Patent Application
20190221183
The present disclosure relates to the field of display devices, and particularly to a driving circuit for a display device, a voltage conversion circuit, a display device and a control method thereof.
In an existing display device, a voltage converter is mainly used to convert a supply voltage to voltages required by other components, such as an operating voltage required by a timing controller, a gate driver and a source driver, a gate line turn-on voltage and a gate line turn-off voltage required by the gate driver, a common voltage required by a display panel, and the like. During a normal process of powering off the display device, the voltage converter that loses supply power would use a charge stored in a capacitor to power some components in the display device for a short period of time, so as to enable relevant components to finish operations such as cleaning the screen.
An exemplary embodiment provides a driving circuit for a display device comprising a voltage converter and a source driver, the voltage converter comprising a first terminal for receiving a first voltage from a power supply and a second terminal for outputting a second voltage to the source driver. The driving circuit further comprises a switch sub-circuit and a voltage comparison sub-circuit. The switch sub-circuit is disposed in a voltage transmission path between the second terminal of the voltage converter and the source driver. The voltage comparison sub-circuit is connected to the first terminal of the voltage converter and configured to control the switch sub-circuit to disconnect the voltage transmission path if the first voltage is less than a reference voltage.
In some exemplary embodiments, the voltage converter further has a third terminal for outputting a constant voltage, the third terminal of the voltage converter being connected to the voltage comparison sub-circuit to provide the constant voltage as the reference voltage to the voltage comparison sub-circuit.
In some exemplary embodiments, the driving circuit further comprises a timing controller, and the third terminal of the voltage converter is further connected to the timing controller.
In some exemplary embodiments, the voltage comparison sub-circuit comprises a first resistor, a second resistor, and a voltage comparator, a first terminal of the first resistor is connected to the first terminal of the voltage converter, and a second terminal of the first resistor is connected to a first comparison input terminal of the voltage comparator, a first terminal of the second resistor is connected to the first comparison input terminal of the voltage comparator, and a second terminal of the second resistor is connected to a common voltage terminal, a second comparison input terminal of the voltage comparator is configured to receive the reference voltage, and a comparison output terminal of the voltage comparator is connected to the switch sub-circuit.
In some exemplary embodiments, the switch sub-circuit comprises a first transistor, a gate of the first transistor being connected to the voltage comparison sub-circuit, a source and a drain of the first transistor being connected to the second terminal of the voltage converter and the source driver, respectively.
Another exemplary embodiment provides a voltage conversion circuit, the voltage conversion circuit comprising a first terminal for receiving a first voltage from a power supply and a second terminal for outputting a second voltage to a source driver, wherein the voltage conversion circuit comprises a first voltage conversion sub-circuit, a voltage comparison sub-circuit and a switch sub-circuit. An input terminal of the first voltage conversion sub-circuit is connected to the first terminal of the voltage conversion circuit. An output terminal of the first voltage conversion sub-circuit is connected to the switch sub-circuit, and the first voltage conversion sub-circuit is configured to convert the first voltage into the second voltage. The switch sub-circuit is disposed in a voltage transmission path between the output terminal of the first voltage conversion sub-circuit and the second terminal of the voltage conversion circuit. The voltage comparison sub-circuit is connected to the first terminal of the voltage conversion circuit and the switch sub-circuit, respectively, and the voltage comparison sub-circuit is configured to control the switch sub-circuit to disconnect the voltage transmission path if the first voltage is less than a reference voltage.
In some exemplary embodiments, the voltage conversion circuit further comprises a second voltage conversion sub-circuit. An input terminal of the second voltage conversion sub-circuit is connected to the first terminal of the voltage conversion circuit, an output terminal of the second voltage conversion sub-circuit is connected to the voltage comparison sub-circuit, and the second voltage conversion sub-circuit is configured to convert the first voltage into a constant voltage to be provided to the voltage comparison sub-circuit as the reference voltage.
