TWI409765B

TWI409765B - Driving circuit for backlight system

Info

Publication number: TWI409765B
Application number: TW97139876A
Authority: TW
Inventors: Chien Yang Chen; Chi Hsiu Lin; Chao Wei Wei
Original assignee: Chunghwa Picture Tubes Ltd
Priority date: 2008-10-17
Filing date: 2008-10-17
Publication date: 2013-09-21
Also published as: TW201017620A

Abstract

A driving circuit for a backlight system is disclosed. The backlight system includes a plurality of backlight sources. The driving circuit includes a DC/AC inverter, a plurality of transformers, a plurality of impedance circuits and a controller. The DC/AC inverter is utilized for converting a DC signal to an AC signal. The plurality of transformers are utilized for boosting voltage of the AC signal to generate a plurality of driving currents. Each of the plurality of impedance circuits, individually coupled in parallel to the plurality of transformers and the plurality of backlight sources, has a frequency-dependent impedance, and is utilized for controlling whether to bypass the plurality of driving currents according to frequency of the AC signal. The controller is coupled to the DC/AC inverter, and is utilized for adjusting the frequency of the AC signal.

Description

背光系統之驅動電路Driving circuit of backlight system

本發明係指一種背光系統之驅動電路，尤指一種用於掃描式背光系統之驅動電路。The invention relates to a driving circuit of a backlight system, in particular to a driving circuit for a scanning backlight system.

由於傳統液晶顯示器係採用整面式點亮的背光源系統，亦即每支燈管的亮度保持固定且不會隨著時間而有所變動，因此在顯示時容易有動態殘影(Motion Blur)現象產生。有鑑於此，習知技術模擬陰極射線管(Cathode Ray Tube，CRT)顯示器之脈衝式(Impulse Type)發光原理，而發展出採輪流方式點亮冷陰極螢光燈管(Cold Cathode Fluorescent Lamp，CCFL)背光源之掃描式背光源(Scanning Backlight)技術，以藉由無發光的暗態區域來遮蔽液晶顯示器所產生的殘影影像，改善液晶顯示器之動態畫面影像品質。Since the conventional liquid crystal display adopts a full-surface lighting backlight system, that is, the brightness of each of the lamps remains fixed and does not change with time, it is easy to have dynamic image blur during display (Motion Blur) The phenomenon occurs. In view of this, the conventional technology simulates the principle of impulsive type of cathode ray tube (CRT) display, and develops a cold cathode fluorescent lamp (Cold Cathode Fluorescent Lamp, CCFL). The scanning source of the backlight (Scanning Backlight) technology is used to shield the image of the afterimage generated by the liquid crystal display by the dark region without light, thereby improving the dynamic image quality of the liquid crystal display.

請參考第1圖，第1圖為習知掃描式背光液晶顯示器之示意圖。如第1圖所示，液晶顯示面板110包含有掃描區塊BLK_1~BLK_n，而每一個掃描區塊係於點亮一相對應燈管120時進行顯像。大致來說，習知掃描式背光液晶顯示器係藉由輪流點亮燈管120的方式進行驅動，以顯示相對應掃描區塊之影像，其相關驅動訊號之時序如第2圖所示。因此，對於每一個掃描區塊而言，其顯示方式相當於***一黑畫面，因而可改善動態殘影的現象。Please refer to FIG. 1 , which is a schematic diagram of a conventional scanning type backlit liquid crystal display. As shown in FIG. 1, the liquid crystal display panel 110 includes scanning blocks BLK_1 BLBLK_n, and each scanning block is developed when a corresponding lamp tube 120 is lit. Generally speaking, the conventional scanning type backlit liquid crystal display is driven by rotating the lamp tube 120 in turn to display the image of the corresponding scanning block, and the timing of the relevant driving signal is as shown in FIG. Therefore, for each scanning block, its display mode is equivalent to inserting a black picture, thereby improving the phenomenon of dynamic image sticking.

