TW201220281A - including a short-circuit protection detection module, an image processor, a driving controller and a light adjusting control circuit - Google Patents

Abstract

A display backlight device for automatically compensating brightness when LED light strings are short-circuit protected is disclosed. The device includes a short-circuit protection detection module. The short-circuit protection detection module is electrically connected among a light source control module and LED light strings to output, based on feedback signals from each LED light string, to a general purpose I/O (GPIO) port of an image processor. When any of the LED light string is short-circuited and is protected by a driving controller, the image processor signals a light adjusting control circuit to output a continuous high level light adjusting signal to the driving controller to compensate average brightness of the entire LED light strings.

Description

201220281 SUMMARY OF THE INVENTION [Technical Field] The present invention relates to a backlight device and a control method therefor, and more particularly to a backlight device and a control method for automatically compensating for brightness when an LED lamp string is short-circuit protected. [Prior Art] Since the LED lamp has a higher luminous efficiency than the cold cathode (CCFL) lamp, the smaller the volume, the existing liquid crystal display products have gradually replaced the backlight of the cold cathode tube lamp with the LED lamp. Device. Referring to FIG. 1 , the conventional display backlight device 900 includes a light source control module 8 , a driving module 5 , and a light source module 7 (ie, an LED tube) having a plurality of LED light strings (not shown). The output ends 701, 702' ... 70 of the LED strings of the light source module 7 output a feedback signal to the driving module 5. The current protection device for the backlight device 900 for short-circuiting the LED light string is a short circuit of the LED light-emitting diode of the LED light string in the light source module 7, and the short-circuit LED light-emitting diode of the light string The voltage is increased to the corresponding feedback pin of the drive controller in the drive circuit 5. The drive controller of the drive module 5 has a set value for the number of short circuits, and when the number of short circuits reaches the set value, the LED is generated. The set of LED strings shorted by the lamp will be turned off' while the other LED strings that have not shorted the LED are still operating normally. The output of the set of LED strings that are short-circuited is opened, so that the average brightness of the LCD screen is displayed. Reduce and darken the face. In addition, in the user usage mode, the dimming signal output terminal 302 of the light source control module 8 gives the pulse mode duty ratio of the burst mode 201220281 (Burst-mode) of the dimming signal of the driving module 5 (Burst_m〇de Mark_Space) R ati ο ) ' is the ratio of the time occupied by the pulse to the total cycle time in a working cycle, only about 80%, so the maximum brightness is not reached, that is, the design usually leaves a margin. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a backlight device and a control method for automatically compensating for brightness when an LED light string is short-circuit protected. Therefore, the display light-emitting device for automatically compensating the brightness when the LED light string of the present invention is short-circuit protected includes a light source control module, a driving module and a plurality of LED light strings, and the LED light strings are driven by the driving module. Bright, the driving module retrieves the feed signal from the output end of the LED light string to determine whether each LED string has a short circuit of the light emitting diode, and the feedback voltage reaches the internal setting value of the feedback pin of the driving controller. The LED light string is protected; the invention is characterized in that the display backlight device further comprises a short circuit protection detecting module. The short circuit protection detecting module is electrically connected between the light source control module and the LED light strings, receives the feedback signals of the LED light strings, and outputs a detection signal to the light source control module, when the feedback is The signal indicates that when there is no short-circuit protection of the rib light string, the detection signal is - the first position is the detection signal is low level or is the same as the dimming frequency of the burst mode pulse square wave, and When the LED string is short-circuited, the detection signal is a second level, that is, the detection signal is continuously high. The light source control module has a dimming control circuit electrically connected to the dimming signal input pin of the driving controller in the driving module for controlling the average brightness of the LED tube and an image processor, and electrically connecting the Short circuit protection detection module and 201220281 The dimming control circuit 'When the image processor receives the debt measurement signal outputted by the output of the short circuit protection detection side module as the second level, the image processor issues a command for dimming The control circuit outputs a 100% dimming signal (ie, a high level = dimming signal) to the drive controller to compensate for the average brightness of the overall LED tube. The invention relates to a control method of a backlight device, a light source control module, a driving module, a short circuit protection detecting module and a plurality of LED light strings. The LED light strings are driven and lit by the driving module, and the short circuit The protection detection side module obtains a feedback signal from the LED light strings to determine whether there is a short circuit of the LED light string LED and is protected by the drive controller. The method includes the following steps: (a) providing a short circuit protection detecting module, the short circuit protection detecting module receiving the feedback signal of the LED light string and outputting

