A multi-channel negative voltage output circuit for partial erasure of liquid crystal film writing blackboard

Abstract

This invention proposes a multi-channel negative voltage output circuit for partial erasure of liquid crystal film writing blackboards. The circuit comprises a signal receiving and transmission circuit, an MCU logic control circuit, a negative voltage output circuit, a negative voltage boost generation circuit, and a liquid crystal display driver chip circuit. The signal receiving and transmission circuit transmits control signals to the MCU logic control circuit, which generates a logic control level. This logic control level is applied to the negative voltage output circuit, which generates a negative voltage. This negative voltage is then boosted by the negative voltage boost generation circuit and input to the liquid crystal display driver chip circuit. By using the multi-channel negative voltage output circuit, multiple varying negative voltages can be obtained, ultimately providing the necessary negative voltage for partial erasure of writing marks on the liquid crystal writing blackboard.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal film, and particularly relates to a multi-path negative voltage output circuit for local erasing of a liquid crystal film writing blackboard. BACKGROUND

[0002] In order to solve the problem of dust of a traditional blackboard, a liquid crystal writing blackboard appears in the market at present. The liquid crystal writing blackboard uses a cholesteric phase liquid crystal and a high polymer mixture material as a writing substrate. Since the material has the characteristics that the reflection state and the scattering state are both stable states, a user can freely write on the liquid crystal writing blackboard by using a hard object, and the writing experience is consistent with that of paper writing. The liquid crystal writing blackboard can solve the problem of dust of a traditional blackboard and protect eyes.

[0003] At present, most of the liquid crystal writing blackboards can only remove all traces in the liquid crystal writing blackboard by overall energization when the traces are removed, and cannot meet the need of local erasing. At present, the liquid crystal writing blackboard mostly uses a positive voltage for voltage control, but local erasing needs to use a negative voltage. The negative voltage obtained by DC-DC voltage boosting only has one voltage and cannot be controlled in multiple paths and obtain different negative voltages. Some use a potentiometer to adjust the voltage, which is very inconvenient for manufacturers and customers and is not good for automatic control and adjustment of the voltage to adapt to different film sheets and different environmental temperatures. SUMMARY

[0004] The main purpose of the present application is to provide a multi-path negative voltage output circuit for local erasing of a liquid crystal film writing blackboard. The multi-path negative voltage output circuit uses an MCU control, changes the negative feedback impedance of a control loop, thereby changing the output negative voltage, obtains multiple combined negative voltages through several groups or multiple groups of control, and then provides the negative voltages to a liquid crystal display driving chip circuit to complete the local erasing function.

[0005] To achieve the above purpose, the present application is implemented by the following technical scheme:

[0006] The present application provides a multi-path negative voltage output circuit for local erasing of a liquid crystal film writing blackboard. The multi-path negative voltage output circuit for local erasing of the liquid crystal film writing blackboard comprises a signal receiving and transmission circuit, an MCU logic control circuit, a negative voltage output circuit, a negative voltage boosting generation circuit and a liquid crystal display driving chip circuit.

[0007] The signal receiving and transmission circuit transmits a control signal to the MCU logic control circuit. The MCU logic control circuit generates a logic control level, and the logic control level is loaded into the negative voltage output circuit. The negative voltage output circuit generates a negative voltage. The negative voltage is boosted by the negative voltage boosting generation circuit, and the boosted negative voltage is input into the liquid crystal display driving chip circuit.

[0008] The negative voltage output circuit is composed of one or more negative voltage generating circuits, the MCU logic control circuit and the negative voltage boost generating circuit are connected with all the negative voltage generating circuits in the negative voltage output circuit, and each negative voltage generating circuit can generate a negative voltage required for local erasing.

