CN102042530A - Backlight panel with series-connected LED components, manufacturing method and display with the backlight panel - Google Patents

Abstract

The backlight plate comprises an energy supply device, serially connected LED components and a liquid crystal module, wherein the energy supply device enables at least two serially connected LED components in parallel connection and the liquid crystal module as a backlight source to be serially connected with the LED components and consists of enough LEDs, so that the power supply voltage required by each string of LEDs approaches to the product of the average voltage and the number of the LEDs, the problem of different forward voltages required by the LEDs is greatly solved, the LED screening cost is reduced, the backlight plate further comprises a light homogenizing device, a front reflector is arranged between a light homogenizing plate and the serially connected LED components, a rear reflector is arranged at the side far away from the light homogenizing plate, and the light emitted by the serially connected LED components is repeatedly projected and homogenized through the two reflectors, so that the effects of reducing the manufacturing cost and improving the yield of products are achieved.

Description

Backlight panel with series-connected LED components, manufacturing method and display with the backlight panel

【Technical field】

The invention relates to a backlight panel, especially an LED backlight panel and a display with the backlight panel, which reduce screening conditions and costs by connecting a large number of light-emitting diode (hereinafter referred to as LED) components in series.

【Background technique】

The application fields of LED are gradually widening, and it has been gradually accepted as the mainstream in the field of backlight panels and displays, but limited by the insufficient brightness of individual LEDs, so it is common to use several LED elements 10 connected in series as shown in Figure 1, and then a single The DC power supply 12 is used as a backlight for a notebook computer, for example. The biggest advantage of this technology of connecting multiple LEDs in series is that it simplifies the driving device of the LED, and can use a larger voltage and a smaller current to provide enough electric power to drive multiple LEDs. The cost of the power supply is small, so it can achieve lower cost purposes.

However, on the one hand, the size of the display is getting larger and larger, and the current notebook computer-sized backlight panel cannot meet the demand for illuminating large-sized panels; especially, the forward drive voltage range of individual LEDs connected in series must be limited to a small range. Otherwise, when the DC power supply designed according to the predetermined circuit flows through the string of LED components, the driving current will be greatly changed from the original design, resulting in a large variation in the brightness of the entire string of LED components.

However, in the process of manufacturing LED components, a wafer is first divided into a batch of 20,000 LED chips, and then packaged into LED components one by one. In the process of wafer manufacturing and segmentation, a small amount of individual differences may occur. To avoid excessive differences in product performance, the entire batch of LED chips is generally tested one by one, and classified according to their forward driving voltage (Bin-Sorting), that is, each LED chip under a certain fixed driving current, according to the The value of the forward drive voltage Vf at the two poles of the LED grain and the luminous brightness are screened. When the forward drive voltage required to light up the die deviates too far from the average value, for example, more than 50mV, it is classified into another classification, thereby ensuring that the forward voltage of the output die conforms to a narrower range. On the other hand, this kind of classification usually needs to eliminate about 10% of the die first, and the cost increases accordingly.

Subsequently, in the packaging process of the components, there may also be a small amount of individual differences due to various process differences, so that the same batch of LED components shipped from the factory, as shown in Figure 2, under the same driving current If (such as the above-mentioned current is 20mA) The forward drive voltage Vf is still a variable, and the range may be between 3.0V and 4.0V, and the V _f value probability distribution (Probability Distribution) P(V _f ) is the inverted bell curve in the figure. The probability P( V _f ) distribution diagram is a distribution close to a normal function Normal Distribution, and its distribution function P(V _f ) can be written as formula (1):

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;V</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}}\mathrm{<span\; class="notranslate">\; e</span>}\frac{<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; av</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

其中V_f表示各个LED元件在正向电流Is下的正向偏压。Among them, the average forward bias value Vav of the whole batch of LED components is 3.5V, and the standard deviation ΔV distribution of the whole batch of output components can reach the range of 0.2V, that is, about 30% of the components are lit under the driving current. , the difference between the forward bias voltage and the average value of 3.5V exceeds 0.2V. Before the entire batch of LED components of the same process leaves the factory, the forward voltage V _f under the same forward current will be measured first, so as to calculate the probability distribution function of the batch of LED components, namely

Among them, V _f represents the forward bias voltage of each LED element under the forward current Is.

