Negative voltage driving circuit and blackboard eraser

Abstract

The application discloses a negative voltage driving circuit and a blackboard eraser. The negative voltage driving circuit comprises a temperature sensing circuit, a micro control unit and a negative voltage control unit. The temperature sensing circuit is used for outputting an analog voltage signal. The micro control unit is electrically connected to the temperature sensing circuit. The micro control unit receives the analog voltage signal to generate a control level signal. The negative voltage control unit is electrically connected to the micro control unit. The negative voltage control unit receives the control level signal and outputs a feedback control signal.

Description

Technical Field

[0001] This application relates to the field of liquid crystal film driving technology, and in particular to a negative voltage driving circuit and a local eraser. Background Technology

[0002] To address the dust problem associated with traditional blackboards, a new type of LCD writing blackboard has emerged on the market. This type of LCD writing board uses a liquid crystal film as the writing substrate. Because the liquid crystal used has the characteristic that both the reflective and scattering states are stable, users can write freely on the LCD writing board using a hard object. The writing experience is consistent with that of writing on paper, which not only solves the dust problem of traditional blackboards but also protects the eyes.

[0003] like Figure 1 As shown, the driving voltage of a liquid crystal film often needs to be adjusted with temperature. As temperature rises, the activity of the liquid crystal gradually increases, and the driving voltage of the liquid crystal film decreases accordingly. In the hot summer, due to the increased activity of the liquid crystal at high temperatures, crosstalk will occur if the driving voltage is not reduced. Crosstalk means that in addition to erasing the desired area, it will also erase or blur the writing in adjacent areas. In winter, the activity of the liquid crystal decreases, and if the driving voltage is not increased, some areas will not be completely erased, or multiple erasures will be required to achieve a clean result, greatly reducing the user experience.

[0004] Currently, most local blackboard erasing methods rely on manual voltage adjustment: lowering the driving voltage in summer and raising it in winter to achieve a satisfactory erasing effect. This method is cumbersome for manufacturers; therefore, there is an urgent need for a technology that can adjust the driving voltage of the liquid crystal film based on temperature. Utility Model Content

[0005] The main objective of this application is to propose a negative voltage driving circuit and a partial erasing blackboard, which aims to solve the technical problem that the driving voltage of the liquid crystal film of the partial erasing blackboard is difficult to adjust according to temperature.

[0006] To achieve the above objectives, this application proposes a negative voltage driving circuit for use on a local blackboard eraser, comprising: A temperature sensing circuit includes a first resistor, a thermistor, and a first node. The first end of the first resistor is used to connect to a first power signal, and the second end of the first resistor is electrically connected to the first node. The first end of the thermistor is electrically connected to the first node, and the second end of the thermistor is electrically connected to a working ground terminal. The first node is used to output an analog voltage signal. A microcontroller unit, electrically connected to the first node, receives the analog voltage signal to generate a control level signal; and A negative voltage control unit is electrically connected to the microcontroller unit. The negative voltage control unit receives the control level signal and outputs a feedback control signal.

[0007] In some embodiments of this application, the temperature sensing circuit includes a filtering unit, the first terminal of which is electrically connected to the first node, and the second terminal of which is electrically connected to the working ground terminal.

[0008] In some embodiments of this application, the filtering unit includes a first capacitor, a first terminal of which is electrically connected to the first node, and a second terminal of which is electrically connected to the working ground terminal.

[0009] In some embodiments of this application, the negative voltage control unit includes multiple liquid crystal negative voltage control circuits, a second node, a third node, and a feedback resistor; The liquid crystal negative voltage control circuit is electrically connected to the microcontroller unit, the second node, and the third node; the first end of the feedback resistor is electrically connected to the second node, and the second end of the feedback resistor is electrically connected to the third node. The microcontroller receives the analog voltage signal to generate multiple control level signals, and the liquid crystal negative voltage control circuit corresponds one-to-one with the control level signals; each liquid crystal negative voltage control circuit receives the corresponding control level signal and adjusts the impedance between the second node and the third node. After the multiple liquid crystal negative voltage control circuits superimpose and adjust the impedance between the second node and the third node, the second node outputs the feedback control signal. The third node is used to output a negative voltage signal.

