Abstract: An electronic ballast for at least one gas discharge lamp (LA) comprises a rectifier circuit (2) connectable to an a.c. voltage source (Uo), a smoothing circuit (3), connected to the output of the rectifier circuit (2), for generating an intermediate circuit voltage (Uz), and an inverter (4) fed with the intermediate circuit voltage (Uz), at the output of which inverter a connection for the load circuit (5) containing the lamp (LA) is connected. The smoothing circuit (3) is constituted by a switching regulator and the ballast further has a control circuit (6) which detects the intermediate circuit voltage (Uz) and controls a controllable switch (S1) of the switching regulator in dependence upon the value of the intermediate circuit voltage (Uz).

Abstract: A circuit arrangement having at least one electric main switch (T1) with a reference electrode (E), a control electrode (B), and a work electrode (C). A recovery diode (D1; D2) is connected antiparallel to the main flow direction of each main switch (T1). In order to speed up the switch-off process and in particular to reduce the attendant power loss, each main switch (T1) is assigned an electric auxiliary switch (T11; T22), whose work electrode is connected to the control electrode (B) of the associated main switch (T1) and whose reference electrode is connected to the reference electrode (E) of the associated main switch (T1). The capacitor (C11) is disposed between the control electrode of the auxiliary switch (T11; T22) and the work electrode (C) of the associated main switch (T1).

Abstract: A method and apparatus for controlling a lamp. A timer (106) reads a rated safe life value from a memory (102) associated with a lamp in a lamp module (104). The memory (102) in the lamp module (104) contains a series of locations in which the rated safe life of the lamp has been stored, and a series of locations for storing the elapsed on time of the lamp. The timer controller (106) reads the series of locations storing the rated safe life of the lamp and verifies the validity of the values using a series of checksums and comparisons between the various values. The timer controller (106) also reads the series of locations storing the elapsed on time for the lamp and verifies the elapsed on time in a similar manner. If either the rated safe on time or the elapsed on time cannot be verified, the lamp is disabled. If both can be verified, and the lamp is enabled until the elapsed on time equals or exceeds the rated safe life.

Abstract: An interface circuit 10 for coupling a power supply 12 that includes a triac phase modulator 18 with a compact fluorescent lamp converter and lamp load 14. The circuit 10 rectifies the modulated power supply signal with a rectifier 24. A current flowing through a current limiting inductor 112 goes through either a reverse current blocking diode 114 to power the fluorescent lamp or through a transistor 116 to reset/discharge the triac phase modulator 18. Transistor 116 is controlled by an R-S flip-flop. The reset 120 of the R-S flip-flop is connected through a current threshold sensor formed by a pair of resistors 144, 146 and a transistor 142. A high duty cycle oscillator is connected to the set 124 of the R-S flip-flop. Large current variations in the triac phase modulator 18 are prevented by current flowing through transistor 116 when the current no longer flows through the diode 114.

Abstract: A lighting circuit for a discharge lamp incorporates a DC-DC converter for converting DC voltage and a control circuit for controlling the output voltage from the converter by controlling the ON/OFF operation of an FET which is configured as the converter. The electric current which flows in the FET is monitored by detecting the voltage between the drain and the source to turn the field effect transistor off when the voltage level is at the reference value or higher. Thus, a pulse-by-pulse current limitation is performed. Limitation of an electric current in a switching device in a DC-DC converter of a lighting circuit for a discharge lamp is achieved while reducing the size and cost of the circuit apparatus.

Abstract: A circuit which detects near or below resonance operation of a fluorescent lamp being driven with a half-bridge circuit and which deactivates the half-bridge circuit before any damage to the circuit can result. In the circuit of the present invention, the voltage across a sense resistor disposed either the lower transistor switch and ground, or between the lower lamp filament and ground, is compared against a predetermined reference voltage to generate an output comparison signal. The output comparison signal is gated to the turn-off edge of the lower MOSFET (in the case of the sense resistor disposed between the lower MOSFET and ground) or to the turn-off edge of the upper MOSFET (in the case of the sense resistor between the lower lamp filament and ground) to generate a signal for shutting down the half-bridge circuit in the event of near or below resonance operation of the lamp resonant circuit.

