Abstract: The illumination intensity of a fluorescent lamp which has cathodes and an ionizable medium separating the cathodes is controlled by a method in which the lamp is ignited once during each half-cycle of applied AC current and is thereafter extinguished during that same half-cycle. The lamp is ignited by creating and applying an ignition voltage pulse of a magnitude greater than a characteristic operating voltage of the ionizable medium between the lamp cathodes. The lamp is extinguished by reducing the voltage between the cathodes to a value less than the operating voltage, at a point prior to a zero crossing of the applied AC current half-cycle in which the lamp was illuminated. Because the extinguishing point occurs prior to the end of the applied AC current half-cycle, the illumination intensity is reduced during each half cycle. The characteristics of the ignition pulse reliably ignite the lamp, thereby allowing extinguishing control on a half-cycle by half-cycle basis.

Abstract: A current flowing through a discharge lamp 4 is detected by a current detecting circuit 5, and the detected current is outputted as a lamp current signal A to a feedback control circuit 7 where a difference between the lamp current signal A and the dimming control signal B is obtained and amplified, and then a simplified signal D is outputted to an adder 12 which adds the amplified signal D to the dimming control signal B to constitute a control signal E. The control signal is fed back to a high frequency power supply 2. When a comparing circuit 15 detects that the light level of the dimming control signal B with respect to the full light becomes higher than or equal to 40% to 60%, the feedback circuit is disconnected by operating a switch 13 provided between an error amplifying circuit 9 and an adder 12 to stop the feedback control.

Abstract: An arrangement for switchably operating one or more gas discharge lamps, such a compact or circline fluorescent lamps, with a single ballast commonly used with a linear fluorescent lamp. One or more capacitors is either in parallel or in series with the gas discharge lamp. When engaged by a switch, the capacitor either shunts or reduces the current to the gas discharge lamp in a manner which allows appropriate starting voltage, appropriate operating current and a plurality of illumination levels of the gas discharge lamp.

Abstract: A power supply for a gas discharge lamp includes a converter, a microprocessor switch control circuit, a driver, a switching network having two MOSFET switches, and an output transformer. A cross conduct inhibit circuit is connected in series between the driver and the switching network to prevent simultaneous operation of the switches. The power supply may further include a ground fault interrupt circuit and a ground continuity detector. A dimming module contains a potentiometer input device to vary the brightness of the lamp. The power supply operates at a preset level until the dimming module is connected. The dimming module cannot be removed without shutting off the power supply. The first and second MOSFETs switch first and second voltages across the transformer, thereby causing first and second drive pulses in the periodic output signal. Between the first and second and the second and first drive pulses are first and second dead times.

Abstract: A wall mountable control panel for controlling power levels delivered to electrical loads, such as lighting loads defining zones, has a zone select switch for scrolling through multiple zones, so as to permit a single control unit (having a power level adjustment switch and a power level display for one zone) in the control panel to be used to separately adjust the power level for, and separately display the power level of, more than one zone. The control panel is capable of controlling M times N zones, where N is the number of control units in the control panel, and where M represents the number of selections that can be made by the zone select switch.

Abstract: A method and apparatus for dimming a lamp in a backlight system of a display device, e.g., liquid crystal display ("LCD"), with a brightness dimming ratio of 10,000:1, which is a factor of 10 better than conventional dimming devices. A switch is provided in an inverter circuit, which has reactive components, that drives the lamp. The is positioned in the inverter circuit such that, when it is closed, the energy stored within the reactive components of the inverter circuit is discharged to ground. In one embodiment, the signals from the power supply are pulse width modulated.

Abstract: A discharge lamp lighting apparatus of the present invention includes an inverter to convert input DC voltage into high frequency voltage and supply the converted high frequency voltage to a discharge lamp having filaments, a preheating circuit to preheat the filaments of the discharge lamp, filament voltage detecting circuits to detect voltage applied between both ends of the filaments of the discharge lamp, and an output control circuit to control the inverter to stop or lower the output of high frequency voltage when the detected result of the filament voltage detecting circuit exceeds a specified value.

