CN102708789A - Pixel unit driving circuit and method, pixel unit and display device - Google Patents
Pixel unit driving circuit and method, pixel unit and display device Download PDFInfo
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- CN102708789A CN102708789A CN2011103939431A CN201110393943A CN102708789A CN 102708789 A CN102708789 A CN 102708789A CN 2011103939431 A CN2011103939431 A CN 2011103939431A CN 201110393943 A CN201110393943 A CN 201110393943A CN 102708789 A CN102708789 A CN 102708789A
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Abstract
The invention provides a pixel unit driving circuit and method, a pixel unit and a display device. The pixel unit driving circuit comprises a driving thin film transistor, a first switching element, a storage capacitor and a driving control unit, wherein the source electrode of the driving thin film transistor is connected with the high-level output end of a driving power supply; the grid electrode of the driving thin film transistor is connected with the first end of the storage capacitor; the drain electrode of the driving thin film transistor is connected with the anode of an organic light emitting diode (OLED) by the first switching element; the second end of the storage capacitor is respectively connected with the source electrode and the data line of the driving thin film transistor by the driving control unit; and the grid electrode of the driving thin film transistor is respectively connected with low-level output end of the driving power supply and the drain electrode of the driving thin film transistor by the driving control unit. According to the pixel unit driving circuit disclosed by the invention, the storage capacitor is controlled to charge and discharge so as to control that the driving thin film transistor works in a saturated zone and the grid source voltage of the driving thin film transistor compensates the threshold voltage of the driving thin film transistor, and the problems of uneven OLED panel luminance and luminance attenuation are solved.
Description
Technical field
The present invention relates to the organic light emitting display field, relate in particular to pixel cell driving circuit and method, pixel cell and the display device of a kind of AMOLED (active matrix organic light-emitting diode).
Background technology
Existing pixel cell driving circuit is as shown in Figure 1; This driving circuit comprises two transistors and an electric capacity; One of them transistor is a switch transistor T 1, and the sweep signal Vscan that is exported by sweep trace controls, and purpose is the input for the data-signal Vdata on the control data line Data; Another transistor is driving tube T2, and OLED is luminous in control; Cs is a MM CAP, is used for keeping the voltage that driving tube T2 is applied in non-scan period, and foregoing circuit is called as 2T1C pixel cell driving circuit.
AMOLED (Active Matrix Organic Light Emitting Diode; Active matrix organic light-emitting diode) can luminously be to drive by the electric current that driving transistors produces when the state of saturation; Because when importing identical gray scale voltage; The different threshold voltage of said driving transistors can cause producing different drive currents, causes the inconsistency of electric current.And the non-constant of homogeneity of LTPS (low temperature polycrystalline silicon technology) processing procedure upper threshold voltage Vth, Vth also has drift simultaneously, and therefore the brightness uniformity of traditional 2T1C pixel cell driving circuit is very poor always.
Summary of the invention
Fundamental purpose of the present invention is to provide a kind of pixel cell driving circuit and method, pixel cell and display device, to improve the oled panel luminance uniformity.
In order to achieve the above object, the invention provides a kind of pixel cell driving circuit, be used for driving OLED, said pixel cell driving circuit comprises drive thin film transistors, first on-off element, MM CAP and driving control unit;
Said drive thin film transistors, source electrode is connected with the high level output terminal of driving power, and grid is connected with first end of said MM CAP, and drain electrode is connected with the anode of said OLED through said first on-off element;
Second end of said MM CAP is connected with data line with the source electrode of said drive thin film transistors respectively through said driving control unit;
The grid of said drive thin film transistors is connected with the low level output terminal of said driving power and the drain electrode of said drive thin film transistors respectively through said driving control unit;
Said driving control unit; Be used for discharging and recharging through controlling said MM CAP; The gate source voltage of the said drive thin film transistors compensation Vth to control that said drive thin film transistors works in the saturation region, wherein, Vth is the threshold voltage of said drive thin film transistors.
During enforcement, said drive thin film transistors is a p type thin film transistor (TFT).
During enforcement, said first on-off element is a p type thin film transistor (TFT);
Said first on-off element, grid is connected with first control line, and source electrode is connected with the drain electrode of said drive thin film transistors, and drain electrode is connected with the anode of said OLED.