In order to make product performance easy to predict and control, the manufactured LED components will be classified according to their respective forward bias voltage, luminous brightness and uniformity, and the finer the classification, the higher the classification accuracy requirements, and the cost and The higher the cost of collection and processing. Generally speaking, a forward bias voltage difference of 0.1V is often used as a sub-category. Therefore, under the above-mentioned 1V difference, all products need to be divided into about 10 categories. However, with a forward bias voltage error of 0.1V, generally for the blue light or green light of the RGB light-emitting module, it can already cause about 20% of the current error, and thus produce about 20% of the brightness error. For a backlight that requires high uniformity, it still needs to be improved.

Based on the above, since the average forward drive voltage of this batch of LED components is 3.5V when they are tested with a 20mA drive current before leaving the factory, if they are not classified, generally when choosing a circuit design that connects, for example, 10 white LED components in series, The total driving voltage Vcc required will be designed to be 35V. But in practice, unless the number of components is small, the forward bias voltage actually required to provide a normal drive current can easily deviate from the theoretical average value unless it is specially screened. Refer to the IV curve of a typical LED component in Figure 3. Generally, the higher the V _f value, the greater the current I _f ; and the relationship between the current I _f and the luminous brightness B is shown in Figure 4. After exceeding the basic driving current, The luminous brightness increases approximately linearly with the current value. Once the total forward drive voltage of these 10 LED components is greater than the theoretical value of 35V and falls to 38V, for example, the drive current flowing through the entire string of LED components may suddenly drop to 12mA with the above-mentioned predetermined Vcc=35V. The driving conditions will make the brightness of the whole string of LEDs differ by 40% from the original design value, resulting in an unacceptable problem of insufficient brightness.

Especially the current large-scale LCD monitors require a large number of LEDs for the backlight panels. For a 42-hour LCD TV, about 3,000 white LEDs (20mA) or 3,000 groups of RGB LEDs are needed to form. If each string is composed of 30 serially connected LED components, the entire backlight panel needs about 100 strings. Even if it is classified according to the above method, it is not only forced to be divided into more than ten categories, resulting in considerable classification, storage management, and use costs; The problem of uneven light emission among LED components in each string causes some strings to be dimmer than other strings. Therefore, for large-size displays, it is even necessary to consider each LED element in each string of LED components All belong to the same category.

At present, another known technology, as shown in Figure 5, is to use a higher DC voltage Vcc to drive, and to provide a current source Is to confirm that the forward current If flowing through the series-connected LED components has indeed reached a predetermined level. flow. If the Vf distribution range of all LED elements 10 in the LED assembly is 3.0V-4.0V when they leave the factory, then the highest voltage requirement of 4V shall be taken as the standard, multiplied by 30 elements to be driven, and a DC voltage above 120V shall be provided. Source Vcc, add the voltage drop of the calculated current source Is, so that the actual required Vcc will be raised to about 122V. The current source Is is used to provide a current If value significantly exceeding the highest demand to ensure that the series-connected LED assembly is lit as expected. However, using this method has the following disadvantages:

1. The efficiency of power supply is low: because the electric energy exceeding the actual demand cannot correspond to drive the LED components to emit higher brightness light, so when the actual light emission is equal to the serial LED components classified according to the voltage in the previous example, the previous classification method will only It needs to consume about 87% of the electric energy of this method;

2. Using the combination of a current source with a fixed output current and a power supply with a higher voltage deliberately applied, according to the above calculation, in order to drive 100 strings of LEDs, a display must provide 100 current sources Is with high voltage resistance, and the manufacturing cost will be reduced. increase;

3. If the backlight panel is composed of RGB three-color chips, the number and cost of high-voltage current sources need to be increased by three times.

Therefore, the present invention provides a plurality of series-connected LED components, which increases the number and controls the number of series connections so that it does not need to distinguish the forward bias voltage when the normal driving current is applied, and still meets the average level. On the one hand, it eliminates the need for precise classification of LED components, reducing unnecessary classification and management costs; on the other hand, only high-voltage low-current sources need to be used, and there is no need to deliberately select high-voltage current sources that can control the current value, further reducing manufacturing costs, especially It can be matched with the applicant's light uniformity technology, so that the luminous brightness between each string of LED components and between the particles in the series of LED components is not uniform, which can be completely covered and not obvious, greatly reducing the backlight when manufacturing displays In order to achieve the dual effect of the lowest cost and the highest power usage efficiency.