Abstract: An electronic ballast for use in illuminating a lamp includes a voltage reference generator that uses a plurality of current amplifiers and resistors having substantially identical resistance characteristics to remain stable in response to temperature variations and despite resistance process dispersion. The reference voltage generator further includes an ON/OFF controller and a dimming function that may be controlled via a single input terminal. Additionally, the dimming function uses a capacitor to prevent abrupt changes in an input signal from causing abrupt changes in a feedback signal that controls an output frequency of the ballast.

Abstract: A power supply is provided for illuminating an electro-luminescent lamp with a constant current and frequency drive signal having a predetermined limiting voltage level for compensating changes in the electro-luminescent lamp characteristics. The power supply operates from an AC or DC input voltage power source and includes an electronic ground fault current interrupter circuit means with remote reset capability to provide protection for the power supply and against user injury. An auto line AC voltage selection circuit senses and selects the proper voltage operating configuration without operator intervention. The status of an LED in conjunction with the status of the electro-luminescent lamp is used as an internal diagnostic aid to assist a user in isolating fault conditions. External signals from a lighting control panel are coupled via an input control circuit to the power supply to provide special lighting effects.

Abstract: A lamp protection circuit for smaller gas discharge lamps and for compact fluorescent lamps powered by a ballast. The circuit protects against several lamp failure modes that can cause overheating and cracking of the lamp. Power levels in the lamp are sensed and when a level is exceeded, a control signal is generated. The circuit acts to reduce power in an electronic ballast powering the lamp and keeps the lamp powered down when either one of two fault conditions is sensed in the lamp. Several embodiments are disclosed.

Abstract: A CCFL power converter circuit is provided using a high-efficiency zero-voltage-switching technique that eliminates switching losses associated with the power MOSFETs. An optimal sweeping-frequency technique is used in the CCFL ignition by accounting for the parasitic capacitance in the resonant tank circuit. Additionally, the circuit is self-learning and is adapted to determine the optimum operating frequency for the circuit with a given load. An over-voltage protection circuit can also be provided to ensure that the circuit components are protected in the case of open-lamp condition.

Abstract: A neon sign includes a transformer module and a receptacle attached to the neon sign for receiving the transformer module. The transformer module is configured to mate with the receptacle as the transformer module is plugged into the receptacle in order to connect the transformer module to the neon sign. The transformer module includes a high voltage transformer for transforming a primary input voltage into a secondary high voltage output. The transformer module also includes secondary contacts for connecting the secondary high voltage output of the transformer module to the neon sign when the transformer module is plugged into the receptacle. The receptacle also includes secondary contacts configured to mate with the secondary contacts of the transformer module as the transformer module is plugged into the receptacle thereby electrically connecting the secondary high voltage output of the high voltage transformer to the neon sign.

Abstract: The present invention provides self destruct arrangements for self ballasted fluorescent lamps and lighting fixtures using them. The ballast power supply includes at least one element that breaks down at high temperature. The lamp arrangements are constructed such that there is close proximity between at least one electrode of the lamp and the breakdown element of the ballast power supply. In one embodiment the breakdown element is a FET switch. In another embodiment, the breakdown element is a capacitor.

Abstract: A line dimmer has a limited maximum firing angle to limit a total harmonic distortion within a powering signal. A dimming ballast generates a pulse width modulated signal based on a firing angle of the powering signal, generates a dimming command signal based on the pulse width modulated signal, and dims a lamp based on the dimming command signal. The maximum firing angle may be limited to 30 degrees, 25 degrees, or 20 degrees, for example, to limit a resulting total harmonic distortion.

