CN102708789A - Pixel unit driving circuit and method, pixel unit and display device - Google Patents

Abstract

The present invention provides a pixel unit driving circuit and method, a pixel unit and a display device. The pixel unit driving circuit includes a driving thin film transistor, a first switching element, a storage capacitor and a driving control unit; a driving thin film transistor, a source and a driving power supply The high-level output end of the storage capacitor is connected, the gate is connected to the first end of the storage capacitor, and the drain is connected to the anode of the OLED through the first switching element; the second end of the storage capacitor is respectively connected to the source of the driving thin film transistor through the driving control unit connected to the data line; the gate of the driving thin film transistor is respectively connected to the low level output end of the driving power supply and the drain of the driving thin film transistor through the driving control unit; the present invention controls the charging and discharging of the storage capacitor to control the driving thin film transistor to work in In the saturation region, the gate-source voltage of the driving thin film transistor compensates the threshold voltage of the driving thin film transistor, so as to solve the problems of uneven brightness and brightness attenuation of the OLED panel.

Description

Pixel unit driving circuit and method, pixel unit and display device

technical field

The invention relates to the field of organic light-emitting display, in particular to an AMOLED (active matrix organic light-emitting diode) pixel unit drive circuit and method, a pixel unit and a display device.

Background technique

The existing pixel unit drive circuit is shown in Figure 1. The drive circuit includes two transistors and a capacitor. One of the transistors is a switch tube T1, which is controlled by the scan signal Vscan output by the scan line. The purpose is to control the data line Data The other transistor is the drive tube T2, which controls the OLED to emit light; Cs is the storage capacitor, which is used to maintain the voltage applied to the drive tube T2 during the non-scanning period. The above circuit is called 2T1C pixel unit drive circuit.

AMOLED (Active Matrix Organic Light Emitting Diode, Active Matrix Organic Light Emitting Diode) can emit light is driven by the current generated by the driving transistor in the saturated state, because when the same gray scale voltage is input, the different threshold voltages of the driving transistor It will lead to different driving currents, resulting in inconsistency of the current. However, the uniformity of the threshold voltage Vth on the LTPS (low temperature polysilicon technology) process is very poor, and Vth also drifts, so the brightness uniformity of the traditional 2T1C pixel unit driving circuit has always been poor.

Contents of the invention

The main object of the present invention is to provide a pixel unit driving circuit and method, a pixel unit and a display device, so as to improve the brightness uniformity of an OLED panel.

In order to achieve the above object, the present invention provides a pixel unit driving circuit for driving an OLED, the pixel unit driving circuit includes a driving thin film transistor, a first switching element, a storage capacitor and a driving control unit;

The source of the driving thin film transistor is connected to the high-level output terminal of the driving power supply, the gate is connected to the first end of the storage capacitor, and the drain is connected to the anode of the OLED through the first switching element;

The second end of the storage capacitor is respectively connected to the source of the driving thin film transistor and the data line through the driving control unit;

The gate of the driving thin film transistor is respectively connected to the low level output terminal of the driving power supply and the drain of the driving thin film transistor through the driving control unit;

The driving control unit is configured to control the charging and discharging of the storage capacitor to control the driving thin film transistor to work in a saturation region and the gate-source voltage of the driving thin film transistor to compensate Vth, wherein Vth is the driving thin film transistor threshold voltage.

In practice, the driving thin film transistor is a p-type thin film transistor.

During implementation, the first switching element is a p-type thin film transistor;

For the first switching element, the gate is connected to the first control line, the source is connected to the drain of the driving thin film transistor, and the drain is connected to the anode of the OLED.

During implementation, the drive control unit includes a second switch element, a third switch element, a fourth switch element and a fifth switch element, wherein,

A second switching element is connected between the drain of the driving effect transistor and the low-level output terminal of the driving power supply;

A third switching element is connected between the source of the driving thin film transistor and the second end of the storage capacitor;

A fourth switching element is connected between the gate of the driving thin film transistor and the drain of the driving thin film transistor;

A fifth switch element is connected between the second end of the storage capacitor and the data line.

