CN102832229B - Pixel circuit, driving method and display device of light emitting device - Google Patents
Pixel circuit, driving method and display device of light emitting device Download PDFInfo
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- CN102832229B CN102832229B CN201210320564.4A CN201210320564A CN102832229B CN 102832229 B CN102832229 B CN 102832229B CN 201210320564 A CN201210320564 A CN 201210320564A CN 102832229 B CN102832229 B CN 102832229B
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Abstract
The invention discloses a pixel circuit, a driving method and a display device of a light emitting device, avoiding the attenuation of an OLED (organic light emitting diode). In the circuit, a source of a switch transistor is connected with a line data wire; a grid is connected with a row scanning line; a drain is connected with a first end of a first storage capacitor; a second end of the first storage capacitor is connected with a first end of a power supply wire; a source of a driving transistor is connected with the first end of the power supply wire; the grid is connected wit the first end of the first storage capacitor; the drain is connected with the first end of the OLED; a source of a first compensating transistor is connected with the first end of the first storage capacitor; a grid of the first compensating transistor is connected with a light emitting control wire; a drain of the first compensating transistor is connected with a source of the second compensating transistor and the first end of the OLED; a grid of the second compensating transistor is connected with the row scanning line; and a drain of the second compensating transistor is connected with second end of the OLED and the second end of the power supply wire. The display device comprises a pixel circuit of the light emitting device.
Description
Technical Field
The invention relates to the technical field of display, in particular to a pixel circuit of a light-emitting device, a driving method and a display device.
Background
The light emitting element of an active light emitting diode display (AMOLED) is an Organic Light Emitting Diode (OLED), and the emission luminance thereof is proportional to the magnitude of a driving current supplied to the OLED device, so that a large driving current is required to achieve an optimal display effect. The low-temperature polysilicon backplane technology is the best choice for the AMOLED display backplane technology because it can provide higher mobility.
The threshold voltage shift inherent in the ltps technology causes non-uniformity of the driving current generated by the pixel circuit, and thus non-uniformity of the display brightness. In order to effectively compensate the shift of the threshold voltage of the Thin Film Transistor (TFT), a compensation technique is often introduced in circuit design, so as to obtain better display brightness uniformity.
However, OLED devices have their own lifetime problem, i.e. the electrical performance is degraded with increasing lifetime. Therefore, during the use process, the voltage drop on the OLED device increases, which means that the same driving voltage is used but different driving currents are generated, resulting in the reduction of the luminance of the OLED device. Because the performance of the OLED device on each pixel point is not completely the same, the brightness change of the OLED device on each pixel point is different, and finally the display brightness is not uniform.
Disclosure of Invention
The embodiment of the invention provides a pixel circuit of a light-emitting device, a driving method and a display device, which are used for realizing the compensation of the attenuation of an organic light-emitting diode (OLED) in the pixel circuit of the light-emitting device, so that the uneven display brightness caused by different brightness changes of the OLED devices of all pixel points is avoided.
The embodiment of the invention provides a pixel circuit of a light-emitting device, which comprises:
the OLED driving circuit comprises a column data line, a row scanning line, a switching transistor, a first storage capacitor, a driving transistor, a first end of a power line, a second end of the power line, a first compensation transistor, a second compensation transistor, an Organic Light Emitting Diode (OLED) and an OLED light emitting control line; wherein,
the source electrode of the switch transistor is connected with the column data line, the grid electrode of the switch transistor is connected with the row scanning line, the drain electrode of the switch transistor is connected with the first end of the first storage capacitor, and the second end of the first storage capacitor is connected with the first end of the power line;
the source electrode of the driving transistor is connected with the first end of the power line, the grid electrode of the driving transistor is connected with the first end of the first storage capacitor, and the drain electrode of the driving transistor is connected with the first end of the OLED;
the source electrode of the first compensation transistor is connected with the first end of the first storage capacitor, the grid electrode of the first compensation transistor is connected with the OLED light-emitting control line, the drain electrode of the first compensation transistor is connected with the source electrode of the second compensation transistor and the first end of the OLED, the grid electrode of the second compensation transistor is connected with the row scanning line, and the drain electrode of the first compensation transistor is connected with the second end of the OLED and the second end of the power line.
