CN112992051A - Constant current source correction device and method of LED display - Google Patents
Constant current source correction device and method of LED display Download PDFInfo
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- CN112992051A CN112992051A CN202110210377.XA CN202110210377A CN112992051A CN 112992051 A CN112992051 A CN 112992051A CN 202110210377 A CN202110210377 A CN 202110210377A CN 112992051 A CN112992051 A CN 112992051A
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
- Led Devices (AREA)
Abstract
The application provides a constant current source correction device of an LED display and a method thereof, comprising the following steps: the calibration circuit comprises a plurality of driving chips and calibration resistors, wherein one end of each calibration resistor is connected with a second power supply end, and the other end of each calibration resistor is connected with the calibration pin of each driving chip. Each of the driving chips includes: the constant current sources are provided with trimming circuits, one end of each constant current source is connected with a first power supply end, and the other end of each constant current source is connected with a row of LED lamp beads and is connected with a correction pin through an output switching circuit; and the first input end of the comparator is connected with the correction voltage, the second input end of the comparator is connected with the correction pin, and the correction pins of each of the plurality of driving chips are electrically connected. The precision of each constant current source can be improved.
Description
Technical Field
The invention relates to the technical field of display, in particular to a constant current source correction device and method of an LED display.
Background
In the field of LED display screens, according to the display characteristics of LED lamp beads, a constant current source circuit is required to provide accurate current to supply power to the LED lamp beads, so that the uniformity of colors can be ensured. The constant current source used for LED display has two forms, one is a common anode current-absorbing constant current source, and the other is a common cathode current-discharging constant current source. The common anode is formed by connecting the anode of the LED lamp bead with the scanning tube, and the constant current source is connected with the cathode of the lamp bead; the common cathode is a cathode of the lamp bead connected with the sweeping tube, and the constant current source is connected with an anode of the lamp bead. Due to the inconsistency of the integrated circuit process, the produced constant current source circuit always has certain deviation, and the current constant current source chip can achieve the error of 1% in the chip and 2% between the chips under the advanced condition. Such a deviation due to the production process is inevitable if no special treatment is performed.
Disclosure of Invention
The invention aims to provide a constant current source correction device and method of an LED display, which can improve the precision of a constant current source in each driving chip.
In one embodiment of the present application, a constant current source correction device for an LED display is disclosed, which includes:
a plurality of driver chips, each of the driver chips comprising:
the constant current sources are provided with trimming circuits, one end of each constant current source is connected with a first power supply end, and the other end of each constant current source is connected with a row of LED lamp beads and is connected with a correction pin through an output switching circuit;
the first input end of the comparator is connected with a correction voltage, the second input end of the comparator is connected with the correction pin, and the correction pin of each of the plurality of driving chips is electrically connected;
and one end of the correction resistor is connected with a second power supply end, and the other end of the correction resistor is connected with the correction pin of each driving chip.
Preferably, the first power end is a voltage source, the second power end is a ground end, the other end of each of the plurality of constant current sources is connected with the anode of each of the LED lamp beads in one row, and the cathode of each of the LED lamp beads in one row is connected with the control pin through a switch.
Preferably, the first power end is a ground end, the second power end is a voltage source, the other end of each of the plurality of constant current sources is connected with the cathode of each of the LED lamp beads in one row, and the anode of each of the LED lamp beads in one row is connected with the control pin through a switch.
Preferably, the output switching circuit is a control switch.
The correction voltage is 2V-3V.
Preferably, the first input terminal is a non-inverting input terminal, and the second input terminal is an inverting input terminal
In an embodiment of the present application, a method for calibrating a constant current source of an LED display is disclosed, which employs the apparatus described above, and includes:
controlling an output switching circuit of a constant current source of a first driving chip to be switched on, and controlling output switching circuits of other constant current sources of the first driving chip and constant current sources of other driving chips to be switched off, wherein the constant current source is electrically connected with a correction pin of the first driving chip, the current value of the constant current source is adjusted, and the current value of the constant current source when a comparator of the first driving chip changes is used as a correction value; and
and controlling the conduction of an output switching circuit of one constant current source of other driving chips, controlling the disconnection of the output switching circuits of the other constant current sources of the driving chip and the output switching circuits of the constant current sources of the other driving chips, electrically connecting the constant current source with the correction pin of the first driving chip, adjusting the current value of the constant current source, and taking the current value of the constant current source as the correction value when the comparator of the first driving chip is changed.
