# US 2014/0192102 A1 · Backlight unit and display device having the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192102 A1 - Document ID: US20140192102A1 - Status: Published application - Kind: A1 - Application number: 13/928,582 - Filed: 2013-06-27 - Published: 2014-07-10 - Earliest claimed: 2013-01-08 - Assignees: Samsung Display Co., Ltd. - Applicants: Samsung Display Co., Ltd. - Inventors: Taegon IM; Myoung-Soo KIM; HWANWOONG LEE; Min-Soo CHOI; EUN CHUL SHIN; Dae-Sik LEE - Web page: https://patentgrep.com/patent/US20140192102A1 ## CPC - G09G 5/10: Intensity circuits - H05B 45/46: having LEDs disposed in parallel lines - G09G 3/3406: {Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336)} - H05B 45/38: using boost topology - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract A backlight unit includes a power converter configured to generate a light source driving voltage in response to a voltage control signal, a plurality of light emitting diode strings, where each of the light emitting diode strings receives the light source driving voltage through a first terminal thereof, a plurality of transistors corresponding to the light emitting diode strings, where each of the transistors includes: a first electrode connected to a second terminal of a corresponding light emitting diode string thereof; a second electrode; and a control electrode, and a controller connected to the control electrode and the second electrode, where the controller outputs a plurality of current control signals to control electrodes of the transistors and generate the voltage control signal, where the controller generates an over-current detection signal when any one of the current control signals has a pulse width greater than a predetermined reference width. ## Claims ### Claim 1 A backlight unit comprising: a power converter configured to generate a light source driving voltage in response to a voltage control signal; a plurality of light emitting diode strings, wherein each of the light emitting diode strings receives the light source driving voltage through a first terminal thereof; a plurality of transistors corresponding to the light emitting diode strings, wherein each of the transistors comprises: a first electrode connected to a second terminal of a corresponding light emitting diode string; a second electrode; and a control electrode; and a controller connected to the control electrode and the second electrode of each of the transistors, wherein the controller outputs a plurality of current control signals to control electrodes of the transistors and generate the voltage control signal, wherein the controller generates an over-current detection signal when any one of the current control signals has a pulse width greater than a predetermined reference width. ### Claim 2 (depends on 1) The backlight unit of claim 1, wherein the controller comprises an over-current detection circuit which outputs the over-current detection signal when the any one of the current control signals has the pulse width greater than the predetermined reference width, and the controller controls the power converter such that the light source driving voltage is not generated when the over-current detection signal is output from the over-current detection circuit. ### Claim 3 (depends on 2) The backlight unit of claim 2, wherein the controller stops generating the voltage control signal such that the light source driving voltage is not generated when the over-current detection signal is output from the over-current detection circuit. ### Claim 4 (depends on 2) The backlight unit of claim 2, wherein the controller sets the voltage control signal to a predetermined level such that the light source driving voltage is not generated when the over-current detection signal is output from the over-current detection circuit. ### Claim 5 (depends on 2) The backlight unit of claim 2, wherein the over-current detection circuit comprises: a plurality of diodes corresponding to the transistors, wherein each of the diodes comprises: a first terminal connected to the control electrode of a corresponding transistor thereof; and a second terminal; a first resistor connected between a first node therein, which is connected to the second terminals of the diodes, and a source voltage; a second resistor connected between the first node and a ground voltage; a third resistor connected between the first node and a second node therein; and a first comparator which receives a voltage of the second node and a first reference voltage, and outputs the over-current detection signal through an output terminal thereof. ### Claim 6 (depends on 5) The backlight unit of claim 5, wherein the over-current detection circuit further comprises: a fourth resistor connected between the output terminal of the first comparator and the source voltage; and a fifth resistor connected between the output terminal of the first comparator and the source voltage. ### Claim 7 (depends on 2) The backlight unit of claim 2, wherein the controller further comprises: a voltage control signal generator which generates the voltage control signal in response to the current control signals; and a switching circuit connected between a source voltage and the voltage control signal generator, wherein the switching circuit operates in response to the over-current detection signal. ### Claim 8 (depends on 7) The backlight unit of claim 7, wherein the controller further comprises: a plurality of current controllers corresponding to the light emitting diode strings, respectively, wherein each of the current controllers is connected to a second terminal of a corresponding light emitting diode string, and generates a current control signal