A driving method of a pixel circuit of a light emitting device, comprising the steps of:
when the row scanning line signal is effective and the OLED light-emitting control line signal is ineffective, the switch transistor is conducted, the first compensation transistor is disconnected, and the second compensation transistor is conducted; wherein,
the switching transistor is conducted, and column data line signal voltage is written into the first end of the first storage capacitor;
the second compensation transistor is conducted to shield the OLED voltage drop, and meanwhile, the first compensation transistor is disconnected;
when the OLED light-emitting control line signal is effective and the row scanning line signal is ineffective, the switch transistor is switched off, the first compensation transistor is switched on, and the second compensation transistor is switched off; wherein,
the second compensation transistor is disconnected, the first compensation transistor is connected, the voltage drop of the OLED is led into the first end of the first storage capacitor and the source electrode of the driving transistor, the voltage of the source electrode and the gate electrode meets the driving condition, and the drain electrode of the driving transistor outputs constant current to drive the OLED to emit light.
The display device provided by the embodiment of the invention comprises the pixel circuit of the light-emitting device.
The pixel circuit, the display device and the driving method of the light-emitting device provided by the embodiment of the invention solve the problem of different voltage drops on the OLED due to the attenuation of the electrical performance of the OLED, thereby solving the problem of non-uniform display brightness of the OLED and improving the display uniformity of the light-emitting device.
Drawings
Fig. 1 is a pixel circuit of a light emitting device according to an embodiment of the present invention;
fig. 2 is a timing diagram of control signals of a pixel circuit of the light emitting device in fig. 1;
fig. 3 is a pixel circuit of another light emitting device according to an embodiment of the present invention;
fig. 4 is a timing diagram of control signals of a pixel circuit of the light emitting device in fig. 3;
fig. 5 is a pixel circuit of a further light emitting device according to an embodiment of the present invention;
fig. 6 is a timing diagram of control signals of a pixel circuit of the light emitting device in fig. 5;
FIG. 7 is a diagram illustrating the operation of the pixel circuit of the light emitting device of FIG. 3 in a first phase of the timing diagram of the control signals of FIG. 2;
FIG. 8 is an operating state diagram of the pixel circuit of the light emitting device of FIG. 3 at a second stage of the timing diagram of the control signals of FIG. 2;
fig. 9 is an operation state diagram of the pixel circuit of the light emitting device in fig. 3 at a third stage of the control signal timing diagram of fig. 2.
Detailed Description
The embodiment of the invention provides a pixel circuit of a light-emitting device, a driving method and a display device, which are used for realizing the compensation of the attenuation of an organic light-emitting diode (OLED) in the pixel circuit of an active light-emitting device, so that the uneven display brightness caused by different brightness changes of the OLED devices of all pixel points is avoided.
The following detailed description of embodiments of the invention is provided in connection with the accompanying drawings and examples.
Example 1
Referring to fig. 1, a pixel circuit of a light emitting device according to an embodiment of the present invention includes:
a switching transistor 101, a column data line 102, a row scanning line 103, a first storage capacitor 104, a power line first end 105, a driving transistor 106, a first compensation transistor 107, an OLED light emission control line 108, a second compensation transistor 109, an OLED110, and a power line second end 111; and; wherein,
the source of the switching transistor 101 is connected to the column data line 102, the gate is connected to the row scan line 103, the drain is connected to the first end of the first storage capacitor 104, and the second end of the first storage capacitor 104 is connected to the first end 105 of the power line;
the source of the driving transistor 106 is connected to the first end of the power line 105, the gate is connected to the first end of the first storage capacitor 104, and the drain is connected to the first end of the OLED 110;
the source of the first compensation transistor 107 is connected to the first end of the first storage capacitor 104, the gate is connected to the OLED light emission control line 108, the drain is connected to the source of the second compensation transistor 109 and the first end of the OLED110, the gate of the second compensation transistor 109 is connected to the row scan line 103, and the drain is connected to the second end of the OLED110 and the second end 111 of the power line.
Preferably, the driving transistor 106 is a P-type thin film transistor TFT, the first terminal of the OLED110 is an anode of the OLED110, the second terminal of the OLED110 is a cathode of the OLED110, and the voltage VDD at the first terminal 105 of the power line is higher than the voltage VSS at the second terminal 111 of the power line.
Preferably, the switching transistor 101, the first compensation transistor 107 and the second compensation transistor 109 are P-type or N-type thin film transistors TFT.
