Abstract: A circuit arrangement suitable for operating low-pressure mercury discharge lamp by means of a high-frequency current includes circuitry (I) for generating the high-frequency current from a supply voltage, and a modulator (II) for the substantially square-wave modulation of the amplitude of the high-frequency current at a modulation frequency f. The circuit arrangement is further provided with circuitry (V) for limiting the amplitude of the re-ignition voltage across the low-pressure mercury discharge lamp to a voltage Vi. As a result, interference with infrared systems caused by a discharge lamp operated by the circuit arrangement is substantially fully suppressed.

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

Abstract: A dimming circuit having a magnetic forced oscillating means incorporating a transformer having three windings, the second winding being connected across a DC power supply and the third winding being coupled to a fluorescent lamp. The second winding is also coupled to an oscillator circuit incorporating a first resistor, a transistor and the first winding. The circuit also includes a variable resistor serially connected to the first resistor, the variable resistor including a movable arm coupled to the first winding for controlling the frequency of operation and thus the brightness of the lamp.

Abstract: A remotely controllable power control system wherein the power supplied to a load may be varied locally via an actuator, positionable through a continuous range, on a wall control or from a remote location using a remote control device not electrically wired to the wall control. The load control system includes a transmitter and a wall control/receiver, each having a control actuator for adjusting the power supplied to the load. Control can be obtained by either the transmitter or the wall control/receiver immediately upon manipulation of either control actuator, with the adjustment in power level occurring substantially instantaneously. Communication between the transmitter and the wall control/receiver is by digitally encoded infrared signal.

Abstract: A power circuit for a fluorescent discharge lamp comprising a converter for producing a DC output. A voltage controlled oscillator is driven by the output from the converter, the oscillator providing a high voltage output for driving the lamp. The frequency of the output increases and decreases with increases and decreases in the powering voltage from the converter. A current detector detects the current passing through the lamp and controls the output voltage of the converter according to that current to increase the the voltage to strike the lamp and then control the voltage to give the required running current.

Abstract: When a discharge lamp is started, high voltage pulses which superpose the voltage due to LC resonance of a resonance circuit are supplied to the discharge lamp, and breakdown occurs in the discharge lamp. The pulse energy needed for the high voltage pulses is small and the output power of the resonance circuit can be decreased. After the breakdown, the energy needed for the transfer from glow discharge to arc discharge is supplied by the resonance, and the high voltage pulses used to supply the starting energy are allowed to be stopped. Thus, the starting and restriking of a discharge lamp is sure, and the starting circuit for a discharge lamp can be made more compact.

Abstract: An electronic ballast for use with fluorescent lamps including a dimming means consisting of a permanent magnet supported over and in proximity to a dual toroid coil assembly utilized as part of an included inverter circuit included in the ballast. The permanent magnet is movable to control the amount of saturation of the transformers thus determining the width of pulses generated by the transistors included in the inverter circuit and thereby controlling the intensity of light emitted from the fluorescent lamps.

Abstract: The level of brightness of rapid-start fluorescent lighting is modulated over a range from full brightness at 100% lamp power consumption to minimum brightness at near 0% lamp power consumption. Fluorescent lamp brightness is modulated by controlling the amount of time during cycles of voltage application, such as 60 hz, when current flows through the lamp. An input signal voltage in a given range, for example, from 0 to 5 volts dc, is processed to provide an output which controls the duration of current flow. A cut-off circuit prevents any line voltage from being applied to the lamp at chosen values of input voltage. The cut-off circuit contains hysteresis elements which prevents the lamp from fluttering between off and on states. Modules connected to the lamp's heater elements maintain proper heater element voltage to ensure operation of the lamp form 0% to 100% brightness.

Abstract: A high frequency electronic ballast which comprises a variable frequency oscillator (1) having its frequency controlled by inputs (10 to 15). The oscillator (1) providing complementary outputs (16, 17) which controls an inverter (4) via a driver circuit (3). The inverter output is a source for a transformer or choke (5) which directly drives a gas discharge lamp (6). In this way the frequency of operation and hence the illumination of the lamp (6) can be changed by changing the driver (3) frequency by direct control (10 to 15) of the oscillator (1) and the lamp voltage is maintained substantially constant while reducing its current flow.