A detection signal is sent to the light source control module, and when the feedback signal indicates that the lED string is not short-circuit protected, the detection signal is a first level, that is, the detection signal is low level or is related to the dimming frequency. The same burst mode pulse square wave, and when any LED string is short-circuit protected, the detection signal is a second level, that is, the detection signal is continuous high level; and (b) the light source When the control module determines that the detection signal is at the second level, the image processor issues a command for the dimming control circuit to output a -100% dimming signal (ie, a high level dimming signal) to the drive controller. The invention overcomes the existing technical solution, and increases the short circuit protection detection module in the display backlight device to obtain the voltage of the output end of each LED light string and outputs a detection signal, and the light source control module determines the detection signal as When the current level is longer than the predetermined time tm (between 201220281 when the image processor's internal software setting is judged), there is a certain light string that is short-circuit protected, so that the brightness of the entire liquid crystal display screen becomes dark, and the image processor emits - instructing the dimming control circuit to output a 100% dimming signal (ie, a dimming signal that continues to be high) to the drive controller 'to compensate for the average brightness of the overall LED tube, such that the display backlight is Brightness is more suitable for users to watch. The above and other technical contents, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments. Referring to FIG. 2, in a preferred implementation of the present invention, the display backlight unit 1 includes a light source control module 1, a driving module 9, an LED tube 7 and a short circuit protection detecting module 3 » LED tube 7 is driven to be driven by the driving module 9, and the driving module 9 obtains the feedback signal from the LED strings 7i, 72...7n of the UD lamp 7 so that the current of each LED string during normal operation is constant current and judges led Whether each LED string 71'72...7n of the lamp tube 7 has a short circuit of the LED; as shown in Fig. 3, the driving module 9 has a driving controller 94, if a LED string (such as: LED string 71) When there is a short circuit in the light emitting diode, and the voltage of the feedback pin end of the driving controller 94 corresponding to the light string (for example, the feedback pin 9451) reaches the set short circuit protection voltage value inside the driving controller 94, The LED string is protected by a drive controller 94. / Referring to FIG. 2, the short circuit protection detecting module 3 is electrically connected to the output terminals of the light source control module 1 and the LED lamp tube 7 and the output terminals of the 72._.7n, and receives the LED lights. The feedback end of the string 71, 72...7η is 7〇2.,.7〇/201220281