【Content of invention】

The object of the present invention is to provide a backlight panel with series-connected LED components, which uses a sufficient number of LED components to be connected in series, so that when the series-connected series is fed with a driving current, the driving voltage is substantially equal to that of the entire batch of LED components. The component average is multiplied by the particle count to eliminate the need for fine sorting of LEDs.

The second object of the present invention is to provide a backlight panel with series-connected LED components, which uses a sufficient number of LED components to be connected in series, so that the driving voltage required by the series after series connection meets expectations, so as to eliminate high-priced fixed components. Current value current source demand.

Another object of the present invention is to provide a display with series-connected LED components, in which the backlight is connected in series with a sufficient number of LED components, so that when the series-connected series is fed with a driving current, the driving voltage is substantially It meets the average value of the entire batch of LED components multiplied by the number of particles, so as to eliminate the need for precise classification of LED components; and makes the driving voltage required for the serial connection meet expectations, so as to eliminate the need for high-priced fixed current value current sources. Thereby greatly reducing the manufacturing cost.

Another object of the present invention is to provide a display with series-connected LED components, which utilizes the front and rear reflectors to homogenize the light emitted by the series-connected LED components in the backlight plate for multiple reflections between the front and rear reflectors, and only Part of the light is emitted from the front reflector, so that the light source is completely uniformed, and the uneven light emission of the LED components connected in series is further covered, thereby allowing the screening threshold of LED components to be greatly reduced.

Another object of the present invention is to provide a method for manufacturing a backlight panel with series-connected LED components that eliminates the need for precise sorting of LED components, thereby greatly reducing manufacturing costs.

Yet another object of the present invention is to provide a series-connected device that utilizes the front and rear reflectors to make the light emitted by the series-connected LED components reflect and homogenize multiple times between the front and rear reflectors, so as to cover the uneven light emission of the series-connected LED components. Manufacturing method of backlight panel of LED module.

The backlight panel with series-connected LED components, the manufacturing method and the display with the backlight panel to achieve the above-mentioned purpose of the invention mainly include a set of energy supply devices, at least two groups are connected in parallel with each other, and are jointly enabled by the energy supply device to emit light, and respectively include A serial connection LED assembly of a plurality of LED elements connected in series and a group of liquid crystal modules. Wherein the energy supply device provides power to the serial connection LED assembly and the liquid crystal module, the series connection LED assembly is provided by the power supply device, and the number of the above-mentioned series connection LEDs is such that when the at least two groups of series connection LEDs When the component is lit, the difference between the enabling voltage of any one of the at least two series-connected LED components minus the product of the average enabling voltage of the above-mentioned LED elements in the component and the number of LEDs in the component is less than the The product of the statistical standard deviation of the individual enabling voltages of the above-mentioned LED elements in the assembly and the number of the above-mentioned LED elements in the assembly reaches a predetermined multiple; thereby, the individual differences of the above-mentioned LED elements affect the enabling voltage provided by the energy supply device The degree of influence is reduced by this predetermined factor. The liquid crystal module is powered by the power supply device to display images, and is used as a backlight for the liquid crystal module by being connected in series with LED components; and the backlight board can be used with a set of uniform light devices , the dodging device mainly includes a dodging sheet, a front reflector and a rear reflector, the front reflector is arranged between the dodging sheet and the at least two groups of LED components connected in series, and the rear reflector is arranged on The at least two groups of series-connected LED components are away from the side of the dodging sheet, wherein the reflectivity of the rear reflector is close to complete reflection, and the reflectivity of the front reflector is higher than its transmittance but less than the reflection of the rear reflector The uniform light device can pass through the different reflectivity of the front reflector and the rear reflector, and can increase the illumination rate of the light source of the series-connected LED components, so as to achieve the purpose of effective use of power and uniformity of the light source.

