This application claims the priority benefit of Taiwan application serial no. 97113246, filed on Apr. 11, 2008.The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.
1.Field of the Invention
The present invention relates to a light source module, and more particularly to a back light module.
2.Description of Related Art
In recent years, back light modules in liquid crystal displays (LCD) mostly adopt light emitting diodes (LED's) that have features such as long life, high efficiency, and low pollution to the environment. Brightness of LED's relates to display quality of an LCD. Therefore, today's manufacturing technology emphasizes on the design of back light modules.
In another aspect, the voltage converter 110, the LED matrix 120, and a feedback compensation circuit 140 comprise a closed loop. An error amplifier 141 compares feedback voltages Vfb1˜Vfb4 generated by each set of the LED series with a reference voltage Vref, and a voltage controller 142 generates a control signal Sct according to the comparison result from the error amplifier 141. Accordingly, the voltage converter 110 adjusts a level the output voltage Vout based on the control signal Sct.
However, in practical applications, in the conventional back light module 100, the current of each set of the LED series is controlled by a switch and a current source so when contrast of a display image in an area control is raised, the number of the switches and the current sources in the current adjusting circuit 130 of the conventional back light module 100 must be increased in response. In this case, the conventional back light module 100 requires tremendous power consumption. As a result, temperature of internal circuits is increased and lifetime is decreased.
The present invention provides a back light module which uses a plurality of light source matrixes utilizing a same current adjusting circuit to lower power consumption of its own circuit.
The present invention provides a back light module that may correspondingly raise contrast of a display image with no need to increase the number of switches and current sources in a current adjusting circuit.
The present invention provides a back light module comprising a plurality of light source matrixes, a current adjusting circuit, and a light source driving circuit. Each of the light source matrixes comprises N light emitting units, where N is an integer greater than 1.First ends of the light emitting units are electrically connected to each other and a second end of the ith light emitting unit is electrically connected to an ith level switch line, where i is an integer and 1≦i≦N. In other words, the aforesaid light source matrixes are electrically connected to the N level switch lines.
In another aspect, the current adjusting circuit provides and controls a current that flows through each of the light source matrixes through the aforesaid level switch lines. The light source driving circuit is used to sequentially drive the aforesaid light source matrixes. The light source matrixes use the same current adjusting circuit through the N level switch lines so the power consumption of the back light module may be significantly decreased and thus its lifetime may be increased.
In one embodiment of the present invention, the aforesaid light source driving circuit comprises a plurality of second switches and a level control circuit. First ends of the second switches are used to receive a predetermined voltage. The light source driving circuit sequentially drives the second switches in a frame period. The level control circuit is used to generate a predetermined voltage and to adjust a level of the predetermined voltage once in every dimming time so as to switch the level of the predetermined voltage to one of a plurality of specified levels.
The present invention provides another back light module comprising a light source driving circuit, a plurality of light source matrixes, and a current adjusting circuit. Each of the light source matrixes comprises N light emitting units, where N is an integer greater than 1.The light source driving circuit is used to sequentially generate a plurality of driving pulses. The light source matrixes are individually driven according to the driving pulses.
In addition, first ends of the light emitting units are used to receive one of the driving pulses, while a second end of the ith light emitting unit is electrically connected to an ith level switch line, where i is an integer and 1≦i≦N. The current adjusting circuit provides and controls a current that flows through each of the light source matrixes through the aforesaid level switch lines. It should be noted that the light source matrixes use the same current adjusting circuit through the N level switch lines so the power consumption of the back light module may be significantly decreased and thus its lifetime may be increased.
In one embodiment of the present invention, the aforesaid light source driving circuit comprises a plurality of second switches and a level control circuit. First ends of the second switches are used to receive a predetermined voltage. The light source driving circuit is used to sequentially drive the second switches in a frame period such that second ends of the second switches sequentially provide the driving pulses. In addition, the level control circuit is used to generate a predetermined voltage and to adjust a level of the predetermined voltage once in every dimming time so as to switch the level of the predetermined voltage to one of a plurality of specified levels.
