Abstract: An electronic circuit drives a plurality of LED strings connected in series. The electronic circuit includes a regulation module corresponding to each LED string, with the regulation module connected to the cathode terminal of the corresponding LED string. Each regulation module is further coupled to receive a reference voltage in phase with a rectified a.c. voltage. The regulation modules execute in turn and in sequence a current-regulation phase as a function of a trend of the reference voltage. Each regulation module, when executing the current-regulation phase, functions to regulate the current that flows in the corresponding LED string and in any previous LED strings in the series connection so that the regulated current is proportional to the reference voltage.

Abstract: Provided is a pre-charge circuit and a photovoltaic inverter. The pre-charge circuit includes an alternating current power source, a half-bridge rectifier, an auxiliary charging capacitor, a current limiting device and a controllable switch. The pre-charge circuit is connected to a target charging capacitor to form a voltage doubling rectifier circuit. A direct current side of the half-bridge rectifier is connected in parallel to the target charging capacitor, and an alternating current side of the half-bridge rectifier is connected to one end of the alternating current power source. One end of the auxiliary charging capacitor is connected to any one end of the target charging capacitor, and the other end of the auxiliary charging capacitor is connected to the other end of the alternating current power source.

Abstract: An LED driver circuit provides a direct input line sensing step dimming interface for controlling an LED load. The LED driver circuit includes an input voltage source, a first input line, a second input line, and a neutral line. A diode bridge is coupled to the neutral line and to each of the first line switch and to the second line switch at a side of each opposite to the input voltage source. The LED driver circuit includes a first isolation circuit and a second isolation circuit and a microcontroller having a first sense input and a second sense input. The microcontroller receives at least one of the first sense input and the second sense input from the first and second isolation circuits. The microcontroller controls LED driver circuit output to a load according to the received sense input.

Abstract: Lighting systems and methods implementing toggle control are provided. In one example implementation, a lighting system includes a first LED array having one or more LED devices and a second LED array having one or more LED devices. The system further includes a single throw circuit interrupter configured to receive power from a power source. The system further includes a power conversion circuit configured to convert an input power received via the toggle switch to a power output for the first LED array and the second LED array. The power conversion circuit is configured to control a power distribution ratio between the first LED array and the second LED array based at least in part on a detected toggle input (e.g., a toggle pattern) implemented using the single throw circuit interrupter.

Abstract: A compensating method for a ripple compensation circuit of a power supply is provided. The power supply includes an LLC resonant converter. The LLC resonant converter receives an input voltage and generates an output voltage. Firstly, the output voltage is subtracted from a reference voltage, so that a first error signal is generated. Then, a digital filter is provided to increase a low frequency gain of the first error signal, so that a second error signal is generated. Then, the first error signal and the second signal are added, so that a modulated error signal is generated. Then, a compensation signal is generated to control the LLC resonant converter according to the modulated error signal. Consequently, a low frequency gain of the input voltage is increased and a low frequency ripple of the output voltage is suppressed by an increased voltage loop compensator response.

Abstract: A half bridge is described with at least one transistor having a channel that is capable in a first mode of operation of blocking a substantial voltage in at least one direction, in a second mode of operation of conducting substantial current in one direction through the channel and in a third mode of operation of conducting substantial current in an opposite direction through the channel. The half bridge can have two circuits with such a transistor.

Abstract: Implementations generally relate to lighting control. In one implementation, a method includes receiving signaling modulations from a power line. The method further includes decoding data based on predetermined modulation characteristics of the signaling modulations, where the data includes one or more operational commands. The method further includes modifying performance parameters of one or more LED driver channel circuits based on one or more of the operational commands. In some implementations, the one or more LED driver channel circuits supply modulated drive current to one or more LEDs. In some implementations, the performance parameters effect brightness levels of the one or more LEDs connected to the one or more LED driver channel circuits.

