Liquid crystal handwriting board

Abstract

The utility model discloses a liquid crystal handwriting board which comprises a control circuit, a first control assembly, a second control assembly, a third control assembly, a first liquid crystal film and a second liquid crystal film, the first input end of the control circuit is electrically connected with the first control assembly, the second input end of the control circuit is electrically connected with the second control assembly, the third input end of the control circuit is electrically connected with the third control assembly, the first output end of the control circuit is electrically connected with the first liquid crystal film, and the second output end of the control circuit is electrically connected with the second liquid crystal film. According to the scheme, double-color display of the liquid crystal handwriting board can be controlled.

Description

Technical Field

[0001] This utility model relates to the field of liquid crystal film handwriting tablet technology, and in particular to a liquid crystal handwriting tablet. Background Technology

[0002] After students write or complete exercises on LCD writing tablets or small blackboards, they often need teachers or parents to correct and annotate them. However, current LCD writing tablets and small blackboards only have one color, making it difficult to distinguish between the student's writing and the teacher's / parent's annotations. Therefore, there is an urgent need to improve LCD writing tablets so that the corrections are more eye-catching and clear, making it easier for students to check and correct their work. Utility Model Content

[0003] The main purpose of this invention is to propose a liquid crystal handwriting tablet that controls the dual-color display of the liquid crystal handwriting tablet.

[0004] To achieve the above objectives, this utility model proposes a liquid crystal handwriting tablet, including a control circuit, a first control component, a second control component, a third control component, and a first liquid crystal film and a second liquid crystal film arranged sequentially from top to bottom; the first input terminal of the control circuit is electrically connected to the first control component, the second input terminal of the control circuit is electrically connected to the second control component, the third input terminal of the control circuit is electrically connected to the third control component, the first output terminal of the control circuit is electrically connected to the first liquid crystal film, and the second output terminal of the control circuit is electrically connected to the second liquid crystal film.

[0005] Optionally, the control circuit includes a power supply module, an MCU logic control circuit, and an output circuit; the first output terminal of the power supply module is connected to the power supply terminal of the output circuit, the controlled terminal of the power supply module is connected to the first control terminal of the MCU logic control circuit, the second control terminal of the MCU logic control circuit is connected to the controlled terminal of the output circuit, the first output terminal of the output circuit is the first output terminal of the control circuit, and the second output terminal of the output circuit is the second output terminal of the control circuit.

[0006] Optionally, the power module includes a charging interface, a charging circuit, an energy storage battery, and a switching boost circuit. The charging interface is connected to the input terminal of the charging circuit, the output terminal of the charging circuit is connected to the input terminal of the energy storage battery, and the output terminal of the energy storage battery is connected to the input terminal of the switching boost circuit. The connection node is the first output terminal of the power module. The controlled terminal of the switching boost circuit is the controlled terminal of the power module, and the output terminal of the switching boost circuit is the first output terminal of the power module.

[0007] Optionally, the switching boost circuit includes capacitors C25, C26, C27, C28, and C30; resistors R65, R66, R68, R69, R70, R72, and R74; transistors Q8 and Q9; boost chip U5; inductors LE1, LE4, and L4; and Zener diode D3. The first terminal of capacitor C30, the first terminal of resistor R72, and the source of transistor Q8 are interconnected, forming the input terminal of the switching boost circuit. The second terminal of resistor R72, the gate of transistor Q8, and the drain of transistor Q9 are interconnected. The gate of transistor Q9 is connected to the first terminal of resistor R74, forming the controlled terminal of the switching boost circuit. The drain of transistor Q8, the first terminal of capacitor C27, and the first terminal of inductor LE4 are interconnected. The second terminal of inductor LE4, the first terminal of capacitor C26, the first terminal of inductor L4, and the VIN terminal of boost chip U5 are interconnected. The following interconnections are made: the EN pin of the boost chip U5 is interconnected; the second terminal of inductor L4, the LX pin of boost chip U5, and the anode of Zener diode D3 are interconnected; the cathode of Zener diode D3, the first terminal of resistor R66, the first terminal of capacitor C25, the first terminal of resistor R68, and the first terminal of inductor LE1 are interconnected; the second terminals of resistor R66, the first terminal of resistor R65, the FB pin of boost chip U5, and the first terminal of resistor R69 are interconnected; the second terminal of resistor R69, the first terminal of capacitor C28, and the first terminal of resistor R70 are interconnected; the second terminal of capacitor C30, the source of transistor Q9, the second terminal of capacitor C27, the second terminal of capacitor C26, the GND pin of boost chip U5, the second terminal of resistor R65, the second terminal of capacitor C25, the second terminal of resistor R68, and the second terminal of capacitor C28 are grounded; the second terminal of inductor LE1 is the output terminal of the switching boost circuit, and the second terminal of resistor R70 is used to receive the power feedback control signal.

[0008] Optionally, the power module also includes a locking toggle switch, which is located between the energy storage battery and the switching boost circuit, and is connected in series with the energy storage battery and the switching boost circuit.