[Simple description of the diagram]

FIG. 1 is a schematic diagram of a known number of series-connected LED elements being driven to light by a single DC power supply;

Fig. 2 is the probability distribution diagram of the forward drive voltage _Vf value of known LED element under 20mA drive current;

Figure 3 is a graph of the I-V relationship of a general LED component;

Fig. 4 is a graph showing the relationship between the current I _f and the luminous brightness B of a general LED element being activated and lit;

FIG. 5 is a schematic diagram of a conventional current source Is used to enable LEDs connected in series to be turned on, illustrating that the supplied voltage Vcc must exceed the maximum required voltage of a single LED multiplied by the number of LEDs connected in series;

Fig. 6 is the structural block of the first preferred embodiment of the backlight panel with LED components connected in series in the present invention

picture;

Fig. 7 is a schematic structural view of the embodiment of Fig. 6;

Fig. 8 is a probability distribution curve of the total forward bias voltage VfT of the series-connected LED components used in the embodiment of Fig. 6 at a driving current of 20mA;

Fig. 9 is a schematic diagram of the arrangement of multiple groups of series-connected LED components on the backlight board of the embodiment in Fig. 6;

Fig. 10 is a distribution diagram of the total forward bias I-V relationship curve of each series-connected LED assembly in the embodiment of Fig. 6 under a driving current of 20mA;

Fig. 11 is a schematic diagram of the backlight circuit of the embodiment in Fig. 6, illustrating the relationship between the energy supply device and the circuit of each series-connected LED assembly;

Fig. 12 is a graph showing the relationship between the respective flowing current I and the total forward bias voltage V _fT when the same forward voltage Vcc is applied to each group of series-connected LED components in Fig. 11;

FIG. 13 is a graph showing the relationship between the luminous brightness and the current IV-If of the embodiment of FIG. 6, illustrating the control mode for adjusting the brightness of the backlight panel;

FIG. 14 is a schematic diagram of reversed series arrangement of each series-connected LED components in the second preferred embodiment of the backlight panel with series-connected LED components of the present invention; and

FIG. 15 is a schematic structural diagram of the first preferred embodiment of the display of the present invention, illustrating the structural relationship between the light homogenizing device and the backlight plate.

[Description of main component symbols]

10 LED components 12 DC power supply 30 Backlight board

32 Energy supply device 34, 34’ LED components connected in series

340, 340’ LED components 36, 36’ LCD modules

38’ Evening device 382’ Front reflector

384’ rear reflector 386’ dodging film

【Detailed ways】

Figure 6 is a block diagram of the backlight structure of the present invention with series-connected LED components, which mainly includes: a backlight 30 and a liquid crystal module 36; Connect the LED assembly 34.

Among them, the energy supply device 32 is used to provide, for example, two strings of parallel connected LED components 34 and liquid crystal module 36 energy; and as shown in FIG. LED elements 340, and the light-emitting sides of each LED element 340 are arranged in the same direction; the liquid crystal module 36 is arranged corresponding to the at least two series-connected LED assemblies 34, and is illuminated by the above-mentioned series-connected LED assemblies 34 in a backlight manner.

The IV curve of a typical LED component is generally that the higher the V _f value, the greater the current I _f . For the same LED component, the relationship between the current I _f and the luminous brightness B, after exceeding the basic driving current, the luminous brightness increases with the current The value increases roughly linearly. However, with the slight difference in various conditions in the manufacturing process, even if the LED components manufactured by the same company, or even the components packaged by LED chips cut out of the same wafer, the IV curves of each chip are also different from each other. difference. Therefore, if N LED components manufactured in the same batch are connected in series, the total forward bias voltage V _f (T) of the total series connection under the forward current I _f = V _f (1) + V _f (2) + ....V _f (N), as shown in Figure 8, according to the mathematical theory of Normal Distribution, the probability distribution function P(V _fT ) of the forward bias voltage V _fT after series connection can be written as:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; .</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}}\mathrm{<span\; class="notranslate">\; e</span>}\frac{<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; vT</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

where V _avT =NxVa...(3)

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Delta;N</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

相较于图2所示的机率分布图P(V_f)，个别LED元件的平均正向偏压为3.5V，标准差为0.2V；可以发现，串联后整串LED组件的正向偏压理论值(V_fT)_av＝350V，仍为个别元件理论值乘以串联元件数目；但相对地，串联后LED组件的正向偏压标准差ΔV_T＝2.0V，明显比应有的0.2V×100的数值遽减，亦即，虽然依照本发明揭示的串列LED组件，在制造前并没有先经过LED元件的分类流程，而其正向偏压的总和分布范围仍比原先单颗时的分布比例明显缩窄。由以上公式可以得出，如果有N颗LED元件串联，其分布范围将可缩小为原来范围的

