Abstract: The disclosed implementations utilize the voltage drop inherent in the device string to power a device control IC. In some implementations, current is drawn from the bottom of the device string and applied to a voltage supply pin of the device control IC. In some implementations, current is drawn from some other location in the device string (e.g., near the bottom or midpoint of the device string) using a switch. In some implementations, current is drawn from near the bottom and the bottom of the device string at different times, such that less current is drawn from the bottom of the device string as the duty cycle of the device string increases and more current is drawn from near the bottom of the device string as the duty cycle of the device string increases.

Abstract: A method and apparatus for controlling a light string is provided. A controller is coupled to the light string and is used to bias one or more of the multicolor LEDs within each bulb on the light string. Using a prearranged determination of 1) the multicolor LEDs within each bulb, 2) the placement of the bulbs within the light string, and 3) the proper biasing of the plurality of leads within the light string, the controller can be used to change the entire light string from one complex holiday color scheme to another using a simple switching mechanism to select from one a of a plurality of desired color schemes.

Abstract: A plurality of LED-based lighting units is segmented into a plurality of LED-based lighting segments connected in series. Each lighting segment has a plurality of LED-based lighting units connected in series with at least a series-connection switch, and a bypass-connection switch is connected in parallel with the series of LED-based lighting units. The total number of LED-based lighting units can be determined by a maximum voltage level of an input voltage supply and the forward voltage of the LED-based lighting unit for achieving optimal efficiency. The number of lighting segments and the number of lighting units in each lighting segment are properly chosen based on the total number of the LED-based lighting units in such away that any number up to the total number of all the LED-based lighting units can be connected in series by respectively controlling the series-connection switch and the bypass-connection switch of each LED-based lighting segment.

Abstract: A circuit for actuating a plurality of light-emitting means which are connected in series, comprising a plurality of electronic switches, which can be actuated depending on a rectified system voltage. The plurality of electronic switches are arranged in parallel with at least some of the light-emitting means, wherein each of the plurality of electronic switches short-circuits on activation of at least one of the light-emitting means connected in series. At least one energy store is connected in parallel with a first group of light- emitting means during a charge phase by virtue of the electronic switches, and it is connected in parallel with a second group of light-emitting means during a discharge phase by virtue of the electronic switches.

Abstract: What is described is a lighting unit 10 with a plurality of lighting segments 30a, 30b. The lighting segments 30a, 30b are arranged on a strip 40 in spaced relation from each other. Each lighting segment 30a, 30b is connected to an electrical supply terminal 20. In order to obtain a lighting unit with a flexible electrical configuration, each lighting segment 30a, 30b comprises at least one LED element and at least one driver circuit 36 including a controllable, current limiting element for controlling a current through the LED element.

Abstract: An approach is provided for devices and methods for driving an LED light, which adjust the numbers of diodes of the LED string corresponding to the rectified AC voltage. The device comprises a power module, a LED string, a current source and a controller. The LED string has multiple LED diodes connected in series that forms a major segment and multiple minor segments. The controller is connected to the current source and the LED string, which selectively shorts the LED diodes of the minor segments. Since the number of LED diodes of the LED string is dynamically adjusted in response to the rectified voltage, the overall “on” voltage of the LED string is more closely matched to the rectified voltage, and thus the power efficiency is improved.

Abstract: Lighting devices and operating methods are presented in which voltage or current perturbations of an OLED caused by a user pressing the OLED are monitored while the OLED is providing general lighting, and one or more lighting control signals are generated based on the sensed perturbations.

Abstract: A wall switch motion sensor detects motion using a lens and an infrared detector, and in response performs a function (for example, turns on a light). The motion sensor is also adapted to respond to IR remote control signals of the type customarily used to control electronic consumer devices in the home. In one example, a user uses an ordinary remote control device to transmit a sequence of IR control signals and dead times toward the motion sensor. The detector in the motion sensor detects each IR control signal as an increased amount of IR energy, whereas it detects a dead time as a period of less IR energy. If the periodicity of the sequence is appropriate, then the wall switch motion sensor determines that the sequence is an instruction. In one example, the instruction is to turn on/off the light controlled by the wall switch motion sensor.

