CN218273953U - Display device and protection circuit thereof - Google Patents
Display device and protection circuit thereof Download PDFInfo
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- CN218273953U CN218273953U CN202222464249.0U CN202222464249U CN218273953U CN 218273953 U CN218273953 U CN 218273953U CN 202222464249 U CN202222464249 U CN 202222464249U CN 218273953 U CN218273953 U CN 218273953U
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Abstract
The utility model discloses a display device and protection circuit thereof, display device is including a plurality of pixel units that become array arrangement, protection circuit includes: the current sources correspond to one row of the pixel units, the input end of each current source is connected to a power supply, and the output end of each current source is connected to the input end of each pixel unit corresponding to one row, wherein the output end of each current source is used for outputting corresponding preset current so that the current flowing through the pixel units is always smaller than the threshold current of the pixel units, and the phenomenon that the pixel circuits and/or the organic light emitting diodes are burnt out due to overlarge current flowing through the pixel units is avoided.
Description
Technical Field
The utility model relates to a show technical field, in particular to display device and protection circuit thereof.
Background
The OLED display panel can adjust the display brightness by controlling the light-emitting current of the organic light-emitting diode OLED, and the threshold current of the organic light-emitting diode OLED can be estimated according to the light-emitting EL performance of the organic light-emitting diode OLED after evaporation when the OLED display panel is manufactured.
When the pixel circuit of the OLED display panel is produced, in order to prevent the pixel circuit and the organic light emitting diode OLED from being burnt by a current value of a current flowing through the organic light emitting diode OLED that is larger than a threshold current thereof, a burn-in prevention design is performed. One design in the prior art is to add an additional transistor inside a pixel circuit, and if unexpected conditions such as abnormal operation of a matching circuit, abnormal temperature or abnormal electrostatic protection (ESD) occur, abnormal current is generated, and at this time, an on-resistance Ron is generated by the additional transistor, so that the equivalent impedance is increased, and the purpose of current limiting and burnout prevention is achieved.
The other design is that under the condition that a transistor is not additionally added, an algorithm is partially used, when the luminance of the organic light-emitting diode OLED reaches the maximum luminance, the current flowing through the organic light-emitting diode OLED is detected, if the current value of the current is too large, the voltage value of the data voltage VDATA is adjusted by the algorithm to reduce the total current, and the purpose of preventing burning is achieved.
SUMMERY OF THE UTILITY MODEL
In view of the foregoing problems, an object of the present invention is to provide a display device and a protection circuit thereof, so that when any pixel unit is short-circuited, the current flowing through the organic light emitting diode OLED can be adjusted in real time, thereby avoiding the pixel circuit and/or the organic light emitting diode OLED from being burnt.
According to an aspect of the present invention, there is provided a protection circuit for a display device, the display device includes a plurality of pixel units arranged in an array, the protection circuit includes a plurality of current sources, each of which corresponds to a row the pixel units, each of which has an input connected to a power supply and an output connected to each of the pixel units, wherein each of the outputs of the current sources is used to output a corresponding predetermined current, so that the current flowing through the pixel units is always smaller than a threshold current thereof.
Optionally, each of the current sources is configured to provide a driving current for the pixel units in a corresponding row when the pixel units in the corresponding row operate normally.
Optionally, each current source is further configured to reduce the voltage at the output end of the current source when any pixel unit in a corresponding row is short-circuited, so as to reduce the short-circuit current, so that the current flowing through the pixel unit is smaller than the threshold current thereof.
Optionally, the protection circuit further comprises: and the current control module is respectively connected with the plurality of current sources and used for controlling the plurality of current sources to output corresponding preset currents.
Optionally, the current source is a current mirror circuit, and includes a first transistor and a second transistor, an intermediate node at which a control terminal of the first transistor is connected to a control terminal of the second transistor is connected to a second conducting terminal of the first transistor for receiving a reference current, a first conducting terminal of the first transistor is connected to the first conducting terminal of the second transistor for receiving the power supply voltage, and a second conducting terminal of the second transistor is connected to an input terminal of each pixel unit in a corresponding row for outputting the predetermined current.
Optionally, the current control module is configured to control a ratio of the current mirror circuit according to a predetermined current corresponding to the current mirror circuit and the reference current, so as to control the current mirror circuit to output the corresponding predetermined current.