Abstract: A microprocessor controlled, electronic ballast operates a lamp at nominal settings and shifts the operation of the ballast away from nominal settings to reduce interference. The shift is randomized by a test--flip--?shift! routine that prevents all ballasts from attempting the same correction at the same time. On DC input voltage, the frequency of the boost controller is varied to reduce EMI. The ballast operates in bands according to the input voltage. Some bands correspond to full brightness, some to a fixed amount of dimming, and some to a variable amount of dimming. In the event of an abrupt change in load, the microprocessor changes the frequency of the inverter, thereby reducing output power and gradually unloading the boost circuit and maintaining power to the microprocessor.

Abstract: A fluorescent lamp flashing circuit is comprised of a fluorescent lamp to which an alternating supply voltage source is connected through a series connected loading reactance device which provides current limiting. The heaters of the fluorescent lamp are independently fed. A switching device disconnects and reconnects the alternating supply voltage at a predetermined frequency rate which is determined by a control circuit which controls a switching device. When the switching device is closed, the fluorescent lamp is bypassed through a full wave rectifier bridge and the reactance device is connected in parallel with the supply voltage source and with a bleeding resistance to load the bridge and to form a resonant circuit to maintain the loading reactance device constant and permitting an energy exchange between the supply voltage source and the loading reactance device in a resonant mode thereby maintaining a sine wave form and minimizing loss.

Abstract: An electronic ballast circuit for igniting, supplying and dimming a gas discharge lamp which comprises an oscillation control circuit, an IR2155 self-oscillating half-bridge driver, a dimming control circuit, a load circuit including at least one gas discharge lamp and an over-current protection circuit, wherein the oscillation control circuit controls a current through the lamp by pulse width modulation of a drive signal during a pre-heating stage and the normal operation to control the dimming of the gas discharge lamp.

Abstract: An electronic ballast for discharge lamps comprises a main resonance circuit for applying a voltage necessary for operating of a discharge lamp having filaments to both ends of the discharge lamp and a filament resonance circuit for supplying a filament current to the filaments, wherein the main resonance circuit and filament resonance circuit have resonance circuits having different resonance characteristics in an output path leading to the discharge lamp and also change their outputs depending on an operating frequency of switching elements. Thereby a filament current and a voltage across the discharge lamp can be set at suitable one of respective operational modes of the discharge lamp according to an operational state of the discharge lamp.

Abstract: The circuit for operating a high-pressure gas discharge lamp (HID) has a ice (ZZU) for ignition-time bridging by switching in a second lamp (GL), the ignition-time bridging device (ZZU) being driven by a signal (S) indicating the operating state of the high-pressure discharge lamp (HID), and the drive signal (S) being an output signal of a power controller (R) of the circuit.

Abstract: An improved discharge lamp driving circuit of a charge-pump type capable of suppressing a ripple in an envelop of a lamp current at the time of dimming the lamp or at a low environmental temperature. The circuit includes an inverter having switching elements Q1 and Q2 for converting a voltage across a smoothing capacitor Ce into a high frequency power which is applied through a resonant circuit to the discharge lamp Ld. A capacitor Cin is connected to one end of the resonant circuit to vary a DC voltage of the output of the rectifier in accordance with a varying instantaneous value of the high frequency current or voltage appearing in the resonant circuit. A control circuit is provided to give a control signal for alternately turning on and off the switching elements Q1 and Q2.

Abstract: A current flowing through a discharge lamp 4 is detected by a current detecting circuit 5, and the detected current is outputted as a lamp current signal A to a feedback control circuit 7 where a difference between the lamp current signal A and the dimming control signal B is obtained and amplified, and then a amplified signal D is outputted to an adder 12 which adds the amplified signal D to the dimming control signal B to constitute a control signal E. The control signal is fed back to a high frequency power supply 2. When a comparing circuit 15 detects that the light level of the dimming control signal B with respect to the full light becomes higher than or equal to 40% to 60%, the feedback circuit is disconnected by operating a switch 13 provided between an error amplifying circuit 9 and an adder 12 to stop the feedback control.

