TWI390489B - Pixel circuit - Google Patents

Description

Pixel circuit

The present invention relates to a pixel circuit, and more particularly to a light-emitting diode (LED) voltage type compensation pixel circuit.

Fig. 1 is a diagram showing a conventional organic light emitting diode pixel circuit. This pixel circuit is a voltage type compensation pixel circuit. The pixel circuit includes an organic light emitting diode (OLED) 180, a first transistor 170, a driving transistor 130, a capacitor 150, and a second transistor 110. The first source/drain 176 of the first transistor 170 is coupled to the light emitting diode 180, wherein the first transistor 170 is controlled by the first scan signal. The drive transistor 130 has source/drain electrodes 132 and 136. Source/drain 132 is coupled to power supply terminal 140 via transistor 160 and source/drain 136 is coupled to source/drain 172 of first transistor 170. Capacitor 150 is coupled to gate 134 of drive transistor 130 and power terminal 140. When the second scan signal is asserted, the second transistor 110 is coupled to the source/drain 172 and the capacitor 150 of the first transistor 170, and to the gate 134 and the source of the driving transistor 130. / bungee 136.

Moreover, transistor 160 is off when the second scan signal is active; transistor 160 is conductive when the second scan signal is de-asserted. The pixel circuit also has a third transistor 190 controlled by the second scan signal coupled to a data line 120 and a source/drain 132 of the driver transistor 130.

A disadvantage of conventional pixel circuits is that they must use five transistors (transistors 110, 130, 160, 170, and 190). These transistors reduce the aperture ratio of the pixel circuit.

According to an embodiment of the invention, the pixel circuit has a light emitting diode, a first switch, a driving transistor, a capacitor and a second switch. A first end of the first switch is coupled to the light emitting diode, wherein the first switch is controlled by the first scan signal. A source/drain of the driving transistor is coupled to the first power terminal and the second terminal of the first switch, respectively. The capacitive coupling drives the gate of the transistor and the second power supply terminal. When the second scan signal is active, the second switch is coupled to the second end of the first switch and the capacitor, and is coupled to the gate and the source/drain of the driving transistor.

In accordance with another embodiment of the present invention, a pixel circuit has a drive transistor, a light emitting diode, and a capacitor. The light emitting diode has a cathode coupled to the first power terminal. The capacitor is coupled between the gate of the driving transistor and the second power terminal. In the pre-charging phase, the first source/drain of the driving transistor is coupled to the anode of the light-emitting diode, and the second source/drain of the driving transistor is coupled to receive a data signal. During the programming phase, the first source/drain of the drive transistor is removed from the anode of the light-emitting diode and the second source/drain of the drive transistor is coupled to receive a data signal. In the display phase, the first source/drain of the driving transistor is coupled to the anode of the light emitting diode, and the second source/drain of the driving transistor is coupled to the first power terminal.

According to another embodiment of the present invention, a pixel circuit has an organic light emitting diode, a first switch, a driving transistor, a capacitor, and a switching component unit. A first end of the first switch is coupled to the light emitting diode, wherein the first switch is controlled by the first scan signal. A first source/drain of the drive transistor is coupled to the second end of the first switch. The capacitor is coupled between the gate of the driving transistor and a power terminal. When the second scan signal is valid, the switch component unit is coupled to the second end of the first switch and the capacitor, coupled to the gate and the source/drain of the driving transistor, and coupled to the source of the driving transistor/ Bungee and power supply.

Please refer to FIG. 2A, which illustrates an organic light emitting diode pixel circuit according to an embodiment of the invention. The pixel circuit is a voltage type compensation pixel circuit. The pixel circuit has an organic light emitting diode (OLED) 280, a first switch 270, a driving transistor 230, a capacitor 250, and a second switch 210. The first end 276 of the first switch 270 is coupled to the light emitting diode 280, wherein the first switch 270 is controlled by a first scan signal (SCAN1). Source/drain 232 and 236 of drive transistor 230 are coupled to first power terminal 240 and second terminal 272 of first switch 270, respectively. The capacitor 250 is coupled to drive the gate 234 of the transistor 230 and the second power terminal 260. When the second scan signal (SCAN2) is active, the second switch 210 is coupled to the second end 272 of the first switch 270 and the capacitor 250, and is coupled to the gate 234 and the source/drain 236 of the driving transistor 230. .

The pixel circuit has a third switch 290 controlled by a second scan signal to couple the data line 220 to the source/drain 232 of the drive transistor 230. Therefore, when the second scan signal is active, the data signal from the data line 220 is transmitted to the pixel circuit.

Fig. 2B is a diagram showing signal waveforms in accordance with an embodiment of Fig. 2A of the present invention. The voltages of the first power supply terminal 240 and the second power supply terminal 260 are provided by a gate driver. In the pre-charging phase and the display phase, the first scan signal turns on the first switch 270 and the first switch 270 turns off during the programming phase. In the pre-charging phase and the program planning phase, the second scan signal turns on the second switch 210 and turns off the second switch 210 in the display phase.