In one embodiment of the light source driving circuit, the light emitting units respectively comprise an LED series. Furthermore, the light source driving circuit drives one of the second switches once in every scan period, wherein the dimming time is an integral multiple of the frame period or the scan period.
In the present invention, a plurality of light source matrixes use a same current adjusting circuit by means of sequentially driving a plurality of light source matrixes. Accordingly, when contrast of a display image under area control is raised, the number of switches and current sources in the current adjusting circuit of the back light module need not be increased in response.
In order to make the aforementioned and other objects, features and advantages of the present invention more comprehensible, several embodiments accompanied with figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Looking at the internal structure of the light source matrix 211, first ends of the light emitting units UA1˜UAN are electrically connected to each other. In addition, a second end of the light emitting unit UA1 is electrically connected to a level switch line SL1, a second end of the light emitting unit UA2 is electrically connected to a level switch line SL2, a second end of the light emitting unit UA3 is electrically connected to a level switch line SL3, . . . , and a second end of the light emitting unit UAN is electrically connected to a level switch line SLN. In other words, a second end of the ith light emitting unit UAi in the light source matrix 211 is electrically connected to the ith level switch line SLi, where i is an integer and 1≦i≦N.
Similarly, looking at the internal structure of the light source matrix 212, first ends of the light emitting units UB1˜UBN are electrically connected to each other. In addition, a second end of the light emitting unit UB1 is electrically connected to a level switch line SL1, a second end of the light emitting unit UB2 is electrically connected to a level switch line SL2, a second end of the light emitting unit UB3 is electrically connected to a level switch line SL3, . . . , and a second end of the light emitting unit UBN is electrically connected to a level switch line SLN. In other words, a second end of the ith light emitting unit UBi in the light source matrix 212 is electrically connected to the ith level switch line SLi.
Furthermore, Referring to
In an overall operation, the light source driving circuit 230 sequentially outputs a plurality of driving pulses PU1˜PU3 respectively corresponding to the light source matrixes 211˜213. The light source matrixes 211˜213 are driven to generate light sources after receiving the corresponding driving pulses PU1˜PU3. In other words, the light source driving circuit 230 sequentially drives the light source matrixes 211˜213 such that the light source matrixes 211˜213 sequentially generate light sources. Furthermore, the current adjusting circuit 220 provides and controls the current that flows through the light source matrixes 211˜213 such that an average current of the light source matrixes 211˜213 changes.
It should be noted that, in the present embodiment, the light source driving circuit 230 adjusts a voltage level of the driving pulses PU1˜PU3 to control the light sources generated by the light source matrixes 211˜213. In other words, the back light module 200 achieves a dimming mechanism through the light source driving circuit 230 and/or the current adjusting circuit 220. In addition, the light emitting units UA1˜UAN-UB1˜UBN, and UC1˜UCN respectively comprise an LED series. For example, as shown in
In order for those skilled in the art to better understand the spirit of the present invention, the internal structures of the current adjusting circuit 220 and the light source driving circuit 230 are further illustrated below.
Referring to
In an overall operation, the current adjusting circuit 220 switches the turn-on status of the switches SWA1˜SWAN to change the current sources CS1˜CSN so as to provide an average current for each light emitting unit at a predetermined time. In other words, the current adjusting circuit 220 adjusts the average current of the light source matrixes 211˜213 by controlling the switches SWA1˜SWAN. Therefore, the back light module 200 achieves a dimming mechanism through the current adjusting circuit 220.
It should be noted that the light source matrixes 211˜213 are all electrically connected to the level switch lines SL1˜SLN. That is, the light source matrixes 211˜213 share the use of the switches SWA1˜SWAN and the current sources CS1˜CSN in the current adjusting circuit 220. Accordingly, when contrast of a display image under area control is increased, the number of the switches and the current sources in the current adjusting circuit 220 of the back light module 200 need not be increased correspondingly. In other words, compared with the conventional technology, the present embodiment may more efficiently lower the power consumption of the back light module and thus promote circuit functionality and lifetime.
