Patent Grant
11341899
This is the U.S. National Stage of International Patent Application No. PCT/CN2019/106107, filed Sep. 17, 2019, which in turn claims the benefit of Chinese Patent Application No. 201910680801.X, filed Jul. 26, 2019.
The present invention relates to a display field, and more particularly to a pixel driving circuit and a display device.
In the active matrix display circuit, the pixel driving circuit could be categorized into two types of circuits, the time-division multiplexing circuit and the spatial multiplexing circuit.
The time-division multiplexing circuit is mainly implemented with a pulse width modulation (PWM) circuit. The PWM circuit could divide the display time of a row into multiple time periods and realize different grey levels by switching black/white in the time periods. However, the driving TFT is working in the linear region when the PWM circuit is working, this makes the switching frequency too high and a current driving IC cannot support such a high switching frequency. In addition, the spatial multiplexing circuit could divide the display region into multiple regions and realize different grey levels by displaying black/white in the multiple regions. This mechanism requires a larger display region.
From the above, the conventional pixel driving circuit has issues of high switching frequency or larger display region.
One objective of an embodiment of the present invention is to provide a pixel driving circuit and a display, which utilizes the spatial multiplexing mechanism with the time-division multiplexing mechanism to solve the above-mentioned issues of high switching frequency or larger display region.
According to an embodiment of the present invention, a pixel driving circuit is provided. The pixel driving circuit comprises: an addressing transistor; a driving transistor; a storage capacitor; and a plurality of pixel units connected in parallel. A drain of the addressing transistor is electrically connected to a gate of the driving transistor. A first end of the storage capacitor is connected to the gate of the driving transistor and a second end of the storage capacitor is connected to a drain of the driving transistor. The pixel units are connected to the drain of the driving transistor, the pixel units comprise at least one digital signal controller, and the digital signal controller is series connected to a plurality of lighting units. The gate of the addressing transistor receives a scan signal, the digital signal controller provides a digital signal, the scan signal and the digital signal makes the lighting units periodically generate lights such that a predetermined frame is displayed.
Optionally, a source of the driving transistor receives a positive power voltage, a cathode of the lighting units receives a negative power voltage, the scan signal, the positive power voltage and the negative power voltage together act on the driving transistor to form a current signal of the drain of the driving transistor. The digital signal controller provides the digital signal having a predetermined addressing period, the digital signal and the current signal are both transferred to an anode of the lighting units such that the current signal has a predetermined display period and the lighting units generates light in the predetermined display period. The predetermined addressing period and the predetermined display period constitute a predetermined period of the predetermined frame such that the lighting units constitute the predetermined frame.
Optionally, when the scan signal corresponds to a high impulse, the addressing transistor is turned on, the gate of the addressing gate receives the scan signal, and the storage capacitor stores the scan signal and transform the scan signal into a corresponding current signal. When the scan signal corresponds to a low impulse, the addressing transistor is turned off, the storage capacitor provides the current signal to the gate of the driving transistor. When a current value of the current signal reaches a current threshold of the driving transistor, the driving transistor is turned on and the lighting units generate light.
Optionally, the scan signal, the digital signal, and the current signal are superposed to indicate the predetermined addressing period and the predetermined display period in the predetermined period. In the predetermined addressing period, the scan signal is a high voltage impulse, the current signal corresponds to a low voltage level and the digital signal corresponds to a logic high level. In the predetermined display period, the scan signal is a low voltage impulse, the current signal corresponds to a high voltage level and the digital signal corresponds to a logic low level.
Optionally, in one of the pixel units, the predetermined display period is double of the predetermined addressing period in one predetermined period.
Optionally, the pixel units comprise a first pixel unit and a second pixel unit, the first pixel unit comprises a first digital signal controller and a lighting unit, and the first digital signal controller is electrically connected to an anode of the lighting unit. The second pixel unit comprises a second digital signal controller and two lighting unit connected in parallel, the second digital signal controller is electrically connected to anodes of the two lighting units connected in parallel to make a luminance of the second pixel unit be double of a luminance of the first pixel unit.
