Abstract: An LED driver includes a voltage detector and a controller. The voltage detector is configured to couple to an LED string comprising a plurality of series-coupled LEDs and to detect a voltage across the LED string to generate a feedback signal. The controller is configured to control an amount of current provided to the LED string in response to the feedback signal, with an amount of power provided to the LED string being substantially constant. The voltage detector can be coupled in parallel with the LED string, and may be a resistor divider. The controller is further configured to couple to a DC-DC converter comprising a switch controlled by the controller and configured to generate an output current and an output voltage coupled to the LED string to provide the amount of power to the LED string.

Abstract: A control device for lights having at least one input wherein a coded resistor can be connected to the input, and having at least one input wherein a passive temperature sensor 20a, 20c, particularly a PTC or an NTC, can be connected to the same. The invention also relates to an arrangement of such a control device and at least one light.

Abstract: Disclosed is an LED fault detection circuit, including a current source, a detection resistor and a first circuit, coupled between an LED string and an LED driving circuit. The current source provides a first current. A first end of the detection resistor is coupled to a node between the LED string and the LED driving circuit, and a second end of the detection resistor is coupled to the current source. The first circuit is coupled to the current source and the detection resistor. After the LED string is driven by the LED driving circuit, a detection current flows through the detection resistor. Then, the first circuit generates a fault detection signal according to the sum of the first current and the detection current. As a response, the LED driving circuit stops driving or continues to drive the LED string according to the fault detection signal.

Abstract: In one example, a system includes a load module, a voltage module, and a controller. The load module is configured to selectively bypass each load unit of a plurality of load units to form a series string of load units. The voltage module is configured to output a voltage across the series string of load units that is based on a target voltage. The controller is configured to output an indication of the target voltage, estimate a time delay for switching one or more load units of the plurality of load units, and output, after outputting the indication of the target voltage for the time delay, a control signal to switch one or more load units of the plurality of load units such that the series string of load units has the target quantity of load units.

Abstract: An apparatus includes a driver circuit configured to control a current through at least one LED responsive to a control signal. The apparatus further includes a modulated oscillator circuit configured to modulate an oscillating signal responsive to a dimming signal and to generate the control signal responsive to the modulated oscillating signal.

Abstract: In at least one embodiment, a light source apparatus includes a discharge lamp with a pair of electrodes and a driving unit that supplies a driving current to the pair of electrodes. The driving unit includes an AC supplier that supplies an alternating current to the pair of electrodes and a DC supplier that supplies a direct current to the pair of electrodes. The AC supplier is configured to alternately repeat an AC supply section in which the alternating current is supplied and an AC stop section in which the supply of the alternating current is stopped. The DC supplier is configured to supply the direct current during a period corresponding to the AC stop section. A frequency of the direct current is not lower than 10 Hz and not higher than 1 kHz.

Abstract: The present disclosure provides a backlight module detection system and a backlight module detection method. The backlight module detection system includes a control unit and a drive unit, the control unit is used for outputting a control signal to the drive unit based on an input code; and the drive unit is used for generating a drive control signal corresponding to the code under the control of the control signal outputted from the control unit, and generating and outputting a drive signal corresponding to the code based on the drive control signal, the drive signal being used for driving a backlight module. The drive signal can be used to drive the backlight module so as to achieve the detection of the backlight module; the backlight module detection system can output the signal required for detecting the backlight module, and has a simple structure and low cost.

Abstract: A lighting apparatus includes a first substrate including a switching circuit, the switching circuit including a first port, a second port and a current control circuit configured to generate a current at the second port of the current control circuit responsive to a varying voltage at the first port. The apparatus further includes a second substrate mounted on the first substrate and including at least two LEDs electrically coupled to the second port of the current control circuit of the first substrate.

Abstract: A power converter circuit for a low power illumination device includes a boost converter circuit, a buck converter circuit, and a control circuit. The control circuit configures the boost converter circuit to alternately operate in a current conducting mode and an off mode, to draw different values of the current from an electric transformer in different periods in the current conducting mode, and to stop drawing current from the electric transformer in the off mode. The control circuit further configures the buck converter circuit to generate the required output signals to the low power illumination device according to the output of the boost converter circuit so that the low power illumination device may function normally.

