CN113785351B - LED backlight capable of detecting faults - Google Patents

LED backlight capable of detecting faults Download PDF

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Publication number
CN113785351B
CN113785351B CN202180001289.7A CN202180001289A CN113785351B CN 113785351 B CN113785351 B CN 113785351B CN 202180001289 A CN202180001289 A CN 202180001289A CN 113785351 B CN113785351 B CN 113785351B
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signal
control signal
light emission
outputs
section
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CN113785351A (en
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金钟善
李龙云
尹炳震
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Beijing Xinneng Electronic Technology Co ltd
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Beijing Xinneng Electronic Technology Co ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

The LED backlight according to the present technology includes: a light emitting device; a data control unit that receives input control signals for embedding the light emission data, the clock signal, and the activation signal at different levels, and then outputs a luminance control signal for controlling luminance and a light emission time control signal for controlling luminance time; a light emission control section that receives the inputted luminance control signal and light emission time control signal and drives the light emitting device to emit light with a luminance corresponding to the luminance control signal for a light emission time corresponding to the light emission time control signal; and a fault detection section that detects a voltage at a node connected to the light emission control section and the light emitting device and outputs a fault signal corresponding to whether the light emitting device has failed, wherein the data control section outputs the fault detected by the fault detection section as a fault detection signal.

Description

LED backlight capable of detecting faults
Technical Field
The present invention relates to an LED backlight unit capable of detecting a failure.
Background
Recently, there is a trend in realizing the display of the outside and the inside of a business, to increase the display resolution while enlarging the display area. In addition, LEDs are employed as light emitting devices in order to achieve high brightness, high contrast, and good color reproducibility.
For LED backlights (back-lights) for LED displays and LCD display panels, the narrower the spacing between individual LEDs, the denser the number of pixels. As the brightness of the individual LEDs increases, the sharpness of the overall display will also increase, and the image quality will also increase. In addition, a better effect in terms of physical size or cost can be obtained by implementing the LEDs included in the LED backlight part as an active matrix type. The LED backlight can obtain a high contrast (contrast) by performing local dimming (local dimming) of the individually driven light emitting devices.
Disclosure of Invention
Technical problem to be solved
A large area and/or high density LED array is a backlight unit (BLU) configured with a large number of light emitting devices and circuit devices for driving the light emitting devices. Accordingly, if a large area and/or high density light emitting device array fails, it is difficult to determine whether the failure occurs.
The present invention aims to solve the above-described problems of the prior art. That is, one of the problems to be achieved by the present invention is to provide a light emitting device apparatus capable of easily identifying and determining a failure when the failure occurs.
Technical proposal for solving the problems
The LED backlight according to the present technology includes: a light emitting device; a data control unit that receives input light emission data, a clock signal, and a control signal in which an activation signal is embedded at different levels, and then outputs a luminance control signal for controlling luminance and a light emission time control signal for controlling luminance time; a light emission control section that receives an input luminance control signal and a light emission time control signal, and drives the light emitting device to emit light with a luminance corresponding to the luminance control signal for a light emission time corresponding to the light emission time control signal; and a fault detection section that detects a voltage at a node connected to the light emission control section and the light emitting device and outputs a fault signal corresponding to whether the light emitting device has failed, wherein the data control section outputs the fault detected by the fault detection section as a fault detection signal.
As an example of the LED backlight unit, the data control unit includes: a signal separation section to which the control signal is input, and from which a clock signal and an activation signal are separated and output, respectively; and a data input/output control section. Which is controlled according to an input/output control signal and receives provided light emitting data or outputs a fault signal to the outside; and a data processing part which provides input/output control signals, receives the provided activation signals, clock signals and light emitting data, and forms and outputs brightness control signals and light emitting time control signals.
As an example of the LED backlight unit, the control signal is embedded with: an activation signal that swings (swing) between a first level and a second level that is greater than the first level; and a clock signal including a plurality of pulses swinging between a second level and a third level greater than the second level, wherein the signal separation section includes: an activation signal isolation circuit that separates an activation signal by including a transistor having a threshold voltage between a first level and a second level, and outputs the separated activation signal to swing (swing) between the first level and a third level; a clock signal separation circuit that separates a clock signal by including a transistor having a threshold voltage between a second level and a third level, and outputs the separated clock signal to swing between the first level and the third level.
As an example of the LED backlight unit, the data input/output control unit includes: a first switch that receives input light-emitting data from the input/output bus or outputs a failure detection signal to the input/output bus by being connected to the input/output bus, and is turned on when an input/output control signal is in a first state after being connected to the input/output bus to transmit the light-emitting data; and a second switch which is turned on when the input/output control signal is in a second state complementary to the first state after being connected to the input/output bus to connect the fault detection signal to the input/output bus.