Abstract: A ballast circuit is provided having an input, an output for coupling to an electric discharge lamp and an oscillation circuit for illuminating the lamp. A circuit may be included for sensing when current from the isolation circuit exceeds acceptable levels, at which point, the ballast circuit may be shut down, limited or otherwise reducing the possibility of ballast failure. In one form of the invention, a current excursion sensor circuit is coupled between the isolation circuit and the output circuit for sensing when the current from the isolation circuit exceeds a given value. Preferably, the ballast circuit is shut down and maintained inactive until such time as any current excursion has a chance to decay away, ballast components have an opportunity to cool off or otherwise return to normal condition or until such other condition has occurred. Preferably, the ballast is shut down upon a current or voltage excursion of such a magnitude at or before components may overheat or begin to fail.

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.

Abstract: In a high-frequency electronic ballast, a screw-in fluorescent lamp is connected with and powered by way of a series-resonant LC circuit. A resistive load is connected with the LC circuit, thereby to constitute a load therefor before ignition of the fluorescent lamp or in case the fluorescent lamp were to fail to ignite.

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: The invention describes a method for the modulation of the light intensity of fluorescent lamps via the supply main by modification of the form and/or the amplitude of the power supply provided. An electronic control element, provided as a component of the logical circuit, temporarily blocks current flow after at least every second zero-crossing of the voltage, dependent upon time and/or voltage. Blocking of the current flow occurs only during the time period in which there is no flow of charging current for the downstream direct-current mains supply circuit. The advantage thus obtained is that the control pulses for the logical circuit do not influence the electric current flowing through the fluorescent lamps.

Abstract: The invention relates to a circuit arrangement for operating at least one discharge lamp (LP) on a half-bridge inverter (Q1, Q2), having at least one coupling capacitor (C3) and having a switch-off device (T1, A) which permanently switches off the half-bridge inverter (Q1, Q2) when the lamp (LP) refuses to start. According to the invention, the circuit arrangement has first and second devices (V1, V2) for monitoring the voltage drop across the at least one coupling capacitor (C3) and for activating the switch-off device (T1, A) as a function of the voltage drop detected across the at least one coupling capacitor (C3). If the voltage across the coupling capacitor (C3) deviates substantially from its normal value, for example owing to the occurrence or the rectifying effect at the end of the service life of the discharge lamp (LP), the half-bridge inverter (Q1, Q2) is shut down by the switch-off device (T1, A).

Abstract: A ballast includes a hot restart circuit for hot restart of a HID lamp. In one embodiment, the hot restart circuit includes inductively coupled first and second inductive elements coupled end to end. A first capacitor has a first terminal coupled to a point between the first and second inductive elements and a second terminal coupled to a switching element. When the switching element transitions to a conductive state, a voltage pulse is generated on the second inductive element and the corresponding pulse on the first inductive element is sufficient to achieve hot restart of the lamp. In one embodiment, the first capacitor and the second inductive provide a parallel resonant LC circuit. The resultant signal on the second inductive element increases a voltage on the first inductive element for hot restart of the lamp.

Abstract: A supply circuit used in electronic ballasts for discharge lamps having an inverter for generating a supply voltage at a specified switching frequency for a load circuit comprising at least one lamp and a resonant circuit in series with the electrodes of the lamp. The supply circuit also includes a control circuit connected to the load circuit and the inverter so as to reduce the supply voltage provided to the load circuit in case of defective operation of the lamp. The control circuit includes a band-pass filter centered on the switching frequency of the inverter, a level discriminator, and a logic circuit. The control circuit receives an input signal that is dependent on the voltage at a point of the load circuit, and it is filtered through a band-pass filter. The output signal from the band-pass filter is provided to the level discriminator, which determines whether the lamp being used is defective by the frequency of the voltage and provides a corresponding high or low signal to the logic circuit.

Abstract: The invention relates to a high-pressure discharge lamp having a base at one end and whose return conductor (13) is protected with the aid of a bidirectional trigger (D) against high induced voltages of the radio interference suppression reactor (L1) connected to the return conductor (13).