Abstract: A strobe dimmer of which the luminous intensity and color temperature are respectively controllable comprises: a fourfold-voltage rectifier circuit(1) having two twofold-voltage rectifier circuits(11,12) for rectifying an input voltage to twofold or fourfold DC voltage depending on the magnitude of input voltage and applying the rectified input voltage to respective strobe discharge tubes(ST1,ST2,ST3); a high voltage generating circuit(5) for supplying high voltage to respective trigger terminals(Tr) of the strobe discharge tubes(ST1,ST2,ST3) through corresponding trigger coils(LT); a first luminous intensity control circuit(13) connected between a ground terminal(GND) and an output terminal(X) of the fourfold rectifier circuit(1), and connected to respective anode terminals(Ad) of the strobe discharge tubes(ST1,ST3); a second luminous intensity control circuit(13a) connected between the ground terminal(GND) and the output terminal(X) of the fourfold rectifier circuit(1), and connected to respective anode ter

Abstract: A communication method particularly suited for lighting control employs encoding of perturbations in a voltage signal having a fundamental period with a nominal waveform. A control period includes a pre-selected number of fundamental periods of the voltage signal. Different control commands are indicated by imposing a selected perturbation, such as a phase cut, on the nominal waveform with a respective occurrence signature within the control period. The control commands are decoded from the voltage signal by detecting the occurrence signature of the perturbations within each control period. Decoding is accomplished by differentiating the nominal waveform to detect encoded perturbations.

Abstract: An improved ballast circuit controls the power delivered to a three-way dimmable fluorescent lamp for use in European countries and elsewhere where the input voltage is on the order of 220 volts. The ballast circuit comprises passive power factor correction to increase the overall power factor of the circuit to above 95% while also reducing the total harmonic distortion to less than 20%. Adaptations to connect a fluorescent lamp to a three-wire dimming switch are also included.

Abstract: A switching module having a switching circuit which achieves a relatively smooth turn-on conduction transition characteristic and a relatively low power consumption. A controlled transition circuit conducts current to between two of its three terminals when in a fully conductive state. The transition circuit transitions from a non-conductive state to the fully conductive state over a predetermined amount of time to limit the di/dt and the interference signals generated by the di/dt. A low forward voltage conduction circuit also conducts current to the load in a conductive state and diverts current to the transition circuit when in a non-conductive state. The conduction circuit creates a second predetermined voltage across the terminals when in the conductive state which is substantially less than the first predetermined voltage to reduce the power consumption.

Abstract: A power control circuit achieves a relatively smooth turn-on conduction transition characteristic and a relatively low power consumption. A controlled transition circuit conducts current to a load when in a fully conductive state. The transition circuit transitions from a non-conductive state to the fully conductive state over a predetermined amount of time to limit the di/dt and the interference signals generated by the di/dt. A low forward voltage conduction circuit also conducts current to the load in a conductive state and diverts current to the transition circuit when in a non-conductive state. The conduction circuit creates a second predetermined voltage across the terminals when in the conductive state which is substantially less than the first predetermined voltage to reduce the power consumption.

Abstract: A dimming ballast lamp includes a lamp, a ballast circuit for converting AC input power to AC output power, a dimming interface circuit for generating a dimming control signal having a voltage level indicative of a selected dimming level of the lamp and a dimming circuit responsive to the dimming control signal for controlling operation of the ballast circuit. A feedback control circuit detects the lamp voltage and produces a feedback control signal in response to the lamp voltage exceeding a perscribed threshold voltage level. The dimming circuit, responsive to the feedback control signal, controls operation of the ballast circuit so as to increase lamp current thereby increasing the dimming level of the lamp, ensuring low temperature ignition of the lamp and protecting against lamp shutdown.

Abstract: A dimming control circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant half-bridge inverter driven by a pulse-duration-modulated voltage, for providing a high-frequency ac voltage between the lamp electrodes. A combination inductive and capacitive snubber circuit reduces switching losses in the inverter and increases the efficiency of the dimming circuit. A low-voltage transformer connected across the resonant portion of the inverter provides voltage to heat the lamp filaments. The filament voltage is substantially constant over a range of pulse-durations providing a dimming range from about 100% to 1% of full light output. A power supply circuit having a power factor of about 0.95 provides both high-voltage and low-voltage dc power to the dimming circuit with minimal losses. A shutdown circuit is provided to shut off power to the lamp if the dimming circuit is miswired or a ground fault occurs.

Abstract: The present invention features an electronic fluorescent lighting ballast which provides a way to transmit data by modulating the light that is emitted from lamps in a luminaire. The modulation occurs at a sufficiently high frequency, so that it is imperceptible in the range of human vision. Data can be represented in the emitted light by frequency-, phase- or amplitude-modulation. Communication methods can be either simplex or duplex. In the preferred embodiment, a simple modification of the base circuit of a typical, Class D, bipolar, push-pull inverter permits frequency- or phase-modulation of the inverter waveform. This causes modulation of the emitted light from the lamps of the luminaire. The transmission of data through an otherwise conventional lighting luminaire is desirable for many commercial applications. One example of its usage is in the transmission of audio or digital information in a grocery or department store from a centralized computer to display units on store shelves.

