CN100501514C - Backlight circuit for LCD panel - Google Patents
Backlight circuit for LCD panel Download PDFInfo
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- CN100501514C CN100501514C CNB2007101512844A CN200710151284A CN100501514C CN 100501514 C CN100501514 C CN 100501514C CN B2007101512844 A CNB2007101512844 A CN B2007101512844A CN 200710151284 A CN200710151284 A CN 200710151284A CN 100501514 C CN100501514 C CN 100501514C
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Abstract
A multi-lamp backlight system is disclosed. The multi-lamp backlight system includes a plurality of lamps, an inverter circuit and a current balance circuit. The inverter circuit is capable of converting a DC input signal to a pair of AC output signals, which have a 180 degree phase shift. The pair of AC output signals are delivered to the plurality of lamps. The current balance circuit is connected to the low voltage sides of the plurality of lamps for balancing the lamp currents.
Description
Technical field
The present invention system is specially the backlight circuit that is used for large scale liquid crystal demonstration (LCD) about backlight circuit.
Background technology
The LCD panel application is extensive, from portable electric appts to fixedly unit, for example notebook computer, video camera, automated navigation system and industrial machine or the like.LCD panel itself is not luminous, needs to use light source to carry out back lighting.The most frequently used back light is cold-cathode fluorescence lamp (CCFL).CCFL lights and works needs a big ac current signal usually.Use direct supply (for example rechargeable battery) to generate this big AC signal, just need a kind of DC/AC inverter of design to drive CCFL.
In recent years, everybody is dense day by day for the interest of large-scale LCD panel, and the large-scale LCD panel is mainly used in needs such as LCD TV and graphoscope for example and uses a plurality of CCFL that the equipment of high intensity illumination is provided.Current large-scale LCD panel majority is to use the CCFL fluorescent tube of a plurality of length.In general, the terminal of long CCFL fluorescent tube by two independently inverter drive, two inverters provide an alternating voltage separately, two voltage-phases differ 180 degree.Here it is, and what is called shown in Figure 1 is floated modulated structure.Exemplary circuit 100 shown in Figure 1 comprises inverter 110 and 120, is connected respectively to the two ends of long CCFL 130, and is designed for alternating voltage V+ and V-are provided.Floating modulated structure shown in Figure 1 can reduce the leakage current between long CCFL fluorescent tube 130 and the chassis 140, can make the brightness of long CCFL 130 keep evenly thus.Yet along with the increase of CCFL fluorescent tube quantity, it is very complicated that circuit 100 can become.In addition, be difficult to make that electric current is even between each CCFL when using a plurality of CCFL, current unevenness is even will make fluorescent tube shorten serviceable life and also brightness inconsistent.
Fig. 2 is a kind of synoptic diagram of traditional many CCFL back light system 200.Many CCFL back light system 200 comprises a current balance circuit 210, and current balance circuit 210 comprises current balance transformer TC6 to TC10 (TC1 to TC5), and current balance transformer is connected to the high-pressure side of power transformer T1 (T2).Yet the high-pressure side of power transformer T1 (T2) will stand the alternating voltage more than 1000 volts in this application, and therefore, the equipment that is connected to high-pressure side will be paid special attention to safety problem.In addition, the quantity of current balance transformer (T1 to T10) is the twice of fluorescent tube (CCFL 1 to CCFL 5) quantity in this system, makes the complexity of back light system and whole cost greatly increase.