Abstract: A lighting apparatus of the present invention includes a discharge lamp incorporating a detecting element having a predetermined electrical characteristic, a detector circuit to discriminate the electrical characteristic of the detecting element and a lighting circuit to light the discharge lamp according to the output from the detector circuit. According to the lighting apparatus of the present invention, it is possible to detect whether a discharge lamp mounted in the socket is an adapted lamp without necessity for lighting the discharge lamp.

Abstract: The invention relates to a circuit arrangement for operating at least one electrodeless discharge lams (LP1) having at least one voltage input (j10, j11) for supplying voltage to the circuit arrangement and electrical terminals (j12, j13) for at least one electrodeless discharge lamp (LP1). The circuit arrangement has supervisory means which ascertain the presence or the absence of the at least one electrodeless discharge lamp (LP1) at the electrical terminals (j12, j13) and enable the provision of the ignition or operating voltage for the at least one electrodeless discharge lamp (LP1) only when the at least one electrodeless discharge lamp (LP1) is connected to the electrical terminals (j12, j13).

Abstract: A power supply for high voltage, low current gas discharge tubes such as neon, argon, and mercury vapor. A free running, flyback oscillator, converts D.C. voltage energy into radio frequency energy by means of a compact, ferrite transformer and associated circuitry. The primary winding is tuned by a resonant capacitor and driven by a power transistor. A high voltage, centertapped winding of a ferrite transformer drives the gas tube load directly. A feedback winding arranged across the transistor base and emitter junction sustains oscillation and controls the drive level of the transistor by means of a regulating circuit which controls the amplitude of the current. Oscillator starting is achieved by means of an on-off switch which supplies a single starting pulse to the power transistor or by means of a time delayed starting pulse.

Abstract: A discharge lamp lighting apparatus according to this invention comprises: an inverting circuit for converting a DC input into a high frequency output; a load circuit which is connected to the inverting circuit and is constructed by a plurality of discharge lamps; a detecting resistor connected between a terminal of the inverting circuit and a ground; an integrating circuit for integrating a voltage generated in the detecting resistor; an operational amplifier which receives an output of the integrating circuit as a negative input, receives a predetermined target value as a positive input, and performs an error amplification; a driver for controlling a switching frequency of the inverting circuit on the basis of an output of the operational amplifier; a frequency detecting comparator which inputs the output of the operational amplifier and whose output value is switched in the case where a frequency converted at an input value exceeds a predetermined value; a control circuit for switching an operating state o

Abstract: A power supply for a xenon arc lamp that will automatically shut down if the lamp current is too high, the lamp voltage is too high, or the lamp requires too many trigger pulses to ignite it. Such conditions indicate faults in the lamp itself and should not be operated this way for safety. Lamp-on and end-of-lamp-life indications are provided to the operator for maintenance. The cooling fan power supply must be normal or the lamp will be shut off or not started. In combination, such provide a lamp system that can safely operate at very high powers.

Abstract: A discharge lamp lighting circuit comprising power control means for executing lighting acceleration control to supply power greater than rated power to a discharge lamp to thereby expedite lighting of the discharge lamp, and constant power control on the discharge lamp with the rated power; and timer means for regulating a time for the lighting acceleration control by the power control means in such a way that the lighting acceleration control does not continue for a predetermined time or longer, at the beginning of the lighting of the discharge lamp or when the status of the discharge lamp after being lit changes.

Abstract: A circuit arrangement for operating a semiconductor light source includes connection terminals for connecting a control unit, an input filter, a converter comprising a control circuit, output terminals for connecting the semiconductor light source, an apparatus CM for removing a leakage current occurring in the control unit in the non-conducting state, and a self-regulating circuit for deactivating the apparatus CM. The circuit arrangement is also provided with a detection circuit for detecting an incorrect functioning of the converter or the semiconductor light source. For this purpose, preferably a minimum voltage and a maximum voltage are detected at the output terminals.