When the third switch is turned on (eg, during the pre-charge and planning phase), the first power supply terminal 240 is floating (high impedance) and the second power supply terminal 260 is at a fixed voltage. In the pre-charging phase and the program planning phase, it is easier to write the data signal to the pixel circuit. Moreover, the pixel circuit does not require an additional reset signal, making the writing of the data signal easier.

The first switch 270, the second switch 210, and the third switch 290 can be implemented with a transistor. As in the embodiment shown in FIG. 2A, the first switch 270, the second switch 210, and the third switch 290 use a P-type MOS transistor. If the switches 270, 210, and 290 are to use an N-type MOS transistor, the above control signals must be inverted.

Compared with the conventional pixel circuit shown in Fig. 1, the number of transistors of this embodiment is reduced to four (switches 270, 210, 290 and driving transistor 230), and the aperture ratio of each pixel circuit is thus increased.

3A-3C illustrate the organic light emitting diode pixel circuits in the pre-charging, programming, and display stages, respectively, in accordance with an embodiment of the present invention. The pixel circuit operates sequentially in the pre-charging phase, the program planning phase, and the display phase. The pixel circuit has a light emitting diode (OLED) 380, a driving transistor 330, and a capacitor 350. In the precharge (Fig. 3A) and display (Fig. 3C) stages, the first source/drain 336 of the drive transistor 330 is coupled to the LED 380 and removed during the programming phase (Fig. 3B). Coupling with the light emitting diode 380. In the display phase, the second source/drain 332 of the drive transistor 330 is coupled to the first power supply terminal 340. In the pre-charge phase and the program planning phase, capacitor 350 is coupled to the first source/drain 336, and only the coupling with the first source/drain 336 is removed during the display phase. The capacitor 350 is also coupled between the gate 334 of the drive transistor 330 and the second power terminal 360.

In the pre-charge and programming phase, the switch 390 of the pixel circuit is coupled between the data line 320 and the second source/drain 332. Therefore, in the pre-charging and programming stages, the data signal of the data line 320 is transmitted to the pixel circuit. Switch 390 can be implemented with a transistor.

In other words, the cathode of the organic light emitting diode 380 is coupled to the first power terminal 340. Capacitor 350 is coupled between the gate of drive transistor 330 and second power supply terminal 360. In the pre-charging stage (Fig. 3A), the first source/drain 336 of the driving transistor 330 is coupled to the anode of the organic light-emitting diode 380, and the second source/drain 332 of the driving transistor 330 is coupledly received. A data signal. In the programming stage (FIG. 3B), the first source/drain 336 of the drive transistor 330 removes the coupling with the anode of the organic light-emitting diode 380, and drives the second source/汲 of the transistor 330. The pole 332 is coupled to receive a data signal. In the display phase (FIG. 3C), the first source/drain 336 of the drive transistor 330 is coupled to the anode of the organic light-emitting diode 380, and the second source/drain 332 of the drive transistor 330 is coupled to the first A power terminal 340.

The voltages of the first power terminal 340 and the second power terminal 360 are provided by a gate driver. In the pre-charging and programming phase, the first power supply terminal 340 (e.g., the second source/drain 332 of the drive transistor 330) is floating, and the voltage of the second power supply terminal 360 is a fixed voltage. Therefore, it is easier to write the data signal to the pixel circuit during the pre-charging and programming stages.

Please refer to FIG. 4A, which illustrates an organic light emitting diode pixel circuit according to another embodiment of the present invention. The pixel circuit has an organic light emitting diode 280, a first switch 270, a driving transistor 230, a capacitor 250 and a switch component unit. The first end 276 of the first switch 270 is coupled to the light emitting diode 280, wherein the first switch is controlled by the first scan signal. The first source/drain 236 of the drive transistor 230 is coupled to the second end 272 of the first switch 270. Capacitor 250 is coupled between gate 234 of drive transistor 230 and power terminal 460. The switch assembly unit has switches 210 and 440. When the second scan signal is valid, the switches 210 and 440 are respectively coupled to the second end 272 of the first switch 270 and the capacitor 250, coupled to the gate 234 and the source/drain 236 of the driving transistor 230, and the coupled connection. The source/drain 232 of the transistor 230 is driven to the power supply terminal 460.

The difference between the embodiment shown in FIGS. 2A and 4A is that the switch assembly unit shown in FIG. 4A has a power switch 440 coupled between the source/drain 232 of the drive transistor 230 and the power supply terminal 460. This power switch 440 is controlled by a second scan signal. Therefore, when the second scan signal is inactive, the power supply terminal 460 is floating.

The power switch 440 is disposed within the gate driver 400. Therefore, many pixel circuits can share the same power switch 440 as compared to the conventional FIG.

From the above, it is known that the embodiment of the present invention has a voltage compensation function and does not require an additional reset signal. Moreover, according to the design and operation, the pixel circuit can achieve a higher aperture ratio.

