201023157 九、發明說明： . 【發明所屬之技術領域】 本發明係關於一種外接圖像訊號源之液晶顯示裝置。 【先前技術】 液晶顯示裝置由於其具有重量輕、耗電少、低輻射及便 於攜帶等優點，已經廣泛應用於各種現代化資訊設備，如顯 示器、電視、行動電話及數位產品等。 請參閱圖1，其係一種先前技術外接圖像訊號源之液晶 Φ顯示裝置之結構示意圖。該液晶顯示裝置1包括一電源板 11、一控制電路12及一液晶面板13。該電源板11為該控制電 路12提供工作電壓。該圖像訊號源14藉由該控制電路12為該 液晶面板13提供圖像訊號。 當該圖像訊號源14有一定時間無圖像訊號輸出時，該控 制電路12控制該液晶顯示裝置1處於省電模式，該電源板11 為該控制電路12提供省電模式所需之工作電壓。 雖然省電模式時該控制電路12工作電壓相對較低，從而 φ使得該液晶顯示裝置1之功耗降低，但是由於該電源板11自 身工作之功耗比較高，導致該液晶顯示裝置1之功耗仍較高。 【發明内容】 有鑑於此，有必要提供一種功耗較低之液晶顯示裝置。 一種外接圖像訊號源之液晶顯示裝置，其包括一電源 板、一控制電路及一液晶面板。該電源板用於為該控制電路 提供工作電壓。該圖像訊號源藉由該控制電路為該液晶面板 提供圖像訊號。當該液晶顯示裝置處於省電模式時，該控制 電路發出控制訊號控制該電源板停止工作，由該圖像訊號源 201023157 為該控制電路提供工作電壓。 一種外接圖像訊號源之液晶顯示裝置，其包括一電源 板、一控制電路及一液晶面板。該電源板為該控制電路提供 工作電壓。該圖像訊號源包括一電源輸出端及一訊號輸出 端，該訊號輸出端輸出之圖像訊號經該控制電路提供至該液 晶面板。當該液晶顯不裝置處於省電模式時’由該圖像訊號 源之電源輸出端為該控制電路提供工作電壓。 相較於先前技術，本發明之外接圖像訊號源之液晶顯示 © 裝置中，當該液晶顯示裝置處於省電模式時，由該圖像訊號 源為該控制電路提供工作電壓，減少了該電源板之功耗，從 而使得該液晶顯示裝置之功耗較低。 【實施方式】 請參閱圖2，其係本發明外接圖像訊號源之液晶顯示裝 置第一實施方式之結構示意圖。該液晶顯示裝置2包括一交 流電源20、一電源板21、一控制電路22、一液晶面板23及一 第一開關電路25。該電源板21為該控制電路22提供工作電 ❿壓。 該圖像訊號源24為電腦主機等可產生圖像訊號之裝 置。該圖像訊號源24包括一訊號輸出端241及一電源輸出端 242。該圖像訊號源24藉由該訊號輸出端241輸出圖像訊號， 圖像訊號經過該控制電路22進行處理後提供至該液晶面板 23進行顯示。該電源輸出端242藉由該第一開關電路25為該 控制電路22提供工作電壓。該控制電路22控制該第一開關電 路25導通或截止。 該電源板21包括一輸入端211及一控制器212。該交流電 201023157 源20與該輸入端211電連接’為該電源板21提供工作電壓。 — 該控制器212包括一反饋控制端213。該控制電路22藉由該反 饋控制端213控制該控制器212工作或停止工作，進而控制該 電源板21是否為該控制電路22提供工作電壓。該反饋控制端 213接收高電平訊號時，該控制器212停止工作。 請參閱圖3，其係圖2中該第一開關電路25之結構示意 圖。該第一開關電路25包括一電源輸入端251、一控制訊號 輸入端252、一輸出端253、一第一電容254、一第一偏置電 ❿阻255、一分壓電阻256、一電晶體257、一第二電容258、一 第二偏置電阻259及一雙極電晶體260。該電晶體257為PNP 型場效應電晶體。該雙極電晶體260為NPN型雙極電晶體。 該第一電容254及該第二電容258起濾波作用。 該電源輸入端251與該電源輸出端242電連接，同時經該 第一電容254接地。該電晶體257之閘極串聯該分壓電阻256 後與該雙極電晶體260之集極電連接，其源極與該電源輸入 端251電連接並串聯該第一偏置電阻255後與該雙極電晶體 ❿260之集極電連接，其汲極作為該輸出端253與該控制電路22 相連接。該控制訊號輸入端252與該控制電路22電連接，該 雙極電晶體260之基極與該控制訊號輸入端252電連接，該雙 極電晶體260之射極接地。該雙極電晶體260之基極經該第二 偏置電阻259及該第二電容258並聯組成之濾波偏置電路接 地。 當該訊號輸出端241有一定時間無圖像訊號輸出時，該 控制電路22控制該液晶顯示装置2處於省電模式。同時，該 控制電路22發出一高電平控制訊號至該反饋控制端213及該 201023157 控制訊號輪入端252。此時，該控制器212接收該高電平之反 饋控制訊號停止工作，從而該電源板21停止工作。該控制訊 號輸入端252所接收該高電平控制訊號也使得該雙極電晶體 260之基極為高電平’該雙極電晶體26〇導通，從而該電晶體 257之閘極接地，因此該電晶體257導通，該電源輸出端242 輸出之工作電壓經該電源輸入端251及該電晶體257後由該 輸出端253輸出至該控制電路22，使該控制電路22在省電模 式時從該圖像訊號源24獲得工作電壓。當該訊號輸出端241 ❹正常輸出圖像訊號時，該液晶顯示裝置2處於正常工作模 式’該電晶體257關閉’該交流電源20藉由該電源板21為該 控制電路22供電。 相較於先前技術’本實施方式外接圖像訊號源之液晶顯 示裝置2中’當該液晶顯示裝置2處於省電模式時，該控制電 路22發出控制訊號至該控制器213，使得該控制器213停止工 作，從而該電源板21停止工作。同時，該控制電路22發出控 制訊號使該第一開關電路25導通，由該液晶顯示裝置2外接 ❹之圖像訊號源24為該控制電路22提供工作電壓。由於省電模 式下該電源板21不再為該控制電路21提供工作電壓，所以可 降低功耗，因此該液晶顯示裝置2功耗較低。 請參閱圖4,其係本發明外接圖像訊號源之液晶顯示裝 置第二實施方式之結構示意圖。該液晶顯示裝置3與該液晶 顯示裝置2之結構基本相同，不同點在於：該液晶顯示裝置3 之輸入端311與交流電源3〇之間設置一第二開關電路36，控 制器312沒有反饋控制端即控制電路32不再控制該控制器 312。該第二開關電路36為繼電器。 9 201023157 * 該交流電源30經該第二開關電路36為該輸入端311提供 交流電。 當該液晶顯示裝置3處於省電模式時，該控制電路32發 出控制訊號至第一開關電路35及該第二開關電路36，以控制 該第一開關電路35處於導通狀態，該第二開關電路36處於斷 開狀態。該交流電源30無法藉由該第二開關電路36為該輸入 端311提供交流電，電源板31停止工作，電源輸出端342輸出 之工作電壓經該第一開關電路35提供至該控制電路32。當訊 0 號輸出端341正常輸出圖像訊號時，該液晶顯示裝置3處於正 常工作模式，該第二開關電路36閉合，該交流電源30藉由該 第二開關電路36為該電源板31供電，該電源板31為該控制電 路32供電。 第二實施方式之液晶顯示裝置3中，在省電模式下藉由 斷開該第二開關電路36使得該交流電源30無法輸出至該電 源板31，即該電源板31完全不通電。與第一實施方式中之電 源板21在省電模式下仍與交流電源20相連接之情況相比，該 ⑩液晶顯示裝置3之功耗可進一步降低。 綜上所述，本發明確已符合發明專利之要件，爰依法提 出申請專利。惟，以上所述者僅係本發明之較佳實施方式， 本發明之範圍並不以上述實施方式爲限，舉凡熟悉本案技藝 之人士援依本發明之精神所作之等效修飾或變化，皆應涵蓋 於以下申請專利範圍内。 【圖式簡單說明】 圖1係一種先前技術外接圖像訊號源之液晶顯示裝置之結構 示意圖。 201023157 、 圖2係本發明外接圖像訊號源之液晶顯示裝置第一實施方式 .之結構示意圖。 圖3係圖2所示液晶顯示裝置之第一開關電路之結構示意 圖。 圖4係本發明外接圖像訊號源之液晶顯示裝置第二實施方式 之結構示意圖。 【主要元件符號說明】 液晶顯示裝置 2、3 電源輸入端 251 交流電源 20、30 控制訊號輸入端 252 電源板 21、31 輸出端 253 輸入端 211、311 第一電容 254 控制器 212、312 第一偏置電阻 255 反饋控制端 213 分壓電阻 256 控制電路 22、32 電晶體 257 液晶面板 23 第二電容 258 圖像訊號源 24、34 第二偏置電阻 259 參 訊號輸出端 241、341 雙極電晶體 260 電源輸出端 242、342 第二開關電路 36 第一開關電路 25、35 11201023157 IX. Description of the Invention: [Technical Field] The present invention relates to a liquid crystal display device with an external image signal source. [Prior Art] Liquid crystal display devices have been widely used in various modern information devices such as displays, televisions, mobile phones, and digital products because of their