During enforcement, said driving control unit comprises second switch element, the 3rd on-off element, the 4th on-off element and the 5th on-off element, wherein,
Be connected with the second switch element between the low level output terminal of said driven effect transistor drain and said driving power;
Be connected with the 3rd on-off element between second end of the source electrode of said drive thin film transistors and said MM CAP;
Be connected with the 4th on-off element between the grid of said drive thin film transistors and the drain electrode of said drive thin film transistors;
Be connected with the 5th on-off element between second end of said MM CAP and the data line.
During enforcement, said second switch element, said the 3rd on-off element, said the 4th on-off element and said the 5th on-off element are p type thin film transistor (TFT);
Said first on-off element, grid is connected with first control line, and source electrode is connected with the drain electrode of said drive thin film transistors, and drain electrode is connected with the anode of said OLED;
Said second switch element, grid is connected with second control line, and source electrode is connected with the drain electrode of said drive thin film transistors, and drain electrode is connected with the low level output terminal of said driving power;
Said the 3rd on-off element, grid is connected with the 3rd control line, and source electrode is connected with second end of said MM CAP, and drain electrode is connected with the source electrode of said drive thin film transistors;
Said the 4th on-off element, grid is connected with the sweep trace that is used for transmission of control signals, and source electrode is connected with the grid of said drive thin film transistors, and drain electrode is connected with the drain electrode of said drive thin film transistors;
Said the 5th on-off element, grid is connected with said sweep trace, and source electrode is connected with said data line, and drain electrode is connected with second end of said MM CAP.
The present invention also provides a kind of pixel cell driving method, and it is applied to above-mentioned pixel cell driving circuit, and said pixel cell driving method may further comprise the steps:
The pixel charge step: driving control unit control store electric capacity is recharged;
The pixel discharge step: said driving control unit is controlled said MM CAP through drive thin film transistors discharge, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of driving OLED: said driving control unit is controlled said drive thin film transistors and is worked in the saturation region; And the voltage difference of controlling said MM CAP two ends is constant; So that it is the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, luminous through said drive thin film transistors driving OLED.
During enforcement, said pixel charge step comprises: first on-off element breaks off the drain electrode of said drive thin film transistors and being connected of said OLED; Being connected of second end of said driving control unit conducting data line and said MM CAP; The grid of the said drive thin film transistors of conducting is connected with the drain electrode of said drive thin film transistors; Being connected of the low level output terminal of the drain electrode of the said drive thin film transistors of conducting and said driving power; Break off being connected of second end of source electrode and the said MM CAP of said drive thin film transistors, control said MM CAP and be recharged;
Said pixel discharge step comprises: the drain electrode that said driving control unit is broken off said drive thin film transistors is connected with the low level output terminal of said driving power; Controlling said MM CAP and discharge through said drive thin film transistors, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of said driving OLED comprises: the drain electrode of the said drive thin film transistors of the said first on-off element conducting is connected with said OLED's; Being connected of second end of the said MM CAP of said driving control unit conducting and the source electrode of said drive thin film transistors; Break off being connected of second end of said data line and said MM CAP; Break off being connected of drain electrode of grid and the said drive thin film transistors of said drive thin film transistors; Control said drive thin film transistors and work in the saturation region; And the voltage difference of controlling said MM CAP two ends is constant and the voltage of second end of said MM CAP stable, and is so that the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, luminous through said drive thin film transistors driving OLED.
The present invention also provides a kind of pixel cell, comprises OLED and above-mentioned pixel cell driving circuit, and said pixel cell driving circuit is connected with the anode of said OLED, and the negative electrode of said OLED is connected with the low level output terminal of driving power.
The present invention also provides a kind of display device, comprises a plurality of above-mentioned pixel cells.
Compared with prior art; Pixel cell driving circuit of the present invention and method pixel cell and display device; Compensate the threshold voltage of the drive thin film transistors of driving OLED through the gate source voltage of driving control unit controlling and driving thin film transistor (TFT), thereby solve the problem of the even brightness decay of oled panel brightness disproportionation.