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: A light fixture comprising a light emitting device, a first electrical path suitable for connecting the light emitting device to a first power circuit, a second electrical path suitable for connecting the light emitting device to a second power circuit and a connector element for acquiring a selected one of a first configuration and a second configuration. Wherein in the first configuration, the light emitting device is in electrical communication with the first electrical path for being powered by the first power circuit and in the second configuration, the light emitting device is in electrical communication with the second electrical path for being powered by the second power circuit.

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: The present invention provides LEDs and zener diodes that are homo-polar and connected in parallel to constitute the first set of LED and zener diode and a second set of LED and zener diode; the first LED and zener diode set and the second LED and zener diode assume a reverse polarity series connection to constitute the voltage-limiting and reverse polarity series type LED device; through the selection of connecting pins, it is used on direct current power source or alternating current power source which is its characteristics.

Abstract: An LED light-emitting device includes: a three-terminal LED circuit which includes a first LED group constituted by a single light-emitting diode or a plurality of light-emitting diodes connected in series, a second LED group constituted by a single light-emitting diode or a plurality of light-emitting diodes connected in series, and an LED common terminal shared by anodes of the first LED group and the second LED group or cathodes thereof, and which has three terminals including both end terminals of the LED groups; and a three-terminal regulator circuit which includes a first regulating unit constituted by a unidirectional current regulator circuit, a second regulating unit constituted by a unidirectional current regulator circuit, and a regulator circuit common terminal connected with the first regulating unit and the second regulating unit and shared by anodes or cathodes thereof so as to exhibit a reverse polarity with respect to the three-terminal LED circuit.

Abstract: A withstand voltage of the LED driver circuit is set to be lower than an LED power supply voltage of the power supply and be higher than a first voltage value obtained by subtracting a voltage drop across whole of the LEDs connected in series caused by the second constant current from the LED power supply voltage. When raising a luminous intensity of the LEDs, in response to the control signal, the control circuit controls the switch circuit to bring about conduction between the LED drive terminal and the first switch terminal to let the first constant current flow through the LEDs. When lowering the luminous intensity of the LEDs, in response to the control signal, the control circuit controls the switch circuit to bring about conduction between the LED drive terminal and the second switch terminal to let the second constant current flow through the LEDs.

Abstract: A lamp control circuit includes a first switch circuit receiving a voltage from a power supply after a control is turned on and outputs a first control signal, a count circuit receives the first control signal and outputs a second control signal, a gate circuit receives the second control signal and outputs a third control signal, a second switch circuit includes a number of electronic switches to receive the third control signal and controls the electronic switches to be turned on or turned off, and a lighting circuit including a number of light emitting diode (LED) groups. Each LED group includes an LED. When an electronic switch connected to an LED group is turned on, the LED of the corresponding LED group is lit. When an electronic switch connected to an LED group is turned off, the LED of the LED group does not light.

Abstract: Circuits for sensing current levels within an apparatus are disclosed. In specific cases, a constant voltage power supply is used to power an LED lighting apparatus in which there are uncertainties within the forward voltages of the LEDs, which in turn creates uncertainty with respect to the current level flowing through the LEDs. To manage these uncertainties, the current flowing through the LEDs is measured by determining a voltage level across a known resistor and calculating the current level. To prevent the known resistor from causing a significant reduction in the efficiency of the overall light engine, the circuit includes one or more transistors in parallel with the known resistor to reduce the effective resistance in the LED circuit during times that the current is not being sensed.

Abstract: The invention provides an LED backlight driving circuit, a backlight module, and an LCD device. The LED backlight driving circuit includes LED light string(s); an anode of the LED light string is connected with a boost circuit, and a cathode of the LED light string is connected with a buck-boost circuit. The invention has the advantages that the limitation of the maximum voltage supplied by the single boost circuit is broken, the voltage difference between both ends of the LED light string is added, namely more LED lights can be connected in series in a single channel. Therefore, the requirement is met by a single string of LEDs or few strings of LEDs instead of the original multiple strings of LEDs, the difficulty of the current sharing of the LED light strings is reduced, the type selection of current sharing IC is convenient, equipment involved therein doesn't need a high voltage resistance, and the use of the current sharing IC is reduced, thereby favoring cost reduction.