[0010] In some embodiments of this application, the liquid crystal negative voltage control circuit includes a first field-effect transistor, a second field-effect transistor, a third field-effect transistor, a second resistor, a third resistor, a first pull-down resistor, a second pull-down resistor, and a pull-up resistor; The control electrode of the first field-effect transistor (FET) is electrically connected to the microcontroller unit. The control electrode of the first FET is used to receive the control level signal. The source electrode of the first FET is electrically connected to the working ground terminal. The drain electrode of the first FET is electrically connected to the second FET. When the control electrode of the first FET is at a high level, the source and drain of the first FET are connected. When the control electrode of the first FET is at a low level, the source and drain of the first FET are disconnected. The control electrode of the second field-effect transistor is electrically connected to the drain of the first field-effect transistor. The source of the second field-effect transistor receives a second power supply signal, and the drain of the second field-effect transistor is electrically connected to the first terminal of the second resistor. When the control electrode of the second field-effect transistor is at a low level, the source and drain of the second field-effect transistor are connected. When the control electrode of the second field-effect transistor is at a high level, the source and drain of the second field-effect transistor are disconnected. The control electrode of the third field-effect transistor is electrically connected to the second terminal of the second resistor, the source electrode of the third field-effect transistor is electrically connected to the third node, the drain electrode of the third field-effect transistor is electrically connected to the first terminal of the third resistor, and the second terminal of the third resistor is electrically connected to the second node; when the control electrode of the third field-effect transistor is high, the source and drain of the third field-effect transistor are connected; when the control electrode of the third field-effect transistor is low, the source and drain of the third field-effect transistor are disconnected. The first terminal of the first pull-down resistor is electrically connected to the control terminal of the first field-effect transistor, and the second terminal of the first pull-down resistor is electrically connected to the source terminal of the first field-effect transistor. The first end of the pull-up resistor is electrically connected to the source of the second field-effect transistor, and the second end of the pull-up resistor is electrically connected to the control terminal of the second field-effect transistor. The first terminal of the second pull-down resistor is electrically connected to the control terminal of the third field-effect transistor, and the second terminal of the second pull-down resistor is electrically connected to the source terminal of the third field-effect transistor.

[0011] In some embodiments of this application, the negative voltage control unit further includes a fourth resistor, the first end of which is electrically connected to the second node, and the second end of which is electrically connected to the working ground terminal.

[0012] In some embodiments of this application, the negative voltage control unit further includes a second capacitor, the first terminal of which is electrically connected to the third node, and the second terminal of which is electrically connected to the working ground terminal.

[0013] In some embodiments of this application, the negative voltage driving circuit further includes: An infrared sensor circuit is electrically connected to the microcontroller unit. The infrared sensor circuit is used to acquire the coordinate position information of the part to be erased and transmit the coordinate position information to the microcontroller unit. A negative voltage generating circuit is electrically connected to the second node. The negative voltage generating circuit receives the feedback control signal and performs voltage regulation processing on the negative voltage signal. A liquid crystal bias voltage generating circuit is electrically connected to the negative voltage generating circuit. The liquid crystal bias voltage generating circuit receives the negative voltage signal after voltage regulation and converts it into a liquid crystal driving voltage. A liquid crystal driving chip circuit is electrically connected to the microcontroller unit and the liquid crystal bias voltage generating circuit. The microcontroller unit transmits the coordinate position information to the liquid crystal driving chip circuit. The liquid crystal driving chip circuit receives the liquid crystal driving voltage and drives the liquid crystal at the corresponding coordinate position to deflect. The power conversion circuit is electrically connected to the microcontroller unit, the negative voltage control unit, the negative voltage generating circuit, the liquid crystal bias voltage generating circuit, and the liquid crystal driver chip circuit. The power conversion circuit is used to supply power.

[0014] This application also proposes a partial eraser blackboard, including the aforementioned negative voltage drive circuit.

