A kind of μ LED pixel drive circuit system and driving methodTechnical field
The present invention relates to a kind of driving circuit technical fields, and in particular to a kind of μ LED pixel drive circuit system and drivingMethod.
Background technique
LED drive power is the power adapter that power supply supply is converted to specific voltage and current to drive LED luminous.The most of constant current sources for that can change and change voltage with LED forward drop value of the output of LED drive power.Driving methodThere are two types of passages, one is a constant pressure source supplies multiple constant-current sources, each constant-current source individually gives every paths of LEDs to power.This combinationMode is flexible, when LED failure all the way, does not influence the work of other LED.
Driving method has constant current mode, type voltage regulation, pulsed drive etc..The electric current of constant-current drive circuit output is constant, andThe DC voltage of output but changes with load the of different sizes of resistance value in a certain range, and load resistance value is small, and output voltage is justLow, load resistance value is big, and output voltage is just high；It is ideal that constant-current drive circuit, which drives LED,.Type voltage regulation driving, works as pressure stabilizingAfter parameters in circuit determine, when voltage of output, is fixed, and the electric current exported becomes with the increase and decrease of loadChange.Pulsed drive, many LED applications require to dim with dimming function such as LED backlight or architectural lighting.By adjustingDimming function may be implemented in the brightness and contrast of LED.Perhaps, the electric current for reducing device, which can shine to LED, to be adjusted, stillAllowing LED to work lower than rated current will cause many adverse consequences, such as color difference problem.Replace simple electric current tuneWhole method is integrated pulse width modulation (PWM) controller in LED driver.The signal of PWM is not used directly for control LED,But one switch of control, such as a MOSFET, thus electric current needed for being provided to LED.PWM controller is usually centainly being fixedIt works in frequency, and pulsewidth is adjusted, to match required duty ratio.Current most of LED chips are all come using PWMIt controls LED to shine, in order to ensure people will not feel significantly to flash, the frequency of pwm pulse has to be larger than 100HZ.PWM controlMajor advantage be it is more accurate by the light modulation electric current of PWM, farthest reduce LED shine when color difference.
Based on above-mentioned several driving methods, according to LED current and voltage feature, it is usually desirable to it is driven using constant current,It is avoided that the change of LED forward voltage and cause current variation, constant current keeps the brightness of LED more stable.
Furthermore it is more that LED drives IC gray scale to adjust type, including weight extinguishes method, weight lights method and synthesis etc..PowerIt is the gradation data 8 parallel delivery outlets that value, which lights method, programs serial transmission, lights LED etc. in turn.Fixed cycle, butIt is that holding time is long.It is that clock is reduced to 23 clocks completions that weight, which extinguishes method, greatly reduces MCU single-chip microcontroller work load,But OE pulse will be gone strictly, if there is tasks interrupt, meeting stroboscopic, brightness is also very low.PWM technology includes phase voltage controlPWM, pulsewidth PWM method, random PWM, SPWM method, line voltage control PWM etc..Wherein, pulsewidth PWM is that each pulse width is homogeneousDeng pulse be classified as PWM waveform, change spike train period with frequency modulation, can change pulse width or duty ratio can with pressure regulation,Voltage and frequency coordination can be made to change using suitable control method.It can reach by adjusting the duty ratio of PWM cycle, PWMControl the purpose of charging current.Software is generallyd use to control the electric current of PWM.
However, the current control accuracy of the above method is low, and brings nothing since the speed of software adjustment PWM is slowMethod controls the problem of charging current, causes the LED switch time that can not effectively control.If using pure hardware controls, hardwarePrice is more expensive, and the display picture contrast frequently resulted in is undesirable.
Therefore, research how effectively control the LED switch time come improve show picture contrast be highly important.
Summary of the invention
In order to overcome the above problems, the present invention is intended to provide a kind of μ LED pixel drive circuit system, simplifies the control of PWM gray scaleThe generating process of signal processed effectively controls the switch time of LED.
