CN205793505U - A kind of LED backlight circuit and liquid crystal TV set - Google Patents
A kind of LED backlight circuit and liquid crystal TV set Download PDFInfo
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- CN205793505U CN205793505U CN201620512146.9U CN201620512146U CN205793505U CN 205793505 U CN205793505 U CN 205793505U CN 201620512146 U CN201620512146 U CN 201620512146U CN 205793505 U CN205793505 U CN 205793505U
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Abstract
The utility model discloses a kind of LED backlight circuit and liquid crystal TV set, LED backlight circuit connects master chip, and LED backlight circuit includes several LED strings, several current-limiting resistances, DC DC transducer, PWM controller, several detection modules and control module；DC DC transducer connects each LED string and PWM controller；Each LED series winding connects PWM controller；Several detection modules connect a LED string respectively, and control module connects master chip and detection module；Supply voltage is converted into running voltage to each LED statements based on collusion electricity by DC DC transducer；Detection module detects short circuit or the open-circuit condition of corresponding LED string, and output triggers signal accordingly；Control module sends fault message according to the triggering corresponding interrupt signal of signal output to master chip and shows to screen.Thus solve the problem not having LED open circuit detection in existing television set, can not automatically detecting short circuit.
Description
Technical field
This utility model relates to Display Technique field, particularly to a kind of LED backlight circuit and liquid crystal TV set.
Background technology
At present, the liquid crystal TV set overwhelming majority on the market uses LED backlight, and LED backlight mainly has 2 kinds of modes: straight-down negative and side entering type.Wherein, side entering-type LED backlight source mostly uses a plurality of LED string actuation techniques, and does not mostly have LED failure detection and prompting function and LED open circuit protecting function.As it is shown in figure 1, existing LED backlight main circuit will be by dc-dc, PWM controller, n × m LED string (n goes here and there, often m LED of string, white light), n current-limiting resistance (R11 ~ R1n) composition；Its operation principle is as follows:
Dc-dc is dc voltage changer, and input voltage vin is generally 24 volts, and running voltage Vout is designed as high about the 1V of the forward voltage more total than LED string.Under normal circumstances, the forward voltage VF of LED is 3.2 ~ 3.4V, so Vout=m*VF+1, m are a number of LED in a LED string.Assume VF=3.3V, if all LED strings are all 10 LEDs, then Vout=10*3.3+1=34V.Voltage on current-limiting resistance is 34-33=1 volt.The operating current assuming LED string is 0.35A, then the power consumption of each current-limiting resistance is 0.35A*1V=0.35W, belongs to normal range.
Assume to have the LEDs in a LED string to be short-circuited fault, then the LED string of short circuit is equivalent to only 9 LEDs, and remaining normal LED string is respectively 10.Running voltage Vout is to be as the criterion with the maximum number of LED string, i.e. Vout keeps 34V.The forward voltage of the lamp string of short circuit is 9*3.3=29.7V, in the lamp string of short circuit, the voltage on current-limiting resistance is 34-29.7=4.3V, power consumption is 0.35A*4.3V=1.505W, more than being 4 times of normal value 0.35W, the lamp string not only inefficiency of short circuit, long-time use may also result in current-limiting resistance damage, causes more major break down.
Assume the LEDs generation open fault having in a LED string, then the voltage on the current-limiting resistance of the LED string of this open circuit is 0V, the FBO signal of PWM controller output controls dc-dc, output its value of maximum working voltage Vout_max(depends on circuit design, generally about 1.2 times of normal working voltage Vout), the most i.e. Vout_max=1.2*34V=40.8V.In this case, the voltage of the current-limiting resistance on normal LED string is 40.8-33=7.8V, and the power consumption of current-limiting resistance is 0.35A*7.8V=2.73W, about 8 times of normal value 0.35 watt.Outside except the lamp string on road, the work efficiency of remaining lamp string is extremely low, and long-time use is very harmful, it is seen then that the hazard ratio short circuit LED string that open circuit LED string causes is much bigger.
But, prior art seldom relates to short circuit, open circuit process.The such as patent of China's Application No. 201510156429.4 proposes a kind of LED light source method for detecting short circuit and device, and it can only detect LED short trouble, does not has LED open circuit detection and protection circuit；It addition, its detection method is extremely complex, detection process needs human intervention, it is impossible to realize detection automatically.
