CN219643890U - Step wave generating circuit, pixel circuit and display device - Google Patents

Step wave generating circuit, pixel circuit and display device Download PDF

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Publication number
CN219643890U
CN219643890U CN202320316503.4U CN202320316503U CN219643890U CN 219643890 U CN219643890 U CN 219643890U CN 202320316503 U CN202320316503 U CN 202320316503U CN 219643890 U CN219643890 U CN 219643890U
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module
signal
voltage
step wave
conversion module
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李全虎
王伙荣
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Xi'an Ti Pt Sr Electronic Technology Co ltd
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Xi'an Ti Pt Sr Electronic Technology Co ltd
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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
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

The utility model belongs to the technical field of display, and provides a ladder wave generating circuit, a pixel circuit and a display device. The step wave generating circuit is applied to the pixel circuit and comprises a counting module and a conversion module, wherein the counting module is electrically connected with the input end of the conversion module, and the output end of the conversion module is electrically connected with the pixel circuit. The counting module is used for receiving the clock signal and the n-bit initial value signal and outputting 2 according to the clock signal and the initial value signal n And (3) target numerical signals, wherein n is a natural number greater than 1. The conversion module is used for receiving the first electricityVoltage signal, second voltage signal and 2 n A target value signal, and according to the first voltage signal, the second voltage signal and 2 n A target value signal, output 2 n Target voltage signal, 2 n The individual target voltage signals form a step wave Sweep. The step wave generation circuit provided by the embodiment of the utility model solves the problem that the step wave generated by the related technology cannot be applied to a pixel circuit.

Description

Step wave generating circuit, pixel circuit and display device
Technical Field
The utility model belongs to the technical field of display, and particularly relates to a ladder wave generating circuit, a pixel circuit and a display device.
Background
In an AM Micro LED (active matrix Micro light emitting diode) display device, a driving manner with an adjustable pulse width needs to be implemented inside a pixel circuit to control the light emitting time of the Micro LED. At present, a mode of combining step wave with capacitive coupling is adopted, and the voltage of a key node is changed along with time so as to control the light-emitting time of the Micro LED.
The related art generates a step wave by using a charge pump principle, and the circuit structure of the circuit mainly comprises a capacitor, a diode and an amplifier, so that the precision of the generated step wave is low due to the characteristics of the device (for example, the conduction voltage drop exists when the diode is conducted). The above-described related art cannot be applied to a pixel circuit because the level maintenance accuracy and the voltage jump accuracy of the pixel circuit to the step wave are extremely high.
Disclosure of Invention
The embodiment of the utility model provides a ladder wave generating circuit, a pixel circuit and a display device, which can solve the problem that the ladder wave generated by the related technology cannot be applied to the pixel circuit.
In a first aspect, an embodiment of the present utility model provides a step wave generating circuit applied to a pixel circuit, including:
a counting module for receiving a clock signal and an n-bit initial value signal and outputting 2 according to the clock signal and the initial value signal n The number of target numerical signals, n is a natural number greater than 1;
the input end of the conversion module is electrically connected with the counting module, the output end of the conversion module is electrically connected with the pixel circuit, and the conversion module is used for receiving a first voltage signal, a second voltage signal and 2 n The target value signal is calculated according to the first voltage signal, the second voltage signal and 2 n Outputting 2 from the target value signal n Target voltage signal, 2 n The largest target voltage signal among the target voltage signals is the first voltageSignal, 2 n The smallest of the target voltage signals is the second voltage signal.
In a possible implementation manner of the first aspect, the counting module includes a counter, and the counter is electrically connected to an input terminal of the conversion module.
In a possible implementation manner of the first aspect, the conversion module is a DAC converter, an input terminal of the DAC converter is electrically connected to the counter, and an output terminal of the DAC converter is electrically connected to the pixel circuit.
In a possible implementation manner of the first aspect, the number of bits of the counter is the same as the number of bits of the DAC converter.
In a possible implementation manner of the first aspect, the counter and the DAC converter are both fabricated using an IC (Integrated Circuit ) process.
In a possible implementation manner of the first aspect, the step wave generating circuit further includes:
the voltage following module, the input of voltage following module with the output electricity of conversion module is connected, the output of voltage following module be used for with pixel circuit electricity is connected, the voltage following module is used for improving conversion module's load capacity.