Abstract: A control circuit and ballasting means controls the light output of a gas discharge lamp in response to switches that are external to the ballast. The invention provides 3 levels of light output with single or multiple lamps. One embodiment of the invention can be mounted in a standard three-way socket for incandescent lamps. Another embodiment can be used to control multiple lamps in a ceiling-mounted fixture, replacing an inboard/outboard configured multiple ballast circuit. Other embodiments provide circuits that allow conventional dimming ballasts which are designed to be controlled with a low-voltage DC input signal to be controlled by a pair of switches connected to an AC power source.

Abstract: A halogen lamp control circuit assembly in which a light intensity regulating remote controller is used to provide a light intensity control signal to a microprocessor of a master unit for controlling an electronic transformer, causing it to provide an alternative current/12 V output for controlling the operation and light intensity of a halogen lamp and simultaneously driving a first slave unit, the first slave unit being driven to produce an alternative current/12 V output for controlling the operation and light intensity of a respective halogen lamp and simultaneously driving a second slave unit when received an alternative current/12 V output from the master unit, the second slave unit and posterior slave units being operated one after another in the same manner.

Abstract: A discharge lamp operating circuit is connected to a source of alternating current (AC) voltage, and has a discharge lamp and a semi-resonant circuit connected to the source of alternating current voltage and in series with the lamp. A starting circuit for initiating operation of said discharge lamp is also connected in the circuit. The lamp switching maintains the series semi-resonant circuit in oscillation and the series semi-resonant circuit maintains the lamp in operation after operation has been initiated by the starting circuit. Highly efficient energy transfer between inductive and capacitive components of the system result in low loss and high power factor.

Abstract: A non-dimmable electronic ballast has a unique inverter design which eliminates a large percentage of the required components, thereby simplifying and increasing the reliability of the ballast, while decreasing its costs. The ballast can provide power for either two or four fluorescent lamps and has additional safety and protection features which are not available in existing ballasts. A dimmable version is also disclosed with a dimming control at the ballast or which can operate a bank of ballasts with a central, remote dimming control or which can provide a variable output frequency to the ballasts to dim the lamps. There is very little distributed capacitance at the connections from the electronic ballast to the lamps. This feature eliminates points of resonances over the range of frequencies for dimming, thereby eliminating sudden changes in brightness as the frequency is varied.

Abstract: An improved ballast circuit for use with a compact fluorescent lamp includes an EMI filter, a rectifier and a voltage amplification stage, an active resonant circuit, a dimming circuit, and a power factor correction stage which is connected in parallel to a lamp load. In one embodiment, the ballast circuit operates in cooperation with a three way switch to adjust the light output of the lamp to three discrete levels corresponding to each setting of the three way switch. In another embodiment the ballast circuit includes a feedback capacitor which provides a feedback path for a portion of the high frequency current to the rectifier and voltage amplification stage. In still another embodiment, the ballast circuit is configured to accept input from a triac or a SCR device. In all of the embodiments, the dimming circuit works with the active resonant circuit to vary the amount of power that is supplied to the lamp load.

Abstract: The invention relates to a circuit arrangement for operating a lamp (La), provided withballast means (B) for generating a lamp current from a supply voltage,a memory (M) in which a relation between a number of temperature-dependent lamp parameters has been laid down,means (II, IV, Va, Vb) coupled to the memory for changing lamp operation in dependence on the temperature.According to the invention, the temperature-dependent parameters are the voltage across the lamp, the current through the lamp, and the luminous flux of the lamp. The actual luminous flux of the lamp is determined by means of the memory through a measurement of the voltage across the lamp and the current through the lamp. The luminous flux of the lamp can be controlled to a substantially temperature-independent and substantially constant level in that this actual value of the luminous flux is used as a signal in a control loop, with the exclusive use of electrical parameters.