然而，在習知多燈管之掃描式背光系統中，每一掃描區塊(即一個相位)通常需要一直交流換流器(DC/AC Inverter)進行驅動，以達到藉由掃描方式驅動背光源的目的。例如，美國專利第US6778415所揭露之一掃描式背光系統驅動架構，其需要N組直交流換流器與控制迴路，來驅動N個掃描區塊，以達到N組相位之分時掃描控制。因此，雖然掃描式背光系統可改善動態殘影的現象，卻具有電路架構複雜且電路成本高的缺點。However, in a conventional multi-lamp scanning backlight system, each scanning block (ie, one phase) usually needs to be driven by a DC/AC Inverter to drive the backlight by scanning. purpose. For example, U.S. Patent No. 6,779,415 discloses a scanning backlight system drive architecture that requires N sets of direct AC inverters and control loops to drive N scan blocks to achieve N sets of phase time division scan control. Therefore, although the scanning backlight system can improve the phenomenon of dynamic image sticking, it has the disadvantages of complicated circuit structure and high circuit cost.

因此，本發明之目的即在於提供一種用於一掃描式背光系統之驅動電路。Accordingly, it is an object of the present invention to provide a drive circuit for a scanning backlight system.

本發明係揭露一種背光系統之驅動電路。該背光系統包含有複數個背光源。該驅動電路包含有一直交流換流器、複數個變壓器、複數個阻抗電路及一控制器。該直交流換流器用來根據一切換控制訊號，將一直流訊號轉換成一交流訊號。每一該些變壓器電性連接於該直交流換流器與對應之該背光源之間，用來對該交流訊號進行升壓，以產生一驅動電流至該相對應背光源。每一該些阻抗電路具有隨頻率變化之一特性阻抗，且以並聯方式電性連接於對應之該變壓器及該背光源，用來根據該交流訊號之頻率，控制是否旁通(Bypassing)該相對應變壓器所產生之該驅動電流。該控制器電性連接於該直交流換流器，用來產生該切換控制訊號，並根據一頻率控制訊號，調整該切換控制訊號之工作頻率，以控制該交流訊號之頻率。The invention discloses a driving circuit of a backlight system. The backlight system includes a plurality of backlights. The driving circuit comprises a constant AC converter, a plurality of transformers, a plurality of impedance circuits and a controller. The direct current converter is configured to convert the direct current signal into an alternating current signal according to a switching control signal. Each of the transformers is electrically connected between the direct current converter and the corresponding backlight to boost the alternating current signal to generate a driving current to the corresponding backlight. Each of the impedance circuits has a characteristic impedance that varies with frequency, and is electrically connected in parallel to the corresponding transformer and the backlight to control whether to bypass the phase according to the frequency of the AC signal. Corresponding to the drive current generated by the transformer. The controller is electrically connected to the direct current converter for generating the switching control signal And adjusting the operating frequency of the switching control signal according to a frequency control signal to control the frequency of the alternating signal.

在說明書及後續的申請專利範圍當中使用了某些詞彙來指稱特定的元件。所屬領域中具有通常知識者應可理解，製造商可能會用不同的名詞來稱呼同樣的元件。本說明書及後續的申請專利範圍並不以名稱的差異來作為區別元件的方式，而是以元件在功能上的差異來作為區別的基準。在通篇說明書及後續的請求項當中所提及的「包含」係為一開放式的用語，故應解釋成「包含但不限定於」。此外，「電性連接」一詞在此係包含任何直接及間接的電氣連接手段。因此，若文中描述一第一裝置電性連接於一第二裝置，則代表該第一裝置可直接連接於該第二裝置，或透過其他裝置或連接手段間接地連接至該第二裝置。Certain terms are used throughout the description and following claims to refer to particular elements. It should be understood by those of ordinary skill in the art that manufacturers may refer to the same elements by different nouns. The scope of this specification and the subsequent patent application do not use the difference of the names as the means for distinguishing the elements, but the differences in the functions of the elements as the basis for the distinction. The term "including" as used throughout the specification and subsequent claims is an open term and should be interpreted as "including but not limited to". In addition, the term "electrical connection" is used herein to include any direct and indirect electrical connection. Therefore, if a first device is electrically connected to a second device, it means that the first device can be directly connected to the second device or indirectly connected to the second device through other devices or connection means.