During implementation, the second switch element, the third switch element, the fourth switch element and the fifth switch element are p-type thin film transistors;

The gate of the first switching element is connected to the first control line, the source is connected to the drain of the driving thin film transistor, and the drain is connected to the anode of the OLED;

The gate of the second switching element is connected to the second control line, the source is connected to the drain of the driving thin film transistor, and the drain is connected to the low-level output terminal of the driving power supply;

The gate of the third switching element is connected to the third control line, the source is connected to the second end of the storage capacitor, and the drain is connected to the source of the driving thin film transistor;

For the fourth switching element, the gate is connected to the scanning line for transmitting the control signal, the source is connected to the gate of the driving thin film transistor, and the drain is connected to the drain of the driving thin film transistor;

For the fifth switching element, the gate is connected to the scanning line, the source is connected to the data line, and the drain is connected to the second end of the storage capacitor.

The present invention also provides a pixel unit driving method, which is applied to the above-mentioned pixel unit driving circuit, and the pixel unit driving method includes the following steps:

Pixel charging step: the drive control unit controls the storage capacitor to be charged;

Pixel discharging step: the driving control unit controls the storage capacitor to discharge through the driving thin film transistor until the gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor;

The step of driving the OLED to emit light and display: the driving control unit controls the driving thin film transistor to work in the saturation region, and controls the voltage difference between the two ends of the storage capacitor to be constant, so that the gate-source voltage of the driving thin film transistor compensates the The threshold voltage Vth of the driving thin film transistor is used to drive the OLED to emit light.

During implementation, the pixel charging step includes: the first switching element disconnects the drain of the driving thin film transistor from the OLED; the driving control unit connects the data line to the second end of the storage capacitor , turning on the connection between the gate of the driving thin film transistor and the drain of the driving thin film transistor, turning on the connection between the drain of the driving thin film transistor and the low level output terminal of the driving power supply, and disconnecting the driving the connection between the source of the thin film transistor and the second terminal of the storage capacitor, and controlling the storage capacitor to be charged;

The pixel discharging step includes: the driving control unit disconnects the drain of the driving thin film transistor from the low level output terminal of the driving power supply, and controls the storage capacitor to discharge through the driving thin film transistor until the The gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor;

The step of driving the OLED to emit light and display includes: the first switching element turns on the connection between the drain of the driving thin film transistor and the OLED; the driving control unit turns on the second end of the storage capacitor and the connecting the source of the driving thin film transistor, disconnecting the data line from the second end of the storage capacitor, disconnecting the gate of the driving thin film transistor from the drain of the driving thin film transistor, and controlling the The driving thin film transistor works in a saturation region, and the voltage difference between the two ends of the storage capacitor is controlled to be constant and the voltage at the second end of the storage capacitor is stable, so that the gate-source voltage of the driving thin film transistor compensates for the driving thin film The threshold voltage Vth of the transistor drives the OLED to emit light through the driving thin film transistor.

The present invention also provides a pixel unit, including an OLED and the above-mentioned pixel unit driving circuit, the pixel unit driving circuit is connected to the anode of the OLED, and the cathode of the OLED is connected to the low-level output terminal of the driving power supply.

The present invention also provides a display device, comprising a plurality of the above-mentioned pixel units.

Compared with the prior art, the pixel unit driving circuit and method pixel unit and the display device of the present invention control the gate-source voltage of the driving thin film transistor through the driving control unit to compensate the threshold voltage of the driving thin film transistor of the OLED, thereby solving the problem of OLED. The problem of uneven brightness and brightness attenuation of the panel.

Description of drawings

FIG. 1 is a circuit diagram of an existing 2T1C pixel unit driving circuit;

2 is a circuit diagram of a pixel unit driving circuit according to the first embodiment of the present invention;

3 is a circuit diagram of a pixel unit driving circuit according to a second embodiment of the present invention;

4 is a circuit diagram of a pixel unit driving circuit according to a third embodiment of the present invention;

4A is a circuit diagram of an equivalent circuit of the pixel unit driving circuit in the first time period according to the third embodiment of the present invention;

4B is a circuit diagram of an equivalent circuit of the pixel unit driving circuit in the second time period according to the third embodiment of the present invention;

4C is a circuit diagram of an equivalent circuit of the pixel unit driving circuit in the third time period according to the third embodiment of the present invention;

FIG. 5 is a timing diagram of signals in the pixel unit driving circuit according to the third embodiment of the present invention.

