CN203013214U

CN203013214U - LED display large-screen high-speed scanning controller

Info

Publication number: CN203013214U
Application number: CN2012207003505U
Authority: CN
Inventors: 乔红瑗; 杨晓鹏; 谢维奇; 丁佳卿
Original assignee: SHANGHAI DOUBLE MICROELECTRONICS CO Ltd
Current assignee: SHANGHAI DOUBLE MICROELECTRONICS CO Ltd
Priority date: 2012-12-17
Filing date: 2012-12-17
Publication date: 2013-06-19
Anticipated expiration: 2022-12-17

Abstract

The utility model discloses an LED display large-screen high-speed scanning controller. The controller comprises an LED large-screen driving chip, a decoder, and a controllable high-speed discharging circuit, wherein the LED large-screen driving chip is connected with the decoder, the decoder decodes a control signal, and is connected with a switch tube which acts as a power supply switch, the switch tube controls the voltage of a plurality of rows of light emitting diodes, and the controllable high-speed discharging circuit discharges electricity to an output end when the switch tube is turned off. According to the LED display large-screen high-speed scanning controller, the time for outputting a falling edge by a scanning line can achieve one microsecond, controllable discharging is performed on a row scanning line in the utility model, and the output end can be controlled to be in a state of high resistance after discharging. A trailing phenomenon is eliminated, the refreshing rate is improved, and influence brought by electric leakage and open circuit of the lighting emitting diodes is eliminated.

Description

LED shows giant-screen high-velocity scanning controller

Technical field

The utility model relates to LED large screen display field.

Background technology

LED display can be divided into again static screen and scan screen.The R/G/BLED that so-called static screen is exactly each picture element has an independently control end.Image whole screen in a frame is to show simultaneously.And so-called scan screen refers to that a few row R/G/B LED share a control end, and these several row are powered by sequential again and reached the purpose that shows complete image.Give an example: take 1/4 scanning as example, first a frame time is divided into 4 parts, first shows the first row at 0-1/4 in the time, 1/4-2/4 just shows the second row in the time, by that analogy.Clearly, in this case, image is not that whole screen shows simultaneously in a frame, shows that first 1/4 image shows another 1/4 image again, has just shown complete image after 4 1/4.The power consumption that is understood that 1/4 scan screen under the equal peak point current of R/G/B LED only is 1/4 of the static screen in front.Certainly the brightness of this moment also only is the former 1/4.But scan screen so its constant-current control circuit will greatly reduce, becomes the utility model also just to decrease because multirow shares one road control end

Scan pattern, its application principle figure sees Fig. 1.In Fig. 1,138 is that 38 code translators are decoded as control signal to double-wire signal, and as shown in Figure 8, the Pmos pipe is controlled V1 ~ V4 voltage as power switch.Fig. 1 is one the 1/4 LED display schematic diagram of sweeping.Its principle of work is that every row power supply V1-V4 opens time of 1/4 by controlling requirement in 1 two field picture.The advantage of doing like this is can more effectively utilize the display characteristic of LED and reduce the hardware cost utility model.Its shortcoming is exactly in 1 two field picture, and every row LED can only show for 1/4 time.As: when frame frequency was 50Hz, the displaying time of every row was Tm=1000/(50 * 4)=5ms.If adopt higher frame frequency or scanning progression further to increase, that displaying time will be shorter, as the 50Hz frame frequency, and during 1/16 scanning, Tm=1.25ms.Along with shortening of Tm, the normal operation of the product confrontation system of rising, the negative edge of row power supply wave shape will be just vital.

The principle of work of scanning display screen has been told about in the front, and Fig. 2 is the ideal waveform figure of 1/4 scan line power supply.Yet its waveform and desirable differing greatly in actual applications.Fig. 3 is the oscillogram that adopts the Pmos pipe to control as the row power switch.When turn-offing due to Pmos pipe its output be in tri-state state and the out-put supply line (V1～v4) and LED lamp stray capacitance exist the voltage on power lead can not reduce at once, and its negative edge Tf will be greater than 100 microseconds.If ignore capable power supply rising time (in fact, very short can ignoring of the time of rising edge), be not difficult to find out, in 1 two field picture, previous row and rear delegation can have an appointment overlapping time of 100 microseconds.For ease of analytical calculation, we can be approximately Tn overlapping time negative edge time T f.That is: Tn=Tf.So, in the time of should showing the second row, previous row still can be luminous with the control mode of the second row in a period of time at Tn, will see that in our vision previous row is in glimmer.The size of brightness is directly proportional to the ratio of displaying time to two row overlapping time, namely is directly proportional to Tn/Tm.Here we definition of T n/Tm is overlap ratio, also take the 50Hz frame frequency as example, and Tn/Tm=0.1/(1000/(4 * 50))=2%.It seems that 2% overlap ratio is not also very large.But along with the raising of frame frequency or its overlap ratio of raising Tn/Tm of scanning progression will increase greatly.

