CN211181600U

CN211181600U - L ED display screen constant current driving device and its pre-charging circuit

Info

Publication number: CN211181600U
Application number: CN202020141290.2U
Authority: CN
Inventors: 乔红瑗; 袁冶
Original assignee: DOUBLE MICROELECTRONICS Corp OF SHANGHAI
Current assignee: DOUBLE MICROELECTRONICS Corp OF SHANGHAI
Priority date: 2020-01-22
Filing date: 2020-01-22
Publication date: 2020-08-04
Anticipated expiration: 2030-01-22

Abstract

The utility model discloses a constant current drive arrangement of L ED display screen and precharge circuit thereof, including the switch tube, a switch end and the power electricity of switch tube are connected, and another switch end is connected with the drive end electricity of the constant current drive arrangement of L ED display screen, and control circuit, control circuit with the control end of switch tube is connected, wherein when the constant current drive arrangement of L ED display screen opens the switch tube is in off-state, when the constant current drive arrangement of L ED display screen closes, control circuit opens the switch tube charges to the drive end of the constant current drive arrangement of L ED display screen.

Description

L ED display screen constant current driving device and its pre-charging circuit

Technical Field

The utility model relates to an L ED display screen field especially relates to a constant current drive arrangement of L ED display screen and precharge circuit thereof.

Background

The L ED is used as a pixel point to realize large-screen display, and has the advantages of high brightness, low working voltage, low power consumption, large size, long service life, impact resistance and stable performance, so that the light-emitting diode L ED is more and more widely applied.

FIG. 1 shows a circuit schematic diagram (CN103854598A) of a control circuit of a L ED display screen according to the prior art, as shown in FIG. 1, a L ED display screen is composed of M rows by N columns L ED matrix arrangement, a control circuit of a L ED display screen includes L ED display screen drive circuit 30, three drive control circuits, a constant current channel group corresponding to the drive control circuit and a plurality of P-type metal oxide semiconductor (PMOS) switches, the internal architecture of the three drive control circuits is the same, and under the control of L ED display screen drive circuit 30, a display of L4 ED array is driven, the P-MOS switches shown in FIG. 1 are controlled by a row supply control port to realize 73power supply control of the ED array, the anodes of a single row of L ED are interconnected to the drains of P-MOS, the common cathodes of a single column of L primary colors are interconnected to constant current input terminals of the drive control circuit, the sources of P-MOS switches are connected to a power supply terminal, the gates are connected to VCC of the L ED drive circuit 30, the P-MOS switches are connected to a row by row control port of the row, the P-MOS switches are connected to a row sequential power supply control terminal of the drive circuit, the row of the LED drive circuit, the sequential power supply control circuit is opened, and the sequential control circuit is realized by a row of the LED drive circuit is connected to a row of a.

With the further development of the current small-dot-pitch and high-density L ED display screen technology, a L ED display screen puts higher requirements on a driving circuit, for example, the main problems of the existing L ED display screen driving circuit include ghost elimination, lamp bead reverse voltage, short-circuit caterpillar, open-circuit cross, large lamp bead VF value, high contrast coupling and the like, and with the increase of the density of the L ED display screen, the complexity of the driving circuit designed for solving the problems is also continuously improved, so that the interference is stronger and stronger, voltage burrs of about 10 nanoseconds are visible everywhere, and the burrs of tens of nanoseconds can cause the L ED tube to be slightly bright.

There is therefore a need in the art for a response control that can be performed in a few nanoseconds to solve the problems of the L ED display screen control circuit of the prior art.

SUMMERY OF THE UTILITY MODEL

To the problem that exists among the prior art, according to the utility model discloses an embodiment provides a precharge circuit for L ED display screen's constant current drive device, include:

a switch tube having a source electrically connected to the power supply and a drain electrically connected to the drive terminal of the constant current drive device of L ED display screen, an

And the control circuit is electrically connected with the grid electrode of the switch tube, wherein when the constant current driving device of the L ED display screen is turned on, the switch tube is in a closed state, and when the constant current driving device of the L ED display screen is turned off, the control circuit turns on the switch tube to charge the driving end of the constant current driving device of the L ED display screen.