In a possible implementation manner of the first aspect, the voltage follower module includes an operational amplifier, a non-inverting input terminal of the operational amplifier is electrically connected to the conversion module, and an inverting input terminal of the operational amplifier is electrically connected to an output terminal of the operational amplifier and the pixel circuit, respectively.
In a second aspect, an embodiment of the present utility model provides a pixel circuit, including a pixel module and the step wave generating circuit described in any one of the first aspects; a conversion module in the step wave generation circuit is electrically connected with the pixel module, and the conversion module is used for converting 2 n The target voltage signals are sequentially transmitted to the pixel modules.
In a possible implementation manner of the second aspectThe pixel module comprises a PWM control unit; the PWM control unit is electrically connected with the conversion module in the ladder wave generation circuit and is used for controlling the voltage according to 2 n And controlling the light-emitting time of Micro LEDs in the pixel module by the target voltage signals.
In a third aspect, an embodiment of the present utility model provides a display device including the pixel circuit according to any one of the second aspects.
Compared with the prior art, the embodiment of the utility model has the beneficial effects that:
the embodiment of the utility model provides a ladder wave generating circuit which comprises a counting module and a conversion module, wherein the counting module is electrically connected with the input end of the conversion module, and the output end of the conversion module is electrically connected with a pixel circuit. The counting module is used for receiving the clock signal and the n-bit initial value signal and outputting 2 according to the clock signal and the initial value signal n And (3) target numerical signals, wherein n is a natural number greater than 1. The conversion module is used for receiving the first voltage signal, the second voltage signal and 2 n A target value signal, and according to the first voltage signal, the second voltage signal and 2 n A target value signal, output 2 n Target voltage signal, 2 n The target voltage signals form a step wave Sweep. Wherein 2 is n The largest target voltage signal among the target voltage signals is the first voltage signal, 2 n The smallest target voltage signal of the target voltage signals is the second voltage signal.
The clock signal adopted by the counting module is provided by a system clock, the system clock adopts a quartz crystal oscillator, the oscillation frequency error of the quartz crystal oscillator can be controlled within 50PPM, and the ns-level precision can be achieved in practical application. Therefore, when the counting module counts according to the clock signal, the turnover precision of the output target numerical value signal can reach the ns-level precision, and the turnover precision of the output target numerical value signal determines the level maintenance precision of the target voltage signal, so that the level maintenance precision of the target voltage signal can reach the ns-level precision.
The number of the target voltage signals can be changed rapidly by changing the bit numbers of the counting module and the conversion module, and then the voltage jump precision between the target voltage signals is adjusted.
The maximum value and the minimum value of the target voltage signals can be adjusted by adjusting the first voltage signal and the second voltage signal, so that the voltage jump precision between the target voltage signals is adjusted.
From the above, it can be seen that the step wave generating circuit provided by the embodiment of the utility model has the advantage of high precision, and can be applied to a pixel circuit.
It will be appreciated that the advantages of the second to third aspects may be found in the relevant description of the first aspect, and are not described in detail herein.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present utility model, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic circuit diagram of a conventional pixel circuit;
fig. 2 is a schematic diagram of a step wave applied in a pixel circuit;
FIG. 3 is a schematic block diagram of a ladder wave generating circuit according to an embodiment of the present utility model;
FIG. 4 is a schematic circuit diagram of a ladder wave generating circuit according to an embodiment of the present utility model;
FIG. 5 is a schematic circuit diagram of a ladder wave generating circuit according to another embodiment of the present utility model;
FIG. 6 is a schematic circuit diagram of a ladder wave generating circuit according to another embodiment of the present utility model;
FIG. 7 is a schematic diagram of a step wave generation process;
FIG. 8 is a schematic diagram of the counter in the ladder wave generating circuit according to one embodiment of the present utility model;
FIG. 9 is a schematic diagram of a ladder wave application generated by a ladder wave generating circuit according to an embodiment of the present utility model;
FIG. 10 is a schematic block diagram of the internal circuitry of a DAC in a ladder generating circuit according to an embodiment of the present utility model;
FIG. 11 is a functional block diagram of a pixel circuit according to an embodiment of the present utility model;
fig. 12 is a schematic block diagram of a pixel circuit according to another embodiment of the present utility model.