請參考第3圖，第3圖為本發明實施例用於掃描式背光系統之一驅動電路30之示意圖。驅動電路30係用來驅動掃描式背光系統中之冷陰極螢光燈管(Cold Cathode Fluorescent Lamp，CCFL)背光源Lamp_1~Lamp_n，其包含有一直交流換流器(DC/AC Inverter)31、變壓器Trans_1~Trans_n、阻抗電路Imp_1~Imp_n及控制器32。直交流換流器31用來根據一切換控制訊號SW1，將一直流訊號Vin轉換成一交流訊號V_AC 。變壓器Trans_1~Trans_n中之每一變壓器具有一初級線圈(Primary Winding)電性連接於直交流換流器31，及一次級線圈(Secondary Winding)電性連接於一相對應冷陰極螢光燈管背光源，用來對交流訊號V_AC 進行升壓，以分別產生驅動電流Io1~Ion至冷陰極螢光燈管背光源Lamp_1~Lamp_n。阻抗電路Imp_1~Imp_n中之每一阻抗電路分別具有隨頻率變化之特性阻抗Z1~Zn，以並聯方式電性連接於一相對應變壓器及一相對應冷陰極螢光燈管背光源，用來根據交流訊號V_AC 之頻率，控制是否旁通(Bypassing)變壓器所產生之驅動電流Io1~Ion。控制器32電性連接於直交流換流器31，用來產生切換控制訊號SW1，並根據一頻率控制訊號CTRL，調整切換控制訊號SW1之工作頻率，以控制交流訊號V_AC 之頻率。Please refer to FIG. 3, which is a schematic diagram of a driving circuit 30 for a scanning backlight system according to an embodiment of the present invention. The driving circuit 30 is used to drive a Cold Cathode Fluorescent Lamp (CCFL) backlight Lamp_1~Lamp_n in a scanning backlight system, which includes a DC/AC Inverter 31 and a transformer. Trans_1~Trans_n, impedance circuits Imp_1~Imp_n and controller 32. The direct current converter 31 is configured to convert the direct current signal Vin into an alternating current signal V _AC according to a switching control signal SW1. Each of the transformers Trans_1~Trans_n has a primary winding electrically connected to the direct current converter 31, and a secondary winding is electrically connected to a corresponding cold cathode fluorescent tube backlight. The source is used to boost the AC signal V _AC to generate the driving current Io1~Ion to the cold cathode fluorescent lamp backlights Lamp_1~Lamp_n, respectively. Each of the impedance circuits Imp_1~Imp_n has a characteristic impedance Z1~Zn which varies with frequency, and is electrically connected in parallel to a corresponding transformer and a corresponding cold cathode fluorescent lamp backlight for The frequency of the AC signal V _AC controls whether the drive current Io1~Ion generated by the Bypassing transformer is generated. The controller 32 is electrically connected to the DC inverter 31 for generating the switching control signal SW1, and adjusts the operating frequency of the switching control signal SW1 according to a frequency control signal CTRL to control the frequency of the AC signal V _AC .

此外，驅動電路30另可包含有一電流偵測電路33，電性連接於變壓器Trans_1~Trans_n之次級線圈及控制器32之間，用來根據變壓器所產生之驅動電流之大小，產生一回授訊號VFB。其中，電流偵測電路33係由整流器rect_1~rect_n及一濾波器34所組成。整流器rect_1~rect_n分別電性連接於變壓器Trans_1~Trans_n之次級線圈，用來對變壓器所產生之驅動電流進行整流；而濾波器34電性連接於整流器rect_1~rect_n，則用來對整流器rect_1~rect_n所產生之整流訊號進行濾波，以產生回授訊號VFB。In addition, the driving circuit 30 may further include a current detecting circuit 33 electrically connected between the secondary coils of the transformers Trans_1~Trans_n and the controller 32 for generating a feedback according to the magnitude of the driving current generated by the transformer. Signal VFB. The current detecting circuit 33 is composed of a rectifier rect_1~rect_n and a filter 34. The rectifiers rect_1~rect_n are respectively electrically connected to the secondary coils of the transformers Trans_1~Trans_n for rectifying the driving current generated by the transformer; and the filter 34 is electrically connected to the rectifiers rect_1~rect_n, and is used for the rectifier rect_1~ The rectified signal generated by rect_n is filtered to generate a feedback signal VFB.