In an embodiment of the present invention, the precharge circuit of the constant current driving device of the L ED display screen further includes a resistor, one end of the resistor is connected to the drain of the switch tube, and the other end of the resistor is connected to the driving end of the constant current driving device.

In an embodiment of the present invention, the control circuit is a PWM pulse control circuit, and the control circuit controls the charge cut-off voltage of the precharge circuit to the driving end by controlling the on duty ratio of the switching tube.

According to another embodiment of the present invention, there is provided a precharge circuit for a constant current driving device of an L ED display screen, including:

one or more switching tubes, wherein the source stage of each switching tube is electrically connected with a power supply;

the resistors are in one-to-one correspondence with the switch tubes, one end of each resistor is electrically connected with the drain electrode of the corresponding switch, and the other end of each resistor is electrically connected with the driving end of the constant current driving device; and

and the control circuit is electrically connected with the grid electrode of each switching tube, wherein when the constant current driving device of the L ED display screen is started, the one or more switching tubes are in a closed state, and when the constant current driving device of the L ED display screen is closed, the control circuit adjusts the opening of the one or more switching tubes to charge the driving end of the constant current driving device of the L ED display screen.

In another embodiment of the present invention, the control circuit changes the charging speed by adjusting the number of the one or more switching tubes that are turned on.

In another embodiment of the present invention, the impedances of the plurality of switching tubes have a proportional relationship, and the impedance of the precharge circuit is controlled by adjusting the conducting number of the switching tubes; or

The impedance of the resistor connected in series with each switching tube has a proportional relation, and the impedance of the pre-charging circuit is controlled by adjusting the conducting number of the switching tubes

In another embodiment of the present invention, the precharge circuit of the constant current driving device for L ED display screen further includes a comparator, a first input terminal of the comparator is connected to the driving terminal, a second input terminal of the comparator receives a reference voltage, and an output terminal of the comparator is connected to the control circuit.

In another embodiment of the present invention, the comparator is a high speed comparator, when the pre-charging circuit is turned on, the control circuit detects whether the voltage of the driving end is lower than the reference voltage through the comparator, once the voltage of the driving end is lower than the reference voltage, the driving end is charged by one or more of the switch tubes until the voltage of the driving end is higher than the reference voltage, and the switch tube is closed.

a current source;

a switch tube having a source electrically connected to the current source and a drain electrically connected to a driving terminal of the constant current driving device of the L ED display screen, an

In another embodiment of the present invention, the current source is a controllable current source, the control circuit is to program the controllable current source, and the driving capability of the current source is adjusted to change the charging speed of the pre-charging circuit.

According to the utility model discloses a further embodiment provides a constant current drive arrangement of L ED display screen, include:

l ED driver, the drive end of the L ED driver is connected with L ED tube of L ED display screen, and

the pre-charging circuit is connected between a power supply and the driving end, and the pre-charging circuit charges the driving end after the L ED driver is closed, so that the voltage at two ends of the L ED tube is lower than the breakover voltage.

In other words, under the condition of L ED pipe of turn-off constant current drive circuit control, pre-charge circuit will be controlled in a few nanoseconds the negative voltage of L ED pipe and pull to specific voltage, guarantee to close back L ED emitting diode off-state at L ED constant current drive circuit, promptly, guarantee that L ED diode does not give out light.

Drawings

To further clarify the above and other advantages and features of various embodiments of the present invention, a more particular description of various embodiments of the invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.

Fig. 1 shows a circuit schematic of a control circuit of an L ED display screen according to the prior art.

FIG. 2 shows a schematic representation of L ED display 200 during operation.

Fig. 3 shows a schematic diagram of a constant current driving device 300 of an L ED display screen according to an embodiment of the present invention.

Fig. 4 shows a schematic diagram of a constant current driving device 400 of an L ED display screen according to an embodiment of the present invention.