Continuously referring to
In an overall operation, the light source driving circuit 230 sequentially turns on the switches SWB1˜SWB3 to generate driving pulses PU1˜PU3 during a frame period TF. In another aspect, the level control circuit 231 is used to generate a predetermined voltage Vpre and to adjust a level of the predetermined voltage Vpre once in every dimming time T41 so as to switch the level of the predetermined voltage Vpre to one of a plurality of specified levels LV1˜LV3. Accordingly, the voltage levels of the driving pulses PU1˜PU3 vary with the change of the level of the predetermined voltage Vpre. In other words, the level control circuit 231 adjusts the average current of the light source matrixes 211˜213 by controlling the level of the predetermined voltage Vpre. Therefore, the back light module 200 may also achieve a dimming mechanism through the light source driving circuit 230.
Furthermore, the level control circuit 231 comprises a plurality of diodes D1˜D3 and a plurality of switches SWC1˜SWC3. The diodes D1˜D3 respectively correspond to the specified levels LV1˜LV3. Anode terminals of the diodes D1˜D3 are electrically connected to the corresponding specified levels. In addition, the switches SWC1˜SWC3 also respectively correspond to the diodes D1˜D3. First ends of the switches SWC1˜SWC3 are electrically connected to cathode terminals of the corresponding diodes, while second ends of the switches SWC1˜SWC3 are electrically connected to the first ends of the switches SWB1˜SWB3.
Here, the diodes D1˜D3 are used to limit the current direction formed during the turn-on of the switches SWC1˜SWC3. In another aspect, the level control circuit 231 turns on one of the switches SWC1˜SWC3 once in every dimming time T41 such that the level of the predetermined voltage Vpre changes once in every dimming time T41. It should be noted that if the light source driving circuit 230 turns on one of the switches SWB1˜SWB3 once in every scan period T42 during a frame period TF, those skilled in the art may set the dimming time T41 to be an integral multiple of the frame period TF or the scan period T42.
For example,
In the embodiment shown in
In other words, the current levels of the current pulses PI1˜PI3 change once in every dimming time T41. In another aspect, the current adjusting circuit 220 controls the width of the current pulses PI1˜PI3 in connection with the scan mechanism of the light source driving circuit 230 so as to make the duty cycle Tp of the current I1 equal to the scan period T42. The operation mechanism of the light source driving circuit 230 and the current adjusting circuit 220 in relation to the currents I2˜I3 can be deduced from the above illustration.
Furthermore,
In addition, in the embodiment shown in
In summary, in the present invention, a plurality of light source matrixes use a same current adjusting circuit by means of sequentially driving a plurality of light source matrixes. Accordingly, when contrast of a display image under area control is raised, the number of the switches and the current sources in the current adjusting circuit of the back light module need not be increased in response. In other words, the present invention may effectively decrease the power consumption of the back light module and increase the circuit functionality and lifetime.
It will be apparent to those of ordinary skills in the technical field that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention covers modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
---|---|---|---|
97113246 A | Apr 2008 | TW | national |
Number | Name | Date | Kind |
---|---|---|---|
5751263 | Huang et al. | May 1998 | A |
6545652 | Tsuji | Apr 2003 | B1 |
6914390 | Koyama | Jul 2005 | B2 |
7511695 | Furukawa et al. | Mar 2009 | B2 |
7619598 | Pulvirenti et al. | Nov 2009 | B2 |
20070247399 | Yamashita et al. | Oct 2007 | A1 |
20090153075 | Li et al. | Jun 2009 | A1 |
Number | Date | Country |
---|---|---|
M253031 | Dec 2004 | TW |
200629967 | Aug 2006 | TW |
Number | Date | Country | |
---|---|---|---|
20090256495 A1 | Oct 2009 | US |