This application claims the priority benefit of Taiwan application serial no. 107103335, filed on Jan. 30, 2018. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The invention relates to a light emitting diode compensation circuit and a display panel, and particularly relates to a compensation circuit adapted to compensate a threshold voltage in a non-display region and a display panel.
With the progress of technology, light emitting diodes (LEDs) have been broadly applied in display technologies. Also, active-matrix organic light emitting diodes (AMOLED) have become a key aspect in the development of display technologies. During the manufacturing process of an AMOLED display panel, an excimer-laser annealing (ELA) process may be performed to manufacture a low temperature polycrystalline silicon thin film transistor (LTPS-TFT) device on the AMOLED display panel.
However, the power of each excimer laser output may differ in the ELA process. Therefore, the LTPS-TFT devices on a display panel may have non-uniform electrical properties, and frames displayed may be affected and also non-uniform.
For example, during the ELA process performed on the LTPS-TFT devices of a display panel, when the excimer laser scans one column after another, the LTPS-TFT devices of the same column may substantially have the same electrical properties. For example, threshold voltages of the LTPS-TFT devices of the same column may be the same. However, since the powers of respective excimer laser outputs may differ, the LTPS-TFT devices of the respective columns may have different electrical properties, such as different threshold voltages.
Thus, how to compensate the electrical properties during the manufacturing process of the LPTS-TFT devices has become an issue to facilitate the display uniformity of the AMOLED display panel.
One or some exemplary embodiments of the invention provide a threshold voltage compensation circuit and a display panel capable of facilitating the display uniformity of a display panel.
A display panel according to an embodiment of the invention has a periphery region and a display region. The display panel includes a pixel column, a threshold voltage compensation circuit, and an operator. The pixel column is disposed in the display region and has a plurality of pixels coupled to a data line. The threshold voltage compensation circuit is disposed in the periphery region. The threshold voltage compensation circuit includes a threshold voltage detection circuit and an operator. The threshold voltage detection circuit is electrically coupled to the data line. The threshold voltage detection circuit includes a first transistor, a compensation transistor, and a second transistor. The first transistor has a first end, a second end, and a control end. The first end of the first transistor and the control end of the first transistor are configured to receive a compensation voltage. The compensation transistor outputs threshold voltage information of the compensation transistor based on the compensation voltage and has a first end, a second end, and a control end. The second end of the first transistor is coupled to the control end of the compensation transistor, the control end of the first transistor is coupled to the second end of the compensation transistor, and the first end of the compensation transistor is coupled to the control end of the compensation transistor; and The second transistor has a first end, a second end, and a control end. The first end of the compensation transistor is coupled to the first end of the second transistor. The operator is electrically coupled to the threshold voltage detection circuit and configured to generate compensated display data based on the threshold voltage information and display data.
A threshold voltage compensation circuit according to an embodiment of the invention is disposed in a periphery region. The threshold voltage compensation circuit includes a threshold voltage detection circuit and an operator. The threshold voltage detection circuit is electrically coupled to a data line of the display panel. The threshold voltage detection circuit includes a first transistor, a compensation transistor, and a second transistor. The first transistor has a first end, a second end, and a control end. The first end of the first transistor and the control end of the first transistor are configured to receive a compensation voltage. The compensation transistor outputs threshold voltage information of the compensation transistor based on the compensation voltage. The compensation transistor has a first end, a second end, and a control end. The second end of the first transistor is coupled to the control end of the compensation transistor, the control end of the first transistor is coupled to the second end of the compensation transistor, and the first end of the compensation transistor is coupled to the control end of the compensation transistor. The second transistor has a first end, a second end, and a control end. The first end of the compensation transistor is coupled to the first end of the second transistor. The operator is electrically coupled to the threshold voltage detection circuit and configured to generate compensated display data based on the threshold voltage information and display data.
Generally, in the threshold voltage compensation circuit according to the embodiments of the invention, the compensation transistor is reset and outputs the threshold voltage information, and the operator receives the threshold voltage information and computes based on the threshold voltage information and the display data to generate the compensated display data. Accordingly, the threshold voltages of the each pixel columns may be compensated based on the compensated display data, so as to effectively facilitate the display uniformity of the display panel.
