Abstract: A circuit is disclosed for driving a plurality of LED strings from an AC supply and arranged to, in use, drive current through a series arrangement of a plurality N of the LED strings when the AC voltage is sufficient to drive the plurality N of the LED strings: the circuit comprising a first current source configured to be switchably connected to a one end of said series arrangement of N LED strings; a series combination of a second current source and a heat dissipater, wherein the series combination of the second current source and the heat dissipater is arranged in parallel with the first current source; and a current balancer for balancing the current through the first current source and the second current source. A driver for such a circuit is also disclosed.

Abstract: Self-identifying solid-state transducer (SST) modules and associated systems and methods are disclosed herein. In several embodiments, for example, an SST system can include a driver and at least one SST module electrically coupled to the driver. Each SST module can include an SST and a sense resistor. The sense resistors of each SST module can have at least substantially similar resistance values. The SSTs of the SST modules can be coupled in parallel across an SST channel to the driver, and the sense resistors of the SST modules can be coupled in parallel across a sense channel to the driver. The driver can be configured to measure a sense resistance across the sense resistors and deliver a current across the SSTs based on the sense resistance.

Abstract: The invention relates to a circuit arrangement (1) for controlling at least one load (D1, D2, D3). In order to provide means for extracting an auxiliary power supply from a current source in order to control shunt switching, the inventive circuit arrangement (1) comprises an input terminal (11) for connection to a power supply (30), an output terminal (12) for connection to at least one load element (20, 21, 22, 23), a control circuit (10), comprising a control device (13), which is adapted to control at least one load element (20, 21, 22, 23), and an energy storage device (C), which is adapted to supply power to the control device (13). A controllable bypass switch (M4) is further provided, wherein said bypass switch (M4) and said control circuit (10) are connected in parallel and are connected between said input terminal (11) and said output terminal (12). The circuit arrangement (1) is adapted to operate the bypass switch (M4) to control the power provided to the control circuit.

Abstract: In accordance with certain embodiments, an illumination system comprising a plurality of power strings features elements facilitating compensation for failure of one or more light-emitting elements connected along each power string.

Abstract: A driver circuit for driving light emitting diodes (LEDs). The driver circuit includes: a string of LEDs divided into n groups, the n groups of LEDs being electrically connected to each other in series, a downstream end of group m?1 being electrically connected to the upstream end of group m, where m is a positive number equal to or less than n. The driver circuit also includes a plurality of current regulating circuits, each of the current regulating circuits being coupled to the downstream end of a corresponding group at one end and coupled to the ground at the other end and including a sensor amplifier and a cascode having first and second transistors, each sensor amplifier being coupled to a different voltage source for providing a different reference voltage thereto.

Abstract: A distributed system for driving strings of series-connected LEDs for backlighting, display and lighting applications includes multiple intelligent satellite LED driver ICs connected to a an interface IC via serial bus. The interface IC translates information obtained from a host microcontroller into instructions for the satellite LED driver ICs pertaining to such parameters as duty factor, current levels, phase delay and fault settings. Fault conditions in the LED driver ICs can be transmitted back to, the interface IC. An analog current sense feedback system which also links the LED driver ICs determines the supply voltage for the LED strings.

Abstract: A distributed system for driving strings of series-connected LEDs for backlighting, display and lighting applications includes multiple intelligent satellite LED driver ICs connected to a an interface IC via serial bus. The interface IC translates information obtained from a host microcontroller into instructions for the satellite LED driver ICs pertaining to such parameters as duty factor, current levels, phase delay and fault settings. Fault conditions in the LED driver ICs can be transmitted back to the interface IC. An analog current sense feedback system which also links the LED driver ICs determines the supply voltage for the LED strings.

Abstract: A light emitting diode (LED) driving circuit structure includes a surge absorber unit, a voltage suppression unit connected to the surge absorber unit, a rectifier unit electrically connected to the voltage suppression unit, a control chip connected to a fourth junction of the rectifier unit, and an impedance unit connected to the control chip. The LED driving circuit structure is installed on an LED light circuit board having a plurality of LEDs mounted thereon. According to the sinusoidal wave form of the alternating current (AC) supplied to the LEDs as well as the number and layout of the LEDs on the LED light circuit board, the LED driving circuit structure controls the current flowing through the LEDs to vary with changes of supply voltage, so as to enable effectively increased power factor and reduced harmonics, as well as effectively lowered manufacturing and material costs.