倍，也就是串接100颗未经分类的LED元件，可将串列组件的正向偏压值缩为原先理论值与串列数目乘积的十分之一。例如第一较佳实施例有400颗LED元件串联，则其V_f之分布范围将可缩小为原来的

The distribution of LED components in the above example is taken as an example. If 100 LED components are connected in series, the theoretical value of the total forward bias voltage V _fT is shown in formula (3) as (V _fT )av=100×3.5=350V , and its standard deviation:

Compared with the probability distribution diagram P(V _f ) shown in Figure 2, the average forward bias voltage of individual LED components is 3.5V, and the standard deviation is 0.2V; it can be found that the forward bias voltage of the entire string of LED components after series connection The theoretical value (V _fT ) _av = 350V is still the theoretical value of individual components multiplied by the number of series components; but relatively, the standard deviation of the forward bias voltage of the LED components after series connection ΔV _T = 2.0V, significantly higher than the 0.2V that should be The value of ×100 is reduced sharply, that is, although the tandem LED assembly disclosed by the present invention does not go through the classification process of LED elements before manufacturing, the total distribution range of the forward bias voltage is still larger than that of the original single LED assembly. The proportion of the distribution narrowed significantly. It can be concluded from the above formula that if there are N LED components connected in series, the distribution range will be reduced to the original range.

times, that is, connecting 100 unclassified LED components in series can reduce the forward bias value of the series components to one-tenth of the product of the original theoretical value and the number of series. For example, if there are 400 LED components connected in series in the first preferred embodiment, the distribution range of its V _f will be reduced to the original

Even with four times the standard deviation as the boundary, the minimum value of V _fT is about 350-(4x2.0)=342V, and the maximum value is about 350+(4×2.0)=358V. The forward bias voltage between multiple strings of LED components The gap, at most, is only 358V-342V=16V, which is still narrowed compared to the dispersion of the original unclassified single LED components; however, four times the standard deviation means that 99% of all produced tandem LED components All of the above are within this range, especially when the number of LED elements in series increases, the concentration of the positive phase bias voltage of the entire string of LED components can be more obvious.

Utilize the above principle, the second preferred embodiment of the present invention will take the backlight plate of a 42 o'clock LCD TV as an example, and calculate the actual situation: here, the brightness of its backlight plate is determined to be 6000cd/m ² , and the area of the backlight plate It is about 0.54m ² , so the total brightness of the required LEDs is 3200cd. When the average brightness of each white LED element is 1cd under the forward current I _f =20mA, the number of white LEDs required by the backlight panel 3200 pieces.

Considering that the cost of a general high-voltage and low-current power supply is lower than that of a high-voltage, high-current power supply, the cost of a 5V, 80A power supply for the same 400W power supply will be much higher than that of a 1000V, 0.4A power supply. Because the current high-voltage low-current power supply has been widely used in the backlight board of the original CCFL cold-cathode tube. Therefore, in the present invention, an inverter (Inverter) of a general cold-cathode tube is also used as a power source for illustration, but the present invention does not limit the use of other power sources. CCFL Inverter is a high-voltage high-frequency AC power supply, so a bridge rectifier and filter capacitor must be added to the output to become a high-voltage DC power supply. However, other general high-voltage DC power supplies use DC-DC conversion circuits to convert a low-voltage DC power supply into high-voltage DC using a Buck.Converter circuit.

In this example, it needs to use 3,200 white LEDs. Through the above-mentioned principle, the more LEDs are used in series, the variation range of the total forward bias voltage can be reduced. Therefore, in this example, as shown in Figure 9 , choose 400 LED components connected in series as an example, in which each string of LED components has 400 LED components, and the light source in the backlight panel is composed of 8 strings of LED components such as ST1, ST2, ... ST8.

If the average forward voltage of each single white LED element (at the current If=20mA) is 3.5V, and the forward bias voltage distribution range of a single LED is 3.0V ~ 4.0V, then 400 LEDs are connected in series to form an LED After assembly, the theoretical value of the total forward voltage required by each assembly is 1400V, and the distribution range of the total forward bias voltage of the series LED assembly is shown in Figure 10, which will be limited to 1390V-1410V.