[0009] Optionally, the MCU logic control circuit includes a control chip U1, resistors R55, R54, R53, R52, R64, R34, R35, R58, R59, R27, R51, R36, R16, capacitors C37, C16, C14, C32, and inductor LE11; the first terminal of inductor LE11 is used for inputting the power supply of the control chip U1, the second terminal of inductor LE11, the first terminal of capacitor C37, the first terminal of capacitor C16, and the control chip U1. The VCC pin of control chip U1 is interconnected with the ADC_VREF+ pin of control chip U1. Pin P5.4 of control chip U1 is connected to the second terminal of resistor R64, with the first terminal of resistor R64 used to output the power feedback control signal. Pin P1.7 of control chip U1 is connected to the second terminal of resistor R52, pin P1.6 of control chip U1 is connected to the second terminal of resistor R53, pin P1.3 of control chip U1 is connected to the second terminal of resistor R54, and pin P1.2 of control chip U1 is connected to the second terminal of resistor R55. (MCU logic...) The second control terminal of the control circuit includes the first terminals of resistors R55, R54, R53, and R52; pin P1.1 of control chip U1, the second terminal of capacitor C14, the second terminal of resistor R34, and the first terminal of resistor R35 are interconnected. The first terminal of resistor R34 is connected to the power supply. Pin P3.7 of control chip U1 is connected to the first terminal of resistor R58. The second terminal of resistor R58 is the first input terminal of the control circuit. Pin P3.6 of control chip U1 is connected to the first terminal of resistor R59. The second terminal of 59 is the second input terminal of the control circuit. The P3.5 pin of the control chip U1 is connected to the first terminal of the resistor R27. The second terminal of the resistor R27 is the first control terminal of the MCU logic control circuit. The P3.3 pin of the control chip U1 is connected to the first terminal of the resistor R51. The second terminal of the resistor R51 is the third input terminal of the control circuit. The P3.1 and P3.0 pins of the control chip U1 are used to transmit software data. The capacitors C37, C16, the GND pin of the control chip U1, and the first terminal of the capacitor C14 are grounded.

[0010] Optionally, the output circuit includes a first H-bridge circuit and a second H-bridge circuit that are independent of each other; the first H-bridge circuit includes resistors R33, R37, R38, R39, R40, R41, R42, R43, and R44, transistors Q10, Q11, and Q12; the first terminal of resistor R33, the first terminal of resistor R40, and the first drain of transistor Q10 are interconnected, and their connection node is the first sub-output terminal of the first H-bridge circuit; the second terminal of resistor R33, the first terminal of resistor R44, and the first drain of transistor Q11 are interconnected, and their connection node is the second sub-output terminal of the first H-bridge circuit. The first output terminal of the output circuit includes the first sub-output terminal and the second sub-output terminal of the first H-bridge circuit; the second terminal of resistor R40 is connected to the second drain of transistor Q10, and the first source of transistor Q10 is connected to the second terminal of resistor R43, and their connection node is used to input the power supply output by the power module; the second gate of transistor Q10 and the first terminal of resistor R43 are connected to the second drain of transistor Q10. The first terminal of resistor R42 is interconnected with the first terminal of resistor R44; the second terminal of resistor R44 is connected to the second drain of transistor Q11, and the first source of transistor Q11 is connected to the first terminal of resistor R39. The connection is used to input the power supply output of the power module; the first gate of transistor Q11, the second terminal of resistor R39, and the first terminal of resistor R38 are interconnected; the first gate of transistor Q10, the second terminal of resistor R37, and the first gate of transistor Q12 are interconnected, and their connection node is the second sub-input terminal of the first H-bridge circuit; the second gate of transistor Q11, the first terminal of resistor R41, and the second gate of transistor Q12 are interconnected, and their connection node is the first sub-input terminal of the first H-bridge circuit; the second drain of transistor Q12 is connected to the second terminal of resistor R42, and the first drain of transistor Q12 is connected to the second terminal of resistor R38; the first source of transistor Q10, the second source of transistor Q11, the first source of transistor Q12, the second source of transistor Q12, the first terminal of resistor R37, and the second terminal of resistor R41 are grounded.

[0011] Optionally, the first liquid crystal film includes a writing liquid crystal film surface layer, a first ITO conductive layer, a first liquid crystal layer, and a second ITO conductive layer, which are arranged sequentially from top to bottom.

[0012] Optionally, the second liquid crystal film includes a first PET material layer, a third ITO conductive layer, a second liquid crystal layer, a fourth ITO conductive layer, and a second PET material layer disposed sequentially from top to bottom.

[0013] Optionally, the LCD handwriting tablet also includes an indicator component, which is electrically connected to the control circuit and is used to indicate the working status of the first control component, the second control component, and / or the third control component.

[0014] This LCD writing tablet achieves dual-color display by setting up a first liquid crystal film and a second liquid crystal film, and configuring three sets of control components and control circuits corresponding to the first and second liquid crystal films. This is especially convenient in scenarios where parents / teachers are grading student homework, as it can display the student's writing and the parent / teacher's annotations in two different colors. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of one embodiment of the liquid crystal handwriting tablet of this utility model;

[0016] Figure 2 This is a schematic diagram of another embodiment of the liquid crystal handwriting tablet of this utility model;

[0017] Figure 3 This is a schematic diagram of another embodiment of the liquid crystal handwriting tablet of this utility model;

[0018] Figure 4 for Figure 3 A schematic diagram of the structure of a control circuit, a first control component, a second control component, a third control component, and an indicator component according to an embodiment;

[0019] Figure 5 for Figure 3 A schematic diagram of an embodiment of a switching boost circuit;

[0020] Figure 6 This is a schematic diagram of an embodiment of the first H-bridge circuit and the second H-bridge circuit. Detailed Implementation

[0021] The solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0022] Please see Figures 1 to 3 This utility model provides a liquid crystal writing tablet, which includes a control circuit 400, a first control component 100, a second control component 200, a third control component 300, and a first liquid crystal film 500 and a second liquid crystal film 600 arranged sequentially from top to bottom; the first input terminal of the control circuit 400 is electrically connected to the first control component 100, the second input terminal of the control circuit 400 is electrically connected to the second control component 200, the third input terminal of the control circuit 400 is electrically connected to the third control component 300, the first output terminal of the control circuit 400 is electrically connected to the first liquid crystal film 500, and the second output terminal of the control circuit 400 is electrically connected to the second liquid crystal film 600.