Detailed ways

The present invention provides a pixel unit driving circuit and method, a pixel unit and a display device, using a diode connection (Diode Connection) and controlling the discharge of a storage capacitor so that the gate-source voltage of the driving thin film transistor is compensated for driving the thin film transistor of the OLED. Threshold voltage, so as to solve the problem of uneven brightness and brightness attenuation of OLED panels.

As shown in FIG. 2 , the pixel unit driving circuit according to the first embodiment of the present invention is used to drive OLED, including a driving thin film transistor DTFT, a first switching element 21, a storage capacitor Cs and a driving control unit 22;

The source of the driving thin film transistor DTFT is connected to the high-level output end of the driving power supply whose output voltage is VDD, the gate is connected to the first end of the storage capacitor Cs, and the drain is connected to the first end of the storage capacitor Cs through the first switching element 21. the anode connection of the OLED;

The second end of the storage capacitor Cs is respectively connected to the source of the driving thin film transistor DTFT and the data line Data through the driving control unit 22;

The gate of the driving thin film transistor DTFT is respectively connected to the low level output end of the driving power supply whose output voltage is VSS and the drain of the driving thin film transistor DTFT through the driving control unit 22;

The driving control unit 22 is configured to control the charging and discharging of the storage capacitor Cs to control the driving thin film transistor DTFT to work in a saturation region and the gate-source voltage compensation Vth of the driving thin film transistor DTFT, wherein Vth is the The threshold voltage of the driving thin film transistor DTFT;

In a specific implementation, the drive control unit 22 is also respectively connected to the control line CR and the scan line SCAN for transmitting control signals.

According to a specific implementation manner, in this embodiment, the driving thin film transistor DTFT is a p-type thin film transistor.

When the pixel unit driving circuit described in the first embodiment is in operation, the first switching element 21 disconnects the drain of the driving thin film transistor DTFT from the OLED during the first time period and the second time period. , turning on the connection between the drain of the driving thin film transistor DTFT and the OLED in a third time period;

The drive control unit 22 controls the storage capacitor Cs to be charged during the first time period;

The driving control unit 22 controls the storage capacitor Cs to discharge through the driving thin film transistor DTFT in the second time period until the gate-source voltage of the driving thin film transistor DTFT is the threshold voltage Vth of the driving thin film transistor;

The driving control unit 22 controls the driving thin film transistor DTFT to work in a saturation region in the third time period, and controls the voltage difference between the two ends of the storage capacitor Cs to be constant and the voltage at the second end of the storage capacitor Cs to be stable, so that the gate-source voltage of the driving thin film transistor DTFT compensates the threshold voltage Vth of the driving thin film transistor DTFT.

Further, when the pixel unit driving circuit described in the first embodiment is working,

In the first period of time, the first switching element 21 disconnects the connection between the drain of the driving thin film transistor DTFT and the OLED; the driving control unit 22 turns on the connection between the data line Data and the second end of the storage capacitor Cs Connecting, turning on the connection between the gate of the driving thin film transistor DTFT and the drain of the driving thin film transistor DTFT, turning on the connection between the drain of the driving thin film transistor DTFT and the low level output terminal of the driving power supply, disconnecting the source of the driving thin film transistor DTFT from the second terminal of the storage capacitor Cs, and controlling the storage capacitor Cs to be charged;

In the second time period, the driving control unit 22 disconnects the drain of the driving thin film transistor DTFT from the low level output terminal of the driving power supply, and controls the storage capacitor Cs to discharge through the driving thin film transistor DTFT , until the gate-source voltage of the driving thin film transistor TFT is the threshold voltage Vth of the driving thin film transistor DTFT;

In the third time period, the first switching element 21 turns on the connection between the drain of the driving thin film transistor DTFT and the OLED; the driving control unit 22 turns on the second end of the storage capacitor Cs and the Connect the source of the driving thin film transistor DTFT, disconnect the data line Data and the second end of the storage capacitor Cs, disconnect the gate of the driving thin film transistor DTFT and the drain of the driving thin film transistor DTFT pole connection, control the driving thin film transistor DTFT to work in the saturation region, and control the voltage difference between the two ends of the storage capacitor Cs to be constant and the voltage at the second end of the storage capacitor Cs to be stable, so that the driving thin film transistor The gate-source voltage of the DTFT compensates the threshold voltage Vth of the driving thin film transistor DTFT, and the OLED is driven to emit light through the driving thin film transistor DTFT.