The U.S. shown in Figure 3 the 6th, 781,325 B2 patents and Fig. 4 and Fig. 5 provide many CCFL back light system configuration of some other types.Provided a kind of exemplary circuitry 300 among Fig. 3, this circuit comprises a balancing circuitry 310, and balancing circuitry 310 comprises current balance transformer TC10 to TC18 (TC1 to TC9) again.The design of balancing circuitry 310 is to use 2N-2 current balance transformer to come the electric current of a balance N CCFL.Exemplary circuit 400 shown in Figure 4 comprises a current balance circuit 410, and current balance circuit 410 comprises current balance transformer TC11 to TC20 (TC1 to TC10) again.The design of balancing circuitry 410 is to use 2N current balance transformer to come the electric current of a balance N CCFL.Exemplary circuit 500 shown in Figure 5 comprises a current balance circuit 510, and current balance circuit 510 comprises current balance transformer TC11 to TC20 (TC1 to TC10) again.The design of balancing circuitry 510 is to use 2N current balance transformer to come the electric current of a balance N CCFL equally.The configuration of these all many CCFL back light systems all has shortcomings such as number of elements is many, circuit is complicated, safety is limited.
In addition, many fluorescent tubes back light system commonly used all is to use long CCFL fluorescent tube, costs an arm and a leg, and is difficult to after the damage replace.And long CCFL fluorescent tube can be on the tube wall of bottom accumulation mercury, finally can cause brightness irregularities.Long CCFL also is difficult to make, and it is also big to store required space.
Summary of the invention
Many fluorescent tubes backlight circuit cost efficiency height that the embodiment of the invention provides can not cause safety problem because of the high-pressure side of backlight lamp tube.Many fluorescent tubes backlight circuit that the embodiment of the invention provides uses short backlight lamp tube to replace traditional long fluorescent tube, and the shorter fluorescent tube of two series connection replaces the long fluorescent tube illumination of an original tradition.Many fluorescent tubes backlight circuit provided by the invention can comprise an inverter boards, links to each other with the high-pressure side of backlight lamp tube, also can comprise a current balance type plate, links to each other with the low pressure end of fluorescent tube.In addition, the quantity of the current balance transformer that uses on the current balance type plate is few than classic method.
Description of drawings
Hereinafter embodiment is carried out in conjunction with the following drawings, will make that the present invention's advantage is apparent.
Fig. 1 is a kind of synoptic diagram of traditional back light system.
Fig. 2 is a kind of synoptic diagram of traditional many fluorescent tubes back light system.
Fig. 3 is the synoptic diagram of the traditional many fluorescent tubes back light system of another kind.
Fig. 4 is the synoptic diagram of the traditional many fluorescent tubes back light system of another kind.
Fig. 5 is the synoptic diagram of the traditional many fluorescent tubes back light system of another kind.
The skeleton view of a kind of fluorescent tube array that Fig. 6 provides for the embodiment of the invention.
The synoptic diagram of a kind of many fluorescent tubes back light system that Fig. 7 provides for the embodiment of the invention.
A kind of process flow diagram that drives the method for load that Fig. 8 provides for the embodiment of the invention.
Embodiment
Below with embodiments of the present invention is described in detail.Need to understand, though the present invention is described the embodiment that is not limited to select for use in conjunction with the embodiments.On the contrary, the present invention includes invention spirit and interior all alternatives, variant and the equivalent of invention scope that the appended claim book is defined.
Fig. 6 is a kind of skeleton view of exemplary fluorescent tube array 600.Fluorescent tube array 600 places the rear of LCD panel 610 to be used for illumination.The LCD panel also comprises one from the power supply of power supply input 630 with from the picture intelligence that is used for displayed image of video input 640.Fluorescent tube array 600 is made up of fluorescent tube, CCFL622-1 for example, and 624-1,622-2...... is until 624 1 N.For the back side that makes LCD panel 610 obtains enough balanced brightness, to use a plurality of fluorescent tubes of placement arranged side by side usually.Usually use a plurality of long fluorescent tube of placing side by side during traditional large-scale LCD is used, fluorescent tube array 600 then uses the shorter fluorescent tube of two series connection to replace a long fluorescent tube, greatly reduces the cost of large-scale LCD panel.