Abstract: Short circuit failures and open circuit failures of light-emitting elements used for the backlight in an LCD panel can be reliably and easily detected. The voltage at the node between each series-connected light-emitting element array and a drive circuit is detected as a monitored voltage. A maximum detector detects the highest and a minimum detector detects the lowest of these monitored voltages. Short circuit or open circuit failure of a light-emitting element is detected by comparing the voltage difference between the maximum detector output and the minimum detector output with a specific reference voltage.

Abstract: LED controllers, LED lighting systems and control methods capable of providing an average luminance intensity independent from the variation of an AC voltage. A string of LEDs are divided into LED groups electrically connected in series between a power source and a ground. A LED controller has path switches, each for coupling a corresponding LED group to the ground. A management center controls the path switches, for making an input current from the power source to the string substantially approach a target value. A line waveform sensor coupled to the power source holds a representative signal during a cycle time of the power source. The representative signal is in response to an attribute of the power source, and substantially determines the target value.

Abstract: A distributed system for driving strings of series-connected LEDs for backlighting, display and lighting applications includes multiple intelligent satellite LED driver ICs connected to a an interface IC via serial bus. The interface IC translates information obtained from a host microcontroller into instructions for the satellite LED driver ICs pertaining to such parameters as duty factor, current levels, phase delay and fault settings. Fault conditions in the LED driver ICs can be transmitted back to the interface IC. An analog current sense feedback system which also links the LED driver ICs determines the supply voltage for the LED strings.

Abstract: A driver circuit for driving light emitting diodes (LEDs). The driver circuit includes: a string of LEDs divided into n groups, the n groups of LEDs being electrically connected to each other in series, a downstream end of group m?1 being electrically connected to the upstream end of group m, where m is a positive number equal to or less than n. The driver circuit also includes a plurality of current regulating circuits, each of the current regulating circuits being coupled to the downstream end of a corresponding group at one end and coupled to the ground at the other end and including a sensor amplifier and a cascode having first and second transistors, each sensor amplifier being coupled to a different voltage source for providing a different reference voltage thereto.

Abstract: A fault-tolerant controller for a lighting system comprising: a plurality of light emitting diode (LED) circuits and a controllable power source to power the plurality of LED circuits. The controller comprising a minimum voltage selector to determine a minimum voltage from a plurality of feedback voltages, one feedback voltage for each of the plurality of LED circuits. A control logic to regulate the drive voltage for the LEDs; and an overvoltage warning mechanism to determine an overvoltage of the drive voltage. The controller identifies one or more open-circuit conditions, one for each LED circuit, for which the respective feedback voltage is below an open-circuit threshold, and which causes the minimum voltage selector to exclude one or more respective feedback voltages associated with the LED circuits which have an open-circuit condition.

Abstract: A light-emitting device control method is provided. The light-emitting device control method comprises the steps outlined below. A light-emitting module of a light-emitting device having light-emitting unit string each having light-emitting units connected in series is operated. One end of each light-emitting unit strings receives a same DC voltage. A voltage drop value across each current control units connected in series to at least one of the light-emitting unit strings is retrieved to further determine whether the light-emitting unit of each of the light-emitting unit strings malfunctions. When x light-emitting units of a specific string malfunction and x is larger than or equal to a malfunction threshold value p, the x malfunctioned light-emitting units are shorted and (x?p+1) light-emitting units in each of the light-emitting unit strings other than the specific string are shorted. The DC voltage received by each of the light-emitting units is decreased.

