TWI467547B - Active organic light emitting diode pixel circuit and operating method thereof - Google Patents

Description

Active organic light emitting diode pixel circuit and operation method thereof

An organic light emitting diode pixel circuit and an operating method thereof, in particular to an active organic light emitting diode pixel circuit and an operating method thereof.

With the advancement of optoelectronic technology and semiconductor technology, flat panel displays have been widely used in many electronic devices, such as mobile phones, notebook computers or tablets. The active-matrix organic light-emitting diode (AMOLED) display is regarded as the best display panel to replace the traditional liquid crystal display because of its wide viewing angle, high contrast and high reaction speed. .

The active organic light emitting diode display is arranged in a matrix by an active organic light emitting diode pixel circuit. The organic light emitting diode pixel circuit mainly comprises a capacitor, a driving transistor and an organic light emitting diode. The capacitor is used for storing the signal voltage and providing the signal voltage to the driving transistor, and the driving transistor provides the driving current according to the signal voltage. The organic light-emitting diode causes the organic light-emitting diode to emit light. However, the organic light-emitting diode is gradually deteriorated by the long-time driving and the external environment, and the threshold voltage shift is increased, and the driving current provided by the driving transistor is attenuated, thereby causing the attenuation of the light-emitting luminance of the organic light-emitting diode. And unstable. When the brightness of the organic light emitting diode is unstable, the color of the active organic light emitting diode display is uneven and the picture quality is further affected.

Therefore, in order to pursue a stable and good quality of an active organic light-emitting diode display, there is an urgent need to improve the above disadvantages.

One aspect of the present invention is an active organic light-emitting diode pixel circuit, which can be used to avoid the attenuation of the luminance of the organic light-emitting diode caused by the increase of the threshold voltage of the organic light-emitting diode. .

According to an embodiment of the invention, the active organic light emitting diode pixel circuit includes an organic light emitting diode, a driving circuit, a switching circuit, and a capacitor. The organic light emitting diode is connected to the first power source. The driving circuit is connected to the organic light emitting diode. The switching circuit is connected to the driving circuit, the organic light emitting diode and the signal input end, wherein the driving circuit is directly connected to the second power source or electrically connected to the second power source through the switching circuit. The first end and the second end of the capacitor are connected to the inside of the switching circuit. In the charging state, the switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the first power source, or the switching circuit electrically connects the first end of the capacitor to the second power source And electrically connecting the second end of the capacitor to the signal input end. In the compensation state, the switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the anode of the organic light emitting diode, or the switching circuit electrically connects the first end of the capacitor The anode of the organic light emitting diode and electrically connecting the second end of the capacitor to the signal input end. In the illuminating state, the switching circuit electrically connects the first end of the capacitor to the driving circuit, and electrically connects the second end of the capacitor to the driving circuit and the anode of the organic light emitting diode.

According to an embodiment of the invention, when the driving circuit is directly connected to the second power source, the driving circuit is a first transistor, and the first source/drain of the first transistor is connected to the anode of the organic light emitting diode and the first transistor Second source / bungee Connect the second power supply.

According to an embodiment of the invention, the switching circuit includes a second transistor, a third transistor, a fourth transistor, and a fifth transistor. A first source/drain of the second transistor is coupled to the first end of the capacitor, and a second source/drain of the second transistor is coupled to the gate of the first transistor. A first source/drain of the third transistor is coupled to the first end of the capacitor and a first source/drain of the second transistor, and a second source/drain of the third transistor is coupled to the signal input. The first source/drain of the fourth transistor is connected to the second end of the capacitor, and the second source/drain of the fourth transistor is connected to the first source/drain of the first transistor and the anode of the organic light-emitting diode. The first source/drain of the fifth transistor is connected to the second end of the capacitor and the first source/drain of the fourth transistor, and the second source/drain of the fifth transistor is connected to the first power source.

According to an embodiment of the invention, the first to fifth transistors are all N-type transistors.

According to an embodiment of the invention, the gate of the second transistor is connected to the first select line. The gate of the third transistor is connected to the second select line. The gate of the fourth transistor is connected to the third selection line. The gate of the fifth transistor is connected to the fourth selection line.

According to an embodiment of the invention, the first, third, and fourth transistors are N-type transistors, and the second and fifth transistors are P-type transistors.

According to an embodiment of the invention, the gates of the second transistor and the third transistor are connected to the first selection line, and the gates of the fourth and fifth transistors are connected to the second selection line.

According to an embodiment of the invention, when the driving circuit is electrically connected to the second power source through the switching circuit, the driving circuit is a first transistor, and the first transistor The first source/drain is connected to the anode of the organic light emitting diode, and the second source/drain of the first transistor is connected to the switching circuit.

According to an embodiment of the invention, the switching circuit includes a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, and a seventh transistor. The first source/drain of the second transistor is coupled to the second source/drain of the first transistor, and the second source/drain of the second transistor is coupled to the second source. The first source/drain of the third transistor is connected to the first source/drain of the second transistor and the second source/drain of the first transistor, and the second source/drain of the third transistor is connected The gate of a transistor. The first source/drain of the fourth transistor is connected to the second source/drain of the third transistor and the gate of the first transistor, and the second source/drain of the fourth transistor is connected to the first end of the capacitor . The first source/drain of the fifth transistor is connected to the second source/drain of the fourth transistor and the first end of the capacitor, and the second source/drain of the fifth transistor is connected to the anode of the organic light-emitting diode And a first source/drain of the first transistor. A first source/drain of the sixth transistor is coupled to the second end of the capacitor, and a second source/drain of the sixth transistor is coupled to the signal input. The first source/drain of the seventh transistor is connected to the first source/drain of the sixth transistor and the second end of the capacitor, and the second source/drain of the seventh transistor is connected to the second of the fifth transistor A source/drain, an anode of the organic light emitting diode, and a first source/drain of the first transistor.

According to an embodiment of the invention, the first to seventh transistors are all N-type transistors.