During implementation, in the pixel unit driving circuit described in this embodiment, the driving control unit includes a second switching element, a third switching element, a fourth switching element, and a fifth switching element, wherein,

A second switching element is connected between the drain of the driving effect transistor DTFT and the low-level output terminal of the driving power supply;

A third switching element is connected between the source of the driving thin film transistor DTFT and the second end of the storage capacitor Cs;

A fourth switching element is connected between the gate of the driving thin film transistor DTFT and the drain of the driving thin film transistor DTFT;

A fifth switch element is connected between the second end of the storage capacitor Cs and the data line Data;

In the first time period, the fifth switching element turns on the connection between the data line Data and the second end of the storage capacitor Cs, and the fourth switching element turns on the gate of the driving thin film transistor DTFT and the The drain of the driving thin film transistor DTFT is connected, the second switching element conducts the connection between the drain of the driving thin film transistor DTFT and the low level output terminal of the driving power supply, and the third switching element disconnects the The connection between the source of the driving thin film transistor DTFT and the second end of the storage capacitor Cs;

During the second time period, the second switching element disconnects the drain of the driving thin film transistor DTFT from the low level output terminal of the driving power supply;

In the third time period, the third switching element turns on the connection between the second end of the storage capacitor Cs and the source of the driving thin film transistor DTFT, and the fifth switching element disconnects the data lines Data and The second end of the storage capacitor Cs is connected, and the fourth switching element disconnects the gate of the driving thin film transistor DTFT from the drain of the driving thin film transistor DTFT.

As shown in FIG. 3 , the circuit diagram of the pixel unit driving circuit described in the second embodiment of the present invention. The pixel unit driving circuit described in the second embodiment of the present invention is based on the pixel unit driving circuit described in the first embodiment of the present invention.

In the pixel unit driving circuit according to the second embodiment of the present invention, the first switch element 21 is a first switch TFT labeled T1, and T1 is a p-type thin film transistor;

The gate of T1 is connected to the first control line CR1, the source of T1 is connected to the drain of the driving thin film transistor DTFT, and the drain of T1 is connected to the anode of the OLED.

As shown in FIG. 4 , the circuit diagram of the pixel unit driving circuit described in the third embodiment of the present invention, the pixel unit driving circuit described in the third embodiment adopts a 6T1C circuit, and by compensating Vth, the driving current of the driving TFT is equal to The threshold voltage Vth of the driving TFT is irrelevant, achieving consistent current and improving uniformity and reliability.

The pixel unit driving circuit described in the third embodiment is based on the pixel unit driving circuit described in the second embodiment;

In the pixel unit driving circuit described in the third embodiment, the first switching element is a first switching TFT labeled T1, the second switching element is a second switching TFT labeled T2, and the first switching element is a TFT labeled T2. The three switching elements are the third switching TFT labeled T3, the fourth switching element is the fourth switching TFT labeled T4, and the fifth switching element is the fifth switching TFT labeled T5; the driving thin film transistor is a driving TFT marked as DTFT, and the low-level output terminal of the driving power supply is a ground terminal, wherein,

T1, T2, T3, T4, T5 and DTFT are p-type TFTs, the threshold voltage Vth of the p-type TFTs is less than 0, and the source of the DTFTs is directly connected to the power line, which is a constant current connection method;

The drain of T2 is grounded, and the source of T2 is connected to the drain of T4;

The drain of T1 is connected to the anode of the OLED, the source of T1 is connected to the drain of DTFT and the drain of T4;

The source of T3 is connected to the second end of the storage capacitor Cs, and the drain of T3 is connected to the source of the DTFT;

The source of T4 is connected to the gate of DTFT, the drain of T4 is connected to the source of T1 and the source of T2;

The source of T5 is connected to the data line Data, and the drain of T5 is connected to the second end of the storage capacitor Cs;

The gate of the DTFT is connected to the first end of the storage capacitor Cs, and the source of the DTFT is connected to the high-level output terminal whose output voltage of the driving power is VDD;

The gate of T4 and the gate of T5 are connected to the scan line SCAN for transmitting control signals;

The gate of T2 is connected to the second control line CR2, the gate of T1 is connected to the first control line CR1, and the gate of T3 is connected to the third control line CR3.

