CN1312519C - Backlight module and liquid crystal display using the backlight module - Google Patents

Abstract

A backlight module, comprising at least: multiple lamps L₁-L_nArranged parallel to each other and having a high-voltage end and a low-voltage end, odd lamps _mM 1, 3, 5 …) on the first and second sides, respectively, and even lamps (L)_mM 2, 4, 6 …) on the second side and the first side, respectively; the high-voltage ends of the odd lamps and the even lamps are respectively connected with the first alternating current signal and the second alternating current signal, and the low-voltage ends of the odd lamps and the even lamps are respectively connected with the reference ground. And a liquid crystal display using the backlight module.

Description

Backlight module and liquid crystal display using the backlight module

technical field

The invention relates to a backlight module, in particular to a backlight module which improves luminous uniformity; and discloses a liquid crystal display using the backlight module.

Background technique

Liquid crystal display (Liquid Crystal Display, hereinafter referred to as LCD) panels are increasingly used in many electronic devices, such as display screens of notebook computers, personal digital assistants (Personal Digital Assistant, PDA) and other information products, and even aerospace instrument display systems Both use LCD technology. Such products are usually used in environments with different levels of light and darkness. In order to make the images displayed on the LCD screen have better visibility, the LCD display device needs a backlight (backlight) source, that is, a light source located on the back of the LCD panel. .

FIG. 1 shows a schematic diagram of a known backlight module. As shown in the figure, the high-voltage converter 10 provides multiple high-voltage signals to the backlight module 12 composed of multiple lamps L ₁ -L _n . When the high-voltage terminals HV of the lamps L ₁ -L _n receive the high-voltage signal VS, the low-voltage When the terminal LV is connected to a reference ground, the lamps L ₁ -L _n will be lit.

Figure 2 shows an equivalent schematic diagram of the lamp. Since the characteristics of the lamps L ₁ -L _n are the same, they are collectively referred to as the lamp 14 for description; since the high-voltage terminal HV of the lamp 14 is connected to the high-voltage signal VS, and the low-voltage terminal LV is connected to a reference ground, electrons (electrons) will be generated from the right to Moving to the left, when the electrons move, they will hit the gas (for example: neon) inside the lamp 14, causing the lamp 14 to emit light. However, since the outer frame of the backlight module is mainly a metal frame, and usually the metal frame is connected to the reference ground, stray capacitance C _L1 -C _LN will be generated between the lamp 14 and the metal frame. When the length of the lamp 14 is longer, The more stray _capacitances C _L1 -C _LN are, the greater the leakage current I _CL1 + .

When the size of the backlight module is larger, the number of lamps is also more, and the leakage current caused by stray capacitance is more serious.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a backlight module, which can control the effect of stray capacitance, so that the backlight module can emit light evenly.

In addition, another object of the present invention is to use the backlight module to make the brightness of the display panel of the liquid crystal display uniform.

In order to achieve the stated purpose, the present invention proposes a backlight module, comprising: a plurality of lamps L ₁ -L _n arranged in parallel with each other, and each lamp L ₁ -L _n has a high-voltage end and a low-voltage end, and odd-numbered lamps L _m , where m=1, 3, 5... the high-voltage end and the low-voltage end are respectively placed on a first side and the second side, the even-numbered lamp L _m , where m=2, 4, 6... the high-voltage end and The low-voltage terminals are respectively placed on the second side and the first side; wherein, the high-voltage terminals of the odd-numbered lamps and the even-numbered lamps are respectively connected to a first and second AC signal, and the low-voltage terminals of the odd-numbered lamps and the even-numbered lamps are respectively connected to a reference ground.

In order to achieve the other purpose, the present invention proposes a liquid crystal display, which at least includes: a display panel; and the backlight module is arranged on the back of the display panel to provide a light source for the display panel, so that the display panel can be uniform glow.

Description of drawings

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, preferred embodiments are listed below and described in detail with accompanying drawings.

FIG. 1 shows a schematic diagram of a known backlight module.

Figure 2 shows an equivalent schematic diagram of the lamp.

FIG. 3 shows a schematic diagram of a backlight module of the present invention.

FIG. 4 shows the first embodiment of the backlight module of the present invention.

Fig. 5 shows the equivalent schematic diagram of the stray capacitance of the lamp.

Figure 6 shows the equivalent schematic diagram of the stray capacitance of the lamp.

Symbol Description

10 ~ high voltage converter;

L ₁ -L _n , 14～lights;

12～Backlight module;

30a, 30b ~ high voltage converters.

Detailed ways

FIG. 3 shows a schematic diagram of a backlight module of the present invention. As shown in the figure, the backlight module 12 includes: a plurality of lamps L ₁ -L _n , wherein each lamp L ₁ -L _n is arranged in parallel with each other, the distance between the lamps is equal to each other, and each lamp L ₁ -L _n has A high-voltage terminal HV and a low-voltage terminal LV; the high-voltage terminal HV and low-voltage terminal LV of odd-numbered lamps (L _m , m=1, 3, 5...) are respectively placed on a first side and a second side, and even-numbered lamps (L _m , m=2, 4, 6...), the high voltage end HV and the low voltage end LV are placed on the second side and the first side respectively.

