BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of display, and in particular to an organic light-emitting diode (OLED) driving circuit and driving method.

2. The Related Arts

The organic light-emitting diode (OLED) display provides many advantages, such as, active illumination, low driving voltage, high luminance efficiency, fast response speed, high clarity and contrast, near 180° viewing angle, wide operation temperature range, ability to realize full-color display, and so on, and has become the most promising display technology.

The OLED displays can be classified into two categories according to the driving method: passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), namely, direct addressing and thin film transistor (TFT) array addressing, wherein the AMOLED has a plurality of pixels arranged in an array, belongs to an active display type, has high luminous efficiency, and is generally used as a high-definition large-sized display device.

The AMOLED is a current-driven device. When a current flows through the organic light-emitting diode, the organic light-emitting diode emits light, and the light-emitting luminance is determined by the current flowing through the organic light-emitting diode. Most known integrated circuits (ICs) only transmit voltage signals, so the pixel driving circuit of the AMOLED needs to convert the voltage signal into a current signal. The conventional AMOLED pixel driving circuit is usually 2T1C-structured, that is, comprising two TFTs plus a capacitor, which converts the voltage into a current.

As shown inFIG. 1, the conventional AMOLED pixel driving circuit of the 2T1C structure using the N-type TFT comprises: a first TFT T10, a second TFT T20, a capacitor C10, and an OLED D10. The first TFT T10has a gate connected to a scan signal Gate, a source connected to a data signal Data, and a drain electrically connected to a gate of the second TFT T20. The second TFT T20has a drain connected to a power supply positive voltage OVDD, and a source electrically connected to an anode of the OLED D10. The OLED D10has a cathode connected to a power supply negative voltage OVSS. Both ends of the capacitor C10are electrically connected to the gate and the source of the second TFT T20, respectively. During display, the scan signal Gate first becomes high voltage to turn on the first TFT T10, and the data signal Data enters the gate of the second TFT T20and the capacitor C10through the first TFT T10, and then the scan signal Gate is low voltage to turn off the first TFT T10. As a result, due to the storage function of the capacitor C10, the gate voltage of the second TFT T20can continue to maintain at the data signal voltage, so that the second TFT T20is in a turned-on state, and the driving current enters the OLED D10through the second TFT T20, and drives the OLED D10to emit light. Actually, however, there is a parasitic capacitance between the gate and the drain of the first TFT T10, and at the instant when the scan signal Gate is changed from a high voltage to a low voltage to turn off the first TFT T10, the drain voltage of the first TFT T10, i.e., the gate voltage of the second TFT T20, will drop due to the existence of parasitic capacitance, resulting in a decrease in the gate-to-source voltage difference of the second TFT T20, which in turn lowers the luminance of the OLED D10and affects the display quality.

As shown inFIG. 2, the conventional AMOLED pixel driving circuit of the 2T1C structure using the P-type TFT comprises: a first TFT T10′, a second TFT T20′, a capacitor C10′, and an OLED D10′. The first TFT T10′ has a gate connected to a scan signal Gate, a source connected to a data signal Data, and a drain electrically connected to a gate of the second TFT T20′. The second TFT T20′ has a source connected to a power supply positive voltage OVDD′, and a drain electrically connected to an anode of the OLED D10′. The OLED D10′ has a cathode connected to a power supply negative voltage OVSS′. Both ends of the capacitor C10′ are electrically connected to the gate and the source of the second TFT T20′, respectively. During display, the scan signal Gate first becomes low voltage to turn on the first TFT T10′, and the data signal Data enters the gate of the second TFT T20′ and the capacitor C10′ through the first TFT T10′, and then the scan signal Gate is high voltage to turn off the first TFT T10′. As a result, due to the storage function of the capacitor C10′, the gate voltage of the second TFT T20′ can continue to maintain at the data signal voltage, so that the second TFT T20′ is in a turned-on state, and the driving current enters the OLED D10′ through the second TFT T20′, and drives the OLED D10′ to emit light. Similar to the AMOLD pixel driving circuit using N-type TFT, due to a parasitic capacitance between the gate and the drain of the first TFT T10′, at the instant when the scan signal Gate is changed from a low voltage to a high voltage to turn off the first TFT T10′, the drain voltage of the first TFT T10′, i.e., the gate voltage of the second TFT T20′, will rise, resulting in an increase in the gate-to-source voltage difference of the second TFT T20′, which in turn lowers the luminance of the OLED D10′ and affects the display quality.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an AMOLED pixel driving circuit, able to improve the problem that the luminance of the OLED changes due to the parasitic capacitance between the gate and the drain of the switching TFT when the scan signal is turned off, and improves the display quality.

Another object of the present invention is to provide an AMOLED pixel driving method, able to improve the problem that the luminance of the OLED changes due to the parasitic capacitance between the gate and the drain of the switching TFT when the scan signal is turned off, and improves the display quality.

To achieve the above object, the present invention provides an AMOLED pixel driving circuit, comprising: a plurality of sub-pixels arranged in an array, a plurality of scan lines, a plurality of data lines, and a plurality of voltage switching modules;

each column of sub-pixels being connected to a data line; each row of sub-pixels being correspondingly connected with a scan line; each voltage switching module being correspondingly connected with a row of sub-pixels and the scan line connected by the row of sub-pixel elements, and connected to a first power source positive voltage and a second power source positive voltage;

each of the sub-pixels comprising a first P-type TFT, a second TFT, a capacitor, and an OLED; the first P-type TFT having a gate electrically connected to the corresponding scan line, a source electrically connected to the corresponding data line, and a drain electrically connected to a gate of the second TFT; the second TFT having a source electrically connected to the corresponding voltage switching module, and a drain electrically connected to an anode of the OLED; the capacitor having two ends electrically connected to the gate and the source of the second TFT respectively; the OLED having a cathode connected to a power source negative voltage;

the voltage switching module being configured to input the first power source positive voltage to the sources of the second TFTs of the corresponding row of sub-pixels when the scan signal on the scan line connected thereto turning on the first P-type TFTs in the corresponding row of sub-pixels, and to input the second power source positive voltage to the sources of the second TFTs of the corresponding row of sub-pixels when the scan signal on the scan line connected thereto turning off the first P-type TFTs in the corresponding row of sub-pixels;

the first power source positive voltage being less than the second power source positive voltage.