在此情形下，控制器32另可根據回授訊號VFB，調整切換控制訊號SW1之工作頻率，以控制調整交流訊號V_AC 之振幅。關於直交流換流器31及控制器32之詳細運作方式，例如根據切換控制訊號SW1之工作頻率，控制直交流換流器31內部之功率電晶體開關等等，其係本領域具通常知識者所知，於此不贅述。In this case, the controller 32 can further adjust the operating frequency of the switching control signal SW1 according to the feedback signal VFB to control the amplitude of the adjusted AC signal V _AC . Regarding the detailed operation mode of the DC converter 31 and the controller 32, for example, controlling the power transistor switch inside the DC converter 31 according to the operating frequency of the switching control signal SW1, etc., which is generally known in the art. As known, it will not be described here.

如此一來，本發明驅動電路30可藉由改變交流訊號V_AC 之頻率，控制是否透過阻抗電路Imp_1~Imp_n旁通變壓器所產生之驅動電流Io1~Ion，以分時點亮背光系統中之冷陰極螢光燈管背光源Lamp_1~Lamp_n，而達到以掃描方式驅動背光源的目的。相較於先前技術，本發明僅需使用一組直交流換流器，即可達成N組相位之分時掃描控制，因而具有電路架構簡單及可降低生產成本等優點。關於驅動電路30之詳細操作，請繼續參考以下說明。In this way, the driving circuit 30 of the present invention can control whether the driving current Io1~Ion generated by the impedance transformer Imp_1~Imp_n is passed through the impedance of the alternating current signal V _AC to lightly cool the backlight system in a time-sharing manner. The cathode fluorescent lamp backlights Lamp_1~Lamp_n achieve the purpose of driving the backlight in a scanning manner. Compared with the prior art, the present invention only needs to use a set of direct AC converters to achieve N-phase phase-timed scanning control, thereby having the advantages of simple circuit structure and reduced production cost. For detailed operation of the drive circuit 30, please continue to refer to the following description.

在本發明驅動電路30中，阻抗電路Imp_1~Imp_n較佳地可藉由諧振電路實現，特別是高品質因子之諧振電路，以使每一阻抗電路之特性阻抗於交流訊號V_AC 之頻率相同於一特徵頻率(或稱為共振頻率)時，提供遠大於冷陰極螢光燈管阻抗Z_L 之一最大阻抗值，而於交流訊號V_AC 之頻率相異於特徵頻率時，提供遠小於冷陰極螢光燈管阻抗Z_L 之一阻抗值。在此情形下，本發明可適當地設計每一阻抗電路之特徵頻率，以在不同操作頻率下迫使變壓器所產生之驅動電流Io1~Ion輸出至冷陰極螢光燈管背光源Lamp_1~Lamp_n，而達到分時驅動的目的。In the driving circuit 30 of the present invention, the impedance circuits Imp_1~Imp_n are preferably implemented by a resonant circuit, in particular a high quality factor resonant circuit, such that the impedance of each impedance circuit is equal to the frequency of the alternating current signal V _AC . A characteristic frequency (or resonant frequency) provides a maximum impedance value that is much greater than one of the cold cathode fluorescent tube impedances Z _L , and provides a much smaller temperature than the cold cathode when the frequency of the alternating current signal V _AC is different from the characteristic frequency. One of the impedance values of the fluorescent tube impedance Z _L . In this case, the present invention can appropriately design the characteristic frequency of each impedance circuit to force the driving currents Io1~Ion generated by the transformer to be output to the cold cathode fluorescent lamp backlights Lamp_1~Lamp_n at different operating frequencies. Achieve the purpose of time-sharing.

