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.
The present invention aims at solving a brightness-non-uniform problem occurred in a frame presented by an OELD due to a voltage drop of an anode resistor of the OLED in the conventional art. Therefore, the present invention provides a source driver, a display and a method for driving the display panel to solve the aforementioned problem.
The display panel 105 is coupled to the gate driver 101 and the source driver 103. The display panel 105 comprises a plurality of light-emitting elements (OLEDs or LEDs here) D11-Dnm, and each of the light-emitting elements D11-Dnm is disposed between each of the gate wirings G1-Gm and each of the source wirings I1-In. Each of the source wirings I1-In is coupled to its corresponding anode of each of the light-emitting elements D1-Dnm, and each of the gate wirings G1-Gm is coupled to its corresponding cathode of each of the light-emitting elements D11-Dnm.
In the present embodiment, the DAC M1b is used to convert the programming data into a first analog signal as1 and then output it. The operational amplifier M1c is used to receive and amplify the first analog signal as1 by a factor of, for example, 10, and output a second analog signal as2. The first input end of the operational amplifier M1c is used to receive the first analog signal as1, the second input end of the operational amplifier M1c is coupled to a first end of the resistor Rref and the first current source P0, and the output end of the operational amplifier M1c is used to output the second analog signal as2. Furthermore, a second end of the resistor Rref is coupled to a first potential, i.e., a ground potential, thereby providing a reference voltage required by a feedback path for the operational amplifier M1c.
The first current source P0 generates a first current L1 according to the second analog signal as2. The second current source P1 mirrors the first current L1 by a factor to generate a second current L2, wherein the factor is determined according to the display data. The second current source P1 may comprise a sub current source circuit C1 or a plurality of sub current source circuits C1-Cn. When the second current source P1 only comprises the sub current source circuit C1, the sub current source circuit C1 determines whether to provide a controlled current (not shown) according to the display data, wherein the controlled current b1 is just the second current L2. When the second current source P1 comprises the sub current source circuits C1-Cn, the sub current source circuits C1-Cn determine whether to provide the controlled circuits b1-bn (not shown) according to the display data, wherein the sum of the controlled currents b1-bn provided is the second current L2.
In the present embodiment, the sub current source circuit C1 comprises a controlled current source B1 (not shown) and a switch SW1, wherein the controlled current source B1 is used to provide the controlled current b1, and the switch SW1 is coupled between the controlled current source B1 and a second potential, i.e., a ground potential, and determines its on or off state according to a control signal S1 generated by the display data. In another embodiment of the present invention, the switch SW1 can also be coupled between the controlled current source B1 and the transistor T1. Furthermore, when the second current source P1 comprises the sub current source circuits C1-Cn, the circuit structure and coupling relation of each of the sub current source circuits C1-Cn are both similar to those of the sub current source circuit C1, so the on or off state is determined according to the control signals S1-Sn generated by the display data.
A current mirror unit M1d is coupled to the first current source P0 and the second current source P1 to mirror the sum of the first current L1 and the second current L2, thereby outputting a data current Id1. The data current Id1 is the sum of the first current L1 and the second current L2 because the currents L1 and L2 are connected in parallel. In the present embodiment, the current mirror unit M1d comprises a first transistor T1 (a P-type transistor here) and a second transistor T2 (a P-type transistor here). The drain of the transistor T1 is coupled to the drain of the transistor T2 and a second potential, i.e., a system voltage VDD, while the gate and the source of the transistor T1 are coupled together, and then coupled to the first current source P0 and the second current source P1. The gate of the transistor T2 is coupled to the gate of the transistor T1, and the source of the transistor T2 is coupled to a source wiring I1. In the present embodiment, the circuit structures and coupling relation of the current-driving units M2-Mn of the source driver 103 are both similar to the current-driving unit M1, which will not be described any more here.
In the present embodiment, when the current-driving unit M1 of the source driver 103 receives the display data, the programming data is converted into the first analog signal as1 by the DAC M1b of the current-driving unit M1, and then the first analog signal as1 is amplified by the operational amplifier M1, so as to output the second analog signal as2. Then, the first current source P0 generates the first current L1 according to the size of the second analog signal as2, and the second current source P1 turns on the switch SW1 according to the control signal S1 generated by the programming data and generates a second current L2, current magnitude of which is equal to that of the first current L1.
After that, after receiving the data current Id1, the current mirror unit M1d mirrors and outputs the data current Id1 to the source wiring I1. According to the data current Id1 required by the programming data, it is only necessary to make the size of the second analog signal as2 output by the DAC M1b through the operational amplifier M1c be sufficient to generate half of the data current Id1, i.e., the first current L1. As such, the data current Id1 required by the programming data can also be acquired through the adding of the second current L2 generated by the second current source P1.
As described above, when the current-driving unit M2-Mn of the source driver 103 receive the display data, it is also converted into the data currents Id2-Idn through the current-driving units M2-Mn, and then the data currents Id2-Idn are output to the corresponding source wirings I2-In through the current mirror units M2c-Mnc of the current-driving units M2-Mn.
Next, the data currents Id1-Idn converted by the current-driving units M1-Mn of the source driver 103 are output to the corresponding source wirings I1-In, and drive each of the enabled light-emitting elements D11-Dnm together with the scanning voltages Vscan (low potentials here) output from the gate wirings G1-Gm of the gate driver 101.
According to the spirit of the present invention, the source wirings I1-In of the source driver 103 can also be correspondingly coupled to the cathodes of the light-emitting elements D11-Dnm, and the gate wirings G1-Gm are correspondingly coupled to the anodes of the light-emitting elements D11-Dnm. As such, each of the enabled light-emitting elements D11-Dnm can be driven only by replacing the first transistor T1 and the second transistor T2 in the current mirror units M1c-Mnc of the current-driving units M1-Mn with N-type transistors having the drains connected to the ground potential, and then coupling the switch SW1 of the current-driving units M1-Mn between the sub current source circuit C1 and the system voltage VDD, together with the scanning voltages Vscan (high potentials here) output from the gate wirings G1-Gm of the gate driver 101.
In view of the above, since the source driver provided by the present invention generates the data current by using the two-stage current mirror, the source driver is not affected by the voltage drop of the anode resistor of the OLED, such that the frame presented by the OELD becomes more uniform and stable.
It will be apparent to those skilled in the art 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 cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Number | Date | Country | Kind |
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95112368 | Apr 2006 | TW | national |