Abstract: A high frequency ballast for a metal halide lamp comprises a controller, a switch, and an oscillator. The controller selectively enables and disables the oscillator via the switch to ignite the lamp. The switch is in a power supply loop of the oscillator and selectively open circuits and close circuits the power supply loop. When the switch close circuits the power supply loop, the oscillator oscillates and provides power to the lamp. When the switch open circuits the power supply loop, the oscillator does not oscillate and does not provide power to the lamp.

Abstract: An LED driver circuit that includes a buck-mode boost converter that provides a regulated output current and that requires only a single connection to each channel of LEDs. The buck-mode boost controller may include a current regulator that includes an integrator. The current regulator may be configured to integrate a difference between a reference signal that is representative of the desired level of the average current through the electronic power switch and a detected signal that is representative of the actual current that is being delivered to the buck-mode boost circuit through the electronic power switch. The reference signal to the integrator may not change during operation of the buck-mode converter. The current regulator may be configured to deactivate the integrator and/or to disconnect the detected signal from the integrator while the electronic power switch is off.

Abstract: The present invention relates to an electronic ballast for operating a lamp (L) which has a Class E converter (T1, L1). When a lamp (L) is connected, the output current of the Class E converter (T1, L1) once a switching element (T1) of the Class E converter (T1, L1) has been switched off has a first and a second half-cycle of opposite polarity. The electronic ballast has a measurement apparatus for measuring the output current and a regulating apparatus for adjusting a switch-on time of the switching element. In this case, the measurement apparatus is designed to determine a first output current value of the first half-cycle and a second output current value of the second half-cycle, wherein the regulating apparatus for adjusting the switch-on time is fed a control variable based on the discrepancy between the two output current values.

Abstract: A method and apparatus are disclosed for providing current to a load. The apparatus includes a full or half bridge switching circuit, including at least one switching element for supplying power to a load when switched on and means for switching a state of the switching element only at a time when a substantially zero voltage is applied across the switching element.

Abstract: An inverter of a liquid crystal display for receiving a power voltage for burst dimming via one power terminal to simultaneously adjust a burst dimming and an analog dimming is disclosed. In the inverter of the liquid crystal display, a burst dimming signal generator receives a triangular-wave signal and a power voltage for burst dimming to generate a burst dimming signal. An analog dimming voltage generator receives the power voltage for burst dimming to generate an analog dimming voltage. And a main controller receives the burst dimming signal and the analog dimming voltage to generate a pulse width modulating signal which is used for generating a driving current of a backlight assembly.

Abstract: An electronic device includes circuitry for driving a light-emitting diode (LED) or other light-emitting semiconductor device.

Abstract: Methods and apparatus for simulating resistive loads, and facilitating series, parallel, and/or series-parallel connections of multiple loads to draw operating power. Current-to-voltage characteristics of loads are altered in a predetermined manner so as to facilitate a predictable and/or desirable behavior of multiple loads drawing power from a power source. Exemplary loads include LED-based light sources and LED-based lighting units. Altered current-to-voltage characteristics may cause a load to appear as a substantially linear or resistive element to the power source, at least over some operating range. In connections of multiple such loads, the voltage across each load is relatively more predictable. In one example, a series connection of multiple loads with altered current-to-voltage characteristics may be operated from a line voltage without requiring a transformer.

Abstract: A ballast system for, and a method of, controlling illumination of a lamp, include a dimmer switch having an actuator settable at different settings corresponding to different output voltages across the dimmer switch, a dimming electronic ballast operatively connected to an electrical power source and to the dimmer switch for dimming the lamp upon setting of the actuator, and a shutdown circuit, preferably provided in the ballast, for measuring the output voltages across the dimmer switch, and for automatically powering the ballast off and, in turn, for turning the lamp off when one of the voltages measured by the shutdown circuit does not exceed a reference voltage that corresponds to one of the settings of the actuator.

Abstract: A safety circuit is provided for a ballast of an electro-luminescent (EL) lamp. The EL lamp had an electrical ground shield on at least a portion thereof and has a separate ground lead. The ballast is an isolated ballast with a line input being isolated from an output. The ballast is constructed and arranged to be electrically connected with the separate ground lead. The circuit includes a current sensing structure constructed and arranged to connect between the separate ground lead and a potential ground of the ballast. In the event a user contacts the EL lamp to replace the EL lamp or contacts a defective EL lamp, the ballast is shut down based on a value of current sensed by the current sensing structure.