advantages of light weight, low power consumption, low radiation, and easy portability. Please refer to FIG. 1 , which is a schematic structural diagram of a liquid crystal Φ display device of a prior art external image signal source. The liquid crystal display device 1 includes a power board 11, a control circuit 12, and a liquid crystal panel 13. The power board 11 provides an operating voltage to the control circuit 12. The image signal source 14 provides an image signal to the liquid crystal panel 13 by the control circuit 12. When the image signal source 14 has no image signal output for a certain period of time, the control circuit 12 controls the liquid crystal display device 1 to be in the power saving mode, and the power board 11 provides the control circuit 12 with the working voltage required for the power saving mode. . Although the operating voltage of the control circuit 12 is relatively low in the power saving mode, φ causes the power consumption of the liquid crystal display device 1 to be reduced, but the power consumption of the power supply panel 11 itself is relatively high, resulting in the work of the liquid crystal display device 1. The consumption is still high. SUMMARY OF THE INVENTION In view of the above, it is necessary to provide a liquid crystal display device with lower power consumption. A liquid crystal display device with an external image signal source includes a power board, a control circuit and a liquid crystal panel. The power board is used to provide operating voltage to the control circuit. The image signal source provides an image signal to the liquid crystal panel by the control circuit. When the liquid crystal display device is in the power saving mode, the control circuit sends a control signal to control the power board to stop working, and the image signal source 201023157 provides the operating voltage for the control circuit. A liquid crystal display device with an external image signal source includes a power board, a control circuit and a liquid crystal panel. The power board provides operating voltage to the control circuit. The image signal source includes a power output end and a signal output end, and the image signal outputted by the signal output end is supplied to the liquid crystal panel via the control circuit. When the liquid crystal display device is in the power saving mode, the power supply output terminal of the image signal source supplies the control circuit with an operating voltage. Compared with the prior art, in the liquid crystal display device of the external image signal source of the present invention, when the liquid crystal display device is in the power saving mode, the image signal source supplies the operating voltage to the control circuit, thereby reducing the power supply. The power consumption of the board makes the power consumption of the liquid crystal display device low. [Embodiment] Please refer to FIG. 2, which is a schematic structural view of a first embodiment of a liquid crystal display device with an external image signal source according to the present invention. The liquid crystal display device 2 includes an AC power source 20, a power board 21, a control circuit 22, a liquid crystal panel 23, and a first switch circuit 25. The power board 21 provides operating voltage to the control circuit 22. The image signal source 24 is a device for generating an image signal, such as a host computer. The image signal source 24 includes a signal output terminal 241 and a power source output terminal 242. The image signal source 24 outputs an image signal through the signal output terminal 241. The image signal is processed by the control circuit 22 and then supplied to the liquid crystal panel 23 for display. The power output 242 provides an operating voltage to the control circuit 22 via the first switching circuit 25. The control circuit 22 controls the first switching