As shown in Figure 11, the positive poles of the eight groups of series-connected LED components 34' are completely paralleled to the power supply Vcc with a voltage of 1400v, and the ground terminals of each series-connected LED component 34' are also connected in parallel to a 10Ω resistor Rs as the operating current. The back-up voltage Vs of IT, and the adjustment voltage control of the power supply Vcc. Since the DC power supply Vcc is selected as 1400V, the possible distribution range is compared with the ideal total forward bias value, and the error is only within 1%, because the forward voltage difference between the LED components of each string is very small, the following will be calculated to prove Even if the eight serial LED assemblies 34' are used completely in parallel, only a single energy supply device is used to enable it, and the same voltage Vcc is applied to the above serial LED assemblies 34', the difference in luminous intensity between each serial LED assembly 34' is the same. Extremely limited and cannot be easily observed.

Due to the total forward bias value VT(I)=V1(I)+V2(I)+----V400(I) of each string of LED components, and the I-V curves of each LED component are different, so that the drive When the current is fixed, the actual total forward bias voltage of each string of LED components is different. On the contrary, if the common forward voltage Vcc is chosen to be fixed at 1400V, the relation curve between the total forward bias voltage VT(I) and the current I of each string of LED components is shown in FIG. 12 .

相对地正向电流20mA时总偏压为1390V的该组LED组件，在Vcc＝1400V时的正向电流I_f为

Among them, when the fixed current is 20mA, the total bias voltage of this string of LED components needs to be 1410V, and the forward current I _f at Vcc=1400V will be roughly estimated as

For this group of LED components with a total bias voltage of 1390V when the forward current is 20mA, the forward current If at Vcc=1400V _is

It can be seen that according to the manufacturing method of the present invention, even if LED elements 340 ′ that are not carefully selected and classified are connected in series in the first step, when the number of LED elements to be connected in series is large enough, at least Two sets of series-connected LED components 34' are connected in parallel and enabled by a single set of power supply Vcc. The drive current of each series-connected LED component 34' is quite close to the originally predetermined ideal drive current If=20mA and the total operating current flowing through Rs can be determined. It is still quite close to the ideal value of 160mA (20mA×8), and the forward current difference among the series-connected LED assemblies 34' is also limited within 5%. Further, since the brightness of the LED is approximately proportional to the current, the average brightness difference of each series-connected LED assembly 34' is also within 5%.

Further, if you want to adjust the brightness of the backlight panel, you can adjust the Vcc voltage to, for example, 1300V (3.25V×400 LEDs), then the forward current If≈15mA of each series-connected LED assembly 34', using the luminous brightness and From the current IV-If relationship diagram, it can be seen that the luminous brightness B is about 75% of the aforementioned 20mA. Therefore, as long as the voltage of Vcc is adjusted, the luminous brightness of each series-connected LED assembly 34' can be controlled. Since the eight strings of LED components are driven by the same forward current, the error of each other's forward bias voltage is only about 1%; therefore, when they are connected in parallel and driven by the same voltage, the error of individual forward current will also be limited to within 5%. .

As shown in the previous embodiment, when a string of LED components actually has 400 LED components connected in series, and the forward voltage across each LED component is about 3.5V, the potential difference across the string of LED components will reach 1400V. ; Once the engineer who designed the circuit did not check, and mistakenly folded the entire string of LED components into a "U" shape distribution design in a single turn, if the distance between the two ends is insufficient, the risk of direct short-circuit and tripping of the voltage at both ends of the LED component will be increased.

In order to improve safety, the present invention has a second preferred embodiment of a backlight panel with series-connected LED components. The LED distribution of the backlight panel will be arranged as shown in Figure 14, and ST1 is set at the uppermost part as shown in the figure and runs from Set ST2,...ST8 sequentially, and arrange 8 strings of LED components ST1, ST2,...ST8 with each string of LED components folded 80 times, so that each reversed arrangement will only connect 5 LED components in series. Therefore, the potential difference between the ends of the first and second arrays is only 35V. The series connection using this method can reduce the voltage difference between each LED and ensure the safety of wiring on the PCB.