As shown in Figure 6, CCFL 622-1 connects with CCFL 624-1, and it is right to form first fluorescent tube.CCFL622-2 connects with CCFL 624-2, forms second and waits the pass right.The rest may be inferred, and CCFL 622-N connects with CCFL 624-N, and it is right to form N fluorescent tube.All fluorescent tubes shown in Figure 6 are used for the illumination of LCD panel 610 to placement arranged side by side.Each fluorescent tube centering, if the length of one of them CCFL is L1, the length of another CCFL is L2, and then these two short CCFL provide jointly and are equivalent to the brightness that length can provide for the long fluorescent tube of tradition of L1+L2.For example, two 26 inches the CCFL brightness that can provide is equivalent to the brightness of a long fluorescent tube in 56 inches LCD panels.By using short fluorescent tube to replace long fluorescent tube, can save the cost more than 40%.
Fig. 7 drives the circuit 700 of multi-load (for example a plurality of CCFL fluorescent tube) for a kind of exemplary being used to.Circuit 700 comprises an inverter boards 710 and a current balance type plate 720.Inverter boards 710 be designed for provide alternating voltage+V and-V, both phase phasic differences 180 degree.Alternating voltage+V and-V is connected to first group of load, and (for example (for example CCFL 734-1 is to the high-pressure side HV1 to HVN of CCFL 734-N), and two groups of loads and CCFL shown in Figure 6 are similar to CCFL 732-N) and second group of load for CCFL 732-1.By alternating voltage+V and-V drives, CCFL lights and works and is used for illumination.Current balance type plate 720 is designed for the electric current between each CCFL of balance.Be different from the traditional circuit that the current balance type plate links to each other with the CCFL high-pressure side, the low pressure end of current balance type plate 720 and CCFL (be LV1 to LVN with LV1 ' to LVN ') links to each other.Therefore, the overall cost of current balance type plate 720 just decreases.In addition, the safety problem that causes because of high pressure has also been avoided in this design, thereby a kind of method of reliable balance lamp current is provided.
In addition, resonant capacitance 718 (719) is in parallel with the secondary winding of transformer 714 (716).The lamp current detecting element is connected to the secondary of transformer 714 and 716, to generate the power that the current feedback signal indicating is transferred to CCFL.Driver 712 is adjusted power according to the current feedback signal, until reaching default performance number.
Current balance type plate 720 also comprise (N-2) individual current balance transformer 722-1...... until 722-(N-2)/2 and 724-1...... until 724-(N-2)/2.By using these current balance transformers, the low pressure end of adjacent C CFL or link to each other by main winding or secondary winding, or be associated by magnetic field.For example, CCFL 732-1 and the main windings in series of CCFL 732-2 by current balance transformer 722-1.CCFL 732-3 and CCFL 732-4 pass through the secondary winding of current balance transformer 722-1 and the main windings in series of current balance transformer 722-2.Similar with it, CCFL 732-(N-1) connects by the secondary winding of current balance transformer 722-(N-2)/2 with CCFL 732-N.In addition, CCFL 732-2 is associated by the magnetic field of transformer 722-1 with CCFL 732-3.Similar with it, CCFL 732-(N-2) is associated by the magnetic field of transformer 722-(N-2)/2 with CCFL 732-(N-1).When the turn ratio of transformer 722-1 and 722-(N-2)/2 was set at 1: 1, the size of current that flows through among each CCFL that links to each other will be equal fully.Therefore, CCFL 732-1 is able to balance to the electric current of CCFL 732-N.Similar with it, CCFL 734-1 also is able to balance to the electric current of CCFL 734-N.