As an example of the LED backlight unit, the data processing unit includes an internal control signal forming unit including: a first SR latch to which an activation signal is input; a first counter that counts the number of pulses included in the clock signal after being activated as the output signal of the first SR latch; and a control signal forming part including a first operation part which forms and outputs a short-circuit fault passing signal and an open-circuit fault passing signal internally when a count result of the first counter is supplied and the count result is greater than the number of bits of the light emitting data, and during periods of the short-circuit fault passing signal and the open-circuit fault passing signal, the data input/output control part forms and outputs an input/output control signal so that the fault signal is output to the outside, and outputs an internal control signal forming part stop signal after outputting the short-circuit fault passing signal and the open-circuit fault passing signal, wherein the internal control signal forming part stop signal is supplied to the first SR latch so as to deactivate the first counter.
As an example of the LED backlight unit, the light emission data is serial (serial) data, and the data processing unit includes: and a luminance control signal forming section including a shift register which receives input light emission data and forms each bit (bit) in parallel and then outputs the same, and a register which outputs each bit (bit) of the light emission data output from the shift register according to a stop signal of the internal control signal forming section, wherein an output signal of the register is a luminance control signal.
As an example of the LED backlight unit, the data processing unit includes a light emission time control signal forming unit including: a second SR latch inputted with an internal control signal to form a stop signal; a second counter that counts the number of pulses included in the clock signal after being activated as an output signal of the SR latch; and a second operation section that is supplied with a count result of the second counter and a brightness control signal, and that forms and outputs a light emission time control signal that changes a pulse width according to a value of the brightness control signal, and after outputting the light emission time control signal, forms and outputs a stop signal of the light emission control signal forming section, wherein the light emission control signal forming section stop signal is supplied to the second SR latch to deactivate the second counter.
As an example of the LED backlight unit, the second operation unit forms the same pulse width as the light emission time control signal when the luminance control signal is greater than or equal to the threshold value, and forms the pulse width of the light emission time control signal to be proportional to the value of the luminance control signal when the luminance control signal is less than the threshold value.
As an example of the LED backlight unit, the light emission control unit includes: a string resistor (resistor string) connected between an upper limit voltage and the lower limit voltage, and including a plurality of resistors distributing a voltage difference between the upper limit voltage and the lower limit voltage to provide a plurality of gray scale voltages; a digital-to-analog converter (DAC) that receives a brightness control signal and outputs a gray-scale voltage to emit light having a corresponding brightness; a driving circuit section that receives a grayscale voltage and drives the light emitting device at a luminance corresponding to the grayscale voltage; and a driving time control section that receives the supplied light emission time control signal, and the driving circuit section controls the light emitting device so that the light emitting device emits light for a time corresponding to the light emission time control signal.
As an example of the LED backlight unit, the failure detection unit includes: a first comparator that outputs a short-circuit fault signal corresponding to whether or not a short-circuit fault has occurred by comparing a voltage at a node to which the light emission control section and the light emitting device are connected with a short-circuit voltage; a first latch for latching the short-circuit fault signal; a first flip-flop that samples and outputs the latched short-circuit fault signal as a short-circuit fault passing signal; and a switch that is turned on to output a short-circuit fault signal after the short-circuit fault passing signal. Wherein the short-circuit fault signal is provided as a fault signal to the data control section.
As an example of the LED backlight unit, the failure detection unit includes: a second comparator that outputs a short-circuit fault signal corresponding to whether or not a short-circuit fault has occurred by comparing a voltage at a node to which the light emission control section and the light emitting device are connected with the short-circuit voltage; a second latch for latching the short-circuit fault signal; a second flip-flop that samples and outputs the latched short-circuit fault signal as a short-circuit fault passing signal; and a switch that is turned on to output a short-circuit fault signal after the fault pass signal. Wherein the short-circuit fault signal is provided as a fault signal to the data control section.
As an example of the LED backlight unit, the failure detection unit outputs any one or more of a short-circuit failure signal for detecting a short-circuit failure of the light emitting device and a short-circuit failure signal for detecting a short-circuit failure, and the failure detection unit outputs the short-circuit failure signal and the open-circuit failure signal based on the short-circuit failure pass signal, the open-circuit failure pass signal, and the output short-circuit provided by the data control unit.
In one example of the LED backlight unit, the LED backlight unit periodically performs a programming phase in which light emission data is input to the data control unit, a failure output phase in which the failure detection unit outputs a failure signal, and a light emission phase in which the light emitting device emits light.
As an example of an LED backlight, in the light emitting stage, the clock period has a larger value than the clock periods of the programming stage and the failure output stage.
As an example of the LED backlight section, LED pixel packages are arranged in a plurality of rows and a plurality of columns, and are driven by an active matrix.
As an example of the LED backlight section, the same control signal is supplied to the LED pixel packages arranged in a plurality of rows, and the same light emission data is supplied to the LED pixel packages arranged in a plurality of columns.
Effects of the invention
According to the present technology, there is provided an advantage in that the LED backlight part can detect a failure of the light emitting device while emitting light.
In addition, according to an example of the present technology, there is provided an advantage in that the LED backlight can emit light in the form of an active matrix.
Drawings
Fig. 1 is a block diagram showing an outline of an LED backlight 1 according to the present invention.
Fig. 2 is a block diagram schematically showing the data control section 10.
Fig. 3 (a) is a schematic circuit diagram of the signal separation section 100; fig. 3 (B) is a diagram showing an outline of the control signal (s_sig) and the activation signal (ON) and the burst (s_out) outputted from the signal separation section 100.