Although the present invention has been described above in terms of a preferred embodiment, it is not intended to limit the invention, and it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

110. . . Second transistor

120. . . Data line

130. . . Drive transistor

132. . . Source/drain of 130

134. . . Gate of 130

136. . . Source/drain of 130

140. . . Power terminal

150. . . capacitance

160. . . Transistor

170. . . First transistor

172. . . Source/drain of 170

176. . . Source/drain of 170

180. . . Organic light-emitting diode

190. . . Third transistor

210. . . Second switch

220. . . Data line

230. . . Drive transistor

232. . . 230 source/drain

234. . . Gate of 230

236. . . 230 source/drain

240. . . First power terminal

250. . . capacitance

260. . . Second power terminal

270. . . First switch

272. . . Second end of the first switch

276. . . First end of the first switch

280. . . Organic light-emitting diode

290. . . Third switch

320. . . Data line

330. . . Drive transistor

332. . . Source/drain of 330

334. . . Gate of 330

336. . . Source/drain of 330

340. . . First power terminal

350. . . capacitance

360. . . Second power terminal

380. . . Organic light-emitting diode

390. . . switch

400. . . Gate driver

440. . . switch

460. . . Power terminal

The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt;

2A is a circuit diagram of an organic light emitting diode pixel according to an embodiment of the invention.

Fig. 2B is a diagram showing signal waveforms of an embodiment shown in Fig. 2A of the present invention.

FIG. 3A is a circuit diagram of an organic light emitting diode pixel in a precharge phase thereof according to an embodiment of the invention.

FIG. 3B is a circuit diagram of an organic light emitting diode pixel according to an embodiment of the invention.

FIG. 3C is a circuit diagram of an organic light emitting diode pixel according to an embodiment of the invention.

4A is a circuit diagram of an organic light emitting diode pixel according to another preferred embodiment of the present invention.

210. . . Second switch

220. . . Data line

230. . . Drive transistor

232. . . Drive the source/drain of the transistor

234. . . Driving the gate of the transistor

236. . . Drive the source/drain of the transistor

240. . . First power terminal

250. . . capacitance

260. . . Second power terminal

270. . . First switch

272. . . Second end of the first switch

276. . . First end of the first switch

280. . . Organic light-emitting diode

290. . . Third switch

Claims (16)

A pixel circuit comprising: a light emitting diode; a first switch having a first end coupled to the light emitting diode, wherein the first switch is controlled by a first scan signal; a driving transistor having The source/drain is coupled to a first power terminal and a second terminal of the first switch; a capacitor coupled between a gate of the driving transistor and a second power terminal; and a second switch When the second scan signal is valid, the second switch is coupled to the second end of the first switch and the capacitor, and coupled to the gate and the source/drain of the driving transistor; And a third switch coupled between the data line and the source/drain by the second scan signal, wherein the first power terminal is floating when the third switch is turned on. The pixel circuit of claim 1, wherein the voltage of the first power terminal and the second power terminal is provided by a gate driver. The pixel circuit of claim 1, wherein the voltage of the second power terminal is a fixed voltage. The pixel circuit of claim 1, wherein the first The switch, the second switch, and the third switch are transistors. A pixel circuit includes: a driving transistor; a light emitting diode having a cathode coupled to a first power terminal; and a capacitor connected to one of the driving transistor and a second power terminal Wherein a first source/drain is coupled to one of the anodes of the light-emitting diode and a second source/drain is coupled to receive one of the drive transistors a data signal; in a programming stage, the first source/drain of the driving transistor is removed from the anode of the LED, and the second source/汲 of the driving transistor The pole coupling receives a data signal; and in a display phase, the first source/drain of the driving transistor is coupled to the anode of the light emitting diode, and the second source/turn of the driving transistor The pole is coupled to the second power terminal. The pixel circuit of claim 5, further comprising a switch coupled between a data line and the second source/drain during the pre-charging phase and the programming phase. The pixel circuit of claim 5, wherein the voltage of the first power terminal and the second power terminal is provided by a gate driver. For example, the pixel circuit described in claim 6 of the patent scope, wherein the opening When the switch is turned on, the first power terminal is floating. The pixel circuit of claim 6, wherein the switch is a transistor. A pixel circuit includes: an organic light emitting diode; a first switch having a first end coupled to the light emitting diode, wherein the first switch is controlled by a first scan signal; and a driving transistor Having a first source/drain coupled to a second end of the first switch; a capacitor coupled between a gate of the drive transistor and a power terminal; and a switch component unit, wherein When the second scan signal is valid, the switch component unit is coupled to the second end of the first switch and the capacitor, coupled to the gate of the driving transistor and the source/drain, and coupled to the capacitor Drive the other source/drain of the transistor to the power supply terminal. The pixel circuit of claim 10, further comprising a second switch controlled by the second scan signal coupled between a data line and the source/drain. The pixel circuit of claim 10, wherein the voltage of the power supply terminal is provided by a gate driver. The pixel circuit of claim 10, wherein the switch component unit comprises a power switch coupled between the source/drain of the driving transistor and the power terminal. The pixel circuit of claim 13, wherein the power switch is controlled by the second scan signal. The pixel circuit of claim 14, wherein the power switch is disposed in the gate driver. The pixel circuit of claim 10, wherein the first switch and the switch assembly unit comprise a transistor.