Than Fig. 2 to conventional arrangement shown in Figure 5, the quantity of the current balance transformer in the circuit 700 is wanted much less.For instance, for the application of 20 fluorescent tubes, circuit shown in Figure 2 needs 40 current balance transformers and 2 power transformers.And structure shown in Figure 3 need need 38 current balance transformers and 2 power transformers, and Fig. 4 and structure shown in Figure 5 then need 40 current balance transformers and 2 power transformers.And circuit shown in Figure 7 is only as long as 8 current balance transformers and 2 power transformers just can drive 20 fluorescent tubes.In addition, the current balance transformer of circuit shown in Figure 7 all is positioned at the low pressure end of fluorescent tube, the problem of having avoided high pressure to cause, thus a kind of method of reliable balance lamp current is provided.Moreover circuit shown in Figure 7 is easy to realize error-detecting and holding circuit.Generally speaking, the present invention's embodiment has reduced system cost, and a kind of reliable and effective back light system solution is provided, and can be used for during large-scale LCD etc. uses.
Fig. 8 is a kind of process flow diagram that is used to drive the method for a plurality of loads provided by the invention.Need to understand, though Fig. 8 has disclosed a plurality of concrete steps, these steps all are exemplary.In other words, the present invention can carry out equally various other step and the variant of step shown in Figure 8.
In the step 810, generate first alternating voltage and second alternating voltage.In one embodiment of the invention, a DC voltage is converted into an interstage exchange voltage, is converted to first alternating voltage and is converted to second alternating voltage by second transformer by first transformer again, and the polarity of second transformer is opposite with first transformer.
In the step 820, first alternating voltage and the second alternating voltage alternating action in a plurality of loads of parallel connection to last.Each load is to all having a high-pressure side and a low pressure end.First alternating voltage and the second alternating voltage alternating action are in high-pressure side.
In the step 830, use the current balance type plate balanced load electric current that is connected low pressure end.
Wording and expression in this use all are illustrative rather than definitive thereof, use these wording and express not and will get rid of outside invention scope, may have various modifications within the scope of the claims at any equivalent (or part equivalent) of the characteristic of this diagram and description.Other modification, variant and alternative also may exist.Therefore, claim is intended to contain all these type of equivalents.
Claims (23)
1. a circuit is characterized in that, comprising:
An inverter boards is used for a DC voltage is converted to first alternating voltage and second alternating voltage;
First group of load, first group of load has first group of high-pressure side, is connected to above-mentioned inverter boards and receives described first alternating voltage, and first group of load also has first group of low pressure end;
Second group of load, second group of load has second group of high-pressure side, is connected to above-mentioned inverter boards and receives described second alternating voltage, and second group of load also has second group of low pressure end;
A current balance type plate is connected to above-mentioned first group of low pressure end and second group of low pressure end, is used for the balanced load electric current.
2. the circuit according to claim 1 is characterized in that, described inverter boards also comprises:
A driver is used for DC voltage is converted to interstage exchange voltage;
First transformer links to each other with above-mentioned driver being described first alternating voltage with described interstage exchange voltage transitions;
Second transformer links to each other with above-mentioned driver being described second alternating voltage with described interstage exchange voltage transitions.
3. the circuit according to claim 2 is characterized in that described driver is chosen: full bridge driver from following type; Half-bridge driver; Push-pull driver.
4. the circuit according to claim 2 is characterized in that, described first transformer is opposite with second polarity of transformer.
5. the circuit according to claim 1 is characterized in that, described first alternating voltage is pressed with 180 degree phase differential with respect to second alternating current.
6. the circuit according to claim 1 is characterized in that, it is right that described first group of load and second group of load are connected to a plurality of loads in parallel, and each load is to all comprising first load and second load that is in series.
7. the circuit according to claim 6 is characterized in that, the described first load length is L1, and the second load length is L2, and first load and second load can provide the brightness that load provided of length for L1+L2 jointly.
8. the circuit according to claim 1 is characterized in that, described first group of load and second group of load comprise cold-cathode fluorescence lamp.
9. the circuit according to claim 1 is characterized in that, described current balance type plate also comprises a plurality of balancing transformers, and the turn ratio of each balancing transformer all is 1 to 1.
10. the backlight circuit according to claim 9 is characterized in that, the sum of described first group of load and second group of load is no more than the twice of described balancing transformer quantity.