Retrieving the nickname and outputting a detection signal through the short-circuit protection detection output terminal 301 of the short-circuit protection detection module 3 to the light source control module 1, when the respective input ends of the short-circuit protection detection module 3 (ie, the LED string 71) , 72~7n output terminal 7〇1, 702 7〇n) The detected feedback signal indicates that there is no LED string 未, and the short-circuit protection of the LED in 72...7η is short-circuit protected. The detection signal outputted by the detection output terminal 301 is a first level, that is, the detection signal is low level or a burst mode pulse square wave with the same dimming frequency, and the LED has any LED string. When the lamp is short-circuit protected, the detection signal outputted by the short-circuit protection detection output terminal 301 is a second level, that is, the detection signal is continuously high. The control method of the backlight device 100 for display according to the present invention includes the following steps: First, electrically connecting the short-circuit protection bias between the light source control mode of the display backlight device 100, the LED lamp string 71, 72, "7η Module short circuit protection _ module 3 receives the feedback signal of the LED 7 string 72., the output end 7 702...70n, and the short circuit protection detection output through the short circuit protection detection module 3# 3〇1 output a detection signal to the input terminals of the light source control module Budang New Road protection detection module 3 (ie, the output end of the LED light string 71, 72...7〇 7 () 7 () 2...7()11) The feedback signal to _ indicates that the LED string 7 that is not in any position is 72. When the 7.7.7n is short-circuit protected, the (4) signal output from the 3Q1 of the short-circuit protection detection wheel is output. The pulse-square wave of the burst mode of the first-order condition number is low level or the same as the dimming frequency, and the LED lamp with any LED string is short-circuit protected and protects the detection wheel output terminal 3Q1 The output detection signal is - the second level signal is continuous high level. #Light source control module 1 judge short circuit protection (4) test ^ 201220281 The output signal outputted by the output terminal 301 is the second level, the dimming signal output end 302 of the light source control module i outputs a 100% dimming signal (ie, continuous A high level dimming signal is given to the drive module 9. It should be noted that the dimming control circuit 12 controls the wavelength width duty ratio of the dimming signal of the burst mode of the driving controller 94 of the driving module 9 as long as the wavelength width of all the LED strings is not short-circuit protected. The air ratio is within the scope of protection of the present invention and is not limited to 1%. Referring to Fig. 3, the components and operational principles of the preferred embodiment of the backlight device for display of the present invention will be described in detail below. The light source control module 1 has an image processor 1〇, the aforementioned switch control circuit 11 and the aforementioned dimming control circuit d. The dynamic module 9 has a boosting circuit 91, an output chopper circuit 92, and an overvoltage protection. The detecting circuit 93, an overcurrent protection detecting circuit 95 and the driving controller 94; the LED tube 7 has a plurality of LED strings 7 72... 7n. In the driving module 9, the boosting circuit 91, the wheeling chopper circuit Μ, the overvoltage protection (four) measuring circuit 93, and the overcurrent protection detecting circuit 95 are prior art and are not heavy in the present invention. It is noted that the partial associated pin functions of the drive controller 94 associated with the present invention are described below. The dimming pin 942 outputs a burst mode (^ti〇de) dimming signal from the dimming signal output terminal 3()2 of the dimming control circuit 12 of the light source control module 1, thereby adjusting the LED string. 7 Bu 72.·.7η average brightness. The switch pin 941 is a switch signal output from the switch signal output terminal 303 of a switch control circuit 11 of 弁j: original ^ 、, control mode, and 1 To control whether the drive controller 94 is going to be away from you + 0 corps to operate or stop running 201220281 (ΟΝ / OFF). The pulse width output pin 943 is an output pulse width control signal control boost circuit 91, and the boost circuit 91 is a DC-DC boost type (^^ Boost). The overvoltage protection pin 944 detects whether the output voltage of the output wave circuit 92 exceeds a preset value by the overvoltage protection detecting circuit 93. When the output voltage of the output filter circuit 92 exceeds a preset value, the drive control The 94 will control the output voltage to remain the same or stop functioning. The overcurrent protection pin 946 detects whether the current maximum between the drain and the source of the switch MOS transistor inside the booster circuit 91 exceeds a preset value by the overcurrent protection detecting circuit 95. When the booster circuit 91 is internally The current value between the drain and the source of the switch M〇s tube exceeds the preset value, and the drive controller 94 controls the pulse width output pin 9 4 3 output PWM duty cycle is unchanged or the output PWM is stopped. The square wave is applied to the boosting circuit μ. The feedback pin group 945 is a feedback signal for receiving the feedback terminals 701'702...70n. One of the functions of the feedback pins 9451, 9452...945n is to detect the LED light strings 71, 72... Is there a short circuit of the light-emitting diode in 7η, and the short-circuiting of the light-emitting diodes of a certain LED light string 71, 72...7n reaches the preset value of the drive controller 94, and the light-emitting diode is short-circuited An LED light_, such as the LED light string 71, will be turned off, and other LED light strings that have not been short-circuited and are not protected, such as the LED light string 72...7n, operate normally, and the LED light string 71 that generates the new line protection The transistor whose output is connected to the drive controller 94 corresponding to the feedback pin 9451 is turned off. Closed, so that the current of the [rib lamp string cannot pass through the internal controller 201220281 of the drive controller 94 of the feedback pin 9451. The image processor ίο has a switch signal output pin 1〇, a dimming signal output pin 102 and a detecting pin 103, and the switch pin 101 is electrically connected to the switch control circuit 11 'switch control circuit 丨丨The switch signal output pin 101 of the image processor i 调控 is controlled to generate a control command for controlling the switch or not to the switch signal input pin 941 of the drive controller 94; the dimming control circuit 12 is electrically connected and received The dimming signal output pin 102 of the processor 1 is controlled to generate a control command for controlling the duty ratio of the pulse square wave of the burst mode to the dimming signal input pin 942 of the drive controller 94. The short circuit protection detecting module 3 includes the number and the like