In some exemplary embodiments, the voltage comparison sub-circuit comprises a first resistor, a second resistor and a voltage comparator, a first terminal of the first resistor is connected to the first terminal of the voltage conversion circuit, and a second terminal of the first resistor is connected to a first comparison input terminal of the voltage comparator, a first terminal of the second resistor is connected to the first comparison input terminal of the voltage comparator, and a second terminal of the second resistor is connected to a common voltage terminal, a second comparison input of the voltage comparator is configured to receive the reference voltage, and a comparison output terminal of the voltage comparator is connected to the switch sub-circuit.
In some exemplary embodiments, the switch sub-circuit comprises a first transistor, a gate of the first transistor being connected to the voltage comparison sub-circuit, a source and a drain of the first transistor being connected to the second terminal of the voltage conversion circuit and the source driver, respectively.
A further exemplary embodiment provides a display device comprising the driving circuit or the voltage conversion circuit according to any one of above embodiments.
Yet another exemplary embodiment provides a control method for a display device, the display device comprising a voltage converter and a source driver, the voltage converter comprising a first terminal for receiving a first voltage from a power supply, and a second terminal for outputting a second voltage to the source driver, wherein the control method comprises: disconnecting a voltage transmission path between the second terminal of the voltage converter and the source driver in response to the first voltage being less than a reference voltage.
It can be understood that, without causing conflicts, various features in the exemplary embodiments described above may be selectively combined to obtain other embodiments. These embodiments also fall within the protection scope of the present disclosure.
In order to more clearly illustrate the technical solutions in embodiments of the present disclosure, the drawings required for describing the exemplary embodiments will be briefly introduced below. The drawings mentioned in the description below are merely some exemplary embodiments of the present disclosure. Reasonable modifications to the drawings are also encompassed within the scope of the present disclosure.
To make the objective, technical solutions and advantages of the disclosure clearer, exemplary embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are part of the exemplary embodiments of the disclosure, rather than all of them. All other embodiments obtained by those ordinarily skilled in the art based on the described exemplary embodiments herein without inventive efforts fall within the protection scope of the application. Unless otherwise defined, technical terms or scientific terms used herein are intended to have ordinary meanings understood by those skilled in the art. The words such as “first” “second” and the like used in the present disclosure do not denote any order, quantity, or importance, but are just used to distinguish different components. The words such as “comprising” and the like means that an element or item preceding the words is intended to encompass elements or items that are listed after the words and their equivalents, but not excluding other elements or items. The words such as “connected” or “linked”, and the like are not limited to physical or mechanical connections, but may include electrical connections, and the connections may be direct or indirect.
Inventors of the application have realized that, in some application scenes, the voltage at a supply voltage receiving terminal of the voltage converter in the display device may decrease too fast, so that the voltage provided to a relevant component has dropped below its required operating voltage in the case that the relevant component has not yet have time to complete operations relating to powering-off. For example, upon powering off, the gate driver in the display device needs to output a full-on control signal of a high level so as to output a gate line turn-on voltage to all the gate lines. However, the full-on control signal tends to decrease to a low level prematurely. As a result, some pixels cannot be completely restored to a reset state, resulting in defects such as a visible shadow effect upon powering off.
In an exemplary embodiment, the voltage converter mainly comprises a DC-DC voltage conversion circuit (which may be, for example, disposed in a chip). Of course, the voltage converter may also have other functions such as providing other voltages by conversion, and may have a respective number of connection terminals. Moreover, the voltage converter may include sub-circuits or components shared by multiple functions when having more than two functions at the same time.