Abstract: A visual warning system for a railway vehicle, particularly a locomotive, to illuminate the tracks or the right of way (sometimes called a ditch). The system has a first lamp and a second lamp. The first lamp is driven by a first lamp driver responsive to a first pulse width modulated signal, and the second lamp driver is driven by a second lamp driver responsive to a second pulse width modulated signal. A controller produces the first and second pulse width modulated signals in which the duty cycle of the first and second pulse width modulated signals is varied between high and low levels to alternatively turn the first and second lamps approximately fully on and approximately fully off. To turn each lamp approximately fully on, the controller increases, step-wise, the duty cycle of the lamp's respective pulse width modulated signal from the low level to the high level. The system may further include a switch for operating a horn on the vehicle.

Abstract: This invention includes a sensor, a time delay trigger circuit, and a power source. The sensor monitors an ambient light level and produces a sensed signal related to the ambient light level. The time delay trigger circuit is in electrical communication with the sensor for determining whether the ambient light level remains reduced below a predetermined level for a specified time. The time delay trigger circuit includes a counter/timer circuit, a comparator circuit, a timing gate circuit, and an output driver. The counter/timer circuit receives the sensed signal from the sensor and initiates a count sequence when the ambient light level is below a predetermined level. The counter/timer circuit provides a count value output representing elapsed time. The comparator circuit includes a plurality of switches used to set the specified time delay. The comparator circuit compares the count value output from the counter/timer circuit with the switches.

Abstract: A back light circuit for a liquid crystal display (LCD) includes: an alternating current (AC) adapter, a battery for supplying a direct current (DC) when the alternating current (AC) adapter is not used, an adapter detecting unit for determining whether or not the alternating current (AC) adapter is being used, a direct current/direct current (DC/DC) converter for providing output of a switched signal, a direct current/alternating current (DC/AC) converter for driving a cold cathode fluorescent lamp (CCFL) by increasing an electric potential, a cold cathode fluorescent lamp (CCFL) operated by the direct current/alternating current (DC/AC) converter, an on/off controller for controlling the direct current/direct current (DC/DC) converter, a brightness controller for controlling the brightness of the cold cathode fluorescent lamp (CCFL), a feedback unit for providing feed back signals to the direct current/direct current (DC/DC) converter, a brightness condition detector for determining the brightness condition

Abstract: A bridge circuit arrangement for the operation of discharge lamps comprises a direct voltage source-supplied inverter (2) whose terminals {8,9) are connected to the series circuit of an inductor (10) and a discharge lamp (11}. By means of the symmetrical arrangement of the capacitor (14) with regard to the branches of the bridge circuit, the asymmetrical pulse load on the operating voltage is minimized and the grid filter {1) can have a simpler design. This allows economical manufacture of the discharge lamp with electronic ballast.

Abstract: A dimmer panel for controlling the intensity of a plurality of electric light sources includes a plurality of dimming circuits. Each dimming circuit has a control circuit, a heat producing controllably conductive power switch such as a triac, and a heat producing coil such as a choke. The power switches and coils are arranged on a corrugated heat sink to minimize component temperatures in the dimming control circuit and of the power switches. The heat producing coils are remotely located from the control circuit and the power switches, so that the heat generated by the coils does not increase the temperature of the components in the control circuit or of the power switches.

Abstract: A gas discharge lamp electronic ballast circuit including a gas discharge lamp (51); a rectifier circuit (11a, 11b, 11c, 11d, 13) responsive to AC power for providing a full wave rectified sinewave voltage across output terminals of the rectifier circuit; a transformer (T1) having a primary winding and a secondary winding; a switching circuit (29) for repetitively connecting the rectifying circuit full wave rectified sinewave voltage to the primary winding; a driving circuit (33, 35, 37, T2, 49) responsive to the secondary winding for driving the lamp with a sinusoidal voltage having a predetermined frequency; a current sensing circuit (39, 41, 45, 47, 43) for sensing an average of peaks of current flowing in the driving circuit; and a pulse width modulation circuit (25) responsive to the full wave rectified sinewave voltage and the current sensing means for pulse width modulating the switching circuit at the predetermined frequency such that the rectifier circuit provides a current having a flattened full wa

Abstract: For energizing remote lamp loads subjected to indeterminate transmission losses, a current regulating power supply is described which delivers a regulated current to the load using for example, a full wave rectifier supplying an unfiltered pulsating voltage to a switching regulator controlled by a feedback loop incorporating a current sensing resistor and pulse width modulator. The supply has a substantially unity power factor, a self-quenching characteristic in the presence of circuit interruptions, and can deliver regulated current to a variety of lamp types.