circuit 25 to be turned on or off. The power board 21 includes an input end 211 and a controller 212. The alternating current 201023157 source 20 is electrically coupled to the input terminal 211 to provide an operating voltage to the power strip 21. - The controller 212 includes a feedback control terminal 213. The control circuit 22 controls the controller 212 to operate or stop working by the feedback control terminal 213, thereby controlling whether the power supply board 21 supplies the operating voltage to the control circuit 22. When the feedback control terminal 213 receives the high level signal, the controller 212 stops operating. Please refer to FIG. 3, which is a schematic structural diagram of the first switch circuit 25 in FIG. The first switch circuit 25 includes a power input terminal 251, a control signal input terminal 252, an output terminal 253, a first capacitor 254, a first bias resistor 255, a voltage divider resistor 256, and a transistor. 257. A second capacitor 258, a second bias resistor 259, and a bipolar transistor 260. The transistor 257 is a PNP type field effect transistor. The bipolar transistor 260 is an NPN type bipolar transistor. The first capacitor 254 and the second capacitor 258 act as filtering. The power input terminal 251 is electrically coupled to the power output terminal 242 while being grounded via the first capacitor 254. The gate of the transistor 257 is connected in series with the voltage dividing resistor 256, and is electrically connected to the collector of the bipolar transistor 260. The source is electrically connected to the power input terminal 251 and connected in series with the first bias resistor 255. The collector of the bipolar transistor 260 is electrically connected, and its drain is connected to the control circuit 22 as the output terminal 253. The control signal input terminal 252 is electrically connected to the control circuit 22. The base of the bipolar transistor 260 is electrically connected to the control signal input terminal 252, and the emitter of the bipolar transistor 260 is grounded. The base of the bipolar transistor 260 is grounded via a filter bias circuit composed of the second bias resistor 259 and the second capacitor 258 in parallel. When the signal output terminal 241 has no image signal output for a certain period of time, the control circuit 22 controls the liquid crystal display device 2 to be in the power saving mode. At the same time, the control circuit 22 sends a high level control signal to the feedback control terminal 213 and the 201023157 control signal wheel 252. At this time, the controller 212 receives the feedback control signal of the high level to stop working, so that the power board 21 stops operating. The high level control signal received by the control signal input terminal 252 also causes the base of the bipolar transistor 260 to be at a high level. The bipolar transistor 26 is turned on, so that the gate of the transistor 257 is grounded. The transistor 257 is turned on, and the operating voltage outputted from the power output terminal 242 is outputted to the control circuit 22 via the power input terminal 251 and the transistor 257, so that the control circuit 22 is in the power saving mode. The image signal source 24 obtains the operating voltage. When the signal output terminal 241 ❹ normally outputs an image signal, the liquid crystal display device 2 is in a normal operation mode 'the transistor 257 is turned off'. The AC power source 20 supplies power to the control circuit 22 by the power source board 21. Compared with the prior art 'the liquid crystal display device 2 of the external image signal source of the present embodiment, when the liquid crystal display device 2 is in the power saving mode, the control circuit 22 sends a control signal to the controller 213, so that the controller The 213 is stopped, so that the power board 