Abstract: A dimming buck type light emitting diode (LED) driving apparatus includes a main switch controlling a driving current flowing into an LED; a current detector detecting a driving current flowing into the LED; a power level determination unit determining a level of the driving power; a dimming capacitor for dimming control; a dimming control unit controlling charging and discharging of the dimming capacitor according to a power level determination signal and an enable signal; a reset circuit unit generating a reset signal according to a detection voltage from the current detector and a voltage of the dimming capacitor; a pulse generation unit generating a pulse signal; and a latch set by the pulse signal of the pulse generation unit and reset by the reset signal of the reset circuit unit to generate a switching signal, and turning on and off the main switch using the switching signal.

Abstract: A restart circuit for causing an electronic ballast to perform a restart in response to reconnecting any lamp of a multiple lamp configuration of the electronic ballast to the electronic ballast is disclosed. The electronic ballast includes a filament health check circuit for providing a first current through a monitored filament of the lamps to a controller of the ballast. The controller restarts the electronic ballast when a determined ratio of the first current to a reference current indicates that the monitored filament has been disconnected or broken (i.e., the first current substantially decreases) and is subsequently replaced or reconnected to the ballast (i.e., the first current returns to a predetermined level). The ballast further comprises a dv/dt circuit for reducing the first current for a transient time period in response to reconnecting a filament other than the monitored filament to the ballast, causing the controller to restart the ballast.

Abstract: A hybrid light source comprises a high-efficiency lamp, for example, a fluorescent lamp, and a low-efficiency lamp, for example, a halogen lamp. A control circuit individually controls the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that a total light output of the hybrid light source ranges throughout a dimming range from a minimum total intensity to a maximum total intensity. The high-efficiency lamp is turned off and the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below a transition intensity. The low-efficiency lamp is controlled such that the correlated color temperature of the hybrid light source decreases as the total light intensity is decreased below the transition intensity. The hybrid light source is characterized by a low impedance throughout the dimming range.

Abstract: The power supply of the present invention is composed of: a charge pump circuit (54) that periodically turns on and off a plurality of charge-transfer switches (Q1 to Q4) according to clock signals (c1 and c2), thereby charges and discharges a charge storage capacitor (C1) and thus produces the desired output voltage (Vo) from an input voltage (Vi) to supply it to a load (LED); an output current detection circuit 57 for detecting an output current Io (a reference current (Im) thereof in FIG. 1) to the load; and means (a frequency conversion circuit 52 in FIG. 1) that varies the frequency of the clock signals c1 and c2 based on the result of the detection of the output current Io. With this configuration, it is possible to achieve high electric power efficiency irrespective of the magnitude of a load.

Abstract: An exemplary circuit (200) for driving light sources (211, 212, 213, 214) includes feedback circuits (218, 228, 238, 248), a signal balance circuit, and a controller (250). Each feedback circuit corresponds to a light source and is configured for providing a first feedback signal according to a driving current of the light source. The signal balance circuit is configured for balancing all the first feedback signals and correspondingly generating a second feedback signal. The controller is configured for driving the light sources to illuminate according to the second feedback signal.

Abstract: A universal input voltage device is presented which may receive a wide range of regulated and unregulated input voltages, both DC and a wide range of variable frequency AC, and output a desired regulated current at a desired voltage independent of the fluctuation of input voltage and frequency. The circuit includes a preconditioning input circuit, a Buck converter circuit with over voltage protection, flyback and boost circuits, and a shutdown circuit configured to drive a predetermined electrical or electronic device.

Abstract: A method for driving a gas discharge lamp and relates to a lamp driver circuit for driving a gas discharge lamp. The method includes supplying a current to the gas discharge lamp, reversing the direction of the current supplied to the gas discharge lamp and, substantially simultaneously, generating a relatively high voltage. The generated high voltage serves to prevent a series of re-ignitions of the gas discharge lamp that may lead to visible flickering of the gas discharge lamp or to extinction of the gas discharge lamp.

Abstract: A method and a control apparatus for driving a lamp 14 in a lighting system, in particular a lamp having a fast response to a change of an amount of energy supplied through the lamp, in which a device controller 8 is connected with the lamp 14. The device controller 8 receives data values from a system controller 2 to change a light output level of the lamp 14. Upon receiving a data value which is different from a previously received data value the device controller calculates additional data values and distribute the additional data values in a following time interval to smoothen a transition between different light output levels of the lamp 14.

