Abstract: A multi channel LED driver comprises a plurality of LED strings. Each of the plurality of LED strings are associated with a separate channel. A voltage regulator generates an output voltage to the plurality of LED strings responsive to an input voltage and a PWM control signal. First control logic generates the PWM control signal responsive to a voltage at a bottom of each of the plurality of LED strings. A plurality of dimming circuitries, each connected to one of the bottoms of the plurality of LED strings, control a light intensity in each of the plurality of LED strings responsive to dimming control signals. Second control logic generates the dimming control signals responsive to forward currents monitored through each of the plurality of LED strings and dimming data.

Abstract: A driving circuit of light emitting diodes includes a power supply circuit, at least one bypass circuit, and a temperature control circuit. The power supply circuit is used for providing a driving voltage to at least one series of light emitting diodes. Each bypass circuit of the at least one bypass circuit is used for being turned on when an ambient temperature is lower than a predetermined temperature. The temperature control circuit is coupled to the at least one bypass circuit for detecting the ambient temperature, and sending a control signal to the at least one bypass circuit when the ambient temperature is lower than the predetermined temperature. Therefore, the driving voltage can still drive the at least one series of light emitting diodes when the ambient temperature is lower than the predetermined temperature.

Abstract: An LED (light emitting diode) driving circuit includes a rectifying circuit, an LED module, a voltage dropping circuit connected to the LED module, a voltage detecting circuit connected between the voltage dropping circuit and the LED module, and an integrated circuit. The integrated circuit includes a pulse-width modulation (PWM) control module providing PWM waves, an overcurrent protection (OCP) module, an overvoltage protection (OVP) module, and a frequency control module. The OCP module detects the working current of the LED module, and the OVP module detects the working voltage. The frequency control module adjust the duty cycle of the PWM waves according to the results of comparisons made by the OCP module and the OVP module against reference levels, to adjust the working current of the LED module.

Abstract: Uneven brightness is less likely to occur in lighting devices at low cost. A backlight unit 12 includes LEDs 17, a chassis 14 having a bottom plate 14a and housing the LEDs 17, and an LED drive controller 24 controlling drive of the LEDs 17. The LEDs 17 are arranged in a matrix in row and column directions (X-axis direction and Y-axis direction) along the bottom plate 14a, forming respective LED groups 25 each along the row direction. The LED groups 25 include a middle LED group 28 and an end side LED group 29. The middle LED group 28 is located in a middle portion of the bottom plate 14a in the column direction group and the end side LED group 29 is located closer to an end of the bottom part from the middle portion group. The LED drive controller 24 controls light of at least one of the middle LED group 28 and the end side LED group 29 such that the end side LED group 29 has relatively high brightness and the middle LED group 28 has relatively low brightness.

Abstract: A lighting device includes: a lighting unit for supplying a lighting power to a light source unit; and a controller, for controlling the lighting unit. The lighting unit has an inductor and a switching element, and a diode for flowing a flyback current of the inductor to the light source unit during an OFF period of the switching element, and the controller has a unit for intermittently driving an ON/OFF operation of the switching element by a PWM signal and a unit for driving the switching element by a frequency higher than that of the PWM signal during an ON period of the PWM signal, and when the PWM signal falls, the controller reduces a peak value of a load current flowing through the light source unit during a certain period.

Abstract: An illumination apparatus includes: a series circuit of a thyristor and at least one load circuit connected across an AC power source; a current control circuit for adjusting an input current to be maintained at a predetermined level during a part or the whole of an ON period of the thyristor; and a short circuit for short-circuiting input ports of the load circuit to have a predetermined resistance during a part of the ON period of the thyristor and a part or the whole of an OFF period of the thyristor. The current control circuit and the short circuit are connected in parallel to the load circuit.

Abstract: The present invention provides a full-bridge driving controller and a full-bridge converting circuit, which have the function of soft switch, to provide a DC output voltage. The present invention employs a resonant unit to oscillate the current flowing through the converting circuit at a resonant frequency. The full-bridge driving controller switches four full-bridge transistor switches at an operating frequency higher than the resonant frequency, so as to achieve the function of soft switch.