[0023] It is understood that in practical applications, the liquid crystal writing tablet also includes a bottom substrate 700 disposed below the second liquid crystal film 600, which is preferably black. Preferably, the first liquid crystal film 500 includes, from top to bottom, a writing liquid crystal film surface layer 510, a first ITO conductive layer 520, a first liquid crystal layer 530, and a second ITO conductive layer 540; the second liquid crystal film 600 includes, from top to bottom, a first PET material layer 610, a third ITO conductive layer 620, a second liquid crystal layer 630, a fourth ITO conductive layer 640, and a second PET material layer 650.

[0024] In this embodiment, when the liquid crystal writing tablet is in working state, if the first control component 100 is triggered, the control circuit 400 outputs a first control signal corresponding to the first control component 100, causing the second liquid crystal film 600 to enter a transparent state, and the new handwriting color on the liquid crystal writing tablet is the handwriting color displayed on the first liquid crystal film 500; if the second control component 200 is triggered, the control circuit 400 outputs a second control signal corresponding to the second control component 200, causing both the first liquid crystal film 500 and the second liquid crystal film 600 to return to their original states, and the new handwriting color on the liquid crystal writing tablet is the superposition of the handwriting color displayed on the first liquid crystal film 500 and the handwriting color displayed on the second liquid crystal film 600; if the third control component 300 is triggered, the control circuit 400 outputs a third control signal corresponding to the third control component 300, causing both the first liquid crystal film 500 and the second liquid crystal film 600 to enter a transparent state, and the handwriting on both the first liquid crystal film 500 and the second liquid crystal film 600 is cleared, and the liquid crystal writing tablet displays the color of the bottom substrate 700, i.e., black.

[0025] To better understand the technical solution of this utility model, a specific application scenario is provided below for supplementary explanation:

[0026] Here, the first control component 100 includes a writing button (see...) Figure 4 The writing button SW4 shown), and the second control component 200 include a label button (see...). Figure 4 The button marked SW3) and the third control component 300 include a one-touch clear button (see [reference]). Figure 4 As shown in the label button SW1), the first liquid crystal film 500 has a green handwriting color, and the second liquid crystal film 600 has a red handwriting color.

[0027] When a student needs to use this LCD writing tablet to write or answer questions, they trigger the writing button SW4. The control circuit 400 outputs an AC voltage to the second liquid crystal film 600, causing the second liquid crystal film 600 to enter a transparent state. Thus, the writing left by the student on the LCD writing tablet appears green.

[0028] When a teacher or parent needs to use this LCD writing tablet to annotate the student's writing, triggering the annotation button SW3 will cause the control circuit 400 to neither output AC voltage to the first liquid crystal film 500 nor the second liquid crystal film 600. Both the first and second liquid crystal films 500 will return to their original states. Thus, the writing left by the teacher or parent on the LCD writing tablet will be a superimposed color of green and red, i.e., yellow.

[0029] After the teacher / student / parent finishes using this LCD handwriting tablet, triggering the one-click clear button SW1 will cause the control circuit 400 to output AC voltage to the first liquid crystal film 500 and the second liquid crystal film 600, making both the first liquid crystal film 500 and the second liquid crystal film 600 transparent, thus completing the one-click clearing of the content written by the teacher / student / parent, which is very convenient.

[0030] It is understood that, in specific implementations, the writing colors of the first liquid crystal film 500 and the second liquid crystal film 600 can have multiple choices, and no limitation is made here. Similarly, there are multiple ways to achieve different writing colors for the first liquid crystal film 500 and the second liquid crystal film 600, and no limitation is made here either. The writing button SW4, annotation button SW3, and / or one-key clear button SW1 mentioned above can be mechanical buttons set on the liquid crystal handwriting tablet or operation buttons set on remote control devices. In an optional embodiment, the first control component 100, the second control component 200, and / or the third control component 300 have communication functions, which can receive control signals from external devices (such as electronic remote controls, smartphones), and complete triggering actions based on the control signals from external devices. In addition, when users, including students / teachers / parents, use this liquid crystal handwriting tablet, they can write content through the stylus 800, or directly with their fingers or other tools.

[0031] It is worth mentioning that, in order to indicate the working status of the first control component 100, the second control component 200 and / or the third control component 300, this LCD handwriting tablet is also equipped with an indicator component 900. This ensures that students write and teachers / parents annotate in an orderly manner and avoids accidentally deleting the writing on the LCD handwriting tablet.

[0032] To provide a more specific understanding of the technical solution of this utility model, the following is combined with... Figures 1 to 6 The present invention will be described in detail below:

[0033] In one embodiment, the control circuit 400 includes a power supply module (not shown), an MCU logic control circuit 460, and an output circuit (not shown). The first output terminal of the power supply module is connected to the power supply terminal of the output circuit, the controlled terminal of the power supply module is connected to the first control terminal of the MCU logic control circuit 460, the second control terminal of the MCU logic control circuit 460 is connected to the controlled terminal of the output circuit, the first output terminal of the output circuit is the first output terminal of the control circuit, and the second output terminal of the output circuit is the second output terminal of the control circuit.

[0034] The power module includes a charging interface 410, a charging circuit 420, an energy storage battery 430, and a switching boost circuit 450. The charging interface 410 is connected to the input terminal of the charging circuit 420, the output terminal of the charging circuit 420 is connected to the input terminal of the energy storage battery 430, and the output terminal of the energy storage battery 430 is connected to the input terminal of the switching boost circuit 450. The connection node is the first output terminal of the power module. The controlled terminal of the switching boost circuit 450 is the controlled terminal of the power module, and the output terminal of the switching boost circuit 450 is the first output terminal of the power module.

