CN113490307B - Control circuit of LED display screen pre-charging circuit and pre-charging circuit - Google Patents
Control circuit of LED display screen pre-charging circuit and pre-charging circuit Download PDFInfo
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- CN113490307B CN113490307B CN202111039706.5A CN202111039706A CN113490307B CN 113490307 B CN113490307 B CN 113490307B CN 202111039706 A CN202111039706 A CN 202111039706A CN 113490307 B CN113490307 B CN 113490307B
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
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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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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/345—Current stabilisation; Maintaining constant current
Abstract
The application provides a control circuit and a pre-charging circuit of an LED display screen pre-charging circuit. The control circuit of the LED display screen pre-charging circuit comprises: a logic circuit generating a logic control signal; the reference voltage generating circuit generates a reference signal according to the logic control signal; the reference signal is used as an input signal of the pre-charging circuit, and the logic control signal controls the output state of the pre-charging circuit; and in one display period, the reference voltage generating circuit and the pre-charging circuit are configured according to the logic control signal. The control circuit adopting the pre-charging circuit can obtain better LED display effect.
Description
Technical Field
The application relates to the field of LED display screens, in particular to a control circuit and a pre-charging circuit of an LED display screen.
Background
At present, common LED display screen driving chip systems in the market drive scanning row lines at different times respectively. In multi-line scanning, ghosting is an earlier discovered display problem. The reason for this is that: during the switching operation, the parasitic capacitance is charged and discharged, so that the LED which is not lighted is lighted. The ghost phenomenon can be divided into an upper ghost and a lower ghost. The lower ghost is caused by the parasitic capacitance being discharged to a low potential and the row forming a charging path after the row is changed. In addition, the LED display screen also has the problems of poor display such as dark first line, high-low gray coupling, cross-board chromatic aberration and the like.
For example, fig. 1 shows a common structure of the LED display driver in the unit panel of the common-anode (the anodes of the 3 kinds of RGB beads are connected together, and the cathodes are separated), in which only beads of one color are shown, and the common-cathode (the cathodes of the 3 kinds of RGB beads are connected together, and the anodes are separated) in the unit panel of the common-cathode LED display screen is to reverse all the LED beads in fig. 1.
The row drivers are typically PMOS transistors and the column drivers are typically constant current sources. Typically, a constant current source driver chip will include a plurality of constant current output driver channels, with the constant current output driver channel (OUT) being terminated to the column lines of fig. 1, i.e., column 1, column 2 ….
The working principle is as follows:
1. firstly, displaying a 1 st row, wherein the PMOS in the 1 st row is conducted, the PMOS in other rows is closed, the row line of the 1 st row is connected with a power supply, and the row lines of other rows are high impedance;
2. the column driving, namely the constant current source driving, correspondingly outputs the constant current sources according to the display data of the 1 st row in columns, lights the LED display lamp beads of the 1 st row, and displays the display image of the 1 st row;
3. and (4) line changing is carried out in sequence, the steps 1-2 are repeated, and all lines are displayed.
Fig. 2 is a channel circuit structure of a general LED display screen constant current source driving chip with a precharge function ((a) common anode LED display screen constant current driving channel circuit structure and (b) common cathode display screen constant current driving channel circuit structure), which mainly includes two parts: constant current source output circuit and pre-charge circuit. Wherein, the pre-charging reference potential is the reference potential of the input pre-charging circuit; the precharge control signal is a signal for controlling the precharge circuit, and generally comprises one or more control signals; the display data is an input signal of the constant current source output circuit; and the OUT end is an output end of the constant current source output channel and is connected with a column line of the LED display screen.
The use of constant current source drive with precharge function for display brings about another undesirable problem: the constant current output of the constant current chip without the pre-charging circuit only has one constant current path, and the constant current output electric quantity generated by the display data can be completely used for lightening the LED lamp beads, so that the light emission of the LED lamp beads is completely controlled by the display data; the pre-charging circuit is a newly introduced current path, and the current path can shunt the constant current output electric quantity generated by the display data, and because of the influence of parasitic capacitance, the constant current output electric quantity shunted by the pre-charging circuit under different display images is different, so that display abnormity is caused, and the main performance is as follows: poor high-low gray coupling display, poor cross-panel display and gray difference cross-unit-panel display.
The existing LED display screen constant current source driving chip with the pre-charging function adjusts the working state of the pre-charging circuit through the control circuit to overcome the problems, however, the existing control circuit controls each working stage of the pre-charging circuit, the configuration of the pre-charging potential output by the pre-charging circuit is not flexible enough, even the pre-charging potential is restricted mutually, the working state of the pre-charging circuit on a single display period is more, and the pre-charging process is more complicated; how to select the starting time and the ending time of each pre-charging stage (namely each working state) of the pre-charging circuit by the control circuit is still not reasonable and perfect, so that the effects of solving the problems of ghost, dark first row, high-low gray coupling, poor cross-board display and the like are still not obvious.
How to solve the technical problems becomes a problem to be solved urgently.
Disclosure of Invention
The technical problem that this application will solve is not enough to the above-mentioned of prior art, provides a control circuit and pre-charge circuit of LED display screen pre-charge circuit, and control is nimble, simple, can eliminate ghost down more effectively, solves the problem that the first line is dark on the left, solves the height grey coupling that appears in the LED display screen and strides board colour difference scheduling problem, promotes the display effect comprehensively.
In one aspect, the present application provides a control circuit of a precharge circuit of an LED display screen, which includes:
a logic circuit generating a logic control signal;
the reference voltage generating circuit generates a reference signal according to the logic control signal;
the reference signal is used as an input signal of the pre-charging circuit, and the logic control signal controls the output state of the pre-charging circuit;
in one display period, the reference voltage generating circuit and the pre-charging circuit are configured according to the logic control signal:
when the display data of the display area is equal to 0, the output potential of the pre-charging circuit is configured to be, in sequence according to the reference signal and the logic control signal: a first potential VR1, a third potential VR3, a fourth potential VR4, a second potential VR2, or a first potential VR1, a third potential VR3, a fourth potential VR4, a high impedance state, a second potential VR 2;
when the display data of the display area is not equal to 0, the output potential of the pre-charge circuit is configured to be a first potential VR1, a high-resistance state and a second potential VR2 in sequence according to the reference signal and the logic control signal.