Among them, the high-voltage terminal HV of the odd-numbered lamps is connected to the first AC signal AC1 sent by the high-voltage converter 30a; the high-voltage terminal HV of the even-numbered lamps is connected to the second AC signal AC2 sent by the high-voltage converter 30b. The low-voltage terminals LV of LV are respectively connected to the reference ground terminals.

Due to the stray capacitance effect of the lamp L ₁ -L _n , when the high voltage terminal HV of the lamp L ₁ -L _n receives an AC signal and the low voltage terminal LV is connected to the reference ground, the leakage current phenomenon caused by the stray capacitance makes the lamp The brightness from the high-voltage end HV to the low-voltage end LV of the lamps will become darker and darker, but by the present invention, the high-voltage end HV and the low-voltage end LV of the lamps L ₁ -L _n are arranged alternately, which can prevent the high-voltage end side of the known backlight module from being particularly bright. The shortcoming that the low-voltage end side is particularly dark; moreover, the present invention can distribute the light source of the backlight module evenly by using a diffuser for diffusing the light source.

The present invention does not limit the number of lamps in the backlight module. When the backlight module is larger, it means that the number of lamps inside is also more. For the convenience of description, here, only the backlight module composed of four lamps is used for illustration. . FIG. 4 shows the first embodiment of the backlight module of the present invention. As shown in the figure, the backlight module 12 has lamps L ₁ -L ₄ , wherein each lamp is arranged in parallel, and the high-voltage terminals HV of the lamps L ₁ and L ₃ are placed on the left side of the backlight module 12 to receive the power supplied by the high-voltage converter 30a. The first AC signal AC1 is sent; the high-voltage terminals HV of the lamps L ₂ and L ₄ are placed on the right side of the backlight module 12 to receive the second AC signal AC2 sent by the high-voltage converter 30b; the low-voltage terminals of the lamps L ₁ and L ₃ The terminal LV is placed on the right side of the backlight module 12 and connected to the reference ground terminal; the low voltage terminals LV of the lamps L ₂ and L ₄ are placed on the left side of the backlight module 12 and connected to the reference ground terminal.

The high voltage terminals HV of the lamps L ₁ and L ₃ can compensate the brightness of the low voltage terminals LV of the lamps L ₂ and L ₄ ; the high voltage terminals HV of the lamps L ₂ and L ₄ can compensate the brightness of the low voltage terminals LV of the lamps L ₁ and L ₃ ; The brightness of the backlight module is made more uniform.

In addition, due to the leakage current phenomenon caused by the stray capacitance between the lamp and the metal frame, the phase difference between the first AC signal AC1 and the second AC signal AC2 can be controlled to solve the leakage current problem. In the following, only two lamps are used to illustrate how the present invention uses the phase difference of the AC signal to solve the problem of leakage current.

Fig. 5 shows the equivalent schematic diagram of the stray capacitance of the lamp. As shown in the figure, there are many capacitor groups 51-5n among the lamps, and the relationship of each capacitor will be described below by taking the capacitor group 51 as an example. Since the high-voltage terminal HV of the lamp _L1 receives the first AC signal AC1 and the low-voltage terminal LV of the lamp _L2 is connected to the reference ground, the voltage of the high-voltage terminal HV of the lamp _L1 is greater than the voltage of the low-voltage terminal LV of the lamp _L2 , so a coupling is generated Capacitor C ₁ , in addition, generally the metal frame of the backlight module is connected to the reference ground, so the capacitors C ₂ and C ₃ respectively represent the stray capacitance between the lamps L ₁ , L ₂ and the metal frame. Other capacitor banks can be deduced by analogy.

When the high-voltage terminals HV of lamps L ₁ and L ₂ both receive AC signals AC1 and AC2 of the same phase, lamp L ₁ will generate a current I _C1 through capacitor C ₁ and flow into lamp L ₂ to increase the current of lamp L ₂ , and then increase the brightness of lamp _L2 . Wherein, the currents I _C2 and I _C3 are leakage currents between the lamps L ₁ and L ₂ and the metal frame.

Assume that the brightness of the high-voltage end HV of the lamps L ₁ and L ₂ is 100 nits (brightness unit: candlelight), and the brightness of the low-voltage end LV of the lamps L ₁ and L ₂ is 80 nits. When the current I _C1 flows into L ₂ , the lamp L ₁ The brightness of the high-voltage end HV of the lamp _L2 is 95 nits, the brightness of the low-voltage end LV of the lamp _L2 is 85 nits, and the brightness of the low-voltage end LV of the lamp L2 is increased. Although the brightness of the high-voltage end HV of the lamp _L1 decreases, the overall uniformity is greatly improved of.