In order to achieve the above object, the present invention provides a kind of μ LED pixel drive circuit systems, including；
Driving switch unit, one end are electrically connected with μ LED phase, for controlling opening or closing for μ LED；
SRAM memory cell is mutually electrically connected with the other end of driving switch unit, for storing and to driving switch unitOutput gray level signal；
Trombone slide in gray-scale Control is mutually electrically connected with SRAM memory cell, driving switch, for controlling opening for driving switch unitIt opens or the shut-in time.
Preferably, trombone slide is trombone slide on PMOS in the gray-scale Control.
Preferably, the driving switch unit uses MOS driving switch pipe.
Preferably, the driving switch unit uses PMOS driving switch pipe.
Preferably, the SRAM memory cell, trombone slide is commonly connected to the driving switch unit in the gray-scale ControlGrid.
Preferably, the SRAM memory cell, trombone slide, the grid of the driving switch unit are common in the gray-scale ControlIt is connected to a voltage node (VDR), the voltage of voltage node (VDR) is stored single by trombone slide in the gray-scale Control and the SRAMMember codetermines.
Preferably, the source electrode of trombone slide connects logical circuit power (VDDD) in the gray-scale Control, and grid meets enable end (RN),Drain electrode meets the voltage node (VDR).
Preferably, the source electrode of the driving switch pipe connects pixel circuit power supply (VDDP), and drain electrode connects the anode tap of μ LED.
In order to achieve the above object, the present invention also provides a kind of using above-mentioned μ LED pixel drive circuit system progressThe method of pixel driver, comprising:
Trombone slide is connected in the gray-scale Control, the shutdown of driving switch unit, and SRAM memory cell is defeated to driving switch unitGrey scale signal out is invalid；
Trombone slide turns off in the gray-scale Control, the conducting of driving switch unit, and SRAM memory cell is defeated to driving switch unitGrey scale signal out is effective.
In some embodiments, trombone slide input low level in Xiang Suoshu gray-scale Control, trombone slide conducting in the gray-scale Control；The trombone slide input high level in the gray-scale Control, trombone slide shutdown in the gray-scale Control.
Preferably, the gray scale control is controlled by the square-wave signal connecting with the grid of trombone slide in the gray-scale ControlThe on or off of trombone slide in system.
Preferably, trombone slide and the SRAM memory cell are commonly connected to a voltage node (VDR) in the gray-scale Control,Trombone slide and the SRAM memory cell codetermine the voltage of voltage node (VDR) in the gray-scale Control, to determine to driveThe grid voltage of switch unit.
Preferably, the SRAM memory cell uses 8-bit pixel grey scale digital signal, the primary ash for only exporting 1-bitDegree evidence arrives driving switch unit.
Preferably, according to the different weights of 8-bit pixel grey scale digital signal, to control trombone slide in the gray-scale ControlOn or off, to control the on or off time of the driving switch unit.
μ LED pixel drive circuit system of the invention controls opening or closing for μ LED by setting driving switch,SRAM memory cell storage and to driving switch unit output gray level signal, trombone slide controls driving switch list in gray-scale ControlThe switch time of member has efficiently controlled the switch time of LED, has mentioned to simplify the generating process of PWM gray-scale Control signalThe high contrast of display picture.Further, pixel grey scale digital signal is 8-bit pixel grey scale digital signal, passes through 8-The different weights of bit pixel grey scale digital signal, to reach the different duration, the further comparison for improving display pictureDegree.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of the μ LED pixel drive circuit system of one embodiment of the present of invention
Specific embodiment
To keep the contents of the present invention more clear and easy to understand, below in conjunction with Figure of description, the contents of the present invention are made into oneWalk explanation.Certainly the invention is not limited to the specific embodiment, general replacement known to those skilled in the artIt is included within the scope of protection of the present invention.
μ LED pixel drive circuit system of the invention, including driving switch unit, SRAM memory cell and gray-scale ControlUpper trombone slide.Wherein, driving switch unit one end is electrically connected with μ LED phase, for controlling opening or closing for μ LED；SRAM storage is singleMember is mutually electrically connected with the other end of driving switch unit, for storage and to driving switch unit output gray level signal；Gray scale controlTrombone slide is mutually electrically connected with SRAM memory cell, driving switch in system, opens or closes the time for control driving switch unit.