7n the same number of diodes DU".Dtn, a voltage regulator diode z])i, a capacitor c a first resistor R1 and a second resistor R2, the anode of each diode "b ^ With the output terminals 701, 702 of each LED lamp _ 71...7n 70 η, j

Connected, the negative pole of each diode DU...Dtn is negative with the Zener diode ZD1; j is connected to the anode of the Zener diode ZD1 and one end of the first resistor R1 as =, the first resistor R1 The other end is connected to the detecting pin 103 of the image processor and the capacitor end of the second resistor R2, and the pin (10) j is a general-purpose input/output pin of the image processor 10 (ie, GPK), and is processed by the software. The input 做 as a detection signal can also be written as a pull-out by software, and the other end of the second resistor R2 and the other end of the capacitor 为 are grounded. β Refer to FIG. 3 and FIG. 4 'The image processor 10 first determines whether the detection pin 10 detects a continuous high level card β electric ten time is greater than a predetermined time Μ step learning. Right 疋 'image processor 10, the dimming control circuit 12 rotates 100, dimming signal to the drive controller 94 (steps; if not, the image processing agency

S 10 201220281 The output light control circuit 12 outputs the original dimming signal to the drive controller 94 (step 403). It should be noted that the predetermined time tn needs to be set to be greater than (four) τ of the dimming signal of the burst mode. Such as: predetermined time t-= 2T, 3 Τ, etc., detailed control description is as follows. Referring to FIG. 3, and in conjunction with FIG. 5, in the time interval ti, the dimming signal output terminal 302 of the dimming control circuit 12 outputs a high-level dimming signal, so that the pulse width output pin 943 of the driving controller 94 outputs pwM. The pulse square wave gives the boosting circuit 91 to start normal operation and supply energy to the output filter circuit 92, while the drive controller 94 feeds back the pins 9451, 9452~945n corresponding to the internal controller of the drive controller to be turned on so that the LED string 71 The ED string 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 71 The outputs of 72, 7n are sequentially connected to respective corresponding feedback pins 9451, 9452, ... 945n of the drive controller 94. When the driving module 9 is working normally, the feedback pins 9451, 9452, ... 945n of the driving controller 94 have a function of making the operating current of each LED tube constant current and the LED string short-circuit protection function, and the driving module 9 works normally. At the same time, almost all of the output filter circuit 92 output voltage drops in each of the LED strings 71, 72...7n, and the feedback pins 9451, 9452...945n of the drive controller 94 only produce a lower feedback voltage vfbl. About 2V or less 'When there is a LED light string, such as LED light string 71, there are m light-emitting diodes short-circuited but have not reached the drive controller 94 feedback and the internal preset short-circuit protection voltage value, and adjust When the dimming signal output terminal 302 of the light control circuit 12 outputs a high level signal, all the LED light strings 71, 72...7n are still 11 201220281 and all work normally 'because the feedback pin 945 b 9452 · .945 η has the (10) lamp String 7 Bu 72... 7η works as a constant current characteristic, so the voltage on the feedback pin 9451 corresponding to the string 71 of which the m light-emitting diodes are short-circuited will increase to VfbI' = Vibl+m* Vfl, wherein each parameter is described as follows: V...: LED When the string is in normal operation and the light string does not have any light-emitting diode short-circuited, the output terminal of the LED string 71 is electrically M, and the voltage is about 2V; the drive controller allows short-circuiting of the LED string n, 72~7n The number, that is, the light string of the LED light-emitting diodes, the light string can still work normally; when the light string is short-circuited m+ΙLED light-emitting diodes, the light string is protected from working, for example. MP3389 drive controller m=1, model TA969〇 drive controller m=2;

