Patent ID: 12205539

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

To help a person skilled in the art better understand the solutions of the present disclosure, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are a part rather than all of the embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present disclosure.

It is understood that terminologies, such as “center,” “longitudinal,” “horizontal,” “length,” “width,” “thickness,” “upper,” “lower,” “before,” “after,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise,” are locations and positions regarding the figures. These terms merely facilitate and simplify descriptions of the embodiments instead of indicating or implying the device or components to be arranged on specified locations, to have specific positional structures and operations. These terms shall not be construed in an ideal or excessively formal meaning unless it is clearly defined in the present specification. In addition, the term “first”, “second” are for illustrative purposes only and are not to be construed as indicating or imposing a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature that limited by “first”, “second” may expressly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of “plural” is two or more, unless otherwise specifically defined.

All of the terminologies containing one or more technical or scientific terminologies have the same meanings that persons skilled in the art understand ordinarily unless they are not defined otherwise. For example, “arrange,” “couple,” and “connect,” should be understood generally in the embodiments of the present disclosure. For example, “firmly connect,” “detachablely connect,” and “integrally connect” are all possible. It is also possible that “mechanically connect,” “electrically connect,” and “mutually communicate” are used. It is also possible that “directly couple,” “indirectly couple via a medium,” and “two components mutually interact” are used.

All of the terminologies containing one or more technical or scientific terminologies have the same meanings that persons skilled in the art understand ordinarily unless they are not defined otherwise. For example, “upper” or “lower” of a first characteristic and a second characteristic may include a direct touch between the first and second characteristics. The first and second characteristics are not directly touched; instead, the first and second characteristics are touched via other characteristics between the first and second characteristics. Besides, the first characteristic arranged on/above/over the second characteristic implies that the first characteristic arranged right above/obliquely above or merely means that the level of the first characteristic is higher than the level of the second characteristic. The first characteristic arranged under/below/beneath the second characteristic implies that the first characteristic arranged right under/obliquely under or merely means that the level of the first characteristic is lower than the level of the second characteristic.

Different methods or examples are introduced to elaborate different structures in the embodiments of the present disclosure. To simplify the method, only specific components and devices are elaborated by the present disclosure. These embodiments are truly exemplary instead of limiting the present disclosure. Identical numbers and/or letters for reference are used repeatedly in different examples for simplification and clearance. It does not imply that the relations between the methods and/or arrangement. The methods proposed by the present disclosure provide a variety of examples with a variety of processes and materials. However, persons skilled in the art understand ordinarily that the application of other processes and/or the use of other kinds of materials are possible.

The present disclosure proposes a pixel driving circuit to solve the problem that the conventional driving circuit using the MOS transistor as a driving transistor may not output exact current corresponding to high grey scales.

Please refer toFIG.1illustrating a block diagram of a pixel driving circuit10according to a preferred embodiment of the present disclosure.

The pixel driving circuit10is used in a display panel which includes scan lines and data lines. The pixel driving circuit10includes a switch circuit11, a storage circuit coupled to the switch circuit, and a light driving circuit13. The switch circuit11conducts data signal DATA applied on the data line in response to scan signal SCAN applied on the scan line. The storage circuit12is charged by the data signal DATA and the light driving circuit13is driven by the data signal DATA to emit light.

The light driving circuit13includes a driving unit14, light-emitting unit15, a supply voltage end1, a ground end2, and a voltage dividing unit16that is coupled between the driving unit14and the ground end2.

In this embodiment, the voltage dividing unit16is connected in series between the driving unit14and the ground end2. The driving unit14drives the light-emitting unit15to emit light according to the data signal DATA when the voltage is divided by the voltage dividing unit16, so that the change in current of the light-emitting unit15caused by the change of the data signal DATA received by the driving unit14can be reduced. The current change of the pixel driving circuit10can realize the display control under high gray scales.

Please refer toFIG.2illustrating a circuit diagram of the pixel driving circuit10according to a preferred embodiment of the present disclosure.

The switch circuit11includes a thin film transistor T1. The storage circuit12is a capacitor Cs. The driving circuit14is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) T2. The light-emitting unit15includes four light emitting diodes (LEDs). The voltage dividing unit16includes a resistor R.