Fig. 4 is a schematic circuit diagram of the data input/output control section 110.
Fig. 5 is a diagram showing an overview of the data processing section 120, and fig. 6 is a timing chart for explaining an operation of the data processing section 120.
Fig. 7 is a diagram showing an outline of the light emission control unit 20.
Fig. 8 is a diagram showing a relationship between a current ILED flowing through the light emitting device according to the luminance control signal (DO [9:0 ]) and the light emission time control signal (PWM).
Fig. 9 is a diagram showing an outline of the fault detection unit 30.
Fig. 10 is a diagram showing an outline of a control signal (s_sig) supplied to an LED backlight according to the present invention.
Fig. 11 is a diagram of an LED backlight 1 configured in an active matrix form according to the present invention.
Detailed Description
The LED backlight according to the present invention is characterized by comprising: a light emitting device; a data control unit that receives input light emission data, a clock signal, and a control signal in which an activation signal is embedded at different levels, and then outputs a luminance control signal for controlling luminance and a light emission time control signal for controlling luminance time; a light emission control section that receives the inputted luminance control signal and the light emission time control signal, and drives the light emitting device to emit light with a luminance corresponding to the luminance control signal for a light emission time corresponding to the light emission time control signal; and a fault detection section that detects a voltage at a node connected to the light emission control section and the light emitting device and outputs a fault signal corresponding to whether the light emitting device has failed, wherein the data control section outputs the fault detected by the fault detection section as a fault detection signal.
Hereinafter, an LED backlight according to the present invention will be described with reference to the accompanying drawings. Fig. 1 is a block diagram showing an outline of an LED backlight 1 according to the present invention. Referring to fig. 1, an LED backlight 1 according to the present technology includes: a light emitting device 40; a data control unit 10 that receives input control signals (S_SIG) and light emission data (DA_OUT) in which light emission data, a clock signal (CLK), and an activation signal (ON) are embedded at different levels, and then outputs a light emission time control signal (PWM) for controlling a luminance (DO [9:0 ]) and a luminance time; a light emission control section 20 that receives an input luminance control signal (DO [9:0 ]) and a light emission time control signal (PWM), and drives the light emitting device 40 to emit light with a luminance corresponding to the luminance control signal (DO [9:0 ]) for a light emission time corresponding to the light emission time control signal (DO [9:0 ]); and a fault detection section 30 that detects a voltage at a node connected to the light emission control section 20 and the light emitting device 40 and outputs a fault signal (da_ft) corresponding to whether the light emitting device has failed, wherein the data control section 10 outputs the fault detected by the fault detection section 30 as a fault detection signal.
Fig. 2 is a block diagram schematically showing the data control section 10. Referring to fig. 2, the data control unit 10 includes: a signal separation unit 100 to which a control signal (s_sig) is input, and which separates and outputs a clock signal (CLK) and an activation signal (ON) from the control signal (s_sig), respectively; a DATA input/output control section which is controlled in accordance with an input/output control signal (da_io) and receives input light emission DATA (da_out) from a DATA input/output bus (DATA) or outputs a failure signal (da_ft) to the DATA input/output bus (DATA); and a data processing part 120 that provides an input/output control signal (DA_IO), and forms and outputs a luminance control signal (DO [9:0 ]) and a light emission time control signal (PWM) after receiving the input light emission data (DA_OUT).
Fig. 3 (a) is a schematic circuit diagram of the signal separation section 100, and fig. 3 (B) is a diagram showing an outline of the control signal (s_sig) and the activation signal (ON) and the pulse train (s_out) output from the signal separation section 100;
referring to fig. 3 (a) and 3 (B), the control signal (s_sig) may swing (swing) between a first level, a second level, and a third level. As an example, the first level may be a ground voltage (GND) level, the third level may be a driving Voltage (VCC) level, and the second level may be a level (VIH) that is larger than a threshold voltage of the NMOS transistor included in the signal separation section 100, but smaller than the third level, and may be less than twice the threshold voltage of the NMOS transistor. As an example, as shown in fig. 3, the second level (VIH) may have a voltage level greater than 1.0V.
The control signal (s_sig) is a signal embedded with a pulse sequence comprising: an activation signal swinging between a ground voltage (GND) and a second level (VIH); and a pulse that swings between a second level (VIH) and a third level that is a driving Voltage (VCC).
The signal separation unit 100 includes: an activation signal separation circuit 112 for separating the activation signal (ON) from the control signal (s_sig); a clock signal separation circuit 114 for separating the clock signal (CLK) from the control signal (s_sig).
The activation signal separation circuit 112 is connected to an inverter (I1) Schmitt Trigger (ST) including a resistor (Ra) and a transistor (N1) having a threshold voltage between a first level and a second level and an inverter I2 in cascade. The threshold voltage of the transistor (N1) is greater than the first level but less than the second level. Accordingly, if the control signal (s_sig) of the first level is input to the inverter I1, the transistor N1 is blocked to output the logic high signal of the third level. However, if the transistor N1 is input with the second level or the third level control signal (s_sig), it is turned on. Accordingly, the inverter I1 outputs a logic low signal of the first level.