Fig. 5 shows a schematic diagram of a constant current driving device 500 of an L ED display screen according to an embodiment of the present invention.

Fig. 6 shows a schematic diagram of a constant current driving device 600 of an L ED display screen according to an embodiment of the present invention.

Fig. 7 shows a schematic diagram of a constant current driving device 700 of an L ED display screen according to an embodiment of the present invention.

Detailed Description

In the following description, the present invention is described with reference to embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of various embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, the invention may be practiced without specific details. Further, it should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

Reference in the specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

FIG. 2 shows a schematic representation of L ED panel 200 in operation, as shown in FIG. 2, if the column driver in the first column needs to be turned off, i.e., constant current is not output, when the row controller scans to the second row L ED tube, a momentary voltage drop spike is generated at the cathode of the L ED tube 21 in the second row and first column of the L ED panel due to the parasitic capacitance effect in the panel, which is 10 to 50 nanoseconds, causing the L ED tube 21 to be slightly bright.

In addition to parasitic capacitance, other circuits in high frequency, high density L ED displays can also generate various types of other voltage spikes, causing the L ED tube that should be turned off to be slightly bright.

Fig. 3 shows a schematic diagram of a constant current driving apparatus 300 of a L ED display panel according to an embodiment of the present invention, as shown in fig. 3, the constant current driving apparatus 300 includes a driver 310 and a pre-charge circuit 320. in the embodiment shown in fig. 3, L ED array 330 is connected between a power supply VDD and the driver 310, wherein other driving circuits and control circuits are omitted for simplicity_F。

In a specific embodiment of the present invention, the response time of the pre-charge circuit 320 is less than 10 ns, in other words, in case of turning off the L ED transistor controlled by the column driver 310, the pre-charge circuit 320 pulls the cathode voltage of the L ED transistor controlled to a specific voltage Vs, which may be substantially equal to the supply voltage VCC, within 10 ns.

Fig. 4 shows a schematic diagram of a constant current driving device 400 of an L ED display screen according to an embodiment of the present invention, as shown in fig. 4, the constant current driving device 400 includes a L ED constant current driving circuit 410 and a pre-charge circuit 420, the pre-charge circuit 420 may also be referred to as a blanking circuit.

The purpose of the pre-charge circuit 420 is to reduce the voltage difference between the L ED cathode and anode after the L ED constant current driver circuit 410 is turned off, ensuring that the L ED led is off after the L ED constant current driver circuit 410 is turned off, i.e., ensuring that the L ED diode is not lit-to simplify the drawing, only one L ED transistor is shown in fig. 4, however, it should be understood by those skilled in the art that the disclosed constant current driver circuit and pre-charge circuit are suitable for use in any number of L ED transistor arrays.

L ED constant current driving circuit 410 and pre-charge circuit 420 work based on L ED switch control signal received from outside, when L0 ED constant current driving circuit 410 is on, the whole pre-charge circuit 420 is in off state, when L ED constant current driving circuit 410 receives constant current off signal, L ED is in weak bias state because of the existence of system and L ED parasitic capacitance 430, L ED both ends voltage is approximately equal to L ED luminous conducting voltage Vf. pre-charge circuit 420 starts working, switch tube 421 of constant current driving end is opened to charge L ED cathode, and reduction of L ED both ends voltage guarantees L ED is in off state.

Specifically, as shown in fig. 4, the pre-charge circuit 420 may include a switch 421, a resistor 422, and a control circuit 423, the switch 421 may be a P-type MOSFET transistor, a source of which is connected to the power VCC, a drain of which is electrically connected to one end of the resistor 422, and a gate of which is controlled by the control circuit 423. in other embodiments of the present invention, the switch 421 may be an N-type MOSFET transistor, a drain of which is connected to the power VCC, a source of which is electrically connected to one end of the resistor 422, and a gate of which is controlled by the control circuit 423. the other end of the resistor 422 is connected to a L ED driving end 440. a cathode of the L ED transistor is also connected to a L ED driving end 440. when an external L ED switch control signal indicates that the L ED constant current driving circuit 410 is turned off, the pre-charge circuit 420 is turned on, the control circuit 423 turns on the switch 421 to charge the L ED constant current driving circuit 410, the switch 421 has a high on time and the switch 421 has a short on time, and the switch 78.