Description of drawings
Fig. 1 is the circuit diagram of existing 2T1C pixel cell driving circuit;
Fig. 2 is the circuit diagram of the described pixel cell driving circuit of first embodiment of the invention;
Fig. 3 is the circuit diagram of the described pixel cell driving circuit of second embodiment of the invention;
Fig. 4 is the circuit diagram of the described pixel cell driving circuit of third embodiment of the invention;
Fig. 4 A is the circuit diagram that the described pixel cell driving circuit of third embodiment of the invention is in the equivalent electrical circuit of very first time during section;
Fig. 4 B is the circuit diagram of the equivalent electrical circuit of the described pixel cell driving circuit of third embodiment of the invention when being in for second time period;
Fig. 4 C is the circuit diagram of the equivalent electrical circuit of the described pixel cell driving circuit of third embodiment of the invention when being in for the 3rd time period;
Fig. 5 is the sequential chart of each signal in the described pixel cell driving circuit of third embodiment of the invention.
Embodiment
The invention provides a kind of pixel cell driving circuit and method, pixel cell and display device; Utilize diode (Diode Connection) and through the control store capacitor discharge so that the threshold voltage of the drive thin film transistors of the gate source voltage of drive thin film transistors compensation driving OLED, thereby the problem of the even brightness decay of solution oled panel brightness disproportionation.
As shown in Figure 2, the described pixel cell driving circuit of first embodiment of the invention is used for driving OLED, comprises drive thin film transistors DTFT, first on-off element 21, MM CAP Cs and driving control unit 22;
Said drive thin film transistors DTFT, source electrode and the output voltage of driving power are that the high level output terminal of VDD is connected, and grid is connected with first end of said MM CAP Cs, and drain electrode is connected with the anode of said OLED through said first on-off element 21;
Second end of said MM CAP Cs is connected with data line Data with the source electrode of said drive thin film transistors DTFT respectively through said driving control unit 22;
The grid of said drive thin film transistors DTFT is that the low level output terminal of VSS and the drain electrode of said drive thin film transistors DTFT are connected with the output voltage of said driving power respectively through said driving control unit 22;
Said driving control unit 22; Be used for discharging and recharging through controlling said MM CAP Cs; The gate source voltage of the said drive thin film transistors DTFT compensation Vth to control that said drive thin film transistors DTFT works in the saturation region, wherein, Vth is the threshold voltage of said drive thin film transistors DTFT;
In the specific implementation, said driving control unit 22 also is connected with the sweep trace SCAN that is used for transmission of control signals with control line CR respectively.
According to a kind of embodiment, in this embodiment, said drive thin film transistors DTFT is a p type thin film transistor (TFT).
The described pixel cell driving circuit of this first embodiment is when work; Said first on-off element 21 breaks off the drain electrode of said drive thin film transistors DTFT and being connected of said OLED in the very first time section and second time period, in the drain electrode of the said drive thin film transistors DTFT of the 3rd time period conducting and being connected of said OLED;
Said driving control unit 22 is controlled said MM CAP Cs in said very first time section and is recharged;
Said driving control unit 22 is controlled said MM CAP Cs in said second time period and is discharged through said drive thin film transistors DTFT, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors DTFT;
Said driving control unit 22 is controlled said drive thin film transistors DTFT in the 3rd time period and is worked in the saturation region; And the voltage difference of controlling said MM CAP Cs two ends is constant and the voltage of second end of said MM CAP Cs stable, so that the gate source voltage of said drive thin film transistors DTFT compensates the threshold voltage vt h of said drive thin film transistors DTFT.
Further, the described pixel cell driving circuit of this first embodiment is in when work,
In very first time section, first on-off element 21 breaks off the drain electrode of said drive thin film transistors DTFT and being connected of said OLED; Being connected of second end of said driving control unit 22 conducting data line Data and said MM CAP Cs; The grid of the said drive thin film transistors DTFT of conducting is connected with the drain electrode of said drive thin film transistors DTFT; Being connected of the low level output terminal of the drain electrode of the said drive thin film transistors DTFT of conducting and said driving power; Break off being connected of second end of source electrode and the said MM CAP Cs of said drive thin film transistors DTFT, control said MM CAP Cs and be recharged;
In second time period; The drain electrode of the said drive thin film transistors DTFT of said driving control unit 22 disconnections is connected with the low level output terminal of said driving power; Controlling said MM CAP Cs and discharge through said drive thin film transistors DTFT, is the threshold voltage vt h of said drive thin film transistors DTFT until the gate source voltage of said drive thin film transistors TFT;
In the 3rd time period, the drain electrode of the said drive thin film transistors DTFT of said first on-off element, 21 conductings is connected with said OLED's; Being connected of second end of the said MM CAP Cs of said driving control unit 22 conductings and the source electrode of said drive thin film transistors DTFT; Break off being connected of second end of said data line Data and said MM CAP Cs; Break off being connected of drain electrode of grid and the said drive thin film transistors DTFT of said drive thin film transistors DTFT; Control said drive thin film transistors DTFT and work in the saturation region; And the voltage difference of controlling said MM CAP Cs two ends is constant and the voltage of second end of said MM CAP Cs stable; So that it is the gate source voltage of said drive thin film transistors DTFT compensates the threshold voltage vt h of said drive thin film transistors DTFT, luminous through said drive thin film transistors DTFT driving OLED.