It is therefore desirable to prior art is improved.
Utility model content
In place of above-mentioned the deficiencies in the prior art, the purpose of this utility model is to provide a kind of LED backlight circuit and liquid crystal TV set, to solve in existing television set, and the problem that do not have LED open circuit detection, can not automatically detect short circuit.
In order to achieve the above object, this utility model takes techniques below scheme:
A kind of LED backlight circuit, it is connected with master chip, including several LED strings, several current-limiting resistances, for supply voltage is converted into running voltage to the dc-dc of each LED statements based on collusion electricity, be used for controlling each LED cross luma and go out the PWM controller of state, it also includes:
For detecting short circuit or the open-circuit condition of the LED string of correspondence, and export corresponding several detection modules triggering signal；
For according to triggering the signal corresponding interrupt signal of output to the control module of master chip；
Described dc-dc connects each LED string and PWM controller；Each LED series winding connects PWM controller, also by current-limiting resistance ground connection；Several detection modules connect a LED string respectively, and control module connects master chip and detection module.
In described LED backlight circuit, the number of described detection module, the number of LED string, the number of current-limiting resistance, PWM controller test side number the most identical；One LED string and detection module, a current-limiting resistance pairing；
The voltage output end of described dc-dc connects the positive pole of each LED string, and the feedback end of dc-dc connects the outfan of PWM controller；The negative pole of each LED string is connected one to one with each test side of PWM controller, and the negative pole of each LED string is also by the current-limiting resistance ground connection of pairing；The input of each detection module is connected with the positive pole of the LED string of pairing, and the test side of each detection module is connected with the negative pole of the LED string of pairing；The outfan of each detection module is all connected with the input of control module, and the outfan of control module connects master chip.
In described LED backlight circuit, described each detection module all includes a Zener diode, a resistance and a diode；The negative pole of Zener diode connects the positive pole of the LED string of pairing, the positive pole of Zener diode connects one end of resistance, the other end of resistance connects negative pole and one end of current-limiting resistance of the LED string of pairing, the other end of resistance is also connected with the test side that the positive pole of diode is corresponding with PWM controller, the input of the negative pole link control module of diode.
In described LED backlight circuit, the resistance of described resistance is 47 Ω ~ 200 Ω.
In described LED backlight circuit, described control module includes base resistance, pull-up resistor and audion；One end of described base resistance connects the negative pole of each diode, the base stage of the other end connecting triode of base resistance, the grounded emitter of audion, and the colelctor electrode of audion connects master chip and one end of pull-up resistor, and the other end of pull-up resistor connects power end.
In described LED backlight circuit, the resistance of described base resistance is 1K Ω ~ 4.7K Ω, and the resistance of pull-up resistor is 4.7K Ω ~ 10K Ω, and audion is NPN audion.
A kind of liquid crystal TV set, including master chip, it also includes described LED backlight circuit, the short circuit of described LED backlight electric circuit inspection LED string or open-circuit condition, when the short circuit of LED string or open circuit being detected, output interrupt signal is to master chip, and master chip sends fault message according to interrupt signal and shows to screen.
Compared to prior art, a kind of LED backlight circuit of this utility model offer and liquid crystal TV set, LED backlight circuit includes；LED backlight circuit connects master chip, and LED backlight circuit includes several LED strings, several current-limiting resistances, dc-dc, PWM controller, several detection modules and control module；Dc-dc connects each LED string and PWM controller；Each LED series winding connects PWM controller；Several detection modules connect a LED string respectively, and control module connects master chip and detection module；Supply voltage is converted into running voltage and controls each LED cross luma go out state to each LED statements based on collusion electricity, PWM controller by dc-dc；Detection module detects short circuit or the open-circuit condition of corresponding LED string, and output triggers signal accordingly；Control module sends fault message according to the triggering corresponding interrupt signal of signal output to master chip and shows to screen.Thus solve the problem not having LED open circuit detection in existing television set, can not automatically detecting short circuit；Its circuit structure is very simple, and cost is the lowest, is suitable for wideling popularize.
Accompanying drawing explanation
Fig. 1 is the circuit diagram of existing LED backlight circuit.
The circuit diagram of the LED backlight circuit that Fig. 2 provides for this utility model embodiment.