The gate of the thin film transistor T1is electrically connected to the scan line, the drain of the thin film transistor T1is electrically connected to the data line, the source of the thin film transistor T1is electrically connected to one end of the capacitor Cs and the gate of the MOS transistor T2. The thin film transistor T1can be an amorphous silicon thin film transistor (a-Si TFT) or an indium gallium zinc oxide thin film transistor (IGZO TFT). It should be noted that in this embodiment, the switch circuit11only includes one thin film transistor. However, in another embodiments, the switch circuit11may also include multiple thin film transistors. The multiple thin film transistors may be connected in series or in parallel, and the gate of each thin film transistor is connected to the scan line. In the embodiment where multiple thin film transistors are connected in parallel, the drain of each thin film transistor is used to access the data signal DATA. In the embodiment where multiple thin film transistors are connected in series, a drain of one of thin film transistors is connected to the data signal DATA.

One end of the capacitor Cs is electrically connected to the gate of the MOS transistor T2and the source of the thin film transistor T1, and the other end of the capacitor Cs is electrically connected to the ground end2. In this embodiment, the storage circuit12includes only one capacitor. In other embodiments of the present disclosure, the storage module12may include multiple capacitors connected in series or in parallel. In the embodiment where multiple capacitors are connected in parallel, one end of each capacitor is electrically connected to the gate of the MOS transistor T2and the source of the thin film transistor T1, and the other end is electrically connected to the ground end2. In the embodiment, one end of one of the plurality of capacitors is electrically connected to the gate of the MOS transistor T2and the source of the thin film transistor T1, and one end of the other of the plurality of capacitors is electrically connected to the ground end2.

The gate of the MOS transistor T2is electrically connected to the source of the thin film transistor T1and the capacitor Cs, the drain of the MOS transistor T2is electrically connected to the cathode of the light emitting diode LED, the source of the MOS transistor T2is electrically connected to the resistor R. The MOS transistor T2is used as a driving transistor in the pixel driving circuit10. The anode of the light emitting diode LED is electrically connected to the supply voltage end1, and the cathode of the light emitting diode LED is electrically connected to the drain of the MOS transistor T2. In this embodiment, the light-emitting unit15includes four LEDs connected in series. In this embodiment, the light-emitting unit15is connected between the supply voltage end1and the driving unit14. In another embodiment, the light-emitting unit15may be connected between the driving unit14and the ground end2.

The resistor R is connected in series between the source of the MOS transistor T2and the ground end2. In this embodiment, the voltage divider unit16includes only one resistor, and the resistance of the resistor is ranged between 100 ohms to 300 ohms. In other embodiments, the voltage dividing unit16may include multiple resistors, and the multiple resistors may be connected in series or in parallel.

During the operation of the pixel driving circuit10, when the scan signal SCAN is a high-level signal, the thin film transistor T1is turned on, and the data signal DATA is fed into the gate of the MOS transistor T2and the capacitor Cs through the drain of the thin film transistor T1. After that, the thin film transistor T1is turned off. Due to the storage effect of the capacitor Cs, the gate voltage of the MOS transistor T2can still maintain the potential of the data signal DATA, so that the MOS transistor T2is still turned on to induce driving current flowing through the MOS transistor T2to drive the light-emitting diode LED to emit light.

Please refer toFIGS.3aand3b.FIG.3ais a characteristic curve diagram of the MOS transistor T2of the pixel driving circuit10without the resistor R.FIG.3bis a characteristic curve diagram of the MOS transistor T2of the pixel driving circuit10with the resistor R. InFIGS.3aand3b, x-axis represents source-drain voltage (Uds) of the MOS transistor T2, and y-axis represents source-drain current (Ids) of the MOS transistor T2. Each curve indicates: when the gate-source voltage (Vgate) of the MOS transistor T2remains unchanged, the source-drain current (Ids) changes with the source-drain voltage (Uds). Further, given that the gate-source voltage (Vgate) of the MOS transistor T2maintains a constant value, the MOS transistor T2works in the constant current region (i.e., the saturation region) when the source-drain voltage (Uds) increases to a certain value. The source-drain current (Ids) no longer increases with the increase of the source-drain voltage (Uds), but tends to a certain value. Further, the greater the gate-source voltage (Vgate) of the MOS transistor T2is, the greater the source-drain current (Ids) when it works in the constant current region is.