[0035] Here, the charging interface 410 is preferably a Type-C interface. In specific implementations, the charging interface type (such as a USB interface) can also be configured according to different charging standards / protocols to improve the applicability of this solution. The energy storage battery 430 is preferably a lithium battery. In specific implementations, the energy storage battery 430 can also be configured in other forms, such as nickel batteries, lead-mercury batteries, etc.

[0036] In implementing this solution, the power module can be connected to a charging power source via the charging interface 410. The energy storage battery 430 obtains and stores the charging power through the charging circuit 420 to provide power to the LCD handwriting tablet. In a preferred embodiment, the power module further includes a locking toggle switch 440, which is disposed between the energy storage battery 430 and the switching boost circuit 450, and connected in series with both the energy storage battery 430 and the switching boost circuit 450. It is easy to understand that when the LCD handwriting tablet is idle, cutting off the power supply path between the energy storage battery 430 and the switching boost circuit 450 by the locking toggle switch 440 can reduce system power loss.

[0037] In one specific embodiment, the switching boost circuit 450 includes capacitors C25, C26, C27, C28, and C30; resistors R65, R66, R68, R69, R70, R72, and R74; transistors Q8 and Q9; a boost chip U5; inductors LE1, LE4, and L4; and a Zener diode D3. The first terminal of capacitor C30, the first terminal of resistor R72, and the source of transistor Q8 are interconnected, forming the input terminal of the switching boost circuit 450. The second terminal of resistor R72, the gate of transistor Q8, and the drain of transistor Q9 are interconnected. The gate of transistor Q9 is connected to the first terminal of resistor R74, forming the controlled terminal of the switching boost circuit 450. The drain of transistor Q8, the first terminal of capacitor C27, and the first terminal of inductor LE4 are interconnected. The second terminal of inductor LE4, the first terminal of capacitor C26, the first terminal of inductor L4, and the boost chip... The VIN pin and EN pin of chip U5 are interconnected; the second terminal of inductor L4, the LX pin of boost chip U5, and the anode of Zener diode D3 are interconnected; the cathode of Zener diode D3, the first terminal of resistor R66, the first terminal of capacitor C25, the first terminal of resistor R68, and the first terminal of inductor LE1 are interconnected; the second terminals of resistor R66, the first terminal of resistor R65, the FB pin of boost chip U5, and the first terminal of resistor R69 are interconnected; the second terminal of resistor R69, the first terminal of capacitor C28, and the first terminal of resistor R70 are interconnected; the second terminal of capacitor C30, the source of transistor Q9, the second terminal of capacitor C27, the second terminal of capacitor C26, the GND pin of boost chip U5, the second terminals of resistor R65, capacitor C25, resistor R68, and capacitor C28 are grounded; the second terminal of inductor LE1 is the output terminal of the switching boost circuit 450; the second terminal of resistor R70 is used to receive power feedback control signals.

[0038] The MCU logic control circuit 460 includes a control chip U1, resistors R55, R54, R53, R52, R64, R34, R35, R58, R59, R27, R51, R36, R16, capacitors C37, C16, C14, and C32, and an inductor LE11. The first terminal of inductor LE11 is used to input the power supply to the control chip U1; the second terminal of inductor LE11, the first terminal of capacitor C37, the first terminal of capacitor C16, and the control chip... The VCC pin of U1 is interconnected with the ADC_VREF+ pin of control chip U1. Pin P5.4 of control chip U1 is connected to the second terminal of resistor R64, with the first terminal of resistor R64 used to output the power feedback control signal. Pin P1.7 of control chip U1 is connected to the second terminal of resistor R52, pin P1.6 of control chip U1 is connected to the second terminal of resistor R53, pin P1.3 of control chip U1 is connected to the second terminal of resistor R54, and pin P1.2 of control chip U1 is connected to the second terminal of resistor R55. This is the MCU logic control circuit. The second control terminal of 460 includes the first terminals of resistors R55, R54, R53, and R52; the P1.1 pin of control chip U1, the second terminal of capacitor C14, the second terminal of resistor R34, and the first terminal of resistor R35 are interconnected. The first terminal of resistor R34 is connected to the power supply. The P3.7 pin of control chip U1 is connected to the first terminal of resistor R58. The second terminal of resistor R58 is the first input terminal of the control circuit. The P3.6 pin of control chip U1 is connected to the first terminal of resistor R59. The second terminal is the second input terminal of the control circuit. The P3.5 pin of the control chip U1 is connected to the first terminal of the resistor R27. The second terminal of the resistor R27 is the first control terminal of the MCU logic control circuit 460. The P3.3 pin of the control chip U1 is connected to the first terminal of the resistor R51. The second terminal of the resistor R51 is the third input terminal of the control circuit. The P3.1 pin and the P3.0 pin of the control chip U1 are used to transmit software data. The capacitors C37, C16, the GND pin of the control chip U1, and the first terminal of the capacitor C14 are grounded.