Abstract: A light emitting diode (LED) backlight driving circuit includes a plurality of LED light bars, a power supply driving the LED light bars to light, and comparing units corresponding to the LED light bars one by one. A first input end of the comparing unit is coupled to a cathode end of the LED light bar, and a second input end of the comparing unit receives a first reference voltage. Each of the LED light bars is connected in series with a switching unit, an output end of the comparing unit is coupled to a statistic unit, an output end of the statistic unit is coupled to driving units corresponding to the switching units one by one and controlling the switching units to turn on/off. The statistic unit divides the LED light bars into two groups according to a logic state output by the comparing unit, and controls the driving unit to turn off one of two groups of LED light bars having a fewer number than the other group of the LED light bars.

Abstract: Multi junction solid-state transducer (SST) devices and associated systems and methods are disclosed herein. In several embodiments, for example, an SST system can include a first multi-junction SST chain having a first drive voltage, a first P-contact, and a first N-contact, and a second multi junction SST chain having a second drive voltage, a second P-contact, and a second N-contact. The first and second multi junction SST chains can be configured to be activated independently of each other. The SST system can further include a driver operably coupled to the first and second P- and N-contacts. The driver can be configured to activate the first multi junction SST chain when voltage input is at least equal to the first drive voltage. When absolute voltage increases a predetermined voltage level, the driver can be configured to activate the second multi-junction SST chain or the first and second multi junction SST chains.

Abstract: In one aspect, a light emission diode (LED) illumination system is capable of providing generally constant illumination by LED ladders coupled to power sources in a polyphase system, where each LED ladder is coupled to a power source respectively. In another aspect, a colored LED illumination system includes multi-color LEDs and is capable of controlling the color output from the LEDs. The colored LED illumination system includes a plurality of LED ladders coupled to a color-mix-control circuit. The color-mix-control circuit can control the output color of the LED ladders by adjusting the intensity of each LED ladder individually.

Abstract: A driving circuit includes a plurality of light-emitting units, a plurality of switches, and a voltage generating module. The light-emitting units are coupled with each other in series and are driven with an input voltage varying according to a frequency. Each switch has a preset voltage and an activation voltage and includes a light-emitting end, a control end, and a setting end. The light-emitting ends are coupled with the light-emitting units, and the setting ends of the switches are coupled with each other. The voltage generating module includes a plurality of control units and provides a plurality of control voltages to the switches, and each switch is driven to be activated or to be deactivated according to a relation of the preset voltage and a difference between the control voltage and the activation voltage when the input voltage drives the light-emitting units, the switches, and the control units.

Abstract: The present application discloses an open circuit protecting circuit, an open circuit protecting method and an illuminating apparatus. The open circuit protecting circuit is configured in an apparatus with a LED load being supplied with power by a current source, and comprises: a switch circuit, a timer circuit and a detecting circuit. When the LED load malfunctions, the open circuit protecting circuit carries out the following operations: the detecting circuit sends an enabling signal to the timer circuit, the timer circuit sends a driving signal with a set time to the switch circuit and the switch circuit is in the on-state during the set time, so as to make the LED load be short circuited to protect the circuit from being damaged. The open circuit protecting circuit can also resume to normal work automatically after the open circuited malfunction is cleared, and thus a hot-plugging function can be realized.

Abstract: An LED backlight driving circuit has a voltage converting unit having an output terminal connected to a positive electrode of an LED to provide a driving voltage required by the LED, a driving unit to control the voltage converting unit to achieve a voltage conversion, and a protection unit connected in series between a negative electrode of the LED and the driving unit. A maximum allowable power of the protection unit is less than a power when the driving voltage of the LED is directly applied to the protection unit. The circuit also includes a control unit for outputting a control signal for stopping working to the driving unit when the protection unit forms an open circuit. Thus, the circuit parts can be protected, and the short-circuit protection function is more safe and reliable.

Abstract: The present invention relates to an LED emitting device and a driving method thereof. The LED emitting device receives an input voltage and supplies a power supply voltage needed for operating an LED channel according to a switching operation of a power switch. The LED emitting device controls the power supply and also controls a load switch between the LED channel and an output voltage. The LED emitting device determines the LED channel to be short circuited when the output voltage is reduced to a predetermined threshold voltage during a predetermined short circuit sense period starting from the time when the output voltage reaches a regulated voltage before the LED channel is dimmed. During the short circuit sense period, the power supply is stopped and the load switch is turned on.