[0009] Further, the negative voltage generating circuit comprises field effect tubes Q1, Q2, Q3 and resistors R1, R2, R3, R4 and R5, the control electrode of Q1 is connected to the MCU logic control circuit, R1 is a pull-down resistor, R2 is a pull-up resistor, one end of R1 is connected to the control electrode of Q1, the other end of R1 is connected to the source electrode of Q1 and grounded, one end of R2 is connected to the drain electrode of Q1 and the control electrode of Q2, the other end of R2 is connected to the drain electrode of Q2 and connected to the voltage VCC, one end of R3 is connected to the source electrode of Q2, the other end of R3 is connected to the control electrode of Q3, R4 is a pull-down resistor of Q3, R4 is connected to the source electrode of Q3 and connected to the negative voltage output Vout, and the drain electrode of Q3 is connected in series with R5.

[0010] Further, the negative voltage output circuit further comprises resistors R11 and R12, R11 is a feedback pin grounding resistor of the negative voltage boost generating circuit, and R12 is connected on the negative voltage output circuit to form a loop control with the feedback pin of the negative voltage boost generating circuit.

[0011] Further, the negative voltage generating circuit comprises transistors Q1A, Q2A, Q3A and resistors R1A, R2A, R3A, R4A and R5A.

[0012] Further, the negative voltage generating circuit comprises transistors Q1A1 and Q3A1, field effect tube Q4 and resistors R1A1, R2A1, R3A1, R4A1 and R5A1.

[0013] Further, the negative voltage output circuit has n negative voltage generating circuits, n is greater than or equal to 2, and the n negative voltage generating circuits are connected in parallel.

[0014] Further, the signal receiving and transmitting circuit is connected with an infrared sensor, a photoelectric sensor, a temperature sensor and a control button.

[0015] Further, the MCU logic control circuit comprises an MCU main control chip, a power conversion chip, a battery charging chip, a liquid crystal driving chip, a USB port and a power interface.

[0016] The present application has the following advantages:

[0017] The multi-path negative voltage output circuit for local erasing of liquid crystal film writing blackboard provided by the application can obtain the superposition and combination of multi-path loop negative feedback impedance through the negative voltage output circuit and the negative voltage boosting generation circuit, further obtain multi-path variable negative voltage, and finally obtain the local erasing negative voltage required for erasing writing traces of the liquid crystal blackboard, and further provide the liquid crystal display driving chip circuit to complete the local erasing function; through the control of the infrared sensor or the temperature sensor, the negative voltage value can be manually or automatically adjusted, and the inaccuracy and inconvenience of single voltage change or only manual adjustment of the potentiometer of the circuit board can be compensated. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The figure is a circuit structure schematic diagram of the multi-path negative voltage output circuit for local erasing of liquid crystal film writing blackboard provided by the application.

[0019] Figure 2 The figure is a circuit schematic diagram of the negative voltage output circuit of the embodiment 1 of the application.

[0020] Figure 3 The figure is a circuit schematic diagram of the negative voltage generation circuit of the embodiment 2 of the application.

[0021] Figure 4 The figure is a circuit schematic diagram of the negative voltage generation circuit of the embodiment 3 of the application.

[0022] Figure 5 The figure is a schematic diagram of the application of the negative voltage output in the local erasing of liquid crystal film.

[0023] Figure 6 The figure is a circuit diagram of the existing liquid crystal handwriting blackboard for adjusting and erasing voltage.

[0024] Figure 7 The figure is a schematic diagram of the application of the negative voltage output circuit of the application in the local erasing of liquid crystal writing film blackboard user terminal for adjusting and erasing voltage automatic control. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0026] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, motion condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications will also change accordingly.

[0027] In addition, if the embodiments of the present application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of a person skilled in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist and is not within the protection scope required by the present application.