Of course, as those familiar with the technical field can easily understand, although the above-mentioned embodiments all take white LED elements as an example, it is also possible to use RGB three-color LED elements to form an LED backlight panel. The forward bias voltages of LED components of different colors are not the same, so the LED components of each color must form multiple strings and be driven with different voltages according to their colors. For example, a 42-hour backlight panel in the above example requires 3,200 sets of R, G, and B LED components to form together, and if each 400 LED components are connected in series to form a string of single-color LED components, each color LED component requires 8 8 strings of LEDs of the same color can be supplied by the same high-voltage DC power supply, so three different voltage power supplies are required. When the color temperature needs to be adjusted, the three power supply voltages of VccR, VccG, and VccB can also be adjusted. The different supply currents for red, green and blue are adjusted individually, thus producing the desired brightness ratio to achieve any desired color temperature.

In-depth discussion, due to the difference in the manufacturing process of LED components, although each LED component is driven by the same current, the difference in output brightness may reach ±20%. In order to achieve the most economical structure and reduce the need for sorting and screening, it is necessary to even out the difference in brightness so that the viewer cannot immediately notice the difference in brightness between the LED elements.

Therefore, when the above-mentioned backlight plate disclosed by the present invention is used to form a display, the preferred embodiment of the display in this case is shown in FIG. The uniform light device 38' of the embodiment includes two reflectors with different reflectivity, the front and the rear, which are illustrated as the front reflector and the rear reflector 382', 384' in this example, and the reflectivity planning of the rear reflector 384' It is 100% completely reflective and only the front reflector 382' is partially transmissive. Thus, no matter whether the light emitted by the LED element 340' is irradiated on the front reflector 382' or the rear reflector 384', it is roughly reflected, and constantly goes back and forth between the two reflectors, and finally passes through the front reflector 382'. through the place, and then homogenized by the dodging sheet 386', and finally irradiated to the liquid crystal module 36'. In this way, a highly reflective partially transmissive reflective sheet is used to form a multi-reflective optical resonant cavity with the total reflective sheet on the bottom surface, so as to increase the uniformity of the light emitted by the series-connected LED assembly 34'.

Using this technology, if the partial reflection film (Partial Transmission Films) with 10% transmission and 90% reflection is used as the material of the front reflector, the uniformity of the LED element can be increased by 10 times according to the experimental results. That is to say, even if there is a difference of ±20% in luminous brightness between the original LED components, after this structure is homogenized, the unevenness remains at most ±2%. The difference in luminance between modules is less than 5%. Thereby, the advantage of not needing to classify the LED components is brought into full play to the extreme, and the problem of non-uniform luminous brightness of the non-classified LED components is covered up to the point where it is difficult to observe.

It can be seen from the above description that using multiple LED elements in series can not only reduce the difference in forward bias voltage among the series-connected LED components, but also allow multiple strings of LED components with the same function to be connected in parallel to be driven by a group of power sources. Moreover, the screening thresholds of the forward voltage and brightness difference of each LED element can be greatly reduced, thereby greatly reducing the manufacturing cost, and making a very economical backlight panel. Certainly, if the number of series-connected LEDs can be easily understood by those skilled in the art, as long as it reaches 36 for example, the deviation value of the total forward bias voltage of the series-connected LED components can be compared with the deviation value of a single LED element and that of an LED. The product of the total number of components is reduced by six times, so that, for example, a 12-inch panel can be connected in parallel using, for example, two sets of low-cost series-connected LED components.

But what is described above is only a preferred embodiment of the present invention, and should not limit the scope of the present invention, that is, all simple equivalent changes and modifications made according to the scope of the claims of the present invention and the contents of the description of the invention are all Still belong to the scope that the patent of the present invention covers.

Claims (13)