According to an embodiment of the invention, the gates of the second and fourth transistors are connected to the first selection line. The gates of the third and sixth transistors are connected to the second selection line. The gate of the fifth transistor is connected to the third selection line. The gate of the seventh transistor is connected to the fourth selection line.

According to an embodiment of the invention, the first, second, third, fourth, and sixth transistors are N-type transistors, and the fifth and seventh transistors are P-type transistors.

According to an embodiment of the invention, the gates of the second, fourth, and fifth transistors are connected to the first selection line, and the gates of the third, sixth, and seventh transistors are connected to the second selection line.

Another technical aspect of the present invention is an operation method applied to an active organic light emitting diode pixel circuit, which can make the active organic light emitting diode pixel circuit not be driven by organic light after driving for a long time. The offset of the threshold voltage of the diode rises and decays.

According to an embodiment of the present invention, an active organic light emitting diode pixel circuit operation method, wherein the active organic light emitting diode pixel circuit comprises an organic light emitting diode, a driving circuit, a switching circuit, and a capacitor. The organic light emitting diode is connected to the first power source. The driving circuit is directly connected to the second power source or electrically connected to the second power source through the switching circuit. The switching circuit is connected to the signal input terminal. The capacitor is connected to the switching circuit. And the steps of the operation method of the active organic light emitting diode pixel circuit include:

(a) when in the charging state, the control switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the first power source, or controls the switching circuit to electrically charge the first end of the capacitor The second power source is connected, and the second end of the capacitor is electrically connected to the signal input end.

(b) When the compensation state is obtained, the control switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the anode of the organic light emitting diode, or controls the switching circuit to the capacitor One end is electrically connected to the anode of the organic light emitting diode, and the second end of the capacitor is electrically Connect the signal input.

(c) When the light is in a state, the control switching circuit electrically connects the first end of the capacitor to the driving circuit, and electrically connects the second end of the capacitor to the driving circuit and the anode of the organic light emitting diode.

According to an embodiment of the invention, when the driving circuit is directly connected to the second power source: the driving circuit is a first transistor, and the first source/drain of the first transistor is connected to the anode of the organic light emitting diode and the first transistor The second source/drain is connected to the second power source.

The switching circuit includes a second transistor, a third transistor, a fourth transistor, and a fifth transistor. a first source/drain of the second transistor connects the first end of the capacitor and a first source/drain of the third transistor, and a second source/drain of the second transistor is connected to the gate of the first transistor . The second source/drain of the third transistor is coupled to the signal input. A first source/drain of the fourth transistor connects the second end of the capacitor and a first source/drain of the fifth transistor. The second source/drain of the fourth transistor is connected to the first source/drain of the first transistor and the anode of the organic light-emitting diode. The second source/drain of the fifth transistor is connected to the first power source.

And step (a) includes turning on the third and fifth transistors, and breaking the second and fourth transistors, so that the voltage at the first end of the capacitor is the voltage at the signal input end, and the voltage at the second end of the capacitor is the first power source. Voltage.

According to an embodiment of the invention, the step (b) includes turning on the third and fourth transistors, and disconnecting the second and fifth transistors to discharge the capacitor through the organic light emitting diode until the organic light emitting diode has no current. by.

According to an embodiment of the invention, the step (c) includes turning on the second and fourth transistors, and breaking the third and fifth transistors, so that the first transistor is The potential difference across the capacitor drives the organic light emitting diode.

According to an embodiment of the invention, when the driving circuit is electrically connected to the first power source through the switching circuit: the driving circuit is a first transistor, and the first source/drain of the first transistor is connected to the anode of the organic light emitting diode.

The switching circuit includes a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, and a seventh transistor. The first source/drain of the second transistor is connected to the second source/drain of the first transistor and the first source/drain of the third transistor, and the second source/drain of the second transistor is connected Two power supplies. a second source/drain of the third transistor is coupled to the gate of the first transistor and a first source/drain of the fourth transistor, and a second source/drain of the fourth transistor is coupled to the first end of the capacitor And a first source/drain of the fifth transistor. A second source/drain of the fifth transistor is coupled to the anode of the organic light emitting diode, the first source/drain of the first transistor, and the second source/drain of the seventh transistor. The first source/drain of the sixth transistor is connected to the second end of the capacitor and the first source/drain of the seventh transistor, and the second source/drain of the sixth transistor is connected to the signal input.

And step (a) includes turning on the second, third, fourth, and sixth transistors, and breaking the fifth and seventh transistors, so that the voltage at the first end of the capacitor is the voltage of the second power source, and the capacitor is second. The voltage at the terminal is the voltage at the signal input.

According to an embodiment of the invention, the step (b) includes turning on the third, fifth, and sixth transistors, and disconnecting the second, fourth, and seventh transistors to discharge the capacitor through the organic light emitting diode until organic The light-emitting diode has no current flowing through it.

According to an embodiment of the invention, the step (c) includes turning on the second, fourth, and seventh transistors, and breaking the third, fifth, and sixth transistors, so that the first transistor drives the organic according to the potential difference between the two ends of the capacitor. Light-emitting diode.

In summary, by applying the circuit architecture and the operation mode of the above embodiment, the capacitor can be connected to the first and second power sources, the signal input end, and the anode of the organic light emitting diode in the charging and compensation states by controlling the switching circuit. And in the light-emitting state, the driving circuit is operated with the potential difference across the capacitor, so that the driving current supplied by the driving circuit increases as the threshold voltage of the organic light-emitting diode increases. In this way, the problem of the luminance degradation of the organic light-emitting diode caused by long-time operation can be avoided, and the color unevenness of the active organic light-emitting diode display caused by the attenuation of the light-emitting luminance is also solved, and the active organic The quality of the LED display can also be effectively improved.

The spirit and scope of the present disclosure will be apparent from the following description of the preferred embodiments of the present disclosure. Modifications do not depart from the spirit and scope of the disclosure.