Preferably, the capacitance of the first storage capacitor 104 is in the order of 10-13f。
The driving method of the pixel circuit of the light emitting device provided in embodiment 1 of the present invention is as follows:
referring to fig. 2, a timing diagram of a control signal of the pixel circuit of the active light emitting device is shown;
referring to fig. 1, in the first phase, phase t2, it is also referred to as the data write phase. When the row scanning signal 103 is at a low level, the switching transistor 101 is turned on, and the signal data provided by the column data line 102 is written into the pixel circuit, at this time, the first terminal a of the first storage capacitor 104 is connected to the first terminal a0The voltage at the point is Vdata, and the voltage is stored by the first storage capacitor 104. And at the same time, the second compensation transistor 109 is also in the on state, and the connection point B between the drain of the first compensation transistor 107 and the source of the second compensation transistor 1090The voltage of the point is the voltage VSS of the second end 111 of the power line, and the signal provided by the OLED light-emitting control line 108 is at a high level, then the first compensation transistor is turned off, thereby preventing the OLED from applying the voltage to the first end A of the first storage capacitor 1040The disturbance of the voltage of the point, that is, the voltage of the gate of the driving transistor DTFT106 is Vdata;
at stage t3, also referred to as the display stage. The line scanning signal 103 transitions to high, the switching transistor 101 is turned off, the signal provided by the OLED emission control line 108 is low, the first compensation transistor 107 is turned on, the voltage drop Voled across the OLED110 device is introduced, the source voltage of the DTFT106 is (Vdd-Voled), and A is at the same time0The voltage (Vss + Vdata-Voled) of the point is stored by the firstThe storage capacitor 104 holds, i.e., drives, the gate voltage of the transistor DTFT106, which ensures that the DTFT106 operates in the saturation region, and the drain current of the DTFT106 is at this time
W is the width of the channel of the DTFT106, L is the length of the channel, C is the capacitance between the channel and the gate, and μ is the carrier mobility of the channel, which are relatively fixed and independent of the voltage drop Voled across the OLED110 device, the voltage change across the OLED110 device does not affect the drain current of the DTFT106, i.e., the driving current of the pixel circuit, which flows into the OLED110, thereby lighting up the display.
It should be noted that in this embodiment, the driving transistor 106, the switching transistor 101, the first compensation transistor 107, and the second compensation transistor 109 are P-type thin film transistors TFT for example; of course, any or all of the transistors may be N-type thin film transistors TFT, and only the level signals of the transistors in the first stage and the second stage and the voltages of the first terminal and the second terminal of the power line are changed accordingly. The P-type thin film transistor TFT is turned on when the level is low, and the N-type thin film transistor TFT is turned on when the level is high. The rest of the embodiments are the same and are not described in detail.
Example 2
Referring to fig. 3, a pixel circuit of a light emitting device provided in embodiment 2 of the present invention includes:
a switch transistor S101, a column data line S102, a row scanning line S103, a first storage capacitor S104, a first end of a power line S105, a driving transistor S106, a first compensation transistor S107, an OLED light-emitting control line S108, a second compensation transistor 109, an OLED S110 and a second end of the power line S111; wherein,
the source of the switching transistor S101 is connected to the column data line S102, the gate is connected to the row scan line S103, the drain is connected to the first end of the first storage capacitor S104, and the second end of the first storage capacitor S104 is connected to the first end of the power line S105;
the source of the driving transistor S106 is connected to the first end of the power line S105, the gate is connected to the first end of the first storage capacitor S104, and the drain is connected to the first end of the OLED S110;
the source of the first compensation transistor S107 is connected to the first end of the first storage capacitor S104, the gate is connected to the OLED light emission control line S108, the drain is connected to the source of the second compensation transistor S109 and the first end of the OLED S110, the gate of the second compensation transistor S109 is connected to the row scan line S103, and the drain is connected to the second end of the OLEDs110 and the second end of the power line S111.