1. A backlight panel with serially connected LED assemblies, characterized in that, comprising: a set of energy supply units; and At least two groups of series-connected LED assemblies that are connected in parallel with each other, are jointly enabled to emit light by the energy supply device, and respectively include a plurality of LED elements connected in series with each other, the number of the above-mentioned series-connected LEDs is such that When being lit, the difference between the enabling voltage of any one of the at least two groups of series-connected LED components minus the product of the average enabling voltage of the above-mentioned LED elements in the component and the number of LEDs in the component is less than that in the component The product of the statistical standard deviation of the individual enabling voltage of the above-mentioned LED elements and the number of the above-mentioned LED elements in the assembly reaches a predetermined multiple; thereby, the individual differences of the above-mentioned LED elements affect the effect of the enabling voltage provided by the energy supply device degree, is reduced by the predetermined multiple. 2. The backlight panel as claimed in claim 1, wherein the difference is less than one-sixth of the product of the standard deviation and the number of LED elements in the assembly. 3. The backlight panel as claimed in claim 1, wherein the difference is less than one-tenth of the product of the standard deviation and the number of LED elements in the assembly. 4. The backlight panel according to claim 1, wherein the light-emitting sides of the above-mentioned LED elements in the at least two series-connected LED assemblies are all arranged facing the same direction. 5. The backlight panel according to claim 1, 2, 3 or 4, further comprising a set of uniform light devices. 6. The backlight panel according to claim 5, wherein the group of homogenizing devices comprises: a homogeneous film; A set of front reflectors respectively arranged between the dodging sheet and the at least two groups of series-connected LED components, and a rear reflector arranged on the side of the at least two groups of series-connected LED components away from the light dosing sheet; Wherein the reflectivity of the rear reflector is close to complete reflection, and the reflectivity of the front reflector is higher than the transmittance but smaller than the reflectivity of the rear reflector. 7. A display with a serially connected LED assembly backlight, characterized in that it comprises: A set of backlight boards with LED assemblies connected in series, including: a set of energy supply units; and At least two groups of series-connected LED assemblies that are connected in parallel with each other, are jointly enabled to emit light by the energy supply device, and respectively include a plurality of LED elements connected in series with each other, the number of the above-mentioned series-connected LEDs is such that When being lit, the enabling voltage of the at least two series-connected LED components minus the difference between the product of the average enabling voltage of the above-mentioned LEDs in the component and the number of LEDs in the component is less than the above-mentioned LEDs in the at least two components The product of the statistical standard deviation of the enabling voltage and the number of LEDs in the component reaches a predetermined multiple; thereby, the degree to which the individual differences of the LEDs affect the enabling voltage provided by the energy supply device is reduced according to the predetermined multiples; and One group corresponds to at least two groups of liquid crystal modules arranged in series with LED components. 8 . The display according to claim 7 , wherein the light emitting directions of the at least two series-connected LED assemblies are set to face the liquid crystal module. 9. The display as claimed in claim 7, wherein the difference is less than one-tenth of the product of the standard deviation and the number of LEDs in the component. 10. The display according to claim 7, 8 or 9, wherein the backlight further comprises a set of uniform light devices. 11. The display device according to claim 10, wherein the group of dodging devices comprises: a homogeneous film; A set of front reflectors respectively arranged between the dodging sheet and the at least two groups of series-connected LED components, and a rear reflector arranged on the side of the at least two groups of series-connected LED components away from the light dosing sheet; Wherein the reflectivity of the rear reflector is close to complete reflection, and the reflectivity of the front reflector is higher than the transmittance but smaller than the reflectivity of the rear reflector. 12. A method for manufacturing a backlight panel with series-connected LED assemblies, comprising the following steps: a) planning at least two groups of series-connected LED assemblies each comprising a plurality of LED elements connected in series with each other; and b) providing an energy supply device for enabling and lighting the at least two groups of series-connected LED components in parallel; Wherein, the number of LEDs connected in series is such that when the at least one group of LED components connected in series is turned on, the entire string enabling voltage of any one of the at least two groups of LED components connected in series minus the above-mentioned LED elements in the component The difference between the product of the average enabling voltage and the number of LEDs in the assembly is smaller than the product of the statistical standard deviation of the individual enabling voltages of the LED elements in the assembly and the number of the LED elements in the assembly by a predetermined multiple; thereby, the above Individual differences of LED elements affect the enabling voltage provided by the energy supply device by reducing the predetermined factor. 13. The method for manufacturing a backlight panel with series-connected LED assemblies as claimed in claim 12, further comprising the step c) of setting a group of uniform light devices, wherein the group of uniform light devices includes: a homogeneous film; A set of front reflectors respectively arranged between the dodging sheet and the at least two groups of series-connected LED components, and a rear reflector arranged on the side of the at least two groups of series-connected LED components away from the light dosing sheet; Wherein the reflectivity of the rear reflector is close to complete reflection, and the reflectivity of the front reflector is higher than the transmittance but smaller than the reflectivity of the rear reflector.

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