When the pixel driving circuit10is operating, the MOS transistor T2works in the constant current region. At this time, in the case that there is no resistor R between the source of the MOS transistor T2and the ground end GND, voltage (Vgate) across the gate and source of the MOS transistor T2is “DATA-GND”. High gray-scale voltage (that is, high DATA voltage) received by the pixel driving circuit10induces large source-drain current (Ids) which is easily exceed the maximum current allowed by the light-emitting diode LED. In addition, a small change in the voltage (Vgate) across the gate and source of the MOS transistor T2at a larger value will induce a large change in the source-drain current (Ids). The change of the current (Ids) is not conducive to enabling the pixel driving circuit10to perform display control under high gray scale. In this embodiment, because the resistor R is connected in series between the source of the MOS transistor T2and the ground end GND, when the MOS transistor T2receives the same gray-scale voltage DATA, voltage (Vgate) across the gate and source of the MOS transistor T2is divided and reduced to “DATA-GND-I*R”, effectively reducing source-drain current (Ids). Referring toFIG.3c, when the magnitude of the data signal DATA changes, the source-drain current(Ids) of the MOS transistor T2is also correspondingly smaller, so that the pixel driving circuit10can be implemented display control in high grayscale.

Specifically, the number of gray levels of the display panel is proportional to the resistance of the resistor R. The higher the number of levels of gray scales of the display panel is, the greater the resistance of the resistor R is. The lower the number of levels of gray scales of the display panel is, the smaller the resistance of resistor R is.

Further, the resistor R has a first resistance R1, the light emitting diode LED has a second resistance R2. A ratio of the supply voltage VDD fed to the pixel driving circuit10and a sum of the first resistance R1of the resistor R and the second resistance R2of the light emitting diode LED is between values of a minimum driving current Iminand a maximum driving current Imaxof the light emitting diode LED, i.e. Imin<VDD/(R1+R2)<Imax.

The pixel driving circuit10adopts a 2T1C (two transistors and one capacitor) architecture. In other embodiments, the pixel driving circuit may be 3T1C (three transistors and one capacitor), 7T1C (seven transistors and one capacitor), and so on. For example, in the 3T1C architecture, the source of a compensation transistor is connected in series to the source of the MOS transistor T2, and the gate and drain of the compensation transistor receive the sensing voltage and the reference voltage respectively.

In contrast to prior art, the present disclosure proposes the pixel driving circuit10used in a display panel having a scan line and a data line. The pixel driving circuit10includes a switch circuit11, a storage circuit12, and a light driving circuit13. The switch circuit11is configured to receive data signal DATA applied on the data line in response to scan signal SCAN applied on the scan line. The storage circuit12, electrically connected to the switch circuit11, is configured to be charged by the data signal DATA. The light driving circuit13is configured to emit light in response to the data signal DATA. The light driving circuit13has a driving unit14, a light-emitting unit15, a supply voltage end1, a ground end2, and a voltage dividing unit16that is coupled between the driving unit14and the ground end2. According to the present disclosure, the driving unit14drives the light-emitting unit15to emit light in response to the data signal DATA when the voltage is divided by the voltage dividing unit16, so that the change in current of the light-emitting unit15caused by the change of the data signal DATA received by the driving unit14can be reduced. The current change of the pixel driving circuit10can realize the display control under high gray scales.

Please refer toFIG.4illustrating a schematic diagram of a mobile terminal according to another embodiment of the present disclosure. The pixel driving circuit10is used in the mobile terminal which can be a smart phone or a tablet computer.

The mobile terminal100comprises a processor101and a memory102coupled to the processor102.

The processor180is a control center of the mobile terminal100, and connects various parts of the terminal by using various interfaces and lines. By running or executing the software program and/or module stored in the memory102, and invoking data stored in the memory102, the processor101performs various functions and data processing of the mobile terminal100, thereby performing overall monitoring on the mobile phone.