舉例來說，請參考第4圖，第4圖為說明了第3圖中阻抗電路Imp_1~Imp_n之頻率響應圖。其中，Z1~Zn分別代表阻抗電路Imp_1~Imp_n之特性阻抗，fr1~frn代表阻抗電路Imp_1~Imp_n之特徵頻率(或共振頻率)，而Z1_max~Zn_max則分別代表每一特性阻抗之最大值。如第4圖所示，每一阻抗電路之特徵頻率皆不相同，且每一阻抗電路之特性阻抗在其特徵頻率下具有遠大於冷陰極螢光燈管阻抗Z_L 之一最大阻抗值，而在相異於特徵頻率之其他頻率下則具有遠小於冷陰極螢光燈管阻抗Z_L 之一阻抗值。For example, please refer to FIG. 4, which is a diagram showing the frequency response of the impedance circuits Imp_1~Imp_n in FIG. Among them, Z1~Zn represent the characteristic impedances of the impedance circuits Imp_1~Imp_n, fr1~frn represent the characteristic frequencies (or resonance frequencies) of the impedance circuits Imp_1~Imp_n, and Z1_max~Zn_max represent the maximum values of each characteristic impedance, respectively. As shown in FIG. 4, the characteristic frequencies of each impedance circuit are different, and the characteristic impedance of each impedance circuit has a maximum impedance value at one of its characteristic frequencies that is much larger than the impedance of the cold cathode fluorescent tube Z _L . At other frequencies that differ from the characteristic frequency, there is an impedance value that is much less than the impedance of the cold cathode fluorescent tube Z _L .

因此，當交流訊號V_AC 之頻率操作於某一特徵頻率下時，例如特徵頻率fr_1，由於此時僅有阻抗電路Imp_1之特性阻抗遠大於冷陰極管阻抗Z_L ，因此阻抗電路Imp_1可迫使變壓器Trans_1所產生之驅動電流Io1輸出至冷陰極螢光燈管背光源Lamp_1，而點亮冷陰極螢光燈管背光源Lamp_1。相較之下，由於此時阻抗電路Imp_2~Imp_n之特性阻抗皆遠小於冷陰極管阻抗Z_L ，因此變壓器Trans_2~Trans_n所產生之驅動電流Io2~Ion將分別透過阻抗電路Imp_2~Imp_n旁通至一地端，而使冷陰極螢光燈管背光源Lamp_2~Lamp_n無法被點亮。Therefore, when the frequency of the AC signal V _AC operates at a certain characteristic frequency, for example, the characteristic frequency fr_1, since only the characteristic impedance of the impedance circuit Imp_1 is much larger than the cold cathode tube impedance Z _L at this time, the impedance circuit Imp_1 can force the transformer The driving current Io1 generated by Trans_1 is output to the cold cathode fluorescent lamp backlight Lamp_1, and the cold cathode fluorescent lamp backlight Lamp_1 is illuminated. In contrast, since the characteristic impedances of the impedance circuits Imp_2~Imp_n are far less than the cold cathode tube impedance Z _L , the driving currents Io2~Ion generated by the transformers Trans_2~Trans_n are respectively bypassed through the impedance circuits Imp_2~Imp_n to At the ground end, the cold cathode fluorescent lamp backlight Lamp_2~Lamp_n cannot be illuminated.

也就是說，當交流訊號V_AC 之頻率操作於特徵頻率fr_1時，背光系統中僅冷陰極螢光燈管背光源Lamp_1被點亮，而其餘燈管皆為熄滅狀態。同理，當交流訊號V_AC 之頻率操作於特徵頻率fr_2時，背光系統中僅冷陰極螢光燈管背光源Lamp_2被點亮而其餘燈管皆為熄滅狀態，以此類推。That is to say, when the frequency of the alternating signal V _AC is operated at the characteristic frequency fr_1, only the cold cathode fluorescent lamp backlight Lamp_1 is lit in the backlight system, and the remaining lamps are all turned off. Similarly, when the frequency of the AC signal V _AC is operated at the characteristic frequency fr_2, only the cold cathode fluorescent lamp backlight Lamp_2 is lit in the backlight system and the remaining lamps are turned off, and so on.

如此一來，本發明驅動電路可藉由改變交流訊號V_AC 之頻率，以掃描方式分時點亮背光系統中之冷陰極螢光燈管背光源Lamp_1~Lamp_n，從而改善液晶顯示器之動態殘影(Motion Blur)現象。In this way, the driving circuit of the present invention can improve the dynamic image sticking of the liquid crystal display by changing the frequency of the AC signal V _AC and scanning the cold cathode fluorescent lamp backlights Lamp_1~Lamp_n in the backlight system in a scanning manner. (Motion Blur) phenomenon.