Optionally, the pixel units further comprise a third pixel unit, connected to the second pixel unit in parallel. The third pixel unit comprises a third digital signal controller electrically connected to anodes of a predetermined number of lighting units. The predetermined number of lighting units are connected in parallel. The predetermined number is an odd number times of a number of the lighting units of the second pixel unit such that a luminance of the third pixel unit is the odd number times of the luminance of the second pixel unit.
Optionally, the pixel driving circuit further comprises a plurality of vertical data lines and a plurality of horizontal scan lines. The data lines provide a data signal to a source of the addressing transistor, and the scan line provides the scan signal to the gate of the addressing transistor such that the drain of the addressing transistor provides a current signal to the storage capacitor.
Optionally, the digital signal controller is implemented with a low temperature poly silicon (LTPS) TFT, an oxide-semiconductor TFT, or an amorphous silicon TFT.
According to an embodiment of the present invention, a display device is provided. The display device comprises a pixel driving circuit. The pixel driving circuit comprises: an addressing transistor; a driving transistor; a storage capacitor; and a plurality of pixel units connected in parallel. A drain of the addressing transistor is electrically connected to a gate of the driving transistor. A first end of the storage capacitor is connected to the gate of the driving transistor and a second end of the storage capacitor is connected to a drain of the driving transistor. The pixel units are connected to the drain of the driving transistor, the pixel units comprise at least one digital signal controller, and the digital signal controller is series connected to a plurality of lighting units. The gate of the addressing transistor receives a scan signal, the digital signal controller provides a digital signal, the scan signal and the digital signal makes the lighting units periodically generate lights such that a predetermined frame is displayed.
Optionally, a source of the driving transistor receives a positive power voltage, a cathode of the lighting units receives a negative power voltage, the scan signal, the positive power voltage and the negative power voltage together act on the driving transistor to form a current signal of the drain of the driving transistor. The digital signal controller provides the digital signal having a predetermined addressing period, the digital signal and the current signal are both transferred to an anode of the lighting units such that the current signal has a predetermined display period and the lighting units generates light in the predetermined display period. The predetermined addressing period and the predetermined display period constitute a predetermined period of the predetermined frame such that the lighting units constitute the predetermined frame.
Optionally, when the scan signal corresponds to a high impulse, the addressing transistor is turned on, the gate of the addressing gate receives the scan signal, and the storage capacitor stores the scan signal and transform the scan signal into a corresponding current signal. When the scan signal corresponds to a low impulse, the addressing transistor is turned off, the storage capacitor provides the current signal to the gate of the driving transistor. When a current value of the current signal reaches a current threshold of the driving transistor, the driving transistor is turned on and the lighting units generate light.
Optionally, the scan signal, the digital signal, and the current signal are superposed to indicate the predetermined addressing period and the predetermined display period in the predetermined period. In the predetermined addressing period, the scan signal is a high voltage impulse, the current signal corresponds to a low voltage level and the digital signal corresponds to a logic high level. In the predetermined display period, the scan signal is a low voltage impulse, the current signal corresponds to a high voltage level and the digital signal corresponds to a logic low level.
Optionally, in one of the pixel units, the predetermined display period is double of the predetermined addressing period in one predetermined period.
Optionally, the pixel units comprise a first pixel unit and a second pixel unit, the first pixel unit comprises a first digital signal controller and a lighting unit, and the first digital signal controller is electrically connected to an anode of the lighting unit. The second pixel unit comprises a second digital signal controller and two lighting unit connected in parallel, the second digital signal controller is electrically connected to anodes of the two lighting units connected in parallel to make a luminance of the second pixel unit be double of a luminance of the first pixel unit.
Optionally, the pixel units further comprise a third pixel unit, connected to the second pixel unit in parallel. The third pixel unit comprises a third digital signal controller electrically connected to anodes of a predetermined number of lighting units. The predetermined number of lighting units are connected in parallel. The predetermined number is an odd number times of a number of the lighting units of the second pixel unit such that a luminance of the third pixel unit is the odd number times of the luminance of the second pixel unit.
Optionally, the pixel driving circuit further comprises a plurality of vertical data lines and a plurality of horizontal scan lines. The data lines provide a data signal to a source of the addressing transistor, and the scan line provides the scan signal to the gate of the addressing transistor such that the drain of the addressing transistor provides a current signal to the storage capacitor.