Optionally, each of the pixel units includes a pixel circuit, and an input terminal is connected to an output terminal of the current source; the anode of the organic light emitting diode is connected with the output end of the pixel circuit, and the cathode of the organic light emitting diode is grounded; and the input end of the discharge switch is connected with the output end of the pixel circuit, and the output end of the discharge switch is grounded.
Optionally, the threshold current of the pixel unit is the maximum forward current of the organic light emitting diode therein.
Optionally, a register is disposed inside the current control module to pre-store the predetermined current corresponding to the plurality of current sources.
According to another aspect of the present invention, there is provided a display device including the protection circuit as described above.
According to the embodiment of the utility model provides a display device and protection circuit thereof, through setting up the current source that corresponds with every line of pixel unit, can be when the short circuit takes place for arbitrary pixel unit in arbitrary line of pixel unit, reduce the voltage of the output of the current source that this pixel unit corresponds, thereby press down the short-circuit current of this pixel unit, so that the electric current that flows through this pixel unit is not more than the organic light emitting diode OLED's in this pixel unit threshold current, thereby prevent that pixel unit from producing unusual heavy current, reach the purpose that prevents pixel circuit and/or organic light emitting diode OLED from being burnt out, and is easy to operate, and wide in application scope.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram illustrating a protection circuit of a display device according to an embodiment of the present invention;
fig. 2 shows a connection schematic diagram of a current source and its corresponding pixel unit according to an embodiment of the present invention.
Detailed Description
Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various figures, identical elements or modules are denoted by the same or similar reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale.
It should be understood that in the following description, "circuitry" may comprise singly or in combination hardware circuitry, programmable circuitry, state machine circuitry, and/or elements capable of storing instructions executed by programmable circuitry. When an element or circuit is referred to as being "connected to" another element or circuit is referred to as being "connected between" two nodes, it may be directly coupled or connected to the other element or intervening elements may be present, and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, it is intended that the two be absent intermediate elements.
Also, certain terms are used throughout the description and claims to refer to particular components. As one of ordinary skill in the art will appreciate, manufacturers may refer to a component by different names. This patent specification and claims do not intend to distinguish between components that differ in name but not function.
Moreover, it is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
Fig. 1 shows a schematic structural diagram of a protection circuit of a display device according to an embodiment of the present invention.
As shown in fig. 1, the display device includes a plurality of pixel units 20 arranged in an array, and the protection circuit includes: the pixel driving circuit comprises a plurality of current sources 10 and a current control module 30, wherein each current source 10 corresponds to a row of pixel units 20, the input end of each current source 10 is connected with a power voltage VDD, the output end of each current source 10 is connected with the input end of each pixel unit 20 corresponding to a row, and the current control module 30 is respectively connected to the plurality of current sources 10.
The current control module 30 is internally provided with a register, which stores a predetermined current corresponding to each row of pixel units 20 in advance, and is used for controlling the output end of the current source 10 corresponding to each row of pixel units 20 to output the corresponding predetermined current. The predetermined current of each current source 10 stored in the current control module 30 may be set according to the required maximum current of the pixel unit 20 corresponding to one row, may be equal to the required maximum current of the pixel unit 20 corresponding to one row or slightly larger than the required maximum current of the pixel unit 20 corresponding to one row, and may be specifically adjusted according to an actual situation, for example, if the required maximum current of the pixel unit 20 corresponding to one row is 10mA, the predetermined current may be set to 10.5mA or 11mA.
Under normal conditions, a corresponding predetermined current outputted by the current source 10 is distributed to each pixel unit 20 of a corresponding row to provide a driving current for each pixel unit 20 of a corresponding row to make it operate normally, and the voltage VDD _ INT at the output terminal of the current source 10 is equal to the power voltage VDD.
When any pixel cell 20 is shorted, the predetermined current output by its corresponding current source 10 ensures that the current flowing through that pixel cell 20 does not exceed its threshold current.