In the figure: 10. a pixel circuit; 11. a pixel module; 111. a PWM control unit; 12. a step wave generating circuit; 100. a counting module; 200. a conversion module; 300. a voltage follower module.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present utility model. It will be apparent, however, to one skilled in the art that the present utility model may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present utility model with unnecessary detail.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As used in the present description and the appended claims, the term "if" may be interpreted in context as "when …" or "upon" or "in response to a determination" or "in response to detection. Similarly, the phrase "if a determination" or "if a [ described condition or event ] is detected" may be interpreted in the context of meaning "upon determination" or "in response to determination" or "upon detection of a [ described condition or event ]" or "in response to detection of a [ described condition or event ]".
Furthermore, the terms "first," "second," "third," and the like in the description of the present specification and in the appended claims, are used for distinguishing between descriptions and not necessarily for indicating or implying a relative importance.
Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the utility model. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
In order to make the expression of the present utility model clearer, the principle of changing the voltage of the key node with time and further controlling the light emitting time of the Micro LED by adopting a mode of combining a step wave and capacitive coupling with the pixel circuit shown in fig. 1 is described below. It should be noted that the pixel circuit shown in fig. 1 is only an example, and the present utility model is not limited to the pixel circuit.
As shown in fig. 1, the switching transistor ts_sw is controlled to be turned on, the step wave Sweep outputs sweep_h, and referring to the waveform shown in fig. 2, the coupling capacitor C10 is coupled to the gate of the switching transistor t_pwm, so that the gate of the switching transistor t_pwm generates voltage vg_pwm, vg_pwm=data_pwm+vth+sweep_h, where data_pwm and Vth are information stored in the previous stage, vth is threshold compensation information, and data_pwm is written Data voltage information. The gate of the switching transistor t_pwm is a key node. Since the gate voltage vg_pwm of the switching transistor t_pwm is greater than the source voltage vdd_pwm thereof, the switching transistor t_pwm is turned off. The switching tubes T_ST1, T_ST2, T_EMI3 and T_EMI4 are controlled to be conducted. The grid voltage of the switch tube T_CC is data_PAM+Vth, which is smaller than the source voltage VDD_CGC, the switch tube T_CC is conducted and generates current, the current is obtained through a saturation region current formula, the prior art is omitted, the current flows through the Micro LED, and the Micro LED starts to emit light.
The step wave Sweep will gradually decrease stepwise over time, referring to the waveform shown in fig. 2. Since one end of the charge-discharge capacitor C20 maintains the Floating state flowing during the falling of the step wave Sweep, the change of the step wave Sweep is reflected on the other end of the charge-discharge capacitor C20, that is, the gate of the switching transistor t_pwm. Under the action of the step wave Sweep, the gate voltage vg_pwm of the switching tube t_pwm finally reaches data_pwm+vth+ (vdd_pwm-data_pwm), that is, the gate-source voltage vgs_pwm of the switching tube t_pwm reaches data_pwm+vth+ (vdd_pwm-data_pwm) -vdd_pwm=vth, so that the switching tube t_pwm starts to be turned on. At this time, the switching tubes t_st1, t_st2, t_emi3 and t_emi4 are still in the on state, so that the current in the switching tube t_pwm flows to the gate of the switching tube t_cc, the gate voltage of the switching tube t_cc is pulled up to vdd_pwm, the gate-source voltage of the switching tube t_cc is vdd_pwm-vdd_cgc, vdd_pwm-vdd_cgc-Vth >0, the off condition of the switching tube t_cc is satisfied, the switching tube t_cc is turned off, and the Micro LED stops emitting light. Light emission time=voltage holding time (Sweep-H- (VDD-PWM-Data-PWM))/step voltage of Micro LED, see fig. 2 for details. The specific waveform of the step wave Sweep is selected according to the pixel circuit, and the step wave Sweep may be a waveform that gradually rises stepwise with time.
From the above, it can be seen that the light emission time of the Micro LED is related to the step voltage and the voltage holding time of the step wave Sweep, wherein the accuracy of the voltage holding time (i.e., the level holding accuracy) has an effect on the Micro LED: the light-emitting time precision of each section of voltage control Micro LED can be affected. Influence of the precision of the step voltage (i.e., the voltage jump precision) on Micro LEDs: it can affect whether the Micro LED should emit light or stop emitting light.