Abstract: Disclosed is an alternating current dimming drive circuit for an LED, comprising a rectification unit and N stages of LED direct current drive circuits. In the ith stage of LED direct current drive circuit, a first end of the ith voltage sampling unit and an input end of the ith LED light source module directly or indirectly receive the output voltage of the rectification unit; a voltage division end of the ith voltage sampling unit is connected to a second input end of the ith switch unit; and a first input end of the ith switch unit is connected to an output end of the ith LED light source module, and an output end of the ith switch unit, a second end of the ith voltage sampling unit and a second output end of the rectification unit are grounded. When the ith switch unit is switched on, the first to the ith LED light source modules emit light.

Abstract: A driver for driving an LED backlight source is disclosed. The driver includes a boost converter for boosting inputted DC voltage and outputting boosted DC voltage to an LED series circuit having LEDs connected and a resistor in series, a feedback circuit for feeding back voltage across the resistor to a backlight driving circuit, and a control switch controlled by output of the backlight driving circuit depending on feedback voltage of the voltage across the resistor for keeping current flowing through the LED series circuit in a constant current. The driver drives the LED series circuit with a constant current, thereby prolonging lifetime of each LED of the LED series circuit. Furthermore, since a time period which the current flowing through the LED series circuit approaches to constant value is shorter, the driver has advantages over lower power consumption, faster response time and better operating efficiency.

Abstract: A solid state lighting apparatus can include a Light Emitting Diode (LED) string that includes a plurality of light emitting diode (LED) segments that are coupled in series with one another wherein a ratio of respective numbers of LEDs in each of the segments is about equal to a ratio of respective average powers for each of the respective segments. Other configurations are also disclosed.

Abstract: A driver circuit (e.g., an LED driver circuit) provides power to a load (e.g. an LED light source) from a DC power rail. A self-oscillating current fed parallel resonant inverter is configured to connect to the DC power rail, receive DC power from the DC power rail, and provide an AC output signal. A current limiting circuit is connected to the self-oscillating current fed parallel resonant inverter. The current limiting circuit receives the AC output signal from the self-oscillating current fed parallel resonant inverter and provides an AC current signal as a function of the DC current provided to the load by the driver circuit. The rectifier receives the AC current signal from the current limiting circuit and provides a DC current to the load.

Abstract: A gate driver circuit providing a slew-rate controlled gate control signal while minimizing the stretching of the gate control signal relative to the input control pulse. Control logic effects two threshold voltage levels. When the gate control signal is between the two threshold voltage levels, the slew rate of the gate control signal is controlled such that the gate of the transistor being driven is driven softly. When the gate control signal is less than the first threshold voltage level or greater than the second threshold voltage level, the gate of the transistor being driven is driven hard. In one embodiment, the first and second threshold voltage levels are set such that the on/off threshold of the transistor being driven is between the two threshold voltage levels.

Abstract: The invention provides LED backlight source, including: a boost converter, for boosting input voltage and outputting boosted voltage; N parallel LED strings, wherein each LED string including a plurality of series LEDs and receiving boosted voltage; a backlight driving IC, for controlling connection/disconnection of boost converter and determining whether to shut down LED strings other than specific LED string based on voltage at negative terminal of specific LED string; and N control circuits, wherein each control circuit controlling voltage at negative terminal of corresponding LED string not to become zero so that backlight driving IC unable to shut down LED strings other than corresponding LED string. When an LED string becomes open, backlight driving IC cannot shut down LEDs strings other than the open LED string to avoid turning off all LED strings. The invention also provides liquid crystal display with LED backlight source.

Abstract: A driving device comprises a first transistor (B13), a second transistor (B14), and a resistance element. The first transistor (B13) has one terminal receiving a pulsed current and a control terminal connected to the one terminal. The second transistor (B14) has one terminal connected to at least one load, the other terminal connected to a reference potential together with the other terminal of the first transistor (B13), and a control terminal connected to the control terminal of the first transistor (B13). The resistance element is connected between the control terminal of the first transistor (B13) and the other terminal of the first transistor (B13).

Abstract: A circuit arrangement for operating at least a first and a second cascade of LEDs is provided. The LED cascades have a different number of LEDs, which are operated alternately in a manner adapted to the instantaneous value of the rectified AC supply voltage by a suitable drive logic. The cascades are assigned to LED units, wherein each unit includes a driving device for driving the respective cascade. The units are coupled in series between the two input terminals, wherein the input terminals are formed by the output of a rectifier. A linear regulator is provided in series with the cascades, said linear regulator being driven via a voltage divider coupled between the two input terminals. An auxiliary voltage supply is provided for operating the respective driving devices, wherein the auxiliary voltage is generated from the voltage dropped across the linear regulator during the operation of the circuit arrangement.