Vfi · When the LED lamp is working normally, the LED light string 71, 72...7n normally operates with a light-emitting diode forward voltage, generally between 3V and 3 3V. When a certain LED string, such as the light string 71, has m+i light-emitting diodes generating a link and reaches a preset protection voltage value corresponding to the internal feedback pin 9451 of the drive controller 94, the string 71 is Short-circuit protection, at this time, other light strings that have not been short-circuit protected still work normally, for example, the feedback pins 9452...945n of the drive controller 94 corresponding to the LED light strings 72...7n in which no light-emitting diode is short-circuited are still Vfbi; the short-circuited LED string 71 is protected by the drive controller 94, at which time the LED string 71 corresponds to the transistor inside the feedback pin 9451 being turned off 'so that the LED string 71 current cannot pass the corresponding feedback connection The foot 9451 stops working. The remaining unshort-circuited LED of the short-circuit protected LED string also has a critical collapse forward voltage of about 20120281 of about Vf2=2V~2 4V, and the short-circuit protected A lamp _ η output will have a higher voltage, the voltage value is about: Vfb "= v ^u (X- ( m + l )) = 33V-2_ 2V * (10_2) = 15. 4V, each parameter Explain as follows f2: X: the number of all series of LEDs in each LED string 7 72...h, such as :X=10 ;

Vin : LED lamp 7 input voltage, such as:; m+1: short circuit protection, the number of short-circuited LEDs, such as: MP3389 model of the drive controller m = 1;

When the LED string 7 is 72...711 is not in use, there is still a critical crash. The forward conduction voltage is as follows: Vf2 = 2. 2V. In the preferred embodiment, the voltage regulation value can be selected to be slightly larger than the feedback voltage of the drive controller 94 corresponding to the feedback pin 945, 9452... 945n internal preset voltage protection voltage vset voltage (eg, drive controller model MP3389: v... The purpose of the Zener diode ZD1' is to: 1. When the time interval tl, that is, the LED lights _71, 72... "normal operation is not short-circuited, ZD1 is not conducting, at this time, the short-circuit protection output terminal 3 〇1 knows that the output is low (four) test signal, and the detection pin 103 of the image processor ig can receive a low level voltage. 2. When in the time interval t2, the time interval tn, or the time interval ^, when the string of lights 71, 72...7n does not work or the LED string 71 is short-circuit protected, then: pass, set the first resistor R1 and the second resistor _ resistance ratio to confirm the loop protection detection output The terminal 301 can output a high-level debt measurement signal, and the detection pin 1〇3 of the image processor 10 can receive the dimming signal of the dimming control circuit 12 when the high-precision 13 201220281 time interval h is received. The output terminal 3〇2 outputs a low-level dimming signal, so that the LED string 71, 72.·· 7n are simultaneously The cutoff does not light up; since the LED light strings 71, 72...7n still have a critical collapse voltage at the time of the cutoff, and at this time, the forward voltage of each of the LED light strings 71, 72...7n is critically collapsed. Vf2 is about 2.0V~2.4V. Therefore, the voltage of the output terminals 701, 702...70n of the LED string 71, 72...7n is Vfb2=Vin-Vf2*X is a higher voltage 'X is the LED string 7 72... 7n series number of light-emitting diodes, if Vin=33v; Vf2=2. 2ν ; χ=1〇;