Detailed description of the invention
This utility model provides a kind of LED backlight circuit and liquid crystal TV set, has LED short circuit and open circuit detection, fault prompting function, and LED open circuit protecting function automatically, and its circuit structure is simple, cost is relatively low, and practicality is stronger.For making the purpose of this utility model, technical scheme and effect clearer, clear and definite, this utility model is further described by the embodiment that develops simultaneously referring to the drawings.Should be appreciated that specific embodiment described herein, only in order to explain this utility model, is not used to limit this utility model.
This utility model provides a kind of liquid crystal TV set, and it includes LED backlight circuit and master chip, and LED backlight main circuit chip connects.The short circuit of described LED backlight electric circuit inspection LED string or open-circuit condition, when the short circuit of LED string or open circuit being detected, output interrupt signal is to master chip, and master chip sends fault message according to interrupt signal and shows to screen.
As in figure 2 it is shown, described LED backlight circuit includes dc-dc 100, PWM controller 200, several LED strings (51 ~ 5n), several current-limiting resistances (R1 ~ Rn), several detection modules (31 ~ 3n) and control module 400.The number of described detection module, the number of LED string, the number of current-limiting resistance, PWM controller test side number the most identical；One LED string and detection module, a current-limiting resistance pairing.N is positive integer.
The voltage output end OUT of described dc-dc 100 connects the positive pole of each LED string, and the feedback end FB of dc-dc 100 connects the outfan FBO of PWM controller 200；The negative pole of each LED string is connected one to one with each test side (L1 ~ Ln) of PWM controller 200, and the negative pole of each LED string is also by the current-limiting resistance ground connection of pairing.The input of each detection module (31 ~ 3n) is connected with the positive pole of the LED string of pairing, the test side of each detection module (31 ~ 3n) is connected with the negative pole of the LED string of pairing, the outfan of each detection module (31 ~ 3n) is all connected with the input of control module 400, and the outfan of control module 400 connects the master chip of liquid crystal TV set.
Wherein, m LED of having connected in described LED string, m is positive integer.The positive pole of LED string refers to total positive pole, the positive pole of i.e. first LED (being topmost in Fig. 2)；The negative pole of LED string refers to be bottom in total negative pole, i.e. last LED(Fig. 2) negative pole.Described dc-dc 100, PWM controller 200, LED string, current-limiting resistance are prior art, and its annexation and operation principle are prior art.Supply voltage is converted into running voltage Vout and is used for controlling the light on and off state of each LED string to each LED statements based on collusion electricity, PWM controller 200 by dc-dc 100.
The improvement of the present embodiment is to increase several detection modules (31 ~ 3n) and a control module 400.The short circuit of the LED string that each detection module (31 ~ 3n) detection is matched with it or open-circuit condition, and export the triggering signal of correspondence.Control module 400 exports corresponding interrupt signal to master chip, to control master chip prompting user when short circuit or open circuit being detected according to triggering signal.
Particularly as follows: when the LED string short circuit that detection module (31 ~ 3n) detection is matched with it or open circuit, the triggering signal of output high level, the triggering signal of output low level when LED string is normal.Control module 400 is pointed out to master chip, master chip according to the interrupt signal triggering signal output low level of high level；If triggering signal is low level, then control module 400 exports the interrupt signal of high level, and master chip does not processes.
Please continue to refer to Fig. 2, in the present embodiment, the circuit structure of each detection module is identical, and each detection module includes a Zener diode, a resistance and a diode；The negative pole (i.e. the input of detection module) of Zener diode connects the positive pole of the LED string of pairing, the positive pole of Zener diode connects one end of resistance, the other end (i.e. the test side of detection module) of resistance connects negative pole and one end of current-limiting resistance of the LED string of pairing, the other end of resistance is also connected with the test side that the positive pole of diode is corresponding with PWM controller, the input of negative pole (i.e. the outfan of the detection module) link control module of diode.
Described each detection module is respectively first detection module the 31, second detection module 32 ..., the n-th detection module 3n.As a example by first detection module 31.Described first detection module 31 includes the first Zener diode Dz1, the first resistance Rw1 and the first diode D1；The negative pole (i.e. the input of first detection module) of described first Zener diode Dz1 connects the positive pole of the first LED string 51, the positive pole of the first Zener diode Dz1 connects one end of the first resistance Rw1, the other end (i.e. the test side of first detection module) of the first resistance Rw1 connects negative pole and one end of the first current-limiting resistance R1 of the first LED string 51, the other end ground connection of the first current-limiting resistance R1.The other end of the first resistance Rw1 is also connected with the input of negative pole (i.e. the outfan of the first detection module) link control module 400 of the positive pole of the first diode D1 and the first test side L1 of PWM controller 200, the first diode D1.