Abstract: A lighting system includes a switch configured so that when the switch is in a first state, current from a supply flows to a light emitter, and when the switch is in a second state, current from the supply flows through the switch bypassing the light emitter. A capacitor in parallel with the light emitter provides current to the light emitter sufficient to cause the light emitter to emit light when the switch is in the second state.

Abstract: An LED light string with open circuit protection has a first end for receiving a first voltage, a second end for receiving a second voltage, and multiple LED units connected in series between the first end and the second end. Each of the LED units has multiple LEDs and at least one by-pass resistor connected in parallel. Even when the LEDs of the same LED unit all fail, a current from the first end to the second end can still flow through all the LED units via the by-pass resistors to drive the remaining normal LED units.

Abstract: An electrical circuit for driving a light emitting diode (LED) string is described. The electrical circuit includes a first LED string having one or more color LED strings. A first current control transistor is coupled in series with the first LED string. A color bypass transistor may couple in parallel to one of the one or more color LED strings. A second LED string may also be coupled to the first LED string at an anode terminal of both LED strings. The second LED string may be coupled in parallel with a string bypass transistor and in series with a second current control transistor. Connection interfaces to control terminals of the first current control transistor, the color bypass transistor, the second current control transistor, and the string bypass transistor enable a control device to operate these transistors in linear mode to drive the LED strings.

Abstract: A lighting device for an AC power supply comprising at least two lighting groups, wherein each lighting group has a group input and a group output and at least one LED, wherein the at least one LED is arranged between the group input and the group output, wherein the lighting groups are connected to one another in series.

Abstract: In an embodiment, a lamp control circuit is provided. The lamp control circuit includes an intermediate current steering block configured to be coupled to a cathode of a first light-emitting device of a plurality of light-emitting devices and a final current steering block configured to be coupled to a cathode of a final light-emitting device of the plurality of light-emitting devices. The final current steering block is configured to disable the intermediate current steering block and conduct current when a voltage input to the plurality of light-emitting devices is sufficient to activate all of the plurality of light-emitting devices.

Abstract: An LED luminaire according to an exemplary embodiment of the present invention includes a rectifier outputting a first rectified voltage generated by rectifying AC voltage and flattening the rectified voltage, a power factor correction unit receiving the first rectified voltage output from the rectifier and generating and outputting a drive voltage, an LED light emitting unit including first to m-th light emitting groups each including at least one LED, the LED light emitting unit sequentially driven by receiving the drive voltage input from the power factor correction unit, and an LED drive IC determining a voltage level of the drive voltage upon receiving the drive voltage input from the power factor correction unit, and controlling sequential driving of the first to m-th light emitting groups according to the determined voltage level of the drive voltage.

Abstract: A driver circuit for driving light emitting diodes (LEDs). The driver circuit includes: a string of LEDs divided into n groups, the n groups of LEDs being electrically connected to each other in series, a downstream end of group m-1 being electrically connected to the upstream end of group m, where m is a positive number equal to or less than n. The driver circuit also includes a plurality of current regulating circuits, each of the current regulating circuits being coupled to the downstream end of a corresponding group at one end and coupled to the ground at the other end and including a sensor amplifier and a cascode having first and second transistors, each sensor amplifier being coupled to a different voltage source for providing a different reference voltage thereto.

Abstract: In one embodiment, a method of forming an LED control circuit may include configuring the LED control circuit to receive a sense signal that is representative of a value of an LED current flow through a plurality of LED strings wherein each LED string includes a plurality of series coupled LEDs; configuring a detector circuit of the LED control circuit to detect the LED current being no greater than a first value and responsively initiate forming a first time period; and configuring the LED control circuit to inhibit forming the LED current responsively to termination of the first time period.

Abstract: The present invention provides a protection circuit with low energy-consumption and driving circuit thereof, including a detection circuit and a switch circuit, with switch circuit disposed between power supply circuit and peripheral step-down shunt; detection circuit and switch circuit connected for controlling. Switch circuit includes a PNP triode or P MOS transistor connected between power supply circuit and peripheral step-down shunt; wherein base of the PNP triode or P MOS transistor connected to drain of another N MOS transistor through resistor, gate of N MOS transistor connected to status pin of detection circuit.