11. a method that is used to drive a plurality of loads is characterized in that, comprising:
Generate first alternating voltage and second alternating voltage;
In a plurality of loads, each load in described a plurality of loads all has a high-pressure side and a low pressure end with first alternating voltage and the second alternating voltage alternating action, and described first alternating voltage and the second alternating voltage alternating action are in high-pressure side;
Use is connected to the current balance type plate balanced load electric current of low pressure end.
12. the method according to claim 11 is characterized in that, described first alternating voltage and second alternating voltage be phasic difference 180 degree mutually.
13. the method according to claim 11 is characterized in that, also comprises:
A DC voltage is converted to interstage exchange voltage;
Is described first alternating voltage by first transformer with the interstage exchange voltage transitions;
Is described second alternating voltage by second transformer with the interstage exchange voltage transitions, and wherein the polarity of second transformer is opposite with first transformer.
14. the method according to claim 11, it is characterized in that, it is right that described a plurality of load is arranged to a plurality of loads, each load is to being made up of two loads of series connection, the first load length is L1, second load is L2, and first load and second load provide the brightness that load provided of length for L1+L2 jointly.
15. the method according to claim 11 is characterized in that, described current balance type plate also comprises a plurality of current balance transformers, and the turn ratio of each current balance transformer all is 1 to 1.
16. the method according to claim 15 is characterized in that the load sum of described a plurality of loads is not more than the twice of described current balance transformer quantity.
17. the method according to claim 11 is characterized in that, described a plurality of loads comprise cold-cathode fluorescence lamp.
18. a display system is characterized in that, comprising:
A power supply input is used to receive power supply;
A video input is used to receive picture intelligence;
A liquid crystal panel, input links to each other with video with above-mentioned power supply input, is used for displayed image;
A fluorescent tube array, be used for the liquid crystal panel backlight illumination, wherein said fluorescent tube array by a plurality of fluorescent tubes to composing in parallel, each fluorescent tube is to all having a high-pressure side and a low pressure end, the right high-pressure side of adjacent fluorescent tube alternately is connected to a positive alternating voltage and a negative alternating voltage, and the right low pressure end of adjacent fluorescent tube is connected to a current balance type plate that is used for the balance lamp current.
19. the display system according to claim 18 is characterized in that, described positive alternating voltage and negative alternating voltage are provided by same inverter boards, and this inverter boards comprises:
A driver is used for a DC voltage is converted to interstage exchange voltage;
First transformer that links to each other with driver, being used for the interstage exchange voltage transitions is described positive alternating voltage;
Second transformer that links to each other with driver, being used for the interstage exchange voltage transitions is described negative alternating voltage.
20. the display system according to claim 18 is characterized in that, each fluorescent tube is to all comprising one first fluorescent tube, and length is L1, comprises one second fluorescent tube, and length is L2, and two fluorescent tube series connection provide the brightness that fluorescent tube provided of length for L1+L2 jointly.
21. the display system according to claim 18 is characterized in that, described current balance type plate comprises a plurality of current balance transformers, and wherein the turn ratio of each current balance transformer all is 1 to 1.
22. the display system according to claim 21 is characterized in that, the fluorescent tube quantity in the described fluorescent tube array is no more than the twice of described current balance transformer quantity.
23. the display system according to claim 18 is characterized in that, described fluorescent tube array comprises cold-cathode fluorescence lamp.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84586406P | 2006-09-19 | 2006-09-19 | |
| US60/845,864 | 2006-09-19 | ||
| US11/809,046 | 2007-05-30 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101149498A CN101149498A (en) | 2008-03-26 |
| CN100501514C true CN100501514C (en) | 2009-06-17 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2007101512844A Expired - Fee Related CN100501514C (en) | 2006-09-19 | 2007-09-18 | Backlight circuit for LCD panel |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN100501514C (en) |
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2007
- 2007-09-18 CN CNB2007101512844A patent/CN100501514C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CN101149498A (en) | 2008-03-26 |
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