Compared with the control circuit of the traditional LED display screen pre-charging circuit, the control circuit of the LED display screen pre-charging circuit has the advantage that when the control circuit controls the pre-charging circuit to output pre-charging potential (namely, output potential), the control process is more flexible and simpler. Compared with the conventional method, the precharge potential of the output configured for the precharge circuit is relatively independent in each precharge stage, and is not restricted to each other, for example, after and before the line change, the precharge circuit outputs VR1 and VR2 are configured respectively, that is, the column lines connected with the output terminal of the precharge circuit are charged to VR1 and VR2 respectively, and the potentials VR1 and VR2 can be adjusted independently, so that the effects of eliminating the first line bias and removing the lower ghost can be simultaneously optimized.
In addition, when the display data is 0 (namely no display or the constant current source is not turned on in the display area), the output of the pre-charging circuit is sequentially configured to be VR1, VR3, VR4 and VR2, or VR1, VR3 and VR4, a high-impedance state and VR 2; when the display data is not 0 (i.e., there is a display or the constant current source is on in the display area), the precharge circuit output is sequentially configured as VR1, high impedance state, VR 2. The control circuit controls the pre-charging process of the pre-charging circuit to be simpler than the traditional pre-charging process.
Alternatively, the potential of the reference signal is configured to be a first potential VR1, a third potential VR3, a fourth potential VR4, and a second potential VR2 in this order, and corresponds to the output potentials of the precharge circuit, i.e., the first potential VR1, the third potential VR3, the fourth potential VR4, and the second potential VR2, one to one. This can ensure the accuracy of the control.
Optionally, the control circuit comprises at least one pre-charge circuit; the control circuit selects one pre-charging circuit according to the logic control signal, and the selected pre-charging circuit configures an output potential according to the reference signal and the logic control signal.
The pre-charging potential requirements are different for the common anode display screen and the common cathode display screen. The application further proposes the configuration relation of the first potential VR1, the second potential VR2, the third potential VR3 and the fourth potential VR4 for different display screens: when the LED display screen is a common-anode display screen, the third potential VR3 is greater than the first potential VR1, the third potential VR3 is greater than the second potential VR2, and the third potential VR3 is greater than the fourth potential VR 4; when the LED display screen is a common cathode display screen, the third potential VR3 is less than the first potential VR1, the third potential VR3 is less than the second potential VR2, and the third potential VR3 is less than the fourth potential VR 4. Taking the common anode display screen as an example, VR3 is larger than other pre-charging potentials, so that when there is no display, the change of the column line voltage can simulate the process of starting the constant current source when there is a display, and the circuit conditions are as close as possible when there is a display and when there is no display, thereby effectively solving the problems of poor high-low gray coupling display and poor cross-board display.
Alternatively, the control circuit may select between stages of arranging the output potential of the precharge circuit, for example, between a stage of arranging the output potential as the first potential VR1 and a stage of arranging the output potential as the third potential VR3, depending on the display effect that there may be a case where the precharge circuit is turned off, and specifically whether or not there is turning off depending on the actual display effect. Through the nimble closed state that sets up, can adjust the display effect in a flexible way, on the other hand can also reduce the display screen power consumptive.
Specifically, when the output potential of the precharge circuit is sequentially arranged as a first potential VR1, a third potential VR3, a fourth potential VR4, and a second potential VR2, a time interval between adjacent arrangements is 0 or more; and when the time interval is greater than 0, the output of the pre-charging circuit is in a high-impedance state in the time interval.
Alternatively, when the display data of the display region is not equal to 0, the end time at which the output potential is set to the first potential VR1 and the start time at which the output potential is set to the second potential VR2 are adjusted according to the display data of the display region. That is, when there is display, the ending time of the stage of the arrangement potential being the first potential VR1 and the starting time of the stage of the arrangement potential being the second potential VR2 are adjusted according to the starting time and the ending time of the display data, so that the selection of the ending time and the starting time is closely related to the display data, the selection of the starting time and the ending time of each working stage of the pre-charging circuit is more reasonable and perfect, and the display effect can be improved to the maximum extent.
Optionally, the ending time of configuring the output potential as the first potential VR1 and the starting time of configuring the output potential as the second potential VR2 are adjusted according to the display data of the display area, specifically: setting the output potential to be the first potential VR1, wherein the interval from the ending time of the first potential VR1 to the beginning time of the display data is greater than or equal to 0; the interval from the end time of the display data to the start time of the arrangement of the output potential as the second potential VR2 is greater than or equal to 0.
When there is display, the selection range of the ending time of the stage of the arrangement potential being the first potential VR1 is set as the time when or before the display data starts, and the starting time of the stage of the arrangement potential being the second potential VR2 is set as the time when or after the display data ends, the selection ranges of the ending time and the starting time are related to the display data, the selection range can change according to the actual starting time and the ending time of the changed display data, the selection of the starting time and the ending time of the working stage of the pre-charging circuit is more reasonable and perfect, and the possibility of improving the display effect is improved.
Alternatively, in order to achieve sufficient precharging, that is, to make the precharge voltages VR1 and VR2 as high as possible in the presence of display, and avoid the situation that the predetermined potential may not be reached in the period of the arrangement potential VR1 and the period of the arrangement potential VR2, the present application further limits the ending time of the stage of the arrangement potential VR1 and the starting time of the stage of the arrangement potential VR2 to be selected as close as possible to the time range of the start of display data or the end of display data. Specifically, the method comprises the following steps:
when the start time of the display data is greater than the start time of the display region, the interval from the start time of the display region to the end time of arranging the output potential at the first potential VR1 is greater than 0, and the interval from the end time of arranging the output potential at the first potential VR1 to the start time of the display data is greater than or equal to 0;
when the starting time of the display data is equal to the starting time of the display area, configuring the ending time of which the output potential is the first potential VR1 as the starting time of the display data;
when the end time of the display data is less than the end time of the display region, the interval from the end time of the display data to the start of setting the output potential to the second potential VR2 is greater than or equal to 0, and the interval from the start of setting the output potential to the second potential VR2 to the end of the display region is greater than 0;
when the end time of the display data is equal to the end time of the display area, the start time of the output potential being the second potential VR2 is configured to be the end time of the display data.