As used herein, "connected", if not specified in the specification, may be a direct connection or an indirect connection, that is, one end is connected to the other end, with or without an intermediary. In contrast, "direct connection" as used herein means that one end is not connected to the other end through an intermediary. In addition, "electrical connection" as used herein means that an electrical signal can be transmitted between one end and the other end.

The "first source / bungee" and "second source / bungee" used in this article Refers to the source or drain of the transistor. When the "first source/drain" is the source, the "second source/dip" is the drain, and when the "first source/dip" is the drain "Second source / bungee" is the source.

The conventional active organic light-emitting diode pixel circuit may cause the driving current to decrease due to the shift of the threshold voltage of the light-emitting diode after a long period of use, and cause the light-emitting brightness of the organic light-emitting diode. The attenuation causes the picture quality of the active organic light emitting diode display to deteriorate. Therefore, if the switching circuit in the active organic light emitting diode pixel circuit is controlled so that the potential difference across the capacitor increases as the threshold voltage of the organic light emitting diode increases, the capacitor can be used. The drive circuit is controlled to cause the drive circuit to generate a drive current corresponding to the threshold voltage. When the offset of the threshold voltage of the organic light-emitting diode is increased due to long-term use, the driving current is also increased to maintain the luminance of the organic light-emitting diode.

1 is a circuit diagram of an active organic light emitting diode pixel circuit 100 in accordance with a first embodiment of the present invention. The active organic light emitting diode pixel circuit 100 includes an organic light emitting diode 110, a driving circuit 120, a switching circuit 130, and a capacitor 140. The organic light emitting diode 110 is connected to the first power source 10. The driving circuit 120 is connected to the organic light emitting diode 110 and directly connected to the second power source 20. The switching circuit 130 is connected to the driving circuit 120, the organic light emitting diode 110, the first power source 10, and the signal input terminal 30. The first end 141 and the second end 142 of the capacitor 140 are connected to the inside of the switching circuit 130. Here, the voltage V _{dd of the} second power source 20 is higher than the voltage V _{ss of the} first power source 10.

In the first embodiment, the driving circuit 120 can be the first transistor T1, and the first source/drain 11 is connected to the anode of the organic light emitting diode 110, and the first The second source/drain 12 of a transistor is directly coupled to the second power source 20. The switching circuit 130 then includes a second transistor T2, a third transistor T3, a fourth transistor T4, and a fifth transistor T5. The first source/drain 21 of the second transistor T2 is coupled to the first end 141 of the capacitor 140, and the second source/drain 22 of the second transistor T2 is coupled to the gate of the first transistor T1. The first source/drain 31 of the third transistor T3 is connected to the first end 141 of the capacitor 140 and the first source/drain 21 of the second transistor T2, and the second source/drain 32 of the third transistor T3 is connected. Signal input terminal 30. The first source/drain 41 of the fourth transistor T4 is connected to the second end 142 of the capacitor 140, and the second source/drain 42 of the fourth transistor T4 is connected to the first source/drain 11 of the first transistor T1 and The anode of the organic light emitting diode 110. The first source/drain 51 of the fifth transistor T5 is connected to the second end 142 of the capacitor 140 and the first source/drain 41 of the fourth transistor T4, and the second source/drain 52 of the fifth transistor T5 is connected. The first power source 10.

The first to fifth transistors T1, T2, T3, T4, and T5 are all N-type transistors, wherein the gate of the second transistor T2 is connected to the first selection line S1, and the gate of the third transistor T3 is connected. The second selection line S2, the gate of the fourth transistor T4 is connected to the third selection line S3, and the gate of the fifth transistor T5 is connected to the fourth selection line S4.

Fig. 2 is a timing chart of the first to fourth selection lines S1, S2, S3, and S4 in the first embodiment of the present invention. According to FIG. 2, the operation method of the active organic light emitting diode pixel circuit 100 is as follows: in the charging state (a), controlling the second and fourth selection lines S2 and S4 to be at a high voltage level to turn on the third, The fifth transistor T3, T5, and controls the first and third selection lines S1, S3 to be at a low voltage level to open the second and fourth transistors T2, T4, so that the first end 141 of the capacitor 140 is electrically connected to The signal input terminal 30 and the second end 142 of the capacitor 140 are electrically connected to the first power source 10, and the equivalent circuit is as shown in FIG. At this time, the capacitor 140 is charged by the signal input terminal 30, so that the voltage V _c1 of the first terminal 141 of the capacitor 140 is the voltage V _data of the signal input terminal 30, and the voltage V _c2 of the second terminal 142 of the capacitor 140 is first. The voltage V _{ss of the} power source 10. That is: V _c1 =V _data

V _c2 =V _ss

In the compensation state (b), the second and third selection lines S2 and S3 are controlled to be at a high voltage level to turn on the third and fourth transistors T3 and T4, and the first and fourth selection lines S1 and S4 are controlled. The low voltage level is used to open the second and fifth transistors T2 and T5, so that the first end 141 of the capacitor 140 is electrically connected to the signal input terminal 30, and the second end 142 of the capacitor 140 is electrically connected to the first power source 10. The equivalent circuit is shown in Figure 4. At this time, the capacitor 140 is discharged through the organic light emitting diode 110 until the organic light emitting diode 110 has no current, so that the voltage of the second terminal V _c2 of the capacitor 140 is the threshold voltage V _{th_oled} of the organic light emitting diode 110 and The sum of the voltages V _ss of the first power source 10 and the voltage V _c1 of the first terminal 141 of the capacitor 140 are maintained at the voltage V _data of the signal input terminal 30. That is: V _c1 =V _data

V _c2 =V _{th_oled} +V _ss

The potential difference across capacitor 140 is V _c1 -V _c2 =V _data -V _{th_oled} -V _ss