Schmitt trigger (schmitt trigger) is a circuit that is unresponsive to transient noise due to the characteristic of an output response having a hysteresis curve according to the magnitude and direction of an input, and is characterized in that the response of the output has a relatively high threshold voltage when the input rises and a relatively low threshold voltage when the input falls.
The output of the Schmitt Trigger (ST) is a signal supplied to the inverter I2 and swinging between a first level and a third level. The output of the inverter I2 is an activation signal (ON) that controls activation of the subsequent light emission control section 20.
The clock signal separation circuit 114 may include inverters I3, I4 connected in cascade, and the inverter I3 of the first stage is connected to a ground voltage with a diode-connected NMOS transistor (N3) connected therebetween. The NMOS transistor (N4) included in the inverter I3 is turned on at a voltage by adding the threshold voltage of the diode-connected NMOS transistor (N3) to the threshold voltage of the NMOS transistor (N4).
As described above, the voltage that adds the threshold voltage of the NMOS transistor (N3) and the threshold voltage of the NMOS transistor (N4) is greater than the second level. Accordingly, if the control signal (s_sig) having the first and second levels is supplied to the inverter (I3), the NMOS transistor (N4) is not turned on, and the inverter (I3) outputs a logic high signal of the third level. However, if the control signal (s_sig) having the third level is supplied to the inverter (I3), the NMOS transistor (N4) is turned on, and the inverter (I3) outputs a logic low signal of the first level. Accordingly, the pulse sequence embedded in the control signal (s_sig) can be separated. The inverter (I4) inverts the output signal of the inverter (I3) and outputs a clock signal (CLK) swinging between a first level and a third level.
Fig. 4 is a schematic circuit diagram of the data input/output control section 110. Referring to fig. 4, the DATA input/output control part 110 is connected to the DATA input/output bus (DATA), and includes a first switch (SW 1) and a second switch (SW 2) controlled by an input/output control signal (da_io). The first switch (SW 1) may be a semiconductor switch turned on by an input/output control signal (da_io) of a logic low state, and the second switch (SW 2) may be a semiconductor switch turned on by an input/output control signal (da_io) of a logic high state. As another example, the first switch (SW 1) may be a semiconductor switch turned on by an input/output control signal (da_io) of a logic high state, and the second switch (SW 2) may be a semiconductor switch turned on by an input/output control signal (da_io) of a logic low state.
The first switch SW1 is turned on and supplies the light emitting DATA (da_out) supplied through the DATA input/output bus (DATA) to the input buffer 113. The input buffer 113 outputs the light emission data (da_out) to the data processing section 120. The output buffer 115 buffers and outputs the fault signal (da_ft) supplied from the fault detection section 30, and outputs the fault signal (da_ft) to the DATA input/output bus (DATA) after the second switch (SW 2) is turned on.
Fig. 5 is a diagram showing an overview of the data processing section 120, and fig. 6 is a timing chart for explaining an operation of the data processing section 120. Referring to fig. 5 and 6, the data processing section 120 includes an internal control signal forming section 122, a light emission time control signal forming section 124, and a luminance control signal forming section 126.
The internal control signal forming unit 122 includes a first SR latch (SRa), a first counter (122 b), and a first arithmetic unit (122 c). The first SR latch (SRa) outputs a logic high state after receiving an input activation signal (ON). The first counter (122 b) is activated by an output signal of the first SR latch (SRa), and counts and outputs the number of pulses included in the clock signal (CLK).
The first operation unit (122 c) receives the input count result of the first counter (122 b), and when the count result is greater than the number of bits of the light emission data (DA_OUT), forms and outputs a short-circuit fault passing signal (SH_EN) and an open-circuit fault passing signal (OP_EN). In the illustrated embodiment, since the light emitting data (da_out) is 10 bits, after the logic high state open fault pass signal (sh_en) is formed and outputted when the count result of the first counter 122b corresponds to 11, the logic high state short fault pass signal (op_en) is formed and outputted. As an embodiment, the short-circuit fault pass signal (sh_en) turns on the fifth switch SW5 short-circuited in the circuit fault detection section 320 (see fig. 9), thereby outputting the short-circuit fault signal (sh_ft) in which the short-circuit fault is detected as the fault signal (da_ft). In addition, the open fault pass signal (op_en) turns on the sixth switch (SW 6) included in the open fault detection section 340 (see fig. 9), so that the open fault signal (op_ft) in which the open fault is detected is output as the fault signal (da_ft).
The first operation part (122 c) outputs a fault signal (da_ft) of the short fault signal (sh_ft, see fig. 9) and an open fault signal (op_ft, see fig. 9) formed by the fault detection part 30 through the DATA input/output bus (DATA), and forms an input/output control signal (da_io) and outputs it to the DATA input/output control part 110 in a time of outputting the short fault pass signal (sh_en) and the open fault pass signal (op_en).