Alternatively, in order to achieve sufficient precharging to the maximum extent in the case of having a display, the end time of disposing the output potential as the first potential VR1 may be specifically selected as the start time of the display data; the start time of the output potential being the second potential VR2 is configured to be the end time of the display data.
An embodiment of the present application further provides a precharge circuit of an LED display screen, which is controlled by the control circuit of the precharge circuit of the LED display screen.
Adopt the control circuit and the precharge circuit of the LED display screen precharge circuit of this application to have following effect:
(1) after line changing, the output potential of the pre-charging circuit is configured to be VR1, namely the voltage of a column line connected with the output end of the pre-charging circuit is charged to VR1, and the state and the environment of each line before display are the same, so that the first line of the LED display screen is eliminated from being darker; before line changing, the output potential of the pre-charging circuit is configured to be VR2, namely the column line voltage is charged to VR2, so that ghost can be eliminated; when no display exists, the output potential of the pre-charging circuit is configured to be VR3 and VR4 in sequence, and the constant current source starting process can be simulated by matching the output potential of the pre-charging circuit and the output potential of the pre-charging circuit, so that the circuit conditions under the condition of no display and the condition of display are as close as possible, and the poor high-low gray coupling display and the poor cross-board display can be effectively improved;
(2) the pre-charging potentials configured in each time period (each stage configured with different output potentials) are adjusted according to the display effect, the adjusting process is flexible and simple, the pre-charging potentials in each stage are not restricted, and the pre-charging process on a single display period is relatively simple;
(3) when the display is performed, the selection of the ending time of the period with the configuration potential VR1 and the starting time of the period with the configuration potential VR2 is closely related to the display data, and the starting time and the ending time of the display data can be different in different periods, so that the selection range of the ending time and the starting time is wider and more flexible, the selection of the starting time and the ending time of each pre-charging stage is more reasonable and perfect, and the display effect can be improved to the maximum extent.
Drawings
FIG. 1 is a common configuration of LED display drivers within a common anode LED display screen unit panel;
FIG. 2 is a channel circuit structure diagram of a common LED display screen constant current source driving chip with a pre-charging function;
FIG. 3 is a block diagram of an LED display pre-charge circuit and a control circuit thereof according to an embodiment of the present disclosure;
FIG. 4 is a timing diagram of a control circuit of a pre-charge circuit of an LED display screen during non-display according to an embodiment of the present application;
FIG. 5 is a timing diagram of a control circuit of a pre-charging circuit of an LED display screen with a display according to an embodiment of the present application;
FIG. 6 is a first schematic diagram of a precharge circuit according to an embodiment of the present disclosure;
FIG. 7 is a schematic diagram of a precharge circuit according to an embodiment of the present application;
in the figure: 1-a logic circuit; 2-a reference voltage generating circuit; 3-precharge circuit.
Detailed Description
The technical solutions of the present application will be further described in detail with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present application, and the scope of the present application is not limited to the following.
The control circuit adjusts the working state of the pre-charging circuit in time sequence, can solve the problems of ghost shadow and dark first line in LED display, and can effectively improve poor high-low gray coupling display and poor cross-board display; the control is flexible, and the pre-charging process on a single display period is simple.
The working states of the precharge circuit defined in the present application are totally 5: state 1, state 2, state 3, state 4, and state 5. The respective states are explained in detail below:
state 1: pre-charging the column lines (output of the constant current driving channels of the constant current driving chips) of the display screen, so that the corresponding column lines are charged to a first potential VR1 (namely the pre-charging potential is VR1), all LED lamp beads on the corresponding column lines are in a cut-off state (do not emit light), and the state and the environment of each line before display are the same at the moment, so that the phenomenon that the first line of the LED display screen is dark (the first line of the display of each constant current driving chip) is eliminated;
state 2: pre-charging a column line (output of a constant current driving channel of a constant current driving chip) of the display screen to enable the corresponding column line to be charged to a second potential VR2, and enabling all lamp beads on the corresponding column line to be in a cut-off state (not to emit light) so as to eliminate the lower ghost of the LED display screen;
state 3: a precharge off state; at this time, the precharge circuit is turned off, and the Output (OUT) is in a high-impedance state; namely the high impedance state of the output end of the pre-charging circuit;
and 4: pre-charging the column lines (output of the constant current driving channel of the constant current driving chip) of the display screen to enable the corresponding column lines to be charged to a third potential VR3, and enabling all lamp beads on the corresponding column lines to be in a cut-off state (not to emit light);
and state 5: pre-charging the column lines (output of the constant current driving channel of the constant current driving chip) of the display screen to enable the corresponding column lines to be charged to a fourth potential VR4, and enabling all lamp beads on the corresponding column lines to be in a cut-off state (not to emit light);
the state 4 and the state 5 are used for simulating the starting process of the constant current source on the column line, so that the circuit condition when no display exists is as close as possible to the circuit condition when display exists, and the poor high-low gray coupling display and the poor cross-board display are effectively improved.
The stage in which the precharge potential is set to VR in accordance with the reference signal and the control signal means a stage in which the precharge circuit charges the column line connected to the output terminal thereof to the VR potential under the control of the control circuit.