Specifically, for example, when the first pixel unit 20 in a certain row of pixel units 20 is short-circuited, it will cause a short-circuit current with a relatively large current value, and at this time, the first pixel unit 20 in the row has a small equivalent impedance, so that the short-circuit current of the first pixel unit 20 in the row = the voltage/equivalent impedance at the output end of the current source, and since the predetermined current output by the current source 10 is mostly concentrated in the first pixel unit 20 in the row, the current input to the other pixel units 20 in the row is small, which causes the voltage VDD _ INT at the output end of the current source 10 to drop rapidly, and the voltage VDD _ INT drops inevitably so that the short-circuit current also drops, thereby lowering the current flowing through the first pixel unit 20 in the row and making it not exceed the threshold current of the first pixel unit 20 in the row.
Fig. 2 shows a connection schematic diagram of a current source and its corresponding pixel unit according to an embodiment of the present invention.
The current source 10 is, for example, a current mirror (current mirror) circuit, the current mirror circuit includes a transistor M1 and a transistor M2, and the transistor M1 and the transistor M2 may be both PMOS transistors or both NMOS transistors. In the present embodiment, the transistor M1 and the transistor M2 are both PMOS as an example, but the structure of the current mirror circuit is not limited in the embodiments of the present invention, and can be selected according to actual needs.
The first conducting terminal of the transistor M1 and the first conducting terminal of the transistor M2 are connected as a power input terminal of the current mirror circuit for receiving a power supply voltage VDD, the intermediate node where the control terminal of the transistor M1 and the control terminal of the transistor M2 are connected as a current input terminal of the current mirror circuit with the second conducting terminal of the transistor M1 for receiving a reference current Iref, and the second conducting terminal of the transistor M2 is used as an output terminal of the current mirror circuit for outputting a predetermined current. The first pass terminals of the transistors M1 and M2 are source terminals, and the second pass terminals are drain terminals, or vice versa.
The proportion of the current mirror circuit is 1: n,1 is a current value of the reference current Iref, and N is a ratio of the predetermined current and the reference current Iref. The current control module 30 controls the ratio of the current mirror circuit according to the predetermined current corresponding to the current source 10 and the reference current Iref, so as to control the current source 10 to output the corresponding predetermined current.
The pixel unit 20 includes a pixel circuit 21, an organic light emitting diode OLED, and a discharge switch S, wherein an input terminal of the pixel circuit 21 connected to the second conducting terminal of the transistor M2 serves as a power supply terminal of the pixel unit 20, another input terminal of the pixel circuit 21 is configured to receive a data voltage VDATA, an output terminal of the pixel circuit 21 is connected to an anode of the organic light emitting diode OLED, a cathode of the organic light emitting diode OLED is connected to a power supply VSS, an output terminal of the pixel circuit 21 is further connected to one terminal of the discharge switch S, and another terminal of the discharge switch S is connected to the power supply VSS2.
Under normal conditions, the current source 10 distributes the output corresponding predetermined current to each pixel unit 20 in a corresponding row to drive the components in each pixel unit 20 to work normally, and the voltage VDD _ INT at the output end of the current source 10 corresponding to each row of pixel units 20 is equal to the power supply voltage VDD.
The discharge switch S in the pixel unit 20 may be short-circuited when it is turned on at an inappropriate time due to ESD or other factors, or when the temperature of the organic light emitting diode OLED is abnormal, or when the operation of the pixel circuit 21 or the organic light emitting diode OLED is abnormal.
When any pixel unit 20 is short-circuited due to any of the above reasons, it will cause a short-circuit current with a relatively large current value, and at this time, most of the corresponding predetermined current output by the corresponding current source 10 is distributed to the pixel unit 20, and the current distributed to the other pixel units 20 in the row of the pixel unit 20 is very small, and cannot satisfy the driving current required by the other pixel units 20 in the row to drive the organic light emitting diodes OLED therein, so that the voltage value of the voltage VDD _ INT at the output terminal of the current source 10 is reduced, thereby reducing the short-circuit current of the pixel unit 20, ensuring that the current flowing through the pixel unit 20 does not exceed the threshold current of the pixel unit 20, thereby preventing the pixel unit 20 from generating an abnormal large current, and achieving the purpose of preventing the pixel circuit 21 and/or the organic light emitting diodes OLED from being burned.
Further, the threshold current of the pixel unit 20 is the maximum forward current of the organic light emitting diode OLED therein.