[0015] Compared with the prior art, the beneficial effects of the technical solution of this application are as follows: The negative voltage driving circuit includes a temperature sensing circuit. The resistance of the thermistor in the temperature sensing circuit changes with temperature, causing the voltage of the first node to change with temperature as well. The microcontroller controls the voltage of the first node and outputs a control level signal. The control level signal is used to control the negative voltage control unit to output a feedback control signal. The feedback control signal can adjust the magnitude of the driving voltage of the liquid crystal film, so that the driving voltage of the liquid crystal film is adjusted according to the temperature. Attached Figure Description

[0016] Figure 1 This is a reference curve showing the driving voltage and temperature of the liquid crystal film. Figure 2 This is a schematic diagram of the negative voltage driving circuit according to an embodiment of this application; Figure 3 This is a circuit diagram of the temperature sensing circuit according to an embodiment of this application; Figure 4 This is a reference curve of the resistance and temperature of the thermistor in an embodiment of this application. Figure 5 This is a circuit diagram of the negative voltage control unit and the negative voltage generating circuit according to an embodiment of this application; Figure 6 This is a schematic diagram illustrating the principle of the blackboard erasing method in an embodiment of this application; Figure 7 This is a schematic diagram of erasing a blackboard according to an embodiment of this application.

[0017] Explanation of reference numerals in the attached figures: 100 - Temperature sensing circuit, R1 - First resistor, RT - Thermistor, L1 - First node, 110 - Filter unit, C1 - First capacitor, 200 - Microcontroller unit, 300 - Negative voltage control unit, 310 - Liquid crystal negative voltage control circuit, Q1 - First field-effect transistor, Q2 - Second field-effect transistor, Q3 - Third field-effect transistor, R2 - Second resistor, R3 - Third resistor, Rd1 - First pull-down resistor, Rd2 - Second pull-down resistor, Ru - Pull-up resistor, L2 - Second node, L3 - Third node, Rf - Feedback resistor, R4 - Fourth resistor, C2 - Second capacitor, 400 - Infrared sensor circuit, 500 - Negative voltage generation circuit, 600 - LCD bias voltage generation circuit, 700 - LCD driver chip circuit, 800 - Power conversion circuit, 900 - Local eraser, GND - Working ground terminal, V1 - First power signal, V2 - Second power signal, V3 - Analog voltage signal, V4 - Control level signal, VFB - Feedback control signal, VOUT - Negative voltage signal. Detailed Implementation

[0018] The solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments in this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] Please see Figure 2 This application provides a negative voltage driving circuit for use in local blackboard erasing. The negative voltage driving circuit includes a temperature sensing circuit 100, a microcontroller unit (MCU) 200, and a negative voltage control unit 300.

[0020] Combining 2 and Figure 3 The temperature sensing circuit 100 includes a first resistor R1, a thermistor RT, and a first node L1. The first end of the first resistor R1 is used to connect to a first power signal V1, and the second end of the first resistor R1 is electrically connected to the first node L1. The first end of the thermistor RT is electrically connected to the first node L1, and the second end of the thermistor RT is electrically connected to the working ground terminal GND. The first node L1 is used to output an analog voltage signal V3. In this embodiment, combined with... Figure 3 and Figure 4 The resistance of the thermistor RT changes with temperature, causing the voltage at the first node L1 to also change with temperature.

[0021] Combination Figure 2 , Figure 3 and Figure 5The microcontroller unit 200 is electrically connected to the first node L1. The microcontroller unit 200 receives the analog voltage signal V3 to generate the control level signal V4.

[0022] The negative voltage control unit 300 is electrically connected to the microcontroller unit 200. The negative voltage control unit 300 receives the control level signal V4 and outputs the feedback control signal VFB.

[0023] Combination Figures 2 to 4 The negative voltage driving circuit of this application includes a temperature sensing circuit 100. The resistance of the thermistor RT in the temperature sensing circuit 100 changes with the temperature, causing the voltage of the first node L1 to also change with the temperature. The microcontroller unit 200 outputs a control level signal V4 based on the voltage of the first node L1. The control level signal V4 is used to control the negative voltage control unit 300 to output a feedback control signal VFB. The feedback control signal VFB can adjust the magnitude of the driving voltage of the liquid crystal film, so that the driving voltage of the liquid crystal film is adjusted according to the temperature.

[0024] Specifically, such as Figure 3 As shown, the temperature sensing circuit 100 includes a filter unit 110. The first terminal of the filter unit 110 is electrically connected to the first node L1, and the second terminal of the filter unit 110 is electrically connected to the working ground terminal GND. The filter unit 110 can filter and stabilize the voltage, which is beneficial to the stable output of the analog voltage signal V3 from the first node L1.