Abstract: A system that provides an intelligent approach to driving multiple strings of LEDs. A processing device determines an optimal current level for each LED string from a limited set of allowed currents. The processing device also determines a PWM duty cycle for driving the LEDs in each LED string to provide precise brightness control over the LED string. The settings for the current level and duty cycle are transmitted to an LED driver for regulating the current and on-off times of the LED strings. Beneficially, the system reduces the size of the LED driver while leveraging existing resources available in the processing device to operate the LEDs in a power efficient manner.

Abstract: A lighting system comprising an LED assembly that comprises a first and second LED unit said LED units being serial connected is described.

Abstract: An LED illumination system includes an LED lamp, a voltage stabilizing circuit and a control circuit. The LED lamp includes an LED string which has a plurality of LEDs connected in series. The voltage stabilizing circuit connects the LED lamp for supplying an electric current to the LED string. The control circuit includes an MCU and a MOSFET connected between the MCU and the LED string. The MCU detects the electric current flowing through the LED string and outputs a PWM signal which has a frequency within a range from 60 Hz to 500 Hz to the MOSFET. The MOSFET receives the PWM signal from the MCU and turns on and off repeatedly under a control of the PWM signal, to make a flicker frequency of the LEDs of the LED string be within a predetermined range.

Abstract: A Pulse Width Modulation (PWM) controlling circuit and a Light Emitting Diode (LED) driver circuit having the same are provided. An LED driver circuit includes a voltage detector connected to a plurality of LED arrays, the voltage detector being configured to determine a connection status of each of the LED arrays according to a corresponding level of the feedback voltage, and detect a minimum feedback voltage from feedback voltages of the LED arrays that are determined to be connected, a controller configured to output a control signal to one of abort and control boosting of the LED arrays according to the detected minimum feedback voltage, and a Pulse Width Modulation (PWM) signal generator configured to output a PWM signal corresponding to the outputted control signal according to an on/off state of a dimming signal that drives the LED arrays that are determined to be connected.

Abstract: A Light Emitting Diode (LED) driver circuit and a Pulse Width Modulation (PWM) controlling circuit thereof is provided. The LED driver circuit includes a voltage detector connected to a plurality of LED arrays, the voltage detector being configured to determine a connection status of each of the LED arrays according to a level of a feedback voltage of each of the LED arrays, and detect a minimum feedback voltage from the feedback voltage of each of the LED arrays that are determined to be connected, a controller configured to output a control signal to control boosting of the LED arrays according to the detected minimum feedback voltage, a PWM signal generator configured to output a PWM signal corresponding to the outputted control signal, and a driving voltage generator configured to supply a driving voltage commonly to the LED arrays according to the PWM signal.

Abstract: The present invention discloses a light emitting device array controller which controls a power stage to supply an output voltage to one end of each of a plurality of light emitting device strings. The other end of each of the light emitting device strings is coupled to a corresponding transistor having a current inflow end, a current outflow end and a control end. The present invention obtains signals from the control ends of the transistors instead of the current inflow ends, and feedback controls the output voltage according to the highest voltage of the control ends. Thus, the number of pins required for a circuit chip is reduced.

Abstract: A light-emitting-diode (LED) driving apparatus is provided, and which includes a power switch having a first terminal coupled to a first node and a second terminal coupled to a second node, wherein an LED string is coupled between a DC voltage and the first node; a first resistor coupled between the second node and a ground potential; and a control chip for generating a driving signal in response to a voltage on the second node and a bandgap voltage during an activation phase of the LED driving apparatus, so as to switch the power switch and thus making the LED string to be operated under a constant current for producing light, and further comparing a detection voltage obtained in response to a voltage on the first node with a predetermined voltage, so as to stop generating the driving signal when the detection voltage is greater than the predetermined voltage.

Abstract: Embodiments described herein provide a LED lighting system and method. A transformer has a primary winding and a secondary winding. A plurality of LED strings are coupled to the secondary winding of the transformer. At least one switch is coupled to at least one of the plurality of LED strings. A controller is coupled to the at least one switch and configured to control the operation of the at least one switch such that current flows through the plurality of LED strings in an alternating manner.

Abstract: The present invention relates to an electronic device for driving a light emitting diode, which includes a switch being adapted to switch a switch-mode power converter, and controlling means being adapted for controlling the switch in response to a sensing value indicative of a current of the switch-mode power converter and for controlling by the switch the output voltage of the switched power converter and a current through the light emitting diode.