The pixel unit driving circuit described in the third embodiment uses a 6T1C circuit to compensate the Vth of the DTFT so that the driving current I=K*(Vgs-Vth) ² of the DTFT is independent of Vth to achieve consistent current and improve uniformity.

As shown in FIG. 4A, when the pixel unit driving circuit according to the third embodiment of the present invention is working, in the first time period, that is, the pre-charging phase, the scan line SCAN and the second control line CR2 output a low potential, The first control line CR1 and the control line CR3 output a high potential to control T1 and T3 to be turned off, and to control T2, T4, and T5 to be turned on (in FIG. 4A, since T2, T4, and T5 are turned on, there is no T2, T4, and T5 are shown, but are replaced by wires; and, since T1 is closed, the path between the drain of the DTFT and the OLED is closed, so T1 and OLED are not shown in Figure 4A; since T3 is closed, the figure T3 is not shown in 4A), the voltage Vdata on the data line Data is input, the storage capacitor Cs is charged, the voltage of the gate (namely point A) and the drain of the DTFT are both 0, and the source voltage of the DTFT is The voltage VDD on the above-mentioned power line, so the gate-source voltage Vgs=-VDD of the DTFT, which is much smaller than the threshold voltage Vth of the DTFT, at this time the DTFT is actually a diode and enters a saturated state.

As shown in FIG. 4B, when the pixel unit driving circuit described in the third embodiment of the present invention is working, in the second time period, the second control line CR2 outputs a high potential to control T2 to be turned off, and point A (that is, the DTFT Gate) is disconnected from the ground wire GND, (the difference between Figure 4B and Figure 4A is that because T2 is closed, point A is disconnected from the ground wire) the storage capacitor Cs starts to discharge through T4 and DTFT until The gate-source voltage Vgs of the DTFT is the threshold voltage Vth, that is, the gate voltage of the DTFT VA=VDD+Vth, at this time, the voltage difference between the second terminal and the first terminal of the storage capacitor Cs is Vdata-VDD- Vth.

As shown in FIG. 4C, when the pixel unit driving circuit described in the third embodiment of the present invention is working, in the third time period, the scanning line SCAN outputs a high potential to control T4 and T5 to be turned off, and the third control line CR3 outputs a low potential to control the opening of T3, and the first control line CR1 outputs a low potential to control the opening of T1 (the difference between Figure 4C and Figure 4B is that since T1 is turned on, the drain of the DTFT and the anode of the OLED are added and because T4 is closed, point A is disconnected from the drain of DTFT; because T5 is closed and T3 is open, the second end of Cs is disconnected from the data line Data, and the second end of Cs is increased The two terminals are connected to the anode of the OLED), and the DTFT works in the saturation region to drive current to flow through the OLED to make it emit light. At this time, the voltage of the second terminal of the storage capacitor Cs becomes VDD, so that the storage capacitor The voltage at the first end of Cs will change abruptly, so that the voltage difference between the second end and the first end of the storage capacitor Cs is constant, so the voltage at the first end of the storage capacitor Cs is the gate voltage of the DTFT Pole voltage VA=VDD+Vth-Vdata+VDD, at this time, the calculation formula of the current I flowing through the OLED is shown in formula (1):

I=K×(Vgs-Vth) ²

=K×{(VDD+Vth-Vdata+VDD)-Vth} ²

＝K×(2VDD-Vdata) ² ; formula (1)

Among them, K is the current coefficient of DTFT;

$\mathrm{<span\; class="notranslate">\; K</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; ox</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&mu;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; W</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; ;</span>$

μ, C _OX , W, L are the field-effect mobility of DTFT, the capacitance per unit area of the gate insulating layer, the channel width, and the length;

The third time period is the OLED light-emitting stage, and the OLED will continue to emit light until the next frame of data is written.