Further, the voltage value of the voltage VDD _ INT at the output terminal of the current source 10 is related to the resistance value of the equivalent impedance of the pixel unit 20, the smaller the resistance value of the equivalent impedance of the pixel unit 20 is, the lower the voltage value of the voltage VDD _ INT at the output terminal of the current source 10 is, and when the resistance value of the equivalent impedance of the pixel unit 20 is sufficiently small, the voltage VDD _ INT at the output terminal of the current source 10 is close to zero.
According to the embodiment of the utility model provides a protection circuit of display device, through setting up the current source 10 that corresponds with every row of pixel 20, can be when arbitrary pixel 20 takes place the short circuit, reduce the voltage VDD _ INT of the current source 10 output that this pixel 20 corresponds rapidly, thereby reduce the short-circuit current of this pixel 20, so that the electric current that flows through this pixel 20 is not more than its threshold current, thereby prevent that pixel 20 from producing unusual heavy current, reach the purpose that prevents pixel 21 and/or organic light emitting diode OLED from being burnt, and is easy to operate, and wide application scope.
The embodiment of the utility model provides a still provide a display device, include as above-mentioned protection circuit.
In accordance with the present invention, as set forth above, these embodiments do not set forth all of the details nor limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and its various embodiments with various modifications as are suited to the particular use contemplated. The scope of the present invention should be determined by the appended claims and their equivalents.
Claims (10)
1. A protection circuit of a display device including a plurality of pixel units arranged in an array, the protection circuit comprising:
a plurality of current sources, each of the current sources corresponding to a row of the pixel units, each of the current sources having an input terminal connected to a power supply and an output terminal connected to an input terminal of each of the pixel units corresponding to a row,
the output end of each current source is used for outputting corresponding preset current so that the current flowing through the pixel unit is always smaller than the threshold current of the pixel unit.
2. The protection circuit of claim 1, wherein each of the current sources is configured to provide a drive current to the pixel cells of a corresponding row when the pixel cells of the corresponding row are operating normally.
3. The protection circuit of claim 2, wherein each current source is further configured to reduce the voltage at the output terminal of the current source to reduce the short-circuit current when any one of the pixel cells in a corresponding row is short-circuited, so that the current flowing through the pixel cell is less than the threshold current of the pixel cell.
4. The protection circuit of claim 3, wherein the protection circuit further comprises:
and the current control module is respectively connected with the plurality of current sources and used for controlling the plurality of current sources to output corresponding preset currents.
5. The protection circuit of claim 4, wherein the current source is a current mirror circuit comprising:
the pixel circuit comprises a first transistor and a second transistor, wherein an intermediate node, which is connected with a control end of the first transistor and a control end of the second transistor, is connected with a second conduction end of the first transistor for receiving a reference current, a first conduction end of the first transistor is connected with a first conduction end of the second transistor for receiving a power supply voltage, and a second conduction end of the second transistor is connected with an input end of each pixel unit in a corresponding row for outputting the preset current.
6. A protection circuit as claimed in claim 5, wherein the current control module is arranged to control the proportion of the current mirror circuit in dependence on the corresponding predetermined current of the current mirror circuit and the reference current to control the current mirror circuit to output the corresponding predetermined current.
7. The protection circuit according to claim 1, wherein each of the pixel units includes;
the input end of the pixel circuit is connected with the output end of the current source;
the anode of the organic light emitting diode is connected with the output end of the pixel circuit, and the cathode of the organic light emitting diode is grounded;
and the input end of the discharge switch is connected with the output end of the pixel circuit, and the output end of the discharge switch is grounded.
8. The protection circuit of claim 7, wherein the threshold current of the pixel cell is the maximum forward current of its internal organic light emitting diode.
9. The protection circuit according to claim 4, wherein the current control module is internally provided with a register to pre-store the predetermined currents corresponding to the plurality of current sources.
10. A display device comprising the protection circuit according to any one of claims 1 to 9.
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| CN202222464249.0U CN218273953U (en) | 2022-09-16 | 2022-09-16 | Display device and protection circuit thereof |
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| CN202222464249.0U CN218273953U (en) | 2022-09-16 | 2022-09-16 | Display device and protection circuit thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117095635A (en) * | 2023-09-18 | 2023-11-21 | 欣瑞华微电子(上海)有限公司 | Display device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117095635A (en) * | 2023-09-18 | 2023-11-21 | 欣瑞华微电子(上海)有限公司 | Display device |
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