In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
In the following, the principle of the disclosure will be described with the accompany drawings and detailed description. After learning the embodiments of the disclosure, people of ordinary skills in the art may change and modify the technology taught in the disclosure without departing from the spirit and scope of the disclosure.
Regarding the terms such as “first”, “second”, and the like used hereinafter, such terms do not specifically denote a sequence or an order, and do not serve to limit the invention, either. These terms are merely used to distinguish among the same components or operations described with the same technical terms.
The term “electrically coupling/coupled” used hereinafter may refer to that two or more components in direct physical or electrical contact or that two or more components in indirect physical or electrical contact. Meanwhile, the term “electrically coupling/coupled” may also refer to that two or more components are operated or moved with respect to each other.
Terms such as “comprise”, “have”, “include”, and/or the like used hereinafter should be considered as open-ended terms meaning “including but not limited to”.
The term “and/or” used hereinafter covers any one of or all the combinations of the described components.
Unless specifically noted, terms used hereinafter mainly bear the general meanings used in the field, the disclosure, and special contents. Some terms used to describe the disclosure are discussed below or elsewhere in the specification to provide additional guidance on the descriptions of the disclosure for people skilled in the art.
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The threshold voltage detection circuit 112 receives a compensation voltage VCOMP and is configured to generate threshold voltage information VDEC to the operator 114 when the display panel 100 is booting, i.e., before the display panel 100 enters a frame period. The compensation voltage VCOMP may be an external signal from a timing controller (not shown). The threshold voltage detection circuit 112 includes a transistor ET1, a transistor ET2, and a transistor ET3. Each of the transistors includes a first end, a second end, and a control end. In addition, the first end of the transistor ET1 and the control end of the transistor ET1 are configured to receive the compensation voltage VCOMP. Namely, in the transistor ET1, the first end of the transistor ET1 and the control end of the transistor ET1 are connected via diode connection. The second end of the transistor ET1 is coupled to the control end of the transistor ET2, and the control end of the transistor ET1 is coupled to the second end of the transistor ET2. The first end of the transistor ET2 is coupled to the control end of the transistor ET2. In other words, in the transistor ET2, the first end of the transistor ET2 is connected to the control end of the transistor ET2 via diode connection. The first end of the transistor ET2 is coupled to the first end of the transistor ET3, and the second end of the transistor ET3 is coupled to the operator 114.
The operator 114 is electrically coupled to the transistor ET3 of the threshold voltage detection circuit 112 and is configured to receive the threshold voltage information VDEC from the threshold voltage detection circuit 112. In addition, the operator 114 may perform computation based on the threshold voltage information VDEC and display data SDATA to generate compensated display information SDATAC, and output a data voltage to the corresponding pixel column 120 during the frame period to enable the corresponding pixel PX. In an embodiment of the invention, for example, the operator 114 may be an adder incorporated in the data driver 130, and the threshold voltage information VDEC is received via the pin of the data driver 130. The threshold voltage compensation circuit 110 may further include an analog-to-digital converter ADC and a memory 116. The analog-to-digital converter ADC converts the received threshold voltage information VDEC from an analog signal to a digital signal, and temporarily stores the threshold voltage information VDEC in the memory 116. After the display data SDATA is received, the compensated display data SDATAC is generated through the adder unit. Then, a digital-to-analog converter DAC in the data driver 130 may convert the compensated display data SDATAC from a digital signal to an analog signal. The pin (not shown) of the data driver 130 outputs the data voltage. However, the invention is not limited thereto. Each of the operator 114, the analog-to-digital converter ADC, and the memory 116 may be disposed on an array substrate, a flexible printed circuit board (FCB), or be integrated in the data driver 130.