Abstract: A dimmable LED driver circuit comprises a resonant DC-DC converter coupled to an output circuit. The converter comprises a half bridge or full bridge switching circuit coupled to a resonant circuit. An output of the resonant circuit is rectified and fed to the output circuit. The output circuit may comprise at least one LED series or shunt switch for switching an LED unit on and off. A control circuit controls the switches of the switching circuit at a variable switching frequency. The control circuit is also configured for controlling the switching circuit for amplitude modulating the converter and for pulse-width modulating the converter at a first pulse-width modulation frequency lower than the switching frequency. The control circuit is may further be configured for controlling the switching of the LED switch at a second pulse-width modulation frequency lower than the switching frequency.

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 (Light-Emitting Diode) driving circuit to drive an LED module is provided. The LED driving circuit includes a converting circuit and a feedback control circuit. The converting circuit is coupled to the LED module, and converts an input voltage into an output voltage according to at least one control signal. The feedback control circuit generates the control signal to control the converting circuit to perform voltage conversion according to a feedback signal. In addition, the feedback control circuit receives a dimming signal, and is operated in a first state or a second state in response to the dimming signal, wherein the feedback control circuit adjusts the duty cycle of the control signal to have the duty cycle larger than or equal to a predetermined duty cycle in a predetermined period right after the feedback control circuit is operated from the second state to the first state.

Abstract: The present invention discloses apparatus and techniques for modular backlighting control of a display. The display includes a number of strings of LEDs. The display is divided into several sections, and each section includes one or more strings of LEDs. A local controller is assigned to each section. The local controller receives feedback signals from the strings of LEDs in its sections and controls the drive voltages and drive currents of those strings. The local controllers communicate with each other and also with the main system controller.

Abstract: The LED driver of the present invention comprises multiple LED arrays, at least one dividing diode, a power module, a driving module, at least one switch pair and a voltage sensing module. Each LED array comprises multiple LEDs connected in series. The dividing diode is mounted between adjacent LED arrays. The power module is connected to an external power source and forms a pulsating direct current (DC) voltage. The driving module receives the pulsating DC voltage outputs a constant current to the LED arrays. The voltage sensing module closes and opens the switch pairs that changes electrical configuration of the LED arrays. The LED driving method of the present invention comprises setting multiple voltage drops and at least one reference voltage; sensing an incoming voltage to compare with the reference voltage; and changing ways of connections of LED arrays based on the reference voltage and the incoming voltage.

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 emitter drive circuit for an oximeter which utilizes a single inductor for driving multiple light emitters. The inductor is connected to a switching circuit to multiple energy storage circuits, such as capacitors. These are alternately charged up, using the same inductor. Subsequently, the capacitors are alternatively discharged for their corresponding light emitters through the same inductor. Also, the magnetic susceptibility of the LED drive circuit is reduced by using magnetic flux canceling in the inductor. In one embodiment, a toroidal inductor is used with geometric symmetry and its magnetic flux. In other embodiment, a dual core closed bobbin shielded inductor is used.

Abstract: A DC-DC converter supplies an output voltage to a plurality of channels of a light emitting device array in common. A current driver has a plurality of driver units which drive the channels. Each of the driver units includes a drive transistor and a detector which detects an abnormality of a drive current. A logic unit generates digital data in response to a plurality of detection signals and supplies the same to a D/A converter. An analog reference voltage of the D/A converter is supplied to the DC-DC converter. The logic unit executes a calibration operation which determines digital data for setting the minimum output DC voltage at the normal operation of all the channels by sequential updating of the digital data.

Abstract: A LED string is divided into segments that each have a bypass-switch and a driver for the bypass-switch. The driver is powered by a supply voltage locally generated from the forward-voltages of the LEDs of the segment.

Abstract: A light-emitting diode (LED) bulb has a shell and a base attached to the shell. An LED is within the shell. A driver circuit provides current to the LED. The driver circuit has a power factor control circuit that includes a tracking circuit configured to produce a tracking signal indicative of the voltage of the supply line. The power factor control circuit also includes a switch-mode power supply (SMPS) controller having an input pin and an output pin. The tracking circuit is connected to the input pin. Based on the signal at the input pin, the SMPS controller is configured to change a duty cycle of an output signal on the output pin.