From the above, it is clear that the accuracy of pulse width modulation can be satisfied when the step wave Sweep has an ultra-high level maintenance accuracy and voltage jump accuracy.
Since the related art generates a step wave with low accuracy by using the charge pump principle, the present utility model proposes a step wave generating circuit. As shown in fig. 3, the step wave generating circuit 12 is applied to the pixel circuit 10, the step wave generating circuit 12 includes a counting module 100 and a converting module 200, the counting module 100 is electrically connected to an input terminal of the converting module 200, and an output terminal of the converting module 200 is electrically connected to the pixel circuit 10.
Specifically, the counting module 100 is configured to receive the clock signal CP and the n-bit initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 And according to the clock signal CP and the initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Output 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 N is a natural number greater than 1. Wherein an initial value signal D of n bits 0 ,D 1 ,D 2 ,D 3 ,...D n-1 As binary value signal, an n-bit initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Each bit of the digital signal has two change states of 0 or 1, then the n-bit initial digital signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Will have 2 n State of change, so that the initial value signal D of n bits 0 ,D 1 ,D 2 ,D 3 ,...D n-1 At each rising edge of the clock signal CP, a change occurs, i.e. a set of target value signals Q are correspondingly output 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 Finally, at most output 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 。
The conversion module 200 is used for receiving the first voltage signal SweePH, the second voltage signal Sweepl and 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 And according to the first voltage signal SweePH, the second voltage signal Sweepl and 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 Output 2 n Target voltage signal, 2 n The target voltage signals form a step wave Sweep. Wherein 2 is n The largest target voltage signal among the target voltage signals is the first voltage signal SweePH,2 n The smallest target voltage signal among the target voltage signals is the second voltage signal sleepl.
Illustratively, when the counting module 100 is set to the self-decrementing mode, the counting module 100 is configured to generate the clock signal CP and the initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Output 2 n The target value signals Q are gradually decreased 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 . Wherein 2 is n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 The maximum target value signal Q of (2) 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 For the initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 。
The conversion module 200 is used for converting the first voltage signal SweePH, the second voltage signal Sweepl and 2 n The target value signals Q are gradually decreased 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 Output 2 n Target voltage signal decreasing in sequence, 2 n The successively decreasing target voltage signals form a step wave Sweep.
When the counting module 100 is set to the self-increment mode, the counting module 100 is used for generating a clock signal CP and an initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Output 2 n Sequentially increasing target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 . Wherein 2 is n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 The minimum target value signal Q of (1) 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 For the initial value signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 。
The conversion module 200 is used for converting the first voltage signal SweePH, the second voltage signal Sweepl and 2 n Each base is according toThe target value signal D of the secondary increment 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Output 2 n Target voltage signal 2 which increases in sequence n The sequentially increasing target voltage signals form a step wave Sweep.
It should be noted that, the clock signal CP adopted by the counting module 100 is provided by a system clock, the system clock adopts a quartz crystal oscillator, the oscillation frequency error of the quartz crystal oscillator can be controlled within 50PPM, and ns-level precision can be achieved in practical application. Therefore, when the counting module 100 counts according to the clock signal CP, the inversion accuracy of the output target value signal Q0-Qn-1 can reach the accuracy of ns level, and the inversion accuracy of the output target value signal Q0-Qn-1 determines the level maintenance accuracy of the target voltage signal, so that the level maintenance accuracy of the target voltage signal can reach the accuracy of ns level.
By changing the bit numbers of the counting module 100 and the converting module 200, the number change of the target voltage signals can be quickly realized, and the voltage jump precision between the target voltage signals can be further adjusted.
By adjusting the first voltage signal sleeph and the second voltage signal sleepl, the maximum value and the minimum value of the target voltage signal can be adjusted, and further the voltage jump precision between the target voltage signals can be adjusted.
From the above, it can be seen that the step wave generating circuit 12 provided in the embodiment of the present utility model has the advantage of high precision, and is suitable for the pixel circuit 10. The step wave Sweep generated by the step wave generating circuit 12 is transmitted to the pixel circuit 10, and the pixel circuit 10 adopts a mode of combining the step wave Sweep with capacitive coupling to change the voltage of the key node along with time so as to control the light emitting time of the Micro LED.
As shown in fig. 4, the counting module 100 is a counter, and the counter is electrically connected to an input terminal of the conversion module 200.