In the light-emitting state (c), the first and third selection lines S1 and S3 are controlled to be at a high voltage level to turn on the second and fourth transistors T2 and T4, and the second and fourth selection lines S2 and S4 are controlled. The low voltage level is used to open the third and fifth transistors T3 and T5, so that the first end 141 of the capacitor 140 is electrically connected to the gate of the first transistor T1, and the second end 142 of the capacitor 140 is electrically connected. To the first source/drain 11 of the first transistor T1 and the anode of the organic light-emitting diode 110, the equivalent circuit is as shown in FIG. At this time, the first transistor T1 generates a driving current _Ioled according to a potential difference across the capacitor 140 to drive the organic light emitting diode 110. The driving current I _oled can be calculated according to this formula: I _oled =K(V _gs -V _{th_TFT} )^2

Where V _{gs is} the potential difference across the capacitor 140. That is: V _gs =V _c1 -V _c2 =V _data -V _{th_oled} -V _ss

Therefore, it can be further known that I _oled =K(V _data -V _{th_oled} -V _ss -V _{th_TFT} )^2

In the above formula, K is a constant, and V _{th — TFT} is the threshold voltage of the first transistor T1. It is seen, by the above operation of the switching circuit 130, as can the drive current I _oled OLED _V th_oled 110 threshold voltage shift increases. Therefore, compensation can be obtained by attenuating the luminance of the light emitted by the organic light-emitting diode 110 for a long time.

Fig. 6 is a circuit diagram of the active organic light emitting diode pixel circuit 100 in accordance with the second embodiment of the present invention. In the second embodiment, the architecture of the active organic light emitting diode pixel circuit 100 is similar to that of the first embodiment, so the same portions will not be described herein. The difference between the two is that, in the second embodiment, the first, third, and fourth transistors are N-type transistors, and the second and fifth transistors are P-type transistors, wherein the second and the second The gates of the three transistors T2 and T3 are connected to the first selection line S1, and the gates of the fourth and fifth transistors T4 and T5 are connected to the second selection line S2.

Through the above replacement, the second embodiment reduces the two selection lines compared to the first embodiment, so that the complexity of the system can be reduced to facilitate the implementation of the embodiment of the present invention.

Figure 7 is a timing chart of the first and second selection lines S1, S2 in the second embodiment of the present invention. According to FIG. 7, the operation method of the active organic light emitting diode pixel circuit 100 is as follows: in the charging state (a), the first selection line S1 is controlled to a high voltage level to turn on the third crystal T3 and the second circuit is broken. Transistor T2. Controlling the second selection line S2 to a low voltage level to open the fourth transistor T4 and turn on the fifth transistor T5, so that the first end 141 of the capacitor 140 is electrically connected to the signal input terminal 30, and the second of the capacitor 140 is made. The terminal 142 is electrically connected to the first power source 10, and the equivalent circuit is as shown in FIG. At this time, the charging method of the capacitor 140 is the same as that of the first embodiment, and therefore will not be described herein.

In the compensation state (b), the first selection line S1 is controlled to be at a high voltage level to turn on the third crystal T3 and to disconnect the second transistor T2. Controlling the second selection line S2 to a high voltage level to open the fifth transistor T5 and turn on the fourth transistor T4, so that the first end 141 of the capacitor 140 is electrically connected to the signal input terminal 30, and the second of the capacitor 140 is made. The terminal 142 is electrically connected to the first power source 10, and the equivalent circuit is as shown in FIG. At this time, the discharge mode of the capacitor 140 via the organic light-emitting diode 110 is the same as that of the first embodiment, and thus will not be described herein.

In the light-emitting state (c), the second selection line S2 is controlled to a high voltage level to open the fifth transistor T5 and turn on the fourth transistor T4. Controlling the first selection line S1 to a low voltage level to open the third transistor T3 and turn on the second transistor T2, the first end 141 of the capacitor 140 can be electrically connected to the first a gate of the transistor T1, and electrically connecting the second end 142 of the capacitor 140 to the first source/drain 11 of the first transistor T1 and the anode of the organic light-emitting diode 110, and the equivalent circuit is the fifth The figure shows. At this time, the first transistor T1 is the same as the first embodiment in that the organic light-emitting diode 110 is driven according to the potential difference across the capacitor 140, and thus will not be described herein.

The above description of the first and second embodiments is intended to provide a pixel circuit and an operation method for five transistors, so that the luminance of the light-emitting luminance caused by the organic light-emitting diode 110 during long-time driving can be compensated. In order to make the description of the embodiment of the present invention more complete, an embodiment of a pixel circuit and an operation method of seven transistors is further provided below.

Fig. 8 is a circuit diagram of the active organic light emitting diode pixel circuit 100 in accordance with the third embodiment of the present invention. In the third embodiment, the active organic light emitting diode pixel circuit 100 includes an organic light emitting diode 110, a driving circuit 120, a switching circuit 130, and a capacitor 140. The organic light emitting diode 110 is connected to the first power source 10. The driving circuit 120 is connected to the organic light emitting diode 110 and connected to the second power source 20 through the switching circuit 130. The switching circuit 130 is connected to the driving circuit 120, the organic light emitting diode 110, the second power source 20, and the signal input terminal 30. The first end 141 and the second end 142 of the capacitor 140 are connected to the inside of the switching circuit 130. Here, the voltage V _{dd of the} second power source 20 is higher than the voltage V _{ss of the} first power source 10.