Abstract: A LED circuit comprises: an inductor, a group of LEDs, a capacitor, a power MOS and a switching circuit. The inductor is connected to a voltage supply and a first node; the group of LEDs is connected to the first node and a ground potential; the capacitor is connected to the first node and a ground potential; the power MOS is connected to the first node and a ground potential, wherein the gate of the power MOS receives a switching signal such that the capacitor is charged when the power MOS is turn on to further turn on the LEDs and the capacitor is discharged when the power MOS is turn off to turn off the LEDs. The switching circuit is to generate the switching signal.

Abstract: Ballasts with crest factor control are provided. During a transition to a given half cycle steady state, the current provided to reach the steady state is varied, such as turned off for a short period. This reduction during the transition may reduce or eliminate overshoot. The crest factor control is active, such as altering the timing or number of on/off/on switchings used to control crest factor. The active control may be based on any information, such as time, lamp voltage feedback, or other lamp dependent feedback.

Abstract: The invention relates to a circuit arrangement which is used to operate a low pressure discharge lamp (EL), wherein the discharge lamp receives power. Said circuit arrangement is embodied in such a manner that power-determination components (C2a, L2a) of the circuit arrangement are embodied in a temperature-dependent manner such that the power consumption of the lamp is limited when the temperature rises. Capacitors (C2a) and throttles (L2a) can be embodied in a temperature-dependent manner in a control circuit (AS) of the circuit arrangement.

Abstract: A limited current circuit of this invention comprising: a transformer that raises an alternating current (AC) power supplied from the digital inverter to an AC voltage of a high voltage to light a lamp; a voltage/current detection unit that detects at least one of the current and voltage supplied to the lamp; an A/D converter that converts the detected voltage/current value of analog to a digital value; and a microcontroller unit (MCU) that induces an LCC check point after the start of a striking process, compares at least one of the output current value and voltage value from the transformer with a preset reference value on the basis of an output signal of the A/D converter and then shuts down the inverter when the output current value or voltage value is determined to be abnormal, wherein the reference value comprises at least one of the current value and voltage value measured at the LCC check point when an object having noninductive resistance is not contacted to the inverter.

Abstract: A driving method for a discharge lamp having two cathodes includes providing a supply input voltage for providing an alternating voltage at the terminals of the cathodes, monitoring a condition of each of the cathodes and measuring a first direct voltage signal of the waveform of the voltage of the lamp that develops when the lamp approaches an ageing condition, deactivating the alternating voltage when a variation of the first direct voltage signal occurs, and supplying a second direct voltage signal proportional to the supply input voltage for deactivating the alternating voltage when a variation of the first direct voltage signal occurs in relation to the second direct voltage signal.

Abstract: An inverter driver integrated circuit (IC) includes a control signal generator generating a first control signal and a second control signal by use of a pulse width modulation oscillator signal, a comparator comparing a half-wave rectified signal of a lamp feedback signal fed back from a lamp with a preset reference signal to output a lamp state signal, a first sensor receiving the lamp state signal and the second control signal to output a first sensing signal, and a second sensor receiving the first sensing signal and the first control signal to output a second sensing signal.

Abstract: A high frequency ballast for a metal halide lamp comprises a controller, a switch, and an oscillator. The controller selectively enables and disables the oscillator via the switch to ignite the lamp. The switch selectively tunes and detunes an inductor of the oscillator by altering an inductance of the inductor. When the inductor is tuned, the oscillator oscillates and provides power to the lamp. When the inductor is detuned, the oscillator does not oscillate and does not provide power to the lamp.

Abstract: A light source device includes first and second electrodes, an arc tube having a main body section having a discharge space in which the first and second electrodes are disposed with a distance and a sealing section disposed on each of the both ends of the main body section, a primary reflecting mirror disposed on the side of the first electrode, a secondary reflecting mirror disposed on the side of the second electrode, and a current drive device that generates an alternating current for causing the discharge between the first and second electrodes, and power control by controlling the alternating current so that supplying energy in an anodic term of the first electrode becomes smaller than supplying energy in a cathode term.