值得注意的是，上述變壓器Trans_1~Trans_n除了用來對交流訊號V_AC 進行升壓之外，另可用來平衡其所產生之驅動電流之大小，其係本領域具通常知識者所熟知，於此不贅述。此外，整流器rect_1~rect_n之每一整流器係分別藉由一半波擷取電路實現，而濾波器34則藉由一電阻電容式低通濾波器實現，如第3圖所示。當然，本領域具通常知識者可根據實際需求做適當地修改，其亦屬本領域之範圍。It should be noted that the above-mentioned transformers Trans_1~Trans_n can be used to balance the driving current generated by the AC signal V _AC , which is well known to those skilled in the art. Do not repeat them. In addition, each of the rectifiers rect_1~rect_n is implemented by a half-wave extraction circuit, and the filter 34 is implemented by a resistor-capacitor low-pass filter, as shown in FIG. Of course, those skilled in the art can make appropriate modifications according to actual needs, which are also within the scope of the art.

綜上所述，本發明驅動電路係藉由變頻方式分時點亮背光系統中之冷陰極螢光燈管背光源，以改善液晶顯示器之動態殘影現象。相較於先前技術，本發明僅需使用一組直交流換流器，即可達成N組相位之分時掃描控制，因而具有電路架構簡單及可降低生產成本等優點。In summary, the driving circuit of the present invention illuminates the backlight of the cold cathode fluorescent lamp in the backlight system by frequency conversion to improve the dynamic image sticking phenomenon of the liquid crystal display. Compared with the prior art, the present invention only needs to use a set of direct AC converters to achieve N-phase phase-timed scanning control, thereby having the advantages of simple circuit structure and reduced production cost.

以上所述僅為本發明之較佳實施例，凡依本發明申請專利範圍所做之均等變化與修飾，皆應屬本發明之涵蓋範圍。The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

110‧‧‧液晶顯示面板110‧‧‧LCD panel

BLK_1~BLK_n‧‧‧掃描區塊BLK_1~BLK_n‧‧‧ scan block

120‧‧‧燈管120‧‧‧Light tube

30‧‧‧驅動電路30‧‧‧Drive circuit

Lamp_1~Lamp_n‧‧‧冷陰極螢光燈管背光源Lamp_1~Lamp_n‧‧‧Cold Cathode Fluorescent Lamp Backlight

31‧‧‧直交流換流器31‧‧‧Direct AC Converter

Trans_1~Trans_n‧‧‧變壓器Trans_1~Trans_n‧‧‧Transformer

Imp_1~Imp_n‧‧‧阻抗電路Imp_1~Imp_n‧‧‧impedance circuit

32‧‧‧控制器32‧‧‧ Controller

SW1‧‧‧切換控制訊號SW1‧‧‧Switching control signal

Vin‧‧‧直流訊號Vin‧‧‧DC signal

V_AC ‧‧‧交流訊號V _AC ‧‧‧ exchange signal

Io1~Ion‧‧‧驅動電流Io1~Ion‧‧‧ drive current

Z1~Zn‧‧‧特性阻抗Z1~Zn‧‧‧ characteristic impedance

CTRL‧‧‧頻率控制訊號CTRL‧‧‧ frequency control signal

33‧‧‧電流偵測電路33‧‧‧ Current detection circuit

rect_1~rect_n‧‧‧整流器Rect_1~rect_n‧‧‧Rectifier

Z_L1 ~Z_Ln ‧‧‧冷陰極螢光燈管阻抗Z _L1 ~Z _Ln ‧‧‧Cold Cathode Fluorescent Lamp Impedance

fr1~frn‧‧‧特徵頻率Fr1~frn‧‧‧Characteristic frequency

Z1_max~Zn_max‧‧‧特性阻抗之最大值Z1_max~Zn_max‧‧‧The maximum value of the characteristic impedance

34‧‧‧濾波器34‧‧‧ Filter

第1圖為習知掃描式背光液晶顯示器之示意圖。FIG. 1 is a schematic diagram of a conventional scanning type backlit liquid crystal display.