In the third embodiment, the driving circuit 120 is the first transistor T1, and the first source/drain 11 of the first transistor T1 is connected to the anode of the organic light-emitting diode 110, and the second source/汲 of the first transistor The pole 12 is connected to the switching circuit 130. The switching circuit 130 includes a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, a sixth transistor T6, and a seventh transistor. T7. The first source/drain 21 of the second transistor T2 is connected to the second source/drain 12 of the first transistor T1, and the second source/drain 22 of the second transistor T2 is connected to the second power source 20. The first source/drain 31 of the third transistor T3 is connected to the first source/drain 21 of the second transistor T2 and the second source/drain 12 of the first transistor T1, and the third transistor T3 The two source/drain 32 is connected to the gate of the first transistor T1. The first source/drain 41 of the fourth transistor T4 is connected to the second source/drain 32 of the third transistor T3 and the gate of the first transistor T1, and the second source/drain of the fourth transistor T4 42 connects the first end 141 of the capacitor 140. The first source/drain 51 of the fifth transistor T5 is coupled to the second source/drain 42 of the fourth transistor T4 and the first end 141 of the capacitor 140, and the second source/drain 52 of the fifth transistor T5 The anode of the organic light emitting diode 110 and the first source/drain 11 of the first transistor T1 are connected. The first source/drain 61 of the sixth transistor T6 is coupled to the second terminal 142 of the capacitor 140, and the second source/drain 62 of the sixth transistor T6 is coupled to the signal input terminal 30. The first source/drain 71 of the seventh transistor T7 is connected to the first source/drain 61 of the sixth transistor T6 and the second end 142 of the capacitor 140, and the second source/drain 72 of the seventh transistor T7 The second source/drain 52 of the fifth transistor T5, the anode of the organic light-emitting diode 110, and the first source/drain 11 of the first transistor T1 are connected.

The first to seventh transistors T1, T2, T3, T4, T5, T6, and T7 are all N-type transistors, and the gates of the second and fourth transistors T2 and T4 are connected to the first selection line S1. The gates of the third and sixth transistors T3, T6 are connected to the second selection line S2. The gate of the fifth transistor T5 is connected to the third selection line S3. The gate of the seventh transistor T7 is connected to the fourth selection line S4.

Fig. 9 is a timing chart of the first to fourth selection lines S1, S2, S3, and S4 in the third embodiment of the present invention. According to FIG. 9 , the operation method of the active organic light emitting diode pixel circuit 100 is as follows: in the charging state (a), controlling the first and second selection lines S1 and S2 to be at a high voltage level to turn on the second, The third, fourth, and sixth transistors T2, T3, T4, and T6, and controlling the third and fourth selection lines S3 and S4 to be at a low voltage level to open the fifth and seventh transistors T5 and T7 to make the capacitor The first end 141 of the 140 is electrically connected to the second power source 20, and the second end 142 of the capacitor 140 is electrically connected to the signal input terminal 30. The equivalent circuit is shown in FIG. At this time, the capacitor 140 is charged, the voltage V _c1 of the first terminal 141 is the voltage V _dd of the second power source 20, and the voltage V _c2 of the second terminal 142 of the capacitor 140 is the voltage V _data of the signal input terminal 30. That is: V _c1 =V _dd

V _c2 =V _data

In the compensation state (b), the second and third selection lines S2 and S3 are controlled to be at a high voltage level to turn on the third, fifth, and sixth transistors T3, T5, and T6, and to control the first and fourth selections. The lines S1 and S4 are at a low voltage level to open the second, fourth, and seventh transistors T2, T4, and T7, so that the first end 141 of the capacitor 140 is electrically connected to the anode of the organic light emitting diode 110, and is maintained. The second end 142 of the capacitor 140 is electrically connected to the signal input terminal 30, and the equivalent circuit is as shown in FIG. At this time, the capacitor 140 is discharged through the organic light emitting diode 110 until the organic light emitting diode 110 has no current, so that the voltage V _c1 of the first end 141 of the capacitor 140 is the threshold voltage of the organic light emitting diode 110 V _{th_oled} The sum of the voltage V _ss of the first power source and the voltage V _c2 of the second terminal 142 of the capacitor 140 are maintained at the voltage V _data of the signal input terminal 30. That is: V _c1 =V _{th_oled} +V _ss

V _c2 =V _data

The potential difference across the capacitor is V _c1 -V _c2 =V _{th_oled} +V _ss -V _data

In the light-emitting state (c), the first and fourth selection lines S1 and S4 are controlled to be at a high voltage level to turn on the second, fourth, and seventh transistors T2, T4, and T7, and to control the second and third selections. The lines S2 and S3 are at a low voltage level to open the third, fifth, and sixth transistors T3, T5, and T6, so that the first end 141 of the capacitor 140 is electrically connected to the gate of the first transistor T1, and The second end 142 of the capacitor 140 is electrically connected to the first source/drain 11 of the first transistor and the anode of the organic light-emitting diode 110, and the equivalent circuit is as shown in FIG. At this time, the first transistor T1 generates a driving current _Ioled according to a potential difference across the capacitor 140 to drive the organic light emitting diode 110. The driving current I _oled can be calculated according to this formula: I _oled =K(V _gs -V _{th_TFT} )^2

Where V _{gs is} the potential difference across the capacitor 140. That is: V _gs =V _c1 -V _c2 =V _{th_oled} +V _ss -V _data

Therefore, it is further known that I _oled =K(V _{th_oled} +V _ss -V _data -V _{th_TFT} )^2

In the above formula, K is a constant, and V _{th — TFT} is the threshold voltage of the first transistor T1. It is seen, by the above operation of the switching circuit 130, as can the drive current I _oled OLED _V th_oled 110 threshold voltage shift increases. Therefore, compensation can be obtained by attenuating the luminance of the light emitted by the organic light-emitting diode 110 for a long time.

Figure 12 is a circuit diagram of the active organic light emitting diode pixel circuit 100 in accordance with a fourth embodiment of the present invention. In the fourth embodiment, the architecture of the active organic light emitting diode pixel circuit 100 is the same as that of the third embodiment. Imitation, so the same thing is not described here. The difference between the two is that in the fourth embodiment, the first, second, third, fourth, and sixth transistors are N-type transistors, and the fifth and seventh transistors are P-type transistors. a crystal, wherein the gates of the second, fourth, and fifth transistors T2, T4, and T5 are connected to the first selection line S1, and the gates of the third, sixth, and seventh transistors T3, T6, and T7 are connected to the second selection. Line S2.

Through the above-described permutation, the fourth embodiment reduces the two selection lines compared to the third embodiment, so that the complexity of the system can be reduced to facilitate the implementation of the embodiment of the present invention.