The potentials VR1, VR2, VR3, and VR4 described above may be specifically configured in consideration of the following points:
VR1 corresponds to state 1, and this pre-charge potential mainly acts to keep the state and environment of each line before display the same, can solve the problem that the first line of each constant current driving chip of the LED display screen is dark, and is also used for adjusting low gray color cast. For a common-sun display screen, the lower the potential of VR1 is, the better the effect of dark first line is, the higher the low-gray display brightness is, and the poor display of directly lighting the lamp beads is caused by too low VR 1; for a common-cathode display screen, the higher the VR1 potential is, the better the effect of dark first line is, the higher the low-gray display brightness is, and the poor display of directly lighting the lamp beads is caused by the excessively high VR 1;
VR2 corresponds to state 2, and the pre-charge level mainly acts to eliminate the ghost image under the display screen. For a common-anode display screen, the higher the VR2 potential is, the better the shadow eliminating effect is, and the poor display of directly lighting the lamp beads is caused by too low VR 2; for a common-cathode display screen, the lower the VR2 potential is, the better the shadow eliminating effect is, and the too high VR2 can cause poor display of directly lighting the lamp beads;
VR3 and VR4 are paired and respectively correspond to state 4 and state 5, and VR3 and VR4 are mainly used for compensating poor display caused by a shadow elimination circuit, such as poor display due to high-low gray coupling and poor display due to cross-board chromatic aberration. For a common-sun display screen, VR3 and VR4 are too low to cause poor display of directly lit beads. When VR4 is larger than VR3, the larger the value of VR4-VR3 is, the brighter the LED lamp bead is after compensation; when VR4 is smaller than VR3, the larger the value of VR3-VR4 is, the darker the LED lamp bead is after compensation. For a common cathode display screen, VR3 and VR4 are too high to cause poor display of directly lit beads. When VR4 is larger than VR3, the larger the value of VR4-VR3 is, the darker the LED lamp bead is after compensation; when VR4 is smaller than VR3, the larger the value of VR3-VR4 is, the brighter the LED lamp bead is after compensation.
In an alternative embodiment, the precharge potentials VR1, VR2, VR3 and VR4 may be arranged in the following relationship: when the LED display screen is a common-anode display screen, VR3 is larger than VR1, VR3 is larger than VR2, and VR3 is larger than VR 4; when the LED display screen is a common cathode display screen, VR3 is smaller than VR1, VR3 is smaller than VR2, and VR3 is smaller than VR 4.
Taking the common anode display screen as an example, VR3 is larger than other pre-charging potentials, so that when there is no display (when the display data is 0), the change of the column line voltage can simulate the process of starting the constant current source when there is a display, and the circuit conditions are as close as possible when there is a display and when there is no display, thereby effectively solving the problems of poor high-low gray coupling display and poor cross-panel display.
As shown in fig. 3, a control circuit of a precharge circuit of an LED display panel according to an embodiment of the present application includes:
a logic circuit 1 for generating a logic control signal;
a reference voltage generating circuit 2 for generating a reference signal according to the logic control signal;
the reference signal is used as an input signal of a pre-charging circuit 3, and the logic control signal controls the output state of the pre-charging circuit 3;
in one display period, the reference voltage generating circuit 2 and the pre-charging circuit 3 are configured according to the logic control signal:
when the display data of the display area is equal to 0, the output potential of the precharge circuit 3 is configured to, in order according to the reference signal and the logic control signal: VR1, VR3, VR4, VR2, or VR1, VR3, VR4, high impedance state, VR 2;
when the display data of the display area is not equal to 0, the output potential of the precharge circuit 3 is configured to, in order according to the reference signal and the logic control signal: VR1, high impedance state, VR 2.
It can be understood that the output terminal of the pre-charge circuit 3 is connected to the column line of the display screen (the output of the constant current driving channel of the constant current driving chip), and the column line of the display screen is pre-charged, so that the corresponding column line is charged to a potential, which is the output potential of the pre-charge circuit 3, that is, the pre-charge potential. Further, the phase in which the output potential of the precharge circuit is configured to the VR potential in accordance with the reference signal and the logic control signal means a period in which the precharge circuit operates in a certain state (state 1 to state 5) described above, that is, a period in which the precharge circuit charges the column line to precharge it to the VR potential under the control of the control circuit.
It is understood that the display period refers to a time when one line is displayed. When a certain row is displayed, the MOS of the row is conducted, and then the LED lamp beads of the row are lightened according to the output constant current sources corresponding to the row display data. In one display period, a complete display frame can be displayed, and a subframe can also be displayed. In other words, in one display period, a certain line of display data can be displayed, and after line feed, the next line of display data can be displayed in the next display period. Or, the display data of each row is partitioned into blocks, that is, divided into a plurality of subframes, in one display period, the subframe of one row is displayed first, and after the row is changed, the subframe of the next row of display data is displayed in the next display period; … …, respectively; and after the first sub-frames of all the rows are displayed, sequentially displaying the second sub-frames according to the mode until all the sub-frames are displayed.
Specifically, when the display data of the display area is equal to 0, in other words, the constant current source is not turned on in the display area; of course, the constant current source is not turned on in the display area and can be considered as no display; when the display data of the display area is not equal to 0, in other words, the constant current source is turned on in the display area; of course, the constant current source is on in the display area and may be considered to have a display.
The control circuit has a simple structure, and the working process of controlling the pre-charging circuit 3 is simple, flexible and effective. It can be understood that the potentials VR1, VR2, VR3 and VR4 corresponding to each precharge stage are not restricted, and can be adjusted independently according to the actual display effect, and the precharge process is flexible. For example, after line feed and before line feed, the pre-charging to VR1 and the pre-charging to VR2 are respectively independent and can be adjusted independently, so that the problem that the mutual restriction of the problem of removing the lower ghost and the first line is too dark is avoided, and the effects of removing the lower ghost and the first line is too dark can be achieved.
Alternatively, the potentials of the reference signals are sequentially configured to VR1, VR3, VR4, VR2, and correspond one-to-one to the output potentials VR1, VR3, VR4, VR2 of the precharge circuit 3.
It will be appreciated that the reference voltage generating circuit 2 outputs VR to the precharge circuit 3 according to the logic control signal of the logic circuit 1, while the logic control signal is input to the precharge circuit 3, the precharge circuit 3 outputting corresponding VR at the output terminal according to the received reference potential VR and the logic control signal. The potential inputted to the precharge circuit 3 is the same as the potential outputted from the precharge circuit 3, and the precharge circuit 3 is actually an operational amplifier whose amplification factor is 1. This is advantageous in ensuring accuracy.
