The invention uses (N+1) mirror output circuits to provide a larger current for driving pixels. Referring to
Referring to
The AMOLED 36 is coupled to a voltage source, such as a ground voltage GND. The transistor MP1 has a first terminal coupled to the data driving unit 32 and a control terminal coupled to the scan driving unit 34. The transistor MP2 has a first terminal coupled to a second terminal of the transistor MP1 and a control terminal coupled to the scan driving unit 34. The transistor MP3 has a first terminal coupled to the first terminal of the transistor MP2, a second terminal coupled to a first voltage, such as an operational voltage VDD, and a control terminal coupled to a second terminal of the transistor MP2. The transistor MP4 has a first terminal coupled to the AMOLED 36, a second terminal coupled to the operational voltage VDD and a control terminal coupled to the control terminal of the transistor MP3. The capacitor C has a first terminal coupled to the control terminal of the transistor MP4 and a second terminal coupled to the second terminal of the transistor MP4.
During a writing time period, a scan signal Scan outputted by the scan driving unit 34 turns on the transistors MP1 and MP2. Due to a current IData of the data driving unit 32, the transistor MP3 also generates the same current IData. Owing that the transistors MP3 and MP4 form a circuit of current mirror, the transistor MP4 generates a current IOLED proportional to the current IData and outputs the current IOLED to the AMOLED 36 to display the corresponding luminance. At the same time, the capacitor C is also charged to the corresponding voltage level.
Afterward, during a display time period, the scan signal Scan turns off the transistors MP1 and MP2, and thus the transistor MP4 is electrically isolated from the data driving unit 12. The voltage difference between the source and gate of the transistor MP4 stably maintains at the corresponding voltage level by the capacitor C, and thus the current IOLED stably maintains at a specific value.
In the above AMOLED panel 30, the data driving unit 32 includes a reference current source circuit 310, (N+1) mirror output circuits 320˜32n and (N+1) switch elements S0˜Sn, wherein N is a positive integer. The reference current source circuit 310 is for providing a reference current I. The mirror output circuits 320˜32n are coupled to the reference current source circuit 310. The AMOLED pixel unit 31 can draft data currents I0˜In from the data driving unit 32. The data currents I0˜In have a proportion relationship corresponding to the reference current I, such as the data current Im (m=0˜n) is 2m×I, wherein I is a constant current.
The switch elements S0˜Sn are disposed in correspondence with the mirror output circuits 320˜32n for controlling the AMOLED pixel unit 31 to draft the data currents I0˜In. The position of switch elements S0˜Sn can be changed. For example, each of the switch elements S0˜Sn has a first terminal coupled to a ground voltage GND and a second terminal coupled to the corresponding mirror output circuit 320˜32n. The switch elements S0˜Sn can also be disposed at different positions. For example, each of the switch elements S0˜Sn has a first terminal coupled to the corresponding mirror output circuit 320˜32n and a second terminal coupled to the AMOLED pixel unit 31.
Whether the AMOLED pixel unit 31 can draft the data currents I0˜In to generate the data current IData depends on openness or closeness of the switch elements S0˜Sn. That is, the amount of the data current IData is controlled by the switch elements S0˜Sn. For example, when only the switch element S0 is turned on, the data current IData is smallest, which is equal to I. When the switch elements S0˜Sn are all turned on, the data current IData is largest, which is equal to (1+2+4+ . . . +2n)I=(2n+1−1)I. As mentioned above, the AMOLED pixel unit 31 can obtain (2n+1−1) different kinds of data currents IData. Therefore, the AMOLED panel 30 can drive the AMOLED 36 by a large current.
In the above AMOLED panel 30, the first switch element to the fourth switch element can also be implemented by n-type metal oxide semiconductor (NMOS) transistors. Referring to
The above AMOLED panel 40 operates in the same rule as the AMOLED panel 30.
The AMOLED panel disclosed by the above embodiment of the invention uses a number of mirror output circuits to provide a larger current for driving the AMOLED pixels and provide different currents for driving the AMOLED pixels.
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
Number | Date | Country | Kind |
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095116424 | May 2006 | TW | national |