L ED constant current driver circuit 410 may include L ED PWM switch control circuit 411, first MOSFET transistor 412, L ED constant current control circuit 413, and second MOSFET transistor 414, first MOSFET transistor 412 and second MOSFET transistor 414 are N-type MOSFET transistors connected in series between L ED drive terminal 440 and ground, the gate of first MOSFET transistor 412 is connected to L ED PWM switch control circuit 411 and is thus controlled by L ED PWM switch control circuit 411, the gate of second MOSFET transistor 414 is connected to L ED constant current control circuit 413 and is thus controlled by L ED constant current control circuit 413 those skilled in the art will appreciate that the aforementioned L constant current drive circuit 410 is merely illustrative and that the L ED constant current drive circuit 410 may include more, fewer or other types of control circuits and drive circuits.

Fig. 5 shows a schematic diagram of a constant current driving device 500 of an L ED display screen according to an embodiment of the present invention, as shown in fig. 5, the constant current driving device 500 includes a L ED constant current driving circuit 510 and a pre-charge circuit 520, the pre-charge circuit 520 may also be referred to as a blanking circuit.

The purpose of the pre-charge circuit 520 is to reduce the voltage difference between the L ED cathode and anode after the L ED constant current driver circuit 510 is turned off, ensuring that the L ED led is turned off after the L ED constant current driver circuit 510 is turned off, i.e., ensuring that the L ED diode is not lit-to simplify the drawing, only one L ED transistor is shown in fig. 5, however, it should be understood by those skilled in the art that the disclosed constant current driver circuit and pre-charge circuit are suitable for use in any number of L ED transistor arrays.

L ED constant current driving circuit 510 and pre-charge circuit 520 work based on L ED switch control signal received from outside, when L0 ED constant current driving circuit 510 is on, the whole pre-charge circuit 520 is in off state, when L ED constant current driving circuit 510 receives constant current off signal, L ED is in weak bias state because of the existence of system and L ED parasitic capacitance 530, L ED both ends voltage is approximately equal to L ED luminous conducting voltage Vf. pre-charge circuit 520 starts working, one or more switch tubes of constant current driving end are opened to charge L ED cathode, voltage reduction L ED both ends voltage guarantees L is in off state.

Specifically, as shown in fig. 5, the pre-charge circuit 520 may include a comparator 521, one or more switching tubes 522 to 524, one or more resistors 525 to 527, and a control circuit 528, the one or more switching tubes 522 to 524 may be P-type MOSFET transistors, a source of each switching tube is connected to a power source vcc, a gate of each switching tube is controlled by the control circuit 528, a drain of each switching tube is electrically connected to one end of a corresponding one of the one or more resistors 525 to 527, another end of the one or more resistors 525 to 527 is connected to L ED driving terminal 540, a cathode of the L ED tube is connected to L ED driving terminal 540, the switching tubes and the resistors are paired one to one, in the embodiment shown in fig. 5, three switching tubes 522 to 524 and three resistors 525 to 527 are included, that a drain of the switching tube 522 is electrically connected to one end of the resistor 525, a drain of the switching tube 523 is electrically connected to one end of the resistor 526, and a drain of the switching tube 524 is electrically connected to one end of the resistor 527.

However, the scope of the present invention is not limited thereto, and embodiments of the present invention may include more or fewer combinations of switching tubes and resistors. By providing a combination of multiple pairs of switching tubes and resistors, the control circuit 528 can change the charging speed of the pre-charging circuit by adjusting the number of the switching tubes that are turned on.