Abstract: A light-emitting device (10) includes a plurality of light-emitting areas (10a, 10b and 10c), and each of the light-emitting areas (10a, 10b and 10c) includes a first light-emitting block (3) and a second light-emitting block (4). Each respective first light-emitting blocks (3) include a plurality of first light-emitting elements (A1, A2, or A3), which are connected in series, and each respective second light-emitting blocks (4) include a plurality of second light-emitting elements (B1, B2, or B3), which are connected in series. The number of first light-emitting elements in each respective first light-emitting blocks (3) is the same with one another of the first light-emitting blocks (3), and the number of second light-emitting elements in each respective second light-emitting blocks (4) is the same with one another of the second light-emitting blocks (4).

Abstract: A liquid crystal display device is provided. A plurality of light emitting units includes a plurality of light emitting elements which are configured to emit light toward a liquid crystal panel through a light guide plate. The light emitting units are arranged in series at an interval in such a direction that the light emitting elements face a side surface of the light guide plate. A feeding circuit is configured to supply power to the light emitting units. A first switch is connected to both ends of at least one of the light emitting units such that the at least one of the light emitting units connected between the both ends is deactivated when the first switch is turned on. A second switch is connected to both ends of at least one of the light emitting units such that the at least one of the light emitting units connected between the both ends is deactivated when the second switch is turned on.

Abstract: An LED driving circuit drives multiple channels of light emitting units which provide a function as a backlight for a liquid crystal panel. An interface unit receives a luminance setting signal that specifies the luminance for each channel. The LED driving circuit drives each of the multiple channels of light emitting units with a luminance that corresponds to the luminance setting signal.

Abstract: It is the task of the present invention to provide an LED lighting device that is adapted for an AC voltage supply. Suggested for this is an LED lighting device 1 for an AC voltage supply 2, with several LEDs that form a whole chain 9, whereby the LEDs are divided into LED part groups 11a, b, c, whereby a supply voltage with changing amplitude is present in the LED lighting device 1, whereby several LED part groups 11a, b, c are arranged in series with each other and form an LED strand 8, 8a, b, c, and with shorting links 12a, b, c, each designed for bridging one of the LED part groups 11a, b, c in the LED strand 8, 8a, b, c, and with a control means 10, whereby the control means 10 is designed for controlling the shorting links 12a, b, c in order to place the LED strand 8, 8a, b, c in at least two switch states I, II, whereby the at least two switch states I, II differ in the through voltage of the LED strand 8, 8a, b, c.

Abstract: A variable master current minor circuit may be used to balance the currents through a parallel Light Emitting Diode (LED) strings in an illumination module when the LED string with the largest forward voltage changes due to events, such as a short failure of an LED. The variable master current mirror circuit includes a switching circuit that is coupled to the parallel LED strings and a current minor circuit that is coupled to the parallel LED strings and the switching circuit. The switching circuit switchably connects the LED string with the largest forward voltage to the current minor circuit as a master LED string. The current mirror circuit maintains equal currents through the LED strings with reference to the current through the master LED string.

Abstract: Disclosed are an LED emitting device and driving method thereof. The LED emitting device controls an LED drive switch connected to a first end of an LED string to control an output current supplied to the LED string. The LED emitting device generates feedback information on the output voltage or the output current supplied to the LED string, and uses the output current to sense an open lamp state of the LED string. The LED emitting device uses a voltage at a first end of the LED drive switch to sense a change of the LED string to a normal state from the open lamp state.

Abstract: Circuits and methods to achieve a most efficient driver for white LEDs are disclosed. Switching Losses associated with the switching activity of a boost converter and mainly depending on clock frequency and total capacitance at the switching nodes and conduction losses associated with the current flowing in the boost converter and mainly depending on the series resistance of the elements in the regulation loop are minimized by using a size programmable NFET power switch with constant current limit, a very low voltage and accurate programmable current source, a programmable reference voltage for the error amplifier, and a PWM generator with programmable clock frequency. A limited number of configuration windows corresponding to a set of programmable values (OTP registers) for specific ranges of the current fed to the WLEDs.

Abstract: A power converter having a feedback circuit for constant loads includes an input, a switch, an input voltage sense circuit, a feedback circuit, and a controller. The input is to be coupled to receive an input voltage and the switch is coupled to the input. The input voltage sense circuit is coupled to the input to generate an input voltage sense signal representative of the input voltage. The feedback circuit is coupled to an output of the power converter, where the output is electrically coupled to the input. The feedback circuit generates a feedback signal representative of an output voltage of the power converter. The controller is coupled to the feedback circuit and to the input voltage sense circuit to control switching of the switch to regulate an output current at the output of the power converter in response to the feedback signal and the input voltage sense signal.