During enforcement, in the described pixel cell driving circuit of this embodiment, said driving control unit comprises second switch element, the 3rd on-off element, the 4th on-off element and the 5th on-off element, wherein,
Be connected with the second switch element between the drain electrode of said driven effect transistor DTFT and the low level output terminal of said driving power;
Be connected with the 3rd on-off element between second end of the source electrode of said drive thin film transistors DTFT and said MM CAP Cs;
Be connected with the 4th on-off element between the grid of said drive thin film transistors DTFT and the drain electrode of said drive thin film transistors DTFT;
Be connected with the 5th on-off element between second end of said MM CAP Cs and the data line Data;
In very first time section; Being connected of second end of said data line Data of said the 5th on-off element conducting and said MM CAP Cs; Being connected of the grid of the said drive thin film transistors DTFT of said the 4th on-off element conducting and the drain electrode of said drive thin film transistors DTFT; Being connected of the drain electrode of the said drive thin film transistors DTFT of said second switch element conductive and the low level output terminal of said driving power, said the 3rd on-off element breaks off being connected of second end of source electrode and the said MM CAP Cs of said drive thin film transistors DTFT;
In second time period, the drain electrode that said second switch element breaks off said drive thin film transistors DTFT is connected with the low level output terminal of said driving power;
In the 3rd time period; Being connected of second end of the said MM CAP Cs of said the 3rd on-off element conducting and the source electrode of said drive thin film transistors DTFT; Said the 5th on-off element breaks off being connected of second end of said data line Data and said MM CAP Cs, and said the 4th on-off element breaks off being connected of drain electrode of grid and the said drive thin film transistors DTFT of said drive thin film transistors DTFT.
As shown in Figure 3, the circuit diagram of the described pixel cell driving circuit of second embodiment of the invention.The described pixel cell driving circuit of second embodiment of the invention is based on the described pixel cell driving circuit of first embodiment of the invention.
In the described pixel cell driving circuit of second embodiment of the invention, said first on-off element 21 is that label is first switching TFT of T1, and T1 is a p type thin film transistor (TFT);
The grid of T1 is connected with the first control line CR1, and the source electrode of T1 is connected with the drain electrode of said drive thin film transistors DTFT, and the drain electrode of T1 is connected with the anode of said OLED.
As shown in Figure 4; The circuit diagram of the described pixel cell driving circuit of third embodiment of the invention; The described pixel cell driving circuit of the 3rd embodiment adopts the 6T1C circuit, through compensation Vth, so that the threshold voltage vt h of the drive current of drive TFT and said drive TFT is irrelevant; Reach the electric current unanimity, improve homogeneity and reliability.
