CN202855257U - High-speed blanking LED large-screen scanning monitor - Google Patents

Abstract

The utility model discloses a high-speed blanking LED large-screen scanning monitor which comprises a LED large-screen driver chip connected with a decoder and the decoder used to decode signals into control signals. The decoder is connected to be used as a double Pmos pipe of a power switch. The double Pmos pipe controls LED voltage of several rows of luminous diodes. The double Pmos pipe circuit comprises a voltage pull-down circuit. According to the utility model, scanning line output falling edge can reach about 1 microsecond, trailing phenomenon is eliminated, refresh rate is raised, and influence caused by electric leakage of the luminous diodes is eliminated.

Description

High-speed blanking LED giant-screen scanning monitor

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 reach the purpose that shows complete image by the sequential power supply again.Give an example: take 1/4 scanning as example, first a frame time is divided into 4 parts, shows first the first row in the time at 0-1/4,1/4-2/4 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 in addition 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 is because multirow shares one road control end, so its constant-current control circuit will greatly reduce, cost also just decreases

Scan pattern, its application principle figure sees Fig. 1.138 is that 38 code translators are decoded as control signal to double-wire signal among Fig. 1, and as shown in Figure 8, two Pmos switching tubes are 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 the control requirement in 1 two field picture.The advantage of doing like this is can more effectively utilize the display characteristic of LED and reduce hardware cost.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, such as the 50Hz frame frequency, and during 1/16 scanning, Tm=1.25ms.Along with shortening of Tm, the normal operation of the rising of row power supply wave shape, the product confrontation system of negative edge just will be 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 in actual applications its waveform and desirable differing greatly.Fig. 3 adopts two Pmos switching tubes as the oscillogram of row power switch control.Since when two Pmos switching tubes turn-off its output be in tri-state state and the out-put supply line (V1 ~ v4) and LED lamp stray capacitance exist the voltage on the power lead can not reduce at once, and its negative edge Tf will be greater than 100 μ s.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 that in 1 two field picture, previous row and rear delegation can have an appointment overlapping time of 100 μ s.For ease of analytical calculation, we can be approximately Tn overlapping time negative edge time T f.That is: Tn=Tf.

So, previous row still can be luminous with the control mode of the second row in a period of time at Tn in the time of should showing the second row, will see that in our vision previous row is in glimmer.The size of brightness is directly proportional with the ratio of displaying time with two row overlapping time, namely is directly proportional with 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 also is not 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. 4.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 realizes scanning display mode by Pmos switching tube switch, because power lead was in tri-state state because stray capacitance exists the voltage on the power lead can not reduce at once when the PMOS switching tube turn-offed, when next frame, may cause showing wrong (conditions of streaking).

The utility model content

The utility model provides a kind of high-speed blanking LED giant-screen scanning monitor, 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 the problems of the technologies described above, the utility model provides a kind of high-speed blanking LED giant-screen scanning control

Device processed comprises: the LED giant-screen drives chip, and the LED giant-screen drives chip and connects code translator; Code translator

Decoding control signal, code translator connects the Pmos switching tube as power switch, Pmos switch controlled

Several rows LED voltage; Include the Nmos voltage pull-down circuits in the described scanning monitor.

The beneficial effects of the utility model are: sweep trace output negative edge can reach about a microsecond, eliminates conditions of streaking and improves refresh rate, eliminates the impact that comes because of the light emitting diode electric leakage.

Described Nmos voltage pull-down circuits is a pulse pull-down circuit, closes to have no progeny at the Pmos switching tube to produce the high level pulse of a short time; Pmos switching tube grid end control end Pmos switching tube Gate controls the Pmos switching tube and turn-offs when high level, Pmos switching tube grid end control end Pmos switching tube Gate controls the Pmos switching tube and opens when low level; Control Nmos switching tube was opened when trombone slide grid end control end NmosGate was high level under the Nmos, and Nmos switching tube grid end control end NmosGate controls the Pmos switching tube and turn-offs when low level; Reaching pmos switching tube pass after Pmos switching tube grid end becomes high level from low level has no progeny, produce a high level pulse by blanking control circuit at the grid end of Nmos pipe, opening the Nmos pipe in the very short time discharges over the ground to scanning power supply Vx, drag down the Vx terminal voltage, accelerated scan power supply Vx turn-off speed.

Comprise that also the Pmos switching tube crosses current circuit and/or overheating protection circuit, it turn-offs the Pmos switching tube behind the controller overcurrent overheat.