Abstract: The light emitting device control circuit device 100 in accordance with the disclosure includes a power source V1, a transistor TR1, a light emitting unit EU1, switches S1 to S17, constant current sources CC1 to CC17, and a controller 110. A switching voltage Vs1 is supplied from the controller 110 to turn ON or turn OFF the transistor TR intermittently, a pulse voltage is supplied to a pulse voltage supplying line Y1 connected to a drain terminal D of the transistor TR1. The driving signals SP1 to SP17 are sequentially supplied to the switches S1 to S17 to turn ON or turn OFF them (i.e., time division drive). The light emitting devices A1 to A17 are driven sequentially by a pulse current (i.e., time division drive) when a high voltage is supplied to the pulse voltage supplying line Y1 and when the driving signals SP1 to SP17 are turned ON.

Abstract: A system and method for converting alternating current from at least two types of electronic ballasts for fluorescent bulbs into direct current for an array of LEDs. The device is assembled such that it can fit into existing fluorescent bulb fixtures. Alternating current from a contemplated electronic ballast can have one of two peak-to-peak voltages and the circuitry of the device will convert either alternating current into approximately the same direct current. In doing so, the array of LEDs is illuminated providing an LED alternative to fluorescent light bulbs.

Abstract: A dynamically programmable LED illumination system, method and apparatus provides for a dynamically programming an LED illumination unit including LED bulbs affixed on a circuit board and arranged to providing an animating display (such as a logo, sign, . . . ), where a user can customize the animating display on the LED illumination unit by selecting control signals. LED bulbs in the unit can illuminate or be adjusted such as to provide an animating display to a viewer.

Abstract: A light emitting device is provided which is capable of displaying in desired colors stably by controlling a change in luminance of OLED when an organic light emitting layer is degraded or there is a change in temperature of the surroundings. A reference value for the amount of current flowing into a pixel portion is calculated from data of a video signal. Then, the pixel portion displays an image in accordance with the data of the video signal and the drive current at the time is measured for all of OLEDs in the pixel portion. The two voltage values supplied from a variable power supply to the pixel portion are corrected such that the measured drive current approaches the reference value. With the above structure, lowering of luminance which accompanies degradation of an organic light emitting layer is prevented and a clear image can be displayed as a result.

Abstract: Electronic circuits provide an error signal to control a regulated output voltage signal generated by a controllable DC-DC converter for driving one or more series connected strings of light emitting diodes.

Abstract: An LED lighting system is provided for connection to a variable power source providing input power, the LED lighting system having at least one power analyzing and processing circuitry connecting to the variable power source, and being configured to identify one or more characteristics of the input power, where the characteristics are selected from amplitude, frequency and pulse width of the input power, compare one or more of the characteristics of the input power to preset control criteria either in hardware or software or both to yield a comparison result, and then control the current control circuitry according to the comparison result.

Abstract: Solid state lighting apparatuses are adapted to operate with alternating current (AC) received directly from an AC power source. An exemplary apparatus includes a substrate and multiple sets of one or more solid state light emitters disposed over the substrate. Multiple sets of solid state light emitters are configured to be activated and/or deactivated at different times relevant to one another during portions of an AC cycle, and optionally have different duty cycles. Emitter configurations, color combinations, and/or circuit components reduce perceivable flicker, color shifts, and/or spatial variations in luminous flux. Color temperature and/or beam pattern are adjustable. Multiple emitters are arranged along non-coplanar substrate portions.

Abstract: A driving device includes a power source that converts input power to output power, first and second capacitors connected to an output of the power source, a load selector, and a capacitor selector. The load selector opens/closes circuits of first and second loads connected to the output of the power source to alternately close these circuits such that the second-load circuit is closed after the opening of the first-load circuit. The capacitor selector opens/closes circuits of the first and second capacitors to alternately close these circuits such that the first-capacitor circuit is closed in synchronization with the closing of the first-load circuit, and such that the second-capacitor circuit is closed in synchronization with the closing of the second-load circuit. The capacitor selector opens the first-capacitor circuit after the opening of the first-load circuit.

Abstract: A light emitting element driving device, which flashing-drive a plurality of light emitting element arrays connected in parallel by switching elements connected in series with each of the plurality of light emitting element arrays, the light emitting element driving device including: a current detection unit configured to detect respective currents flowing through each of the plurality of light emitting element arrays as currents of the light emitting element arrays; a selection unit configured to select the smallest current of the light emitting element arrays of the detected currents obtained by the current detection unit; and an output voltage control unit configured to control output voltage supplied to the plurality of light emitting element arrays so that the current of the light emitting element arrays selected by the selection unit becomes a preset reference current value.