The uniformity algorithm of the lamp is to divide the brightness of the low-voltage end by the brightness of the high-voltage end. When the high-voltage end and the low-voltage end of the lamp are not staggered, the uniformity of the lamp is $\frac{80}{100}=0.8,$ After the lamps are arranged in a staggered manner, the uniformity is $\frac{95}{85}=0.89,$ Therefore, the invention can improve the uniformity of the lamp.

Figure 6 shows the equivalent schematic diagram of the stray capacitance of the lamp. The difference from FIG. 5 is that the phase of the first AC signal AC1 received by the high voltage terminal HV of the lamp L ₁ is opposite to the phase of the second AC signal AC2 received by the high voltage terminal HV of the lamp L ₂ . Therefore, the low-voltage terminal LV of the lamp _L2 not only receives the current I _C1 flowing through the capacitor _C1 , but also receives the current I _C2 flowing through the capacitors _C2 and _C3 , which solves the leakage current phenomenon between the lamp and the metal frame, and makes the lamp The low-voltage side LV brightness of L ₂ is increased.

As mentioned above, controlling the phase of the AC signal received by the odd-numbered lamps and the phase of the AC signal received by the even-numbered lamps can eliminate the leakage current phenomenon caused by stray capacitance; among them, the AC signal received by the odd-numbered lamps The signal and the AC signal received by the even-numbered lamps can be generated by the same high-voltage converter or by different high-voltage converters.

The backlight module of the present invention can be combined in any electronic product that needs a backlight source, such as liquid crystal display, etc. The backlight module of the present invention provides a backlight source for the LCD panel, so that the brightness of the picture displayed by the LCD panel is more stable.

The present invention has the following points to be superior to known technology:

1. Improve uniformity: Arrange the high-voltage end and low-voltage end of the lamps alternately, so that the brightness between the lamps can be compensated for each other.

2. Solve the leakage current phenomenon: when the phase difference of the AC signal received by the high-voltage end of the odd-numbered and even-numbered lamps is 180°, the leakage current between the lamp and the metal frame can be eliminated.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection is defined by the claims as presented.

Claims (10)

1. A backlight module, comprising: A plurality of lamps L ₁ -L _n , the lamps L ₁ -L _n are arranged in parallel with each other, and each lamp has a high-voltage end and a low-voltage end, and an odd number of lamps L _m , wherein m=1, 3, 5... the high voltage The high-voltage end and the low-voltage end are placed on a first side and the second side respectively, and the high-voltage end and low-voltage end of even-numbered lamps L _m , where m=2, 4, 6... are respectively placed on the second side and the first side ; Wherein, the high-voltage terminals of the odd-numbered lamps and the even-numbered lamps are respectively connected to a first and second AC signal, and the low-voltage terminals of the odd-numbered lamps and even-numbered lamps are respectively connected to a reference ground. 2. The backlight module according to claim 1, further comprising a first driver disposed on the first side for providing the first AC signal to the high-voltage end of the odd lamps; and, a second A driver, disposed on the second side, is used to provide the second AC signal to the high-voltage end of the even-numbered lamps. 3. The backlight module according to claim 1, wherein the distances between the lamps are the same. 4. The backlight module as claimed in claim 2, wherein the first and second AC signals are in phase with each other. 5. The backlight module as claimed in claim 2, wherein the first and second AC signals are opposite to each other. 6. A liquid crystal display, comprising: a display panel; and A backlight module is arranged on the back of the display panel to provide a light source for the display panel, at least including: A plurality of lamps L ₁ -L _n , the lamps L ₁ -L _n are arranged in parallel with each other, and each lamp has a high-voltage end and a low-voltage end, and an odd number of lamps L _m , wherein m=1, 3, 5... the high voltage The high-voltage end and the low-voltage end are placed on a first side and the second side respectively, and the high-voltage end and low-voltage end of even-numbered lamps L _m , where m=2, 4, 6... are respectively placed on the second side and the first side ; Wherein, the high-voltage terminals of the odd-numbered lamps and the even-numbered lamps are respectively connected to a first and second AC signal, and the low-voltage terminals of the odd-numbered lamps and even-numbered lamps are respectively connected to a reference ground. 7. The liquid crystal display as claimed in claim 6, further comprising a first driver disposed on the first side of the display panel for providing the first AC signal to the high voltage end of the odd lamps; and, A second driver, disposed on the second side of the display panel, is used to provide the second AC signal to the high-voltage end of the even-numbered lamps. 8. The liquid crystal display of claim 6, wherein the distances between the lamps are the same. 9. The liquid crystal display of claim 7, wherein the first and second AC signals are in phase with each other. 10. The liquid crystal display as claimed in claim 7, wherein the first and second AC signals are opposite to each other.