Abstract: A method for controlling an amount of power delivered to an electrical load may include controlling an average magnitude of a load current towards a target load current that ranges from a maximum rated current to a minimum rated current in a normal mode, and controlling the average magnitude of the load current below the minimum rated current in a burst mode. The burst mode may include at least one burst mode period that comprises a first time period associated with an active state and a second time period associated with an inactive state. During the burst mode, the method may include regulating a peak magnitude of the load current towards the minimum rated current during the active state, and stopping the generation of at least one drive signal during the inactive state to control the average magnitude of the load current to be less than the minimum rated current.

Abstract: Systems and methods for dimming control using TRIAC dimmers are provided. An example apparatus for a power conversion system includes: a process-and-drive component configured to receive an input signal and output a drive signal to a switch to affect a current that flows through a primary winding of a power conversion system. The input signal includes a first pulse associated with a first input period and a second pulse associated with a second input period. The drive signal is associated with a first modulation period for the first input period and a second modulation period for the second input period. The process-and-drive component is further configured to: determine the first modulation period for the first input period; change the drive signal between a first logic level and a second logic level at a modulation frequency during the first modulation period; determine the second modulation period for the second input period.

Abstract: The present invention relates to a driving circuit of organic light emitting diode comprising an electricity storage unit having a positive polarity at a first terminal and a negative polarity at a second terminal, and a signal input unit having opposite polarities at the first and second terminals, the signal polarity of the signal input unit being changed according to a preset frequency; a control unit, which causes the first terminal of the signal input unit to transmit negative charges to the anode of the organic light emitting diode and causes the second terminal of the signal input unit to transmit positive charges to the cathode of the organic light emitting diode, when the signal polarity at the first terminal of the signal input unit is negative and the signal polarity of the second terminal thereof is positive, and causes the first terminal of the electricity storage unit to transmit positive charges to the anode of the organic light emitting diode and causes the second terminal of the electricity s

Abstract: A device for providing regulated current to an electrical load comprising a current controller operable at predetermined intervals (clock cycles) to receive:—i. a desired input reference voltage; and ii. a feedback voltage obtained from an electronic switch; wherein the current controller is operable to compare the feedback voltage with the desired input reference voltage and provide regulated current to the electrical load based on calculation of the switch off time of the electronic switch at each clock cycle; the calculation of the switch off time operable to achieve a continuous-conduction-mode (CCM) for the device under normal operating conditions, is disclosed.

Abstract: The present invention relates to an intelligent switch capacitor, which comprises a shell. The shell is provided with a capacitor core internally. A temperature sensor is arranged on the capacitor core. A top end of the capacitor core is connected to an intelligent switch wiring board. The intelligent switch wiring board is connected to a single chip computer, a capacity-switch, a temperature measurement module, a current measurement module and a current harmonic component measurement module, wherein the capacitor switch is connected to the capacitor core in an inner triangle way. Beneficial effects of the present invention are: 1. A switch and a power capacitor are integrated into a whole, which can implement quick capacity-switching and cutting of the switch; 2. The capacitor has an electronic thermal protection function; 3. Possibilities of capacitor damages and power grid accidents caused by resonance of a PFC capacitor in a power grid system are eliminated completely; 4.

Abstract: A discharge lamp driving device includes: a discharge lamp driving unit which supplies drive power to a discharge lamp; and a control unit which controls the discharge lamp driving unit according to a waveform of the drive power. The waveform has n launching periods and a low-power mode lighting period. The n launching periods include a first launching period in which the drive power increases toward refresh power that is equal to or above drive power in a low-power mode and equal to or below rated power, and (n?1) launching periods in which the drive power is maintained at the refresh power. The control unit, in an x-th launching period, supplies the discharge lamp with a drive current having a drive frequency equal to or below a drive frequency of a drive current supplied to the discharge lamp in an (x?1)th launching period.

Abstract: A luminaire comprising a first and second terminal connected to an alternating current power source having a period, a first LED light source electrically coupled to each of the first and second terminals, and a second LED light source electrically coupled to each of the first and second terminals. The first LED light source comprises a first color conversion layer having a first emission latency.