Wherein, each voltage switching module comprises a third N-type TFT and a fourth P-type TFT, the third N-type TFT has a gate electrically connected to the corresponding scan line, a source connected to the second power supply positive voltage and a drain electrically connected to a drain of the fourth P-type TFT and electrically connected to the source of the second TFT of the corresponding row of the sub-pixels; the fourth P-type TFT has a gate electrically connected to the corresponding scan line, and a source connected to the first power supply positive voltage.

Wherein, the second TFT is a P-type TFT.

The present invention also provides an AMOLED pixel driving method, applicable to the above AMOLED pixel driving circuit, the method comprising:

Step S1: for a positive integer n, the scan signal on the n-th scan line being a constant low voltage to control the first P-type TFT in the n-th row of sub-pixels to be turned on, and control the voltage switching module connected to the n-th row of sub-pixels to input the first power source positive voltage to the sources of the second TFTs in the n-th row of sub-pixels, and a plurality of data lines inputting the data signal to the gates of the second TFTs of the n-th row of sub-pixels;

Step S2: the scan signal on the n-th scan line being a constant high voltage to control the first P-type TFT in the n-th row of sub-pixels to be turned off, and control the voltage switching module connected to the n-th row of sub-pixels to input the second power source positive voltage to the sources of the second TFTs in the n-th row of sub-pixels, and the OLED emitting light.

The present invention also provides an AMOLED pixel driving circuit, comprising: a plurality of sub-pixels arranged in an array, a plurality of scan lines, a plurality of data lines, and a plurality of voltage switching modules;

each column of sub-pixels being connected to a data line; each row of sub-pixels being correspondingly connected with a scan line; each voltage switching module being correspondingly connected with a row of sub-pixels and the scan line connected by the row of sub-pixel elements, and connected to a first power source positive voltage and a second power source positive voltage;

each of the sub-pixels comprising a first N-type TFT, a second TFT, a capacitor, and an OLED; the first N-type TFT having a gate electrically connected to the corresponding scan line, a source electrically connected to the corresponding data line, and a drain electrically connected to a gate of the second TFT; the second TFT having a drain electrically connected to to power source positive voltage, and a source electrically connected to an anode of the OLED; the capacitor having two ends electrically connected to the gate and the source of the second TFT respectively; the OLED having a cathode connected to the corresponding voltage switching module;

the voltage switching module being configured to input the first power source negative voltage to the cathodes of the OLEDs of the corresponding row of sub-pixels when the scan signal on the scan line connected thereto turning on the first N-type TFTs in the corresponding row of sub-pixels, and to input the second power source negative voltage to the cathodes of the OLEDs of the corresponding row of sub-pixels when the scan signal on the scan line connected thereto turning off the first N-type TFTs in the corresponding row of sub-pixels;

the first power source negative voltage being larger than the second power source negative voltage.

Wherein, each voltage switching module comprises a third N-type TFT and a fourth P-type TFT, the third N-type TFT has a gate electrically connected to the corresponding scan line, a source connected to the first power supply negative voltage and a drain electrically connected to a drain of the fourth P-type TFT and electrically connected to the cathode of the OLED of the corresponding row of the sub-pixels; the fourth P-type TFT has a gate electrically connected to the corresponding scan line, and a source connected to the second power supply negative voltage.

Wherein, the second TFT is an N-type TFT.

The present invention also provides an AMOLED pixel driving method, applicable to the above AMOLED pixel driving circuit, the method comprising:

Step S1′: for a positive integer n, the scan signal on the n-th scan line being a constant high voltage to control the first N-type TFT in the n-th row of sub-pixels to be turned on, and control the voltage switching module connected to the n-th row of sub-pixels to input the first power source negative voltage to the cathodes of the OLEDs in the n-th row of sub-pixels, and a plurality of data lines inputting the data signal to the gates of the second TFTs of the n-th row of sub-pixels;

Step S2′: the scan signal on the n-th scan line being a constant low voltage to control the first N-type TFT in the n-th row of sub-pixels to be turned off, and control the voltage switching module connected to the n-th row of sub-pixels to input the second power source negative voltage to the cathodes of the OLEDs in the n-th row of sub-pixels, and the OLED emitting light.

The present invention provides the following advantages: the present invention provides an AMOLED pixel driving circuit, which is disposed with a voltage switching module corresponding to each row of sub-pixels, and the voltage switching module is connected to a corresponding row of sub-pixels and scan line corresponding to the row of sub-pixels. The scan signal on the scan line controls the corresponding voltage switching module to provide different power supply voltages to the row of sub-pixels when the switching TFTs in the corresponding row of sub-pixels are turned on and off, thereby compensating for the voltage difference change caused by the parasitic capacitance between the drain and the gate of the switching TFT when the switching TFT changes from on to off, ensuring a stable current flowing through the OLED, and improving the display consistency of the sub-pixels to ensure display quality. The present invention provides an AMOLED pixel driving method capable of improving the brightness change of the OLED caused by the parasitic capacitance between the gate and the drain of the switching TFT when the scan signal turns off the switching TFT to improve display quality.