[0039] The output circuit includes a first H-bridge circuit 470 and a second H-bridge circuit 480, which are independent of each other. The first H-bridge circuit 470 includes resistors R33, R37, R38, R39, R40, R42, R43, and R44, transistors Q10, Q11, and Q12. The first terminal of resistor R33, the first terminal of resistor R40, and the first drain of transistor Q10 are interconnected, and their connection node is the first sub-output terminal of the first H-bridge circuit 470. The second terminal of resistor R33, the first terminal of resistor R44, and the first drain of transistor Q11 are interconnected, and their connection node is the second sub-output terminal of the first H-bridge circuit 470. The first output terminal of the output circuit includes the first sub-output terminal and the second sub-output terminal of the first H-bridge circuit 470. The second terminal of resistor R40 is connected to the second drain of transistor Q10, and the first source of transistor Q10 is connected to the second terminal of resistor R43. Their connection node is used to input the power supply output by the power module. The second gate of transistor Q10 and the first drain of resistor R43 are connected to the second drain of transistor Q10. The first terminal of resistor R42 is interconnected with the second terminal of transistor Q11; the second terminal of resistor R44 is connected to the second drain of transistor Q11, and the first source of transistor Q11 is connected to the first terminal of resistor R39. The connection is used to input the power supply output of the power module; the first gate of transistor Q11, the second terminal of resistor R39, and the first terminal of resistor R38 are interconnected; the first gate of transistor Q10, the second terminal of resistor R37, and the first gate of transistor Q12 are interconnected, and their connection node is the second sub-input terminal of the first H-bridge circuit 470; the second gate of transistor Q11, the first terminal of resistor R41, and the second gate of transistor Q12 are interconnected, and their connection node is the first sub-input terminal of the first H-bridge circuit 470; the second drain of transistor Q12 is connected to the second terminal of resistor R42, and the first drain of transistor Q12 is connected to the second terminal of resistor R38; the first source of transistor Q10, the second source of transistor Q11, the first source of transistor Q12, the second source of transistor Q12, the first terminal of resistor R37, and the second terminal of resistor R41 are grounded.

[0040] In an optional embodiment, the circuit structure of the second H-bridge is the same as that of the first H-bridge, and the repeated parts will not be described again here.

[0041] The following, combined with Figures 1 to 6 Explain the working principle of this LCD handwriting tablet:

[0042] 1. The MCU logic control circuit 460 has three main functions: first, to receive signals input from control component 1, control component 2 and control component 3; second, to output PWM1 and PWM2 control signals to the first H-bridge circuit 470, and to output PWM3, PWM4 and the second H-bridge circuit 480; and third, to control the indicator component 900 (such as LED indicator lights).

[0043] 2. Charging port 410: It serves as the charging port for the energy storage battery 430 (such as a lithium battery).

[0044] 3. Charging circuit 420: mainly composed of a dedicated charging chip (not shown in the figure) to ensure proper charging of the energy storage battery 430.

[0045] 4. Lithium battery: mainly provides power, with a preferred voltage of 3.7V (maximum 4.2V).

[0046] 5. Locking toggle switch 440: When this switch is locked, the one-click erasure function cannot be performed. After unlocking, the one-click erasure function can be performed.

[0047] 6. Switching boost circuit 450: mainly boosts the voltage of the energy storage battery 430 to the voltage required for erasing the first liquid crystal film 500 and the second liquid crystal film 600. The output voltage can be controlled by the MCU logic control circuit 460.

[0048] 7. The first H-bridge circuit 470 and the second H-bridge circuit 480 are mainly full-bridge circuits composed of field-effect transistors or transistors. Under the control of the PWM1, PWM2, PWM3 and PWM4 signals output by the MCU logic control circuit 460, two sets of AC drive square waves can be obtained respectively. These drive square wave signals will be connected to the first liquid crystal film 500 and the second liquid crystal film 600 respectively.

[0049] 8. First liquid crystal film 500 (optional green), second liquid crystal film 600 (optional red): When these two liquid crystal films receive the driving square waves of the first H-bridge circuit 470 and the second H-bridge circuit 480 respectively, the pen marks on the corresponding films can be erased.

[0050] 9. The first control component 100, taking the writing button as an example, after pressing this button, the writing marks change to the writing color (e.g., green).

[0051] 10. Second control component 200, taking the annotation button as an example, after pressing this button, the written handwriting changes to the annotation color (e.g., yellow).

[0052] 11. The third control component 300, taking the one-click erase button as an example, will erase the written marks (e.g., green) and the marked marks (e.g., yellow) with one click after pressing this button.

[0053] 12. Indicator component 900, taking the indicator component 900 as an example, consists of green and orange (or yellow) LEDs. When the writing button is pressed, the LEDs will display green, indicating that the writing is green. When the annotation button is pressed, the LEDs will display orange (or yellow), indicating that the annotation or correction is yellow (or other specific color).

[0054] Specifically, when the user presses the "Write Button SW4", the LED indicator turns green. The MCU logic control circuit 460 sends PWM3 and PWM4 signals to the second H-bridge circuit 480, while the first H-bridge circuit 470 does not send a PWM signal. The high voltage output from the lithium battery under the control of the switching boost circuit 450 is input to the second H-bridge circuit 480. The second H-bridge circuit 480 then outputs a high-voltage AC drive square wave, which is applied to the second liquid crystal film 600 (e.g., red). In this way, the user's handwriting will be erased from the second liquid crystal film 600 without leaving any trace. Only the first liquid crystal film 500 (e.g., green) will produce green handwriting. Overall, the handwriting tablet displays green. When the user presses the "Annotation Button SW3", the LED indicator turns orange (or yellow). The MCU logic control circuit 460 stops sending PWM3 and PWM4 signals to the second H-bridge circuit 480, and also turns off the switching boost circuit 450. As a result, there are no AC drive square wave signals on the first liquid crystal film 500 and the second liquid crystal film 600. At this time, the writing pen will simultaneously produce writing on the first liquid crystal film 500 and the second liquid crystal film 600. Since the green and red writing are superimposed, they become yellow. In terms of the overall display effect, the handwriting tablet displays yellow, which is the annotation color writing. When the user presses the one-key clear button SW1, the MCU logic control circuit 460 simultaneously sends PWM1, PWM2, PWM3, and PWM4 signals to the first H-bridge circuit 470 and the second H-bridge circuit 480. The high voltage output by the lithium battery under the control of the switching boost circuit 450 is input to the first H-bridge circuit 470 and the second H-bridge circuit 480. As a result, the first H-bridge circuit 470 and the second H-bridge circuit 480 output a high-voltage AC drive square wave, which is then applied to the first liquid crystal film 500 and the second liquid crystal film 600. In this way, the handwriting written by the user is erased from both the first liquid crystal film 500 and the second liquid crystal film 600, and the handwriting tablet completes the one-key clear function.