Optionally, the digital signal controller is implemented with a low temperature poly silicon (LTPS) TFT, an oxide-semiconductor TFT, or an amorphous silicon TFT.
In contrast to the conventional art, an embodiment of the present invention adds one or more digital signal controllers to control the lighting units to periodically generate light such that the spatial multiplexing mechanism and the time-division multiplexing mechanism are both used. This solves the issues of high switching frequency or larger display region.
To describe the technical solutions in the embodiments of this application more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of this application, and a person of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.
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.
Please refer to
The gate of the addressing transistor T1 receives a scan signal. The digital signal controller Ctr provide a digital signal DS. The scan signal scan and the digital signal DS make the lighting unit M periodically generate light to display a predetermined frame.
The source s of the driving transistor T2 receives a power positive voltage Vss. The cathode of the lighting unit M receives a power negative voltage Vdd. The scan signal scan, the power positive voltage Vss and the power negative voltage Vdd work together on the driving transistor T2 to form a current signal ES of the drain d of the driving transistor T2.
Please refer to
The predetermined addressing period TA and the predetermined display period TL constitute a predetermined period T of the predetermined frame such that the lighting unit M could constitute the predetermined frame.
The pixel driving circuit 10 further comprises a plurality of vertical data lines and a plurality of horizontal scan lines. The data lines provide a data signal data to the source s of the addressing transistor T1. The scan line provides the scan signal scan to the gate g of the addressing transistor T1 such that the drain d of the addressing transistor T1 provides a current signal ES to the storage capacitor Cst.
In this embodiment, through providing a digital signal controller Ctr and one or more lighting units M at the drain d of the driving transistor T2 of the pixel driving circuit, the digital signal controller Ctr provides a digital signal DS of the addressing period TA to the lighting unit M. The digital signal DS, the scan signal scan, the power positive voltage Vss and the power negative voltage Vdd all act on the driving transistor Ts to form the current signal RS of the drain d of the driving transistor T2 in the predetermined display period TL. This make the addressing period TA and the predetermined display period TL constitute the predetermined period T of the predetermined frame such that the pixel unit L has the predetermined period T of the predetermined frame and the lighting unit M could periodically generates light.
The theory for the pixel driving circuit 10 to periodically generate light is as below:
The scan signal scan comprises a high voltage impulse and a low voltage impulse. The scan signal scan varies to control the on/off condition of the addressing transistor T1.
When the scan signal scan is a high voltage impulse, the addressing transistor is turned on. The gate g of the first transistor T1 receives the scan signal scan. The storage capacitor Cst stores the scan signal scan and transforms the scan signal scan to the corresponding current signal ES.
When the scan signal scan is a low voltage impulse, the addressing transistor T1 is turned off. The storage capacitor Cst provides the current signal ES to the gate g of the driving transistor T2. When the current value of the current signal ES reaches the current threshold of the driving transistor TS, the driving transistor T2 is turned on such that the lighting unit M generates light.
In
In the predetermined addressing period TA, the scan signal scan is a high voltage impulse, the current signal ES corresponds to a low voltage level and the digital signal DS corresponds to a logic high level. At this time, the lighting unit M of the pixel driving circuit 10 generates light.
In the predetermined display period TL, the scan signal scan is a low voltage impulse, the current signal ES corresponds to a high voltage level and the digital signal DS corresponds to a logic low level. At this time, the lighting unit M of the pixel driving circuit 10 generates light.
The above embodiments explain how the pixel driving circuit 10 could periodically generate light. Then, the time-division multiplexing and the spatial multiplexing mechanisms of the pixel driving circuit 10 will be illustrated.
Please refer to
In the pixel driving circuit 11, the number of the pixel units L is one or more and the pixel units L are connected in parallel at the drain d of the driving transistor T2. The pixel units L comprise a first pixel unit L1 and a second pixel unit L2. The first pixel unit L1 comprises a first digital signal controller Ctr1 and a lighting unit M1. The first digital signal controller Ctr1 is connected to the anode of the lighting unit M1.
The second pixel unit L2 comprises a second digital signal controller Ctr2 and further comprises two lighting units M2 connected in parallel. The second digital signal controller Ctr2 is connected to the anodes of the two lighting units M2 such that the luminance of the second pixel unit L2 is double of the luminance of the first pixel unit L1 in the predetermined frame.