The described pixel cell driving circuit of the 3rd embodiment is based on the described pixel cell driving circuit of this second embodiment;
In the described pixel cell driving circuit of the 3rd embodiment; Said first on-off element is that label is first switching TFT of T1; Said second switch element is that label is the second switch TFT of T2; Said the 3rd on-off element is that label is the 3rd switching TFT of T3, and said the 4th on-off element is that label is the 4th switching TFT of T4, and said the 5th on-off element is that label is the 5th switching TFT of T5; Said drive thin film transistors is that label is the drive TFT of DTFT, and the low level output terminal of said driving power is an earth terminal, wherein,
T1, T2, T3, T4, T5 and DTFT are p type TFT, threshold voltage vt h＜0 of p type TFT, and the source electrode of DTFT directly connects said power lead, for constant-current type connects method;
The grounded drain of T2, the source electrode of T2 is connected with the drain electrode of said T4;
The drain electrode of T1 is connected with the anode of said OLED, and the source electrode of T1 is connected with the drain electrode of the drain electrode of DTFT and T4;
The source electrode of T3 is connected with second end of MM CAP Cs, and the drain electrode of T3 is connected with the source electrode of DTFT;
The source electrode of T4 is connected with the grid of DTFT, and the drain electrode of T4 is connected with the source electrode of the source electrode of T1 and T2;
The source electrode of T5 is connected with data line Data, and the drain electrode of T5 is connected with second end of said MM CAP Cs;
The grid of DTFT is connected with first end of said MM CAP Cs, and the source electrode of DTFT and the output voltage of driving power are that the high level output terminal of VDD is connected;
The grid of T4 is connected with the sweep trace SCAN that is used for transmission of control signals with the grid of said T5;
The grid of T2 is connected with the second control line CR2, and the grid of T1 is connected with the first control line CR1, and the grid of T3 is connected with the 3rd control line CR3.
The described pixel cell driving circuit of the 3rd embodiment adopts the Vth of 6T1C circuit through compensation DTFT, so that the drive current I=K of DTFT * (Vgs-Vth)
2Irrelevant with Vth, reach the electric current unanimity, improve homogeneity.
Shown in Fig. 4 A, during the described pixel cell drive circuit works of third embodiment of the invention, in very first time section; Be pre-charging stage, said sweep trace SCAN and said second control line CR2 output electronegative potential, said first control line CR1 and said control line CR3 output noble potential; Close with control T1 and T3, and control T2, T4 and T5 conducting are (in Fig. 4 A, because T2, T4 and T5 conducting; So not shown T2, T4 and T5, but substitute with lead; And, because closing drain electrode and the path between the OLED of DTFT then, turn-offs T1, so not shown T1 and OLED among Fig. 4 A; Because T3 closes, so not shown T3 among Fig. 4 A), the voltage Vdata input on the data line Data; Said MM CAP Cs is recharged; The voltage of the grid of DTFT (being the A point) and drain electrode is 0, and the source voltage of DTFT is the voltage VDD on the said power lead, so the gate source voltage Vgs=-VDD of DTFT; It is much smaller than the threshold voltage vt h of DTFT, and this moment, DTFT was that a diode gets into state of saturation in fact.
Shown in Fig. 4 B, during the described pixel cell drive circuit works of third embodiment of the invention, in second time period; Said second control line CR2 output noble potential, T2 closes with control, and A point (being the grid of DTFT) disconnection is connected with ground wire GND's; (difference of Fig. 4 B and Fig. 4 A is; Because T2 closes, so A point breaks off and being connected of ground wire) said MM CAP Cs passes through T4 and DTFT begins to discharge, and is threshold voltage vt h up to the gate-source voltage Vgs of DTFT; Be the grid voltage VA=VDD+Vth of DTFT, this moment, second end and the voltage difference between first end of said MM CAP Cs were Vdata-VDD-Vth.
Shown in Fig. 4 C, during the described pixel cell drive circuit works of third embodiment of the invention, in the 3rd time period; Said sweep trace SCAN output noble potential cuts out with control T4, T5, said the 3rd control line CR3 output electronegative potential; T3 opens with control, and said first control line CR1 output electronegative potential opens with control T1 that (difference of Fig. 4 C and Fig. 4 B is; Because T1 opens, the drain electrode that has therefore increased DTFT is connected with the anode of OLED; And because T4 closes, then the A point has broken off and being connected of the drain electrode of DTFT; Because T5 closes, T3 opens; Therefore second end of Cs breaks off and being connected of data line Data, and being connected of the anode of second end that has increased Cs and OLED), DTFT works in the saturation region and flows through said OLED with drive current; Make it luminous; At this moment, the voltage of second end of said MM CAP Cs becomes VDD, and the voltage of first end of said MM CAP Cs like this will be undergone mutation; So that the voltage difference between second end of said MM CAP Cs and first end is constant; So the voltage of first end of said MM CAP Cs is the grid voltage VA=VDD+Vth-Vdata+VDD of DTFT, at this moment, the computing formula that flows through the electric current I of said OLED is by shown in the formula (1):
I＝K×(Vgs-Vth)
2
＝K×{(VDD+Vth-Vdata+VDD)-Vth}
2
=K * (2VDD-Vdata)
2Formula (1)
Wherein, K is the current coefficient of DTFT;
μ, C
OX, W, L be respectively the field-effect mobility of DTFT, gate insulation layer unit-area capacitance, channel width, length;
The 3rd time period was the OLED glow phase, and said OLED will continue luminously to write to the next frame data.