Vfb2=11, at this time, the short circuit protection detection output terminal 301 outputs a detection signal of a high level, and the detection pin 3 of the image processor 1 接收 receives a high level voltage. The detection pin 103 of the preferred embodiment uses a general purpose input/output (GPIO) control pin, and the detection signal detected by the image processor 103 is designed as a standard The voltage of T11, that is, the voltage detected by the GPIO control pin is 〇. 8V is interpreted as low voltage, and the voltage detected by GPI0 control pin is high voltage when 2V. The image processor 10 determines that the detection signal received by the detection pin 103 from the short circuit protection detection output terminal 301 continues to be a high level voltage for more than a predetermined time t»', so that the dimming control circuit 12 continuously outputs 1%%. The dimming signal is given to the drive controller 94, so that the image processor 1〇 can be programmed to realize that when an LED string, such as the LED string 71, is short-circuit protected, the program instantly detects and will make the image The output terminal 〇2 of the processor 10 outputs a constant signal to the dimming control circuit 12, so that the dimming signal output terminal 302 of the dimming control circuit 12 outputs a dimming signal of a continuous high level to the driver 14 201220281 The dimming input pin 942 of the controller 94 causes other unprotected LED light strings, such as LED light strings 72...7n, to increase in brightness, thereby compensating for a certain light string in the led lamp 7 to be short-circuit protected. The overall average brightness of the subsequent LED tube 7 makes the brightness of the display backlight more suitable for the user to view. In summary, the present invention overcomes the existing technical solution, and adds the short circuit protection detecting module 3 to the display light-emitting device 100 to instantly detect the LED light strings 71, 72...7n output end 701 '702.. 70 η voltage, and the detection signal is transmitted to the light source control module through the short-circuit protection detection output terminal 301, and the light source control module 1 determines whether the detection signal output by the short-circuit protection detection output terminal 3〇1 is the second The level, that is, whether the detection signal is a question level whose duration is longer than 惫疋, the image processor causes the dimming control circuit a to output a loo% dimming signal to the drive controller 94 to compensate for the overall The average brightness of the Ld lamp 7 makes the brightness of the backlight device 1 更 more suitable for the user to view, so that the object of the present invention can be achieved. The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the patent and the description of the invention in the present invention are All remain within the scope of the invention patent. [Simple description of the map]

1 is a circuit block diagram illustrating the control mode of a conventional backlight device for display; FIG. 2 is a circuit block diagram illustrating a backlight device for display of the present invention and a control method thereof; 〃 15 201220281 FIG. 3 is a circuit block diagram DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 4 is a flow chart illustrating a program processing step; and FIG. 5 is a timing chart illustrating a partial output chirp waveform of the display backlight device of the present invention.

S 16 201220281 [Description of main component symbols] [General] 302 • · •• Dimming signal wheel output 5... Drive module 303 ----Switch signal wheel output ·*·*· · Light source module 7 .. • • • Light source module 8... Light source control module 71, 72...7n LED light string 701, 702...70η—— 701- 70n LED string output LED light string output terminal 9 .. ----Drive module 302 ---- Dimming signal output terminal 91 · - Boost circuit 303 - Switch signal output terminal 92 · • • • Output filter circuit 900 · ··· Display backlight unit 93 • •• Overvoltage protection circuit [This creation] 94 · ----Drive controller 100 - Display backlight 95 · • · · · Overcurrent protection detection 1 ······ Light source control module road 10... Image processor 941 ----Switch pin 101 - Switch pin 942 ---- Dimming pin 102---- Dimming pin 943 • Pulse width output pin 103 - Detection pin 944 ---- Overvoltage protection pin 11... Switch control circuit 9451, 9452...945η---back 12... .. dimming control circuit feed Pin 3... Short circuit protection detection mode 946 ---- Over current protection pin group C1 · ---- Capacitor 401-403 Step Dtl. ·· Dtn---Diode 301 Short circuit protection detection R1 · - first resistance output R2 · • · · · second resistance 17 201220281 ZDl - voltage regulator diode