Figure 13 is a timing chart of the selection lines S1, S2 in the fourth embodiment of the present invention. According to FIG. 13 , the operation method of the active organic light emitting diode pixel circuit 100 is as follows: in the charging state (a), controlling the first and second selection lines S1 and S2 to be at a high voltage level to turn on the second, The third, fourth, and sixth transistors T2, T3, T4, and T6 electrically connect the first end 141 of the capacitor 140 to the second power source 20, and electrically connect the second end 142 of the capacitor 140 to the signal input end. 30, the equivalent circuit is shown in Figure 10. At this time, the charging method of the capacitor 140 is the same as that of the third embodiment, and therefore will not be described herein.

In the compensation state (b), the second selection line S2 is controlled to a high voltage level to turn on the third and sixth transistors T3, T6 and to open the seventh transistor. Controlling the first selection line S1 to a low voltage level to open the second and fourth transistors T2 and T4 and turning on the fifth transistor T5 to electrically connect the first end 141 of the capacitor 140 to the organic light emitting diode 110 The anode, and the second end 142 of the capacitor 140 is electrically connected to the signal input terminal 30, and the equivalent circuit is as shown in FIG. At this time, the capacitor 140 is discharged via the organic light emitting diode 110. The electrical mode is the same as that of the third embodiment, and therefore will not be described herein.

In the light-emitting state (c), the first selection line S1 is controlled to a high voltage level to turn on the second and fourth transistors T2, T4 and to disconnect the fifth transistor T5. Controlling the second selection line S2 to a low voltage level to open the third and sixth transistors T3, T6 and turning on the seventh transistor T7, so that the first end 141 of the capacitor 140 is electrically connected to the gate of the first transistor T1. The second terminal 142 of the capacitor 140 is electrically connected to the first source/drain 11 of the first transistor T1 and the anode of the organic light-emitting diode 110, and the equivalent circuit is as shown in FIG. At this time, the first transistor T1 is the same as the third embodiment in that the organic light-emitting diode 110 is driven according to the potential difference across the capacitor 140, and thus will not be described herein.

In summary, embodiments of the present invention provide an active organic light emitting diode pixel circuit including an organic light emitting diode, a driving circuit, a switching circuit, and a capacitor. The organic light emitting diode is connected to the first power source. The driving circuit is connected to the organic light emitting diode. The switching circuit is connected to the driving circuit, the organic light emitting diode and the signal input end, wherein the driving circuit is directly connected to the second power source or electrically connected to the second power source through the switching circuit. The first end and the second end of the capacitor are connected to the inside of the switching circuit.

On the other hand, the steps of the operation method of the active organic light emitting diode pixel circuit include:

(a) when in the charging state, the control switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the first power source, or controls the switching circuit to electrically charge the first end of the capacitor The second power source is connected, and the second end of the capacitor is electrically connected to the signal input end.

(b) When the compensation state is reached, the control switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to the organic The anode of the light emitting diode or the control switching circuit electrically connects the first end of the capacitor to the anode of the organic light emitting diode, and electrically connects the second end of the capacitor to the signal input end.

(c) When the light is in a state, the control switching circuit electrically connects the first end of the capacitor to the driving circuit, and electrically connects the second end of the capacitor to the driving circuit and the anode of the organic light emitting diode.

Through the pixel circuit and the operation method proposed above, the luminescence attenuation caused by the organic light-emitting diode pixel circuit after long-time driving can be compensated, thereby ensuring the stability of the active organic light-emitting diode display and further Further improve the quality of active organic light-emitting diode displays.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and retouched without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

10‧‧‧First power supply

11‧‧‧First source/bungee

12‧‧‧Second source/bungee

20‧‧‧second power supply

21‧‧‧First source/bungee

22‧‧‧Second source/bungee

30‧‧‧Signal input

31‧‧‧First source/bungee

110‧‧‧Active Organic Light Emitting Diodes

120‧‧‧Drive circuit

130‧‧‧Switching circuit

140‧‧‧ capacitor

141‧‧‧ first end

142‧‧‧ second end

T1‧‧‧first transistor

T2‧‧‧second transistor

32‧‧‧Second source/bungee

41‧‧‧First source/bungee

42‧‧‧Second source/bungee

51‧‧‧First source/bungee

52‧‧‧Second source/bungee

61‧‧‧First source/bungee

62‧‧‧Second source/bungee

71‧‧‧First source/bungee

72‧‧‧Second source/bungee

100‧‧‧Active Organic Light Emitting Diode Pixel Circuit

T3‧‧‧ third transistor

T4‧‧‧ fourth transistor

T5‧‧‧ fifth transistor

T6‧‧‧ sixth transistor

T7‧‧‧ seventh transistor

S1‧‧‧ first choice line

S2‧‧‧ second selection line

S3‧‧‧ third option line

S4‧‧‧ fourth choice line

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; The circuit diagram drawn by the prime circuit.

Fig. 2 is a timing chart of a selection line according to the first embodiment of the present invention.

Fig. 3 is an equivalent circuit of the active organic light emitting diode pixel circuit according to Fig. 1 in a charged state.

Fig. 4 is an equivalent circuit drawn in the compensation state of the active organic light emitting diode pixel circuit according to Fig. 1.

Fig. 5 is an equivalent circuit drawn in the light-emitting state of the active organic light-emitting diode pixel circuit according to Fig. 1 or Fig. 8.

Figure 6 is a circuit diagram of an active organic light emitting diode pixel circuit in accordance with a second embodiment of the present invention.

Fig. 7 is a timing chart of a selection line according to a second embodiment of the present invention.

Figure 8 is a circuit diagram of an active organic light emitting diode pixel circuit in accordance with a third embodiment of the present invention.

Figure 9 is a timing chart of a selection line according to a third embodiment of the present invention.

Fig. 10 is an equivalent circuit of the active organic light emitting diode pixel circuit according to Fig. 8 in a charged state.

Fig. 11 is an equivalent circuit drawn in the compensation state of the active organic light emitting diode pixel circuit according to Fig. 8.