Specifically, n number of digital inputs of the counter are used for receiving n-bit initial digital signal D 0 ,D 1 ,D 2 ,D 3 ,...D n-1 The clock signal input end of the counter is used for receiving the clock signal CP, and the n number value output ends of the counter and the conversion moduleThe inputs of block 200 are electrically connected. The counter is used for counting the initial value signal D according to the clock signal CP and n bits 0 ,D 1 ,D 2 ,D 3 ,...D n-1 Output 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 。
As shown in fig. 4, the conversion module 200 is a DAC converter, an input terminal of the DAC converter is electrically connected to the counter, and an output terminal of the DAC converter is electrically connected to the pixel circuit. The number of bits of the counter is the same as that of the DAC converter, which means that the counter and the DAC converter are in matching relation, and the number of bits of the counter and the DAC converter are set to be the same, so that the cost of the ladder wave generating circuit can be reduced.
Specifically, n digital input ends of the DAC converter are electrically connected with n digital output ends of the counter and are used for receiving 2 output by the counter n The target value signals Q0-Qn-1. The first reference voltage terminal of the DAC converter is used for receiving the first voltage signal SweePH, and the second reference voltage terminal of the DAC converter is used for receiving the second voltage signal Sweepl. The DAC converter is used for converting the first voltage signal SweePH, the second voltage signal Sweepl and 2 n Target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 ,...Q n-1 Output 2 n Target voltage signal, 2 n The target voltage signals form a step wave Sweep. The DAC converter transmits the step wave Sweep to the pixel circuit 10, and the pixel circuit 10 adopts a mode of combining the step wave Sweep with capacitive coupling to change the voltage of the key node with time so as to control the light emitting time of the Micro LED.
The counter and the DAC converter are manufactured by IC technology. In order to further improve the accuracy and efficiency of the step wave generated by the step wave generating circuit 12, the counter and DAC converter in the present utility model may be integrated on the same circuit substrate.
As shown in fig. 5, the step wave Sweep generated by the step wave generating circuit 12 is applied to the pixel circuit 10, and in the process of transmitting the step wave Sweep to the pixel circuit 10, there are parasitic resistance RL and parasitic capacitance CL due to wiring on the substrate. To improve the load carrying capability of the conversion module 200, the step wave generation circuit 12 further includes a voltage follower module 300. An input terminal of the voltage follower block 300 is electrically connected to an output terminal of the conversion block 200, and an output terminal of the voltage follower block 300 is electrically connected to the pixel circuit 10.
Illustratively, as shown in FIG. 5, the voltage follower module 300 includes an operational amplifier OPAMP. The noninverting input terminal of the operational amplifier OPAMP is electrically connected to the conversion module 200, and the inverting input terminal of the operational amplifier OPAMP is electrically connected to the output terminal of the operational amplifier OPAMP and the pixel circuit 10, respectively. As can be seen from fig. 5, the noninverting input terminal of the operational amplifier OPAMP is electrically connected to the output terminal of the DAC converter in the conversion module 200.
The operational amplifier OPAMP is manufactured by an IC process.
In order to make the expression of the present utility model clearer, the generation process of the step wave Sweep will be specifically described below by taking a 4-bit counter and a 4-bit DAC converter as examples in conjunction with fig. 6 to 10.
First, the working principle and pin function of the counter will be described. The pin function of the counter is shown in table 1.
Table 1 pin function introduction table for counter
The counter is realized by adopting an IC process design, and a higher counter bit number can be realized by the counter realized by the IC process design; various functions (e.g., flexibly setting the maximum and minimum values of the counter) may also be implemented; and meanwhile, higher counting input clock frequency can be realized, so that better counting precision is realized.
The internal principle of the counter is shown in fig. 8, where the maximum/minimum registers: the maximum and minimum counter counts are stored according to the input value signal D and the Load signal. Zero clearing judgment: when the CE signal is high, the following module is adjusted, and the counter is directly enabled to output 0. Self-increasing and self-decreasing judgment: when the U/D signal is high level, the counter is in self-increasing mode, and conversely, in self-decreasing mode. Judging an initial value: the initial value is the minimum value in the self-increasing mode, and the initial value is the maximum value in the self-decreasing mode. Add 1/subtract 1: the 1 adding operation is realized in the self-increasing mode; the 1-reduction operation is realized in the self-reduction mode. A counter: a group of D triggers are adopted, a clock signal is CP, a reset signal is RSTN, an enabling signal is CEP, a result of adding 1/subtracting 1 to a preceding module is input, and a digital signal Q is output. End signal: and a D trigger is adopted, a clock signal is CP, a reset signal is RSTN, an input end is a result of adding 1/subtracting 1 to a preceding-stage module, whether the counter is counted is judged, and a TC signal is output.