Abstract: A light-emitting-diode (LED) driving circuit and a display device include a current driving circuit, a level detector, a comparing circuit, a digital control circuit, and a power supply circuit. The level detector detects a minimum detection voltage signal having a minimum voltage level among voltage signals of first terminals of respective LED strings. The comparing circuit generates a first comparison output signal and a second comparison output signal based on a headroom-control reference voltage and the minimum detection voltage signal. The digital control circuit adjusts a duty ratio of a gate control signal in a digital mode based on the first comparison output signal, the second comparison output signal and a control clock signal. Therefore, the LED driving circuit has a small area in a semiconductor integrated circuit.

Abstract: In one aspect of the invention, a driver for driving a backlight module having a plurality of LED strings includes a random frequency multiplexer for receiving one or more PWM signals and responsively outputting a plurality of random frequency signals, a PWM dimming controller electrically coupled to the random frequency multiplexer for receiving the plurality of random frequency signals and responsively outputting a plurality of driving signals to the plurality of LED strings to drive each of the plurality of LED strings, respectively, and a switching control circuit LX electrically coupled to the random frequency multiplexer for receiving the plurality of random frequency signals and responsively outputting a plurality of switching control signals to a boost converter to regulate duty cycle ON/OFF of each of the plurality of driving signals, respectively, so as to cause each of the plurality of LED strings to emit light of a desired brightness within a desired timing cycle.

Abstract: A control IC controls a switching power supply configured to supply a driving voltage Vout to one terminal of an LED string to be intermittently driven. In the on period of the LED string, a pulse modulator generates a pulse signal having a duty ratio adjusted such that a detection voltage VLED that corresponds to the output voltage Vout of the switching power supply matches a predetermined reference voltage Vref. A driver drives a switching transistor included in the switching power supply according to the pulse signal. After transition from the on period to the off period, the pulse modulator reduces the duty ratio of the pulse signal over time.

Abstract: A power-saving light string, particularly a battery-powered light string, includes a timing controller mounted to an electrical wire of the light string. The light string is operated to intermittently supply power to bulbs of the light string in an alternate ON/OFF switching fashion that complies with visual persistency of human eyes so as to reduce power consumption.

Abstract: The present invention provides a feedback control circuit and an LED driving circuit for using the same, wherein the feedback control circuit receives a dimming signal. The dimming signal is changed between a first state and a second state. When being in the first state, the feedback control circuit controls a converter circuit to drive the LED module for lighting stably. When being in the second state, the feedback control circuit controls the converter circuit to maintain the power conversion of the converter circuit to have an output voltage outputted by the converter circuit maintained at a level close to a lighting threshold voltage of the LED module.

Abstract: A converting control circuit, adapted to control a converting circuit to convert an input voltage into an output voltage for driving a load, is provided. The converting control circuit comprises a current control circuit, a first detecting circuit, a second detecting circuit, a feedback controller and a feedback circuit. The current control circuit comprises at least one control end coupled to the load to adjust a current flowing through the load. The first detecting circuit is coupled to the current control circuit and generates a first detecting signal according to the voltage at the least one control end. The second detecting signal is coupled to the converting circuit and generates a second detecting signal according to the output voltage. The feedback circuit is coupled to the first and second detecting circuit and modulates a level of the second signal according to the first detecting signal.

Abstract: Various embodiments of the invention provide power factor correction in solid state lighting applications. In certain embodiments, an LED driver for an LED array is controlled for power factor correction by a control circuit block. The control circuit block comprises electronic circuitry that enables the input current to the LED driver to be measured and controlled. This control circuit block comprises at least one switching device that enables an alternating form of current at a particular frequency to be applied to the LED array regardless of whether the main power source is a DC or AC power source.

Abstract: A circuit for operating a light-emitting diode assembly, wherein the light-emitting diode assembly comprises a plurality of strands connected in parallel of one or more light-emitting diodes which are arranged in series and through which in the operational state a particular partial current of an operating current flowing through the light-emitting diode assembly flows, comprises a current source for providing the operating current. The circuit is designed to detect the greatest partial current and to control an operational value provided by the partial current source on the basis of said greatest partial current such that none of the partial currents exceeds a predetermined maximum current.