[0055] about Figure 4U1 is the MCU logic control chip. Pin P1.1 of U1 and resistor R55 form the PWM1 control signal, and pin P1.2 of U1 and resistor R54 form the PWM2 control signal, which are provided to the first H-bridge circuit 470 (connected to the green LCD). Pin P1.6 of U1 and resistor R53 form the PWM4 control signal, and pin P1.6 of U1 and resistor R52 form the PWM3 control signal, which are provided to the second H-bridge circuit 480 (connected to the red LCD). Pin P5.4 of U1 outputs an HV-PWM signal (i.e., the aforementioned power feedback control signal). This signal is input to the feedback pin of the switching boost circuit 450 (i.e., the second end of the aforementioned resistor R70) to control and generate the required control voltage, such as the driving wave voltage applied to the second LCD 600 (red LCD) or the erasure voltage required for one-key erasure. Generally, the one-key erasure voltage is higher than that applied to the second LCD 600 (writing mode). The VCC and ADC_VREF+ pins of U1 are connected to the power supply VCC (typically 3.0–5.0V). C37 and C16 are filter capacitors used to filter the voltage applied to the VCC and ADC_VREF+ pins. The TXD and RXD pins of U1 are serial port signal pins, connected to connector J1 to form a software download port for software download and updates. The P3.3 pin of U1 is connected to switch SW1 through resistor R51. SW1 is set as a one-key clear button. When this button is pressed, the P3.3 pin of U1 changes from high to low, thus notifying U1 to perform a one-key erase operation. The P1.0 pin of U1 is connected to orange (or yellow) and green LEDs through resistor R14 and resistor R57 through resistor R57. When the write button is pressed, the level of the P3.4 pin of U1 goes low, and the green LED lights up to indicate that the writing mode is now active. When pin P1.0 of U1 goes low, the orange (or yellow) LED will light up. When both LEDs are lit and flashing simultaneously, it indicates that a one-key erase operation is in progress. Pin P3.5 of U1 is the HV-ONOFF signal pin. When the handwriting tablet has been inactive for a certain period of time, HV-ONOFF will output a low-level signal, thus turning off the 450 switching boost circuit to save power. Pin P3.6 of U1 is connected to the annotation button SW3 through resistor R59. Pressing this button will turn the pen writing yellow. Pin P3.7 of U1 is connected to the writing button SW4 through resistor R58. Pressing this button will turn the pen writing green (red LCD film plus a driving square wave signal).The P1.1 pin of U1 is the battery voltage detection pin, which consists of resistors R34 and R35 and capacitor C14. One end of R34 is connected to the battery, and R34 and R35 are connected in series and connected to the P1.1 pin of U1 in the middle. C14 is a filter capacitor to prevent instantaneous high voltage such as electrostatic discharge from damaging U1. When the battery voltage is lower than a certain value, the P1.1 pin of U1 will receive the lower limit voltage. After ADC conversion, U1 will control the LED to flash, indicating to the user that the battery voltage is low and needs to be charged.

[0056] about Figure 5 It mainly consists of components such as U5, L4, D3, R66, R65, and filter capacitors. Q8, Q9, R72, R74, and C30 form the power-on / off circuit (not shown in the diagram). To save power, after the user has not used the handwriting tablet for a period of time, U1 sends a low level through the HV-ONOFF signal line to shut down the voltage input of the boost circuit, achieving a power-saving effect. LE4, C27, and C26 form the power supply energy storage capacitor, which filters and stores energy for the MAIN_PWR input voltage. The LX pin of U5 is connected to the second terminal of inductor L4. Driven by the high-speed control signal inside U5, the voltage is rectified by rectifier diode D3, generating a high voltage across capacitor C25. Resistors R66 and R65 are connected in series to form a voltage output feedback network. The intermediate node of the resistor is connected to the FB pin (feedback pin) of U5 to achieve a set output voltage. R68 is a load resistor used for fast discharge and voltage regulation. LE1 is a ferrite bead, mainly used to reduce electromagnetic interference signals generated by oscillation on L4 that are transmitted to subsequent circuits. The voltage control signal HV-PWM of U1 is applied to the FB pin of U5 through resistors R70, C28, and R69. When different output voltages are required, the output voltage (i.e., HVOUT as shown in the diagram) can be controlled by adjusting the PWM duty cycle of the control signal HV-PWM through U1. For example, when the user presses the one-key clear button, HVOUT requires a higher clear voltage. At this time, U1 outputs a signal with a lower duty cycle, and the voltage drop at the FB pin of U5 will cause the output voltage to rise.

[0057] about Figure 6It includes two H-bridge circuits, each composed of six field-effect transistors or transistors. The two H-bridge circuits are connected to the green and red liquid crystal films respectively. The corresponding H-bridge is driven based on whether the user presses the "writing button SW4", "annotation button SW3", or "one-key clear button SW1". In the first H-bridge circuit 470, PWM1 and PWM2 are connected to the gate control pins of Q10, Q11, and Q12 respectively. The high voltage HVOUT output from the switching boost circuit 450 is connected to the drains of Q10 and Q11. R43 and R39 are pull-up resistors, and R41 and R37 are pull-down resistors for PWM1 and PWM2, providing pull-down discharge. R33 is a discharge resistor, which discharges the film when the drive voltage is turned off. R40 and R44 are current-limiting resistors to prevent large currents from being generated when the film is energized.