Abstract: A dimming module and a solid state lighting device are shown. The dimming module includes a rectifying circuit, a first driving circuit, and a processing circuit. The rectifying circuit is configured to convert an AC voltage to a rectified voltage. The first driving circuit is configured to receive the rectified voltage to provide a first current so as to drive a first lighting module. The first driving circuit includes a first switch. The first switch turns ON or OFF selectively according to a first control voltage signal so as to control the first current. The processing circuit is configured to receive a dimming command, and adjust the first control voltage signal according to the dimming command. The first control voltage signal is configured to control a phase delay angle and a duty cycle of the first current.

Abstract: A half bridge is described with at least one transistor having a channel that is capable in a first mode of operation of blocking a substantial voltage in at least one direction, in a second mode of operation of conducting substantial current in one direction through the channel and in a third mode of operation of conducting substantial current in an opposite direction through the channel. The half bridge can have two circuits with such a transistor.

Abstract: A preferred embodiment relates to controlling the amount of backlight power in an electronic display to account for the temperature in the backlight cavity. Another embodiment relates to a system for controlling the amount of backlight based on both the temperature of the backlight and the amount of ambient light.

Abstract: The invention proposes a driver circuit (1, 20) for illuminants, particularly LEDs, having: —a circuit (2), such as an inverter in the form of a half-bridge circuit that has a resonant circuit (3), that is clocked by means of at least one switch (FET1, FET2), —a transformer (L2) that follows the resonant circuit (3) and from whose secondary winding (L2b) the illuminants can be supplied with power, and —a control circuit (ST) that clocks the switches (FET1, FET2) of the clocked circuit (2), wherein an actual signal (ILED_PRIM) that indirectly reproduces the current through the illuminants and that is inductively output on the secondary side (L2/2) of the transformer (L2) is fed back to the control circuit (ST), wherein the control circuit (ST) is designed: —to regulate the current through the illuminants by clocking at least one switch (FET1, FET2) of the clocked circuit (2) on the basis of the actual signal (ILED_PRIM), and/or —to use the actual signal (ILED_PRIM) to record a fault state following the seconda

Abstract: A lighting driver includes a processor configured to generate a compensator signal based on a first signal during a constant current mode and based on a second signal during a constant voltage mode. The first signal corresponds to a current through an LED light source coupled to an output of the driver, and the second signal corresponds to a voltage at the output. The driver further includes a controller to control, based on the compensator signal, an amount of power provided to the LED light source. The driver also includes a constant current source circuit to be coupled to the LED light source. During the constant current mode, a flow of the current through the constant current source circuit is disabled, and, during the constant voltage mode, disabling the flow of the current through the constant current source circuit disables a flow of the current through the LED light source.

Abstract: A method of controlling a dimmable light emitting diode (LED) system includes defining two or more dimming regions having respective dimming levels applied to one or more strings of LEDs, continuously supplying a current to the one or more strings of LEDs in a first dimming region, and maintaining an average peak value of the current substantially the same and adjusting a duty cycle of a pulse width modulation (PWM) control signal in a second dimming region to supply the current according to the PWM control signal.

Abstract: A circuit for turning off a power semiconductor switch includes a turn-off transistor coupled to switch a signal for turning off the power semiconductor switch onto a control terminal of the power semiconductor switch and a feedback control loop for controlling a voltage on the control terminal of the power semiconductor switch during turn-off. The feedback loop includes a feedback path to feedback a measurement of the voltage of the control terminal of the power semiconductor switch, a control terminal reference voltage generator to generate a time-dependent reference voltage, an error amplifier to generate an error signal representative of a difference between the voltage of the control terminal and the time-dependent reference voltage, and a forward path to convey the error signal forward for controlling the switching of the signal for turning off the power semiconductor switch onto the control terminal of the power semiconductor switch by the turn-off transistor.