[0025] Specifically, such as Figure 3 As shown, the filter unit 110 includes a first capacitor C1, the first end of the first capacitor C1 is electrically connected to the first node L1, and the second end of the first capacitor C1 is electrically connected to the working ground terminal GND.

[0026] Specifically, in combination Figure 2 and Figure 5 The negative voltage control unit 300 includes multiple liquid crystal negative voltage control circuits 310, a second node L2, a third node L3, and a feedback resistor Rf.

[0027] The liquid crystal negative voltage control circuit 310 is electrically connected to the microcontroller unit 200, the second node L2, and the third node L3; the first end of the feedback resistor Rf is electrically connected to the second node L2, and the second end of the feedback resistor Rf is electrically connected to the third node L3.

[0028] The microcontroller unit 200 receives an analog voltage signal V3 to generate multiple control level signals V4. A liquid crystal negative voltage control circuit 310 corresponds one-to-one with each control level signal V4. Each liquid crystal negative voltage control circuit 310 receives its corresponding control level signal V4 and adjusts the impedance between the second node L2 and the third node L3.

[0029] After the multiple liquid crystal negative voltage control circuits 310 superimpose and adjust the impedance between the second node L2 and the third node L3, the second node L2 outputs a feedback control signal VFB.

[0030] The third node L3 is used to output the negative voltage signal VOUT.

[0031] The microcontroller unit 200 adjusts the impedance between the second node L2 and the third node L3 through multiple liquid crystal negative voltage control circuits 310. Specifically, each liquid crystal negative voltage control circuit 310 corresponds to a control level signal V4. Each liquid crystal negative voltage control circuit 310 controls the impedance between the second node L2 and the third node L3 by a control level signal V4. Under the superimposed adjustment of multiple liquid crystal negative voltage control circuits 310, the second node L2 outputs a feedback control signal VFB. The feedback control signal VFB can adjust the driving voltage, so that the driving voltage of the liquid crystal film is adjusted according to the temperature.

[0032] In the embodiments of this application, such as Figure 5 As shown, the negative voltage control unit 300 includes n liquid crystal negative voltage control circuits 310, where n is an integer greater than 2. The impedance between the second node L2 and the third node L3 can be controlled by the n liquid crystal negative voltage control circuits 310.

[0033] In one implementation, the negative voltage control unit 300 includes 2 to 10 liquid crystal negative voltage control circuits 310, that is, the negative voltage control unit 300 may include 2, 3, 4, 5, 6, 7, 8, 9 or 10 liquid crystal negative voltage control circuits 310.

[0034] Specifically, such as Figure 5 As shown, the liquid crystal negative voltage control circuit 310 includes a first field-effect transistor Q1, a second field-effect transistor Q2, a third field-effect transistor Q3, a second resistor R2, a third resistor R3, a first pull-down resistor Rd1, a second pull-down resistor Rd2, and a pull-up resistor Ru.

[0035] The control electrode of the first field-effect transistor Q1 is electrically connected to the microcontroller unit 200. The control electrode of the first field-effect transistor Q1 is used to receive the control level signal V4. The source of the first field-effect transistor Q1 is electrically connected to the working ground terminal GND. The drain of the first field-effect transistor Q1 is electrically connected to the second field-effect transistor Q2. When the control electrode of the first field-effect transistor Q1 is at a high level, the source and drain of the first field-effect transistor Q1 are turned on. When the control electrode of the first field-effect transistor Q1 is at a low level, the source and drain of the first field-effect transistor Q1 are turned off.

[0036] The control electrode of the second field-effect transistor Q2 is electrically connected to the drain of the first field-effect transistor Q1. The source of the second field-effect transistor Q2 receives the second power supply signal V2. The drain of the second field-effect transistor Q2 is electrically connected to the first terminal of the second resistor R2. When the control electrode of the second field-effect transistor Q2 is at a low level, the source and drain of the second field-effect transistor Q2 are turned on. When the control electrode of the second field-effect transistor Q2 is at a high level, the source and drain of the second field-effect transistor Q2 are turned off.