Preferably, the pixel circuit of the light emitting device further includes a second storage capacitor S112, a first end of which is connected to the drain of the switching transistor S101, and a second end of which is connected to the first end of the first storage capacitor S104, so as to ensure that the gate voltage of the driving transistor S106 is not attenuated by the leakage of the switching transistor;
preferably, the pixel circuit of the light emitting device further includes a third compensation transistor S113, a source of which is connected to the drain of the driving transistor S106, a gate of which is connected to the light emitting control line S108, and a drain of which is connected to the source of the second compensation transistor S109, so as to ensure that the OLEDS110 are driven when the driving current is stable;
preferably, the third compensation transistor S113 is a P-type or N-type thin film transistor TFT;
preferably, the pixel circuit of the light emitting device further includes an initialization transistor S114, an initialization line S115, and a reference power source S116;
the source electrode of the initialization transistor S114 is connected with the reference power supply S116, the grid electrode is connected with the first end of the initialization line S115, and the drain electrode is connected with the first end of the first storage capacitor S104;
preferably, the initialization transistor S114 is a P-type or N-type thin film transistor TFT;
preferably, the pixel circuit of the light emitting device further includes a fourth compensation transistor S117, a gate of the fourth compensation transistor S117 is connected to the row scanning line S103, a source is connected to the gate of the driving transistor S106, and a drain is connected to the drain of the driving transistor S106, for storing the threshold voltage of the driving transistor in advance in the first storage capacitor S104;
preferably, the fourth compensation transistor S117 is a P-type or N-type thin film transistor TFT;
preferably, the driving transistor S106 is a P-type thin film transistor TFT, the first terminal of the OLEDS110 is an anode of the OLEDS110, the second terminal of the OLEDS110 is a cathode of the OLEDS110, and the voltage VDD at the first terminal 105 of the power line is higher than the voltage VSS at the second terminal 111 of the power line;
preferably, the switching transistor S101, the first compensation transistor S107 and the second compensation transistor 109 are P-type or N-type thin film transistors TFT;
preferably, the capacitance values of the first storage capacitor S104 and the second storage capacitor S112 are in the order of 10-13f。
The embodiments of the present invention are provided for illustrating the present invention, but not for limiting the scope of the present invention, wherein the second storage capacitor 112, the third compensation transistor 113, the initialization transistor S114, the initialization line S115, the reference power source S116 and the fourth compensation transistor S117 do not necessarily exist in the pixel circuit of the active light emitting device at the same time, and the circuit including any one of them can achieve the object of the present invention.
The driving method of the pixel circuit of the active light emitting device provided in embodiment 2 of the present invention is as follows:
referring to fig. 4, a timing diagram of a control signal of the pixel circuit of the active light emitting device is shown;
referring to fig. 7, at stage t1, also referred to as an initialization stage. The initialization signal S115 is low, the initialization transistor S114 is turned on, Vref provided by the reference power source S116 is written into the point a1 at the first end of the first storage capacitor, and at this time, the voltage at the point C2 on the right side of the second storage capacitor S1112 is also Vref, thereby completing the initialization of the pixel state;
referring to fig. 8, at stage t2, also referred to as the data write phase. The initialization signal S115 jumps to a high level, the initialization transistor S114 is turned off, and the Vref voltage is held by the first storage capacitor S104. Meanwhile, when the row scanning signal S103 is at a low level, the switching transistor S101 is turned on, the signal data provided by the column data line S102 is written into the pixel circuit, and the right C of the second storage capacitor S112 is at this time2The dot voltage is (Vdata + Vref). Meanwhile, since the row scanning signal S103 is asserted, the fourth compensation transistor S117 is turned on, and the gate terminal and the drain terminal of the driving transistor DTFT S106 are connected to form a diode-connection, and the threshold voltage Vth, Vth is recorded and maintained by the first storage capacitor S104. Taken together, at this time A1The dot voltage, i.e., the voltage of the gate of the driving transistor DTFT S106 is (Vdata + Vref-Vth), and the voltage is stored by the first storage capacitor S104. At this stage, the signal provided by the OLED light-emitting control line S108 is at a high level, so that the third compensation transistor S113 is turned off, and the writing of data into the pixel does not affect the light-emitting state of the OLED110, thereby avoiding display flicker. While the second compensation transistor S109 is also in the on state, B1The voltage of the point is the voltage VSS of the second end S111 of the power line, and at the same time, the signal provided by the OLED light-emitting control line S108 is at a high level, the first compensation transistor is turned off, thereby preventing the OLED S110 from applying the voltage to the first end A of the first storage capacitor S1041The disturbance of the voltage of the point, that is, the voltage of the gate of the driving transistor DTFT S106 is (Vdata + Vref-Vth);
