter.

Abstract: A high frequency inductively coupled electrodeless lamp includes an excitation coil with an effective electrical length which is less than one half wavelength of a driving frequency applied thereto, preferably much less. The driving frequency may be greater than 100 MHz and is preferably as high as 915 MHz. Preferably, the excitation coil is configured as a non-helical, semi-cylindrical conductive surface having less than one turn, in the general shape of a wedding ring. At high frequencies, the current in the coil forms two loops which are spaced apart and parallel to each other. Configured appropriately, the coil approximates a Helmholtz configuration. The lamp preferably utilizes an bulb encased in a reflective ceramic cup with a pre-formed aperture defined therethrough. The ceramic cup may include structural features to aid in alignment and I or a flanged face to aid in thermal management.

Abstract: An integrated control and regulating circuit (IC) controls, via a half-bridge circuit (V2, V3), a load circuit (4) having the at least one fluorescent lamp (FL) by means of a drive circuit (CCO, SEL, HSD, LSD) regulated in a high-frequency manner. In the control and regulating circuit, each time the lamp is started and/or when there is a disturbance, a timer (PST, IT, CT) is started, which thus defines a sequence predetermined periods of time (&Dgr;pt, &Dgr;it, &Dgr;st, &Dgr;ot), inter alia preheating period (&Dgr;pt) and ignition period (&Dgr;it).

Abstract: A circuit for driving a load. In one embodiment, the load is driven by an inverter circuit having a full bridge circuit divided by inductive elements to provide cross conduction protection. In another embodiment, first and second converter circuits are coupled to the inverter circuit with the inverter and converter circuits having common circuit elements. In a further embodiment, a common mode inducter is inductively coupled to a power circuit for detecting a common mode signal generated by a load current return path disruption. The common mode inductor is coupled to a control circuit for limiting current to the load.

Abstract: The invention relates to a circuit arrangement for operating at least one low-pressure discharge lamp (LP1, LP2) on an inverter (Q1, Q2). The circuit arrangement has a simplified harmonic filter for limiting the harmonic content of the mains current. In the preferred exemplary embodiment, the harmonic filter is formed by the back-up capacitor (C2), the diode (D1), the trapezoidal capacitor (C7) and the resonance capacitor (C6).

Abstract: A high frequency arc lamp power supply (518) and display system (500). The power supply (518) drives an arc lamp (504) at a frequency high enough to several times higher than the display system's LSB frequency. By pulsing the lamp many times during each LSB period, the variations in light output during the pulses are all integrated in each bit period and do not degrade the quality of the image display. This eliminates the need for the controller (514) to synchronize the arc lamp power supply (518) with the spatial light modulator (502) when using pulse width modulation.

Abstract: A high frequency control circuit for a gaseous discharge lamp which includes a mechanically variable reactance device coupled in series with the lamp to control the current fed to the lamp. The mechanically variable reactance device is adjustable by a user to alter the intensity of the light emitted by the lamp.

Abstract: AC voltage is applied to a resonant unit provided with an inductor and a capacitor AC current is supplied to a discharged tube connected to one of the inductor and the capacitor according to the switching operation of the two power semiconductor elements connected in a bridge manner. The resonant unit and first and second voltage drop units are connected in series between I/O terminals of the bridge and the voltages of the first and the second voltage drop units are applied as signals of opposite phases to control terminals of the two power semiconductor elements.

Abstract: Ballast circuit 10 for lamp 52 has a switching network consisting of a complimentary pair of switches 30, 32 which are driven by a low-power universally available controller IC 26. The controller IC 26 is configured with a floating ground arrangement 36. A current sensor 72 assists in generating a negative feedback signal 79 which is provided to an inverting input of operational amplifier 86 of controller IC 26. Prior to being supplied, the negative feedback signal 79 is summed at summing node 80 with a level shifted signal 92, generated by a level shifting circuit 22 which received an input dimming signal 16. The level shifting circuit 22 shifts the dimming signal 16 from a ground reference system to a floating ground design. The level shifted signal 92 and feedback signal 79 are designed to cancel each other whereby the input to operational amplifier 86 is maintained constant as the non-inverting input has a constant internally supplied voltage.