In the embodiment of the present invention, the impedances of the plurality of switching tubes have a specific proportional relationship, for example, they may be in a ratio similar to 1, 2, 4, 8, etc., and the impedances of the pre-charging circuit can be controlled by adjusting the conducting number of the switching tubes. Alternatively, the impedance of the pre-charging circuit can be controlled by adjusting the conducting number of the switch tubes, by the impedance of each switch tube in series having a specific proportional relationship, for example, the impedance can be a resistor like 1, 2, 4, 8.

The first input of comparator 521 is connected to L ED drive end 540. the second input of comparator 521 receives the reference voltage the output of comparator 521 is connected to control circuit 528. in the embodiment shown in FIG. 5, the first input of comparator 521 is the inverting input, and the second input is the non-inverting input.

When the external L ED switch control signal indicates that the L ED constant current drive circuit 510 is turned off, the precharge circuit 520 is turned on, it is detected by the comparator 521 whether the L ED drive end 540 voltage is lower than the reference voltage, one or more of the switching tubes 522 to 524 are immediately turned on to charge the drive end once the L ED drive end 540 voltage is lower than the reference voltage, and the switching tube is turned off until the L ED drive end 540 voltage is higher than the reference voltage.

The L ED constant current driver circuit 510 is similar to that shown in fig. 4, and therefore the structure and specific operation of the L ED driver circuit will not be described in detail.

Fig. 6 shows a schematic diagram of a constant current driving device 600 of an L ED display screen according to an embodiment of the present invention, as shown in fig. 6, the constant current driving device 600 includes a L ED constant current driving circuit 610 and a pre-charge circuit 620, the pre-charge circuit 620 may also be referred to as a blanking circuit.

The purpose of pre-charge circuit 620 is to reduce the voltage difference between the L ED cathode and anode after L ED constant current driver circuit 610 is turned off, ensuring that the L ED led is off after L ED constant current driver circuit 610 is turned off, i.e., ensuring that the L ED diode is not lit-to simplify the drawing, only one L ED transistor is shown in fig. 6, however, it should be understood by those skilled in the art that the disclosed constant current driver circuit and pre-charge circuit are suitable for use in any number of L ED transistor arrays.

L ED constant current driving circuit 610 and pre-charge circuit 620 work based on L ED switch control signal received from outside, when L0 ED constant current driving circuit 610 is on, the whole pre-charge circuit 620 is in off state, when L ED constant current driving circuit 610 receives constant current off signal, L ED is in weak bias state because of the existence of system and L ED parasitic capacitance 630, L ED both ends voltage is approximately equal to L ED luminous conducting voltage Vf. pre-charge circuit 620 works, switch tube of constant current driving end is opened to charge L ED cathode, voltage reduction L ED both ends voltage guarantees L ED is in off state.

Specifically, as shown in fig. 6, the pre-charge circuit 620 may include a comparator 621, a current source 622, a switch 623 and a control circuit 624, the switch 623 may be a P-type MOSFET transistor, a source of the switch 623 is connected to one end of the current source 622, the other end of the current source 622 is connected to a power vcc, a gate of the switch 623 is controlled by the control circuit 624, a drain of the switch 623 is connected to L ED driving terminal 640, and a cathode of the L ED transistor is connected to L ED driving terminal 640.

The first input of comparator 621 is connected to L ED drive end 640. the second input of comparator 621 receives the reference voltage the output of comparator 621 is connected to control circuit 624. in the embodiment shown in FIG. 6, the first input of comparator 621 is the inverting input, the second input is the non-inverting input. when the non-inverting input voltage is higher than the inverting input, the output tube is cut off, equivalent to the output open circuit.

When the external L ED switch control signal indicates that the L ED constant current driving circuit 610 is turned off, the pre-charge circuit 620 is turned on, and the comparator 621 detects whether the voltage at the L ED driving terminal 640 is lower than the reference voltage, and once the voltage at the L ED driving terminal 640 is lower than the reference voltage, the switch 623 is immediately turned on to charge the driving terminal, and the switch 623 is turned off until the voltage at the L ED driving terminal 640 is higher than the reference voltage.