The above-described driving circuit may further comprise other circuit structures not mentioned above. For example, the voltage converter 11 may be connected to a number of other circuits through a number of connection terminals respectively to provide required electrical signals for those circuits. In practice, other structures may be disposed in the driving circuit as needed, and examples of the driving circuit for a display device are not limited to the structure shown in
In a contrastive example, the driving circuit comprises a voltage converter 11 and a source driver 12 directly connected to each other, but does not comprise the switch sub-circuit 13 and the voltage comparison sub-circuit 14 described above. The first terminal of the voltage converter 11 is provided with a capacitor. The capacitor can be charged when the voltage converter 11 receives a voltage from a power supply, and the voltage converter 11 can be powered by charges stored in the capacitor for a period of time when it loses power supply. Thus, when the display device is powered off, with the charges stored in the capacitor, the voltage converter 11 will continue to output a plurality of electrical signals including the first voltage AVDD for a period of time so as to maintain the operating states of other circuit structures to which the electrical signals are provided. However, as the charges stored in the capacitor are consumed over time, the voltage at the first terminal of the voltage converter 11 gradually decreases, and the operating states of these circuit structures cannot be maintained when it decreases to a certain extent.
As an example,
Thus, for the curve S2, after the second voltage decreases to the reference voltage REF, it looks gentler than the curve S1, and the second voltage drops to the critical value Von at the third time instant t3 after the second time instant t2. By comparison, it can be seen that the driving circuit provided by the exemplary embodiment can give more time “t3-t2” than the contrastive example for the voltage converter 11 to maintain the operating states of other circuit structures, which helps to enable these circuit structures to perform operations that need to be completed upon powering off the display device. For example, during the process in which the gate driver and the source driver cooperate to avoid the visible shadow effect upon powering off the display device, the time period “t3-t2” can facilitate the gate driver to output a gate turn-on voltage in the allowable range, which is advantageous for the liquid crystal capacitor to be discharged, and thus helps to eliminate or alleviate the above problem regarding the visible shadow effect upon powering off the display device.
It can be appreciated that, with the voltage comparison sub-circuit and the switch sub-circuit in the embodiment of the disclosure, the connection between the second terminal of the voltage converter and the source driver can be disconnected when the first voltage drops below the reference voltage, so as to interrupt the power consumption caused by the second voltage, slow down the decreasing speed of the first voltage VDDIN, and prolong the time for relevant components to perform operations such as screen cleaning, which thus helps to avoid display abnormalities upon powering off caused by a too fast power-down, thereby improving the performance of the display device.
The critical value Von mentioned above is mainly used to explain the technical effects of exemplary embodiments, and may not be a parameter actually set for the driving circuit. The above-described reference voltage REF may be, for example, a voltage signal generated inside or outside the driving circuit, whose magnitude may be set as needed. For example, it can be inferred from the description above that the reference voltage REF should be smaller than the above maximum value Vmax and larger than the above critical value Von. On this basis, the closer the reference voltage REF is to the maximum value Vmax, the longer the time period “t3-t2” shown in
In another exemplary embodiment, as shown in
By comparing
It can be understood that, for an existing driving circuit of a display device, the switch sub-circuit and the voltage comparison sub-circuit may be added by referring to the above exemplary embodiments. For example, exemplary embodiments of the disclosure may be implemented by adding respective elements and lines on the circuit board of the driving circuit. As an example of another implementation, the switch sub-circuit and the voltage comparison sub-circuit may also be disposed in existing components of the driving circuit.
As an example,
As an example of an implementation of the voltage conversion circuit 11′, as shown in
Further, as shown in
As an example of another implementation of the voltage conversion circuit 11′, the voltage conversion circuit 11′ includes a processor and a memory (not shown). The processor is connected to the first terminal and the second terminal of the voltage conversion circuit 11′ respectively via an interface circuit. A first instruction, a second instruction and a third instruction are stored in the memory. The processor can convert the first voltage from the first terminal of the voltage conversion circuit 11′ into the second voltage outputted at the second terminal of the voltage conversion circuit 11′ by executing the first instruction, trigger execution of the third instruction when the voltage at the first terminal of the voltage conversion circuit 11′ is less than the reference voltage by executing the second instruction, and stop the output of the voltage at the second terminal of the voltage conversion circuit 11′ by executing the third instruction.