Abstract: Electrical and mechanical connection for a series connected LED lamp to an appropriate electrical circuit. The circuit contains additional series connected light producing elements. To enable continuous operation of all the other light producing elements in the series circuit, the socket contains a device to bypass the series current to the remaining circuit elements in the case of a defective lamp or connection. Operation of the bypass device is controlled within the socket with operational parameters controlled either from within the socket or in conjunction with an external element in the lamp. The operation of the bypass circuit is latching, once operating the bypass will continue to operate until reset preventing unwanted flicker in the case of intermittent connections. The method of resetting the bypass circuit may be either manual or automatic. The socket bypass may contain a time delay to allow internal bypass circuits included within the lamp to operate before the socket bypass activates.

Abstract: A LED driving system comprising: an input port to receive an input signal; a switch node to provide a switching signal; an energy storage component coupled between the input port and the switch node; a main switch coupled between the switch node and ground; n output lines coupled in parallel, and each output line having a first and second terminals, and wherein the first terminal is coupled to the switch node, and the second terminal is coupled the reference ground, and wherein each output line having an output switch, a diode and a LED string coupled in series between the first and second terminals, and wherein each output line having a capacitor coupled in parallel with the LED string; and a controller providing a control signal to the main switch and providing corresponding n control signals to the corresponding n output switches in the corresponding n output lines.

Abstract: An LED array switching apparatus, comprises: a plurality of LED segments D1 to Dn connected in series, each LED segment having a forward voltage; a voltage supply coupled to the plurality of LED segments; and a plurality of constant current sources G1 to Gn, coupled to outputs of LED segments D1 to Dn, respectively. Each of the constant current sources is switchable between a current regulating state and an open state such that as the voltage of the voltage supply increases, LED segments are switched on and lit to form a higher forward voltage LED string, and as the voltage of the voltage supply decreases, segments are switched off and removed from the LED string starting with the most recently lit segment.

Abstract: A LED driving device adapted to driving N LED strings connected in series is provided. N is a positive integer greater than 1. The LED driving device includes (N?1) switch units, a current source, a detection unit and a control unit. The ith switch unit electrically connects to the (i+1) LED string in parallel or to the ith LED string in parallel, and 0<i?(N?1). The current source supplies a driving current to drive the N LED strings. The detection unit outputs a detection signal according to a voltage of the current source, a first reference voltage and a second reference voltage. The control unit outputs a plurality of first control signals according to the detection signal to dynamically control an amount of the (N?1) switch units turned on.

Abstract: A light emitting diode (LED) backlight driving circuit includes an LED lightbar, and a constant current chip that controls current flowing through the LED lightbar. The LED backlight driving circuit further includes a comparison module that receives an output voltage of the LED lightbar. When the output voltage of the LED lightbar is greater than the preset reference voltage, the comparison module controls the constant current chip to switch off the current of the LED lightbar.

Abstract: A light emitting diode (LED) backlight driving circuit includes a power supply, an LED light bar coupled to the power supply, a constant current driving chip that drives the LED light bar to light, and a comparing unit. The constant current driving chip includes an under-voltage protection pin that receives an under-voltage protection signal. An overvoltage collecting unit of the LED backlight driving circuit and an under-voltage collecting unit of the LED backlight driving circuit are coupled to an input end of the power supply, and an output voltage of the under-voltage collecting unit is directly input to the under-voltage protection pin. A reference voltage is input to a first input end of the comparing unit, and a second input end of the comparing unit is coupled to the overvoltage collecting unit. When an output voltage of the overvoltage collecting unit exceeds the reference voltage, the comparing unit sends the under-voltage protection signal to the under-voltage protection pin.