The first arithmetic unit (122 c) outputs the short-circuit fault passing signal (SH_EN) and the open-circuit fault passing signal (OP_EN), and then forms and outputs an internal control signal forming unit stop Signal (STOPPA) for deactivating the internal control signal forming unit 122. When the first counter 122b counts 13, an internal control signal stop Signal (STOPA) may be output and provided to a reset input of the first SR latch (SRa) to deactivate the first counter 122 b.
The luminance control signal forming section 126 includes a shift register, a register (126 a), an and gate, and a third SR latch (SRc). The AND gate masks the clock signal (CLK) with the output signal of the third SR latch (SRc). If an enable signal (ON) of a logic high state is provided to the SET input of the third SR latch (SRc), the third SR latch (SRc) outputs a logic high state, and thus the and gate outputs a shift_clk signal, and the SHIFT register sequentially stores and outputs each bit of the light emitting data (da_out). Then, with the output control signal (da_io) provided in a logic high state, the third SR latch (SRc) outputs a logic low state to mask the clock signal.
As shown in fig. 6, after the activation signal (ON) is supplied, the first operation section (122 c) included in the internal control signal forming section 122 counts the pulses included in the clock by the total number of bits of the light emission data (da_out), and then outputs the input/output control signal (da_io), so that all bits of the light emission data (da_out) are stored in the shift register.
The register 126a samples and outputs each bit output from the shift register as an internal control signal forming part stop signal (stop). In the illustrated embodiment, the light emitting data (da_out) is serial data of 10 bits in total, and the luminance control signals (DO [9:0 ]) formed and output by the luminance control signal forming section 126 are 10-bit parallel signals in total.
The emission time control signal forming section 124 includes a second SR latch (SRb), a second counter (124 b), and a second arithmetic section (124 c). The second SR latch (SRb) outputs a logic high state by providing an internal control signal forming part stop signal (stop) to the SET input. The number of pulses included in the clock signal (CLK) is counted by a second SR latch (SRb) activated to a logic high state by a second counter (124 b), and is output to a second operation section (124 c).
The second operation unit (124 c) is supplied with the count result (CNTB [3:0 ]) of the second counter (124 b) and the luminance control signal (DO [9:0 ]), and outputs a light emission time control signal (PWM) having a pulse width according to the value of the luminance control signal (DO [9:0 ]).
In one embodiment, when the value of the brightness control signal (DO [9:0 ]) is greater than or equal to the threshold value, the second operation portion (124 c) may form and output a light emission time control signal (PWM) such that the light emitting device 40 emits light for a predetermined time. However, when the luminance control signal (DO [9:0 ]) is less than the threshold value, the second operation portion (124 c) may set the light emission time to output the light emission time control signal (PWM) such that the light emitting device 40 emits light in proportion to the value of the luminance control signal (DO [9:0 ]). The second operation unit (124 c) outputs a light emission time signal (PWM) in a logic low state if the value of the supplied brightness control signal (DO [9:0 ]) is 0.
In the example shown in FIG. 6, the threshold is 16 decimal, and the brightness control signals (DO [9:0 ]) are greater than or equal to the threshold 16. When the count result (CNTB [3:0 ]) of the second counter 124b is 1, the second operation part (124 c) outputs a logic high state, and when the count result (CNTB [3:0 ]) is 15, a logic low state is outputted to form and output a light emission time control signal (PWM), so that the light emitting device 40 emits light for a total of 14 clock cycles.
In an example not shown, in the example shown in fig. 6, the threshold value is 16 in decimal, if the brightness control signal (DO [9:0 ]) is smaller than the threshold value 16, and when the count result (CNTB [3:0 ]) of the second counter 124b is 1, the second operation portion 124c outputs a logic high state, and when the count result (CNTB [3:0 ]) is the decimal value +1 of the brightness control signal (DO [9:0 ]), a logic low state is outputted to form and output the light emission time control signal (PWM). Accordingly, if the brightness control signal (DO [9:0 ]) is less than 16, the pulse width of the light emission time control signal (PWM) is proportional to the value of the brightness control signal (DO [9:0 ]).
If the count result (CNTB [3:0 ]) of the second counter (124 b) reaches 15, the second operation unit (124 c) forms a light emission control signal forming unit stop signal (STOP B) and outputs the signal to the RESET input of the second SR latch (SRb). Accordingly, the second SR latch (SRb) outputs a logic low, and the second counter (124 b) is deactivated.
Fig. 7 is a diagram showing an outline of the light emission control unit 20. Referring to fig. 7, the light emission control section 20 includes a register string (210), a digital-to-analog converter 220, a driving circuit section 240, and a driving time control section 230.
The resistor string 210 includes a plurality of resistors connected in series between an upper limit Voltage (VREF) and a lower limit voltage (GND). The serially connected resistors distribute and output a voltage difference between an upper limit Voltage (VREF) and a lower limit voltage (GND). A plurality of voltages (V0, V1,) allocated and output by the register string 210 are supplied to the light emitting device 40 to determine a light emission level (gradation).