Abstract: Power management and thermal management for high intensity LED lamps are disclosed.

Abstract: A converting controller is provided and comprises a first comparing unit, a second comparing unit, a duty cycle operating unit and a reference voltage supplying unit. The first comparing unit receives a detecting signal representing a state of the load and a first reference signal, and generates a first comparing signal accordingly. The duty cycle operating unit controls power conversion of the converting circuit according to the first comparing signal. The second comparing unit receives the detecting signal and a second reference signal, and generates a second comparing signal accordingly. The reference voltage supplying unit supplies the first reference signal and adjusts a level of the first reference signal in response to the second comparing signal.

Abstract: The present disclosure discloses a lighting apparatus using a PN junction light-emitting element, the apparatus comprising: a power transmitting substrate; PN junction light-emitting elements mounted on the power transmitting substrate; circuit elements mounted on the power transmitting substrate and controlling power provided to the PN junction light-emitting elements; and a top cover covering the circuit elements and forward reflecting light emitted by the PN junction light-emitting elements.

Abstract: Circuitry and methods for driving a plurality of LED strings are disclosed herein. In one embodiment, the circuitry comprises a plurality of current regulating circuits electrically coupled to the LED strings and are configured to regulate a current flowing through the LED strings. At least two control circuits are coupled to the current regulating circuits and are configured to generate a control signal according to terminal voltages of the corresponding current regulating circuits. A voltage converter is electrically coupled to the LED strings and to the at least two control circuits, and is configured to regulate the DC driving voltage according to the at least two control signals.

Abstract: The invention relates to a method and a device for driving an LED string of a first LED segment (11) and at least one further LED segment (12, 13, 14) connected in series. Each LED segment has at least one light emitting diode, LED. The LED string is powered by a rectified AC mains voltage. The first LED segment (11) is powered when the rectified AC mains voltage is above a first voltage level, and the first LED segment and the further LED segment are powered when the rectified AC mains voltage is above a second voltage level higher than the first voltage level. The first LED segment emits light having a first color temperature, and the further LED segment emits light having a second color temperature higher than the first color temperature. The light emitted by the first LED segment and the light emitted by the further LED segment are superimposed. The color temperature change of the light emitted by the LED string, when dimmed, resembles the color temperature change of an incandescent lamp.

Abstract: A constant current LED lamp is provided with a linear driver circuit for driving multiple light emitting diodes (LEDs), or LED packages including multiple LED chips, connected in series. The driver circuit includes a rectifier circuit, a filter circuit, a stable voltage circuit, and a constant current circuit. The driver circuit allows the aggregate forward voltage drop of all the LEDs connected in series to approach the rectified input voltage to efficiently utilize the AC power from the mains.

Abstract: A light-emitting device, electrically connected to an external variable voltage source, includes a plurality of light-emitting modules sequentially electrically connected in series and electrically connected to the external variable voltage source. Each light-emitting module has at least one light-emitting unit, a first connection terminal and a second connection terminal. At least one of the light-emitting modules has a control unit and a bypass unit electrically connected to the light-emitting unit. The second connection terminal of the light-emitting module having the bypass unit and the control unit is electrically connected to the first connection terminal of the other light-emitting module and serves as a detection terminal. The control unit detects a voltage of the detection terminal and accordingly controls the bypass unit to adjust a current flowing through the light-emitting unit.

Abstract: The present invention provides an illumination device, an illumination system, and a lamp. The illumination system includes the illumination device and a light modulation module. The illumination device includes a light emitting diode (LED) array, an alternating current (AC) current source, and an output power control module. The AC current source is electrically coupled to the LED array. The output power control module is electrically coupled to the LED array and the AC current source. The LED array, the AC current source, and the output power control module together form a closed-loop control loop. The light modulation module is electrically coupled to the closed-loop control loop for modulating illumination brightness of the LED.

Abstract: The present disclosure discloses a lighting apparatus using a PN junction light-emitting element, the apparatus including: a power transmitting substrate having a plurality of boundaries defined thereon; a plurality of PN junction light-emitting elements positioned within each boundary and divided into a plurality of groups; and a first switch provided on the power transmitting substrate, wherein the first switch goes into the ON state by a supplied AC having a first voltage to cause PN junction light-emitting elements of a first group positioned within each boundary to emit light, and the first switch is in the OFF state when PN junction light-emitting elements of a second group, which is positioned within each boundary and connected in series to the first group, emit light by a supplied AC having a second voltage higher than the first voltage.