So just make that the electric current that flows through said OLED does not receive the influence of the threshold voltage vt h of DTFT, flow through the homogeneity of the electric current of said OLED with improvement, reach oled panel brightness evenly.
Fig. 5 is the sweep signal VSCAN of the sweep trace SCAN output in the described pixel cell driving circuit of third embodiment of the invention, the data-signal Vdata of data line Data output, the control signal VCR1 of first control line CR1 output, the control signal VCR2 of second control line CR2 output and the sequential chart of the control signal VCR3 that the 3rd control line is exported; In Fig. 5, what B, C, D indicated respectively is very first time section, second time period, the 3rd time period.
The present invention also provides a kind of pixel cell driving method, and it is applied to above-mentioned pixel cell driving circuit, and said pixel cell driving method may further comprise the steps:
The pixel charge step: driving control unit control store electric capacity is recharged;
The pixel discharge step: said driving control unit is controlled said MM CAP through drive thin film transistors discharge, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of driving OLED: said driving control unit is controlled said drive thin film transistors and is worked in the saturation region; And the voltage difference of controlling said MM CAP two ends is constant; So that it is the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, luminous through said drive thin film transistors driving OLED.
According to a kind of embodiment, said pixel charge step comprises: first on-off element breaks off the drain electrode of said drive thin film transistors and being connected of said OLED; Being connected of second end of said driving control unit conducting data line and said MM CAP; The grid of the said drive thin film transistors of conducting is connected with the drain electrode of said drive thin film transistors; Being connected of the low level output terminal of the drain electrode of the said drive thin film transistors of conducting and said driving power; Break off being connected of second end of source electrode and the said MM CAP of said drive thin film transistors, control said MM CAP and be recharged;
Said pixel discharge step comprises: the drain electrode that said driving control unit is broken off said drive thin film transistors is connected with the low level output terminal of said driving power; Controlling said MM CAP and discharge through said drive thin film transistors, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of said driving OLED comprises: the drain electrode of the said drive thin film transistors of the said first on-off element conducting is connected with said OLED's; Being connected of second end of the said MM CAP of said driving control unit conducting and the source electrode of said drive thin film transistors; Break off being connected of second end of said data line and said MM CAP; Break off being connected of drain electrode of grid and the said drive thin film transistors of said drive thin film transistors; Control said drive thin film transistors and work in the saturation region; And the voltage difference of controlling said MM CAP two ends is constant and the voltage of second end of said MM CAP stable, and is so that the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, luminous through said drive thin film transistors driving OLED.
The invention also discloses a kind of pixel cell, it comprises OLED and above-mentioned pixel cell driving circuit, and this pixel cell driving circuit is connected with the anode of OLED, the plus earth of said OLED.
The invention also discloses a kind of display device, comprise a plurality of above-mentioned pixel cells.
More than explanation is just illustrative for the purpose of the present invention; And nonrestrictive, those of ordinary skills understand, under the situation of spirit that does not break away from accompanying claims and limited and scope; Can make many modifications, variation or equivalence, but all will fall in protection scope of the present invention.
Claims (9)
1. a pixel cell driving circuit is used for driving OLED, it is characterized in that, said pixel cell driving circuit comprises drive thin film transistors, first on-off element, MM CAP and driving control unit;
Said drive thin film transistors, source electrode is connected with the high level output terminal of driving power, and grid is connected with first end of said MM CAP, and drain electrode is connected with the anode of said OLED through said first on-off element;
Second end of said MM CAP is connected with data line with the source electrode of said drive thin film transistors respectively through said driving control unit;
The grid of said drive thin film transistors is connected with the low level output terminal of said driving power and the drain electrode of said drive thin film transistors respectively through said driving control unit;
Said driving control unit; Be used for discharging and recharging through controlling said MM CAP; The gate source voltage of the said drive thin film transistors compensation Vth to control that said drive thin film transistors works in the saturation region, wherein, Vth is the threshold voltage of said drive thin film transistors.