The digital-to-analog converter 220 receives the input luminance control signals (DO [9:0 ]), and outputs a gray-scale voltage (dac_out) corresponding to the luminance control signals (DO [9:0 ]) among the plurality of voltages (V0, V1,... In one embodiment, the digital-to-analog converter 220 distributes and outputs a plurality of voltages (V0, V1,..v 255) when the decimal value corresponding to the input brightness control signal (DO [9:0 ]) is 15 to 255. In contrast, when the decimal value corresponding to the luminance control signal ((DO [9:0 ]) is 0 to 14, V15 will be output to dac_out no matter what value the luminance control signal (DO [9:0 ]) has in the corresponding range.
As shown in fig. 7, the output (dac_out) of the digital-to-analog converter 220 should be supplied to the control electrode of the light emitting device driving transistor (M1) to control the turn-on, which may be because the light emitting device driving transistor (M1) cannot be turned on at a voltage lower than V15. Accordingly, the lower limit voltage output from the digital-to-analog converter 220 may correspond to a voltage that turns on the light emitting device driving transistor (M1) included in the driving circuit part 240.
The driving time control part 230 receives the supplied light emitting time control signal (PWM) and controls the turn-on of the third switch (SW 3) and the fourth switch (SW 4) for a time corresponding to the pulse width of the driving time control signal (PWM). As an embodiment, the driving time control part 230 blocks the third switch (SW 3) and turns on the fourth switch (SW 4) to supply the ground voltage to the control electrode of the light emitting device driving transistor (M1). Accordingly, the light emitting device driving transistor (M1) is blocked.
The driving time control part 230 turns on the third switch (SW 3) and blocks the fourth switch (SW 4) for a time corresponding to the pulse width of the driving time control signal PWM. With the fourth switch (SW 4) blocked and the third switch (SW 3) turned on, the output of the operational amplifier 242 is supplied to the control electrode of the light emitting device driving transistor (M1), so that the light emitting device driving transistor (M1) is turned on.
In addition, the output signal (dac_out) of digital-to-analog converter 220 provided as the non-inverting input of operational amplifier 242 is replicated as an inverting input. The replicated output signal (DAC_OUT) is provided to one end of a current limiting resistor (R). Accordingly, iled=dac_out/R current flows through the light emitting device.
Fig. 8 is a diagram showing a relationship between a current ILED flowing through the light emitting device according to the luminance control signal (DO [9:0 ]) and the light emission time control signal (PWM). Referring to fig. 8, it can be confirmed that when the value corresponding to the brightness control signal (DO [9:0 ]) is greater than or equal to the threshold value, the current flowing through the light emitting device increases. When the light emitting device is a Light Emitting Diode (LED), the brightness of the emitted light is proportional to the current. Accordingly, it was confirmed that the brightness of the light emitted by the light emitting device was controlled according to the value of the brightness control signal (DO [9:0 ]).
Further, it was confirmed that when the value of the luminance control signal (DO [9:0 ]) is smaller than the threshold value, the pulse width of the light emission time control signal (PWM) is changed according to the value of the luminance control signal (DO [9:0 ]).
Fig. 9 is a diagram showing an outline of the fault detection unit 30. The fault detection section 30 includes a short fault (short fault) detection section 320 for detecting a short fault and an open fault detection section 340 for detecting an open fault.
The short-circuit fault detection section includes a comparator 322, a latch 324, a flip-flop 326, and a fifth switch (SW 5). The voltage of the node to which the light emission control unit 20 and the light emitting device 40 are connected is supplied as one input of the comparator 322, and the short-circuit Voltage (VSHORT) is supplied as the other input, and the comparator 322 compares and outputs the voltage of the node to which the light emission control unit 20 and the light emitting device 40 are connected and the magnitude of the short-circuit Voltage (VSHORT). If the voltage of the node connected to the light emission control part 20 and the light emitting device 40 is greater than the short fault Voltage (VSHORT), it may be determined that a short fault exists in the light emitting device 40.
The comparator 322 outputs a short-circuit fault signal (sh_ft) corresponding to the comparison result to the latch 324, and the latch 324 latches and outputs the short-circuit fault signal (sh_ft) as a light emission time control signal (PWM). The flip-flop 326 samples and outputs the short-circuit fault signal (sh_ft) as a short-circuit fault pass signal (sh_en), and supplies the short-circuit fault to the pass signal (sh_en) fifth switch (SW 5) to output the short-circuit fault signal (sh_ft) as a fault signal (da_ft).
The open fault detection section includes a comparator 342, a latch 344, a flip-flop 346, and a sixth switch (SW 6). The voltage of the node of the light emission control section 20 and the light emitting device 40 is connected as one input of the comparator 342, and an open circuit Voltage (VOPEN) is supplied as the other input. The comparator 342 compares and outputs the voltage of the node to which the light emission control section 20 and the light emitting device 40 are connected and the magnitude of the open circuit Voltage (VOPEN). If the voltage of the node to which the light emission control section 20 and the light emitting device 40 are connected is lower than the open circuit Voltage (VOPEN), it can be determined that an open fault (open fault) exists in the light emitting device 40.
The latch 344 outputs an open circuit fault signal (op_ft) corresponding to the comparison result to the latch 344, and the latch 344 latches and outputs the open circuit fault signal (op_en) as a light emission time control signal (PWM). The flip-flop 346 samples and outputs the open fault signal (op_ft) as an open fault passing signal (op_en), and supplies the open fault passing signal (op_en) to the sixth switch (SW 6) to output the open fault signal (op_en) as a fault signal (da_ft).