Described control module 400 includes base resistance R401, pull-up resistor R402 and audion Q；One end (i.e. the input of control module) of described base resistance R401 connects the negative pole (and negative pole of other diodes) of the first diode D1, the base stage of the other end connecting triode Q of base resistance R401, the grounded emitter of audion Q, the colelctor electrode of audion Q connects master chip and one end of pull-up resistor 402, and the other end of pull-up resistor 402 connects power end (input 3.3V power supply).
Wherein, described first Zener diode Dz1 and the first resistance Rw1 forms open loop protection circuit, the first current-limiting resistance R1 and the first diode D1 and forms short-circuit protection circuit.The resistance of base resistance R401 takes between 1K Ω ~ 4.7K Ω, and the resistance of pull-up resistor 402 takes between 4.7K Ω ~ 10K Ω, and the amplification of audion Q is between 50 ~ 200.
Under normal circumstances, audion Q is in cut-off state, and collector voltage i.e. interrupt signal INT of about 3.3V(is high level).When having short circuit or open fault occurs, audion Q conducting is the most saturated, interrupt signal INT is that 0V(is low level), interrupt signal INT is connected with the master chip of television set, interrupt signal INT is low level, reporting to the police to master chip, in screen ejection, " backlight of television breaks down master chip, reports for repairment the most in time！" etc fault message, in order to remind consumer report for repairment.
Please continue to refer to Fig. 2, it is assumed that each LED string all has 10 LEDs, the forward voltage VF=3.3V of LED string, running voltage Vout of dc-dc output is 34V under normal circumstances.The operation principle of described A is:
Short circuit detection automatically and prompting:
As a example by the first LED string 51, it is assumed that have a LED lamp to be short-circuited, then the forward voltage that the first LED string 51 is total is 9*3.3=29.7V, and the voltage on the first current-limiting resistance R1 is 34-29.7=4.3V.As can be seen from Figure 2, as long as having the voltage on a current-limiting resistance more than 2V, just can provide base current to audion Q by base resistance 401, audion Q conducting is the most saturated, interrupt signal INT of its colelctor electrode output becomes low level, thus control master chip and eject fault message at screen, remind consumer to report for repairment.
Open-circuit-protection also automatically detects and reminds:
The resistance of the first resistance Rw1 is 47 Ω ~ 200 Ω, and total forward voltage of the voltage stabilizing value of the first Zener diode Dz1 the first LED string 51 by being protected adds 3.3V, i.e. 10*3.3+3.3=36.3V.
Running voltage Vout is 34V under normal circumstances, less than voltage stabilizing value 36.3V, the first Zener diode Dz1 cut-off, does not affect circuit work.When there is LED open fault in the first LED string 51, without protection circuit, running voltage Vout can bring up to 40.8V(can refer to background technology).After having had protection circuit; when running voltage Vout, to bring up to 37.3 V more; first Zener diode Dz1 conducting; when voltage on first current-limiting resistance R1 is also initially increased to about 1V by 0V; running voltage Vout is maintained at 37.3V; less than 40.8V during unprotected circuit, circuit work is comparatively safe.The voltage of the current-limiting resistance on normal LED string is 37.3-33=4.3V, as can be seen from Figure 2, as long as having the voltage on a current-limiting resistance more than 2V, just can provide base current by base resistance R401 to audion Q, audion Q conducting is the most saturated, interrupt signal INT becomes low level, thus the master chip controlling television set ejects fault message at screen, reminds consumer to report for repairment.
In sum, the LED backlight circuit of this utility model offer and liquid crystal TV set, by increasing a control module, and increase a detection module to each LED string, by short circuit or the open-circuit condition of the LED string of detection module detection correspondence, and export the triggering signal of correspondence；Control module according to trigger signal export corresponding interrupt signal to master chip, with detect short circuit or open circuit time control master chip send out fault message prompting user；It is achieved thereby that LED short circuit and open circuit detection, fault prompting function, and LED open circuit protecting function automatically, its circuit structure is very simple, cost is relatively low, and practicality is stronger.