第2圖為習知掃描式背光系統之驅動訊號時序圖。FIG. 2 is a timing diagram of driving signals of a conventional scanning backlight system.

第3圖為本發明實施例用於掃描式背光系統之一驅動電路之示意圖。FIG. 3 is a schematic diagram of a driving circuit for a scanning backlight system according to an embodiment of the present invention.

第4圖為說明了第3圖中阻抗電路之頻率響應圖。Figure 4 is a diagram showing the frequency response of the impedance circuit in Figure 3.

30‧‧‧驅動電路30‧‧‧Drive circuit

31‧‧‧直交流換流器31‧‧‧Direct AC Converter

Trans_1~Trans_n‧‧‧變壓器Trans_1~Trans_n‧‧‧Transformer

Imp_1~Imp_n‧‧‧阻抗電路Imp_1~Imp_n‧‧‧impedance circuit

32‧‧‧控制器32‧‧‧ Controller

SW1‧‧‧切換控制訊號SW1‧‧‧Switching control signal

Vin‧‧‧直流訊號Vin‧‧‧DC signal

V_AC ‧‧‧交流訊號V _AC ‧‧‧ exchange signal

Io1~Ion‧‧‧驅動電流Io1~Ion‧‧‧ drive current

Z1~Zn‧‧‧特性阻抗Z1~Zn‧‧‧ characteristic impedance

CTRL‧‧‧頻率控制訊號CTRL‧‧‧ frequency control signal

33‧‧‧電流偵測電路33‧‧‧ Current detection circuit

rect_1~rect_n‧‧‧整流器Rect_1~rect_n‧‧‧Rectifier

fr1~frn‧‧‧特徵頻率Fr1~frn‧‧‧Characteristic frequency

34‧‧‧濾波器34‧‧‧ Filter

Claims

一種背光系統之驅動電路，該背光系統包含有複數個背光源，該驅動電路包含有：一直交流換流器(DC/AC Inverter)，用來根據一切換控制訊號，將一直流訊號轉換成一交流訊號；複數個變壓器，每一該些變壓器電性連接於該直交流換流器與對應之該背光源之間，用來對該交流訊號進行升壓，以產生一驅動電流至該相對應背光源；複數個阻抗電路，每一該些阻抗電路具有隨頻率變化之一特性阻抗，且以並聯方式電性連接於對應之該變壓器及該背光源，用來根據該交流訊號之頻率，控制是否旁通(Bypassing)該相對應變壓器所產生之該驅動電流；以及一控制器，電性連接於該直交流換流器，用來產生該切換控制訊號，並根據一頻率控制訊號，調整該切換控制訊號之工作頻率，以控制該交流訊號之頻率；其中每一該些阻抗電路之特性阻抗係於該交流訊號之頻率相同於一特徵頻率時，提供一最大阻抗值，該最大阻抗值遠大於該相對應背光源之阻抗，而於該交流訊號之頻率相異於該特徵頻率時，提供遠小於該相對應背光源之阻抗之一阻抗值。 A driving circuit for a backlight system, the backlight system comprising a plurality of backlights, the driving circuit comprising: a DC/AC Inverter for converting a DC signal into an AC according to a switching control signal a plurality of transformers, each of the transformers being electrically connected between the direct current converter and the corresponding backlight for boosting the alternating current signal to generate a driving current to the corresponding backlight a plurality of impedance circuits, each of the impedance circuits having a characteristic impedance that varies with frequency, and electrically connected in parallel to the corresponding transformer and the backlight for controlling whether the frequency of the AC signal is based on Bypassing the driving current generated by the corresponding transformer; and a controller electrically connected to the direct current converter for generating the switching control signal, and adjusting the switching according to a frequency control signal Controlling the operating frequency of the signal to control the frequency of the alternating signal; wherein the characteristic impedance of each of the impedance circuits is at a frequency of the alternating current signal Providing a maximum impedance value that is greater than the impedance of the corresponding backlight when the characteristic frequency is greater than the corresponding backlight when the frequency of the alternating signal is different from the characteristic frequency One of the impedance values of the impedance.