Abstract: An improved ballast circuit for use with a fluorescent lamp includes an EMI filter, a feedback network, a rectifier and voltage amplification stage, and an active resonant circuit which connects to the lamp load. The ballast circuit includes a magnetic feedback path which couples the resonant circuit to the feedback network. The magnetically coupled feedback network of the improved ballast circuit reduces the non-linear characteristics of the rectifier diodes, thus providing an almost linear load to the input power supply and therefore achieving an improved power factor, on the order of 0.95 or greater. The improved ballast circuit may also include a dimming stage which works with the active resonant circuit to vary the amount of power that is supplied to the lamp load. The dimming stage does not require the addition of parasitic active stages and thus provides a lamp with high electrical efficiency.

Abstract: Step dimming of a fluorescent lamp load through sensing of power line interruptions generated through the toggling of a switch. The number of power line interruptions through toggling produced within a predetermined period of time identifies the level of dimming desired. In the event that interruption of power to the ballast exceeds the predetermined period of time, the lamp load will be reset to a prefixed level of illumination once power is restored.

Abstract: A high frequency electronic ballast (128) having a transformer (104) in which the transformer (104) has a primary winding (106) which is coupled to a secondary winding (108) via a primary flux path (1) from which flux can be diverted by a secondary flux path (2) including an air gap (114) which can be adjustable. Use of the transformer (104) permits load operation from a rectified alternating current power source which can be compensated by a high frequency power supply (192) to present a favorable power factor to the alternating current supply.

Abstract: A light sensitive dimmer switch circuit for controlling the illumination level of a light as a function of the ambient illumination level surrounding the dimmer switch circuit by selectively controlling an AC power signal provided to the light includes a photocell and a phase control circuit. The photocell is responsive to the ambient illumination level and has a conduction state associated therewith. The conduction state changes, in response to the ambient illumination level, such that the photocell effectively exhibits either a substantially open circuit or a substantially short circuit. The phase control circuit selectively varies a conduction phase angle associated with the AC power signal which correspondingly causes a variation in the illumination level of the light.

Abstract: A dimming control system includes dimmer modules which receive dimming level information from a control module. Each dimmer modules includes a microprocessor which provides internal intelligence for controlling power to a load in response to the dimming level information. The control module receives industry standard protocol dimming information from various sources, converts it to dimming level information, and communicates the dimming level information to the dimmer modules through serial communication lines. The dimmer modules and control module are mounted in a rack which includes a backplane having nonvolatile memory device that retains configuration data even if the control module is removed from the rack. The dimmer modules implement a zero cross prediction method which includes detecting an actual zero cross, calculating an error, and adding the error to the period of a line power signal.

Abstract: An electronic drive for fluorescent lamps that includes a feedback loop arrangement where a lumen or intensity setting is compared to the lamp current and the frequency of an inverter is changed to bring the lumen output of the lamp to a level that matches the setting. The bandwidth of the feedback loop is great enough such that the time delay around the feedback loop is faster than prior art designs, and is preferably about 50 microseconds. This fast feedback loop provides the advantage that fluorescent lamps, and especially the more non-linear fluorescent lamps, can to be dimmed down to 10-30% of normal full scale lumen output without extinguishing. The faster feedback loop also prevents flicker when as the lamp is dimmed.

Abstract: The illumination intensity of a fluorescent lamp is controlled in response to control signals generated at a remote location on the power supply conductors of a lamp circuit and decoding those control signals at the fluorescent lamp to control the illumination intensity. A dimming controller is connected in the lamp circuit remote from the lamp and generates first and second control signals indicative of a request to increase or decrease, respectively, the lamp illumination intensity. The control module is connected in the lamp circuit to fluorescent lamp and the control module receives the control signals. The control module continually increases and decreases the illumination intensity of the lamp in response to the first and second control signals, respectively. The illumination intensity is controlled by adjusting a time point within each half-cycle of applied power where the lamp is extinguished.

Abstract: A half-bridge inverter is powered from a constant DC voltage and loaded by way of an L-C circuit that has a natural resonance frequency equal to or lower than the inverter's operating frequency. A gas discharge lamp is disconnectably connected across the tank capacitor of the L-C circuit and, when indeed so connected, is provided with a current-limited high-frequency (30 kHz) voltage. The magnitude of the resulting lamp current decreases as the inverter's operating frequency is increased; which operating frequency is controlled by way of a negative feedback arrangement that causes the frequency to increase as a function of increasing magnitude of the current flowing through the tank capacitor. Thus, particularly with the lamp disconnected, the magnitude of the current flowing through the capacitor--and therefore also the magnitude of the voltage existing across it--will be regulated so as to be lower than it would be in the absence of the negative feedback.