[0058] In the second H-bridge circuit 480, PWM3 and PWM4 are connected to the gate control pins of Q13, Q14, and Q15 respectively. The high voltage HVOUT output from the boost circuit is connected to the drain of Q13 and Q14. R26 and R19 are pull-up resistors, and R21 and R17 are pull-down resistors for PWM3 and PWM4, providing pull-down discharge. R15 is a discharge resistor, which discharges the diaphragm when the drive voltage is off. R20 and R28 are current-limiting resistors to prevent a large current from being generated when the diaphragm is energized. The working principle of the first H-bridge circuit 470 is as follows: when PWM1 is high, PWM2 is low, the N-channel MOSFET on the left side of Q12 is turned on, and the N-channel MOSFET on the right side of Q12 is not turned on. When the gate of the P-channel MOSFET in Q10 is low, the voltage HVOUT flows from the source to the drain of the P-channel MOSFET. The drain voltage then flows through the liquid crystal film and through the current-limiting resistor R44 to the drain of the N-channel MOSFET in Q11. Since PWM1 is high, the source of the MOSFET in Q11 also conducts, forming a complete current loop and applying voltage to the film. At another moment, when PWM1 goes low and PWM2 goes high, the same principle applies: the HVOUT voltage flows from the source to the drain of the P-channel MOSFET in Q11, through the film, to the current-limiting resistor R40, and then through the drain of the N-channel MOSFET in Q10 back to its source, forming a complete loop and applying voltage to the film. This generates a positive and negative square wave drive voltage for one cycle on the film, thus clearing the liquid crystal film connected to H-bridge 1. Similarly, the H-bridge 2 circuit can also apply a drive voltage according to the MCU's control.

[0059] Under the control of these circuits, the circuit of this invention achieves separate control of the two liquid crystal films. In writing mode, a driving voltage is applied to the red liquid crystal film to obtain green writing marks. In annotation mode, the circuit cancels the voltage applied to the red liquid crystal film, so green + red are superimposed to obtain yellow writing marks. In one-key clear mode, the circuit applies a high AC driving voltage to both the green and red liquid crystal films simultaneously, thereby clearing all writing marks (yellow + green).

[0060] It should be noted that the technical solutions of the various embodiments of this utility model can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0061] The above description is only a part or preferred embodiment of this utility model. Neither the text nor the drawings should limit the scope of protection of this utility model. All equivalent structural transformations made using the content of this utility model specification and drawings under the overall concept of this utility model, or direct / indirect applications in other related technical fields, are included within the scope of protection of this utility model.

Claims

1. A liquid crystal handwriting tablet, characterized in that, It includes a control circuit, a first control component, a second control component, a third control component, and a first liquid crystal film and a second liquid crystal film arranged sequentially from top to bottom; The first input terminal of the control circuit is electrically connected to the first control component, the second input terminal of the control circuit is electrically connected to the second control component, the third input terminal of the control circuit is electrically connected to the third control component, the first output terminal of the control circuit is electrically connected to the first liquid crystal film, and the second output terminal of the control circuit is electrically connected to the second liquid crystal film.

2. The liquid crystal handwriting tablet as described in claim 1, characterized in that, The control circuit includes a power module, an MCU logic control circuit, and an output circuit. The first output terminal of the power module is connected to the power terminal of the output circuit, the controlled terminal of the power module is connected to the first control terminal of the MCU logic control circuit, the second control terminal of the MCU logic control circuit is connected to the controlled terminal of the output circuit, the first output terminal of the output circuit is the first output terminal of the control circuit, and the second output terminal of the output circuit is the second output terminal of the control circuit.

3. The liquid crystal handwriting tablet as described in claim 2, characterized in that, The power module includes a charging interface, a charging circuit, an energy storage battery, and a switching boost circuit. The charging interface is connected to the input terminal of the charging circuit, the output terminal of the charging circuit is connected to the input terminal of the energy storage battery, and the output terminal of the energy storage battery is connected to the input terminal of the switching boost circuit. The connection node is the first output terminal of the power module. The controlled terminal of the switching boost circuit is the controlled terminal of the power module, and the output terminal of the switching boost circuit is the first output terminal of the power module.

4. The liquid crystal handwriting tablet as described in claim 3, characterized in that, The switching boost circuit includes capacitors C25, C26, C27, C28, and C30; resistors R65, R66, R68, R69, R70, R72, and R74; transistors Q8 and Q9; boost chip U5; inductors LE1, LE4, and L4; and Zener diode D3. The first terminal of capacitor C30, the first terminal of resistor R72, and the source of transistor Q8 are interconnected, and their connection node is the input terminal of the switching boost circuit; the second terminal of resistor R72, the gate of transistor Q8, and the drain of transistor Q9 are interconnected, and the gate of transistor Q9 is connected to the first terminal of resistor R74, and their connection node is the controlled terminal of the switching boost circuit. The drain of transistor Q8, the first terminal of capacitor C27, and the first terminal of inductor LE4 are interconnected; the second terminal of inductor LE4, the first terminal of capacitor C26, the first terminal of inductor L4, the VIN pin of boost chip U5, and the EN pin of boost chip U5 are interconnected; the second terminal of inductor L4, the LX pin of boost chip U5, and the anode of Zener diode D3 are interconnected; the cathode of Zener diode D3, the first terminal of resistor R66, the first terminal of capacitor C25, the first terminal of resistor R68, and the first terminal of inductor LE1 are interconnected; the second terminal of resistor R66, the first terminal of resistor R65, the FB pin of boost chip U5, and the first terminal of resistor R69 are interconnected. The second terminal of resistor R69, the first terminal of capacitor C28, and the first terminal of resistor R70 are interconnected. The second terminal of capacitor C30, the source of transistor Q9, the second terminal of capacitor C27, the second terminal of capacitor C26, the GND pin of boost chip U5, the second terminal of resistor R65, the second terminal of capacitor C25, the second terminal of resistor R68, and the second terminal of capacitor C28 are grounded. The second terminal of the inductor LE1 is the output terminal of the switching boost circuit, and the second terminal of the resistor R70 is used to receive the power feedback control signal.