Preferably, the first power end is a voltage source, the second power end is a ground end, the other end of each of the plurality of constant current sources is connected with the anode of each of the LED lamp beads in one row, and the cathode of each of the LED lamp beads in one row is connected with the control pin through a switch.
Preferably, the first power end is a ground end, the second power end is a voltage source, the other end of each of the plurality of constant current sources is connected with the cathode of each of the LED lamp beads in one row, and the anode of each of the LED lamp beads in one row is connected with the control pin through a switch.
Preferably, when the output switching circuit of one constant current source of the first driving chip is controlled to be switched on, the LED lamp bead connected with the first driving chip is connected with the voltage source through the control pin.
Compared with the prior art, the constant current source correction device and the method of the LED display have the following beneficial effects:
in the application, the precision of the automatically corrected constant current source can reach the magnitude of one thousandth.
Drawings
Fig. 1 is a schematic diagram of a constant current source correction device of an LED display according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a normal operation mode according to an embodiment of the present invention.
Fig. 3 is a schematic diagram illustrating a calibration process of the chip 1 in the calibration mode according to an embodiment of the invention.
Fig. 4 is a schematic diagram illustrating a calibration process of the chip 2 in the calibration mode according to an embodiment of the invention.
Fig. 5 is a schematic diagram of a constant current source calibration method of an LED display according to an embodiment of the invention.
Detailed Description
In the following description, numerous technical details are set forth in order to provide a better understanding of the present application. However, it will be understood by those skilled in the art that the technical solutions claimed in the present application can be implemented without these technical details and with various changes and modifications based on the following embodiments.
In an embodiment of the present application, a constant current source correction device for an LED display is disclosed, and fig. 1 is a schematic diagram of the constant current source correction device. The correction device includes: a plurality of driving chips 10, a correction resistor 20, and a Light Emitting Diode (LED) lamp bead 30. Only driver chips 1 and 2 are shown in fig. 1, it being understood that the apparatus may also comprise more driver chips, e.g. 3, 5, etc. The driving chip 10 is used for driving the LED lamp beads 30 to work.
Each driver chip 10 includes a plurality of constant current sources 11 having trimming circuits, a comparator 12, an output switching circuit 13, and a correction pin 14. One end of each of the constant current sources 11 is connected to a first power supply terminal, and the other end is connected to a row of LED lamp beads 30 and connected to the calibration pins 14 through the output switching circuit 13. The first input end of the comparator is connected withIs connected with a correction voltage VTRIM_XAnd a second input terminal is connected to a calibration pin 14. The calibration pins 14 of each of the several driver chips are electrically connected. Correcting resistance (R)TRIM_X) One end of the second power terminal 20 is connected to the second power terminal, and the other end is connected to the calibration pin 14 of each driver chip 10.
The light-emitting LED lamp bead shown in fig. 1 is a common-cathode light-emitting LED lamp bead, in this embodiment, the first power end is a voltage source VDD _ X, and the second power end is a ground end. The other end of each of the plurality of constant current sources 11 is connected to the anode of each of the LED beads in one row of LED beads 30, and the cathode of each of the LED beads in one row of LED beads 30 is connected to the control pin 40 through a switch for connecting the row sweeping tube. It should be understood that in other embodiments of the present invention, the light-emitting LED lamp bead may also be a common-anode light-emitting LED lamp bead, in this embodiment, the first power end is a ground end, and the second power end is a voltage source. The other end of each of the constant current sources is connected with the cathode of each LED lamp bead in a row of LED lamp beads, and the anode of each LED lamp bead in a row of LED lamp beads is connected with the control pin through the switch and used for being connected with the row sweeping tube. It should be noted that in the process of correcting the constant current source, the line scanning end of the display screen is closed, and the current is ensured not to flow through the LED lamp beads, so that the correction result is influenced.