Figure 12 is a circuit diagram of an active organic light emitting diode pixel circuit in accordance with a fourth embodiment of the present invention.

Figure 13 is a timing chart of a selection line according to a fourth embodiment of the present invention.

10‧‧‧First power supply

11‧‧‧First source/bungee

12‧‧‧Second source/bungee

20‧‧‧second power supply

21‧‧‧First source/bungee

22‧‧‧Second source/bungee

30‧‧‧Signal input

31‧‧‧First source/bungee

32‧‧‧Second source/bungee

41‧‧‧First source/bungee

42‧‧‧Second source/bungee

51‧‧‧First source/bungee

52‧‧‧Second source/bungee

100‧‧‧Active Organic Light Emitting Diode Pixel Circuit

110‧‧‧Active Organic Light Emitting Diodes

120‧‧‧Drive circuit

130‧‧‧Switching circuit

140‧‧‧ capacitor

141‧‧‧ first end

142‧‧‧ second end

T1‧‧‧first transistor

T2‧‧‧second transistor

T3‧‧‧ third transistor

T4‧‧‧ fourth transistor

T5‧‧‧ fifth transistor

S1‧‧‧ first choice line

S2‧‧‧ second selection line

S3‧‧‧ third option line

S4‧‧‧ fourth choice line

Claims (19)