FIG.5is a block diagram of a mobile terminal100according to one embodiment of the present disclosure. The mobile terminal100may be a smart phone or a tablet computer.

As shown inFIG.5, the mobile terminal100may comprise components, such as a radio frequency (RF) circuit110, a memory120, an input unit130, a display unit140, a sensor150, an audio circuit160, a transmission module170, a processor180including one or more (only one is shown in the figure) processing cores, and a power supply190, etc. Those skilled in the art would understand that the mobile terminal100is not limited to the structure of the mobile terminal100shown inFIG.5. The mobile terminal100may comprise more or less components than those illustrated in the figure, or some components may be combined, or may have different components arrangements.

The RF circuit110may be configured to receive and send a signal during an information receiving and sending process or a conversation process. Specifically, after receiving downlink information from a base station, the RF circuit110delivers the downlink information to one or more processors180for processing, and sends related uplink data to the base station. Generally, the RF circuit110includes, but is not limited to, an antenna, at least one amplifier, a tuner, one or more oscillators, a subscriber identity module (SIM) card, a transceiver, a coupler, a low noise amplifier (LNA), and a duplexer. In addition, the RF circuit110may also communicate with a network and another device by wireless communication. The wireless communication may use any communications standard or protocol, which includes, but is not limited to, a Global System for Mobile communications (GSM), an Enhanced Data GSM Environment (EDGE), a Wideband Code Division Multiple Access (WCDMA), a Code Division Access (CDMA), a Time Division Multiple Access (TDMA), a Wireless Fidelity (Wi-Fi) such as IEEE 802.11a, IEEE 802.11b, IEEE802.11g and IEEE 802.11n, a Voice over Internet Protocol (VoIP), a Worldwide Interoperability for Microwave Access (Wi-Max), any other protocols for e-mail, instant communication and short message, and the like.

The memory120may be configured to store a software program and module. The processor180runs the software program and module stored in the memory120, to implement various functional applications and data processing. The memory120may mainly include a program storage area and a data storage area. The program storage area may store an operating system, an application program required by at least one function (such as a sound playback function and an image display function), and the like. The data storage area may store data (such as audio data and an address book) created according to use of the mobile terminal100, and the like. In addition, the memory120may include a high speed random access memory, and may also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or another volatile solid-state storage device. Correspondingly, the memory120may further include a memory controller, so that the processor180and the input unit130access the memory120.

The input unit130may be configured to receive input digit or character information, and generate keyboard, mouse, joystick, optical, or track ball signal input related to the user setting and function control. Specifically, the input unit130may include a touch-sensitive surface131and other input device132. The touch-sensitive surface131may also be referred to as a touch screen or a touch panel, and may collect a touch operation of a user on or near the touch-sensitive surface (such as an operation of a user on or near the touch-sensitive surface131by using any suitable object or attachment, such as a finger or a stylus), and drive a corresponding connection apparatus according to a preset program. Optionally, the touch-sensitive surface131may include two parts: a touch detection apparatus and a touch controller. The touch detection apparatus detects a touch position of the user, detects a signal generated by the touch operation, and transfers the signal to the touch controller. The touch controller receives the touch information from the touch detection apparatus, converts the touch information into touch point coordinates, and sends the touch point coordinates to the processor180. Moreover, the touch controller can receive and execute a command sent from the processor180. In addition, the touch-sensitive surface131may be implemented by using various types, such as a resistive type, a capacitance type, an infrared type, and a surface sound wave type. In addition to the touch-sensitive surface131, the input unit130may further include the another input device132. Specifically, the another input device132may include, but is not limited to, one or more of a physical keyboard, a functional key (such as a volume control key or a switch key), a track ball, a mouse, and a joystick.