Abstract: An illumination apparatus includes: a plurality of light emitting modules connected in series; a constant current source; and a fault detection circuit for detecting that the plurality of light emitting modules have at least one thereof with a short circuit fault. The light emitting module includes: an organic EL panel; a threshold value detection circuit configured to output a constant voltage when the organic EL panel between its anode and cathode has a potential difference equal to or larger than a threshold value; and a VI conversion circuit receiving the constant voltage from the threshold value detection circuit, converting the constant voltage into a constant current, and outputting the constant current. The fault detection circuit detects whether the plurality of light emitting modules have a short circuit fault based on a total value of the constant current output from each light emitting module.

Abstract: The present invention provides LED backlight source of liquid crystal display device. The LED backlight source includes: a boost converter, boosting input DC voltage and outputting boosted DC voltage; a plurality of LED strings connected in parallel, with each LED string including a plurality of LEDs in series and receiving boosted DC voltage from boost converter; a plurality of constant-current drivers, controlling current of each LED string, each constant-current driver controlling at least an LED string and first constant-current driver controlling connection/disconnection of boost converter; an under-voltage protection control circuit, outputting under-voltage protection voltage to constant-current drivers and constant-current drivers determining whether to stop operating based on received under-voltage protection voltage, wherein under-voltage protection voltage outputted to first constant-current driver less than under-voltage protection voltages outputted to other constant-current drivers.

Abstract: A retrofit lamp includes at least one series circuit having a multiplicity of LEDs having a circuit arrangement. The at least one series circuit including is coupled between a first rectifier output connection and a second rectifier output connection. A breakdown apparatus is coupled between a third connection terminal and a fourth connection terminal The breakdown apparatus may have the following properties: up to a first threshold value of the voltage drop across said breakdown apparatus during operation, the breakdown apparatus is nonconducting. If the first threshold value is exceeded, the breakdown apparatus becomes conducting. The breakdown apparatus remains conducting as long as current is supplied to it which is above a second threshold value. As soon as the current falls below the second threshold value, the breakdown apparatus becomes nonconducting again. In the conducting state, the breakdown apparatus has a forward voltage which is below a third threshold value.

Abstract: An LED drive circuit is disclosed, which comprises a square wave generator configured to generate a square-wave signal for driving an LED unit, an LLC resonance circuit configured to transform the square-wave signal outputted by the square wave generator into a sinuous wave of a reduced voltage level, and the LED unit comprising at least one LED sub-unit. The LED sub-unit comprises at least a first LED lamp set and a second LED lamp set connected in parallel, and LEDs of the first LED lamp set are disposed in a direction opposite to those of the second LED lamp set. The square wave generator, the LLC resonance circuit and the LED unit are connected in sequence. The LED drive circuit of the present disclosure can drive an LED and has a reduced cost.

Abstract: In accordance with certain embodiments, an illumination system comprising a plurality of power strings features elements facilitating compensation for failure of one or more light-emitting elements connected along each power string.

Abstract: An integrated circuit is capable of controlling current through several light-emitting diode (LED) chains, each having several LEDs forward-connected in series between a major anode and a major cathode. Each major anode is coupled to a power node. The integrated circuit has several driving circuits, a detection node, a comparator, and a logic controller. The driving circuits can light the LED chains, respectively. Detection voltage at the detection node corresponds to voltage at one of the major cathodes. The comparator asserts a ready signal when the detection voltage exceeds a reference voltage. Receiving a dimming signal and the ready signal, if the dimming signal is asserted and the ready signal has been asserted, the logic controller enables the driving circuits to light the LED chains.

Abstract: A Light Emitting Diode (LED) driver apparatus is provided. The LED driver apparatus includes: a Pulse Width Modulation (PWM) signal generator configured to generate a PWM signal, a DC-DC converter configured to provide a driving voltage of a plurality of LED arrays by using the generated PWM signal, and a sensor configured to determine whether at least one LED array among the plurality of LED arrays is in an open state in response to the driving voltage being higher than or equal to a preset first reference voltage, and the preset first reference voltage is higher than the driving voltage applied when the plurality of LED arrays are each in a working state.