The fault detection unit 30 outputs a fault signal (da_ft) including a short-circuit fault signal (sh_ft) and/or an open-circuit fault signal (op_ft). The fault signal (da_ft) is output to the DATA input/output bus (DATA) through the second switch (SW 2, see fig. 4) of the DATA input/output control section 110 (see fig. 4) at the time of outputting the input/output control signal (da_io).
Fig. 10 is a diagram showing an outline of a control signal (s_sig) supplied to an LED backlight according to the present invention. Referring to fig. 10, a control signal (s_sig) is supplied to the LED backlight 1 to control the operation. In the illustrated embodiment, the LED backlight part performs a programming stage (DP) in which light emission data (da_out) is input to the data control part 10, a failure output stage (FP) in which the failure detection part 30 outputs a failure report (da_ft), and a light emission stage (EP) in which the light emitting device 40 emits light. The LED backlight may periodically repeatedly perform a programming phase (DP), a fault output phase (FP), and a light Emitting Phase (EP). In addition, the programming phase (DP) and the programming phase (DP) which rapidly executes the fail output phase (FP) and causes the light Emitting Phase (EP) to be executed for a long time can make the clock period in the light Emitting Phase (EP) larger than the fail output phase (FP).
Fig. 11 is a diagram of an LED backlight 1 configured in an active matrix form according to the present invention. Referring to fig. 11, a plurality of backlight units 1 may be arranged in rows and columns. As an example, the same control signal (s_sig1) is supplied to the backlight 1 arranged in the 1 st row, and the same control signal (s_sig2) is supplied to the backlight 1 arranged in the same row as the backlight 1 arranged in the 2 nd row.
In addition, the first DATA signal (DATA 1) is supplied to the backlight 1 arranged in the first column, and the same DATA signal is supplied to the backlight 1 arranged in the same column as the second DATA signal (DATA 2) is supplied to the backlight 1 arranged in the second column.
The backlight configured in this way can start the program phase (DP) and the fail output phase (FP) of the second row after the program phase (DP) and the fail output phase (FP) of the first row are finished. That is, the program phase (DP) and the fail output phase (FP) of the next driving row after the end of the program phase (DP) and the fail output phase (FP) of the previously driven row may be performed.
While the invention has been described with reference to the embodiments shown in the drawings for the purpose of aiding in the understanding of the same, it is to be understood that the embodiments are for the purpose of illustration and that various modifications and other embodiments may be made as will be understood by those of ordinary skill in the art. Accordingly, the true technical scope of the present invention should be determined by the appended claims.

Claims (14)

1. An LED backlight unit, comprising:
a light emitting device;
a data control unit that receives input control signals for embedding the light emission data, the clock signal, and the activation signal at different levels, and then outputs a luminance control signal for controlling luminance and a light emission time control signal for controlling luminance time;
a light emission control section that receives the inputted luminance control signal and light emission time control signal and drives the light emitting device to emit light with a luminance corresponding to the luminance control signal for a light emission time corresponding to the light emission time control signal; and
a failure detection section that detects a voltage at a node connected to the light emission control section and the light emitting device and outputs a failure signal corresponding to whether the light emitting device fails,
wherein the data control unit outputs the fault detected by the fault detection unit as a fault detection signal,
the failure detection unit includes:
a first comparator that outputs a short-circuit fault signal corresponding to whether or not a short-circuit fault has occurred by comparing a voltage at a node to which the light-emitting control section and the light-emitting device are connected with a short-circuit voltage;
a second comparator that outputs an open-circuit fault signal corresponding to whether or not an open-circuit fault has occurred by comparing a voltage at a node to which the light-emitting control section and the light-emitting device are connected with an open-circuit voltage;
a first latch for latching the short-circuit fault signal;
a second latch for latching the open circuit fault signal;
the first trigger samples and outputs the latched short-circuit fault signal as a short-circuit fault passing signal;
the second trigger samples and outputs the latched open-circuit fault signal as an open-circuit fault passing signal; and
a switch that is turned on to output the short-circuit fault signal or the open-circuit fault signal after the short-circuit fault pass signal or the open-circuit fault pass signal;
wherein the short-circuit fault signal and/or the open-circuit fault signal is provided as the fault signal to a data control section.
2. The LED backlight of claim 1, wherein the LED backlight is configured to display the display image,
the data control unit includes:
a signal separation section to which the control signal is input, and which separates and outputs the clock signal and the activation signal from the control signal, respectively;
a data input/output control section which is controlled according to an input/output control signal and receives the provided light emission data or outputs the failure signal to the outside; and
and a data processing section that supplies the control signal to and from the input/output section, receives the supplied activation signal, the clock signal, and the yes data, and forms and outputs the luminance control signal and the light emission time control signal.