Abstract: A monolithic MOS gate driver chip is described for driving high side and low side power MOSFETs in a gas discharge lamp ballast circuit. The chip includes a timer circuit for generating a square output at the natural frequency of resonance of the lamp ballast. Dead time circuits are provided in the chip to prevent the simultaneous conduction of both high side and low side MOSFETs. The chip may be housed in a right pin DIP package.

Abstract: A circuit for sensing a current in a fluorescent lamp. A control system comprises a buck regulator circuit for supplying a buck current, an inverter circuit for receiving the buck current and for generating a lamp voltage, a circuit for sensing a current in a fluorescent lamp, and a controller for controlling the buck regulator and the inverter. The inverter comprises a Royer-type inverter, a resonant tank, and a transformer. A current flows through a primary winding of the transformer to generate a voltage in a secondary winding of the transformer. The fluorescent lamp is coupled to the secondary winding of the transformer so that the fluorescent lamp is isolated from the remainder of the control system by the transformer. The circuit for sensing the current in the lamp senses a current in the Royer-type inverter which is representative of the current in the lamp. The circuit for sensing the current in the lamp is coupled to the controller for controlling the buck regulator and the inverter.

Abstract: A high density dimmer module controls four separate lighting circuits and provides adequate cooling while maintaining a form factor identical to conventional dimmer modules. The module includes circuit breakers arranged in stacks located adjacent to the front of the module. The circuit breaker stacks are spaced apart to allow cooling air to flow between, and to each side of, the circuit breakers. The air then flows past a power device and four toroidal inductors which are arranged behind and between the stacks. In a preferred embodiment, the module includes an input power connector positioned adjacent the rear periphery of the module chassis, first and second stacks of circuit breakers positioned adjacent the front periphery, four inductors arranged in an arcuate pattern behind the circuit breaker stacks, a power device located adjacent a sidewall of the chassis, and four output load connectors positioned adjacent the rear periphery.

Abstract: An apparatus for retrofitting an HID light fixture is described in several embodiments. The apparatus is coupled in series with the secondary winding and the HID lamp of the HID light fixture. A first retrofit capacitor replaces the light fixture capacitor of the HID light fixture. A switching device is coupled in series with a second retrofit capacitor and couples the first and second retrofit capacitors in parallel in response to a normal power mode control input so that the HID lamp provides normal intensity lighting at normal power. The switching device uncouples the first and second retrofit capacitors from being in parallel in response to a low power mode control input so that the HID lamp provides low intensity lighting at low power.

Abstract: A universal input dimming circuit for coupling an isolated external control signal into a variable output power supply, particularly those used for driving fluorescent lamps. Circuitry is incorporated which allows to discriminate between a DC control voltage or a relatively low-frequency pulsewidth-modulated signal using the same pair of input leads. By appropriate conditioning and waveshaping, the circuit produces a pulsewidth-modulated output which is then coupled across an isolation boundary and then demodulated to provide a command signal to the dimming ballast.

Abstract: The electronic ballast for a gas-discharge lamp includes an inverter. The inverter uses the combination of a step-up transformer, a resonant circuit, and clamping diodes to provide an operational inverter output voltage that is independent of the start-up output voltage of the inverter. During the start-up mode, the step-up transformer is used to provide the start-up voltage for the lamp and the resonant circuit is inactive. Clamping diodes prevent or inhibit the resonant circuit from resonating with potential parasitic capacitances during the start-up mode. During the operational mode, an oscillator is tuned relative to the resonant frequency of a resonant circuit to control the brightness of the fluorescent lamp.

Abstract: A fluorescent discharge lamp has two glow mode electrodes wound around it in a helical fashion. One circuit drives the main electrodes at opposite ends of the lamp at high levels of brightness. Another circuit drives the glow mode electrodes at low levels of brightness, at about 10MHz. At intermediate levels of brightness, both the main electrodes and the glow mode electrodes are driven, the two sets of electrodes being driven for alternate on and off periods with the glow mode electrodes being on when the main electrodes are off and the glow mode electrodes being off when the main electrodes are on.