Abstract: A low cost, high efficiency, dimmable electronic ballast for gas discharge lamps which can be controlled by a traditional phase controlled dimmer is disclosed. This ballast includes a push-pull, parallel resonant, self-oscillating inverter which is comprised of a DC base drive circuit and an adjustable, loosely coupled (between the primary and the secondary) transformer with a pair of magnetic shunts, and a LC filter which has both common and differential mode filter functions to reduce the high frequency interference and improve the power factor. The Q factor of the LC filter will maintain a nearly constant lamp current at low light levels. Wide range dimming (100% to less than 1%) is achieved. A delay start circuit and an overvoltage (open circuit) protection circuit are connected to the LC filter. The overvoltage protection circuit can be connected to either the AC side or DC side of the ballast.

Abstract: A half-bridge inverter is powered from a constant DC voltage and provides an AC output voltage that is--in contrast with the usual squarewave voltage--describable as being a sinusoidal waveform with the tops clipped off at some fixed magnitude; or, described differently, a waveform composed of truncated sinusoidal waves; or, described still differently, a waveform having trapezoidally shaped half-cycles. This AC voltage is applied across the primary winding of a so-called reactance transformer, whose loosely coupled secondary winding is connected across a gas discharge lamp. The internal inductive reactance of the secondary winding constitutes a lamp ballasting means by way of limiting the magnitude of the resulting lamp current to a pre-established desired level.

Abstract: A dimmer with reduced filtering losses is connected into a conductor supplying power to a load from a mains power supply. It conventionally comprises a triac in series with a filter inductor between an input terminal and an output terminal and a circuit generating triggering signals for the triac. To reduce the losses in the inductor, which conventionally is in series with the load at all times but is active only during moments following triggering of the triac, to reduce the amplitude of the transient currents, a second triac triggered by a circuit with a time-delay greater than the time constant defined by the filter capacitor and inductor diverts the load current. An auxiliary low-value inductor attenuates transients due to triggering of the second triac.

Abstract: In an electronic ballast for fluorescent lamps, means are provided by which the lamps are powered at their normal level whenever power line voltage is initially connected to the ballast. However, if the power line voltage is disconnected and then re-connected within about two seconds, the lamps will be powered at a lower-than-normal level; which lower-than-normal level will remain in effect until the power line voltage is once again disconnected and not re-connected until more than about two seconds have passed.

Abstract: A universal dimmer which can be used for both fluorescent lamps having a ballast and for incandescent lamps connected to either an alternating or direct current power supply. The dimmer can be installed in place of a standard wall-mounted light switch and connected to the existing wiring. The dimmer circuitry has a fullwave diode rectifier bridge connected in series with the lamp for converting the alternating current power into direct current. A variable current limiting circuit is connected in series with the DC output of the rectifier bridge and is powered by direct current to control the amount of current supplied through the lamp and ballast. The current limiting circuit includes a power transistor which acts as a variable resistor and controls the lamp current and an operational amplifier coupled with a voltage divider network that establishes a selectively variable reference voltage which controls the amount of current through the lamp.

Abstract: A circuit arrangement for operating a discharge lamp includes a DC-AC converter provided with a branch A having at least one switching element alternately conductive and non-conductive for generating a current of alternating polarity at a frequency f. A load branch B is coupled to the branch A and is provided with lamp connection terminals and with inductive means. A drive circuit E renders the switching element conducting and non-conducting at a frequency f. The drive circuit is provided with a branch D which includes a series circuit of further inductive means and capacitive means, and with a branch C including a variable impedance. The drive circuit is coupled to the inductive means in the load branch B, the branch D is coupled to the switching element in branch A, and the branch C is coupled to the further inductive means in branch D. Branch C also includes inductive means and the variable impedance is a variable resistor. The lamp thus can be dimmed over a wide range by a simple and inexpensive circuit.