In one embodiment of the present invention, the control circuit 624 may be a PWM pulse control circuit.

The L ED constant current driver circuit 610 is similar to that shown in fig. 4, and therefore the structure and specific operation of the L ED driver circuit will not be described in detail.

Fig. 7 shows a schematic diagram of a constant current driving device 700 of an L ED display screen according to an embodiment of the present invention, as shown in fig. 7, the constant current driving device 700 includes a L ED constant current driving circuit 710 and a pre-charge circuit 720, the pre-charge circuit 720 may also be referred to as a blanking circuit.

The purpose of the pre-charge circuit 720 is to reduce the voltage difference between the L ED cathode and anode after the L ED constant current driver circuit 710 is turned off, and ensure that the L ED light emitting diode is turned off after the L ED constant current driver circuit 710 is turned off, i.e., ensure that the L ED diode does not emit light.

L ED constant current driving circuit 710 and pre-charge circuit 720 work based on L ED switch control signal received from outside, when L0 ED constant current driving circuit 710 is on, the whole pre-charge circuit 720 is in off state, when L ED constant current driving circuit 710 receives constant current off signal, L ED is in weak bias state because of the existence of system and L ED parasitic capacitance 730, L ED both ends voltage is approximately equal to L ED luminous conducting voltage Vf. pre-charge circuit 720 starts working, switch tube of constant current driving end is opened to charge L ED cathode, and reduction of L ED both ends voltage guarantees L ED is in off state.

Specifically, as shown in fig. 7, the pre-charge circuit 720 may include a comparator 721, a controllable current source 722, a switching tube 723, and a control circuit 724, the switching tube 723 may be a P-type MOSFET transistor, a source of the switching tube 723 is connected to the controllable current source 722, a gate of the switching tube 723 is controlled by the control circuit 724, a drain of the switching tube 723 is connected to an L ED driving terminal 740, a cathode of the L ED tube is connected to a L ED driving terminal 740, the controllable current source 722 is controlled by the control circuit 724, and a magnitude of an output current is adjusted based on a control signal of the control circuit 724.

The first input of the comparator 721 is connected to L ED driving end 740. the second input of the comparator 721 receives the reference voltage. the output of the comparator 721 is connected to the control circuit 724. in the embodiment shown in FIG. 7, the first input of the comparator 721 is the inverting input, the second input is the non-inverting input. when the voltage of the non-inverting input is higher than the voltage of the inverting input, the output tube is off, which is equivalent to an open circuit at the output.

When the external L ED switch control signal indicates that the L ED constant current driver 710 is turned off, the pre-charge circuit 720 is turned on, it is detected whether the voltage at the L ED driver end 740 is lower than the reference voltage by the comparator 721, the switch 723 is turned on immediately to charge the driver end once the voltage at the L ED driver end 740 is lower than the reference voltage, and the switch 723 is turned off until the voltage at the L ED driver end 740 is higher than the reference voltage.

The L ED constant current driver circuit 710 is similar to that shown in fig. 4, and therefore the structure and specific operation of the L ED driver circuit will not be described in detail.

In the above embodiments of the present invention, the response time of the pre-charge circuit is less than 10 ns, in other words, in the case of turning off the L ED transistor controlled by the constant current driving circuit, the pre-charge circuit pulls the voltage of the cathode of the L ED transistor controlled to a specific voltage within a few ns, ensuring the off state of the L ED light emitting diode after the L ED constant current driving circuit is turned off, i.e., ensuring that the L ED diode does not emit light.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A precharge circuit of a constant current driving device of an L ED display screen is characterized by comprising:

a switch tube having one switch end electrically connected to the power supply and the other switch end electrically connected to the drive end of the constant current drive device of L ED display screen, an

And the control circuit is connected with the control end of the switch tube, wherein when the constant current driving device of the L ED display screen is turned on, the switch tube is in a closed state, and when the constant current driving device of the L ED display screen is turned off, the control circuit turns on the switch tube to charge the drive end of the constant current driving device of the L ED display screen.