Abstract: There is provided highly efficient discharge lamp lighting apparatus capable of reducing its cost by reducing high withstand voltage components on the secondary side of a high voltage transformer and stabilizing, its circuit operation. A discharge lamp lighting apparatus (1) comprises a high voltage transformer (2), a switching circuit (4) for driving the primary side of the high voltage transformer (2), and a triangular wave generation circuit (15) for determining the operation frequency of the switching circuit (4). The triangular wave generation circuit (15) includes a frequency switching means (25) for switching the operation frequency of the switching circuit (4) between before and after the lighting of a discharge lamp (3). At the secondary side of the high voltage transformer (2), a resonant circuit having a capacitance component consisting of only a parasitic capacitance (CCFL) is also formed.

Abstract: An LED driver circuit and its control circuit for controlling its power switch are provided. The LED driver includes a switch, a PWM controller, a current source and a signal controller. The switch has a first end outputting a driving voltage to at least one LED. The PWM controller provides a PWM signal. The current source provides a driving current flowing through the LED when a dimming control signal is asserted. The signal controller turns off the switch when the dimming control signal is de-asserted and relays the PWM signal from the PWM controller to the switch so that the switch is controlled by the PWM signal when the dimming control signal is asserted.

Abstract: An exemplary power supply circuit (20) includes a scaler (21), a field-effect transistor (23), a pulse width modulation circuit (25), and a capacitor (29). The scaler includes an output port (213). The pulse width modulation circuit includes an input port (251). The input port of the pulse width modulation circuit is grounded via the capacitor. The field-effect transistor includes a gate electrode (231), a source electrode (232), and a drain electrode (233). The gate electrode is connected to the output port of the scaler. The source electrode is grounded. The drain electrode is connected to the input port of the pulse width modulation circuit.

Abstract: A display apparatus and a control method thereof are provided. The inventive method and apparatus improves a response speed of a light source and image quality by minimizing a ripple of a current and reducing a time required to increase/decrease an amount of a current to drive a light source when a light source is turned on and off or a size of a current used to drive a light source is changed.

Abstract: A light-emitting diode driving circuit includes a control circuit, a transistor switch and a compensating circuit. The control circuit receives an oscillating signal to generate a pulse drive signal. The transistor switch is activated by the pulse drive signal such that an inductor is charged by an input voltage, in which the inductor is arranged to deliver an inducting current to at least one light-emitting diode when the transistor switch is deactivated. The compensating circuit is coupled between the control circuit and a capacitor provided for reducing ripples of an output voltage corresponding to the inducting current. The compensating circuit performs a charging and discharging operation along with the capacitor when controlled by a dimming control signal provided to control brightness of the light-emitting diode.

Abstract: An OLED driver for driving at least one organic electroluminescence element and lighting apparatus equipped with the driver. The driver has a direct-current power source and a dimmer. The source alternately applies first voltage and second voltage across the element. The first voltage is approximately equal to drive voltage of the element. The second voltage is lower than the first voltage and higher than barrier voltage of the element. The dimmer controls the source so as to change a ratio of a first term to a second term to dimm the element. The first term is a period of time for which the first voltage is applied across the element. The second term is a period of time for which the second voltage is applied across the element.

Abstract: A power supply circuit includes a power supply input for receiving power from a power supply, a power supply output for supplying power to a load, a voltage reference circuit, and a switch circuit. The voltage reference circuit is connected between the power supply input and the power supply output for regulating voltage of the power supply circuit. The switch circuit is connected to the voltage reference circuit and the power supply output. The voltage reference circuit supplies regulated voltage to the switch circuit. The switch circuit controls current between the power supply input and the power supply output to be changed alternately at a certain frequency, thereby changing power output to the load to save electricity.

Abstract: A ballast controller integrated circuit which executes a specific set of instructions via an integrated state diagram architecture to control a fluorescent lamp or high intensity discharge lamp and protect the ballast. The state diagram architecture controls powering up and down of the IC and the half-bridge circuit driven by the IC, preheating and striking of the lamp, running of the lamp, sensing for numerous possible fault conditions, and recovering from these fault conditions based on the normal maintenance of a lamp, while requiring fewer internal and external components than previous electronic ballasts.

Abstract: An inverter for driving light source is disclosed. The inverter includes a pulse control unit for producing a conduction period signal, a power switch unit driven by the conduction period signal and a power conversion unit for outputting a driving power, wherein a waveform modulation unit is further connected between the power switch unit and the power conversion unit, and the waveform modulation unit obtains the input power from the power switch unit and converts thereof into a modulation power, wherein the modulation power includes a positive edge modulation period with gradually rising voltage peak and a negative edge modulation period with gradually falling voltage peak, with the positive edge modulation period has a duration longer than that of the negative edge modulation period, and the modulation power is transmitted to the power conversion unit for being further converted into the driving power.

