CN107945746A - Led backlight drive circuit and liquid crystal display device - Google Patents
Led backlight drive circuit and liquid crystal display device Download PDFInfo
- Publication number
- CN107945746A CN107945746A CN201711147915.5A CN201711147915A CN107945746A CN 107945746 A CN107945746 A CN 107945746A CN 201711147915 A CN201711147915 A CN 201711147915A CN 107945746 A CN107945746 A CN 107945746A
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- voltage
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- control chip
- drive control
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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
Abstract
The invention discloses a kind of LED backlight drive circuit, including input power, BUCK reduction voltage circuits, LED light source and drive control chip, the input voltage of the input power is transformed to output voltage and is supplied to the LED light source by BUCK reduction voltage circuits described in the drive control chip controls, wherein, the LED backlight drive circuit further includes：Enable signal circuit, for providing enable signal to the drive control chip；Voltage sampling circuit, the sampled voltage of the output voltage size is reflected for obtaining；Comparison circuit, by the sampled voltage compared with reference voltage, if the sampled voltage is more than reference voltage, controls the enable signal circuit to provide low level enable signal to the drive control chip.The drive circuit can prevent output terminal overvoltage from causing LED light source to be burned out.
Description
Technical field
The present invention relates to display technology field, and in particular to a kind of LED backlight drive circuit and liquid crystal display device.
Background technology
With the continuous progress of technology, the backlight technology of liquid crystal display is continuously available development.Traditional liquid crystal display
The backlight of equipment uses cold-cathode fluorescence lamp (CCFL).But due to CCFL backlight there are color restoration capability it is poor, hair
Light efficiency is low, under discharge voltage high and low temperature flash-over characteristic it is poor, heating reach the stable gray scale time it is long the shortcomings of, currently opened
Send the back light source technique using LED backlight.In liquid crystal display, LED backlight is opposite with liquid crystal display panel to be set
Put, so that LED backlight provides display light source to liquid crystal display panel, wherein, LED backlight is gone here and there including at least one LED, often
A LED strings include multiple LED light of series connection.
For the drive circuit of LED light source, the object of output control is the electric current for flowing through LED light source, and voltage is usual
No longer be object of concern, thus some by voltage band Lai influence may ignore.Fig. 1 is that existing one kind is used for liquid
The circuit diagram of the drive circuit of the LED backlight of crystal display.As shown in Figure 1, the circuit employs the LED drivings of BUCK frameworks
Circuit, in this circuit, Vin are input voltage, load what is formed for LED light D1~Dn of the LED light source including multiple series connection
LED goes here and there, and drive control chip is turned on and off according to enable signal EN, and the break-make of MOS transistor Q is controlled by pwm signal, will
Input voltage vin is transformed to output voltage and is supplied to LED to go here and there.Wherein, the electric current flowed through forms output voltage at LED strings both ends,
Resistance Rs is used for the detection of output current, drive control chip by the electric current of detection resistance Rs to the duty cycle of pwm signal into
Row control, capacitance Co are filtered output current so that the final electric current for flowing through LED strings is stable direct current.In order to reduce
Unnecessary loss, the pressure difference very little on resistance Rs, the pressure difference on LED string both ends and capacitance Co are very close.
As Fig. 1 drive circuit in, when LED strings are opened a way in some cases, do not flow through the current channel of LED strings not
In the presence of so the pressure difference on resistance Rs is 0, the duty cycle for making pwm signal automatically is raised to maximum and held by drive control chip
It is continuous to be in this state.In the process, output capacitance Co can only be flowed through since MOS transistor Q opens the electric current to be formed, so
Voltage on capacitance Co will be equal to input voltage vin.In BUCK frameworks, input voltage vin is always greater than the LED both ends gone here and there
Voltage, and the voltage in capacitance Co is already higher than normal LED strings conducting voltage at this time, if LED is concatenated into electricity again at this time
Road, the electric energy being deposited in capacitance Co just will unrestrictedly flow through LED strings, and LED strings are difficult the impact for bearing such electric current, incited somebody to action
Heat and be burned out.
The content of the invention
In view of the shortcomings of the prior art, the present invention provides a kind of LED backlight drive circuit, the drive circuit can
To prevent output terminal overvoltage from causing LED light source to be burned out.
To achieve the above object, present invention employs following technical solution：
A kind of LED backlight drive circuit, including input power, BUCK reduction voltage circuits, LED light source and drive control chip,
The input voltage of the input power is transformed to output voltage and carried by BUCK reduction voltage circuits described in the drive control chip controls
The LED light source is supplied, wherein, the LED backlight drive circuit further includes：Enable signal circuit, is connected to the driving control
Coremaking piece, for providing enable signal to the drive control chip；Voltage sampling circuit, is connected to the BUCK reduction voltage circuits
Output terminal, the sampled voltage of the output voltage size is reflected for obtaining；Comparison circuit, is connected to the voltage sample electricity
Between road and the enable signal circuit, by the sampled voltage compared with reference voltage, if the sampled voltage is more than
Reference voltage, controls the enable signal circuit to provide low level enable signal to the drive control chip.
Specifically, the enable signal circuit includes first resistor and the first MOS transistor, and the first of the first resistor
End is connected to the output terminal of the input power, and the second end of the first resistor is connected to the leakage of first MOS transistor
Pole, the grid of first MOS transistor are connected to the output terminal of the comparison circuit, and source electrode is electrically connected with ground；Wherein, from
The second end of the first resistor picks out the enable signal and is connected to the drive control chip, defeated when the comparison circuit
Outlet exports high level, and the first MOS transistor conducting, the enable signal is low level.
Specifically, the voltage sampling circuit includes second resistance and 3rd resistor, and the first end of the second resistance connects
The cathode of the output terminal of the BUCK reduction voltage circuits is connect, the second end of the second resistance connects the first of the 3rd resistor
End, the second end of the 3rd resistor connect the anode of the output terminal of the BUCK reduction voltage circuits；Wherein, from the second resistance
Second end connection comparison circuit, with to the comparison circuit export sampled voltage.
Specifically, the comparison circuit includes voltage comparator, described in the normal phase input end connection of the voltage comparator
The second end of second resistance, inverting input receive the reference voltage, and the output terminal of the voltage comparator is connected to described
The grid of first MOS transistor.
Specifically, the BUCK reduction voltage circuits include storage capacitor, output capacitance, inductance, diode and the 2nd MOS crystal
Pipe, the first end of the storage capacitor are connected to the output terminal of the input power, and second end is electrically connected with ground, the output
The first end of capacitance is connected to the first end of the storage capacitor, and the second end of the output capacitance connects the first of the inductance
End, the second end of the inductance are connected to the drain electrode of second MOS transistor, and the grid of second MOS transistor receives
From the pwm control signal of drive control chip output, source electrode is electrically connected with ground；The cathode of the diode is connected to institute
The second end of inductance is stated, anode is connected to the first end of the output capacitance；Wherein, the LED light source is connected to the output
It is in parallel with the output capacitance between the first end and second end of capacitance.
Specifically, the LED light source includes multiple LED light of series connection.
Specifically, current sampling circuit, the electricity are provided between the first end of the LED light source and the output capacitance
Stream sample circuit is used to obtain the electric current for flowing through the LED light source and feeds back to the drive control chip, the drive control
Chip adjusts the pwm control signal according to the size of the electric current, to realize that constant current drives the LED light source.
Specifically, the current sampling circuit includes the 4th resistance, and the 4th resistance and the LED light are source-series, institute
The first end for stating the 4th resistance is connected to the first end of the output capacitance, and the second end of the 4th resistance is connected to described
LED light source；Wherein, the drive control chip is connected from the second end of the 4th resistance, with to the drive control chip
Input sample electric current.
Specifically, the storage capacitor is also parallel with a filter capacitor.
Another aspect of the present invention is to provide a kind of liquid crystal display device, and the liquid crystal display device includes LED backlight,
Wherein, the LED backlight uses LED backlight drive circuit as described above.
Compared with the prior art, in LED backlight drive circuit provided in an embodiment of the present invention, it is provided with voltage output end
Voltage sampling circuit, by the sampled voltage of the reflection output voltage size of acquisition compared with reference voltage, if the sampling
Voltage is more than reference voltage, and it is low level to control enable signal, so as to control drive control chip to stop driving, effectively prevents
Output terminal overvoltage causes LED light source to be burned out.
Brief description of the drawings
Fig. 1 is a kind of circuit diagram of existing LED backlight drive circuit；
Fig. 2 is the structure diagram of LED backlight drive circuit provided in an embodiment of the present invention；
Fig. 3 is the circuit diagram of LED backlight drive circuit provided in an embodiment of the present invention；
Fig. 4 is the structure diagram of liquid crystal display device provided in an embodiment of the present invention.
Embodiment
To make the object, technical solutions and advantages of the present invention clearer, below in conjunction with the accompanying drawings to the specific reality of the present invention
The mode of applying is described in detail.The example of these preferred embodiments is illustrated in the accompanying drawings.Shown in attached drawing and according to
What the embodiments of the present invention of attached drawing description were merely exemplary, and the present invention is not limited to these embodiments.
Here, it should also be noted that, in order to avoid having obscured the present invention because of unnecessary details, in the accompanying drawings only
Show the structure and/or processing step closely related with scheme according to the present invention, and eliminate little with relation of the present invention
Other details.
The present embodiment provide firstly a kind of LED backlight drive circuit, refering to Fig. 2 and Fig. 3, the LED backlight driving electricity
Road includes input power 1, BUCK reduction voltage circuits 2, LED light source 3 and drive control chip 4, and the drive control chip 4 controls institute
State BUCK reduction voltage circuits 2 input voltage vin of the input power 1 is transformed to output voltage and be supplied to the LED light source 3.
Further, the LED backlight drive circuit further includes enable signal circuit 5, voltage sampling circuit 6, comparison circuit 7 and electric current
Sample circuit 8.
Wherein, the enable signal circuit 5 is connected to the drive control chip 4, for the drive control chip 4
Enable signal EN is provided, when the enable signal EN be high level, the unlatching of drive control chip 4 working status, to described
BUCK reduction voltage circuits 2 export pwm control signal；When the enable signal EN is low level, the drive control chip 4 closes work
Make state, stop exporting pwm control signal to the BUCK reduction voltage circuits 2.The voltage sampling circuit 6 is connected to the BUCK
The output terminal of reduction voltage circuit 2, the sampled voltage Vs of the output voltage size is reflected for obtaining.The comparison circuit 7 connects
Between the voltage sampling circuit 6 and the enable signal circuit 5, the comparison circuit 7 is also associated with reference voltage V ref,
The comparison circuit 7 by the sampled voltage Vs compared with reference voltage V ref, if the sampled voltage Vs is more than benchmark
Voltage Vref, then control the enable signal circuit 5 to provide low level enable signal EN to the drive control chip 4.Institute
State current sampling circuit 8 to be connected between the LED light source 3 and the drive control chip 4, the LED is flowed through for obtaining
The electric current IS of light source 3 simultaneously feeds back to the drive control chip 4, and the drive control chip 4 is according to the size of the electric current IS
The duty cycle of the pwm control signal is adjusted, to realize that constant current drives the LED light source 3.
Specifically, as shown in figure 3, the BUCK reduction voltage circuits 2 include storage capacitor Cp, output capacitance Co, inductance L, two
Pole pipe D and the second MOS transistor Q2.The first end of the storage capacitor Cp is connected to the output terminal (connection of the input power 1
To input voltage vin), second end is electrically connected with ground.The first end of the output capacitance Co is connected to the storage capacitor Cp
First end, the second end of the output capacitance Co connects the first end of the inductance L, and the second end of the inductance L is connected to
The drain electrode of the second MOS transistor Q2, the grid reception of the second MOS transistor Q2 are defeated from the drive control chip 4
The pwm control signal gone out, source electrode are electrically connected with ground.The cathode of the diode D is connected to the second end of the inductance L, bears
Pole is connected to the first end of the output capacitance Co.In the present embodiment, the storage capacitor Cp and output capacitance Co points
Wei not polar capacitor.Further, the storage capacitor Cp be also parallel with filter capacitor a C, the filter capacitor C specifically can be with
Using ceramic capacitor.
Wherein, the LED light source 3 is connected between the first end and second end of the output capacitance Co, with the output
Capacitance Co is in parallel.Specifically, in the present embodiment, the LED light source 3 includes multiple LED light 31 of series connection.
Specifically, as shown in figure 3, the enable signal circuit 5 includes first resistor R1 and the first MOS transistor Q1.Institute
The first end for stating first resistor R1 is connected to the output terminal (being connected to input voltage vin) of the input power 1, first electricity
The second end of resistance R1 is connected to the drain electrode of the first MOS transistor Q1, and the grid of the first MOS transistor Q1 is connected to institute
The output terminal of comparison circuit 7 is stated, source electrode is electrically connected with ground.Wherein, described make is picked out from the second end of the first resistor R1
Energy signal EN is connected to the drive control chip 4, when the output terminal of the comparison circuit 7 exports high level, the first MOS
Transistor turns Q1, by the enable signal EN down for low level.
Specifically, as shown in figure 3, the voltage sampling circuit 6 includes second resistance R2 and 3rd resistor R3, described second
The first end of resistance R2 connects the cathode of the output terminal of the BUCK reduction voltage circuits, the second end connection institute of the second resistance R2
The first end of 3rd resistor R3 is stated, the second end of the 3rd resistor R3 connects the negative of the output terminal of the BUCK reduction voltage circuits 2
Pole.More specifically, in the present embodiment, the first end of the second resistance R2 is connected to the cathode of the output capacitance Co, described
The second end of 3rd resistor R3 is connected to the anode of the output capacitance Co；Wherein, connect from the second end of the second resistance R2
The comparison circuit 7 is connected to, to export sampled voltage Vs to the comparison circuit 7.
Specifically, as shown in figure 3, the comparison circuit 7 includes voltage comparator OP, the positive of the voltage comparator OP
For the second end of input terminal second resistance R2 to receive the sampled voltage Vs, inverting input receives the reference voltage V ref,
The output terminal of the voltage comparator OP is connected to the grid of the first MOS transistor Q1 in the enable signal circuit 5.Work as institute
State sampled voltage Vs and be more than reference voltage V ref, then the enable signal EN that the enable signal circuit 5 exports is low level, works as institute
State sampled voltage Vs and be less than or equal to reference voltage V ref, then the enable signal EN that the enable signal circuit 5 exports is high electricity
It is flat.
Specifically, as shown in figure 3, in the present embodiment, the current sampling circuit 8 is connected to the LED light source 3 and described
Between the first end of output capacitance Co.The current sampling circuit 8 includes the 4th resistance R4, the 4th resistance R4 with it is described
LED light source 3 is connected, and the first end of the 4th resistance R4 is connected to the first end of the output capacitance Co, the 4th resistance
The second end of R4 is connected to the LED light source 3.Wherein, the drive control core is connected from the second end of the 4th resistance R4
Piece 4, with to the 4 input sample electric current IS of drive control chip.
The LED backlight drive circuit of example offer is provided, when the LED light source 3 is normal connection status, the voltage
The sampled voltage Vs that sample circuit 6 obtains is less than or equal to reference voltage V ref, and the comparison circuit 7 exports low level signal,
The first MOS transistor Q1 in the enable signal circuit 5 is disconnected, from the first resistor R1 partial pressures of the enable signal circuit 5
The enable signal EN of acquisition is high level, and the drive control chip 4 opens working status, defeated to the BUCK reduction voltage circuits 2
Go out pwm control signal, keep the LED backlight drive circuit driven.When the LED light source 3 is opened a way, the output electricity
The pressure difference for holding Co both ends raises, and the sampled voltage Vs that 3rd resistor R3 partial pressures obtain in the voltage sampling circuit 6 is increased,
When sampled voltage Vs is more than reference voltage V ref, the comparison circuit 7 exports high level signal, in the enable signal circuit 5
The first MOS transistor Q1 conductings, by the enable signal EN down for low level, the drive control chip 4 closes work
State, stops exporting pwm control signal to the BUCK reduction voltage circuits 2, avoids the pressure difference at the output capacitance Co both ends from continuing
Rise.When connecting the LED light source 3 herein at this time, the LED light source 3 will not be because of the pressure difference mistake at the output capacitance Co both ends
It is high and be burned out, it is effectively protected LED light source 3.
Further, the present embodiment additionally provides a kind of liquid crystal display device, as shown in figure 4, the liquid crystal display device
Including liquid crystal panel 100 and backlight module 200, the liquid crystal panel 100 is oppositely arranged with the backlight module 200, the back of the body
Optical mode group 200 provides display light source to the liquid crystal panel 100, so that the liquid crystal panel 100 shows image.Wherein, it is described
Backlight module 200 is LED backlight module, and which employs the LED backlight drive circuit that present invention is provided.
In conclusion in LED backlight drive circuit provided in an embodiment of the present invention, voltage output end is provided with voltage and adopts
Sample circuit, by the sampled voltage of the reflection output voltage size of acquisition compared with reference voltage, if the sampled voltage is big
In reference voltage, it is low level to control enable signal, so as to control drive control chip to stop driving, effectively prevents output terminal
Overvoltage causes LED light source to be burned out.
It should be noted that herein, relational terms such as first and second and the like are used merely to a reality
Body or operation are distinguished with another entity or operation, are deposited without necessarily requiring or implying between these entities or operation
In any this actual relation or order.Moreover, term " comprising ", "comprising" or its any other variant are intended to
Non-exclusive inclusion, so that process, method, article or equipment including a series of elements not only will including those
Element, but also including other elements that are not explicitly listed, or further include as this process, method, article or equipment
Intrinsic key element.In the absence of more restrictions, the key element limited by sentence "including a ...", it is not excluded that
Also there are other identical element in process, method, article or equipment including the key element.
The above is only the embodiment of the application, it is noted that for the ordinary skill people of the art
For member, on the premise of the application principle is not departed from, some improvements and modifications can also be made, these improvements and modifications also should
It is considered as the protection domain of the application.
Claims (10)
1. a kind of LED backlight drive circuit, including input power, BUCK reduction voltage circuits, LED light source and drive control chip, institute
State BUCK reduction voltage circuits described in drive control chip controls the input voltage of the input power is transformed to output voltage and provide
To the LED light source, it is characterised in that the LED backlight drive circuit further includes：
Enable signal circuit, is connected to the drive control chip, for providing enable signal to the drive control chip；
Voltage sampling circuit, is connected to the output terminal of the BUCK reduction voltage circuits, reflects the output voltage size for obtaining
Sampled voltage；
Comparison circuit, is connected between the voltage sampling circuit and the enable signal circuit, by the sampled voltage and base
Quasi- voltage is compared, if the sampled voltage is more than reference voltage, controls the enable signal circuit to the drive control
Chip provides low level enable signal.
2. LED backlight drive circuit according to claim 1, it is characterised in that the enable signal circuit includes first
Resistance and the first MOS transistor, the first end of the first resistor are connected to the output terminal of the input power, first electricity
The second end of resistance is connected to the drain electrode of first MOS transistor, and the grid of first MOS transistor is connected to the comparison
The output terminal of circuit, source electrode are electrically connected with ground；Wherein, the enable signal connection is picked out from the second end of the first resistor
To the drive control chip, when the output terminal of the comparison circuit exports high level, the first MOS transistor conducting, institute
It is low level to state enable signal.
3. LED backlight drive circuit according to claim 2, it is characterised in that the voltage sampling circuit includes second
Resistance and 3rd resistor, the first end of the second resistance connect the cathode of the output terminal of the BUCK reduction voltage circuits, and described the
The second end of two resistance connects the first end of the 3rd resistor, and the second end of the 3rd resistor connects the BUCK decompressions electricity
The anode of the output terminal on road；Wherein, comparison circuit is connected from the second end of the second resistance, to be exported to the comparison circuit
Sampled voltage.
4. LED backlight drive circuit according to claim 3, it is characterised in that the comparison circuit compares including voltage
Device, the normal phase input end of the voltage comparator connect the second end of the second resistance, and inverting input receives the benchmark
Voltage, the output terminal of the voltage comparator are connected to the grid of first MOS transistor.
5. according to any LED backlight drive circuits of claim 2-4, it is characterised in that the BUCK reduction voltage circuits bag
Include storage capacitor, output capacitance, inductance, diode and the second MOS transistor, the first end of the storage capacitor is connected to described
The output terminal of input power, second end are electrically connected with ground, and the first end of the output capacitance is connected to the storage capacitor
First end, the second end of the output capacitance connect the first end of the inductance, and the second end of the inductance is connected to described the
The drain electrode of two MOS transistors, the grid of second MOS transistor receive the PWM controls from drive control chip output
Signal, source electrode are electrically connected with ground；The cathode of the diode is connected to the second end of the inductance, and anode is connected to described defeated
Go out the first end of capacitance；Wherein, the LED light source is connected between the first end and second end of the output capacitance, and described
Output capacitance is in parallel.
6. LED backlight drive circuit according to claim 5, it is characterised in that the LED light source includes the multiple of series connection
LED light.
7. LED backlight drive circuit according to claim 5, it is characterised in that the LED light source and the output capacitance
First end between be provided with current sampling circuit, the current sampling circuit is used to obtain the electric current for flowing through the LED light source
And the drive control chip is fed back to, the drive control chip adjusts the PWM controls letter according to the size of the electric current
Number, to realize that constant current drives the LED light source.
8. LED backlight drive circuit according to claim 7, it is characterised in that the current sampling circuit includes the 4th
Resistance, the 4th resistance and the LED light are source-series, and the first end of the 4th resistance is connected to the of the output capacitance
One end, the second end of the 4th resistance are connected to the LED light source；Wherein, institute is connected from the second end of the 4th resistance
Drive control chip is stated, with to the drive control chip input sample electric current.
9. LED backlight drive circuit according to claim 5, it is characterised in that the storage capacitor is also parallel with a filter
Ripple capacitance.
10. a kind of liquid crystal display device, including LED backlight, it is characterised in that the LED backlight uses such as claim
Any LED backlight drive circuits of 1-9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711147915.5A CN107945746A (en) | 2017-11-17 | 2017-11-17 | Led backlight drive circuit and liquid crystal display device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201711147915.5A CN107945746A (en) | 2017-11-17 | 2017-11-17 | Led backlight drive circuit and liquid crystal display device |
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| Publication Number | Publication Date |
|---|---|
| CN107945746A true CN107945746A (en) | 2018-04-20 |
Family
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201711147915.5A Pending CN107945746A (en) | 2017-11-17 | 2017-11-17 | Led backlight drive circuit and liquid crystal display device |
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| Country | Link |
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| CN (1) | CN107945746A (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109755923A (en) * | 2019-02-20 | 2019-05-14 | 广州视源电子科技股份有限公司 | A kind of protection circuit, the method and apparatus of power supply device |
| WO2020103199A1 (en) * | 2018-11-21 | 2020-05-28 | 惠科股份有限公司 | Backlight control circuit and method for controlling same |
| CN112233610A (en) * | 2020-10-16 | 2021-01-15 | Tcl华星光电技术有限公司 | Backlight constant-current control circuit and backlight structure |
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Application publication date: 20180420 |
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