Alternatively, the reference voltage generating circuit 2 may generate the reference signal according to the logic control signal by: the reference voltage generating circuit 2 generates VR1, VR2, VR3 and VR4, logic control signals of the logic circuit 1 are input into the reference voltage generating circuit 2, and then the reference voltage generating circuit 2 is controlled to select one of VR 1-VR 4 to be used as a reference signal to be output to the pre-charging circuit 3. In other words, as long as the chip is powered, the 4 potentials VR 1-VR 4 are generated according to the register configuration, and the logic control signal can be used to select and output one of VR 1-VR 4. Of course, the reference voltage generating circuit 2 may generate other different VRs according to the requirement, and select any one or more outputs according to the logic control signal, which is not limited to the four potentials, and the application is not limited thereto.
Optionally, the control circuit comprises at least one pre-charge circuit 3; the control circuit selects one of the precharge circuits 3 according to the logic control signal, and the selected precharge circuit 3 configures an output potential according to the reference signal and the logic control signal.
It is understood that the present application may employ one precharge circuit 3, the control circuit controlling the precharge circuit 3 to sequentially output desired potentials, for example, the logic control signal controlling the reference voltage generating circuit 2 to output VR, VR and the logic control signal being input to the precharge circuit 3, the precharge circuit 3 outputting the potential VR accordingly, and then outputting another potential in this manner, and so on; it is also possible to employ a plurality of precharge circuits 3, and before charging the column line, the control circuit selects one precharge circuit 3 by a logic control signal, inputs a reference potential and the logic control signal to the selected precharge circuit 3, and charges the column line by the selected precharge circuit 3. For example, m precharge circuits are provided, and when the reference potential is VR1, the first precharge circuit is selected, and the output end of the precharge circuit is charged to VR 1; … …, when the reference potential is VRm, the m-th precharge circuit is selected, and the output terminal of the precharge circuit is charged to VRm. Of course, m precharge circuits are not necessarily configured for m potentials, the number of precharge circuits can be selected as required, and only one of the precharge circuits needs to be selected according to the logic control signal to input the reference signal and the logic control signal.
The control of the precharge circuit 3 by the control circuit provided in the present application is described in detail below with reference to fig. 4-5 of the specification.
Fig. 4 is a timing diagram of a control circuit of a precharge circuit of an LED display panel when there is no display according to an embodiment of the present application. As shown in fig. 4, the control circuit controls the precharge circuit 3 to sequentially operate in: state 1, state 4, state 5, state 2; in the state 1, the problem that the first line of the LED display screen is dark (the first line is displayed by each constant current source driving chip) can be solved; the state 4 and the state 5 appear in pairs and are used for simulating the starting process of the constant current source on the column line, so that the circuit working condition can be as close as possible to the circuit working condition when the display is available when no display is available, namely the constant current source is not started in the display area, and therefore the poor high-low gray coupling display and the poor cross-board display are effectively improved; and in the state 2, the lower ghost of the LED display screen can be eliminated.
FIG. 5 is a timing diagram of a control circuit of a precharge circuit of an LED display panel with display according to an embodiment of the present application. As shown in fig. 5, the control circuit controls the precharge circuit 3 to sequentially operate in: state 1, state 3, state 2. In the state 1, the problem that the first line of the LED display screen is dark (the first line is displayed by each constant current source driving chip) can be solved; and in the state 2, the lower ghost of the LED display screen can be eliminated.
Each state in fig. 4-5 has a precharge area in the display period, i.e., precharge 1, precharge 2, precharge 3, precharge 4, precharge 5, precharge 6, precharge 7 in the figure. For example, in the precharge 1 region, the control circuit controls the precharge circuit 3 to operate in the state 1 (precharge the column line, charge it to VR1), referring to the time period corresponding to this region, the logic circuit 1 in the control circuit generates the logic control signal, the reference voltage generating circuit 2 generates the reference signal according to this logic control signal, the precharge circuit 3 outputs the desired precharge potential VR1 according to the logic control signal and the above reference signal, i.e., in this time period, the output potential of the precharge circuit 3 is configured to be VR1 according to the reference signal and the logic control signal. The start time and the end time at which the output potential of the precharge circuit 3 is arranged to be VR refer to the start time and the end time of the corresponding precharge region, respectively.
Alternatively, the duration of the state i (i being a positive integer between 1 and 5), i.e. the time the corresponding pre-charged area occupies over the display period, is adjustable according to the display effect. For example, 0 may be taken or not taken, that is, greater than 0, depending on the display effect; the minimum value can be obtained according to the actual display effect on the premise that the actual pre-charging potential reaches the preset value.
Optionally, the time interval from the line feed to the start of the precharge 1 and precharge 5 regions is equal to or greater than 0. The adjustment can be specifically carried out according to the actual display effect.
Alternatively, when the output potentials of the precharge circuits 3 are arranged in sequence as VR1, VR3, VR4 and VR2, the time interval between adjacent arrangements is equal to or greater than 0, and when the time interval is greater than 0, the Output (OUT) of the precharge circuit 3 is in a high-impedance state during the time interval, that is, the precharge circuit operates in state 3. The time between adjacent configurations refers to the time between the end of the last pre-charge region and the start of the next pre-charge region. In other words, there may be cases where the precharge circuit 3 is turned off depending on the display effect between the respective operating states (i.e., the respective precharge regions) of the precharge circuit, i.e., whether the precharge circuit 3 outputs a high impedance state, is specifically set to the off state, may be selected depending on the actual display effect. Understandably, the display effect can be flexibly adjusted by flexibly setting the closing state; on the other hand, the power consumption of the display screen can be reduced.