Described code translator is decoded as control signal to the double-wire signal that drives chip from the LED giant-screen.

Description of drawings

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

Fig. 1 is existing scan pattern application principle figure;

Fig. 2 is the ideal waveform figure of existing 1/4 scan line power supply;

Fig. 3 is the existing oscillogram that adopts two Pmos switching tubes to control as the row power switch;

Row power switch control waveform figure when Fig. 4 is existing frame frequency 250Hz;

Fig. 5 is that Pmos switch controlled end described in the utility model and the drop-down pipe control end of Nmos and high level pulse concern synoptic diagram;

Fig. 6 is power switch control waveform figure described in the utility model;

Fig. 7 is power switch circuit block diagram described in the utility model;

Fig. 8 is existing product power switch internal frame diagram.

Embodiment

The utility model high-speed blanking LED giant-screen scanning monitor comprises: the LED giant-screen drives chip, and the LED giant-screen drives chip and connects code translator; Code translator is decoding control signal, and code translator connects the two Pmos switching tubes as power switch, two Pmos switch controlled several rows LED voltages; Include voltage pull-down circuits in the described pair of Pmos switching tube circuit.

The utility model adds pull-down circuit, closes a power line voltage of having no progeny at the PMOS switching tube and drags down rapidly to guarantee correctly to show in the next frame data.The utility model improves two Pmos switching tubes increases pull-down circuit, closes at two Pmos switching tubes and has no progeny, and utilizes pull-down circuit to drag down rapidly V1 ~ V4 voltage, improves power supply Vx turn-off speed.Pull-down circuit is exactly a Nmos pipe, and whole circuit block diagram is seen Fig. 7.As shown in Figure 6, the Nmos voltage pull-down circuits is a pulse pull-down circuit, closes to have no progeny at the Pmos switching tube to produce the high level pulse of a short time at once.As shown in Figure 5, Pmos switching tube Gate is Pmos switching tube grid end control end, and its high level Pmos switching tube turn-offs, and the low level switching tube is opened.NmosGate is trombone slide grid end control end under the Nmos, and high level is opened, and low level is turn-offed.When the Pmos switching tube delete become high level from low level after (and pmos switching tube close have no progeny) produce a high level pulse by blanking control circuit at the grid end of Nmos pipe and open the Nmos very short time of pipe scanning power supply Vx is discharged over the ground.Drag down rapidly the Vx terminal voltage) accelerated scan power supply Vx turn-off speed.

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 at once and open the very short reality (about 1us) of Nmos pipe to drag down rapidly the low output terminal of power switch be the VX terminal voltage.

The utility model increases the overcurrent and overheating protection circuit.

The utility model is not limited to embodiment discussed above.More than the description of 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 those of ordinary skill in the art can use numerous embodiments of the present utility model and multiple alternative reaches the purpose of this utility model.

Claims (4)

1. a high-speed blanking LED giant-screen scanning monitor 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 Pmos switching tube as power switch, Pmos switch controlled several rows LED voltage;

Include the Nmos voltage pull-down circuits in the described scanning monitor.

2. high-speed blanking LED giant-screen scanning monitor as claimed in claim 1 is characterized in that, described Nmos voltage pull-down circuits is a pulse pull-down circuit, closes to have no progeny at the Pmos switching tube to produce the high level pulse of a short time;

Pmos switching tube grid end control end Pmos switching tube Gate controls the Pmos switching tube and turn-offs when high level, Pmos switching tube grid end control end Pmos switching tube Gate controls the Pmos switching tube and opens when low level;

Control Nmos switching tube was opened when trombone slide grid end control end NmosGate was high level under the Nmos, and Nmos switching tube grid end control end NmosGate controls the Pmos switching tube and turn-offs when low level;

Reaching Pmos switching tube pass after Pmos switching tube grid end becomes high level from low level has no progeny, produce a high level pulse by blanking control circuit at the grid end of Nmos pipe, opening the Nmos pipe in the very short time discharges over the ground to scanning power supply Vx, drag down the Vx terminal voltage, accelerated scan power supply Vx turn-off speed.

3. high-speed blanking LED giant-screen scanning monitor as claimed in claim 1 or 2 is characterized in that, comprises that also the Pmos switching tube crosses current circuit and/or overheating protection circuit, and it turn-offs the Pmos switching tube behind the controller overcurrent overheat.

4. high-speed blanking LED giant-screen scanning monitor as claimed in claim 1 or 2 is characterized in that, described code translator is decoded as control signal to the double-wire signal that drives chip from the LED giant-screen.

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