Abstract: The disclosure is directed at a configurable light emitting diode (LED) dimmer for controlling a set of light fixture loads comprising: a power circuit; a primary digital controller for controlling the power circuit; a set of output current drivers, each of the set of output current drivers connected to one of the set of light fixture loads for controlling the associated light fixture load; a secondary digital controller for controlling the set of output current drivers; wherein the secondary controller transmits LED control information to control outputs of the set of output current drivers; and wherein the secondary digital controller provides digital feedback control information to the primary digital controller.

Abstract: A compensation method for a light emitting diode (LED) circuit including a first transistor, a second transistor, a capacitor, and a LED is illustrated. A first end as a control end of the first transistor is connected to one end of the second transistor and the capacitor, and a second end of the first transistor is connected to the LED. A width to length (W/L) ratio of the second transistor is less than one. An initial control voltage is applied to a control end of the second transistor, and the current output voltage of the LED is correspondingly measured. If a difference between the current output voltage and an initial output voltage exceeds a predetermined value, a compensation voltage, which is a summation of the initial control voltage and the difference, is applied to the control end of the second transistor.

Abstract: A supplemental dimming circuit for an electronic led driver comprising a universal control section has a VCC3 startup and low conduction period circuit for providing a current during start-up and during low conduction periods; a CC hold current circuit for providing a hold current for the dimmer at low conduction periods; a latch circuit for providing a current draw latch on; and a PWM synchronized dimming circuit for providing a PWM signal dependent on the conduction period of the dimmer in real time. The supplemental dimming circuit also has a socket and a plug. The universal control section is on a daughter board that is pluggable to the socket. The VCC3 startup and low conduction period circuit creates a low AC voltage dummy load, which is a resistive load. The CC hold current circuit creates a low AC current dummy load that is a constant current load.

Abstract: Various embodiments of the invention allow for active AC ripple noise cancellation. In certain embodiments, noise cancellation is accomplished by modulating an LED driver output in a polarity opposite to the ripple, thereby, preventing interference with ripple-sensitive loads. Certain embodiments take advantage of a filter network to prevent the LED driver from modulating LED current in response to ripple that falls within a visible frequency range so as to prevent flicker in an LED backlight display. In addition to protecting ripple-sensitive loads from large ripple currents, efficiency is increased by reducing both I2·R losses and peak currents, thereby, extending the useful battery life time in mobile devices.

Abstract: According to one embodiment, a rectifying circuit includes a diode, a switching element, a capacitor and an auxiliary winding. The diode is connected between a first terminal and a second terminal while a direction directed from the second terminal to the first terminal is a forward direction. The switching element includes a first main electrode connected to the first terminal, a second main electrode connected to a cathode of the diode, and a gate electrode connected to an anode of the diode. The auxiliary winding is magnetically coupled to an inductor. The auxiliary winding is connected to the gate electrode through the capacitor, and is connected to the second main electrode of the switching element and the cathode of the diode.

Abstract: A display device includes a display panel having a plurality of pixels for displaying an image, a light source on the display panel, and a light source driving circuit configured to drive the light source. The light source driving circuit for driving a light source includes a driving voltage generator configured to supply power to a light source, and a light source controller configured to generate a light source control signal for periodically turning on/off the light source, the light source being turned on again before being turned off completely.

Abstract: An LED driver has a power supply configured to receive power from a power input. A primary controller configured to receive power from the power supply and output power to a power output. The power output is configured to be connected to LED lights. A dimmer provides a dimming signal, and the dimmer has an adjustable voltage circuit. An offset voltage is added to a ground path on the adjustable voltage circuit. The offset voltage can be created by a silicon diode adding the offset voltage to a transformer's secondary winding ground path on a DC regulated voltage circuit. The adjustable voltage circuit can be formed as the DC regulated voltage circuit. The DC regulated voltage circuit is a 10 VDC regulated voltage circuit.

Abstract: According to one embodiment, a power supply for lighting includes a rectifying circuit, a smoothing capacitor, and a current control circuit. The rectifying circuit rectifies a phase-controlled alternating-current voltage supplied to between a pair of input terminals. The smoothing capacitor is connected to a high-potential terminal and a low-potential terminal of the rectifying circuit. A first electric current flows to the current control circuit in a period when an absolute value of the alternating-current voltage is lower than a specified value. After a second electric current larger than the first electric current flows when the absolute value of the alternating-current voltage increases to be equal to or larger than the specified value, the current control circuit is shut off to reduce a current value to be smaller than the second electric current until the absolute value of the alternating-current voltage decreases to be lower than the specified value.