2. The pre-charge circuit of L ED display screen constant current driving device as claimed in claim 1, further comprising a resistor, one end of the resistor is connected to the other switch end of the switch tube, the other end of the resistor is connected to the driving end of the constant current driving device.

3. The pre-charge circuit of L ED display screen constant current driving device as claimed in claim 1, wherein the control circuit is a PWM pulse control circuit, the control circuit controls the pre-charge circuit to control the charging cut-off voltage of the driving terminal by controlling the on duty ratio of the switch tube.

4. A precharge circuit of a constant current driving device of an L ED display screen is characterized by comprising:

one or more switching tubes, wherein one switching end of each switching tube is electrically connected with a power supply;

the resistors are in one-to-one correspondence with the switching tubes, one end of each resistor is electrically connected with the other switching end of the corresponding switching tube, and the other end of each resistor is electrically connected with the driving end of the constant current driving device; and

and the control circuit is respectively and electrically connected with the control end of each switching tube, wherein when the constant current driving device of the L ED display screen is started, one or more switching tubes are in a closed state, and when the constant current driving device of the L ED display screen is closed, the control circuit adjusts the opening of one or more switching tubes to charge the driving end of the constant current driving device of the L ED display screen.

5. The L ED display screen of constant current drive device of claim 4, wherein, the control circuit changes the charging speed by adjusting the number of the one or more switch tubes.

6. The L ED display screen constant current drive device precharge circuit as claimed in claim 4, wherein the impedances of the multiple switch tubes have a proportional relationship, the precharge circuit impedance is controlled by adjusting the conducting number of the switch tubes, or

The impedance of the resistor connected in series with each switching tube has a proportional relation, and the impedance of the pre-charging circuit is controlled by adjusting the conducting number of the switching tubes.

7. The pre-charge circuit of L ED display screen constant current drive device according to claim 4, further comprising a comparator, the first input terminal of the comparator is connected to the drive terminal, the second input terminal of the comparator receives a reference voltage, the output terminal of the comparator is connected to the control circuit.

8. The L ED display screen of constant current drive device of claim 7, wherein the comparator is a high speed comparator, when the precharge circuit is turned on, the control circuit detects whether the voltage at the driving end is lower than the reference voltage through the comparator, once the voltage at the driving end is lower than the reference voltage, one or more of the switch tubes are turned on to charge the driving end until the voltage at the driving end is higher than the reference voltage, and the switch tubes are turned off.

9. A precharge circuit of a constant current driving device of an L ED display screen is characterized by comprising:

a current source;

a switch tube having one switch end electrically connected with the current source and the other switch end electrically connected with the drive end of the constant current drive device of the L ED display screen, an

And the control circuit is electrically connected with the control end of the switch tube, wherein when the constant current driving device of the L ED display screen is turned on, the switch tube is in a closed state, and when the constant current driving device of the L ED display screen is turned off, the control circuit turns on the switch tube to charge the drive end of the constant current driving device of the L ED display screen.

10. The pre-charge circuit of L ED display screen constant current drive device as claimed in claim 9, further comprising a comparator, the first input terminal of the comparator is connected to the drive terminal, the second input terminal of the comparator receives a reference voltage, the output terminal of the comparator is connected to the control circuit.

11. The pre-charge circuit of L ED display screen constant current driving device as claimed in claim 10, wherein the comparator is a high speed comparator, when the pre-charge circuit is turned on, the control circuit detects whether the voltage at the driving end is lower than the reference voltage through the comparator, once the voltage at the driving end is lower than the reference voltage, one or more of the switch tubes are turned on to charge the driving end until the voltage at the driving end is higher than the reference voltage, and the switch tubes are turned off.

12. A precharge circuit for a constant current driver of an L ED display screen as claimed in claim 9, wherein the current source is a controllable current source, and the control circuit programs the controllable current source to adjust the drive capability of the current source to vary the precharge circuit charging speed.

13. A constant current driving device of L ED display screen, which is characterized in that it includes: