CN104966494A - LED driving circuit for display screen back lighting - Google Patents
LED driving circuit for display screen back lighting Download PDFInfo
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- CN104966494A CN104966494A CN201510379298.6A CN201510379298A CN104966494A CN 104966494 A CN104966494 A CN 104966494A CN 201510379298 A CN201510379298 A CN 201510379298A CN 104966494 A CN104966494 A CN 104966494A
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Abstract
The invention discloses an LED driving circuit for display screen back lighting, which comprises an NCP5007 chip, wherein the NCP5007 chip comprises a pin FB, a pin GND, a pin EN, a pin Vout and a pin Vbat; the pin FB is connected to a current detection resistor R2, the pin GND is grounded, the pin EN is connected to PWM pulse signals, the pin Vout is connected to a switching diode VD1 and a capacitor C2 which are connected in series, and a plurality of identical LED lamps are connected between a negative electrode of the switching diode VD1 and the pin FB; the pin Vout and the pin Vbat are connected through an inductor L, one end of the inductor L is connected with a positive electrode of the switching diode VD1, and the other end of the inductor L is connected to a capacitor C1; and the pin Vbat is further connected to a power supply. According to the invention, the LED driving circuit is formed through the NCP5007 chip, the structure is simple, external components are small in number, the loss is low, current flowing through the LED lamps is regulated by the resistor R2, the current of the LED lamps can be changed by changing a value of the resistor R2, the PWM pulse signals added to the pin EN can carry out dimming on the LED lamps, and the LED driving circuit is suitable for being popularized and applied in a large scale.
Description
Technical field
The present invention relates to LED drive circuit, particularly relate to a kind of LED drive circuit for display backlight illumination.
Background technology
The backlight of display screen is a most frequently used field of LED, this is because LED has, crystal grain is little, volume is little, lightweight, thickness is thin, sturdy and durable, life-span long, color preference is large, arrangement mode has the series of advantages such as very large dirigibility when using.Along with the increasing of electronic equipment output adopting LCD liquid crystal display screen, to the demand of LED backlight also in continuous rising.
The large multiplex LED of current undersized LCD color monitor makes backlight, because its volume is little, lightweight, sturdy and durable again.Such as in the consumer electronics products such as mobile phone, digital camera, digital camera, game machine, be provided with colorful display screen, the illumination of its key-press backlight and incoming call instruction also all use LED.Also needing to configure flashlamp in the product of advising energy with taking a picture, also will use LED.If a mobile phone calculates by using 8-10 LED, the whole world singlehanded machine demand to LED is all very surprising.
In this series products, following 3 kinds of working methods are taked in back lighting usually: the first, some packaged LED or the LED die that do not encapsulate are directly installed on after LCD scattering film, as the backlight of LCD; The second, it is intrafascicular that the light sent by LED imports optical fiber, and fibre bundle forms a smooth thin slice after LCD scattering film, and light takes out from thin slice, as the back lighting of LCD; The third is edge-light LCD back lighting, and at this moment, after LCD scattering film, fill one piece of transparent or semitransparent bright rectangular plastic block as light conductor, the light sent by LED is injected from a side of unit of plastic, remaining side coated white reflectorized material.
LED marches to the liquid crystal TV set of giant-screen, notebook computer, office automation product.The plurality of advantages such as it has that color representation power is abundant, brightness and white balance are easy to control, volume is little, lightweight, life-span length, environmental protection, future likely will replace the backlight of cold-cathode fluorescence lamp (CCFL) as large-scale LCD completely.
In prior art, the general more complicated of driving circuit of LED, and need external a lot of resistance capacitance components and parts, be unfavorable for improving the efficiency manufactured.
Summary of the invention
Goal of the invention: the object of the invention is to solve deficiency of the prior art, provide a kind of structure simple, outward element is few, the LED drive circuit for display backlight illumination that loss is little.
Technical scheme: a kind of LED drive circuit for display backlight illumination of the present invention, comprise NCP5007 chip, described NCP5007 chip comprises pin FB, pin GND, pin EN, pin Vout, pin Vbat;
Described pin FB is connected with current sense resistor R2, pin GND ground connection, pin EN is connected with pwm pulse signal, and pin Vout is connected with switching diode VD1 and the electric capacity C2 of series connection, the negative pole of described switching diode VD1 be connected with some identical LED between pin FB; Described pin Vout is connected by inductance L with between pin Vbat, and described inductance L one end is connected with the positive pole of switching diode VD1, and the inductance L other end is connected with electric capacity C1; Described pin Vbat is also connected with power supply.
Further, what described inductance L adopted is high frequency ferrite core.
Further, described switching diode VD1 is schottky diode.
Further, described some LED are cascaded structure, and positive pole is connected with the negative pole of switching diode VD1, and positive pole is connected with pin FB.
Further, described electric capacity C1 is 5: 1 with the capacitance ratio of electric capacity C2.
Beneficial effect: the present invention forms LED drive circuit by NCP5007, structure is simple, and outward element is few, loss is little, and the electric current flowing through LED is adjusted by resistance R2, changes resistance R2 value, can change the electric current of LED, the pwm pulse signal being added to EN pin can carry out light modulation to LED.LED adopts and is connected in series, and constant current drives, and ensures that LED luminosity is consistent.Switching diode VD1 adopts schottky diode, and its conduction voltage drop is less, can improve the efficiency of whole circuit, and has the feature of the fast quick-recovery required for on-off circuit.The LED drive circuit for display backlight illumination of the present invention's design is suitable for promoting the use of on a large scale.
Accompanying drawing explanation
Fig. 1 is electrical block diagram of the present invention.
Fig. 2 is NCP5007 chip internal structure block diagram of the present invention.
Embodiment
By particular specific embodiment, embodiments of the present invention are described below, person skilled in the art scholar the content disclosed by this instructions can understand other advantages of the present invention and effect easily.
As shown in Figure 1, a kind of LED drive circuit for display backlight illumination, comprise NCP5007 chip, NCP5007 chip comprises pin FB, pin GND, pin EN, pin Vout, pin Vbat.
Pin FB is connected with current sense resistor R2, pin GND ground connection, and pin EN is connected with pwm pulse signal, and pin Vout is connected with switching diode VD1 and the electric capacity C2 of series connection, the negative pole of switching diode VD1 be connected with some identical LED between pin FB.Be connected by inductance L between pin Vout with pin Vbat, inductance L one end is connected with the positive pole of switching diode VD1, and the inductance L other end is connected with electric capacity C1.Pin Vbat is also connected with power supply.Electric capacity C1 is 5: 1 with the capacitance ratio of electric capacity C2.
As to further optimization of the present invention, what inductance L adopted is high frequency ferrite core.Switching diode VD1 is schottky diode.Some LED are cascaded structure, and positive pole is connected with the negative pole of switching diode VD1, and positive pole is connected with pin FB.
As shown in Figure 2, each pin function is as follows for the cut-away view of NCP5007 chip:
1 pin (FB): feed back input is simulating signal, the electric current outputting to LED can be detected by the detection resistance linking this pin, and electric current delivers to outward element inside, can automatically be adjusted.What input this pin can be simulating signal, also can be width modulation (PWM) pulse signal.Change the impressed voltage signal that this pin is delivered in the resistance of this pin or change, the electric current of LED can be changed, thus adjust its brightness, in order to light modulation.The detection resistance linking this pin is ± 5% or the higher precision resistance of precision as adopted error, accurately can control the electric current (brightness) of LED.As inputted the voltage of this pin more than 700mv, inner comparer will automatically shut down NCP5007, make it to quit work.
2 pin (GND): the ground of power supply and simulating signal.Must ensure good earth, avoid affecting by electric spark causing misoperation, the cabling of PCB is enough wide, excessive so as not to current density, is blown by ground wire.
3 pin (EN): numeral input.When the logical signal of an input high level, NCP5007 starts working.Because inside has connect a pull down resistor, so when this pin is unsettled, outward element does not work.During normal work, EN is necessary for high level, can directly be connected with battery supply.The logic high of input should be 1.8V or the CMOS logic high of mark difficulty.The brightness that pulse-width signal also can adjust LED is added at this pin.
4 pin (Vout): power stage.When this pin is connected with switching diode VD1 with inductance L, the DC voltage that transducer exports is a DC voltage improved.Transducer works in constant current output, but its output voltage is the highest can not more than 22V, once output voltage exceedes superpotential threshold value, outward element will enter off state.Restart it, a logical signal from low to high can be added at EN pin, or reclose again after turning off cell voltage.This pin should switch to ground by bulky capacitor, in order to avoid overvoltage protection (OVP) misoperation, capacitance between 1.0-8.2 μ F, and should use the ceramic capacitor that ESR (equivalent series resistance) is little.
5 pin (Vbat): battery supply inputs.This pin of positive termination of external connection battery.This pin should by the capacitive bypass of high-quality to ground, and the capacitor that available 4.7 μ F/6.3V, ESR are low, as the ceramic condenser of X5R or X7R.Allow it near 2,5 pin when connecting capacitor as far as possible.
NCP5007 has following features: input direct voltage scope is 2.7-5.5V, and output voltage can reach 22V, allows the LED driving several series connection, can adjust the size of output current, make it to match with the requirement of LED, and keep current constant; When input supply voltage changes, the automatic adjustment of LED luminance can be realized; Inside has overvoltage protection, Thermal shutdown to protect; Analog voltage or pwm signal by being added to FB pin regulate the electric current flowing through LED, carry out light modulation to LED; Static standby current is very low, can reduce the power consumption of display screen, extend its serviceable life.All pins have all added the protection diode (ESD) of electrostatic prevention, in order to avoid pin punctures by electrostatic interference.
In the circuit of the present invention's design, the representative value of inductance L is 22 μ H, and if output current is more than 20mA, the direct current resistance of inductance is preferably lower than 0.15 Ω, in order to avoid make power supply conversion efficiency reduce.Output current is more stable, ripple is less to adopt larger inductance to make.In order to reduce the size of inductance, general switching frequency is all higher, at about 1MHz.Inductance L adopts high frequency ferrite core, and switching frequency adapts.Magnetic core size is wanted to bear certain rated current, in order to avoid saturated during work, loss is too large, reduces power supply conversion efficiency.
Switching diode VD1 adopts schottky diode, as MBR0530.Its conduction voltage drop is less, can improve the efficiency of whole circuit, and has the feature of the fast quick-recovery required for on-off circuit.The switching diode only conducting when switching tube ends, the maximum peak inverse voltage born equals output voltage, and average current equals output current when normally working.In this type of circuit general, the schottky diode that current rating is 1A, reverse voltage is 20V/30V/40V all can use.Switching diode VD1 is integrated in outward element by this circuit, makes outward element quantity less.
LED adopts and is connected in series, and constant current drives, and ensures that LED luminosity is consistent.R2 is LED current sense resistor, and change its resistance position, controllable flow crosses the electric current of diode and the brightness of diode, and the electric current that output current and LED are required matches.
The electric current flowing through LED in circuit of the present invention is adjusted by resistance R2, change resistance R2 value, the electric current of LED can be changed, in this circuit, R2 adopts 22 Ω, can meet the requirement of actual back lighting brightness, and the pwm pulse signal being added to EN pin can carry out light modulation to LED, structure is simple, outward element is few, and loss is little, is suitable for promoting the use of on a large scale.
Claims (5)
1., for a LED drive circuit for display backlight illumination, it is characterized in that: comprise NCP5007 chip, described NCP5007 chip comprises pin FB, pin GND, pin EN, pin Vout, pin Vbat;
Described pin FB is connected with current sense resistor R2, pin GND ground connection, pin EN is connected with pwm pulse signal, and pin Vout is connected with switching diode VD1 and the electric capacity C2 of series connection, the negative pole of described switching diode VD1 be connected with some identical LED between pin FB; Described pin Vout is connected by inductance L with between pin Vbat, and described inductance L one end is connected with the positive pole of switching diode VD1, and the inductance L other end is connected with electric capacity C1; Described pin Vbat is also connected with power supply.
2. a kind of LED drive circuit for display backlight illumination according to claim 1, is characterized in that: what described inductance L adopted is high frequency ferrite core.
3. a kind of LED drive circuit for display backlight illumination according to claim 1, is characterized in that: described switching diode VD1 is schottky diode.
4. a kind of LED drive circuit for display backlight illumination according to claim 1, is characterized in that: described some LED are cascaded structure, and positive pole is connected with the negative pole of switching diode VD1, and positive pole is connected with pin FB.
5. a kind of LED drive circuit for display backlight illumination according to claim 1, is characterized in that: described electric capacity C1 is 5: 1 with the capacitance ratio of electric capacity C2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510379298.6A CN104966494A (en) | 2015-06-27 | 2015-06-27 | LED driving circuit for display screen back lighting |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510379298.6A CN104966494A (en) | 2015-06-27 | 2015-06-27 | LED driving circuit for display screen back lighting |
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| CN104966494A true CN104966494A (en) | 2015-10-07 |
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| CN201510379298.6A Pending CN104966494A (en) | 2015-06-27 | 2015-06-27 | LED driving circuit for display screen back lighting |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105636280A (en) * | 2016-03-31 | 2016-06-01 | 深圳多哚新技术有限责任公司 | Backlight circuit of VR display |
| CN107946268A (en) * | 2017-11-30 | 2018-04-20 | 郑州云海信息技术有限公司 | A kind of method and device for strengthening chip operation stability |
| CN108235519A (en) * | 2018-01-29 | 2018-06-29 | 新日(无锡)发展有限公司 | A kind of LED backlight drive circuit for electric vehicle |
| CN109346016A (en) * | 2018-11-29 | 2019-02-15 | 厦门天马微电子有限公司 | Backing structure, the brightness adjusting method of backing structure and display device |
| CN115035867A (en) * | 2022-07-20 | 2022-09-09 | 绵阳惠科光电科技有限公司 | Backlight driving circuit and method, backlight module and display device |
-
2015
- 2015-06-27 CN CN201510379298.6A patent/CN104966494A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105636280A (en) * | 2016-03-31 | 2016-06-01 | 深圳多哚新技术有限责任公司 | Backlight circuit of VR display |
| CN107946268A (en) * | 2017-11-30 | 2018-04-20 | 郑州云海信息技术有限公司 | A kind of method and device for strengthening chip operation stability |
| CN108235519A (en) * | 2018-01-29 | 2018-06-29 | 新日(无锡)发展有限公司 | A kind of LED backlight drive circuit for electric vehicle |
| CN109346016A (en) * | 2018-11-29 | 2019-02-15 | 厦门天马微电子有限公司 | Backing structure, the brightness adjusting method of backing structure and display device |
| CN115035867A (en) * | 2022-07-20 | 2022-09-09 | 绵阳惠科光电科技有限公司 | Backlight driving circuit and method, backlight module and display device |
| CN115035867B (en) * | 2022-07-20 | 2023-04-28 | 绵阳惠科光电科技有限公司 | Backlight driving circuit and method, backlight module and display device |
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| WD01 | Invention patent application deemed withdrawn after publication |