[0028] Embodiment 1

[0029] Please refer to Figure 1 and Figure 2 , the present application proposes a multi-channel negative voltage output circuit for local erasing of a liquid crystal film writing blackboard, the multi-channel negative voltage output circuit for local erasing of the liquid crystal film writing blackboard comprises a signal receiving transmission circuit, an MCU logic control circuit, a negative voltage output circuit, a negative voltage boost generation circuit, a liquid crystal display driving chip circuit;

[0030] The signal receiving transmission circuit transmits a control signal to the MCU logic control circuit, the MCU logic control circuit generates a logic control level, and the logic control level is loaded into the negative voltage output circuit, the negative voltage output circuit generates a negative voltage, and the negative voltage is boosted by the negative voltage boost generation circuit, and the boosted negative voltage is input into the liquid crystal display driving chip circuit;

[0031] The negative voltage output circuit is composed of n negative voltage generation circuits, the n negative voltage generation circuits are connected in parallel, and the number of the negative voltage generation circuits is determined according to the number of areas required for local erasing of the liquid crystal handwriting film blackboard. The MCU logic control circuit and the negative voltage boost generation circuit are connected with all the negative voltage generation circuits in the negative voltage output circuit, and each negative voltage generation circuit can generate a negative voltage required for local erasing.

[0032] In the embodiment, the signal receiving transmission circuit is connected with an infrared sensor, a temperature sensor, a control button and a photoelectric sensor. The infrared sensor is installed around the frame of the liquid crystal film writing blackboard using the circuit of the application and is located on the surface of the liquid crystal film. The infrared sensor has very high resolution (32767x32767). When the writing pen or finger contacts the surface of the liquid crystal film, the infrared sensor is blocked, so that the position coordinate information is obtained. The position coordinate information is input to the control circuit, so that the corresponding erasing control can be performed. Meanwhile, the position coordinate information is input to the USB port and connected to the all-in-one computer. Through the special blackboard software, the clear handwriting can be displayed on the all-in-one computer.

[0033] The MCU logic control circuit comprises an MCU main control chip, a power conversion chip, a battery charging chip, a liquid crystal driving chip, a USB port and a power interface. The MCU main control chip mainly receives the data provided by the infrared sensor and then sends the data to the liquid crystal display driving chip circuit, so that the erasing function is completed. In addition, the MCU main control chip can also control the power conversion, so that different required positive and negative voltages are obtained. The power conversion chip mainly converts the external adapter power supply or external lithium battery power supply to obtain a plurality of different voltages under the control of the MCU main control chip.

[0034] In the embodiment, the temperature sensor is mainly used for testing the ambient temperature, and the obtained temperature information can be provided to the MCU logic control circuit to change the erasing voltage of the film material. The photoelectric sensor is mainly used for power saving control of the circuit. When it is night, part of the power supply can be turned off to achieve the effects of energy saving and environmental protection and prolong the service life of electronic parts. The battery charging chip is mainly used for charging the external lithium battery. The USB interface is mainly used for the all-in-one machine. The power interface is used for the adapter to connect the power supply.

[0035] The liquid crystal display driving chip circuit is mainly composed of a liquid crystal display driving chip, which is a special chip for driving an STN liquid crystal display. The main function is to provide a corresponding erasing voltage at a liquid crystal position to be erased according to position coordinate information provided by the MCU logic control circuit, and to provide a bias BIAS voltage that cannot erase at a position that does not need to be erased. After the control signal input by the signal transmission circuit, the MCU master control chip in the MCU logic control circuit generates a logic control level, which is loaded into the negative voltage output circuit, and then a required number of loop control impedances are obtained. These impedances are input into the negative voltage boost generating circuit, and finally a corresponding number of variable negative voltages are generated. These voltage negative voltages are exactly the voltages required by the liquid crystal display driving chip circuit. Then, the liquid crystal display driving chip circuit converts each voltage into various voltage waveforms and loads them onto the liquid crystal film blackboard, thereby completing the functions of local erasing and overall erasing.

[0036] Further, the negative voltage generating circuit includes field effect tubes Q1, Q2, Q3 and resistors R1, R2, R3, R4, R5. The control electrode of Q1 is connected to the MCU logic control circuit. R1 is a pull-down resistor, R2 is a pull-up resistor, one end of R1 is connected to the control electrode of Q1, the other end of R1 is connected to the source electrode of Q1 and grounded, one end of R2 is connected to the drain electrode of Q1 and the control electrode of Q2, the other end of R2 is connected to the drain electrode of Q2 and connected to the voltage VCC, one end of R3 is connected to the source electrode of Q2, the other end of R3 is connected to the control electrode of Q3, R4 is a pull-down resistor of Q3, R4 is connected to the source electrode of Q3 and connected to the negative voltage output Vout, and the drain electrode of Q3 is connected in series with R5.

[0037] In the embodiment, the negative voltage output circuit further includes resistors R11 and R12. R11 is a feedback pin grounding resistor of the negative voltage boost generating circuit, and R12 is connected to the negative voltage output circuit and forms a loop control with the feedback pin of the negative voltage boost generating circuit.

[0038] In the embodiment, the control signals of multiple negative voltages are mainly composed of infrared sensors, photoelectric sensors, temperature sensors, and key inputs. These control signals are input into the MCU in the MCU logic control circuit, and the MCU generates a logic control level. The control level is loaded into the negative voltage output circuit, and then a plurality of loop control impedances are obtained. This impedance is input into the negative voltage boost generating circuit, and finally 1, 2, 3... n variable negative voltages are generated. This negative voltage is exactly the voltage required by the liquid crystal display driving chip circuit. Then, the liquid crystal display driving chip circuit converts each voltage into various voltage waveforms and loads them onto the liquid crystal film blackboard, thereby completing the functions of local erasing and overall erasing.

[0039] Each negative voltage is composed of a negative voltage generating circuit, and several negative voltage generating circuits are needed for several negative voltages. The control electrode of Q1 is connected to the control pin of MCU. R1 is a pull-down resistor, which outputs low level when not controlled and outputs high level when controlled. R2 is pulled up to VCC (for example, 5V) and then connected to the drain of Q1 and the control electrode of Q2. When MCU is not controlled, the control electrode of Q2 is high level, and the voltage VCC at the source of Q2 cannot pass through Q2 to reach R3. When the control pin of MCU is high level, Q1 is turned on, the control electrode of Q2 changes from high to low, and then Q2 is turned on. The voltage VCC at the source is connected to the control electrode of Q3 through R3, and R4 is a pull-down resistor of Q3 connected to the source and the negative voltage output Vout. At this time, the voltage VCC of the turned-on Q2 is directly loaded to the control electrode of Q3, and then Q3 is also turned on. R5 is connected in series to the drain of Q3. R11 is a feedback pin grounding resistor of the negative voltage boost generating circuit. R12 is connected to the feedback pin of the negative voltage output circuit and the negative voltage boost generating circuit to form a loop control. When Q3 is turned on, R5 is connected to the feedback resistor R12, and then a smaller impedance resistance is obtained. Through loop feedback control, the negative voltage boost generating circuit obtains a new voltage value. By analogy, when MUC is controlled by multiple paths, we can get multiple variable negative voltages. When we change the liquid crystal film material or the environmental temperature changes greatly, the liquid crystal driving voltage must be changed accordingly. Through the multi-channel negative voltage output circuit for local erasing of the liquid crystal film writing blackboard, we can conveniently control the output of multiple negative voltages manually and automatically, and finally complete the functions of local erasing and overall erasing.

[0040] Please refer to Figure 5 , Figure 5is a schematic diagram of a negative voltage output application in a liquid crystal film local erasing blackboard, and the local erasing liquid crystal film writing blackboard is mainly composed of an upper ITO conductive terminal, a middle liquid crystal, and a lower ITO conductive terminal. The ITO conductive film refers to a high-tech product obtained by sputtering a transparent indium tin oxide (ITO) conductive film coating on a transparent organic film PET material by a magnetron sputtering or evaporation or reaction ion plating, chemical vapor deposition, etc. The ITO conductive terminal is a conductive film strip obtained by etching the corresponding X-axis and Y-axis perpendicular to each other, such as the X-axis 1 conductive strip, the X-axis 2 conductive strip, the X-axis 3 conductive strip, the X-axis 4 conductive strip, the X-axis 5 conductive strip, the X-axis 6 conductive strip, and the X-axis perpendicular to the Y-axis 1 conductive strip, the Y-axis 2 conductive strip, the Y-axis 3 conductive strip, the Y-axis 4 conductive strip, the Y-axis 5 conductive strip, and the Y-axis 6 conductive strip. When we want to erase a certain position, we can erase the intersection of the X-axis and the Y-axis by applying positive and negative alternating voltages to the conductive strips of the X-axis and the Y-axis at the corresponding positions. If positive and negative alternating voltages are applied to multiple conductive strips of the X-axis and the Y-axis at the same time, a local erasing of a region will be performed. The multi-channel negative voltage output circuit for local erasing of the liquid crystal film writing blackboard is mainly applied to provide different negative voltages to the liquid crystal film, so as to achieve the ideal local erasing function of the liquid crystal writing blackboard.

[0041] Please refer to Figure 6 and Figure 7 , Figure 6 is a prior art circuit diagram for adjusting the erasing voltage, Figure 7 is a schematic diagram of the negative voltage output circuit applied to the user end of the liquid crystal writing film local erasing blackboard for automatic control of the erasing voltage (gesture control). The liquid crystal writing film local erasing blackboard may need to be fine-tuned for the erasing voltage under different temperature environments to achieve the best erasing effect. In addition, as the service life of the liquid crystal writing film local erasing blackboard increases, the liquid crystal molecule image may change, so the erasing voltage may also need to be fine-tuned to achieve the best erasing effect. The prior art control circuit for adjusting the voltage is shown in Figure 6 . The commonly used way to adjust the single negative voltage is to add an adjustable potentiometer RP1 in the loop feedback circuit, so that the negative feedback voltage is changed by changing the resistance of RP1, thereby obtaining the adjusted single negative voltage. This method has the problems of only being suitable for factory production, not being suitable for user adjustment of the erasing voltage, being unable to perform automatic voltage adjustment control, and having low reliability. Therefore, we have developed the following multi-channel negative voltage output control circuit.

[0042] The liquid crystal film local erasing blackboard using the present application can be set as Figure 7The infrared sending or receiving sensors are installed at the upper and lower (X-axis) and left and right (Y-axis) frames. Through the sensors and the control circuit, the infrared network can achieve an ultra-high precision resolution of 32767x32767. The corresponding coordinate data can be obtained by blocking the infrared rays. The computer can display the writing traces or automatically control the erasing voltage by obtaining the position data of the special coordinates. The liquid crystal writing film generally has a special eraser for locally erasing the blackboard. The user can adjust the erasing voltage by using the eraser as follows: the eraser is placed in the following order: the lower left corner (1) -> the lower right corner (2) -> the upper right corner (3) -> the upper left corner (4) and the middle upper position (5) in the drawing. If the coordinate data position is completed within the specified time (for example, 25 seconds), the erasing voltage is increased by one level (for example, +1V). Similarly, if the eraser is placed in the following order: the lower left corner (1) -> the lower right corner (2) -> the upper right corner (3) -> the upper left corner (4) and the middle lower position (6) in the drawing, the erasing voltage is decreased by one level (for example, -1V). Through the above operation repeatedly, the user can conveniently change the erasing voltage of the liquid crystal writing film for locally erasing the blackboard, so as to achieve a satisfactory erasing effect. These applications are achieved by the multi-channel negative voltage output circuit for locally erasing the liquid crystal film writing blackboard.

[0043] Embodiment 2

[0044] Please refer to Figure 3 On the basis of Embodiment 1, the present embodiment proposes a multi-channel negative voltage output circuit for locally erasing the liquid crystal film writing blackboard. Compared with Embodiment 1, the negative voltage generating circuit in the present embodiment includes transistors Q1A, Q2A, Q3A and resistors R1A, R2A, R3A, R4A, R5A. The difference lies in that the transistors are used instead of the field effect tubes. The circuit connection mode of the present embodiment is exactly the same as that of Embodiment 1, and the effect is also the same.