Abstract: The present invention and its related methods of operation provide a wide range dimmable high frequency lamp ballast system having a resonant circuit associated with each lamp or lamp set for providing a resonant frequency which is substantially higher than the drive frequency at which the lamp or lamp set is driven, and means for automatically selecting a drive frequency to be a submultiple of the resonant frequency of the resonant circuit, the selection of a submultiple being dependent on lamp operating conditions.

Abstract: A discharge lamp lighting device includes a DC power supplying means which supplies as superposed on a high frequency power fed to a low-tension, mercury-arc discharge lamp a DC power of a level capable of maintaining a discharge upon low light flux lighting, the lamp being thereby made stably lighted to an extremely low level of the flux of light.

Abstract: High-efficiency inverter circuits, particularly half-bridge devices, are especially suitable for energizing gas discharge lamps. The inverters preferably employ a series-connected combination of an inductor and a capacitor to be energized upon periodic transistor conduction. Transistor drive current is preferably provided through the use of at least one saturable inductor to control the transistor inversion frequency to be equal to or higher than the natural resonant frequency of the inductor and capacitor combination. The inverters can develop high output voltages to supply external loads connected to the inductor-capacitor combinations.

Abstract: An electronic ballast including a dimming circuit for use with fluorescent lamps. An electromagnet located adjacent to a dual toroid coil transformer employed as part of a inverter circuit is used to control the saturation of the toroid coil to the control the on and off times of transistors included in the inverter circuitry, to limit saturation thereby controlling the intensity of the light emitted from the fluorescent lamps.

Abstract: An inverter-type fluorescent lamp ballast is powered from the power line by way of a common and either of two (or more) different power leads. When powering the ballast by way of the common and the first one of these two power leads, the power provided to the ballast's fluorescent lamp load is relatively low; when powering the ballast by way of the common and the second one of these two power leads, the power provided to the ballasts's fluorescent lamp load is relatively high. In a lighting system, the power leads from each of several such ballasts are parallel-connected and controllably powered from the power line by way of a combination of two ordinary single-pole single-throw wall switches; such that when one of the two wall switches is in its ON-position, the amount of light provided is relatively low; but when the other one of the two wall switches is in its ON-position, the amount of light provided is relatively high.

Abstract: A remote wireless load control system wherein the power supplied to a load can be varied from a remote location using a remote control device not electrically wired to the load. The load control system includes a transmitter and a receiver, each having a control actuator for adjusting the power supplied to the load. Control can be conferred upon either the transmitter or the receiver immediately upon manipulation of the control switch, with the adjustment in power level occurring substantially instantaneously upon manipulation of the control actuator. Transmission of load level information between transmitter and receiver is by digitally pulse-coded infrared signal.

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

Abstract: An apparatus for operating a discharge lamp is disclosed in which a voltage supplied from a commercial alternating current source is fed to a feedback-controlled, saturable current transformer having a primary winding, secondary windings and control winding and to a self-excited inverter circuit having a rectifier circuit. The discharge lame is lit upon receipt of an AC output obtained through reconversion by the inverter circuit. An impedance circuit varies an impedance so as to control a current in the control winding. The current in the control winding varies in accordance with a varied impedance to vary a saturation time of the variable current transformer in the inverter circuit and hence an output of the inverter circuit.

Abstract: An illumination control apparatus is constituted by a main operation panel for performing dimming control of a plurality of different lighting units, a plurality of dimming terminals for receiving dimming data from the main operation panel, and a pair of transmission lines for connecting the plurality of dimming terminals to the main operation panel. In the dimming terminals, the types of different lighting unit are selected in accordance with the dimming data from the main operation panel. Upon selection of the types, the dimming characteristics of the lighting units are converted into desired dimming characteristics, respectively. Dimming signals corresponding to the lighting units are formed on the basis of the dimming characteristics obtained by the conversion. The formed dimming signals are output to the lighting units. With this operation, dimming outputs from the plurality of different lighting units are controlled in accordance with the dimming data from the main operation panel.