Abstract: When a turn on signal or a turn off signal is input from a receiving unit to a controller, the controller outputs the turn on signal or the turn off signal to a voltage setting unit. When the turn on signal is input, the voltage setting unit sets an upper limit value of a voltage Vout supplied from a power source circuit to a LED module to a lighting upper limit value. When the turn off signal is input, the voltage setting unit sets an upper limit value of the voltage Vout supplied from the power source circuit to the LED module to a switching upper limit value lower than the lighting upper limit value.

Abstract: A universal module capable of being removably coupled to each of a plurality of distinct products for demonstrating a functionality is described. In the universal module an activation switch is operatively coupled to a DC power source. An external electrical connector is operatively coupled to the DC power source and the activation switch. An external electrical connector is configured to removably couple the universal module to an external circuit of one of the plurality of distinct products. The circuit has an integrated circuit that is operatively coupled to the DC power source, the activation switch and the external electrical connector. When the external electrical connector is coupled to the external circuit and the activation switch is activated, the integrated circuit outputs a voltage from the DC power source through the external electrical connector to enable a functionality of a coupled product for a predetermined period of time.

Abstract: A driving power control circuit and method for light emitting diodes (LEDs) are provided. The driving power control circuit includes a plurality of switch units and a control unit. Each switch unit is electrically coupled to one LED string whose end generates node voltage. The control unit includes a voltage selecting module, a subtractor, and an adjusting module. The voltage selecting module is electrically coupled to the node voltages and outputs one of the node voltages as a reference node voltage. The subtractor is electrically coupled to an output terminal of the voltage selecting module and generates a corresponding feedback voltage according to the reference node voltage and the node voltage. The adjusting module is electrically coupled to an output terminal of the subtractor and outputs a corresponding adjusting signal according to the feedback voltage to determine whether the corresponding switch unit is turned on.

Abstract: A light emitting diode (LED) lamp includes an LED cluster including LED groups arranged in series, a power source configured to provide an input power to the LED cluster, and a driving unit configured to adjust a number of the LED groups connected to a current path of the LED cluster in series based on the input power to the LED cluster.

Abstract: A diode selection circuit for a light emitting apparatus according to some embodiments includes a plurality of light emitting devices coupled in series. The diode selection circuit includes a comparator configured to receive a rectified AC input signal and a reference voltage and to generate a control signal in response to comparison of the rectified AC input signal with the reference voltage, a voltage controlled current source configured to supply a current to the plurality of light emitting diodes that is proportional to the rectified AC input signal, and a switch configured to receive the control signal and to shunt current away from at least one of the plurality of light emitting devices in response to the control signal.

Abstract: Ladder network circuits for controlling operation of a string of light emitting diodes (LEDS). The circuits include a number of sections connected in series. Each section includes one or more LED junctions, a variable resistive element coupled to the LED section, and a switch coupled to the variable resistive element and the LED section for controlling activation of the LED. The sections can include a transistor coupled between the switch and variable resistive element. The series of sections are connected to an AC power source, rectifier, and dimmer circuit. When receiving power from the power source, the sections activate the LEDs in sequence throughout the series of the sections. The dimmer circuit controls activation of a selection of one or more of the sections in order to activate in sequence the LEDs in only the selected sections, providing for both dimming and color control of the LEDs.

Abstract: A lighting apparatus includes a string of light emitting diode (LED) sets coupled in series where each set includes at least one LED. A current diversion circuit is coupled to the string and is configured to operate responsive to a bias state transition of one of the LED sets to direct current away from another one of the LED sets. A current limiting circuit is coupled in series with the string and is configured to conduct current responsive to a forward biasing of all of the LED sets. The current limiting circuit includes only passive electrical component(s).

Abstract: A method of controlling a solid state lighting apparatus can be provided by receiving a solid state lighting characteristic selection signal at a solid state lighting apparatus and selecting, responsive to the solid state lighting characteristic selection signal, a solid state lighting model that defines a relationship between different lighting parameters used to vary light output from the solid state lighting apparatus responsive to a user input provided to the solid state lighting apparatus.

Abstract: The present disclosure discloses a dimming method of a lighting apparatus using a PN junction light-emitting element, the method including: supplying AC controlled by a dimmer; causing a first group, which has one PN junction light-emitting element positioned within a first boundary and one PN junction light-emitting element positioned within a second boundary, to emit light at a first voltage by the supplied AC when a first switch is in the ON state; and causing a second group, which has another PN junction light-emitting element positioned within the first boundary and another PN junction light-emitting element positioned within the second boundary and which is connected in series to the first group, to emit light at a second voltage higher than the first voltage by the supplied current when the first switch positioned between the first group and the second group is in the OFF state.

Abstract: A light emitting diode (LED) driver is provided that includes a light emitting diode, a converter connected to the light emitting diode, wherein the converter receives an input voltage and converts the input voltage to a basic voltage for driving the light emitting diode, a current regulator connected to the light emitting diode, a first operational amplifier connected to the current regulator, an analog dimming voltage generating unit including a second operational amplifier, a first resistor, a second resistor, and a third resistor, wherein a first terminal of the first resistor, a first terminal of the second resistor, and a first terminal of the third resistor are connected to a non-inversion terminal of the second operational amplifier, and connected to the first operational amplifier, and a pulse-width-modulation dimming pulse generating unit connected to a second terminal of the third resistor.

Abstract: An illumination module includes a plurality of Light Emitting Diodes (LEDs) located in different zones to preferentially illuminate different color converting surfaces. The flux emitted from LEDs located in different zones may be independently controlled by selectively routing current from a single current source to different strings of LEDs in the different zones. In this manner, changes in the CCT of light emitted from LED based illumination module may be achieved.

Abstract: A Light Emitting Diode (LED) driver for preventing shorting has an LED driver circuit. A protection circuit is coupled to the LED driver to detect a fault condition by monitoring a cathode of an LED string of the LED driver, an LED current sense voltage of the LED driver, an LED current feedback error voltage of the LED driver circuit, and a state of a dimming switch of the LED driver.

Abstract: An LED driver arrangement wherein a low voltage IC is arranged to sample the voltage at a terminal of each of the respective electronically controlled switches controlling a plurality of LED strings each receiving power from a single source, with the single source providing voltage in excess of the voltage rating of the IC. For each electronically controlled switch a controllable current source and an isolating unidirectional electronic valve is provided, the respective current source being enabled only when the respective associated electronically controlled switch is at least partially closed thereby ensuring that the respective isolating unidirectional electronic valve associated with the respective illuminating LED string conducts, and the voltage at the terminal of the respective electronically controlled switch is thus seen by the IC when the associated LED string is producing illumination, the voltage then being lower than the maximum voltage rating of the IC.

Abstract: A driving circuit includes a switch, a detecting unit, and a current supply unit. A first terminal of the switch is used for coupling to a first terminal of a first LED group of a plurality of LED groups and receiving a first voltage, and a third terminal of the switch is used for coupling to a first terminal of a last LED group of the plurality of LED groups. The detecting unit is used for outputting a switch control signal to a second terminal of the switch for controlling turning-on and turning-off of the switch. The current supply unit has a plurality of input current terminals, and a ground terminal coupled to ground, where each input current terminal of the plurality of input current terminals is used for coupling to a second terminal of a corresponding LED group of the plurality of LED groups.

Abstract: In one novel aspect, driving a string of light emitting elements, such as LEDs, includes applying a drive signal to circuitry that regulates a voltage appearing at a source of a transistor whose drain is coupled to one end of the string of light emitting elements and whose source is coupled to ground through a resistive element. Sequencing of the drive signal and a voltage supply signal for the light emitting elements is controlled such that the voltage supply signal is not increased above a predetermined allowable voltage for the transistor until the transistor is turned on, and such that the supply voltage is not decreased below the allowable voltage for the transistor until the transistor is turned off.

Abstract: A two-terminal current controller having a current limiting unit and an adjusting unit regulates a first current flowing through a load according to a load voltage. When the load voltage does not exceed a first voltage, the two-terminal current controller operates in a first mode for conducting a second current associated a rectified AC voltage, thereby limiting the first current to zero and adjusting the second current accordingly. When the load voltage is between the first voltage and a second voltage, the two-terminal current controller operates in a second mode for conducting the second current, thereby limiting the first current to zero and limiting the second current to a constant value larger than zero. When the load voltage exceeds the second voltage, the two-terminal current controller operates in a third mode for turning off the current limiting unit. The adjusting unit can adjust the predetermined value and the second voltage.