The display unit140may be configured to display information input by the user or information provided for the user, and various graphical user ports of the mobile terminal100. The graphical user ports may be formed by a graph, a text, an icon, a video, and any combination thereof. The display unit140may include a display panel141. Optionally, the display panel141may be configured by using a liquid crystal display (LCD), an organic light-emitting diode (OLED), or the like. Further, the touch-sensitive surface131may cover the display panel141. After detecting a touch operation on or near the touch-sensitive surface131, the touch-sensitive surface131transfers the touch operation to the processor180, so as to determine a type of a touch event. Then, the processor180provides corresponding visual output on the display panel141according to the type of the touch event. Although, inFIG.5, the touch-sensitive surface131and the display panel141are used as two separate parts to implement input and output functions, in some embodiments, the touch-sensitive surface131and the display panel141may be integrated to implement the input and output functions.

The mobile terminal100may further include at least one sensor150, such as an optical sensor, a motion sensor, and other sensors. Specifically, the optical sensor may include an ambient light sensor and a proximity sensor. The ambient light sensor may adjust luminance of the display panel141according to brightness of the ambient light. The proximity sensor may switch off the display panel141and/or backlight when the mobile terminal100is moved to the ear. As one type of motion sensor, a gravity acceleration sensor may detect magnitude of accelerations at various directions (which generally are triaxial), may detect magnitude and a direction of the gravity when static, and may be configured to identify an application of a mobile phone attitude (such as switching between horizontal and vertical screens, a related game, and attitude calibration of a magnetometer), a related function of vibration identification (such as a pedometer and a knock). Other sensors, such as a gyroscope, a barometer, a hygrometer, a thermometer, and an infrared sensor, which may be configured in the mobile terminal100are not further described herein.

The audio circuit160, a loudspeaker161, and a microphone162may provide audio interfaces between the user and the mobile terminal100. The audio circuit160may transmit, to the loudspeaker161, a received electric signal converted from received audio data. The loudspeaker161converts the electric signal into a sound signal for output. On the other hand, the microphone162converts a collected sound signal into an electric signal. The audio circuit160receives the electric signal and converts the electric signal into audio data, and outputs the audio data to the processor180for processing. Then, the processor180sends the audio data to, for example, another terminal by using the RF circuit110, or outputs the audio data to the memory120for further processing. The audio circuit160may further include an earplug jack, so as to provide communication between a peripheral earphone and the mobile terminal100.

The mobile terminal100may help, by using the transmission module170(e.g. Wi-Fi module), a user to receive and send an e-mail, browse a webpage, and access stream media, and the like, which provides wireless broadband Internet access for the user. AlthoughFIG.3shows the transmission module170, it may be understood that, the wireless communications unit is not a necessary component of the mobile terminal100, and can be ignored according to demands without changing the scope of the essence of the present disclosure.

The processor180is a control center of the mobile terminal100, and connects various parts of the terminal by using various interfaces and lines. By running or executing the software program and/or module stored in the memory120, and invoking data stored in the memory120, the processor180performs various functions and data processing of the mobile terminal100, thereby performing overall monitoring on the mobile phone. Optionally, the processor180may include one or more processing cores. Preferably, the processor180may integrate an application processor and a modem. The application processor mainly processes an operating system, a user interface, an application program, and the like. The modem mainly processes wireless communication. It may be understood that, the foregoing modem may not be integrated into the processor180.

The mobile terminal100further includes the power supply190(such as a battery) for supplying power to the components. Preferably, the power supply may be logically connected to the processor180by using a power supply management system, thereby implementing functions, such as charging, discharging, and power consumption management, by using the power supply management system. The power supply190may further include any component, such as one or more direct current or alternate current power supplies, a re-charging system, a power supply fault detection circuit, a power supply converter or an inverter, and a power supply state indicator.

Although not shown in the figure, the mobile terminal100may further include a camera (a front camera or a rear camera), a Bluetooth module, and the like, which are not further described herein. Specifically, in this embodiment, the display unit of the mobile terminal100is a touch screen display.

Above are embodiments of the present invention, which does not limit the scope of the present invention. Any modifications, equivalent replacements or improvements within the spirit and principles of the embodiment described above should be covered by the protected scope of the invention.

The present disclosure is described in detail in accordance with the above contents with the specific preferred examples. However, this present disclosure is not limited to the specific examples. For the ordinary technical personnel of the technical field of the present disclosure, on the premise of keeping the conception of the present disclosure, the technical personnel can also make simple deductions or replacements, and all of which should be considered to belong to the protection scope of the present disclosure.