Abstract: When a state for electric discharge is established, switching elements T2 and T3 are turned on so that a machining current J0 from a low-voltage auxiliary DC power source (2) flows between a workpiece (W) and a machining electrode (P). Thereupon, an electric discharge machining current J0 sharply rises as a high voltage is applied from a main DC power source (1). When the switching element T1 is turned off, the electric discharge machining current (J0) reaches its peak value, which is maintained by the current from the auxiliary DC power source (2). When the switching elements T2 and T3 are turned off, a current produced by induced energy is fed back to the main DC power source (1) through diodes D1 and D2, whereupon the machining current sharply falls.

Abstract: A ballast adapted to power a fluorescent lamp as a function of a variable input signal, includes a power stage for providing power to a fluorescent lamp; a control circuit for controlling the power stage as a function of the variable input signal; a control circuit power supply for supplying control power to the control circuit; and a monitor and enabling circuit which permits the ballast to provide power to the lamp only when characteristics of the variable input signal meet predetermined criteria.

Abstract: A ballast circuit 10 for a gas discharge lamp 14, incorporates a shutdown circuit 12 for limiting voltage output of a d.c.-to-a.c. converter 21. The shutdown circuit includes a pair of terminals 66 and 68 connecting across an inductor 48 in order to sense the inductive voltage of the d.c.-to-a.c. converter 21. A rectifier network 70-76 receives the inductor voltage and generates a full-wave rectified voltage. A latch 84 is arranged to receive the rectified voltage and to enter an active state when the rectified voltage is above a pre-determined value. A time delay circuit 118 located between the rectifier network 70-76 and the latch 84 provides an adjustable delay time prior to activation of the latch network. Upon activation of the latch, the inductor voltage is decreased and the ballast circuit 10 is taken out of resonance thereby lowering the voltage and current applied to the resonant circuit 28.

Abstract: A circuit for driving a plurality of light emitting diodes (LEDs) that includes a power supply and a voltage divide circuit utilizing positive and negative temperature coefficient thermistors to boost the drive voltage to the LEDs as the ambient temperature deviates from room temperature, which compensates for increased electrical resistance of the LEDs at low temperatures and decreased LED light output efficiency at high temperatures. The circuit also provides a signal voltage to indicate the drive current through the LEDs, and includes a transistor to shut down the power supply when the signal voltage drops below a predetermined level (i.e. the number of burned out LEDs exceeds a predetermined number). A compensation circuit utilizes a thermistor to boost the signal voltage as the ambient temperature drops to compensate for the characteristic turn-on voltage of the transistor that increases as the temperature of the transistor drops.

Abstract: A back-up power system which can accommodate a standard electrical device that is operable from an alternating current power source when alternating current is available, but is operable by a direct-current to direct-current converter when alternating current is unavailable, the converter being powered by replaceable low voltage battery charged by the alternating current source, with the loss of alternating current being sensed to cause the disconnection of the alternating current source and connection to the low-voltage replaceable battery.

Abstract: An exciter circuit for an ignition system including an igniter plug. The exciter circuit includes an energy storage device comprising a pair of capacitors and a charging circuit for charging the capacitors of energy storage device to a predetermined voltage. The exciter circuit further includes a discharge circuit electrically coupled to the energy storage device and the igniter plug providing a conductive path between the energy storage device and the igniter plug. The exciter circuit periodically energizes the igniter plug by applying an output signal of the discharge circuit to the igniter plug, the output signal having a voltage magnitude sufficient to initiate a spark across electrodes of the igniter plug.

Abstract: A discharge lamp lighting circuit which, in turning on a discharge lamp, when an abnormal condition occurs in a discharge lamp or in the present discharge lamp lighting circuit due to a transient cause, can resume the power supply to the discharge lamp at the time when the present transient abnormal condition cause disappears. The discharge lamp lighting circuit includes lighting control for controlling the lighting of a discharge lamp, an abnormal condition detector for detecting an abnormal condition occurring in the discharge lamp or in the discharge lamp lighting circuit, and a protection circuit which receives a signal from the abnormal condition detector to thereby stop the power supply to the discharge lamp. The protection circuit is composed of first protection unit and second protection unit.