The generation process of the step wave Sweep is then described with reference to fig. 6 and 7:
giving an initial value: the U/D signal is low and the counter is set to the self-subtracting mode. The Load signal is high at this time, and the initial value signal D is set at the rising edge of the clock signal CP 0 ,D 1 ,D 2 ,D 3 1111 imparts a target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 1111, DAC according to target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 1111 outputs the highest level, i.e., the first voltage signal sleeph, which is amplified by the operational amplifier OPAMP and then transmitted to the pixel circuit 10.
Starting counting: the CEP signal is high, the rising edge of the clock signal CP is coming, the subtraction is started, the target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 Change to 0111, target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 Is fed back to the DAC converter, which outputs the next highest level. Typically, adjacent bit output voltage differences of DAC convertersWhere v=sleeph-sleepl, represents the maximum voltage range of the output.
Counting is finished: target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 When the voltage is 0000, the DAC converter outputs the second voltage signal Sweepl at the lowest level, and the second voltage signal Sweepl passes through the operational amplifierOPAMP is amplified and transferred to the pixel circuit 10. At this time, the counter counts up, the CEP signal goes low, the counting stops, and the target value signal Q 0 ,Q 1 ,Q 2 ,Q 3 The low level is maintained. The above is the process of generating the step wave Sweep.
It should be noted that, when the counter is set in the self-increasing mode, the step wave Sweep is generated in a similar process to that when the counter is set in the self-decreasing mode, and will not be described here again.
In practical application, the maximum value and the minimum value of the counter can be flexibly set according to practical requirements so as to realize the control of the light emission of a certain section of gray scale. Taking 8Bit display Gray scale as an example as shown in fig. 9, when the full Sweep function is realized using the step wave Sweep, the required Sweep time is the time from Gray0 to Gray255 as shown in (a) of fig. 9. However, not every gray level is actually emitting in the display screen, for example, only 0 to 127 gray levels of the current display screen are emitting, so that the scanned 127 to 255 gray levels are not emitting in the display screen, and therefore, the scanning time is wasted. At this time, the partial Sweep function may be realized by using the step wave Sweep, and only the maximum value and the minimum value of the counter need be set, as shown in (b) of fig. 9. The partial scanning function can scan only a part of the step signals, for example, the (b) in fig. 9 scans only the gray scales 0 to 127, so that the number of steps scanned can be reduced, and the luminous efficiency is improved.
Finally, taking the DAC converter as a resistor type DAC as an example, the working principle of the DAC converter is explained. It should be noted that the present utility model is not limited to the type of DAC converter.
The resistive DAC is implemented by using an IC process design, and as shown in fig. 10, since the ladder wave generating circuit of the present utility model is applied to the display field, it is required to operate at different operating voltages. The leftmost vref_l and vref_h in fig. 10 may determine the number and voltage ranges according to actual needs, such as the high-low voltage range of the common data voltage signal and the high-low voltage range of the step wave Sweep. Such as when state 1: VREF_L <1> and VREF_H <1> are voltage ranges for the data voltage signal. When state 2: VREF_L <2> and VREF_H2 > are voltage ranges of the step wave sleeps, wherein VREF_H <2> corresponds to sleepH and VREF_L <2> corresponds to sleepL. In general, the data voltage signal and the step wave Sweep are not simultaneously effective in the AM Micro LED display device, and thus the multiplexing DAC converter can be implemented with such a design, thereby reducing the chip area.
The multi-path selector in the resistance DAC adopts 2Bit selectors to form 4Bit selectors through cascade connection, and the specific working flow is as follows:
to input binary data S3 to S0:1110, V14 is selected as an illustration. Both bits of S3S2 are 1, so through 2Bit high selection, 11XX units are selected to be output. In the 11XX cell, there are four level outputs V15 to V12, and since the lower two bits S1S0 of the input are 10, the gate control bit of V14 is XS1S0 in the lower two bit PMOS select cell, and therefore in the corresponding lower two bit NMOS select cell in the V14 PMOS select cell, the gate control bit of V14 is S1XS0, V14 is selected.