referring to fig. 9, at stage t3, also referred to as the display stage. The row scanning signal S103 jumps to a high level, and the switching transistor S101 and the fourth compensating transistor S117 are turned offWhen the signal provided by the OLED emission control line S108 is low, the first compensation transistor S107 is turned on, the third compensation transistor S113 is turned on, the voltage drop Voled across the OLED S110 device is introduced, and the source voltage of the DTFT S106 is (Vdd-Voled), and A is at the same time1The voltage (Vss + Vdata + Vref Vth-Voled) of the point is maintained by the first storage capacitor S104, i.e. the gate voltage of the driving transistor DTFT S106, which ensures that the DTFT S106 operates in the saturation region, and the drain current of the DTFT S106 is at this time
Where W is the width of the DTFTS106 channel, L is the length of the channel, C is the capacitance between the channel and the gate, and μ is the carrier mobility of the channel, all of which are relatively constant. The current value is independent of the threshold voltage Vth and the voltage drop Voled across the OLED S1110 device, and the drift of the threshold voltage Vth of the driving transistor DTFT S106 and the voltage change across the OLED S110 device do not affect the drain current of the DTFT S106, i.e., the driving current of the pixel circuit. Meanwhile, the signal provided by the OLED light-emitting control line S108 is active, the third compensation transistor S113 is turned on, and the pixel driving current flows into the OLED S110 through the third compensation transistor S113 to light up the display;
preferably, Vref is optionally grounded, to act as pair A1The reset of the point potential also compensates for the fluctuation of the pixel current caused by the IR drop of the power supply if there is a voltage drop, i.e., IR drop, caused by the wire resistance or parasitic resistance at the first end S105 of the power supply line, and the value of Vref is adjusted to cancel the voltage drop caused by the IR drop.
Example 3
Referring to fig. 5, a pixel circuit of an active light emitting device provided in embodiment 3 of the present invention includes:
a switch transistor S201, a column data line S202, a row scan line S203, a first storage capacitor S204, a first end of a power line S205, a driving transistor S206, a first compensation transistor S207, an OLED light emission control line S208, a second compensation transistor S209, an OLEDs210, and a second end of the power line S211; (ii) a Wherein,
the source of the switching transistor S201 is connected to the column data line S202, the gate is connected to the row scan line S203, the drain is connected to the first end of the first storage capacitor S204, and the second end of the first storage capacitor S104 is connected to the first end of the power line S205;
the source of the driving transistor S206 is connected to the first end of the power line S205, the gate is connected to the first end of the first storage capacitor S204, and the drain is connected to the first end of the OLED S210;
the source of the first compensation transistor S207 is connected to the first end of the first storage capacitor S104, the gate is connected to the OLED light emission control line S208, the drain is connected to the source of the second compensation transistor S109 and the first end of the OLED S210, the gate of the second compensation transistor S209 is connected to the row scan line S203, and the drain is connected to the second end of the OLEDs210 and the second end of the power line S211;
preferably, the pixel circuit of the light emitting device further includes a second storage capacitor S212, a first end of which is connected to the drain of the switching transistor S201, and a second end of which is connected to the first end of the first storage capacitor S204, so as to ensure that the gate voltage of the driving transistor S206 is not attenuated by the leakage of the switching transistor; preferably, the pixel circuit of the light emitting device further includes a third compensation transistor S213, a source thereof is connected to the drain of the driving transistor S206, a gate thereof is connected to the light emitting control line S208, and a drain thereof is connected to the source of the second compensation transistor S209, so as to ensure that the OLEDS210 are driven when the driving current is stable;
preferably, the third compensation transistor S213 is a P-type or N-type thin film transistor TFT;
preferably, the pixel circuit of the light emitting device further includes an initialization transistor S214, an initialization line S215, and a reference power source S216;
the source electrode of the initialization transistor S214 is connected with the reference power supply S216, the grid electrode is connected with the first end of the initialization line S215, and the drain electrode is connected with the first end of the first storage capacitor S204;
preferably, the initialization transistor S214 is a P-type or N-type thin film transistor TFT;
preferably, the pixel circuit of the light emitting device further includes a fourth compensation transistor S217, a gate of the fourth compensation transistor S217 is connected to the row scanning line S203, a source is connected to the gate of the driving transistor S206, and a drain is connected to the drain of the driving transistor S206, for storing the threshold voltage of the driving transistor in advance in the first storage capacitor S204;
preferably, the fourth compensation transistor S217 is a P-type or N-type thin film transistor TFT;
preferably, the driving transistor S206 is an N-type thin film transistor TFT, the first terminal of the OLEDS110 is a cathode of the OLEDS210, the second terminal of the OLEDS110 is an anode of the OLEDS110, and the voltage VSS at the first terminal S205 of the power line is lower than the voltage VDD at the second terminal S211 of the power line.