Abstract: A luminous power supply apparatus for driving gas discharge devices and the like with relatively high frequency voltages including an output transformer having a primary winding and a secondary winding across which a device to be powered may be connected, transistorized switches connected to the primary winding for providing pulses of alternating polarity thereto when driving, a pulse width modulator for driving the switches at an RF frequency, and a controller for selecting the width of the drive pulses to control the power applied to the device to be powered. The output transformer is comprised of: a pair of U-shaped core members having their corresponding ends joined together to form a unitary core; a primary winding wound about one side of the core and overlying a first junction of the pair of core members; a secondary winding wound about an opposite side of the core and overlying a second junction of the pair of core members; and potting means having a coefficient of resistance of 3.

Abstract: A dimming ballast system wherein the light output of the lamp is controlled by a remote source. The ballast output voltage is regulated by a voltage control feedback loop, the dimming function being achieved by varying the set point of the control loop. The remote control signal, coded by interrupting the current flow to the ballast for a short period, is processed digitally by a microcomputer which generates information to vary the control set point. Circuit means are provided to control the filament voltage of the fluorescent lamps such that as the lamps are dimmed down, the filament voltage is maintained or slightly increased, thus prolonging lamp life and stabilizing the lamp light output.

Abstract: A dimming device, with a brightness dimming ratio of 1 to 1000, for a fluorescent lamp used for the backlighting of a liquid crystal screen comprises a periodic signal generator for delivering rectangular pulses with an adjustable duty cycle. The pulses are synchronized with the image synchronizing signal of the liquid crystal screen. An alternating voltage generator provides power to the lamp only during the pulses. The decrease in tube efficiency for very short pulses allows the required dimming intensity to be achieved without image flickering.

Abstract: Dimming fluorescent lamp solid-state ballast. The ballast is adapted for automatic sensing and control of lamp temperature to dim the lamp to an optimal operating temperature, such as that at which the light output is a maximum per energy input. The ballast is also adapted for manual continuously adjustable or multi-position stepwise dimming control, which may include such an optimal setting. Other available dimming settings include undimmed or maximum light output, and/or the lamp's minimal sustainable light output.

Abstract: The inverter circuitry requires minimal operating input power, is power factor correcting and may, if desired, include a dimming circuit. The circuitry further includes a runaway protection circuit which is activated upon sensing of a no load condition to place the inverter circuitry in a standby mode of operation.

Abstract: A fluorescent lamp control system operable from either an AC power supply of a first frequency or a power supply of a second frequency and which operates the lamp in a dimmed condition when the power supply is that of the second frequency.

Abstract: A discharge lamp lighting device includes a pair of main switching transistors and a feedback transformer. Each of the main switching transistors has a control electrode to form a push-pull circuit and which is switched on and off responsive to a given oscillating frequency. The feedback transformer has a pair of drive windings and serves to positively feed back the output of the push-pull circuit to each of the control electrodes of the paired main switching transistors. A first control circuit is connected to each of the bases of the main switching transistors and includes a variable impedance element to control the oscillating frequency by varying the impedance of this variable impedance element. A second control circuit has a level shift circuit and serves to control the level of signal applied to the first control circuit so as to change the impedance of the variable impedance element so that the on-off operation of each of the paired main switching transistors can be controlled.

Abstract: A dimming ballast system wherein the light output of the lamp is controlled by a remote source. The ballast output voltage is regulated by a voltage control feedback loop, the dimming function being achieved by varying the set point of the control loop. The remote control signal, coded by interrupting the current flow to the ballast for a short period, is processed digitally by a microcomputer which generates information to vary the control set point. Circuit means are provided to control the filament voltage of the fluorescent lamps such that as the lamps are dimmed down, the filament voltage is maintained or slightly increased, thus prolonging lamp life and stabilizing the lamp light output.

Abstract: A dimming ballast system wherein the light output of the lamp is controlled by a remote source. The ballast output voltage is regulated by a voltage control feedback loop, the dimming function being achieved by varying the set point of the control loop. The remote control signal, coded by interrupting the current flow to the ballast for a short period, is processed digitally by a microcomputer which generates information to vary the control set point. Circuit means are provided to control the filament voltage of the fluorescent lamps such that as the lamps are dimmed down, the filament voltage is maintained or slightly increased, thus prolonging lamp life and stabilizing the lamp light output.