of the current control signals to control a current of the corresponding light emitting diode string. ### Claim 9 (depends on 8) The backlight unit of claim 8, wherein each of the current controllers generates the current control signal having a pulse width corresponding to a forward driving voltage of the corresponding light emitting diode string. ### Claim 10 (depends on 9) The backlight unit of claim 9, further comprising: a plurality of pull-down resistors corresponding to the transistors, wherein each of the pull-down resistors comprises: a first end connected to the second electrode of a corresponding transistor; and a second end connected to a ground voltage. ### Claim 11 (depends on 10) The backlight unit of claim 10, wherein each of the current controllers comprises: a resistor connected between the first end of a corresponding pull-down resistor of the pull-down resistors and a third node therein; a second comparator which receives a voltage of the third node therein and a second reference voltage, and outputs a voltage corresponding to a difference between the voltage of the third node and the second reference voltage to a fourth node therein; a capacitor connected between the third node and the fourth node; and a third comparator which receives a voltage of the fourth node and a third reference voltage, and outputs the current control signal. ### Claim 12 (depends on 11) The backlight unit of claim 11, wherein the third reference voltage is a triangular wave or a sawtooth wave, which has a predetermined frequency. ### Claim 13 A display device comprising: a display panel comprising a plurality of pixels; a driving circuit which controls the display panel to display an image on the display panel; and a backlight unit which provides light to the display panel, wherein the backlight unit comprises: a power converter which generates a light source driving voltage in response to a voltage control signal; a plurality of light emitting diode strings, wherein each of the light emitting diode strings receives the light source driving voltage through a first terminal thereof; a plurality of transistors corresponding to the light emitting diode strings, wherein each of the transistors comprises: a first electrode connected to a second terminal of a corresponding light emitting diode string; a second electrode; and a control electrode; a plurality of pull-down resistors corresponding to the transistors, wherein each of the pull-down resistors comprises: a first end connected to the second electrode of a corresponding transistor of the transistors; and a second end connected to a ground voltage; and a controller connected to the control electrode and the second electrode to output a plurality of current control signals to the control electrode of each of the transistors and generate the voltage control signal, wherein the controller outputs an over-current detection signal when any one of the current control signals has a pulse width greater than a predetermined reference range. ### Claim 14 (depends on 13) The display device of claim 13, wherein the controller controls the power converter such that the light source driving voltage is not generated when the over-current detection signal is activated. ### Claim 15 (depends on 14) The display device of claim 14, wherein the controller stops generating the voltage control signal such that the light source driving voltage is not generated when the over-current detection signal is output from the over-current detection circuit. ### Claim 16 (depends on 14) The display device of claim 14, wherein the controller sets the voltage control signal to a predetermined level such that the light source driving voltage is not generated when the over-current detection signal is output from the over-current detection circuit. ### Claim 17 (depends on 14) The display device of claim 14, wherein the over-current detection circuit comprises: a plurality of diodes corresponding to the transistors, wherein each of the didoes comprises: a first terminal connected to the control electrode of a corresponding transistor of the transistors; and a second terminal; a resistor connected between a first node therein, which is connected to the second terminal of the diodes, and a source voltage; a second resistor connected between the first node and the ground voltage; a third resistor connected between the first node and a second node therein; and a first comparator which receives a voltage of the second node and a first reference voltage, and outputs the over-current detection signal through an output terminal thereof. ### Claim 18 (depends on 14) The display device of claim 14, wherein the controller further comprises: a voltage control signal generator which generates the voltage control signal in response to the current control signals; and a switching circuit connected between the source voltage and the voltage control signal generator, wherein the switching circuit operates in response to the over-current detection signal. ### Claim 19 (depends on 18) The display device of claim 18, wherein the controller further comprises: a plurality of current controllers corresponding to the light emitting diode strings, wherein each of the current controllers is connected to a second terminal of a corresponding light emitting diode string, and generates a current control signal of the current control signals to control a current of the corresponding light emitting diode string. ### Claim 20 (depends on 19) The display device of claim 19, wherein each of the current controllers generates the current control signal having a pulse width corresponding to a forward driving voltage of the corresponding light emitting diode string.