[0037] The control electrode of the third field-effect transistor Q3 is electrically connected to the second terminal of the second resistor R2, the source electrode of the third field-effect transistor Q3 is electrically connected to the third node L3, the drain electrode of the third field-effect transistor Q3 is electrically connected to the first terminal of the third resistor R3, and the second terminal of the third resistor R3 is electrically connected to the second node L2. When the control electrode of the third field-effect transistor Q3 is high, the source and drain of the third field-effect transistor Q3 are conducting; when the control electrode of the third field-effect transistor Q3 is low, the source and drain of the third field-effect transistor Q3 are disconnected.

[0038] The first terminal of the first pull-down resistor Rd1 is electrically connected to the control terminal of the first field-effect transistor Q1, and the second terminal of the first pull-down resistor Rd1 is electrically connected to the source terminal of the first field-effect transistor Q1.

[0039] The first end of the pull-up resistor Ru is electrically connected to the source of the second field-effect transistor Q2, and the second end of the pull-up resistor Ru is electrically connected to the control terminal of the second field-effect transistor Q2.

[0040] The first terminal of the second pull-down resistor Rd2 is electrically connected to the control terminal of the third field-effect transistor Q3, and the second terminal of the second pull-down resistor Rd2 is electrically connected to the source terminal of the third field-effect transistor Q3.

[0041] In the embodiments of this application, combined with Figure 2 and Figure 5The control electrode of the first field-effect transistor Q1 is connected to the control pin of the microcontroller unit 200. The control pin of the microcontroller unit 200 outputs a control level signal V4. The control level signal V4 is low when no control is needed and high when control is required. When the control level signal V4 is high, the first field-effect transistor Q1 is turned on, causing the control electrode of the second field-effect transistor Q2 to change from high to low. Thus, the second field-effect transistor Q2 is turned on. The second power supply signal V2 is transmitted through the source of the second field-effect transistor Q2 and the second resistor R2 to the control electrode of the third field-effect transistor Q3, so the third field-effect transistor Q3 is also turned on. The third resistor R3 is connected in series with the drain of the third field-effect transistor Q3. When the third field-effect transistor Q3 is turned on, the third resistor R3 is connected in parallel with the feedback resistor Rf, thereby reducing the impedance resistance between the second node L2 and the third node L3. Similarly, when the microcontroller unit 200 is controlled by multiple channels, we can obtain multiple variable negative voltages. Depending on the ambient temperature, the multiple voltages are finally superimposed to form a desired ideal liquid crystal driving voltage. When this ideal liquid crystal driving voltage is applied to the liquid crystal film, a better local smearing effect can be obtained.

[0042] Specifically, the negative voltage control unit 300 also includes a fourth resistor R4. The first terminal of the fourth resistor R4 is electrically connected to the second node L2, and the second terminal of the fourth resistor R4 is electrically connected to the working ground terminal GND. The fourth resistor R4 can play a filtering and voltage stabilizing role, which is beneficial to the stable output of the feedback control signal VFB by the second node L2.

[0043] Specifically, the negative voltage control unit 300 also includes a second capacitor C2. The first terminal of the second capacitor C2 is electrically connected to the third node L3, and the second terminal of the second capacitor C2 is electrically connected to the working ground terminal GND. The fourth resistor R4 can play a filtering and voltage stabilizing role, which is conducive to the stable output of the negative voltage signal VOUT by the third node L3.

[0044] Specifically, in combination Figure 2 and Figure 5 The negative voltage driving circuit also includes an infrared sensor circuit 400, a negative voltage generating circuit 500, a liquid crystal bias voltage generating circuit 600, a liquid crystal driving chip circuit 700, and a power conversion circuit 800.

[0045] The infrared sensor circuit 400 is electrically connected to the microcontroller unit 200. The infrared sensor circuit 400 acquires the coordinate position information of the area to be erased and transmits this information to the microcontroller unit 200. The infrared sensor is mounted around the frame of the partial eraser, located on the surface of the liquid crystal film. The infrared sensor has a very high resolution (32767x32767). When a pen or finger touches the surface of the liquid crystal film, it obstructs the infrared sensor, thus obtaining the position coordinate information. Inputting this position information into the control circuitry allows for corresponding erasure control.

[0046] The negative voltage generating circuit 500 is electrically connected to the second node L2. The negative voltage generating circuit 500 receives the feedback control signal VFB and performs voltage regulation on the negative voltage signal VOUT.