Abstract: A ballast circuit for a gas discharge lamp includes a d.c.-to-a.c. converter circuit with circuitry for coupling to a load circuit, for inducing a.c. current therein. The converter circuit comprises a pair of switches serially connected between a bus conductor at a d.c. voltage and a reference conductor. The voltage between a reference node and a control node of each switch determines the conduction state of the associated switch. The respective reference nodes of the switches are connected together at a common node through which the a.c. current flows, and the respective control nodes of the switches are connected together. The load circuit has circuitry for connecting to a gas discharge lamp and comprises a piezoelectric transformer having a body and including a reference lead connected to one of the bus and reference conductors, an input lead coupled to the common node, and an output lead connected to the lamp.

Abstract: A circuit arrangement for igniting and operating at least two discharge lamps. the circuit is provided with input terminals (K1,K2) for connection to a supply voltage source and a circuit I (SC, S1, S2) coupled to the input terminals for generating a high-frequency voltage from a supply voltage delivered by the supply voltage source. A load branch B is coupled to the circuit I and comprising a first branch A including first terminals (K3,K3') for accommodating a discharge lamp and a first inductive element L1, and a second branch C shunting the first branch A and comprising further terminals (K4,K4') for accommodating a discharge lamp and a second inductive element L2 which is magnetically coupled to the first inductive element L1. A circuit II limits the voltage across branch A and branch C to a first value during the ignition of the discharge lamps.

Abstract: An electronic ballast is provided for the operation of one or more gas discharge lamps. The electronic ballast has at least one inverter half bridge and a driving circuit that prescribes the inverter frequency. In the event of overvoltage across a gas discharge lamp, the driving circuit is brought into a locking state in which it blocks the inverter half bridge. This is performed via a circuit resembling a thyristor, which reduces the supply voltage of the driving circuit below a predetermined value. Provided for the purpose of unlocking and restarting the driving circuit is a detector circuit which detects the insertion of a new gas discharge lamp into its respective holder. This is accomplished by pinpoint detection of a steep pronounced voltage rise at a terminal of a gas discharge lamp which is connected to the intermediate circuit voltage via the filament of the gas discharge lamp.

Abstract: A method and apparatus for efficiently driving a load coupled to a ballast is described. A switching element coupled between a pair of ballast terminals converts a low frequency drive signal to a high frequency drive signal which is provided to the load.

Abstract: A circuit which detects an end-of-lamp life or false lamp condition in a fluorescent lamp being driven by an electronic ballast by indirectly sensing total load power through an analog signal indicative of the operating frequency while controlling lamp power using phase control, and which deactivates the half-bridge driver circuit if the operating frequency exceeds a predetermined maximum frequency. Controlling the lamp power via phase control enables the simple detection of excessive lamp power due to either a symmetrical or an asymmetrical increase in lamp running voltage over the course of the life of the lamp. A simple resistor user-programmable interface which allows flexibility for setting different threshold levels for different ballast/lamp combinations. The circuit is easily implemented in an electronic ballast driver IC (e.g., the IR2158/2159), resulting in the elimination of existing high-voltage-sensing-component methods, reduction of PCB interconnects, and an increase in manufacturability.

Abstract: A MOS gate drive (MGD) integrated circuit drives a pair of MOS gated power semiconductor devices such as are used in a half bridge circuit to drive a load in a resonant power supply circuit or to drive a gas discharge lamp in a ballast circuit. The gate drive circuit includes a protection circuit which protects against damage to the components of the driver circuit when a lamp fails or is removed by disabling both of the driver outputs. When the lamp is replaced, the gate drive circuit restarts the lamp driver circuit without cycling the lamp power switch. The protection circuit disables the driver outputs when a low logic level signal falls below a threshold voltage. The lamp driver circuit is restarted when the low logic level signal exceeds the threshold voltage.