[0045] Embodiment 3

[0046] Please refer to Figure 4 On the basis of Embodiment 1, the present embodiment proposes a multi-channel negative voltage output circuit for locally erasing the liquid crystal film writing blackboard. Compared with Embodiment 1, the negative voltage generating circuit in the present embodiment includes transistors Q1A1, Q3A1, a field effect tube Q4 and resistors R1A1, R2A1, R3A1, R4A1, R5A1. The difference lies in that two transistors are used instead of two field effect tubes. The circuit connection mode of the present embodiment is exactly the same as that of Embodiment 1, and the effect is also the same.

[0047] It should be explained that the technical solutions of various embodiments of the present application can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, when the combination of technical solutions appears contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist, nor is it within the protection scope required by the present application.

[0048] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structural transformation made by using the content of the specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A multi-channel negative voltage output circuit for partial erasing of a liquid crystal film writing blackboard, characterized by, The multi-channel negative voltage output circuit for local erasing of the liquid crystal film writing blackboard comprises a signal receiving transmission circuit, an MCU logic control circuit, a negative voltage output circuit, a negative voltage boosting generation circuit and a liquid crystal display driving chip circuit. The signal receiving transmission circuit transmits a control signal to the MCU logic control circuit, the MCU logic control circuit generates a logic control level, the logic control level is loaded into the negative voltage output circuit, the negative voltage output circuit generates a negative voltage, and the negative voltage is boosted by the negative voltage boosting generation circuit and input into the liquid crystal display driving chip circuit. The negative voltage output circuit comprises one or more negative voltage generation circuits, the MCU logic control circuit and the negative voltage boosting generation circuit are connected with all the negative voltage generation circuits in the negative voltage output circuit, and each negative voltage generation circuit can generate a negative voltage required for local erasing. The negative voltage generation circuit comprises field effect tubes Q1, Q2 and Q3 and resistors R1, R2, R3, R4 and R5, the control electrode of Q1 is connected to the MCU logic control circuit, R1 is a pull-down resistor, R2 is a pull-up resistor, one end of R1 is connected to the control electrode of Q1, the other end of R1 is connected to the source electrode of Q1 and grounded, one end of R2 is connected to the drain electrode of Q1 and the control electrode of Q2, the other end of R2 is connected to the drain electrode of Q2 and connected with a voltage VCC, one end of R3 is connected to the source electrode of Q2, the other end of R3 is connected to the control electrode of Q3, R4 is a pull-down resistor of Q3, R4 is connected to the source electrode of Q3 and connected to a negative voltage output Vout, and the drain electrode of Q3 is connected with R5 in series. The negative voltage output circuit further comprises resistors R11 and R12, R11 is a feedback foot grounding resistor of the negative voltage boosting generation circuit, and R12 is connected on the negative voltage output circuit to form a loop control with the feedback foot of the negative voltage boosting generation circuit.

2. The multi-channel negative voltage output circuit for partial erasing of a liquid crystal film writing blackboard according to claim 1, wherein The field effect tubes Q1, Q2 and Q3 in the negative voltage generation circuit are bipolar transistors.

3. The multi-channel negative voltage output circuit for partial erasure of a liquid crystal film writing blackboard according to claim 1, wherein The field effect tubes Q1 and Q3 in the negative voltage generation circuit are bipolar transistors.

4. The multi-channel negative voltage output circuit for partial erasure of a liquid crystal film writing blackboard according to claim 1, wherein The negative voltage output circuit has n negative voltage generation circuits, n is greater than or equal to 2, and the n negative voltage generation circuits are connected in parallel.

5. The multi-channel negative voltage output circuit for partial erasure of a liquid crystal film writing blackboard according to claim 1, wherein The signal receiving transmission circuit is connected with an infrared sensor, a photoelectric sensor, a temperature sensor and a control button.

6. The multi-channel negative voltage output circuit for partial erasure of a liquid crystal film writing blackboard according to claim 1, wherein The MCU logic control circuit comprises an MCU master control chip, a power conversion chip, a battery charging chip, a liquid crystal driving chip, a USB port and a power interface.

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