如請求項1所述之驅動電路，其中每一該些阻抗電路之特性阻抗皆不相同。 The driving circuit of claim 1, wherein each of the impedance circuits has a characteristic resistance Resistance is different.

如請求項1所述之驅動電路，其中每一該些阻抗電路係於該交流訊號之頻率相異於該特徵頻率時，旁通該相對應變壓器所產生之驅動電流至一地端。 The driving circuit of claim 1, wherein each of the impedance circuits bypasses a driving current generated by the corresponding transformer to a ground terminal when the frequency of the alternating current signal is different from the characteristic frequency.

如請求項1所述之驅動電路，其中每一該些阻抗電路係於該交流訊號之頻率相同於該特徵頻率時，使該相對應變壓器所產生之該驅動電流輸出至該相對應背光源，以點亮該相對應背光源。 The driving circuit of claim 1, wherein each of the impedance circuits outputs the driving current generated by the corresponding transformer to the corresponding backlight when the frequency of the alternating current signal is the same as the characteristic frequency. To illuminate the corresponding backlight.

如請求項1所述之驅動電路，其中每一該些阻抗電路包括一諧振電路。 The driving circuit of claim 1, wherein each of the impedance circuits comprises a resonant circuit.

如請求項1所述之驅動電路，其中該些變壓器另用來平衡所產生之複數個驅動電流之大小。 The driving circuit of claim 1, wherein the transformers are further used to balance the magnitude of the plurality of driving currents generated.

如請求項1所述之驅動電路，其中該控制器更可根據一回授訊號，調整該切換控制訊號之工作頻率，以控制該交流訊號之振幅。 The driving circuit of claim 1, wherein the controller further adjusts an operating frequency of the switching control signal according to a feedback signal to control an amplitude of the alternating signal.

如請求項7所述之驅動電路，其中該驅動電路更包含一電流偵測電路，電性連接於該些變壓器及該控制器之間，用來根據該些變壓器所產生之驅動電流之大小，產生該回授訊號。 The driving circuit of claim 7, wherein the driving circuit further comprises a current detecting circuit electrically connected between the transformer and the controller for using a driving current generated by the transformers. The feedback signal is generated.

如請求項8所述之驅動電路，其中該電流偵測電路包含有：複數個整流器，每一該些整流器分別電性連接於對應之該變壓器，用來對該些變壓器所產生之驅動電流進行整流，以產生複數個整流訊號；以及一濾波器，電性連接於該些整流器，用來接收該些整流訊號，並對該些整流訊號進行濾波，以產生該回授訊號。 The driving circuit of claim 8, wherein the current detecting circuit comprises: a plurality of rectifiers, each of the rectifiers being electrically connected to the corresponding transformer, for driving current generated by the transformers Rectifying to generate a plurality of rectified signals; and a filter electrically connected to the rectifiers for receiving the rectified signals and filtering the rectified signals to generate the feedback signals.

如請求項9所述之驅動電路，其中每一該些整流器係為一半波擷取電路。 The driving circuit of claim 9, wherein each of the rectifiers is a half-wave extraction circuit.

如請求項9所述之驅動電路，其中該濾波器係為一電阻電容式低通濾波器。 The driving circuit of claim 9, wherein the filter is a resistance-capacitance low-pass filter.

如請求項1所述之驅動電路，其中該切換控制訊號係用來控制該直交流換流器內部之功率電晶體開關。 The driving circuit of claim 1, wherein the switching control signal is used to control a power transistor switch inside the direct current converter.

如請求項1所述之驅動電路，其中該些背光源係為冷陰極螢光燈管(Code Cathode Fluorescent Lamp，CCFL)。 The driving circuit of claim 1, wherein the backlights are Cold Cathode Fluorescent Lamps (CCFLs).

如請求項1所述之驅動電路，其中每一該些變壓器具有一初級線圈(Primary Winding)電性連接於該直交流換流器，及一次級線圈(Secondary Winding)電性連接於對應之該背光源。 The driving circuit of claim 1, wherein each of the transformers has a primary winding electrically connected to the direct current converter, and a secondary winding is electrically connected to the corresponding one. Backlight.