Abstract: Disclosed is an integrated circuit for use in a ballast circuit for supplying a.c. current to a resonant load circuit incorporating a gas discharge lamp and a resonant inductance and capacitance. The integrated circuit comprises a d.c.-to-a.c. converter circuit comprising first and second switches serially connected between a bus pin, for connection to a bus conductor at a d.c. voltage, and a reference pin, for connection to a reference conductor. The switches are connected together at a node connected to a common pin through which the a.c. current flows, have respective control nodes connected to a control pin, and have respective reference nodes. The voltage between the control pin and an associated reference node determines the conduction state of the associated switch. A first embodiment also includes first and second resistors serially connected between the bus and reference pins, with their intermediate node connected to an intermediate pin.

Abstract: The object of the invention in to provide a drive circuit in which a high efficiency can be achieved and with which the voltage spikes reacting on the supply network are virtually zero. For this purpose, the discharge lamp (FL) is connected by its first electrode (E1), by means of a connecting line (VL), to the junction (H) between the emitter resistor (R3) of the first transistor (T1) and the collector of the second transistor (T2) of the high-frequency resonant circuit. The discharge lap (FL) in connected by its second electrode (E2) to the neutral conductor (0). As a result, the supply current with the superimposed control frequency flows via the load. Consequently, voltage spikes are compensated for and the efficiency in considerably increased.

Abstract: A lighting circuit for a discharge lamp is designed in such a way that a detection time for the flicker state of a discharge lamp is not affected by the light-OFF time at the time the discharge lamp flickers without causing a significant increase in cost.

Abstract: A method (100) of controlling an inverter in an electronic ballast for at least one gas discharge lamp protects the inverter from damage due to lamp fault conditions, and provides enhanced noise immunity and multiple ignition attempts for low-temperature lamp starting. The method (100) includes repeating a filament preheating step and a frequency shifting step up to a predetermined number of times in order to facilitate lamp ignition under low-temperature conditions and to verify the legitimacy of a detected lamp fault.

Abstract: A power distribution system in which the loads are connected in series to a current source. At each load, a current source to voltage source convertor provides alternative current paths. A serial power distribution current path includes a modulated switch (e.g. a pulse width modulated switch) to control the amount of power delivered to the load via a load current path. The load current path includes a diode which couples a capacitor across the switch, providing a semi-regulated voltage input to a d.c. to d.c. convertor connected across the capacitor. The d.c. to d.c. convertor provides a regulated output voltage, which is connected to the load. The control circuit for modulating the opening and closing of the switch is connected in parallel across the capacitor.

Abstract: Abnormal states in a high-voltage cable connected to a backlight of a liquid crystal display are detected. This invention includes: a secondary winding of a transformer; a discharge tube connected to the secondary winding of the transformer; means connected to the discharge tube for detecting a tube current; means connected to the secondary winding of the transformer for detecting a transformer current; and abnormal-state detection means for comparing a value of the tube current detected by the tube current detection means with a value of the transformer current detected by the transformer current detection means and interrupting a power supply if a difference greater than a predetermined value is detected. Thus, a case of lighting delayed due to the darkness effect can also be dealt with.

Abstract: A light-emission controlling apparatus including an electric discharge lamp (106) which can emit light, a unit for detecting the light-emission state of the electric discharge lamp (106), such as a light-emission time integrating unit (107) for measuring the integral of the length of time that the electric discharge lamp (106) has emitted light, a comparing unit (1082) for comparing the integral of the length of time that the electric discharge lamp (106) has emitted light which is measured by the light-emission time integrating unit (107) to a reference value, and a light-emission mode selecting unit (1083) for selecting either a first light-emission mode or a second light-emission mode according to a comparison result from the comparing unit (1082) so as to cause the electric discharge lamp (106) to emit light in one light-emission mode selected.

Abstract: A circuit is proposed for the AC voltage operation of a discharge lamp by ans of a coupling capacitor (C3) with a safety disconnection device, connected in series with the lamp for DC current separation, which is characterized by the fact that the safety disconnection device responds to a DC voltage (UC3) at coupling capacitor (C3) by means of a DC current component flowing through the lamp.