Abstract: A phase shift circuit includes an on signal generator, an off signal generator, and a channel signal generator. The on signal generator generates an on signal having a rising edge shifted by a predetermined phase based on a pulse width modulation (PWM) signal, the off signal generator generates an off signal based on the PWM signal and the on signal, and the channel signal generator generates a channel signal that is enabled in response to the rising edge of the on signal and disabled in response to a rising edge of the off signal.

Abstract: A regulation circuit is provided for making available a constant current supply on the basis of a transformer principle, in which there flows through the luminescent diodes a triangular a.c. current varying periodically around a d.c. current value. Circuitry is provided so that both the charging and the discharging current of an inductive reactance connected in series to the luminescent diodes, functioning as a storage choke for filtering of mains harmonics, flows as diode current through the luminescent diodes. An advantage of this method consists in a significant reduction of the overall power loss of the LED illumination module. According to one embodiment, the ceramic circuit board of the LED illumination module has a direct mains current supply, which, for protection from mechanical damage, is accommodated in a transparent housing having a highly transparent polymer mass serving as an optically active lens surface.

Abstract: A power supply unit provides a voltage, and a driving current to a series of light emitting diodes. A dimming unit adjusts a duty cycle of an original dimming signal to generate a dimming signal according to the driving current and an ideal current. A current sink coupled to the series of light emitting diodes adjusts a duty cycle of the driving current according to the dimming signal.

Abstract: A power supply unit provides a voltage, and a driving current to a series of light emitting diodes. A dimming unit adjusts a duty cycle of an original dimming signal to generate a dimming signal according to the driving current and an ideal current. A current sink coupled to the series of light emitting diodes adjusts a duty cycle of the driving current according to the dimming signal.

Abstract: An LED backlight driving circuit including a boost circuit and a transformer current balance circuit is provided. The boost circuit provides a total current for n LED strings, and the transformer current balance circuit is coupled to the LED strings and includes n?1 transformers. A first LED current-balance-circuit (CBC) includes a switching-transistor connected to a secondary-winding of a first-transformer, and an nth LED CBC includes a switching-transistor connected to a primary-winding of an (n?1)th transformer. An ith (1<i<n, n>2) LED CBC includes a switching-transistor sequentially connected to a primary-winding of an (i?1)th transformer and a secondary-winding of an ith transformer. The passive-transformers are applied in the LED driving circuit to implement current balance/equalization, such that the LED backlight driving circuit is suitable for a system with any odd or even number (greater than 1) of the LED strings connected in parallel, so as to reduce the cost of the system.

Abstract: Disclosed is a power-saving LED lighting apparatus in which the full-wave rectified wave form of the commercial power is used as the driving voltage. The LED lighting apparatus includes a rectifier circuit part which rectifies commercial power and outputs a rectified voltage; a plurality of LED arrays having a plurality of LEDs connected in series and the rectified voltage of the rectifier circuit part is supplied to an anode of the uppermost LED array; a driving part in which one terminal of each switching device for supplying or blocking a driving current to the plurality of LED arrays is connected to each anode of the plurality of LED arrays, and the other terminal thereof is connected to a cathode of the lowermost LED array; and a control part which outputs a control signal for turning on and off the switching devices according to a level of the rectified voltage.

Abstract: The present invention relates to a multiple LED driver circuit in which each LED (15, 17) is controlled by a bypass switch (19, 21). The LEDs are supplied by a switched mode power supply (8) and are connected to a constant current source to draw a predetermined current through the LEDs. The switched mode power supply is arranged to output different voltages depending on the number of switched-on LEDs. This is carried out by supplying the control signals (sw1, sw2) of the bypass switches to the switched mode power supply. In this way, the power dissipation of the constant current source can be kept at a low level.

Abstract: A resonant power supply for light-emitting devices comprises an inverter including two DC input terminals and two AC output terminals, a resonant circuit connected in series to at least one of the two AC output terminals, and an LED circuit connected in series to the resonant circuit. The inverter is configured to convert a direct current from the two DC input terminals into an alternating current through the two AC output terminals, and the LED circuit emits lights as the alternating current is applied.