Below we might as well bring up to 250Hz to frame frequency and have a look at, this moment row power switch control waveform figure such as Fig. 3.Obviously, the overlap ratio of this moment reaches Tn/Tm=0.1/ (1000/ (4 * 250))=10%.Under so high overlap ratio, conditions of streaking will be fairly obvious.

Therefore, existing LED scanning giant-screen is managed switch by Pmos and is realized scanning display mode, when turn-offing due to PMOS, power lead is in tri-state state and can reduce because there is the voltage on power lead in stray capacitance at once, may cause showing when next frame wrong (conditions of streaking).

In order to have added various blanking circuits in the frame frequency application that improves scanning in every horizontal scanning line, traditional blanking circuit can improve the scanning frame frequency to a certain extent.But this has brought again new problem, because service time is elongated, temperature raises, the variety of issues such as LED quality, and the reverse leakage that has the LED light emitting diode becomes large.Thereby as traditional blanking circuit after form loop of electric leakage cause should not be luminous pixel light become bright spot by stain, array brightens and brings so-called caterpillar problem under dark state.Take the D14 electric leakage as example, if under normal circumstances when scan V2 when capable V2 be that the pixel at high level D24 place is for black.This moment LED giant-screen drive IC 4 ends be high-impedance state, so and the voltage breakdown of light emitting diode greater than not having electric current D24 not work in operating voltage D24.If should be a variety of causes, D14 this moment cause reverse leakage to become the large larger leakage current (greater than 1uA) that produces in operating voltage range.Form loop of electric leakage shown in dotted lines in Figure 1 this moment for D24 so, caused having produced in D24 electric current.In like manner the 4th column array all exists same problem D34, D44 all can shinnyly cause the demonstration mistake.

Summary of the invention

The technical problems to be solved in the utility model is, provides a kind of LED to show giant-screen high-velocity scanning controller, and it can effectively be eliminated conditions of streaking and improve refresh rate, eliminates the impact that comes because of the light emitting diode electric leakage.

For solving above technical matters, the utility model provides a kind of LED to show giant-screen high-velocity scanning controller, and comprising: the LED giant-screen drives chip, and the LED giant-screen drives chip and connects code translator; The code translator decoding control signal, code translator connects the switching tube as power switch, the supply voltage of switch controlled LED; Controlled high rate discharge circuit discharges to output terminal when switching tube turn-offs.

The beneficial effects of the utility model are: sweep trace output negative edge can reach about a microsecond, and the utility model horizontal scanning line is carried out controlled discharge, and after discharge, output terminal can be controlled to be high-impedance state.Eliminate conditions of streaking and improve refresh rate, eliminate the impact that comes because of the light emitting diode electric leakage.

Described controllable discharge circuit can the controlled discharge level; The range of control of discharge level is that Vdd-1V is to VDD-2V.

Described controlled high rate discharge circuit can be set to high-impedance state to output after discharge finishes.

Described controllable discharge circuit controlled discharge level is Vdd-1.4V.

Described switching tube is Pmos or Nmos switching tube.

Also comprise the overcurrent and overheating protection circuit.

The described controlled high rate discharge circuit discharging time is less than 1 microsecond.

Description of drawings

Below in conjunction with drawings and Examples, the utility model is described in further detail.

Fig. 1 coordinates traditional blanking mode application principle figure for existing scan pattern;

Fig. 2 is the oscillogram that the existing Pmos of employing pipe is controlled as the row power switch;

Row power switch control waveform figure when Fig. 3 is existing frame frequency 250Hz;

Fig. 4 is power switch control waveform described in the utility model, blanking control of discharge waveform, power switch output waveform;

Fig. 5 is power switch circuit block diagram described in the utility model;

Fig. 6 is existing product power switch internal frame diagram.

Fig. 7 is the controllable discharge circuit block diagram.

Embodiment

As shown in Figure 5, LED described in the utility model shows giant-screen high-velocity scanning controller, comprising: the LED giant-screen drives chip, and the LED giant-screen drives chip and connects code translator; The code translator decoding control signal, code translator connects the switching tube as power switch, switch controlled several rows LED voltage; Controlled high rate discharge circuit discharges to output terminal when switching tube turn-offs.

Described controllable discharge circuit can the controlled discharge level; The range of control of discharge level be Vdd-1V to VDD-2V, preferred, controllable discharge circuit controlled discharge level is Vdd-1.4V.

The described controlled high rate discharge circuit discharging time, the whole output that stops after time of arrival discharging can be set to high-impedance state less than 10 microseconds.Preferably, the described controlled high rate discharge circuit discharging time is less than 1 microsecond.