Specifically, the state 3 between the end of precharge 1 and the start of precharge 2, the end of precharge 2 to the start of precharge 3, and the end of precharge 3 to the start of precharge 4, that is, the precharge off state, may be selectively set according to the actual display effect, at which time the precharge circuit 3 is turned off, outputting the high impedance state. Based on this, the working state of the pre-charging circuit can be as follows: state 1, high resistance state, state 4, state 5, and state 2; state 1, state 4, high resistance state, state 5, and state 2; state 1, state 4, state 5, high resistance state and state 2; state 1, high resistance state, state 4, high resistance state, state 5, and state 2; state 1, high resistance state, state 4, state 5, high resistance state, state 2; state 1, state 4, high resistance state, state 5, high resistance state, state 2; state 1, high resistance state, state 4, high resistance state, state 5, high resistance state, state 2.
It can be understood that the start and end times of each operating state of the pre-charging circuit, i.e. the start and end times of the time period corresponding to each pre-charging area, can be adjusted according to the actual display effect.
Optionally, the precharge 3 start time may also be set at the beginning or after the display area, and the end time may be set before or at the end of the display area. At this time, the time interval from the start of the display area to the start of the precharge 3 is equal to or greater than 0, when greater than 0, the precharge state is set to state 3, the time interval from the end of the precharge 3 to the end of the display area is equal to or greater than 0, when greater than 0, the precharge state is set to state 3; the precharge circuit 4 may be started at or after the end of the display area, in which case the time interval from the end of the display area to the start of the precharge circuit 4 is equal to or greater than 0, and when greater than 0, the operation state of the precharge circuit is set to state 3. Further, precharge 2 (state 4) may be set to end before or at the start of the display area, in which case the time interval from the end of precharge 2 to the start of the display area is equal to or greater than 0, and when greater than 0, this interval precharge state is state 3.
Referring to fig. 5, when there is a display, the display data (gray portion) in the display area is not equal to 0, and at this time, the constant current source is turned on in the display area, and the LED lamp bead emits light based on the display data. The position of the starting point of the display data (indicating the starting time of the initial light emission of the LED lamp beads in the display area) from the starting point of the display area (the starting time of the display area) is adjustable; and similarly, the position of the end of the display data (indicating the end of the last light emission of the LED lamp beads in the display area) is adjustable. For example, it is possible to select to set the display data on different periods to start at the same position within the display area or to end at the same position within the display area. The application is not limited thereto. The display data width is different based on different requirements of the LED display. Thus, the display data start or end times are typically at least one different within the display area.
In order to improve the display effect, when the display data is not equal to 0, the ending time of the output potential VR1 and the starting time of the output potential VR2 are adjusted according to the display data of the display area. Specifically, the end time of the stage at which the arrangement potential is VR1 and the start time of the stage at which the arrangement potential is VR2 are adjusted according to the start and end times of display data, respectively. Wherein, the start time and the end time of the arrangement of the output potential VR refer to the start time and the end time of the precharge region in which the working state of the precharge circuit corresponding to the potential is located (in this case, VR1 corresponds to state 1 in the precharge 5 region, and VR2 corresponds to state 2 in the precharge 7 region).
It can be understood that, with the control circuit of the present application, when there is a display, the selection of the ending time of the stage of configuring the output potential of the pre-charge circuit 3 as VR1 and the starting time of the stage of configuring the output potential as VR2 is closely related to the display data, and the selection of the starting time and the ending time of each pre-charge stage is more reasonable and perfect, so that the display effect can be improved to the greatest extent.
Optionally, when the display data is not equal to 0, the interval from the end time of VR1 to the start time of the display data is configured to be equal to or greater than 0. In other words, the ending time of the pre-charge 5 can be adjusted according to the specific starting time and the display effect of the display data at the beginning of the display data, after the display area begins and before the display data begins, or at the beginning of the display area.
It will be appreciated that in some displays, the parasitic capacitance is discharged to a low potential, and therefore the column will form a charge path after the row is changed, resulting in the occurrence of ghosting. At this time, the timing of starting the precharge 7 (state 2) affects the effect of removing the lower ghost. In an alternative embodiment, the interval from the end time of the display data to the start time of the configuration of the output potential VR2 of the precharge circuit 3 is equal to or greater than 0. In other words, the time when the precharge 7 starts may be at the end of the display data, after the end of the display data and before the end of the display area, at the end of the display area, or after.
It can be understood that the selection range of the end time of the precharge 5 (i.e. the stage of setting the output potential of the precharge circuit 3 to VR1) is set to be at or before the start of the display data, and the selection range of the start time of the precharge 7 (i.e. the stage of setting the output potential of the precharge circuit 3 to VR 2) is set to be at or after the end of the display data, the selection ranges of the end time of the precharge 5 and the start time of the precharge 7 are associated with the display data, the selection ranges of the end time of the precharge 5 and the start time of the precharge 7 can be varied according to the actual start time and end time of the varied display data, the selection of the start time and the end time of the precharge state is more reasonable and perfect, and the possibility of improving the display effect is improved.
When display is available, the constant current source is started, the LED emits light, and the parasitic capacitance in the circuit has charging and discharging conditions. In order to achieve sufficient precharging with display, that is, to make the precharge 5 stage and the precharge 7 stage as much as possible reach the precharge potentials VR1 and VR2, avoiding the situation that the precharge voltage may not reach the predetermined voltage during the time of precharging 5 and precharging 7, the ending time of precharging 5 and the starting time of precharging 7 are selected as close as possible to the time range where display data starts or ends.
Optionally, when the display data is not equal to 0, when the start time of the display data is greater than the start time of the display area, the interval from the start time of the display area to the end time of arranging the output potential VR1 is greater than 0, and the interval from the end time of arranging the output potential VR1 to the start time of the display data is greater than or equal to 0;
when the start time of the display data is equal to the start time of the display area, the end time at which the output potential VR1 is configured is the start time of the display data.
Alternatively, the end time at which the output potential is configured to be VR1 is directly selected as the start time of the display data. In other words, the end time of the precharge 5 can be directly selected as the display data start time.