21 is stopped. At the same time, the control circuit 22 sends a control signal to turn on the first switch circuit 25. The image signal source 24 externally connected to the liquid crystal display device 2 supplies the control circuit 22 with an operating voltage. Since the power supply board 21 no longer supplies the operating voltage to the control circuit 21 in the power saving mode, power consumption can be reduced, and thus the liquid crystal display device 2 consumes less power. Please refer to FIG. 4 , which is a structural diagram of a second embodiment of a liquid crystal display device with an external image signal source according to the present invention. The liquid crystal display device 3 has substantially the same structure as the liquid crystal display device 2, except that a second switch circuit 36 is disposed between the input end 311 of the liquid crystal display device 3 and the AC power source 3, and the controller 312 has no feedback control. The end control circuit 32 no longer controls the controller 312. The second switching circuit 36 is a relay. 9 201023157 * The AC power source 30 supplies AC power to the input terminal 311 via the second switch circuit 36. When the liquid crystal display device 3 is in the power saving mode, the control circuit 32 sends a control signal to the first switch circuit 35 and the second switch circuit 36 to control the first switch circuit 35 to be in an on state. The second switch circuit 36 is in the off state. The AC power supply 30 cannot supply AC power to the input terminal 311 by the second switch circuit 36, the power board 31 stops operating, and the operating voltage outputted by the power output terminal 342 is supplied to the control circuit 32 via the first switch circuit 35. When the output terminal 341 outputs the image signal normally, the liquid crystal display device 3 is in the normal working mode, the second switch circuit 36 is closed, and the AC power source 30 supplies power to the power board 31 by the second switch circuit 36. The power board 31 supplies power to the control circuit 32. In the liquid crystal display device 3 of the second embodiment, the AC power source 30 cannot be output to the power source board 31 by turning off the second switch circuit 36 in the power saving mode, that is, the power source board 31 is completely de-energized. Compared with the case where the power source board 21 in the first embodiment is still connected to the AC power source 20 in the power saving mode, the power consumption of the liquid crystal display device 3 can be further reduced. In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention are It should be covered by the following patent application. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the structure of a liquid crystal display device of a prior art external image signal source. 201023157, FIG. 2 is a schematic structural view of a first embodiment of a liquid crystal display device with an external image signal source according to the present invention. Fig. 3 is a view showing the configuration of a first switching circuit of the liquid crystal display device shown in Fig. 2. Fig. 4 is a block diagram showing the structure of a second embodiment of a liquid crystal display device of an external image signal source of the present invention. [Main component symbol description] Liquid crystal display device 2, 3 Power input terminal 251 AC power supply 20, 30 Control signal input terminal 252 Power board 21, 31 Output terminal 253 Input terminal 211, 311 First capacitor 254 Controller 212, 312 First Bias resistor 255 Feedback control terminal 213 Divider resistor 256 Control circuit 22, 32 Transistor 257 LCD panel 23 Second capacitor 258 Image signal source 24, 34 Second bias resistor 259 Signal output 241, 341 Bipolar Crystal 260 power output 242, 342 second switch circuit 36 first switch circuit 25, 35 11