Abstract: A high frequency generating device used in a plasma ignition apparatus according to an embodiment includes a high frequency output unit, an output control unit, a current detecting unit, and an abnormality detecting unit. The high frequency output unit outputs a high frequency. The output control unit shifts a state of the high frequency output unit from a non-output state to an output-ready state of the high frequency. The current detecting unit detects a current that flows through a power-supply path to the high frequency output unit. The abnormality detecting unit detects output abnormality of the high frequency in the non-output state when a value of a current detected by the current detecting unit in the non-output state exceeds a non-output threshold.

Abstract: A power conversion apparatus sets a point between AC input terminals of a full-wave rectifying circuit as an input terminal of an alternating voltage, connects a series circuit of two capacitors between the input terminals, connects a series circuit of two switches between DC output terminals of the full-wave rectifying circuit, connects one end of a series circuit of a third capacitor and an inductor with a midpoint of the two switches, connects the other end thereof with a connection point of two capacitors, connects a positive electrode side terminal of a smoothing capacitor with a DC output terminal of a positive electrode of the full-wave rectifying circuit via a first diode, connects a negative electrode side terminal of the smoothing capacitor with a DC output terminal of a negative electrode of the full-wave rectifying circuit via a second diode for preventing counter current.

Abstract: A half bridge is described with at least one transistor having a channel that is capable in a first mode of operation of blocking a substantial voltage in at least one direction, in a second mode of operation of conducting substantial current in one direction through the channel and in a third mode of operation of conducting substantial current in an opposite direction through the channel. The half bridge can have two circuits with such a transistor.

Abstract: A light modulation device having an image forming area in which a plurality of pixels is arranged, and adapted to modulate incident light, and an illumination device adapted to illuminate the image forming area are provided, and the illumination device has an effective dimming area in which a plurality of dimming parts each capable of individually controlling a light intensity of the light for illuminating the image forming area is arranged, illumination areas illuminated by the light emitted from the dimming parts adjacent to each other out of the plurality of dimming parts partially overlap each other, and the light enters the light modulation device, and the position of the peak of the intensity distribution of the light emitted from the dimming part located on the outermost side of the effective dimming area is located on the outer edge of the image forming area or outside the image forming area.

Abstract: A lamp and an operating method for a lamp with an LED element 22 are described. An electrical circuit with the LED element 22 is covered by a cover member 12. A separation device 28 is provided to mechanically severe the electrical conductor 16a, 16b arrange to supply electrical power to the LED element 22 if the detector element 24 detects a defect of the cover member 12.

Abstract: The present disclosure applies to peak current limitation and also to ensuring that a minimum current condition is not exceeded, that is, that the current through a component remains at or above a desired minimum level. A current limitation circuit compensates for time-induced errors by sampling and holding a current or voltage value at the time when a power switch changes state, deriving a rate of change of the electrical parameter and extrapolating the value over time. The extrapolated value is used for subsequent post-processing such as duty cycle modification of a switching mode DC-DC converter.

Abstract: A method for controlling an illumination system having a plurality of colored light sources, with a plurality of colors including at least a first and a second color different from the first one, the illumination system for emitting illumination light and the sources controlled by control signals to provide respective luminances and hence a luminance and a color point of the system. The method having the steps of measuring at different instants the luminance of the system, determining at each measurement the active light sources and, hence, the emitted colors, determining the different luminances of the different colors and, hence, the variations of the luminance of the system and retro-modifying the control signals to reduce the variations.

Abstract: An LED tube lamp having an LED unit is disclosed. The LED tube lamp includes a control circuit that selectively determines whether to perform a first mode or a second mode of lighting operation according to a state of a property of an external driving signal and a switching circuit coupled to the control circuit and the LED unit. When the control circuit determines to perform the first mode of lighting operation, the control circuit controls the second circuit in a manner such that the switching circuit maintains its on state to allow continual current to flow through the LED unit, until the external driving signal is disconnected from the LED tube lamp, and when the control circuit determines to perform the second mode of lighting operation, the control circuit controls the switching circuit in a manner to regulate the continuity of current to flow through the LED unit by alternately turning on and off the switching circuit.