Abstract: A soft-start circuit generates a soft-start voltage Vss having a voltage level that rises over time. A pulse width modulator generates a PWM signal having a duty ratio adjusted such that a feedback voltage Vout? that corresponds to the output voltage Vout of the switching power supply matches the soft-start voltage Vss. A driver circuit controls a switching element according to the PWM signal. A capacitor is arranged such that one terminal thereof is set to a fixed electric potential. A current source generates a charge current that flows intermittently in synchronization with the PWM signal so as to charge the capacitor. The soft-start circuit outputs, as the soft-start voltage Vss, a voltage that occurs at the capacitor.

Abstract: A high efficiency power drive device enabling serial connection of LED lamps thereto, which includes a power source filter circuit, an AC to DC rectifier, a power factor correction circuit and an LED constant current drive circuit. The power factor correction circuit is utilized using the so-called transition mode technique to obtain voltage required by the LED lamps when serially connected, and current control is used to achieve a state whereby the current and voltage are in the same phase. A current control IC and an externally set resistor are further used to eliminate the need to adopt any CPU (central processing unit) while accurately directly controlling the output pulse width of PWM (Pulse Width Modulation).

Abstract: Apparatus and associated methods reduce harmonic distortion of a excitation current by diverting the excitation current substantially away from a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level, and ceasing the current diversion while the excitation current or voltage is substantially above the predetermined threshold level. In an illustrative embodiment, a rectifier may receive an AC (e.g., sinusoidal) voltage and deliver unidirectional current to a string of series-connected LEDs. An effective turn-on threshold voltage of the diode string may be reduced by diverting current around at least one of the diodes in the string while the AC voltage is below a predetermined level. In various examples, selective current diversion within the LED string may extend the input current conduction angle and thereby substantially reduce harmonic distortion for AC LED lighting systems.

Abstract: An LED driving device includes a rectifier circuit, a first LED module, a first switch, a second LED module, a second switch, and a diode module. The rectifier circuit includes a pair of input terminals and first and second output terminals for receiving an AC voltage and rectifying the AC voltage to output a pulsed rectified voltage. The first LED module and first switch connected in series are electrically connected between the first and second output terminals of the rectifier circuit. The second LED module and second switch connected in series are electrically connected between the first and second output terminals of the rectifier circuit. The diode module is connected between a common node of the first LED module and the first switch and a common node of the second LED module and the second switch.

Abstract: An alternating-current (AC) light-emitting diode (LED) apparatus is disclosed. A rectifier rectifies a power AC voltage to generate a rectified voltage, which is monitored by a controller. A number of LEDs are electrically coupled between the rectified voltage and a ground. A number of switches correspondingly control at least a portion of the LEDs respectively, wherein one terminal of each switch is electrically coupled to one electrode of the corresponding LED or LEDs. The switches are controlled by the controller according to the rectified voltage.

Abstract: An electronic ballast (10), for a gas discharge lamp (18), comprises a constant current source (14) and a switch (16). A transformer (60), for use in an igniter (90) for a gas discharge lamp (18, 40), comprises a core (62) which has interconnected legs (64, 66, 68), a first secondary winding (70) around a first leg (64), a second secondary winding (72) around a second leg (66), and a primary winding (74) around a third leg (66). An igniter (90) for a gas discharge lamp (18, 40) comprises a transformer (60) as described above and a drive circuit (92) for driving the primary winding (74).

Abstract: A light-emitting diode (LED) driver circuit is provided, which includes a transistor, a current regulator, a release diode, and a voltage clamping device. The transistor is coupled in series with an LED string. The LED string is coupled between the transistor and a bus voltage. The current regulator is coupled to the transistor for regulating the current through the transistor and the LED string to a predetermined current. The release diode has an anode coupled between the LED string and the transistor. The voltage clamping device is coupled to the cathode of the release diode for clamping the voltage level at the cathode of the release diode to a predetermined voltage. The voltage clamping device protects the transistor from breakdown when the transistor is turned off for dimming control.

Abstract: There is provided a lamp driver including: a power supplying part switching an input power, supplying a driving power to at least one lamp, and controlling brightness of the at least one lamp according to a dimming signal; a signal supplying part supplying a first comparison result signal obtained by comparing a current sensing signal sensing a current flowing through the at least one lamp with a reference signal having a current level set beforehand when the dimming signal is a logic high signal, and supplying a second comparison result signal having a voltage level set beforehand when the dimming signal is a logic low signal; and a controlling part controlling the switching of the power supplying part according to a signal being supplied by the signal supplying part.