In this way, the current flowing through the OLED is not affected by the threshold voltage Vth of the DTFT, so as to improve the uniformity of the current flowing through the OLED and achieve uniform brightness of the OLED panel.

5 is the scan signal VSCAN output by the scan line SCAN, the data signal Vdata output by the data line Data, the control signal VCR1 output by the first control line CR1, and the second control line in the pixel unit drive circuit according to the third embodiment of the present invention. The timing diagram of the control signal VCR2 output by the line CR2 and the control signal VCR3 output by the third control line. In FIG. 5 , B, C, and D indicate the first time period, the second time period, and the third time period, respectively.

The present invention also provides a pixel unit driving method, which is applied to the above-mentioned pixel unit driving circuit, and the pixel unit driving method includes the following steps:

Pixel charging step: the drive control unit controls the storage capacitor to be charged;

Pixel discharging step: the driving control unit controls the storage capacitor to discharge through the driving thin film transistor until the gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor;

The step of driving the OLED to emit light and display: the driving control unit controls the driving thin film transistor to work in the saturation region, and controls the voltage difference between the two ends of the storage capacitor to be constant, so that the gate-source voltage of the driving thin film transistor compensates the The threshold voltage Vth of the driving thin film transistor is used to drive the OLED to emit light.

According to a specific implementation manner, the pixel charging step includes: a first switching element disconnects the drain of the driving thin film transistor from the OLED; the driving control unit turns on the data line and the storage capacitor The connection of the second terminal is to conduct the connection between the gate of the driving thin film transistor and the drain of the driving thin film transistor, and to connect the drain of the driving thin film transistor to the low level output terminal of the driving power supply, disconnecting the source of the driving thin film transistor from the second terminal of the storage capacitor, and controlling the storage capacitor to be charged;

The pixel discharging step includes: the driving control unit disconnects the drain of the driving thin film transistor from the low level output terminal of the driving power supply, and controls the storage capacitor to discharge through the driving thin film transistor until the The gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor;

The step of driving the OLED to emit light and display includes: the first switching element turns on the connection between the drain of the driving thin film transistor and the OLED; the driving control unit turns on the second end of the storage capacitor and the connecting the source of the driving thin film transistor, disconnecting the data line from the second end of the storage capacitor, disconnecting the gate of the driving thin film transistor from the drain of the driving thin film transistor, and controlling the The driving thin film transistor works in a saturation region, and the voltage difference between the two ends of the storage capacitor is controlled to be constant and the voltage at the second end of the storage capacitor is stable, so that the gate-source voltage of the driving thin film transistor compensates for the driving thin film The threshold voltage Vth of the transistor drives the OLED to emit light through the driving thin film transistor.

The present invention also discloses a pixel unit, which includes an OLED and the above-mentioned pixel unit drive circuit, the pixel unit drive circuit is connected to the anode of the OLED, and the cathode of the OLED is grounded.

The present invention also discloses a display device, which comprises a plurality of the above pixel units.

The above description is only illustrative, rather than restrictive, to the present invention. Those skilled in the art understand that many modifications, changes or the like can be made without departing from the spirit and scope defined by the appended claims. effect, but all will fall within the protection scope of the present invention.

Claims (9)