Abstract: A circuit having a series interconnection of a light-emitting diode (LED) group, a first transistor, a second transistor and a first resistor. The series interconnection has a cathode coupled to a drain terminal of the first transistor and a source terminal of the first transistor is coupled to a first terminal of the first resistor wherein voltage across the first resistor to provide a biasing voltage for the first transistor. A source terminal of the second transistor is coupled to a first terminal of the first resistor wherein voltage across the second resistor provides a biasing voltage for the second transistor and ancillary circuitry bypasses the series interconnection. The ancillary circuitry has a capacitor to provide current to the series interconnection to increase the amount of light emitted during an electrical excitation cycle.

Abstract: Apparatus and associated methods involve operation of an LED light engine in which a relative intensities of selected wavelengths shift as a function of electrical excitation. In an illustrative example, current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level. The diversion current may be smoothly reduced in transition as the excitation current or voltage rises substantially above the predetermined threshold level. A color temperature of the light output may be substantially changed as a predetermined function of the excitation voltage. For example, some embodiments may substantially increase or decrease a color temperature output by a solid state light engine in response to dimming the AC voltage excitation (e.g., by phase-cutting or amplitude modulation).

Abstract: A method and circuit to use light-emitting diodes to emulate the dimming performance of incandescent lighting, and more particularly, to making a circuit that uses only white and deep red light-emitting diodes to achieve a coordinated-color-temperature as a function of dim level that is close to that of an incandescent light being similarly dimmed.

Abstract: An LED tube lamp is disclosed. The LED tube lamp includes an LED module for emitting light, the LED module comprising an LED unit comprising an LED; a rectifying circuit for rectifying an external driving signal to produce a rectified signal; and a mode determination circuit configured to detect a state of a property of the rectified signal, for selectively determining on performing a first mode or a second mode of lighting according to the state of the property of the rectified signal; wherein when the LED tube lamp performs the first mode of lighting, the mode determination circuit allows continual current to flow through the LED unit until the external driving signal is disconnected from the LED tube lamp; and when the LED tube lamp performs the second mode of lighting, the mode determination circuit regulates the continuity of current to flow through the LED unit.

Abstract: An image display apparatus including a light source; a light source control unit configured to control electric power to be supplied to the light source; a light source cooling unit configured to cool the light source; a cooling control unit configured to control the light source cooling unit; an image display device; an illumination optical system configured to introduce light from the light source to the image display device, and a projecting optical system configured to project light modulated by the image display device. When the light source control unit receives a turn-off command, the light source control unit first lowers electric power to be supplied to the light source to a predetermined electric power lower than normal electric power to be supplied when the lamp is on, and then blocks the supply of the electric power to the light source, thereby turning the light source off.

Abstract: Apparatus and associated methods relate to modular series-connectable LED light strings having an input connector and an output connector for electrically communicating power and a control signal, an input control signal being actively level-shifted to a level suitable to a first lighting element of the LED light string. In an illustrative embodiment, the LED light string may have a plurality of series connected lighting elements that generate a series of intermediate supply voltage levels. In some embodiments, the active level shifter may bias the input control signal between an DC voltage level applied to a positive supply pin of the first lighting element and the intermediate supply voltage level generated at the connection of a negative supply pin of the first lighting element and the positive supply pin of the second lighting element. In some embodiments, active level-shifting may advantageously restore the proper bias for a series connected light string.

Abstract: Disclosed are a control circuit and a voltage generation method of an LED lighting apparatus which provides lighting using a rectified voltage. Light emission of the LED lighting apparatus can be implemented through current regulation, a rectified voltage used for light emission can be used to provide a constant voltage required for a peripheral circuit, and a current flowing through a current path formed by the current regulation can be controlled to perform dimming.

Abstract: A light emitting diode (LED) control system may include a LED control system for an aircraft. The LED control system may include an LED power controller, and a solid state power controller (SSPC) that includes a processor in communication with the LED power controller, where the LED power controller and the solid state power controller are integrated onto a single power module. The LED control system is configured to receive DC power from a power source, determine, via the processor, current flow through a series MOSFET element connecting to at least one LED, to control operational voltage across the at least one LED, and adjust, via the processor, a gate voltage of the series MOSFET element with the LED power controller.