S. 18

Claims (1)

201220281 VII. Patent application scope: 1_ A backlight device for display that automatically compensates for brightness when the LED light string is short-circuit protected, including a light source control module, - 犯 smashing module and several LED light strings, the 4 LED lights The string is driven by the driving module, and the driving module obtains a feedback signal from the LED strings to determine whether a light-emitting diode of the LED light rate is short-circuited, so that the string is short-circuit protected; The display backlight device further includes: a short circuit protection detecting module electrically connected to the light source control module and the beta LED string to receive a feedback signal of the LED string and output a detection signal to The light source control module, when the feedback signal indicates that no LED string is short-circuit protected, the detection signal is at a first level, and the detection signal is when the LED string is short-circuit protected. a second level; and the light source control module has: a dimming control circuit electrically connecting and controlling the wavelength width period of the wavelength sfL of the dimming mode of the burst mode of the driving module; And a picture The processor is electrically connected to the short circuit protection detecting module and the dimming control circuit, and when the detecting signal is determined to be the second level, the dimming control circuit controls the dimming mode of the driving module. The signal's wave width duty cycle is greater than the wave width duty cycle when all LED strings are not short-circuit protected. 2. The display backlight device for automatically compensating for brightness when the LED string of the first embodiment of the patent application scope is protected by short circuit protection, wherein the image processor internal software program determines that the detection signal continues to be the second The leveling time exceeds a predetermined time, that is, the dimming control circuit continuously outputs the dimming signal 19 201220281 which controls the brightness adjustment to the driving controller. 3. The display backlight device for automatically compensating for brightness when the LED light string of the second application of the patent application is short-circuit protected, wherein the image processor has an electrical connection to the short-circuit protection detection module to receive the detection The detection pin of the test signal and a dimming pin electrically connected to the dimming control circuit. 4. The display backlight device for automatically compensating for brightness when the LED light string according to item 3 of the patent application scope is short-circuit protected, wherein the short circuit protection detecting module includes the same number of the same as the LED light string a pole body, a voltage stabilizing diode, a capacitor, a first resistor and a second resistor, wherein the anode of each of the diodes is electrically connected to the output end of each of the LED strings, and the anode of each of the diodes Connected to the negative pole of the voltage stabilizing diode, the positive pole of the voltage stabilizing diode is connected to one end of the first resistor, and the other end of the first resistor is connected to one end of the second resistor and one end of the capacitor The detecting pin is, and the other end of the second resistor and the other end of the capacitor are grounded. 5. A control method for a display backlight device, coupled with a light source control module, a driving module and a plurality of LED light strings, wherein the LED light strings are driven to be illuminated by the driving module, the driving module is Waiting for the LED string to obtain a feedback signal to determine whether there is a short circuit of the LED of the LED string so that the LED string is short-circuit protected; the method comprises the following steps: (a) providing a short-circuit protection The short circuit protection detection module receives the feedback signal of the LED light string and outputs a detection signal to the light source control module. When the feedback signal indicates that no LED light string is short-circuit protected, the test module The detection signal is a first level, and the detection signal is a second level when any LED string is short-circuit protected; and 201220281 (b) the light source control module determines the detection signal The wavelength width duty ratio of the dimming signal for controlling the burst mode of the driving module for the second bit is greater than the wave width duty ratio when the LED string is not short-circuit protected. According to the control method of the display backlight device described in claim 5, wherein in the step (b), the light source control module determines that the detection signal continues to be at the second level for more than a predetermined time. That is, the dimming control circuit continuously outputs a dimming signal for controlling the brightness adjustment to the driving controller. twenty one