Because service time is elongated, temperature raises, the variety of issues such as LED quality, the reverse leakage that has the LED light emitting diode becomes large, forming loop of electric leakage as after traditional blanking circuit, thereby cause should not be luminous pixel light become bright spot by stain, array brightens and brings so-called caterpillar problem under dark state.The D14 electric leakage is as example in Fig. 1, under normal circumstances when scanning V2 when capable, if V2 is that the pixel at high level D24 place is for black.This moment LED giant-screen drive IC 4 ends be high-impedance state, so and the voltage breakdown of light emitting diode greater than not having electric current D24 not work in operating voltage D24.If should be a variety of causes, D14 this moment cause reverse leakage to become the large larger leakage current (greater than 1uA) that produces in operating voltage range.Form loop of electric leakage shown in dotted lines in Figure 1 this moment for D24 so, caused having produced in D24 electric current.In like manner the 4th column array all exists same problem D34, D44 all can shinnyly cause the demonstration mistake.In order to solve smear problem, increase the high speed pull-down circuit when the PMos switching tube turn-offs, output level has been pulled down to 0, but produced simultaneously short circuit caterpillar problem, next controlling drop-down level closes at Pmos and has no progeny, control drop-down level and make more than drop-down level is controlled at VDD-1.4V, when V2 was output as 5V like this, V1 was 3.6V, V2-V1 is 1.4V, less than the Vf forward conduction voltage of D24, so being the lamps such as D24, this all can't give out light, solved the electric leakage caterpillar.

But because the Vx high level is 5V, low level is 3.6V, in case D14, D34, D44 can be bright when the V2 high level for the D24 open circuit, forms open circuit caterpillar problem.The utility model solution be pull down to Vdd-1.4v lasting drop-down to change pulse into drop-down, output is set to high-impedance state after pulling down to VDD-1.4 at once, caterpillar state a little less than atomic can reduce to open a way this moment.

The utility model increases blanking control circuit and utilizes input control signal to produce the pulse pulldown signal, namely closes to have no progeny at the Pmos switching tube to generate a very short drop-down pulse of time, and dragging down rapidly the low output terminal of power switch is the VX terminal voltage at once.

The utility model also increases the overcurrent and overheating protection circuit.

The utility model also comprises the high speed pull-down circuit as shown in Figure 7, pull-down circuit is by a 1.4VDC voltage source to VDD, operational amplifier OPamp and a gate-controlled switch Q1 who is used for high-speed driving forms. and operational amplifier is connected to voltage follower structure, its input end connects the dc voltage source output terminal and is connected to output terminal by switch Q1, and Q1 is connected to blanking circuit and produces.When Pmos switching tube input end has cut-off signals, blanking circuit can produce a blanking discharge pulse signal, the high level of this pulse signal can be opened the Q1 pipe, output terminal is discharged in the time at this high level pulse, so after the pulse step-down Q1 switching tube turn-off due to this moment Pmos open the light and also be in off state output this moment and be set to high-impedance state, output voltage is the output voltage of operational amplifier.

The utility model is not limited to embodiment discussed above.Above description to embodiment is intended in order to describe and illustrate the technical scheme that the utility model relates to.Based on the apparent conversion of the utility model enlightenment or substitute and also should be considered to fall into protection domain of the present utility model.Above embodiment is used for disclosing best implementation method of the present utility model, so that the those of ordinary skill in the utility model field can be used numerous embodiments of the present utility model and multiple alternative reaches the purpose of this utility model.

Claims

1. a LED shows giant-screen high-velocity scanning controller, it is characterized in that, comprising:

The LED giant-screen drives chip, and the LED giant-screen drives chip and connects code translator;

The code translator decoding control signal, code translator connects the switching tube as power switch, the supply voltage of switch controlled LED;

Controlled high rate discharge circuit discharges to output terminal when switching tube turn-offs.

2. LED as claimed in claim 1 shows giant-screen high-velocity scanning controller, it is characterized in that, described controllable discharge circuit can the controlled discharge level; The range of control of discharge level is that Vdd-1V is to VDD-2V.

3. LED as claimed in claim 2 shows giant-screen high-velocity scanning controller, it is characterized in that, described controlled high rate discharge circuit can be set to high-impedance state to output after discharge finishes.

4. LED as claimed in claim 3 shows giant-screen high-velocity scanning controller, it is characterized in that, described controllable discharge circuit controlled discharge level is Vdd-1.4V.

5. LED as claimed in claim 3 shows giant-screen high-velocity scanning controller, it is characterized in that, described switching tube is Pmos or Nmos switching tube.

6. LED as claimed in claim 3 shows giant-screen high-velocity scanning controller, it is characterized in that, also comprises the overcurrent and overheating protection circuit.

7. LED as claimed in claim 3 shows giant-screen high-velocity scanning controller, it is characterized in that, the described controlled high rate discharge circuit discharging time is less than 1 microsecond.