Preferably, the switching transistor S201, the first compensation transistor S207 and the second compensation transistor S209 are P-type or N-type thin film transistors TFT.
Preferably, the capacitance values of the first storage capacitor S204 and the second storage capacitor S212 are in the order of 10-13f。
The embodiments of the present invention are provided for illustrating the present invention, but not for limiting the scope of the present invention, wherein the second storage capacitor 212, the third compensation transistor 213, the initialization transistor S214, the initialization line S215, the reference power source S216 and the fourth compensation transistor S217 are not necessarily simultaneously present in the pixel circuit of the active light emitting device, and any one of the circuits may be included to achieve the object of the present invention.
The driving method of the pixel circuit of the active light emitting device provided in embodiment 3 of the present invention is as follows: referring to fig. 6, a timing diagram of a control signal of the pixel circuit of the light emitting device is shown;
referring to fig. 5, during the period t1, the initialization signal S215 is high, the initial transistor S214 is turned on, and Vref provided by the reference power source S216 is written into the first terminal a of the first storage capacitor2At this time, the right side C of the second storage capacitor S2122The voltage of the voltage is also Vref, and the initialization of the pixel state is completed;
in the stage t2, the initialization signal S215 jumps low, the initialization transistor S214 is turned off, and the Vref voltage is maintained by the first storage capacitor S204. Meanwhile, when the row scanning signal S203 is asserted, the switching transistor S201 is turned on, and the signal data provided by the column data line S202 is written into the pixel circuit, at this time, the right C of the second storage capacitor S112 is asserted2The voltage at the point is (Vdata + Vref). Meanwhile, since the row scanning signal S203 is at a high level, the fourth compensation transistor S217 is turned on, and the gate terminal and the drain terminal of the driving transistor DTFT S206 are connected to form a diode-connection, and the threshold voltage Vth, of the diode-connection is recorded and maintained by the first storage capacitor S204. Taken together, at this time A2The dot voltage, i.e., the voltage of the gate of the driving transistor DTFT S206 is (Vdata + Vref-Vth), and the voltage is stored by the first storage capacitor S204. At this stage, the signal provided by the OLED light-emitting control line S208 is at a low level, which ensures that the third compensation transistor S213 is turned off, and the writing of data into the pixel does not affect the light-emitting state of the OLED S210, thereby avoiding display flicker. While the second compensating transistor S209 is also in the conducting state, B2The voltage of the point is the voltage VDD of the second end S211 of the power line, and at the same time, the signal provided by the OLED light-emitting control line S208 is at a low level, the first compensation transistor is turned off, thereby preventing the OLED S110 from applying a voltage to the first storage capacitor S104One end A2The disturbance of the voltage of the point, that is, the voltage of the gate of the driving transistor DTFT S106 is (Vdata + Vref-Vth);
in the period t3, the line scanning signal S203 is at low level, the switching transistor S201 and the fourth compensation transistor S217 are turned off, the signal provided by the OLED emission control line S208 is at high level, the first compensation transistor S207 is turned on, the third compensation transistor S213 is turned on, the voltage drop Voled across the OLED S210 device is introduced, and the source voltage of the DTFT S206 is (Vss-Voled), and A is at the same time2The voltage (Vdd + Vdata + Vref Vth-Voled) of the point is maintained by the first storage capacitor S204, i.e. the gate voltage of the driving transistor DTFT S206, which ensures that the DTFT S206 operates in the saturation region, and the drain current of the DTFT S206 is at this time
Where W is the width of the DTFT S206 channel, L is the length of the channel, C is the capacitance between the channel and the gate, and μ is the carrier mobility of the channel, all of which are relatively constant. The current value is independent of the threshold voltage Vth and the voltage drop Voled across the OLED S210 device, and the drift of the threshold voltage Vth of the driving transistor DTFT S206 and the voltage change across the OLED S210 device do not affect the drain current of the DTFT S206, i.e., the driving current of the pixel circuit. Meanwhile, the signal provided by the OLED emission control line S208 is active, the third compensation transistor S213 is turned on, and the pixel driving current flows into the OLED S210 through the third compensation transistor S213, so as to turn on the display;
preferably, Vref is optionally grounded, to act as pair A2The reset of the point potential also compensates for the fluctuation of the pixel current caused by the IR drop of the power supply if there is a voltage drop caused by the wire resistance or parasitic resistance, i.e., IR drop, at the first end S205 of the power supply line, and the value of Vref is adjusted to cancel the voltage drop caused by IR drop.
The display device provided by the embodiment of the invention comprises the pixel circuit of any one of the light-emitting devices.
In summary, an embodiment of the present invention provides a pixel circuit of an active light emitting device, a driving method thereof, and a display apparatus, where the pixel circuit includes: the OLED driving circuit comprises a column data line, a row scanning line, a switching transistor, a first storage capacitor, a driving transistor, a first end of a power line, a second end of the power line, a first compensation transistor, a second compensation transistor, an Organic Light Emitting Diode (OLED) and an OLED light emitting control line; the source electrode of the switching transistor is connected with the column data line, the grid electrode of the switching transistor is connected with the row scanning line, the drain electrode of the switching transistor is connected with the first end of the first storage capacitor, and the second end of the first storage capacitor is connected with the first end of the power line; the source electrode of the driving transistor is connected with the first end of the power line, the grid electrode of the driving transistor is connected with the first end of the first storage capacitor, and the drain electrode of the driving transistor is connected with the first end of the OLED; the source electrode of the first compensation transistor is connected with the first end of the first storage capacitor, the grid electrode of the first compensation transistor is connected with the light-emitting control line, the drain electrode of the first compensation transistor is connected with the source electrode of the second compensation transistor and the first end of the OLED, the grid electrode of the second compensation transistor is connected with the row scanning line, and the drain electrode of the first compensation transistor is connected with the second end of the OLED and the second end of the power line. The display device comprises the pixel circuit of the light-emitting device. The pixel circuit of the light-emitting device, the driving method and the display device provided by the embodiment of the invention solve the problem of different voltage drops on the OLED due to the attenuation of the electrical performance of the OLED, thereby solving the problem of non-uniform display brightness of the OLED and further improving the display uniformity of the light-emitting device.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (17)
1. A pixel circuit of a light emitting device, the circuit comprising: the OLED driving circuit comprises a column data line, a row scanning line, a switching transistor, a first storage capacitor, a driving transistor, a first end of a power line, a second end of the power line, a first compensation transistor, a second compensation transistor, an Organic Light Emitting Diode (OLED) and an OLED light emitting control line; wherein,
the source electrode of the switch transistor is connected with the column data line, the grid electrode of the switch transistor is connected with the row scanning line, the drain electrode of the switch transistor is connected with the first end of the first storage capacitor, and the second end of the first storage capacitor is connected with the first end of the power line;
the source electrode of the driving transistor is connected with the first end of the power line, the grid electrode of the driving transistor is connected with the first end of the first storage capacitor, and the drain electrode of the driving transistor is connected with the first end of the OLED;
the source electrode of the first compensation transistor is connected with the first end of the first storage capacitor, the grid electrode of the first compensation transistor is connected with the light-emitting control line, the drain electrode of the first compensation transistor is connected with the source electrode of the second compensation transistor and the first end of the OLED, the grid electrode of the second compensation transistor is connected with the row scanning line, and the drain electrode of the first compensation transistor is connected with the second end of the OLED and the second end of the power line.
2. The pixel circuit of the light-emitting device according to claim 1, further comprising a second storage capacitor having a first terminal connected to the drain of the switching transistor and a second terminal connected to a first terminal of the first storage capacitor.
3. The pixel circuit of a light emitting device according to claim 1 or 2, further comprising a third compensation transistor having a source connected to the drain of the driving transistor, a gate connected to the emission control line, and a drain connected to the source of the second compensation transistor.
4. The pixel circuit of the light-emitting device according to claim 3, wherein the third compensation transistor is a P-type or N-type Thin Film Transistor (TFT).