In the 11XX unit, the other lower two gate control bits are different from V14, and there is no case where two reference levels are selected at the same time, so V14 is output as the output of the 4Bit selector to the non-inverting input terminal of the operational amplifier OPAMP. The above is the working principle of a resistive DAC.
As shown in fig. 11, the embodiment of the present utility model further provides a pixel circuit 10, which includes a pixel module 11 and the above-described step wave generating circuit 12. The conversion module in the step wave generation circuit 12 is electrically connected with the pixel module 11, and is used for converting 2 n The respective target voltage signals are sequentially supplied to the pixel modules 11.
As shown in fig. 12, the pixel module 11 includes a PWM control unit 111. The PWM control unit 111 is electrically connected to the conversion module in the step wave generation circuit 12 for generating a step wave according to 2 n The individual target voltage signals control the light emission time of Micro LEDs in the pixel module 11.
The embodiment of the utility model also provides a display device which comprises the pixel circuit.
The above embodiments are only for illustrating the technical solution of the present utility model, and not for limiting the same; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present utility model, and are intended to be included in the scope of the present utility model.

Claims (10)

1. A step wave generating circuit applied to a pixel circuit, comprising:
a counting module for receiving a clock signal and an n-bit initial value signal and outputting 2 according to the clock signal and the initial value signal n The number of target numerical signals, n is a natural number greater than 1;
the input end of the conversion module is electrically connected with the counting module, the output end of the conversion module is electrically connected with the pixel circuit, and the conversion module is used for receiving a first voltage signal, a second voltage signal and 2 n The target value signal is calculated according to the first voltage signal, the second voltage signal and 2 n Outputting 2 from the target value signal n Target voltage signal, 2 n The largest of the target voltage signals is the first voltage signal, 2 n The smallest of the target voltage signals is the second voltage signal.
2. The step wave generation circuit of claim 1, wherein the counting module comprises a counter electrically connected to an input of the conversion module.
3. The step wave generation circuit of claim 2, wherein the conversion module is a DAC converter, an input of the DAC converter is electrically connected to the counter, and an output of the DAC converter is electrically connected to the pixel circuit.
4. The step wave generation circuit of claim 3, wherein the number of bits of the counter is the same as the number of bits of the DAC converter.
5. The step wave generation circuit of claim 3, wherein the counter and the DAC converter are fabricated using an IC process.
6. The step wave generation circuit according to any one of claims 1 to 5, characterized in that the step wave generation circuit further comprises:
the voltage following module, the input of voltage following module with the output electricity of conversion module is connected, the output of voltage following module be used for with pixel circuit electricity is connected, the voltage following module is used for improving conversion module's load capacity.
7. The step wave generation circuit of claim 6, wherein the voltage follower module comprises an operational amplifier, a non-inverting input of the operational amplifier being electrically connected to the output of the conversion module, and an inverting input of the operational amplifier being electrically connected to the output of the operational amplifier and the pixel circuit, respectively.
8. A pixel circuit comprising a pixel module and the step wave generating circuit according to any one of claims 1 to 7; a conversion module in the step wave generation circuit is electrically connected with the pixel module, and the conversion module is used for converting 2 n The target voltage signals are sequentially transmitted to the pixel modules.
9. The pixel circuit of claim 8, wherein the pixel module comprises a PWM control unit; the PWM control unit is electrically connected with the conversion module in the ladder wave generation circuit and is used for controlling the voltage according to 2 n Each of the target voltage signal control stationsAnd the light-emitting time of the Micro LEDs in the pixel module.
10. A display device comprising the pixel circuit according to any one of claims 8 to 9.
CN202320316503.4U 2023-02-24 2023-02-24 Step wave generating circuit, pixel circuit and display device Active CN219643890U (en)

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Application Number Priority Date Filing Date Title
CN202320316503.4U CN219643890U (en) 2023-02-24 2023-02-24 Step wave generating circuit, pixel circuit and display device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202320316503.4U CN219643890U (en) 2023-02-24 2023-02-24 Step wave generating circuit, pixel circuit and display device

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CN219643890U true CN219643890U (en) 2023-09-05

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