In the timing diagram of
From the above, in the pixel driving circuit 11, the predetermined display period TL is double of the predetermined addressing period TA in a predetermined period T. Therefore, for a pixel unit L, the amount of light generated by the lighting unit M in the predetermined display period TL is double of the amount of light generated by the lighting unit M in the predetermined addressing period TA. For example, assuming that in the first pixel unit L1, the grey level corresponding to the predetermined addressing period TA is 1, the grey level corresponding to the predetermined display period TA is 2. Further, because the luminance of the second pixel unit L2 is double of the luminance of the first pixel unit L1, in the second pixel unit L2, the grey level corresponding to the predetermined addressing period TA is 2, the grey level corresponding to the predetermined display period TA is 4.
Therefore, in the pixel driving circuit 11, when the overall grey level is 9, this grey level could be realized by turning on the first digital signal controller Ctr1 and the second digital signal controller Ctr2 such that the grey level is 1×1+1×2+1×2+1×4=9. In this way, the pixel driving circuit 11 could realize 9+1=10 different grey levels.
In the pixel driving circuit 11, only another one second pixel unit L2 is adopted. Further, the two parallel-connected lighting units M2 are used with the second digital controller Ctr2 such that multiple grey levels could be displayed. The pixel driving circuit 11 could reduce the occupied space of the pixel unit L and the signal switching frequency of the gate of the transistor while realizing displaying the multiple grey levels.
In another embodiment, the number of the pixel unit L is not limited to two. Please refer to
In the pixel driving circuit 12, the pixel units L are connected in parallel. The pixel unit L further comprises a third pixel unit L3. The third pixel unit L3 and the second pixel unit L2 are connected in parallel.
The third pixel unit L3 comprises a third digital signal controller Ctr3. The third digital signal controller Ctr3 is electrically connected to anodes of a predetermined number of lighting units M3. The predetermined number of lighting units M3 are connected in parallel. The predetermined number is an odd number times of the number of the lighting units L2 of the second pixel unit L2 such that the luminance of the third pixel unit L3 is the odd number times of the luminance of the second pixel unit L2. For example, from the above, it could be understood that the predetermined display period TL is double of the predetermined addressing period TA. Assuming that the number of the lighting units in the third pixel unit L3 is 4, the luminance (grey level) of the third pixel unit L3 should be double of that of the second pixel unit L2. The actual implementation is shown in table 2 below:
When the first digital signal controller Ctr1, the second digital signal controller Ctr2 and the third digital signal controller Ctr3 are all turned on, then the overall grey levels could be 1×1+1×2+1×2+1×4+1×4+1×8=21. Therefore, the pixel driving circuit 12 could realize 22 grey levels.
In some embodiments, the digital signal controller Ctr is connected to an external timing controller (not shown). The predetermined addressing period TA and the predetermined display period could be provided by the timing controller.
The addressing transistor T1 and the driving transistor T2 could be both implemented with a low temperature poly silicon (LTPS) thin film transistor (TFT), a oxide-semiconductor TFT, or an amorphous silicon TFT. The digital signal controller could be implemented with a low temperature poly silicon (LTPS) thin film transistor (TFT), an oxide-semiconductor TFT, or an amorphous silicon TFT.
Further, according to an embodiment of the present invention, a display device is provided. The display device comprises the above-mentioned pixel driving circuit in any one of the above-mentioned embodiments. The display device could be a cell phone, a laptop, a TV, a display, a tablet, a digital frame, a navigator, or any other devices or components having display functions.
An embodiment of the present invention adds one or more digital signal controllers to control the lighting units to periodically generate light such that the spatial multiplexing mechanism and the time-division multiplexing mechanism are both used. This solves the issues of high switching frequency or larger display region.
One of ordinary skill in the art may make variations, modifications, substitutions and alterations to the above embodiments within the scope of the present disclosure.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201910680801.X | Jul 2019 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2019/106107 | 9/17/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2021/017118 | 2/4/2021 | WO | A |
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| Number | Date | Country | |
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| 20210335216 A1 | Oct 2021 | US |