Abstract: A method and apparatus for operating at least one gas discharge lamp includes supplying a gas discharge lamp with high-frequency alternating voltage from an externally controlled lamp generator having an operating frequency being variable for dimming the gas discharge lamp. The state of the gas discharge lamp is monitored. A preheating phase with an ensuing starting phase are provided for firing the gas discharge lamp. The operating frequency of the lamp generator during the preheating phase is adjusted to be greater than a rated frequency in rated operation. The operating frequency at the beginning of the starting phase is reduced until the gas discharge lamp has attained a predetermined state and the operating frequency is subsequently maintained at least at an instantaneous value thereof until the gas discharge lamp fires. The operating frequency at the end of the starting phase is reduced to the rated frequency, thereby initiating rated operation.

Abstract: A power controller device used for dimming fluorescent lights includes a power supply circuit for producing a rectified AC power output, a start pulse generator for producing a start pulse in response to the power output, and a switch energized in response to the start pulse to deliver power to the load. A phase detector is connected with the power supply for generating a synchronized saw-tooth voltage waveform from the rectified power output and a power level control circuit is connected with the power supply for setting a voltage threshold level for controlling the power level supplied to the load. A run pulse generator is connected with the phase detector and the power level control circuit and produces run pulses when the saw-tooth voltage waveform from the phase detector exceeds the voltage threshold level. Timer and restart circuits are also provided. The timer circuit disables the power level control circuit for a pre-determined warm-up period wherein full power is delivered to the light for start-up.

Abstract: A dimming circuit provides power from an ac source to a compact fluorescent lamp. The circuit generally includes a resonant circuit driven by a high-frequency switching inverter and a current feedback control system. The circuit is essentially an ac current source of unusually high impedance and provides substantially symmetrical high-frequency current to the lamp. This allows flicker-free dimming of compact fluorescent lamps over a wide range with good light output stability. A small amount of dc or low-frequency ac current may be simultaneously provided to the lamp. The resulting composite current waveform flowing through the lamp substantially eliminates visible striations over a dimming range from about 100% to 1% of full light output.

Abstract: A control circuit for a dimmer which receives all of its operating power through the control terminals from the dimmer of the fluorescent lamp to which said dimmer is connected.

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

Abstract: Reverse phase-controlled dimming of an a.c.-powered load is accomplished by switching power to the load on and off during each half cycle. In one embodiment of the present invention, power is switched on when line voltage is substantially equal to load voltage and off at a selected time later in the half cycle or at any time that the voltage across the switch exceeds a predetermined value. Preferably, switching is accomplished with a pair of field effect transistors. The load preferably includes a capacitor from load hot to neutral. The present circuit permits quiet dimming of incandescent lamp loads without the need for complex circuitry. It is particularly well adapted for dimming low voltage lamps using a solid state transformer.

Abstract: An apparatus is provided for controlling the charging of a main capacitor of a flash unit. Comparison means detect the timing at which a voltage V across the main capacitor reaches a reference voltage V.sub.1, at which point a flash photograph can be taken. A timer detects whether a predetermined time period has elapsed since the voltage V across the main capacitor reached the reference voltage V.sub.1 so as to stop charging the main capacitor. When the voltage V across the main capacitor drops to the reference voltage V.sub.1, as a result of the phenomenon known as "spontaneous discharge", recharging of the main capacitor occurs and the above process is repeated. When the recharging of the main capacitor has been performed over a predetermined time period or a predetermined number of times, the charging of the main capacitor is stopped.