Abstract: Disclosed are various embodiments of low cost high quality LED (Light Emitting Diode) retrofit lamp devices capable of operating in a wide range of power and to supersede conventional lighting devices such as incandescent, halogen, sodium or fluorescent lamps. The disclosed embodiments include various LED lamp retrofit apparatuses that maximize the electro-mechanical-optical compatibility of seven interactive systems, such as: LEDs, LED Panel, Supply Adaptor, Housing, Lens/diffuser Shield, In/Out Electrical Wiring an LED driver. LED lamp retrofit apparatuses include incandescent, halogen, fluorescent, and sodium lamps.

Abstract: A circuit can be used for controlling a plurality of LEDs coupled in series. A switching converter operates as a current source coupled to the plurality of LEDs to provide a constant load current thereto. The switching converter includes an inductor coupled in series with the plurality of LEDs such that the same load current flows through the inductor and the plurality of LEDs. No substantial capacitance is coupled between the inductor and the plurality of LEDs. A floating driver circuit is coupled in parallel with each individual LED of the plurality of LEDs. The floating driver circuit is configured to fully or partially take over the load current thereby bypassing the respective LED in accordance with a respective modulated input signal to control the intensity of the light emitted by the LED.

Abstract: An apparatus for driving LEDs using high voltage includes a plurality of LEDs divided into a plurality of LED segments connected in series and a plurality of three-terminal voltage controlled current limiting devices. Each of the current limiting devices is associated with one of the LED segments and has a first terminal connected to a negative end of the associated LED segment, a second terminal applied with a bias voltage and a third terminal connected to a common node. A current source is connected between the common node and ground. A power-loss reduction circuit having a plurality of LEDs controlled by an LED controlling circuit may further be inserted between the common node and the current source to reduce the power loss in the current source because of the high voltage at the common node.

Abstract: The present invention provides an LED backlight drive circuit, which includes a first power supply module, an electrical inductor, a rectifier diode, a MOS transistor, an electrolytic capacitor, an LED light string, a voltage division module, a voltage comparator, a second power supply module, and an LED constant-current drive chip. The LED backlight drive circuit is arranged to include a voltage comparator in an external circuit of the LED constant-current drive chip to detect output voltage of the drive circuit so that high voltage, the voltage comparator is caused to supply a low voltage level to forcibly pull down a PWM dimming signal or an ENA enabling signal of the LED constant-current drive chip to achieve an over-voltage protection function and also enable removal of over-voltage protection module from a conventional LED constant-current drive chip.

Abstract: A light source device includes a plurality of light emitting devices connected in series, an open-circuit failure detecting section, a failure detection and maintenance section, and a short-circuiting section connected in parallel to at least one light emitting device among the plurality of light emitting devices. The open-circuit failure detecting section detects an open-circuit failure of the light emitting device connected in parallel. The failure detection and maintenance section shifts to, when the open-circuit failure detecting section detects the open-circuit failure, a circuit state during the open-circuit failure and maintains the circuit state to which the failure detection and maintenance section shifts. The short-circuiting section short-circuits, when the failure detection and maintenance section maintains the circuit state during the open-circuit failure, both ends of the light emitting device in which the open-circuit failure is detected.

Abstract: A light-emitting diode chain comprising a plurality of light-emitting diodes (LED1 . . . LED4) connected in series and fed by a current source, in which each light-emitting diode is assigned a control circuit (5), which has a series connection, connected in parallel with the light-emitting diode, between a reference voltage sink (D1) of the voltage (Uref) and a controlled switch (Q) and is designed to compare the control voltage (Ust) at a control line (4) common to all control circuits, measured against is base point of the LED series circuit, with the voltage at the connection between the switch and the subsequent LED in the chain or the base point, and to dose or to open the switch if the control voltage (Ust) falls below a predefined value or rises above a predefined value respectively.

Abstract: Optimal power supply topologies that do not use output bulk capacitors as well as freewheeling diodes in output section to therefore provide efficiency, cost, volume, and weight advantage over the existing solutions. The present invention applies a pulse-width modulated switched current at higher frequency (in order of 10 to 100 kHz) to LEDs without degrading optical performance. LEDs' average current control is attained using a feedback loop that senses the average value of LEDs' current and controls the current by varying the pulse width of applied current.