2. pixel cell driving circuit as claimed in claim 1 is characterized in that, said drive thin film transistors is a p type thin film transistor (TFT).
3. pixel cell driving circuit as claimed in claim 2 is characterized in that,
Said first on-off element is a p type thin film transistor (TFT);
Said first on-off element, grid is connected with first control line, and source electrode is connected with the drain electrode of said drive thin film transistors, and drain electrode is connected with the anode of said OLED.
4. pixel cell driving circuit as claimed in claim 3 is characterized in that, said driving control unit comprises second switch element, the 3rd on-off element, the 4th on-off element and the 5th on-off element, wherein,
Be connected with the second switch element between the low level output terminal of said driven effect transistor drain and said driving power;
Be connected with the 3rd on-off element between second end of the source electrode of said drive thin film transistors and said MM CAP;
Be connected with the 4th on-off element between the grid of said drive thin film transistors and the drain electrode of said drive thin film transistors;
Be connected with the 5th on-off element between second end of said MM CAP and the data line.
5. pixel cell driving circuit as claimed in claim 4 is characterized in that, said second switch element, said the 3rd on-off element, said the 4th on-off element and said the 5th on-off element are p type thin film transistor (TFT);
Said second switch element, grid is connected with second control line, and source electrode is connected with the drain electrode of said drive thin film transistors, and drain electrode is connected with the low level output terminal of said driving power;
Said the 3rd on-off element, grid is connected with the 3rd control line, and source electrode is connected with second end of said MM CAP, and drain electrode is connected with the source electrode of said drive thin film transistors;
Said the 4th on-off element, grid is connected with the sweep trace that is used for transmission of control signals, and source electrode is connected with the grid of said drive thin film transistors, and drain electrode is connected with the drain electrode of said drive thin film transistors;
Said the 5th on-off element, grid is connected with said sweep trace, and source electrode is connected with said data line, and drain electrode is connected with second end of said MM CAP.
6. pixel cell driving method, it is applied to pixel cell driving circuit as claimed in claim 1, it is characterized in that, and said pixel cell driving method may further comprise the steps:
The pixel charge step: driving control unit control store electric capacity is recharged;
The pixel discharge step: said driving control unit is controlled said MM CAP through drive thin film transistors discharge, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of driving OLED: said driving control unit is controlled said drive thin film transistors and is worked in the saturation region; And the voltage difference of controlling said MM CAP two ends is constant; So that it is the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, luminous through said drive thin film transistors driving OLED.
7. pixel cell driving method as claimed in claim 6 is characterized in that,
Said pixel charge step comprises: first on-off element breaks off the drain electrode of said drive thin film transistors and being connected of said OLED; Being connected of second end of said driving control unit conducting data line and said MM CAP; The grid of the said drive thin film transistors of conducting is connected with the drain electrode of said drive thin film transistors; Being connected of the low level output terminal of the drain electrode of the said drive thin film transistors of conducting and said driving power; Break off being connected of second end of source electrode and the said MM CAP of said drive thin film transistors, control said MM CAP and be recharged;
Said pixel discharge step comprises: the drain electrode that said driving control unit is broken off said drive thin film transistors is connected with the low level output terminal of said driving power; Controlling said MM CAP and discharge through said drive thin film transistors, is the threshold voltage vt h of said drive thin film transistors until the gate source voltage of said drive thin film transistors;
The luminous step display of said driving OLED comprises: the drain electrode of the said drive thin film transistors of the said first on-off element conducting is connected with said OLED's; Being connected of second end of the said MM CAP of said driving control unit conducting and the source electrode of said drive thin film transistors; Break off being connected of second end of said data line and said MM CAP; Break off being connected of drain electrode of grid and the said drive thin film transistors of said drive thin film transistors; Control said drive thin film transistors and work in the saturation region; And the gate source voltage of said drive thin film transistors compensates the threshold voltage vt h of said drive thin film transistors, and is luminous through said drive thin film transistors driving OLED.
8. pixel cell; It is characterized in that; Comprise OLED and like the described pixel cell driving circuit of arbitrary claim in the claim 1 to 5, said pixel cell driving circuit is connected with the anode of said OLED, the negative electrode of said OLED is connected with the low level output terminal of driving power.
9. a display device is characterized in that, comprises a plurality of pixel cells as claimed in claim 8.
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