[0047] The liquid crystal bias voltage generating circuit 600 is electrically connected to the negative voltage generating circuit 500. The liquid crystal bias voltage generating circuit 600 receives the negative voltage signal VOUT after voltage regulation and converts it into liquid crystal driving voltage.

[0048] The liquid crystal driver chip circuit 700 is electrically connected to the microcontroller unit 200 and the liquid crystal bias voltage generation circuit 600. The microcontroller unit 200 transmits coordinate position information to the liquid crystal driver chip circuit 700. The liquid crystal driver chip circuit 700 receives the liquid crystal driving voltage and drives the liquid crystal at the corresponding coordinate position to deflect.

[0049] The power conversion circuit 800 is electrically connected to the microcontroller unit 200, the negative voltage control unit 300, the negative voltage generating circuit 500, the liquid crystal bias voltage generating circuit 600, and the liquid crystal driver chip circuit 700. The power conversion circuit 800 is used to supply power.

[0050] Combination Figure 2 and Figure 6As shown, the liquid crystal film of the blackboard eraser mainly consists of an upper conductive layer, a middle liquid crystal layer, and a lower conductive layer. For example, the upper conductive layer includes conductive strips X1-X6 arranged horizontally, and the lower conductive layer includes conductive strips Y1-Y6 arranged vertically, with conductive strips X1-X6 and Y1-Y6 interleaved. The liquid crystal driving chip circuit 700 includes a first liquid crystal driving chip circuit and a second liquid crystal driving chip circuit. The first liquid crystal driving chip circuit is used to apply voltage to the conductive strips X1-X6, and the second liquid crystal driving chip circuit 700 is used to apply voltage to the conductive strips Y1-Y6. When we want to erase a certain position, after applying positive and negative AC voltages to the conductive strips of the upper and lower conductive layers at the corresponding positions, the points where the applied voltages on the conductive strips of the upper and lower conductive layers intersect can be erased, and so on. For example, after applying positive and negative AC voltages to conductive strips X3 and Y4, the area where conductive strips X3 and Y4 intersect is erased.

[0051] Please see Figure 7 This application also proposes a local eraser 900, which includes the aforementioned negative voltage drive circuit.

[0052] It should be noted that the technical solutions of the various embodiments of this application 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 in this application.

[0053] The above description is only a part or preferred embodiment of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. A negative voltage driving circuit, applied to a partial eraser blackboard, characterized in that, include: A temperature sensing circuit includes a first resistor, a thermistor, and a first node. The first end of the first resistor is used to connect to a first power signal, and the second end of the first resistor is electrically connected to the first node. The first end of the thermistor is electrically connected to the first node, and the second end of the thermistor is electrically connected to a working ground terminal. The first node is used to output an analog voltage signal. A microcontroller unit is electrically connected to the first node, and the microcontroller unit receives the analog voltage signal to generate a control level signal; as well as A negative voltage control unit is electrically connected to the microcontroller unit. The negative voltage control unit receives the control level signal and outputs a feedback control signal.

2. The negative voltage driving circuit according to claim 1, characterized in that, The temperature sensing circuit includes a filtering unit, the first end of which is electrically connected to the first node, and the second end of which is electrically connected to the working ground terminal.

3. The negative voltage driving circuit according to claim 2, characterized in that, The filtering unit includes a first capacitor, a first terminal of which is electrically connected to the first node, and a second terminal of which is electrically connected to the working ground terminal.

4. The negative voltage driving circuit according to claim 1, characterized in that, The negative voltage control unit includes multiple liquid crystal negative voltage control circuits, a second node, a third node, and a feedback resistor; The liquid crystal negative voltage control circuit is electrically connected to the microcontroller unit, the second node, and the third node; the first end of the feedback resistor is electrically connected to the second node, and the second end of the feedback resistor is electrically connected to the third node. The microcontroller receives the analog voltage signal to generate multiple control level signals, and the liquid crystal negative voltage control circuit corresponds one-to-one with the control level signals. Each of the liquid crystal negative voltage control circuits receives the corresponding control level signal and adjusts the impedance between the second node and the third node; After the multiple liquid crystal negative voltage control circuits superimpose and adjust the impedance between the second node and the third node, the second node outputs the feedback control signal. The third node is used to output a negative voltage signal.