5. The pixel circuit of a light-emitting device according to claim 1 or 2, further comprising an initialization transistor, an initialization line, and a reference power supply;
the source electrode of the initialization transistor is connected with the reference power supply, the grid electrode of the initialization transistor is connected with the first end of the initialization line, and the drain electrode of the initialization transistor is connected with the first end of the first storage capacitor; the second end of the initialization line is connected with the signal generator and provides an initialization signal for initializing the circuit state.
6. The pixel circuit of the light-emitting device according to claim 5, wherein the initialization transistor is a P-type or N-type Thin Film Transistor (TFT).
7. The pixel circuit of a light-emitting device according to claim 1 or 2, further comprising a fourth compensation transistor having a gate connected to the row scan line, a source connected to the gate of the driving transistor, and a drain connected to the drain of the driving transistor, for storing a threshold voltage of the driving transistor in advance in the first storage capacitor.
8. The pixel circuit of the light-emitting device according to claim 7, wherein the fourth compensation transistor is a P-type or N-type Thin Film Transistor (TFT).
9. The pixel circuit of the light emitting device according to claim 1, wherein the driving transistor is a P-type thin film transistor TFT, the first terminal of the OLED is an anode of the OLED, the second terminal of the OLED is a cathode of the OLED, and the voltage of the first terminal of the power line is higher than the voltage of the second terminal of the power line; or,
the driving transistor is an N-type Thin Film Transistor (TFT), the first end of the OLED is the cathode of the OLED, the second end of the OLED is the anode of the OLED, and the voltage of the first end of the power line is lower than the voltage of the second end of the power line.
10. The pixel circuit of the light-emitting device according to claim 1, wherein the switching transistor, the first compensation transistor, and the second compensation transistor are P-type or N-type Thin Film Transistors (TFTs).
11. The pixel circuit of the light-emitting device according to claim 2, wherein the first storage capacitor and the second storage capacitor are connected in seriesThe capacitance value of the second storage capacitor is of the order of 10-13f。
12. A display device comprising the pixel circuit of the light-emitting device according to any one of claims 1 to 11.
13. A method of driving the pixel circuit of claim 1, comprising the steps of:
when the row scanning line signal is effective and the OLED light-emitting control line signal is ineffective, the switch transistor is switched on, the first compensation transistor is switched off, and the second compensation transistor is switched on; wherein,
the switching transistor is conducted, and column data line signal voltage is written into the first end of the first storage capacitor;
the second compensation transistor is conducted to shield the OLED voltage drop, and meanwhile, the first compensation transistor is disconnected;
when the OLED light-emitting control line signal is effective and the row scanning line signal is ineffective, the switch transistor is switched off, the first compensation transistor is switched on, and the second compensation transistor is switched off; wherein,
the second compensation transistor is disconnected, the first compensation transistor is connected, the voltage of a source electrode and a grid electrode meets the driving condition, and the drain electrode of the driving transistor outputs constant current to drive the OLED to emit light.
14. A method according to claim 13, wherein when the pixel circuit further comprises a second storage capacitor connected between the drain of the switching transistor and the first terminal of the first storage capacitor, the method further comprises:
when the row scanning line signal is effective, the signal voltage of the column data line is stored in the second storage capacitor.
15. The method of claim 13, wherein when the pixel circuit further comprises a third compensation transistor connected between the drain of the drive transistor and the first terminal of the OLED, the method further comprises:
when the row scanning line signal is effective and the OLED light-emitting control line signal is ineffective, the third compensation transistor is disconnected, and the drain electrode of the driving transistor is disconnected with the OLED.
16. The method of claim 13, wherein when the pixel circuit further comprises an initialization transistor, an initialization line, and a reference power supply, wherein the initialization transistor has a source connected to the reference power supply, a gate connected to the first end of the initialization line, and a drain connected to the first end of the first storage capacitor, the method further comprises:
before the column data signal is written in, when the initialization line signal is effective, the initialization transistor is conducted, and the reference voltage is written in the first end of the first storage capacitor.
17. The method of claim 13, wherein when the pixel circuit further comprises a fourth compensation transistor connected between the gate and the drain of the drive transistor, the method further comprises:
when the row scanning line signal is effective and the OLED light-emitting control line signal is ineffective, the fourth compensation transistor is conducted, and the threshold voltage of the driving transistor is introduced to the first end of the first storage capacitor.
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