Abstract: Disclosed is a constant current drive for an LED light source, including a main power supply loop and at least one backup power supply loop. The main power supply loop at least includes a power conversion circuit. The power conversion circuit outputs a constant current to an LED light source. The backup power supply loop at least includes a power conversion backup circuit. The power conversion backup circuit outputs a constant current to the LED light source. When the power conversion circuit and the power conversion backup circuit operate normally, any one thereof operates in a nominal state or a derating state, and the output ends thereof are connected in parallel and then supply power to the LED light source simultaneously. When any one of the power conversion circuit and the power conversion backup circuit is invalid, the invalid circuit will not affect the normal operation of the remaining circuit.

Abstract: A pixel circuit, display device, and method of driving a pixel circuit enabling source-follower output with no deterioration of luminance even with a change of the current-voltage characteristic of the light emitting element along with elapse, enabling a source-follower circuit of n-channel transistors, and able to use an n-channel transistor as an EL drive transistor while using current anode-cathode electrodes, wherein a source of a TFT 111 as a drive transistor is connected to an anode of a light emitting element 114, a drain is connected to a power source potential VCC, a capacitor C111 is connected between a gate and source of the TFT 111, and a source potential of the TFT 111 is connected to a fixed potential through a TFT 113 as a switching transistor.

Abstract: A switch is disclosed. In some examples, a switch includes a generally cylindrical housing; one or more sets of contact points enclosed by the housing; an indicator module, such as a multi-color LED illuminator, also enclosed by the housing; and a pushbutton actuator disposed to operate the contact points. The housing includes a display section spanning substantially the entire circumference of the housing such that the indication made by the indicator module is visible from all radial directions. When the pushbutton actuator is pressed, some of the contact points open to cut off power from hazards, while others are reconfigured to change the state of the indicator module to indicate the changed status of the switch. Multiple switches can be interfaced with each other, such as by serial connection, to facilitate multi-switch safety environment. Modular cables can be used to conveniently establish the interface.

Abstract: A solid state lighting switch can include a first input control that can be configured to adjust a dimming indication or color indication for a solid state lighting fixture that is configured for coupling to the solid state lighting switch. A selective linking mechanism can be configured to activate a linked mode of operation of the switch to link the dimming indication to the color indication or to activate an unlinked mode of operation of the switch to unlink the dimming indication from the color indication.

Abstract: The present invention provides a LED device with voltage-limiting unit and voltage-equalizing and current-limiting resistances, in which a LED is connected in parallel with a voltage-limiting unit, and a current-limiting resistance is connected in series between the LED and the voltage-limiting unit, and two ends of each LED are connected in parallel with an voltage-equalizing resistance for forming a light-emitting unit, so that a light-emitting unit set can be structured through connecting two or more than two of the mentioned light-emitting units in series or in series-parallel in the same polarity; with the two ends of each LED being connected in parallel with the voltage-equalizing resistance, the end voltage of each light-emitting unit can be evenly stabilized; and the current-limiting resistance is connected in series between the connection joints of the LED and the voltage-limiting unit for limiting the shunt current passing through the voltage-limiting unit.

Abstract: One aspect of the present invention includes a light-emitting diode (LED) power supply system. The system includes an LED regulator configured to monitor at least one LED voltage associated with a respective at least one activated LED string and to generate an LED regulation voltage based on the at least one LED voltage relative to an LED power voltage that provides power to the at least one activated LED string. The system also includes a power converter configured to generate the LED power voltage and to regulate the LED power voltage based on the LED regulation voltage.

Abstract: Systems and methods for gathering data relating to time, personnel tasks, personnel awareness levels, and lighting and regulating the levels of white light or blue light in a command center to optimize personnel awareness, accuracy, and effectiveness. Systems and methods for optimum delivery of blue light for ambient, display and task or spot illumination via specialized fixtures, timing, and regulation to optimize alertness and efficiency in a 24-hour command center setting.

Abstract: An LED driving device includes a DC to DC converter module and a driving module. The DC to DC converter module includes a full-bridge switching circuit for converting a first DC electric power into an AC electric power, a rectifier circuit for converting the AC electric power into a second DC electric power, and a control circuit for modulating pulse phase of the second DC electric power and for controlling switching operation of the full-bridge switching circuit, such that the second DC electric power has a predetermined voltage value. The driving module is operable to receive the second DC electric power, to output a third DC electric power with a predetermined current value for driving an LED module, and to modulate pulse width of the third DC electric power.