Abstract: A power supply apparatus includes a controller that performs the following action and resonance means for creating a resonance state between the power supply apparatus and a plasma generator. That is, the controller changes, when a value of electric power input equal to 100% (or a value of electric power input equal to or more than a threshold % and equal to or less than 100%) of a rated power is instructed, an inverter frequency and obtains an inverter output power factor for each of a plurality of inverter frequencies. Then, the controller determines, as a driving frequency of the inverter, one of the plurality of inverter frequencies at which the inverter output power factor is maximized.

Abstract: An automotive lamp with a lighting device is provided that includes a LED lighting circuit designed to generate a luminous flux on the basis of a driving current, a controlling electrical circuit which provides the driving current on the basis of a reference electrical quantity and of a sensed electrical quantity, and a compensating electrical circuit, which is configured so as to vary the reference electrical quantity by way of a compensation function of the luminous flux predetermined, on the basis of the temperature of the LED lighting circuit. The compensating electrical circuit includes a resistive conditioning electrical device that conditions the compensation function of the luminous flux so as to vary the reference electrical quantity in a predetermined way in response to a change in temperature.

Abstract: Various embodiments relates to a DLP (digital light processing) projector for projecting at least one image on a projection surface. A discharge lamp is driven by a current waveform having at least one first region, to which a first frequency is assigned, and a second region, to which a second frequency is assigned, wherein the first region is established by a first commutation and a following second commutation, wherein the second region is established by the region between the second commutation and a following first commutation, wherein further commutations can occur within the second region, wherein a modulation factor is defined by the ratio of second frequency to first frequency, wherein the modulation factor is at least 3. A method for projecting at least one image is also disclosed.

Abstract: A dimming driver circuit includes a power converting unit, an input voltage detection unit, an output voltage detection unit, a driving unit and a control unit. The power converting unit receives an input voltage. During an operation of the switch of the power converting unit, the input voltage is converted into an output voltage. The driving unit is used for driving the switch. The control unit calculates an on-time period of the switch in an operation cycle according to a first detecting signal, a second detecting signal and a dimming signal. The control unit generates a control signal to the driving unit according to the on-time period. The driving unit adjusts the operation of the first switch so as to control the brightness of the light-emitting diode.

Abstract: A device for assisting the nighttime driving of a motor vehicle fitted with a lighting device for emitting a beam for illuminating the road scene in front of the vehicle, the illumination emitted by the lighting device being variable periodically between a maximum value and a minimum value, the device including at least one variable-transmission screen placed between the road scene and the driver, the coefficient of transmission of the screen being variable periodically between a maximum value and a minimum value, the switching on of at least one light source of the lighting device and the coefficient of transmission of the variable-transmission screen controlled by the control unit, the illumination reaching its maximum value when the coefficient of transmission of the screen reaches its maximum value. The control unit controls a circuit for regulating the power supply and a transmitter of remote control waves toward a receiver.

Abstract: In a preferred embodiment, a voltage converter comprises a voltage converter circuit, an output adjuster and a controller. The controller provides a control signal at a duty ratio determined dynamically by a set of input signals. The dynamic output adjuster determines the set of input signals by adjusting the ac component of an output voltage based on a gain Q. The dynamic output adjuster alleviates dependence on the value of Rc under leading edge modulation in either analog or digital converter systems. In addition to delivering the desired left half plane zero effects, dynamic output adjustment reduces the value of the output ripple. As a result, modern control methods such as input-output linearization can be used to design both boost and buck-boost PWM converters if only left half plane zero effects are present.