In another embodiment of the invention, the threshold voltage compensation circuit 110 may include a switch SW1 and a switch SW2 disposed in the data driver 130. The switch SW1 is connected between the pin (not shown) and the analog to digital converter ADC. Based on the timing in the data driver 130, the switch SW1 is turned on, and the threshold voltage information VDEC is received. The switch SW2 is coupled between the digital-to-analog converter DAC and the pin. Based on the timing in the data driver 130, the switch SW2 is turned on, and the data voltage is output. The switch SW1 and the switch SW2 may be switches formed in an integrated circuit in the form of a metal oxide semiconductor field effect transistor (MOSFET) or a transmission gate. However, the invention is not limited thereto.
In another embodiment of the invention, a transistor ET4 may be further disposed between the data driver 130 and the data line DL. Taking an embodiment of the invention as an example, since the pin receiving the threshold voltage information VDEC and the pin outputting the data voltage in the data driver 130 are shared, a first end of the transistor ET4 is coupled to the second end of the transistor ET3, a second end of the transistor ET4 is coupled to the data line DL, and a control end of the transistor ET4 receives a selection signal SE4. Based on the selection signal SE4, the transistor ET4 is turned on to output the data voltage to the data line DL. The transistors ET1 to ET4 and transistors T1 to T2 are P-type thin film transistors. However, the invention is not limited thereto. In another embodiment, the transistors ET1 to ET4 and the transistors T1 to T2 may also be N-type thin film transistors.
In an embodiment of the invention, each pixel PX may be a basic pixel circuit having two transistors and one capacitor (2T1C). The pixel PX includes the transistor T1, the transistor T2, a capacitor C2t, and a light emitting diode D. Each of the transistors has a first end, a second end, and a control end. The first end of the transistor T1 is coupled to the data line DL, the second end of the transistor T1 is coupled to the control end of the transistor T2, the first end of the transistor T2 is configured to receive a voltage OVDD, the second end of the transistor T2 is coupled to an anode of the light emitting diode D, the capacitor Cst may be coupled between the first end/second end of the transistor T2 and the control end, and a cathode of the light emitting diode is configured to receive a voltage OVSS. However, the invention is not limited thereto.
In a thermal treatment of the display panel 100, the display panel 100 may be subjected to an excimer-laser annealing (ELA) process sequentially scanning each of the columns. In other words, when the ELA process is performed on each column of the display panel 100 to carry out the thermal treatment, the transistors in the same column direction are subjected to the thermal treatment at the same time. Therefore, the threshold voltage detection circuit 112 and the pixel column 120 of the same column are subjected to the thermal treatment at the same time. Accordingly, the transistors in the same column may have substantially equal electrical properties. Namely, the threshold voltages of the transistors in the same column are substantially equal. Therefore, the threshold voltage of the transistor T2 (i.e., the driving transistor) of the pixel PX and the transistor ET2 of the threshold voltage detection circuit 112 may be considered as equal. According to an embodiment of the invention, during a blanking period without entering the frame period, the threshold voltage of the transistor is detected by the threshold voltage detection circuit 112 disposed in the periphery region SA, and computation on the threshold voltage information VDEC generated accordingly and the display data SDATA are carried out to generate the compensated display data SDATAC. During the frame period, the compensated display data SDATAC is written into the corresponding pixel PX. By disposing the threshold voltage detection circuit 112 in the periphery region SA, an aperture ratio of the pixel PX may be increased. In the known basic pixel circuit, the threshold voltage of the driving transistor of each pixel needs to be compensated during each pixel refresh period. Comparatively, since the embodiments of the invention disclose that the threshold voltage of the transistor is detected during the blanking period without entering the frame period, the time for threshold voltage detection is not affected by a refresh rate and a resolution of the display device. Thus, it is not necessary for the pixel PX to compensate the threshold voltage of the driving transistor during the pixel refresh period. Therefore, an emitting period of the pixel PX is lengthened.
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The operation of the display panel 100 is described in detail below. Referring to
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In view of the foregoing, in the threshold voltage compensation circuit according to the embodiments of the invention, the compensation transistor is reset and outputs the threshold voltage information, and the operator receives the threshold voltage information and computes based on the threshold voltage information and the display data to generate the compensated display data. Accordingly, the threshold voltages of the driving transistors in the respective pixel columns may be compensated based on the compensated display data, so as to effectively facilitate the display uniformity of the display panel.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
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