In the present invention, the constant current source 11 has a trimming circuit (not shown) which can adjust the current value output by the constant current source. The trimming circuit can be implemented in various ways, for example, by superimposing current mirrors of different sizes. The output switching circuit can select one of the multiple constant current sources on one driving chip to be switched to a fixed TRIM _ X output, or can not select the constant current source to be switched to the output. In one embodiment, the output switching circuit is a control switch for controlling the constant current source to be connected to the input terminal of the comparator. The TRIM _ X with the switching output of the constant current source is externally connected with a fixed resistor to the ground (common cathode constant current source) or a power supply (common anode constant current source), and the comparator 12 is used for comparing the voltage on the TRIM _ X with a correction voltage or reference voltage (for example, V) in the chipTRIM_X) And comparing and outputting a comparison result inside the chip. In one embodiment, the correction voltage is2V to 3V, for example, 2.5V.
Usually, a plurality of driving chips are disposed on a display panel, and in order to ensure the consistency of the constant current sources among the plurality of chips, the TRIM pins TRIM _ X of the plurality of chips are electrically connected together, and the comparison result of one of the chips is used as a fine tuning reference.
FIG. 2 is a diagram illustrating a normal operation mode according to an embodiment of the present invention. When the LED lamp works normally, each constant current source outputs current to the corresponding LED lamp bead.
Fig. 3 is a schematic diagram illustrating a calibration process of the chip 1 in the calibration mode according to an embodiment of the invention. In the correction mode: firstly, one path of constant current source of the chip 1 is switched to the correction TRIM _ X, the current magnitude of the constant current source is finely adjusted until the output result of the comparator changes, the value of the comparator when the comparator changes is recorded according to the result of the comparator, and the value is stored as the fine adjustment parameter of the constant current source. And by analogy, calibrating each constant current source on the chip in sequence. When a certain path of constant current source is corrected, the cathode of the LED lamp bead is connected with a voltage source, and the switching circuits of the other paths of constant current sources of the chip 1 are all disconnected.
Fig. 4 is a schematic diagram illustrating a calibration process of the chip 2 in the calibration mode according to an embodiment of the invention. After all the constant current sources of the chip 1 are calibrated, the constant current source of the chip 2 is switched to the calibration pin TRIM _ X of the chip 1, and the constant current source is output to the calibration resistor R connected with the TRIM _ X of the chip 1TRIM_XIn the above, the constant current source on chip 2 is calibrated in turn, still using the comparator of chip 1 as a feedback result. The constant current sources of all chips on the board are calibrated in turn with the comparator of chip 1. Although there is a production process inconsistency between chips, since the comparators of chip 1 are used for calibration, all the constant current sources on the display panel are calibrated to a consistent result after calibration.
The correction method of the invention can be popularized among different display unit boards on the same display screen, namely, the current of the constant current sources on different display boards is sequentially output to the calibration resistor of a certain chip (such as the display board 1 and the chip 1) of a certain display board, and the constant current sources of all chips on all display unit boards in the display screen are sequentially calibrated by using the comparator in the same chip, so as to achieve the purpose of uniformly calibrating the constant current sources of the whole display screen.
In an embodiment of the present application, a method for calibrating a constant current source of an LED display is disclosed, in which the foregoing apparatus is used, and a flowchart thereof is shown in fig. 5, and the method includes the following steps:
controlling the conduction of an output switching circuit of a constant current source of the first driving chip, controlling the disconnection of output switching circuits of other constant current sources of the first driving chip and constant current sources of other driving chips, electrically connecting the constant current source with a correction pin of the first driving chip, adjusting the current value of the constant current source, and taking the current value of the constant current source as a correction value when a comparator of the first driving chip changes; and
and controlling the conduction of an output switching circuit of one constant current source of other driving chips, controlling the disconnection of the output switching circuits of the other constant current sources of the driving chip and the output switching circuits of the constant current sources of the other driving chips, electrically connecting the constant current source with a correction pin of the first driving chip, adjusting the current value of the constant current source, and taking the current value of the constant current source as a correction value when a comparator of the first driving chip is changed.
In one embodiment, the first power supply end is a voltage source, the second power supply end is a ground end, the other end of each of the plurality of constant current sources is connected with the anode of each of the LED lamp beads in one row, and the cathode of each of the LED lamp beads in one row is connected with the control pin through the switch.