In addition to the above hardware implementation and software implementation, the functions of the switch sub-circuit and the voltage comparison sub-circuit described above may also be implemented by a combination of software and hardware. For example, the processor executes a fourth instruction in the memory so that a control signal is outputted to the gate of the above first transistor M1 when the voltage at the first terminal of the voltage conversion circuit 11′ is less than the reference voltage, so as to enable the first transistor M1 to disconnect the voltage transmission path for transmitting the second voltage. Of course, the possible implementations in practice may not be limited to the above examples.
Referring to
The display device in exemplary embodiments of the present disclosure may be any product or component having a display function such as a display panel, a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator, and the like. Moreover, although the exemplary embodiment is described above taking liquid crystal displays as an example, in practice, exemplary embodiments of the disclosure may also be applied to other display devices such as an organic light emitting diode (OLED) display device, a quantum dot light emitting diode (QLED) display device, and the like, which can also prolong the time for relevant components to perform operations such as cleaning screen upon powering off the display device, and help to avoid or mitigate display abnormalities upon caused by a too fast power-down, improving the performance of the display device.
Furthermore, in any of the above exemplary embodiments, the reference voltage may be generated by an internal circuit of the driving circuit. For example, in the exemplary embodiment shown in
It can be understood that the reference voltage obtained by outputting a constant voltage may not decrease as the voltage at the first terminal of the voltage converter or the voltage conversion circuit decreases, thus the voltage comparison sub-circuit may be provided with a reference voltage with a stable amplitude when the display device is powered off, which will not cause an abnormal operation of the voltage comparison sub-circuit for being not affected by the variation in the first voltage at the first terminal of the voltage converter or voltage conversion circuit. Compared to the way in which it is required to individually provide a reference voltage externally, this embodiment is more advantageous for reducing the number of external ports of the driving circuit and simplifying the overall structure.
Moreover, in some exemplary embodiments, the voltage converter or voltage conversion circuit itself may provide the timing controller with a voltage signal having a constant amplitude of, for example, 1.2V. For example, the third terminal of the voltage converter is further connected to the timing controller. Owing to this, the voltage signal can be directly used as a reference voltage to be connected to the voltage comparison sub-circuit, which further simplifies the structure of the driving circuit.
Based on the same inventive concept, a further exemplary embodiment of the present disclosure provides a control method for a display device. The display device comprises a voltage converter and a source driver. The voltage converter has a first terminal for receiving a first voltage from a power supply, and a second terminal for outputting a second voltage to the source driver. The control method comprises: disconnecting a voltage transmission path between the second terminal of the voltage converter and the source driver in response to the first voltage at the first terminal of the voltage converter being less than a reference voltage. It can be understood that the implementations of the switch sub-circuit and the voltage comparison sub-circuit as described above can be regarded as examples of implementation of the above control method, and therefore details of the control method will not be described again. In conclusion, with exemplary embodiments, the output of the second voltage AVDD can be cut off when the first voltage drops below the reference voltage, so as to interrupt the power consumption caused by the second voltage, slow down the falling speed of the first voltage VDDIN, and prolong the time for relevant components to perform operations such as screen cleaning when powering off the display device, which thus helps to avoid or relieve display abnormalities caused by a too fast power-down, thereby improving the performance of the display device.
What have been stated above are merely exemplary embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc., which are made within the spirit and principle of the present disclosure, should be encompassed in the scope of the application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201710706159.9 | Aug 2017 | CN | national |
The present application is the U.S. national phase entry of PCT/CN2018/087457, with an international filling date of May 18, 2018, which claims the benefit of Chinese Patent Application No. 201710706159.9, filed on Aug. 17, 2017, the entire disclosure of which is incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2018/087457 | 5/18/2018 | WO | 00 |