Abstract: A power converter circuit for a low power illumination device includes a boost converter circuit, a buck converter circuit, and a control circuit. The control circuit configures the boost converter circuit to alternately operate in a current conducting mode and an off mode, to draw different values of the current from an electric transformer in different periods in the current conducting mode, and to stop drawing current from the electric transformer in the off mode. The control circuit further configures the buck converter circuit to generate the required output signals to the low power illumination device according to the output of the boost converter circuit so that the low power illumination device may function normally.

Abstract: A power converter circuit of a low power illumination device includes a boost converter circuit, a buck converter circuit, and a control circuit, for cooperating with a dimmer and an electric transformer. The control circuit configures the boost converter circuit to alternatively operate in a current conducting mode and an off mode, to draw current from the electric transformer in the current conducting mode, and to stop drawing current from the electric transformer in the off mode. The control circuit further configures the buck converter circuit to generate the required output signals to the low power illumination device according to the configuration of the dimmer so that the low power illumination device may perform the required dimming function.

Abstract: Methods and apparatus are provided to fabricate massive monolithic arrays of individually addressable light emitting diodes, assemble a plurality of such massive monolithic arrays of individually addressable light emitting diodes, control each individual light emitting diode, and to assemble the same in manner to achieve the accuracy and stability for a massive number of individually controlled light emitting diodes that can then be focused using projection optics on to a photoreceptive surface. In addition methods and apparatus are provided to move the imaging system thus described relative to the photoreceptive surface in two axes orthogonal to each other thus exposing the photoreceptive surface.

Abstract: An illuminating apparatus adapted to receive an input power which is a pulse DC includes a lighting unit, a detecting unit and a controlling unit. The lighting unit includes a plurality of lighting sets and a switching unit. The switching unit may be used to cause the lighting sets interconnected in a serial fashion and/or in a parallel manner. The detecting unit detects a state of the input power. The control unit couples the detecting unit and the lighting unit, and controls the switching unit according to the detecting unit detecting the state of the input power. As such, the turn-on voltages of the lighting unit may adjust at different stages of the input power.

Abstract: A power circuit include a plurality of LED strings, each LED string having multiple LEDs connected in series. A plurality of magnetic amplifiers, reset current sources, and a control circuit are used to drive each LED string with equal current and to independently regulate the amount of voltage supplied to each LED to maximize efficiency. One magnetic amplifier, one reset current source, and one current sink are dedicated to each LED string. The control circuit measures the voltage drop across each LED string and determines an amount of reset control current in response to the measured voltage drop. The reset control current is supplied by the reset current source to the magnetic amplifier dedicated to the regulated LED string. The amount of reset control current supplied to the magnetic amplifier dictates the amount of voltage supplied to the LED string.

Abstract: A light emitting diode (LED) driving apparatus is provided, and which includes a first operational amplifier (OPA) having a positive input terminal receiving a predetermined voltage related to a current flowing through an LED string; a first resistor having a first end coupled to a negative input terminal of the first OPA and a second end coupled to a ground; a power transistor having a gate coupled to an output of the first OPA, a drain coupled to a cathode of the LED string and a source coupled to the first end of the first resistor; an error amplifier having a first input terminal coupled to the gate of the power transistor, a second input terminal receiving a reference voltage and an output terminal outputting a control voltage; and a power conversion stage providing a DC voltage to an anode of the LED string according to the outputted control voltage.

Abstract: A lighting device includes a lighting part, a switching part and a luminance fine-tuning part. The lighting part at least includes a first light emitting diode unit for outputting light with a first color temperature and a second light emitting diode unit for outputting light with a second color temperature. The switching part is coupled with a power source. By changing the number of times the switching part is turned on, the light with desired color temperature and luminance is produced by the lighting part according to the user's requirements. By operating the luminance fine-tuning part, the selected luminance is slightly increased or decreased.

Abstract: A semiconductor light emitting element drive device includes: a converter circuit configured to supply a light source unit with a load current from a first-primary winding; and a current regulation circuit. The converter circuit further includes a second-secondary winding. The current regulation circuit includes a switching device (second switching device) connected in series with the second-secondary winding. In a dimming ratio of the light source unit is lower than a first ratio, the second switching device is controlled to ON and OFF so as to decrease the load current through the light source unit by a shunt of a part of the energy stored in the primary winding.