An active organic light emitting diode pixel circuit includes: an organic light emitting diode connected to a first power source; a driving circuit connecting the organic light emitting diode; a switching circuit connecting the driving circuit, the organic a light emitting diode and a signal input end, wherein the driving circuit is directly connected to a second power source or electrically connected to the second power source through the switching circuit; and a capacitor, wherein the capacitor has a first end and a second end The end is connected to an internal portion of the switching circuit; wherein, in a state of charge, the switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor The first power source, or the switching circuit electrically connects the first end of the capacitor to the second power source, and the second end of the capacitor is electrically connected to the signal input end; wherein, in a compensation state, The switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to an anode of the organic light emitting diode, or the switching power The first end of the capacitor is electrically connected to the anode of the organic light emitting diode, and the second end of the capacitor is electrically connected to the signal input end; and wherein, in a light emitting state, the switching circuit The first end of the capacitor is electrically connected to the driving circuit, and the second end of the capacitor is electrically connected to the driving circuit and the anode of the organic light emitting diode; wherein when the driving circuit is directly connected to the first In the case of two power supplies, the switching circuit includes: a first transistor, wherein a first source/drain of the first transistor is connected to the first end of the capacitor, and a second source/drain of the first transistor is connected to the driving circuit; a second transistor, wherein a first source/drain of the second transistor is connected to the first end of the capacitor and the first source/drain of the first transistor, and a second of the second transistor a source/drain is connected to the signal input terminal; a third transistor, wherein a first source/drain of the third transistor is connected to the second end of the capacitor, and a second source of the third transistor is a drain electrode connecting the driving circuit and the anode of the organic light emitting diode; and a fourth transistor, wherein a first source/drain of the fourth transistor is connected to the second end of the capacitor and the third The first source/drain of the transistor, a second source/drain of the fourth transistor is connected to the first power source. The active organic light emitting diode pixel circuit of claim 1, wherein when the driving circuit is directly connected to the second power source, the driving circuit is a fifth transistor, and the first one of the fifth transistors a source/drain is connected to the anode of the organic light emitting diode and a second source/drain of the fifth transistor is connected to the second power source, and the second source/drain of the first transistor is connected to the first A gate of the fifth transistor, and the second source/drain of the third transistor is coupled to the first source/drain of the fifth transistor. The active organic light emitting diode pixel circuit of claim 2, wherein the first to fifth transistors are all N-type transistors. The active organic light emitting diode pixel circuit of claim 3, wherein: a gate of the first transistor is connected to a first selection line; and a gate of the second transistor is connected to a second selection a gate of the third transistor is coupled to a third select line; and a gate of the fourth transistor is coupled to a fourth select line. The active organic light emitting diode circuit of claim 2, wherein the second, third, and fifth transistors are N-type transistors, and the first and fourth transistors are P-type transistors. The active organic light emitting diode pixel circuit of claim 5, wherein the gates of the first and second transistors are connected to a first selection line; and the gates of the third and fourth transistors are Connect a second selection line. The active organic light emitting diode pixel circuit of claim 1, wherein when the driving circuit is electrically connected to the second power source through the switching circuit, the driving circuit is a fifth transistor, and the fifth power A first source/drain of the crystal is connected to the anode of the organic light emitting diode, and a second source/drain of the fifth transistor is connected to the switching circuit. The active organic light emitting diode pixel circuit of claim 7, wherein the switching circuit comprises: a sixth transistor, wherein a first source/drain of the sixth transistor is connected to the fifth transistor The second source/drain, the second source/drain of the sixth transistor is connected to the second power source; a seventh transistor, wherein a first source/drain of the seventh transistor is connected to the second source/drain The first source/drain of the sixth transistor and the second source/drain of the fifth transistor, a second source/drain of the seventh transistor is connected to a gate of the fifth transistor An eighth transistor, wherein a first source/drain of the eighth transistor is connected to the second source/drain of the seventh transistor and the gate of the fifth transistor, the eighth a second source/drain of the crystal is coupled to the first end of the capacitor; a ninth transistor, wherein a first source/drain of the ninth transistor is coupled to the second source of the eighth transistor/ a drain and a first end of the capacitor, a second source/drain of the ninth transistor connecting the anode of the organic light emitting diode and the fifth transistor The first source/drain; a tenth transistor, wherein a first source/drain of the tenth transistor is connected to the second end of the capacitor, and a second source/汲 of the tenth transistor a pole connected to the signal input terminal; and an eleventh transistor, wherein a first source/drain of the eleventh transistor is connected to the first source/drain of the tenth transistor and the first of the capacitor a second source, a second source/drain of the eleventh transistor is connected to the second source/drain of the ninth transistor, the anode of the organic light emitting diode, and the first The first source/drain of the five transistors. The active organic light emitting diode pixel circuit of claim 8, wherein the fifth to eleventh transistors are all N-type transistors. The active organic light emitting diode pixel circuit of claim 9, wherein: the gates of the sixth and eighth transistors are connected to a first selection line; and the gates of the seventh and tenth transistors are connected a second selection line; the gate of the ninth transistor is connected to a third selection line; and the gate of the eleventh transistor is connected to a fourth selection line. The active organic light emitting diode pixel circuit of claim 8, wherein the fifth, sixth, seventh, eighth, and tenth transistors are N-type transistors, and the ninth and eleventh The transistor is a P-type transistor. The active organic light emitting diode circuit of claim 11, wherein: the gates of the sixth, eighth, and ninth transistors are connected to a first selection line; and the seventh, tenth, and The gate of the eleven transistor is connected to a second select line. An operation applied to an active organic light-emitting diode pixel circuit The active organic light emitting diode pixel circuit includes an organic light emitting diode, a driving circuit, a switching circuit and a capacitor. The organic light emitting diode is connected to a first power source, and the driving circuit is directly Connecting a second power source or electrically connecting the second power source through the switching circuit, the switching circuit is connected to a signal input terminal, the capacitor is connected to the switching circuit, and the active organic light emitting diode pixel circuit is The method includes the following steps: (a) when the charging state is controlled, the switching circuit electrically connects a first end of the capacitor to the signal input end, and electrically connects a second end of the capacitor to the first Powering, or controlling the switching circuit to electrically connect the first end of the capacitor to the second power source, and electrically connecting the second end of the capacitor to the signal input end; (b) when compensating the state, controlling the The switching circuit electrically connects the first end of the capacitor to the signal input end, and electrically connects the second end of the capacitor to an anode of the organic light emitting diode, or controls the switching power The first end of the capacitor is electrically connected to the anode of the organic light emitting diode, and the second end of the capacitor is electrically connected to the signal input end; (c) when the light emitting state is controlled, the switching circuit is controlled The first end of the capacitor is electrically connected to the driving circuit, and the second end of the capacitor is electrically connected to the driving circuit and the anode of the organic light emitting diode; wherein when the driving circuit is directly connected to the first In the case of two power supplies, the switching circuit includes a first transistor, a second transistor, a third transistor, and a fourth transistor, wherein a first source/drain of the first transistor is coupled to the capacitor a first end and a first source/drain of the second transistor, and a second source/drain of the first transistor is connected to the driving circuit, the second transistor a second source/drain is connected to the signal input end, a first source/drain of the third transistor is connected to the second end of the capacitor and a first source/drain of the fourth transistor, a second source/drain of the third transistor is connected to the driving circuit and the anode of the organic light emitting diode, a second source/drain of the fourth transistor is connected to the first power source, and wherein the step (a) comprising: conducting the second and fourth transistors, and breaking the first and third transistors, so that the voltage of the first end of the capacitor is the voltage at the input end of the signal, and the The voltage at the two terminals is the voltage of the first power source. The operating method of the active organic light emitting diode pixel circuit of claim 13, wherein when the driving circuit is directly connected to the second power source: the driving circuit is a fifth transistor, the fifth transistor a first source/drain is connected to the anode of the organic light emitting diode and a second source/drain of the fifth transistor is connected to the second power source, the second source/drain of the first transistor A gate of the fifth transistor is connected, and the second source/drain of the third transistor is connected to the first source/drain of the fifth transistor. The method for operating an active organic light emitting diode pixel circuit according to claim 14, wherein the step (b) comprises: turning on the second and third transistors, and breaking the first and fourth transistors, so that The capacitor is discharged through the organic light emitting diode until no current is passed through the organic light emitting diode. The operating method of the active organic light emitting diode pixel circuit of claim 15, wherein the step (c) comprises: turning on the first and third transistors, and breaking the second and fourth transistors, so that The fifth transistor drives the organic light emitting diode according to a potential difference across the capacitor. The operating method of the active organic light emitting diode pixel circuit of claim 13, wherein when the driving circuit is electrically connected to the first power source through the switching circuit: the driving circuit is a fifth transistor, a first source/drain of the fifth transistor is connected to the anode of the organic light emitting diode; the switching circuit includes a sixth transistor, a seventh transistor, an eighth transistor, and a ninth transistor. a tenth transistor and an eleventh transistor, wherein a first source/drain of the sixth transistor is connected to a second source/drain of the fifth transistor and one of the seventh transistors a first source/drain, a second source/drain of the sixth transistor is connected to the second power source, and a second source/drain of the seventh transistor is connected to a gate of the fifth transistor and a first source/drain of the eighth transistor, a second source/drain of the eighth transistor connecting the first end of the capacitor and a first source/drain of the ninth transistor, a second source/drain of the ninth transistor is connected to the anode of the organic light emitting diode, the fifth transistor a source/drain and a second source/drain of the eleventh transistor, a first source/drain of the tenth transistor is coupled to the second end of the capacitor and the eleventh transistor a first source/drain, a second source/drain of the tenth transistor is coupled to the signal input; and wherein step (a) comprises: Turning on the sixth, seventh, eighth, and tenth transistors, and breaking the ninth and eleventh transistors, so that the voltage of the first end of the capacitor is the voltage of the second power source, and the capacitor is The voltage at the second end is the voltage at the input of the signal. The method for operating an active organic light emitting diode pixel circuit according to claim 17, wherein the step (b) comprises: turning on the seventh, ninth, and tenth transistors, and breaking the sixth, eighth, The eleventh transistor discharges the capacitor through the organic light emitting diode until no current is passed through the organic light emitting diode. The method for operating an active organic light emitting diode pixel circuit according to claim 18, wherein the step (c) comprises: turning on the sixth, eighth, eleventh transistors, and breaking the seventh and ninth And a tenth transistor, wherein the fifth transistor drives the organic light emitting diode according to a potential difference across the capacitor.