3. The LED backlight of claim 2, wherein,
the control signal is embedded with:
the activation signal swinging between a first level that is a ground voltage level and a second level that is greater than the first level; and
the clock signal comprising a plurality of pulses swinging between the second level and a third level greater than the second level,
wherein the signal separation section includes: an activation signal isolation circuit that separates an activation signal by including a transistor having a threshold voltage between the first level and the second level, and outputs the separated activation signal to swing between the first level and the third level; a clock signal separation circuit that separates a clock signal by including a transistor having a threshold voltage between the second level and the third level, and outputs the separated clock signal to swing between the first level and the third level.
4. The LED backlight of claim 2, wherein,
the data input/output control section includes:
a first switch that receives the input light-emitting data from the input/output bus or outputs the fault detection signal to the input/output bus by being connected to the input/output bus, and is turned on when the input/output control signal is in a first state after being connected to the input/output bus to transmit the light-emitting data; and
and a second switch which is turned on when an input/output control signal is in a second state complementary to the first state after being connected to the input/output bus to connect the fault detection signal to the input/output bus.
5. The LED backlight of claim 2, wherein,
the data processing section includes an internal control signal forming section, wherein the internal control signal forming section includes:
a first SR latch to which the activation signal is input;
a first counter that counts the number of pulses included in the clock signal after being activated as an output signal of the first SR latch; and
an internal control signal forming section including a first operation section that forms and outputs a short-circuit fault passing signal and an open-circuit fault passing signal when a count result of the first counter is supplied and the count result is greater than a bit number of light emission data, and during a period of the short-circuit fault passing signal and the open-circuit fault passing signal, the data input/output control section forms and outputs an input/output control signal to cause the fault signal to be output to the outside, and after outputting the short-circuit fault passing signal and the open-circuit fault passing signal, outputs an internal control signal forming section stop signal,
wherein the internal control signal forming portion stop signal is provided to the first SR latch to deactivate the first counter.
6. The LED backlight as claimed in claim 5, wherein,
the light emitting data is serial data,
the data processing section includes: a brightness control signal forming section including a shift register which receives the inputted light emission data and forms each bit in parallel and then outputs the same, and a register which outputs each bit of the light emission data outputted from the shift register according to the internal control signal forming section stop signal,
wherein the output signal of the register is a brightness control signal.
7. The LED backlight as claimed in claim 5, wherein,
the data processing section includes a light emission time control signal forming section, wherein the light emission time control signal forming section includes: a second SR latch inputted with the internal control signal to form a stop signal;
a second counter that counts the number of pulses included in the clock signal after being activated to an output signal of the SR latch; and
a second operation section which is supplied with a count result of the second counter and a luminance control signal, and which forms and outputs a light emission time control signal of which pulse width is changed in accordance with a value of the luminance control signal, and after outputting the light emission time control signal, forms and outputs a stop signal of a light emission control signal forming section,
wherein the light emission control signal forming section stop signal is supplied to the second SR latch to deactivate the second counter.
8. The LED backlight of claim 7, wherein the LED backlight is configured to display the display image,
the second operation section forms the same pulse width as the light emission time control signal when the luminance control signal is greater than or equal to the threshold value, and forms the pulse width of the light emission time control signal to be proportional to the value of the luminance control signal when the luminance control signal is less than the threshold value.
9. The LED backlight of claim 1, wherein the LED backlight is configured to display the display image,
the light emission control unit includes:
a string resistor connected between the upper limit voltage and the lower limit voltage, and including a plurality of resistors outputting a plurality of voltages by distributing a voltage difference between the upper limit voltage and the lower limit voltage;
a digital-to-analog converter receiving the brightness control signal and outputting a gray-scale voltage corresponding to the brightness control signal among the plurality of voltages to emit light having a corresponding brightness;
a driving circuit section that receives the grayscale voltage and drives the light emitting device at a luminance corresponding to the grayscale voltage; and
a driving time control section that receives the supplied light emission time control signal, and the driving circuit section controls the light emitting device so that the light emitting device emits light for a time corresponding to a pulse width of the light emission time control signal.
10. The LED backlight of claim 1, wherein the LED backlight is configured to display the display image,
the failure detection section outputs any one or more of a short-circuit failure signal of the detected short-circuit failure of the light emitting device and a short-circuit failure signal of the detected short-circuit failure,
and the fault detection section outputs the short-circuit fault signal and the open-circuit fault signal according to the short-circuit fault passing signal, the open-circuit fault passing signal and the output short-circuit provided by the data control section.
11. The LED backlight of claim 1, wherein the LED backlight is configured to display the display image,
a programming stage of periodically performing the light emission data input to the data control part;
a fault output stage in which the fault detection unit outputs a fault signal; and
and a light emitting stage in which the light emitting device emits light.
12. The LED backlight of claim 11, wherein,
in the light emitting phase, the clock period has a larger value than the clock periods of the program phase and the fail output phase.
13. The LED backlight of claim 1, wherein the LED backlight is configured to display the display image,
configured in a plurality of rows and columns and driven by an active matrix.
14. The LED backlight of claim 13, wherein,
the same control signal is supplied to the LED backlights arranged in the plurality of rows, and the same light emission data is supplied to the LED backlights arranged in the plurality of columns.
CN202180001289.7A 2020-04-09 2021-03-29 LED backlight capable of detecting faults Active CN113785351B (en)

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