In one embodiment, the first power supply end is a ground end, the second power supply end is a voltage source, the other end of each of the plurality of constant current sources is connected with the cathode of each of the LED lamp beads in one row, and the anode of each of the LED lamp beads in one row is connected with the control pin through the switch.
In one embodiment, when the output switching circuit of one constant current source of the first driving chip is controlled to be switched on, the LED lamp bead connected with the first driving chip is connected with the voltage source through the control pin.
It is noted that, in the present patent application, relational terms such as first and second, and the like are 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, the use of the verb "comprise a" to define an element does not exclude the presence of another, same element in a process, method, article, or apparatus that comprises the element.
In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.
Claims (10)
1. A constant current source correction device of an LED display is characterized by comprising:
a plurality of driver chips, each of the driver chips comprising:
the constant current sources are provided with trimming circuits, one end of each constant current source is connected with a first power supply end, and the other end of each constant current source is connected with a row of LED lamp beads and is connected with a correction pin through an output switching circuit;
the first input end of the comparator is connected with a correction voltage, the second input end of the comparator is connected with the correction pin, and the correction pin of each of the plurality of driving chips is electrically connected; and one end of the correction resistor is connected with a second power supply end, and the other end of the correction resistor is connected with the correction pin of each driving chip.
2. The device of claim 1, wherein the first power source terminal is a voltage source, the second power source terminal is a ground terminal, the other end of each of the plurality of constant current sources is connected to the anode of each of the LED beads in a column of LED beads, and the cathode of each of the LED beads in a row of LED beads is connected to the control pin through a switch.
3. The device of claim 1, wherein the first power source terminal is a ground terminal, the second power source terminal is a voltage source, the other end of each of the plurality of constant current sources is connected to the cathode of each of the LED beads in a column of LED beads, and the anode of each of the LED beads in a row of LED beads is connected to the control pin through a switch.
4. The LED display constant current source correction device according to claim 1, wherein the output switching circuit is a control switch.
5. The LED display constant current source correction device according to claim 1, wherein the correction voltage is 2V to 3V.
6. The apparatus of claim 1, wherein the first input terminal is a non-inverting input terminal and the second input terminal is an inverting input terminal.
7. A method for constant current source calibration of an LED display, using the apparatus of claim 1, the method comprising:
controlling an output switching circuit of a constant current source of a first driving chip to be switched on, and controlling output switching circuits of other constant current sources of the first driving chip and constant current sources of other driving chips to be switched off, wherein the constant current source is electrically connected with a correction pin of the first driving chip, the current value of the constant current source is adjusted, and the current value of the constant current source when a comparator of the first driving chip changes is used as a correction value; and
and controlling the conduction of an output switching circuit of one constant current source of other driving chips, controlling the disconnection of the output switching circuits of the other constant current sources of the driving chip and the output switching circuits of the constant current sources of the other driving chips, electrically connecting the constant current source with the correction pin of the first driving chip, adjusting the current value of the constant current source, and taking the current value of the constant current source as the correction value when the comparator of the first driving chip is changed.
8. The method for calibrating a constant current source of an LED display of claim 7, wherein said first power source terminal is a voltage source, said second power source terminal is a ground terminal, another terminal of each of said plurality of constant current sources is connected to an anode of each LED bead in a column of LED beads, and a cathode of each LED bead in a row of LED beads is connected to a control pin through a switch.
9. The method for calibrating a constant current source of an LED display of claim 7, wherein said first power source terminal is a ground terminal, said second power source terminal is a voltage source, another terminal of each of said plurality of constant current sources is connected to a cathode of each of a column of LED beads, and an anode of each of a row of LED beads is connected to a control pin through a switch.
10. The method for calibrating a constant current source of an LED display according to claim 8 or 9, wherein when an output switching circuit for controlling a constant current source of the first driver chip is turned on, the LED lamp bead connected to the first driver chip is connected to a voltage source through the control pin.
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| CN202110210377.XA CN112992051B (en) | 2021-02-25 | 2021-02-25 | Constant current source correction device and method of LED display |
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| CN112992051B (en) | 2022-06-03 |
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