Abstract: A lighting arrangement comprises:a) an array of plural pairs of series-connected fluorescent lamps, with each lamp pair: i) adapted to be powered from 30 kHz/240 Volt by way of a high-Q series-resonant L-C circuit, ii) receiving cathode heating by way of transformer connected with the 30 kHz/240 Volt, iii) connected in parallel with the capacitor of the L-C circuits and iv) connected in parallel with a circuit protection means operative to limit the magnitude of the voltage that can develop across the capacitor of the L-C circuit as a result of Q-multiplication, and --in response to a control signal, or in case the lamp pair fails to start within a reasonably short time--to place a short circuit across the capacitor;b) a frequency converter connected with a power line and operable to provide the 30 kHz/240 Volt; andc) programming means connected with each circuit protection means and operable: i) before providing 30 kHz/240 Volt to the array, to provide a signal to all circuit protection means, thereby placin

Abstract: An electronic ballast for fluorescent lights is disclosed which includes a pulse width modulation driven inverter with feedback current controlling the pulse width. Ambient light feedback control is provided. The ballast includes a power factor correction pre-regulator for ensuring a high power factor. A pre-heat delay timer allows lamps cathodes to heat before applying driving voltage across the lamps.

Abstract: An apparatus for use in dimming florescent lamps by alternating cathodes operated with pulsating unidirectional arc currents for a duration that is long relative to the filament thermal time constant, but short in relation to the mercury migration time constant of the florescent lamp. The invention provides apparatus using full bridge switching and full bridge clamping topology in a trigger driver as well as a power driver to prevent low voltage power supply "ride up". The invention further provides means for sensing cathode heater current to detect a failed cathode and to control the phase switching to a good cathode if a cathode failure occurs. The invention further provides apparatus for a balanced-to-group ground lamp drive voltage for improved ignition of the lamp plasma and better lamp luminance uniformity when the lamp is operated dimly. A logarithmic amplifier is provided in a closed loop operation for analog compression and also to provide a logarithmic dimming response.

Abstract: A ballast circuit for a gaseous discharge lamp, particularly a neon light, includes a diode bridge rectifier for producing a d-c voltage from an a-c input and a transformer with a secondary winding connected to the lamp and a primary winding connected to the rectifier. A switching circuit is connected to the transformer primary winding for controlling a flow of current therethrough from the rectifier. The switching circuit includes at least one MOSFET having a drain terminal connected to the transformer primary winding and a grounded source terminal. A control circuit is connected to a gate terminal of the MOSFET for controlling the on and off times thereof, the control circuit including a pulse generator for producing a train of pulse-width-modulated rectangular pulses of substantially a single frequency fed to the MOSFET's gate terminal.

Abstract: A high voltage active device such as a power FET is employed in a circuit configuration which maximizes the terminal impedance. This high impedance is placed in series with the gaseous discharge device to be driven. The gaseous discharge device is able to sustain conduction, between pulsed operations, at very low currents due to the very high impedance presented by the FET. A further refinement of the invention provides the supply voltage for the combination of the FET and the gaseous discharge device from a capacitor which can be charged during normal pulse-forming network charging.

Abstract: It is a no-touch lamp to be operated with a proximity-capacition-sensing circuit with lamp shade and waterscape-lamp stand; the lamp mainly comprises a lamp stand and lamp shade. when a person moves closely to the lamp, a signal will be generated, and will be amplified through a capacitance induction circuit so as to control the output of a Triac circuit and to turn on the lamp. The lamp stand is loaded with water and decorative objects, whereby a beautiful waterscape can be provided upon the power is turned on for visual pleasure.

Abstract: A load power control circuit which adjusts the level of power provided by a load in response to changes in the impedance across control terminals includes a control circuit which disconnects the load from the power source when the voltage across the control terminals in within a certain range. The control circuit is particularly useful in controlling fluorescent light fixtures controlled by electronic ballasts because the control circuit avoids the need for a separate on/off switch for the fixtures.

Abstract: A circuit and a method for controlling the dimming of incandescent lights using a pair of antiparallel connected SCRs which are fired at the same frequency as the frequency of the AC line power to achieve phase control of the power supplied to the light. Only one SCR of the pair is utilized in the 0% to 50% brightness range while both SCRs are utilized in the 51% to 100% brightness range.

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

Abstract: A fluorescent lamp controller uses a dimmer circuit having an isolation transformer. The controller applies a high frequency current to the primary winding of the transformer. The secondary winding is coupled to a control input via loading circuitry. A detector circuit supplies a signal to the lamp controller indicative of the resultant loading of the transformer to control lamp intensity.