Below in conjunction with attached drawing 1 and specific embodiment, invention is further described in detail.It should be noted that attached drawing is adoptedWith very simplified form, using non-accurate ratio, and only to it is convenient, clearly reach and aid in illustrating the mesh of the present embodiment's.
Referring to Fig. 1, trombone slide 03 can be using trombone slide on PMOS, certainly in other realities in gray-scale Control in the present embodimentIt applies in example, it can also be using trombone slide on NMOS.Driving switch unit 01 can use MOS driving switch pipe, preferably, usingPMOS driving switch pipe.
As shown in Figure 1, trombone slide 03 is commonly connected to the grid of driving switch unit 01 in SRAM memory cell 02, gray-scale ControlPole, specifically, the grid of trombone slide 03 in SRAM memory cell 02, gray-scale Control, driving switch unit 01 is commonly connected to an electricityNode VDR is pressed, the voltage of voltage node VDR is codetermined by trombone slide 03 in gray-scale Control and SRAM memory cell 02.
Here, the source electrode of trombone slide 03 connects the end VDDD (logical circuit power) in gray-scale Control, and grid meets enable end RN, outputSquare-wave signal, drain electrode meet voltage node VDR.And the source electrode of driving switch unit 01 meets pixel circuit power vd DP, drain electrode connectsThe anode tap VAN of LED.
About SRAM memory cell 02 can using conventional SRAM memory cell structure, such as comprising SRAM memory,Ramp generator, comparator, signal output device etc..This is all that those skilled in the art could be aware which is not described herein again.ThisIn, multiple metal-oxide-semiconductors are used in SRAM memory cell 02, VSSD is low level digital signal end, is equivalent to GND；BL is data bit,WL is row control signal.
Include: using the method that the μ LED pixel drive circuit system of the present embodiment carries out pixel driver
Trombone slide 03 is connected in gray-scale Control, and driving switch unit 01 turns off, and SRAM memory cell 02 is to driving switch unitThe grey scale signal of 01 output is invalid；Specifically, since trombone slide 03 is using PMOS tube in gray-scale Control, when the trombone slide in gray-scale ControlWhen 03 input low level, trombone slide 03 is connected in gray-scale Control.Here it is possible to control gray-scale Control pull-up by square-wave signalThe on or off of pipe 03.
Trombone slide 03 turns off in gray-scale Control, and driving switch unit 01 is connected, and SRAM memory cell 02 is to driving switch unitThe grey scale signal of 01 output is effective.Specifically, when 03 input high level of trombone slide in gray-scale Control, trombone slide 03 in gray-scale ControlShutdown.
Here, the grid voltage of driving switch unit 01 is determined jointly by trombone slide 03 in gray-scale Control and SRAM memory cell 02It is fixed.Since trombone slide 03 in gray-scale Control and SRAM memory cell 02 are commonly connected to a voltage node VDR, trombone slide in gray-scale ControlThe voltage of 03 and the co-determination of SRAM memory cell 02 voltage node VDR.
In the present embodiment, SRAM memory cell 02 uses 8-bit pixel grey scale digital signal, primary only output 1-bit'sGradation data is to driving switch unit 01.Therefore, according to the different weights of 8-bit pixel grey scale digital signal, to control gray scaleThe on or off of trombone slide 03 in control is shown to control the on or off time of driving switch unit 01 with reaching to improveShow the effect of picture contrast.
In conclusion the present invention controls opening or closing for μ LED by setting driving switch, SRAM memory cell is depositedIt storing up and to driving switch unit output gray level signal, trombone slide controls switch time of driving switch unit in gray-scale Control,To simplify the generating process of PWM gray-scale Control signal, the switch time of μ LED is efficiently controlled, display picture is improvedContrast.Further, pixel grey scale digital signal is 8-bit pixel grey scale digital signal, passes through 8-bit pixel grey scale numberThe different weights of word signal improve the contrast of display picture to reach the different duration.
Although the present invention is disclosed as above with preferred embodiment, the right embodiment illustrate only for the purposes of explanation and, it is not intended to limit the invention, if those skilled in the art can make without departing from the spirit and scope of the present inventionDry changes and retouches, and the protection scope that the present invention is advocated should be subject to described in claims.