Abstract: A device includes at least two circuit branches, each of said at least two circuit branches comprising at least one LED diode. The device comprises a supply circuit that provides an electric supply of said at least two circuit branches and includes a variable resistance. The device comprises a controller coupled to said at least two circuit branches and suitable for varying said resistance in reply to a variation of the current that flows in one of said at least two circuit branches to vary the electric supply of said at least two circuit branches.

Abstract: A driver for a white LED string or a display is provided. The driver includes a boost converter that is arranged to provide an output voltage from a source voltage. Also, the driver includes a sense resistor that is coupled between the output voltage and a feedback voltage. The sense resistor is coupled in series with the white LED string or the display. Further, the boost converter uses the sense voltage across the sense resistor to regulate the output voltage. In one embodiment, the boost converter includes a level shifter that converts the sense voltage into a comparison signal that is referenced to ground. In another embodiment, the converter employs a reference voltage that is referenced to the output voltage.

Abstract: A system and method map dimming levels of a lighting dimmer to light source control signals using a predetermined lighting output function. The dimmer generates a dimmer output signal value. At any particular period of time, the dimmer output signal value represents one of multiple dimming levels. In at least one embodiment, the lighting output function maps the dimmer output signal value to a dimming value different than the dimming level represented by the dimmer output signal value. The lighting output function converts a dimmer output signal values corresponding to measured light levels to perception based light levels. A light source driver operates a light source in accordance with the predetermined lighting output function. The system and method can include a filter to modify at least a set of the dimmer output signal values prior to mapping the dimmer output signal values to a new dimming level.

Abstract: There is provided a backlight driving system for a liquid crystal display that can reduce size and weight of a product because a DC-DC converter is not used when commercial AC power is converted into lamp driving power. A backlight driving system for a liquid crystal display according to an aspect of the invention includes a power supply unit converting commercial alternating current (AC) power into direct current (DC) power having a voltage level set beforehand, an inverter unit converting the DC power from the power supply unit into AC power at a one-to-one conversion ratio set beforehand, a boosting unit boosting the AC power from the inverter unit into lamp lighting power set beforehand; and a lamp group receiving the lamp lighting power from the boosting unit to emit light.

Abstract: A hybrid electronic ballast circuit includes a ballast control, half-bridge driver, and a power switch half-bridge in a single package. The ballast circuit includes a number of fault protections and safety features and is self-oscillating to drive a resonant circuit including a fluorescent lamp. Internal feedback and control signals are provided for a number of modes of operation, including startup, preheat, normal run mode and fault protection response mode. A voltage controlled oscillator adjusts the switching frequency of the switching half-bridge to maintain zero volt switching and minimum current switching. The entire ballast control may have only three external connections, and may be implemented in a TO220 package.

Abstract: A discharge lamp lighting apparatus includes an input power supply, a power supply circuit, a bridge circuit having switching elements that performs AC operation of a discharge lamp, a lighting circuit, a control circuit that controls the power supply circuit, and a drive circuit that drives bridge circuit. An overcurrent suppressing circuit having a resistance element and a switching element connected to the resistance element in parallel therewith is connected between the negative side of the bridge circuit and the negative side of the power supply circuit, so that the overcurrent suppressing circuit automatically adjusts current flowing to the switching elements and suppresses the overcurrent upon starting the discharge lamp.

Abstract: A method and a circuit arrangement for operating a discharge lamp, in particular during the first hours of operation after lamp manufacture, are described. The method and the circuit arrangement are provided in particular for high-pressure gas discharge lamps (HID or high intensity discharge lamps or UHP or ultra high performance lamps). Furthermore, a lighting unit with a discharge lamp and such a circuit arrangement and a projection system with a projection display and such a lighting unit are described. Switching-over between various modes of operation with different operating frequencies serves to avoid that the burning voltage of the lamp drops into a region of a minimum voltage of a lamp driver unit below which the latter can no longer drive the lamp with its rated power or a desired power.