Optionally, when the ending time of the display data is less than the ending time of the display area when the display data is not equal to 0, the interval from the ending time of the display data to the beginning of arranging the output potential VR2 is greater than or equal to 0, and the interval from the beginning of arranging the output potential VR2 to the ending time of the display area is greater than 0;
when the end time of the display data is equal to the end time of the display area, the start time at which the output potential VR2 is configured is the end time of the display data.
Alternatively, the start time at which the output potential is configured to be VR2 is directly selected as the end time of the display data. In other words, the start time of the precharge 7 can be directly selected as the display data end time.
In addition, referring to fig. 5, in precharge 6 region, precharge circuit 3 operates in state 3, i.e., precharge circuit is turned off. In other words, after precharge 5 ends, the precharge circuit is turned off until precharge 7 begins.
In another embodiment of the present application, a precharge circuit for an LED display panel is provided, which is controlled by the control circuit of the precharge circuit for an LED display panel. The specific circuit structure of the precharge circuit is exemplarily described as follows:
a precharge circuit provided in one embodiment of the present application is shown in fig. 6, where the precharge circuit 3 includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a first switching element, and a second switching element;
the source electrodes of the first transistor and the second transistor and the first end of the first switch element are connected to a working voltage VDD in common; a gate of the first transistor is connected to a drain of the first transistor, a gate of the second transistor, a second terminal of the first switching element, and a drain of the third transistor; a source electrode of the third transistor, a source electrode of the fourth transistor and a first end of the second switch element are connected in common; a second terminal of the second switching element is electrically connected to a drain of the fifth transistor; the grid electrode of the fifth transistor receives bias voltage, and the source electrode of the fifth transistor is grounded; the third end of the first switch element and the third end of the second switch element are connected in common and used as a first input end for receiving the logic control signal; the grid electrode of the third transistor is used as a second input end and receives the reference signal; the drain of the second transistor is connected to the drain and the gate of the fourth transistor in common, and the drain and the gate of the second transistor serve as output terminals to output a precharge potential.
Third ends of the first switching element and the second switching element are used as first input ends and receive the logic control signal; a gate of the fifth transistor receives a bias voltage; a gate of the third transistor receives a reference signal. The logic control signal and the reference signal are provided by the logic circuit 1 and the reference voltage generating circuit 2, respectively.
It is understood that the precharge circuit 3 is actually an operational amplifier, and can output the precharge potential through the output terminal by configuring different reference signals under the coordination of the first switching element and the second switching element, i.e. the column line connected with the output terminal is charged to the target precharge potential.
Optionally, the first transistor, the second transistor and the first switching element are selected to be PMOS transistors, and are respectively represented by PM0, PM1 and PM2 in fig. 6; the third transistor, the fourth transistor, the fifth transistor, and the second switching element are NMOS, and are respectively represented by NM0, NM1, NM2, and NM 3. The first terminal of the PM2 is a source, the second terminal is a drain, and the third terminal is a gate. The first terminal of NM3 is a drain, the second terminal is a source, and the third terminal is a gate. The circuit is suitable for pre-charging the column lines of the common anode LED display screen.
It is understood that when the logic control signal is low, PM2 is closed, the gate, source and drain of PM0 and the gate and source of PM1 are all VDD, and neither PM0 nor PM1 is turned on. And, the NM3 gate is low, NM3 is off. At this time, the precharge circuit 3 is in an off state and outputs a high impedance state. When the logic control signal is high level, PM2 is off, NM3 is on, PM0, PM1, NM0, NM1 and NM2 form an operational amplifier. At this time, an appropriate reference signal is configured as necessary, and the output terminal of the precharge circuit 3 can charge the column line connected thereto to the above-mentioned reference potential. At this time, the amplification ratio of the operational amplifier is 1, and the accuracy can be improved by adopting such an arrangement.
In an alternative embodiment, a pre-charge circuit for a common cathode LED display screen is provided. As shown in fig. 7, the precharge circuit is different from the precharge circuit suitable for the common anode LED display panel in that the first transistor, the second transistor and the first switching element are NMOS transistors, which are respectively denoted by NM4, NM5 and NM6 in fig. 7; the third transistor, the fourth transistor, the fifth transistor, and the second switching element are PMOS transistors, and are denoted by PM3, PM4, PM5, and PM6, respectively. At this time, the sources of NM4, NM5, NM6 are grounded, and the source of PM5 is connected to the operating voltage VDD. A first end of the NM6 is a source electrode, a second end is a drain electrode, and a third end is a grid electrode; the first terminal of the PM6 is a drain, the second terminal is a source, and the third terminal is a gate.
The foregoing is illustrative of the preferred embodiments of this application, and it is to be understood that this application is not limited to the forms disclosed herein, but is not intended to be exhaustive of other embodiments and that various other combinations, modifications, and environments may be used, and changes may be made within the scope of the inventive concept as described herein, by the above teachings or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the application, which is to be protected by the claims appended hereto.
Claims (10)
1. A control circuit of a pre-charging circuit of an LED display screen is characterized by comprising the following components:
a logic circuit (1) for generating a logic control signal;
a reference voltage generating circuit (2) for generating a reference signal according to the logic control signal;
the reference signal is used as an input signal of a pre-charging circuit (3), and the logic control signal controls the output state of the pre-charging circuit (3);
in one display period, the reference voltage generating circuit (2) and the pre-charging circuit (3) are configured according to the logic control signal:
when the display data of the display area is equal to 0, the output potential of the pre-charge circuit (3) is configured to be, in order according to the reference signal and the logic control signal: a first potential VR1, a third potential VR3, a fourth potential VR4, a second potential VR2, or a first potential VR1, a third potential VR3, a fourth potential VR4, a high impedance state, a second potential VR 2;
when the display data of the display area is not equal to 0, the output potential of the pre-charge circuit (3) is sequentially configured to a first potential VR1, a high-resistance state and a second potential VR2 according to the reference signal and the logic control signal, wherein the first potential VR1 ends before the display data starts, and the second potential VR2 starts after the display data ends;
the first potential VR1 is used for eliminating the first row bias of the LED display screen;
the second potential VR2 is used for eliminating the lower ghost of the LED display screen;
the third potential VR3 and the fourth potential VR4 are used for simulating the starting process of the constant current source on the column line.