5. The negative voltage driving circuit according to claim 4, characterized in that, The liquid crystal negative voltage control circuit includes a first field-effect transistor, a second field-effect transistor, a third field-effect transistor, a second resistor, a third resistor, a first pull-down resistor, a second pull-down resistor, and a pull-up resistor; The control electrode of the first field-effect transistor is electrically connected to the microcontroller unit. The control electrode of the first field-effect transistor is used to receive the control level signal. The source electrode of the first field-effect transistor is electrically connected to the working ground terminal. The drain electrode of the first field-effect transistor is electrically connected to the second field-effect transistor. When the control electrode of the first field-effect transistor is high, the source and drain of the first field-effect transistor are turned on; when the control electrode of the first field-effect transistor is low, the source and drain of the first field-effect transistor are turned off. The control electrode of the second field-effect transistor is electrically connected to the drain of the first field-effect transistor. The source of the second field-effect transistor receives a second power supply signal, and the drain of the second field-effect transistor is electrically connected to the first terminal of the second resistor. When the control electrode of the second field-effect transistor is at a low level, the source and drain of the second field-effect transistor are connected. When the control electrode of the second field-effect transistor is at a high level, the source and drain of the second field-effect transistor are disconnected. The control terminal of the third field-effect transistor is electrically connected to the second terminal of the second resistor, the source terminal of the third field-effect transistor is electrically connected to the third node, the drain terminal of the third field-effect transistor is electrically connected to the first terminal of the third resistor, and the second terminal of the third resistor is electrically connected to the second node. When the control electrode of the third field-effect transistor is at a high level, the source and drain of the third field-effect transistor are turned on; when the control electrode of the third field-effect transistor is at a low level, the source and drain of the third field-effect transistor are turned off. The first terminal of the first pull-down resistor is electrically connected to the control terminal of the first field-effect transistor, and the second terminal of the first pull-down resistor is electrically connected to the source terminal of the first field-effect transistor. The first end of the pull-up resistor is electrically connected to the source of the second field-effect transistor, and the second end of the pull-up resistor is electrically connected to the control terminal of the second field-effect transistor. The first terminal of the second pull-down resistor is electrically connected to the control terminal of the third field-effect transistor, and the second terminal of the second pull-down resistor is electrically connected to the source terminal of the third field-effect transistor.

6. The negative voltage driving circuit according to claim 5, characterized in that, The negative voltage control unit further includes a fourth resistor, the first end of which is electrically connected to the second node, and the second end of which is electrically connected to the working ground terminal.

7. The negative voltage driving circuit according to claim 5, characterized in that, The negative voltage control unit further includes a second capacitor, the first terminal of which is electrically connected to the third node, and the second terminal of which is electrically connected to the working ground terminal.

8. The negative voltage driving circuit according to claim 4, characterized in that, The negative voltage driving circuit also includes: An infrared sensor circuit is electrically connected to the microcontroller unit. The infrared sensor circuit is used to acquire the coordinate position information of the part to be erased and transmit the coordinate position information to the microcontroller unit. A negative voltage generating circuit is electrically connected to the second node. The negative voltage generating circuit receives the feedback control signal and performs voltage regulation processing on the negative voltage signal. A liquid crystal bias voltage generating circuit is electrically connected to the negative voltage generating circuit. The liquid crystal bias voltage generating circuit receives the negative voltage signal after voltage regulation and converts it into a liquid crystal driving voltage. A liquid crystal driving chip circuit is electrically connected to the microcontroller unit and the liquid crystal bias voltage generating circuit. The microcontroller unit transmits the coordinate position information to the liquid crystal driving chip circuit. The liquid crystal driving chip circuit receives the liquid crystal driving voltage and drives the liquid crystal at the corresponding coordinate position to deflect. The power conversion circuit is electrically connected to the microcontroller unit, the negative voltage control unit, the negative voltage generating circuit, the liquid crystal bias voltage generating circuit, and the liquid crystal driver chip circuit. The power conversion circuit is used to supply power.

9. A partial erasing blackboard, characterized in that, Includes the negative voltage drive circuit as described in any one of claims 1-8.

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