5. The liquid crystal handwriting tablet as described in claim 3, characterized in that, The power module also includes a locking toggle switch, which is disposed between the energy storage battery and the switching boost circuit, and is connected in series with the energy storage battery and the switching boost circuit.

6. The liquid crystal handwriting tablet as described in claim 2, characterized in that, The MCU logic control circuit includes a control chip U1, resistors R55, R54, R53, R52, R64, R34, R35, R58, R59, R27, R51, R36, R16, capacitors C37, C16, C14, C32, and inductor LE11. The first terminal of the inductor LE11 is used to input the power supply of the control chip U1. The second terminal of the inductor LE11, the first terminal of the capacitor C37, the first terminal of the capacitor C16, the VCC pin of the control chip U1, and the ADC_VREF+ pin of the control chip U1 are interconnected. The P5.4 pin of the control chip U1 is connected to the second terminal of the resistor R64. The first terminal of the resistor R64 is used to output the power feedback control signal. The P1.7 pin of the control chip U1 is connected to the second terminal of the resistor R52, the P1.6 pin of the control chip U1 is connected to the second terminal of the resistor R53, the P1.3 pin of the control chip U1 is connected to the second terminal of the resistor R54, and the P1.2 pin of the control chip U1 is connected to the second terminal of the resistor R55. The second control terminal of the MCU logic control circuit includes the first terminal of the resistor R55, the first terminal of the resistor R54, the first terminal of the resistor R53, and the first terminal of the resistor R52. The P1.1 pin of the control chip U1, the second terminal of the capacitor C14, the second terminal of the resistor R34, and the first terminal of the resistor R35 are interconnected. The first terminal of the resistor R34 is connected to the power supply. The P3.7 pin of the control chip U1 is connected to the first terminal of the resistor R58. The second terminal of the resistor R58 is the first input terminal of the control circuit. The P3.6 pin of the control chip U1 is connected to the first terminal of the resistor R59. The second terminal of the resistor R59 is the second input terminal of the control circuit. The P3.5 pin of the control chip U1 is connected to the first terminal of the resistor R27. The second terminal of the resistor R27 is the first control terminal of the MCU logic control circuit. The P3.3 pin of the control chip U1 is connected to the first terminal of the resistor R51. The second terminal of the resistor R51 is the third input terminal of the control circuit. The P3.1 pin and the P3.0 pin of the control chip U1 are used to transmit software data. The capacitors C37, C16, the GND pin of the control chip U1, and the first end of the capacitor C14 are grounded.

7. The liquid crystal handwriting tablet as described in claim 2, characterized in that, The output circuit includes a first H-bridge circuit and a second H-bridge circuit that are independent of each other. The first H-bridge circuit includes resistors R33, R37, R38, R39, R40, R41, R42, R43, R44, transistor Q10, transistor Q11, and transistor Q12. The first terminal of resistor R33, the first terminal of resistor R40, and the first drain of transistor Q10 are interconnected, and their connection node is the first sub-output terminal of the first H-bridge circuit; the second terminal of resistor R33, the first terminal of resistor R44, and the first drain of transistor Q11 are interconnected, and their connection node is the second sub-output terminal of the first H-bridge circuit. The first output terminal of the output circuit includes the first sub-output terminal and the second sub-output terminal of the first H-bridge circuit. The second terminal of resistor R40 is connected to the second drain of transistor Q10, and the first source of transistor Q10 is connected to the second terminal of resistor R43. This connection is used to input the power supply output from the power module. The second gate of transistor Q10, the first terminal of resistor R43, and the first terminal of resistor R42 are interconnected. The second terminal of resistor R44 is connected to the second drain of transistor Q11, and the first source of transistor Q11 is connected to the first terminal of resistor R39. This connection is used to input the power supply output from the power module. The first gate of transistor Q11, the second terminal of resistor R39, and the first terminal of resistor R38 are interconnected. The first gate of transistor Q10, the second terminal of resistor R37, and the first gate of transistor Q12 are interconnected, and their connection node is the second sub-input terminal of the first H-bridge circuit. The second gate of transistor Q11, the first terminal of resistor R41, and the second gate of transistor Q12 are interconnected, and their connection node is the first sub-input terminal of the first H-bridge circuit. The second drain of transistor Q12 is connected to the second terminal of resistor R42, the first drain of transistor Q12 is connected to the second terminal of resistor R38, and the first source of transistor Q10, the second source of transistor Q11, the first source of transistor Q12, the second source of transistor Q12, the first terminal of resistor R37, and the second terminal of resistor R41 are grounded.

8. The liquid crystal handwriting tablet as described in claim 1, characterized in that, The first liquid crystal film includes, from top to bottom, a writing liquid crystal film surface layer, a first ITO conductive layer, a first liquid crystal layer, and a second ITO conductive layer.

9. The liquid crystal handwriting tablet as described in claim 1, characterized in that, The second liquid crystal film includes, from top to bottom, a first PET material layer, a third ITO conductive layer, a second liquid crystal layer, a fourth ITO conductive layer, and a second PET material layer.

10. The liquid crystal handwriting tablet as described in any one of claims 1-9, characterized in that, The LCD handwriting tablet also includes an indicator component, which is electrically connected to the control circuit and is used to indicate the working status of the first control component, the second control component, and / or the third control component.

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