It is understandable that; for those of ordinary skills; in addition equivalent or change can be conceived according to the technical solution of the utility model and utility model thereof, and all these change or replace and all should belong to the scope of the claims appended by this utility model.
Claims (7)
1. a LED backlight circuit, it is connected with master chip, including several LED strings, several current-limiting resistances, for supply voltage is converted into running voltage to the dc-dc of each LED statements based on collusion electricity, be used for controlling each LED cross luma and go out the PWM controller of state, it is characterized in that, also include:
For detecting short circuit or the open-circuit condition of the LED string of correspondence, and export corresponding several detection modules triggering signal；
For according to triggering the signal corresponding interrupt signal of output to the control module of master chip；
Described dc-dc connects each LED string and PWM controller；Each LED series winding connects PWM controller, also by current-limiting resistance ground connection；Several detection modules connect a LED string respectively, and control module connects master chip and detection module.
LED backlight circuit the most according to claim 1, it is characterised in that the number of described detection module, the number of LED string, the number of current-limiting resistance, PWM controller test side number the most identical；One LED string and detection module, a current-limiting resistance pairing；
The voltage output end of described dc-dc connects the positive pole of each LED string, and the feedback end of dc-dc connects the outfan of PWM controller；The negative pole of each LED string is connected one to one with each test side of PWM controller, and the negative pole of each LED string is also by the current-limiting resistance ground connection of pairing；The input of each detection module is connected with the positive pole of the LED string of pairing, and the test side of each detection module is connected with the negative pole of the LED string of pairing；The outfan of each detection module is all connected with the input of control module, and the outfan of control module connects master chip.
LED backlight circuit the most according to claim 2, it is characterised in that described each detection module all includes a Zener diode, a resistance and a diode；The negative pole of Zener diode connects the positive pole of the LED string of pairing, the positive pole of Zener diode connects one end of resistance, the other end of resistance connects negative pole and one end of current-limiting resistance of the LED string of pairing, the other end of resistance is also connected with the test side that the positive pole of diode is corresponding with PWM controller, the input of the negative pole link control module of diode.
LED backlight circuit the most according to claim 3, it is characterised in that the resistance of described resistance is 47 Ω ~ 200 Ω.
LED backlight circuit the most according to claim 3, it is characterised in that described control module includes base resistance, pull-up resistor and audion；One end of described base resistance connects the negative pole of each diode, the base stage of the other end connecting triode of base resistance, the grounded emitter of audion, and the colelctor electrode of audion connects master chip and one end of pull-up resistor, and the other end of pull-up resistor connects power end.
LED backlight circuit the most according to claim 5, it is characterised in that the resistance of described base resistance is 1K Ω ~ 4.7K Ω, the resistance of pull-up resistor is 4.7K Ω ~ 10K Ω, and audion is NPN audion.
7. a liquid crystal TV set, including master chip, it is characterized in that, also include the LED backlight circuit as described in claim 1-6 is arbitrary, the short circuit of described LED backlight electric circuit inspection LED string or open-circuit condition, when the short circuit of LED string or open circuit being detected, output interrupt signal is to master chip, and master chip sends fault message according to interrupt signal and shows to screen.
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| CN201620512146.9U CN205793505U (en) | 2016-05-31 | 2016-05-31 | A kind of LED backlight circuit and liquid crystal TV set |
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| CN201620512146.9U CN205793505U (en) | 2016-05-31 | 2016-05-31 | A kind of LED backlight circuit and liquid crystal TV set |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111880973A (en) * | 2020-06-16 | 2020-11-03 | 合肥松豪电子科技有限公司 | Short circuit detection mode applied to touch sensor for touch display |
| CN113296017A (en) * | 2021-05-20 | 2021-08-24 | 广东高标电子科技有限公司 | Vehicle lamp fault detection system, electric vehicle and vehicle lamp fault detection method |
-
2016
- 2016-05-31 CN CN201620512146.9U patent/CN205793505U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111880973A (en) * | 2020-06-16 | 2020-11-03 | 合肥松豪电子科技有限公司 | Short circuit detection mode applied to touch sensor for touch display |
| CN113296017A (en) * | 2021-05-20 | 2021-08-24 | 广东高标电子科技有限公司 | Vehicle lamp fault detection system, electric vehicle and vehicle lamp fault detection method |
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