Abstract: Each driver circuit for a six-by-four array of light emitting diodes illuminating a pushbutton switch switches three pairs of the light emitting diodes between series connection and parallel connection based on changes to an applied input voltage. Driving six light emitting diodes instead of only four allows illumination of a larger area and improves power efficiency at higher applied input voltages, while retaining dimming compatibility at low voltage levels. Each driver circuit also includes a rectifier allow illumination of the pushbutton switch with direct current voltages of either polarity. The quiescent current limiting resistance is split into multiple resistors for further improved power efficiency. Each driver circuit also includes a bridge rectifier to allow illumination of the pushbutton switch with direct current voltages of either polarity or alternating current voltages.

Abstract: A system for current and/or temperature control of light fixtures includes a sensor in communication with a light fixture, sense a current flow or a temperature of the light fixture, and communicate an input signal relative to the current flow or the temperature; a variable switch in communication with the light fixture to regulate the current flow of the light fixture in response to a control signal; and a controller in communication with the sensor and the variable switch to monitor the input signal, compare the input signal to a condition, and communicate the control signal to the variable switch to control its operation. A bypass circuit applies a normal current directly to the light fixture should a failure occur with the sensor, the variable switch or the controller.

Abstract: An apparatus according to the present invention provides regulated pulsed current to an LED from a voltage source such as a rectified AC voltage. The present inventions provide methods for delivering regulated pulsed current to an LED from the voltage source.

Abstract: The lamp comprises at least one light-emitting diode and an electronic power switch connected in series between a power source and the light-emitting diode. The electronic power switch is controlled by an electronic processing circuit according to the state of a control button connected to a control input of the electronic processing circuit. The button is connected in parallel to the electronic power switch. To detect and reconstitute the state of the button, the electronic processing circuit periodically applies fine turn-off pulses to a control electrode of the electronic power switch.

Abstract: A low current loss ballast operates a high intensity discharge lamp with or without radioactive krypton. A by-pass capacitor in conjunction with a resonant strike circuit limits high frequency ripple applied to a lamp during continuing operation. Different resistor combinations are connected to drive dual buck converters of the ballast. One combination is used for high frequency operation for striking. Another combination is used during low frequency operation to limit current loss. In a strike mode of operation, combinations of signals at a resonant frequency for striking and subharmonic frequencies are applied to a resonant circuit. The signals at the subharmonic have less than a 50% duty cycle.

Abstract: A detecting device of an inverter system comprises at least one detecting element and at least one comparative unit. The detecting element is electrically connected to any one of the connecting parts of the inverter system to get a voltage signal. The comparative unit generates a control signal to shut the inverter system down when the voltage signal is higher than a reference signal.

Abstract: A ballast control circuit for use with a fluorescent lamp in accordance with an embodiment of the present application includes a voltage controlled oscillator operable to provide an operating signal for the ballast control circuit, wherein a frequency of the operating signal depends on an input voltage provided to the voltage controller oscillator, and a driver circuit operable to provide a first driver signal via a first driver terminal and a second driver signal via a second driver terminal to a first switch and a second switch of a half bridge, respectively, wherein the first switch and the second switch are connected in series across a power source, such that a desired output voltage for powering the fluorescent lamp is provided at a node between the first switch and the second switch. The first control signal and the second control signal control the first switch and the second switch to provide a desired duty cycle and dead time based on the frequency of the operating signal.

Abstract: Methods and apparatus to improve efficiency in cold cathode fluorescent light (CCFL) controllers using a full bridge resonant implementation. The secondary of a transformer drives the CCFL, with the primary of the transformer being driven through a capacitor from a full bridge. The bridge alternately and repetitively connects the capacitor and primary between power supply connections, across one of the power supply connections, between the power supply connections with an alternate polarity and again across one of the power supply connections. Instead of switching from across one of the power supply connections to between the power supply connections when the primary current is near zero, a delay is intentionally imposed before switching. This significantly improves the operating efficiency of a backlighting system. In preferred embodiments, the delay is made power supply voltage dependent.

Abstract: A two-wire dimmer for control of a lighting load from an alternating-current (AC) power source includes a semiconductor switch, a power supply, and a control circuit. The power supply includes an energy storage input capacitor that is able to charge only when the semiconductor switch is non-conductive. The control circuit continuously monitors the voltage on the input capacitor and automatically decreases the maximum allowable conduction time of the semiconductor switch when the voltage falls to a level that will not guarantee proper operation of the power supply. The dimmer of the present invention is able to provide the maximum possible conduction time of the semiconductor switch at high end (i.e., maximum light intensity) while simultaneously ensuring sufficient charging time for proper operation of the power supply, and hence, the dimmer.