Abstract: A circuit arrangement for the protection of at least one component of a two wire electrical current loop, which is connected in series with a burden to an AC/DC electrical current source. The two wire electrical current loop has a rectifier a clock signal producer and a switch. The rectifier forms a DC circuit, wherein the component is connected in the DC circuit and wherein the clock signal producer outputs a clock signal to the switch for clocking the DC circuit. The circuit arrangement has a diode, wherein the conduction direction of the diode points from the anode of the diode to the cathode of the diode. The cathode of the diode is connected to the DC circuit, and the anode of the diode is supplied with a periodic or constant voltage from a first voltage source, and the voltage is at least periodically greater than a predetermined threshold value.

Abstract: A simple, cost-effective and efficient short circuit protection with simple routing of the ground on the PCB is achieved in an asynchronous DC-DC boost converter wherein a voltage sensing controller selectively isolates an input power supply to a load in the event of a short circuit. The controller alleviates need for additional components by utilizing the circuit for under voltage lockout protection and the circuit for overvoltage protection to generate signals for detecting short circuit. A predetermined offset voltage is added to a sensed output voltage to generate a reference voltage that is compared to a sensed input voltage and an output signal having a high state is generated in the event that the reference voltage is less than the sensed input voltage for selectively disabling the source of input power when the output signal is in the high state.

Abstract: An apparatus includes a switched-mode converter circuit having an output configured to be coupled to at least one light-emitting device. The apparatus further includes a control circuit configured to generate a measure of a voltage magnitude of a time-varying voltage applied to an input of the switched-mode converter circuit and a measure of a dimming level to be applied to the at least one light-emitting device. The control circuit is configured to control a switch of the switched-mode converter circuit responsive to the generated measures. The control circuit may be implemented using functional units of a microcontroller.

Abstract: An image display apparatus including a light source; a light source control unit configured to control electric power to be supplied to the light source; a light source cooling unit configured to cool the light source; a cooling control unit configured to control the light source cooling unit; an image display device; an illumination optical system configured to introduce light from the light source to the image display device, and a projecting optical system configured to project light modulated by the image display device. When the light source control unit receives a turn-off command, the light source control unit first lowers electric power to be supplied to the light source to a predetermined electric power lower than normal electric power to be supplied when the lamp is on, and then blocks the supply of the electric power to the light source, thereby turning the light source off.

Abstract: A light source circuit includes light-emitting diodes and a constant current circuit that controls current flowing through light-emitting diodes to a fixed level. A DC power supply circuit outputs a DC voltage having a voltage value capable of causing light-emitting diodes to emit light. A light modulation control unit includes: a MOSFET electrically connected between DC power supply circuit and light source circuit; and a control circuit configured to control MOSFET. Control circuit is configured to turn MOSFET on and off with a duty ratio corresponding to a light modulation level such that DC voltage that is outputted from DC power supply circuit is converted to a square wave voltage, and the square wave voltage is outputted to light source circuit. The square wave voltage has an amplitude equal to the voltage value of the DC voltage that is outputted from DC power supply circuit.

Abstract: A tubular LED bulb includes a circuit board include an AC to DC conversion circuit that provides an output DC current at one of several selectable levels when provided with an AC power source. The DC current is routed through a plurality of LEDs at the selected DC current level. The AC to DC conversion circuit operates responsive to a selection circuit that allows a user to select a level corresponding to a desired light output level. The AC to DC conversion circuit allows the tubular LED bulb to be mounted in a conventional fluorescent light fixture, including a ballast, without regard to polarity. In some embodiments, the circuit board includes jumper blocks to allow multiple circuit boards to be connected in tandem.

Abstract: A lighting device includes: a signal converting circuit which receives a dimming signal that is a rectangular voltage signal, and converts the dimming signal to a DC voltage signal corresponding to a duty ratio of the dimming signal; and a power supply circuit which receives an AC voltage and outputs DC current having a current value corresponding to the DC voltage signal. The signal converting circuit includes a resistor-capacitor (RC) circuit which integrates a signal corresponding to the dimming signal by way of charging and discharging to produce the DC voltage signal, and a time constant of the RC circuit during charging is greater than a time constant of the RC circuit during discharging.