2. The control circuit of the precharge circuit of the LED display panel according to claim 1, wherein the potential of the reference signal is configured to be a first potential VR1, a third potential VR3, a fourth potential VR4, and a second potential VR2 in sequence, and corresponds to the output potentials of the precharge circuit (3), i.e., the first potential VR1, the third potential VR3, the fourth potential VR4, and the second potential VR 2.
3. The control circuit of the pre-charging circuit of the LED display screen according to claim 1, characterized in that the control circuit comprises at least one pre-charging circuit (3); the control circuit selects one of the precharge circuits (3) according to the logic control signal; the selected pre-charging circuit (3) configures an output potential according to the reference signal and the logic control signal.
4. The control circuit of the LED display screen pre-charging circuit of claim 1, wherein the first potential VR1, the second potential VR2, the third potential VR3 and the fourth potential VR4 are configured as follows: when the LED display screen is a common-anode display screen, the third potential VR3 is greater than the first potential VR1, the third potential VR3 is greater than the second potential VR2, and the third potential VR3 is greater than the fourth potential VR 4; when the LED display screen is a common cathode display screen, the third potential VR3 is less than the first potential VR1, the third potential VR3 is less than the second potential VR2, and the third potential VR3 is less than the fourth potential VR 4.
5. The control circuit of the precharge circuit of the LED display panel according to claim 1, wherein when the output potential of the precharge circuit (3) is sequentially set to a first potential VR1, a third potential VR3, a fourth potential VR4 and a second potential VR2, the time interval between adjacent sets is greater than or equal to 0; and when the time interval is larger than 0, the output of the pre-charging circuit (3) is in a high-impedance state in the time interval.
6. The control circuit of the precharge circuit of LED display panel according to claim 1, wherein when the display data of the display area is not equal to 0, the end time of setting the output potential to the first potential VR1 and the start time of setting the output potential to the second potential VR2 are adjusted according to the display data of the display area.
7. The control circuit of the LED display screen precharge circuit of claim 6, wherein the ending time of configuring the output potential as the first potential VR1 and the starting time of configuring the output potential as the second potential VR2 are adjusted according to the display data of the display area, specifically: setting the output potential to be the first potential VR1, wherein the interval from the ending time of the first potential VR1 to the beginning time of the display data is greater than or equal to 0; the interval from the end time of the display data to the start time of the arrangement of the output potential as the second potential VR2 is greater than or equal to 0.
8. The control circuit of the LED display screen precharge circuit of claim 6, wherein the ending time of configuring the output potential as the first potential VR1 and the starting time of configuring the output potential as the second potential VR2 are adjusted according to the display data of the display area, specifically:
when the start time of the display data is greater than the start time of the display region, the interval from the start time of the display region to the end time of arranging the output potential at the first potential VR1 is greater than 0, and the interval from the end time of arranging the output potential at the first potential VR1 to the start time of the display data is greater than or equal to 0;
when the starting time of the display data is equal to the starting time of the display area, configuring the ending time of which the output potential is the first potential VR1 as the starting time of the display data;
when the end time of the display data is less than the end time of the display region, the interval from the end time of the display data to the start of setting the output potential to the second potential VR2 is greater than or equal to 0, and the interval from the start of setting the output potential to the second potential VR2 to the end of the display region is greater than 0;
when the end time of the display data is equal to the end time of the display area, the start time of the output potential being the second potential VR2 is configured to be the end time of the display data.
9. The control circuit of the LED display screen precharge circuit of claim 6, wherein the ending time of configuring the output potential as the first potential VR1 and the starting time of configuring the output potential as the second potential VR2 are adjusted according to the display data of the display area, specifically:
setting the end time of the output potential as a first potential VR1 as the start time of the display data; the start time of the output potential being the second potential VR2 is configured to be the end time of the display data.
10. An LED display screen pre-charging circuit, characterized in that the LED display screen pre-charging circuit is controlled by the control circuit of the LED display screen pre-charging circuit according to any one of claims 1 to 9.
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| KR100288037B1 (en) * | 1992-09-14 | 2001-05-02 | 가나이 쓰도무 | Method of driving display device |
| TW521241B (en) * | 1999-03-16 | 2003-02-21 | Sony Corp | Liquid crystal display apparatus, its driving method, and liquid crystal display system |
| TWI264694B (en) * | 2005-05-24 | 2006-10-21 | Au Optronics Corp | Electroluminescent display and driving method thereof |
| JP2007025122A (en) * | 2005-07-14 | 2007-02-01 | Oki Electric Ind Co Ltd | Display device |
| CN104091569B (en) * | 2014-07-31 | 2016-04-20 | 无锡力芯微电子股份有限公司 | LED display system and the driving circuit thereof of LED display ghost can be eliminated |
| CN104934007A (en) * | 2015-07-06 | 2015-09-23 | 合肥京东方光电科技有限公司 | Data line driving method and unit, source electrode driver, panel driving apparatus and display apparatus |
| CN204857145U (en) * | 2015-08-07 | 2015-12-09 | 深圳市绿源半导体技术有限公司 | LED shows grey level compensation drive arrangement and system thereof |
| CN110767153B (en) * | 2019-11-08 | 2020-11-27 | 四川遂宁市利普芯微电子有限公司 | Pre-charging method of LED display screen |
| CN110827748B (en) * | 2019-11-08 | 2020-12-25 | 四川遂宁市利普芯微电子有限公司 | Pre-charging circuit of LED display screen driving chip |
| CN210378420U (en) * | 2019-11-15 | 2020-04-21 | 深圳市富满电子集团股份有限公司 | LED display screen blanking circuit and chip |
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| CN111785205B (en) * | 2020-08-03 | 2023-08-25 | 四川遂宁市利普芯微电子有限公司 | Pre-charging circuit of common-cathode LED display screen driving chip |
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