1. A pixel unit driving circuit for driving an OLED, characterized in that the pixel unit driving circuit includes a driving thin film transistor, a first switching element, a storage capacitor and a driving control unit; The source of the driving thin film transistor is connected to the high-level output terminal of the driving power supply, the gate is connected to the first end of the storage capacitor, and the drain is connected to the anode of the OLED through the first switching element; The second end of the storage capacitor is respectively connected to the source of the driving thin film transistor and the data line through the driving control unit; The gate of the driving thin film transistor is respectively connected to the low level output terminal of the driving power supply and the drain of the driving thin film transistor through the driving control unit; The driving control unit is configured to control the charging and discharging of the storage capacitor to control the driving thin film transistor to work in a saturation region and the gate-source voltage of the driving thin film transistor to compensate Vth, wherein Vth is the driving thin film transistor threshold voltage. 2. The pixel unit driving circuit according to claim 1, wherein the driving thin film transistor is a p-type thin film transistor. 3. The pixel unit driving circuit according to claim 2, wherein: The first switching element is a p-type thin film transistor; For the first switching element, the gate is connected to the first control line, the source is connected to the drain of the driving thin film transistor, and the drain is connected to the anode of the OLED. 4. The pixel unit driving circuit according to claim 3, wherein the driving control unit comprises a second switching element, a third switching element, a fourth switching element and a fifth switching element, wherein, A second switching element is connected between the drain of the driving effect transistor and the low-level output terminal of the driving power supply; A third switching element is connected between the source of the driving thin film transistor and the second end of the storage capacitor; A fourth switching element is connected between the gate of the driving thin film transistor and the drain of the driving thin film transistor; A fifth switch element is connected between the second end of the storage capacitor and the data line. 5. The pixel unit driving circuit according to claim 4, wherein the second switching element, the third switching element, the fourth switching element and the fifth switching element are p-type thin film transistors ; The gate of the second switching element is connected to the second control line, the source is connected to the drain of the driving thin film transistor, and the drain is connected to the low-level output terminal of the driving power supply; The gate of the third switching element is connected to the third control line, the source is connected to the second end of the storage capacitor, and the drain is connected to the source of the driving thin film transistor; For the fourth switching element, the gate is connected to the scanning line for transmitting the control signal, the source is connected to the gate of the driving thin film transistor, and the drain is connected to the drain of the driving thin film transistor; For the fifth switching element, the gate is connected to the scanning line, the source is connected to the data line, and the drain is connected to the second end of the storage capacitor. 6. A pixel unit driving method, which is applied to the pixel unit driving circuit as claimed in claim 1, wherein the pixel unit driving method comprises the following steps: Pixel charging step: the drive control unit controls the storage capacitor to be charged; Pixel discharging step: the driving control unit controls the storage capacitor to discharge through the driving thin film transistor until the gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor; The step of driving the OLED to emit light and display: the driving control unit controls the driving thin film transistor to work in the saturation region, and controls the voltage difference between the two ends of the storage capacitor to be constant, so that the gate-source voltage of the driving thin film transistor compensates the The threshold voltage Vth of the driving thin film transistor is used to drive the OLED to emit light. 7. The pixel unit driving method according to claim 6, wherein: The pixel charging step includes: the first switching element disconnects the drain of the driving thin film transistor from the OLED; the driving control unit connects the data line to the second end of the storage capacitor, and turns on The gate of the driving thin film transistor is connected to the drain of the driving thin film transistor, the connection between the drain of the driving thin film transistor and the low level output terminal of the driving power supply is turned on, and the driving thin film transistor is disconnected. the connection between the source of the storage capacitor and the second end of the storage capacitor, and control the storage capacitor to be charged; The pixel discharging step includes: the driving control unit disconnects the drain of the driving thin film transistor from the low level output terminal of the driving power supply, and controls the storage capacitor to discharge through the driving thin film transistor until the The gate-source voltage of the driving thin film transistor is the threshold voltage Vth of the driving thin film transistor; The step of driving the OLED to emit light and display includes: the first switching element turns on the connection between the drain of the driving thin film transistor and the OLED; the driving control unit turns on the second end of the storage capacitor and the connecting the source of the driving thin film transistor, disconnecting the data line from the second end of the storage capacitor, disconnecting the gate of the driving thin film transistor from the drain of the driving thin film transistor, and controlling the The driving thin film transistor works in a saturation region, and the gate-source voltage of the driving thin film transistor compensates the threshold voltage Vth of the driving thin film transistor, and the OLED is driven to emit light through the driving thin film transistor. 8. A pixel unit, characterized in that it comprises an OLED and the pixel unit driving circuit according to any one of claims 1 to 5, the pixel unit driving circuit is connected to the anode of the OLED, and the OLED The cathode of the drive power supply is connected to the low level output terminal. 9. A display device, comprising a plurality of pixel units according to claim 8.

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