Liquid crystal handwriting tablet driver chip and application circuit thereof, and liquid crystal handwriting tablet

Abstract

The present invention discloses a liquid crystal handwriting board driver chip and its application circuit, and a liquid crystal handwriting board, wherein the liquid crystal handwriting board driver chip comprises: a detection circuit for detecting a key trigger signal and outputting a corresponding working mode signal; an erasing signal generating circuit for generating an erasing signal according to the working mode; a voltage shifter for converting and outputting the erasing signal; a driving circuit for amplifying the current of the signal output by the voltage shifter and outputting a driving signal to the liquid crystal handwriting board; a clock generating circuit for generating a reference clock according to the key trigger signal; a boost switch tube for boosting the input voltage; and a boost control circuit for controlling the boost switch tube. The present invention integrates the driving circuit into the driving chip, directly drives the liquid crystal handwriting board through the chip, reduces the volume of peripheral devices and circuits, and reduces the complexity of processing and assembly.

Description

Technical Field

[0001] The present invention relates to the field of liquid crystal handwriting tablets, and in particular to a liquid crystal handwriting tablet driving chip and an application circuit thereof, and a liquid crystal handwriting tablet. Background Art

[0002] The LCD tablet is a handwriting and drawing device that can retain the handwriting and drawing content for a long time without consuming power. The content of the LCD tablet can be partially or fully erased through a dedicated drive circuit.

[0003] The driving circuit of the LCD handwriting board currently on the market is realized by using a controller plus peripheral devices. This solution has many peripheral devices, large volume, and complex processing and assembly.

[0004] Therefore the prior art still needs to be improved and enhanced. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a liquid crystal handwriting board driver chip and its application circuit, as well as a liquid crystal handwriting board, which integrates the driver circuit into the driver chip and directly drives the liquid crystal handwriting board through the chip, thereby reducing the size of peripheral devices and circuits and reducing the complexity of processing and assembly.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a liquid crystal handwriting board driving chip, which is connected to a liquid crystal handwriting board diaphragm, and includes:

[0008] A detection circuit connected to the key and used to detect the key trigger signal and output a corresponding working mode signal;

[0009] an erasure signal generating circuit connected to the detection circuit and used to generate an erasure signal according to the working mode;

[0010] A voltage shifter connected to the erase signal generating circuit and used for converting and outputting the erase signal;

[0011] A driving circuit connected to the voltage shifter and the boost module outside the liquid crystal handwriting board driving chip, used for current amplifying the signal output by the voltage shifter and outputting a driving signal to the liquid crystal handwriting board;

[0012] A clock generating circuit connected to the detection circuit and used for generating a reference clock according to the key trigger signal;

[0013] A boost switch tube for boosting the input voltage;

[0014] A boost control circuit connected to the clock generation circuit and the boost switch tube and used to control the boost switch tube.

[0015] The liquid crystal handwriting board driver chip also includes:

[0016] An overcurrent protection circuit is used to detect the current of a boost switch tube and shut down the switch tube when the current exceeds a preset current value; the overcurrent protection circuit is connected to a boost control circuit and a boost module outside the chip.

[0017] The liquid crystal handwriting board driver chip also includes: an overvoltage protection circuit for detecting the voltage of the boost switch tube and turning off the switch tube when the voltage exceeds a first voltage preset value; the overvoltage protection circuit is connected to the boost control circuit and the boost module outside the chip.

[0018] The liquid crystal handwriting board driver chip also includes: a voltage detection circuit for detecting the voltage boosted by the boost module and shutting down the boost control circuit when the voltage is higher than a second voltage preset value; the voltage detection circuit is connected to the boost control circuit, the detection circuit and the boost module outside the chip.

[0019] The liquid crystal handwriting board driver chip also includes:

[0020] A voltage reference circuit connected to the voltage detection circuit and used to provide a reference voltage;

[0021] A reset circuit for providing a reset signal; the reset circuit is respectively connected to each circuit in the liquid crystal handwriting board driver chip.

[0022] An application circuit of a liquid crystal handwriting tablet driver chip, comprising the liquid crystal handwriting tablet driver chip as described above;

[0023] A voltage boost module connected to the LCD handwriting board driver chip and used for boosting voltage in combination with the LCD handwriting board driver chip;

[0024] A key module connected to the LCD handwriting board driver chip and used to send key pulses;

[0025] A filtering unit connected to the LCD handwriting board driver chip and used for filtering;

[0026] An output control unit connected to the LCD handwriting board driver chip and the boost module and used to determine the output voltage of the boost circuit composed of the boost module and the LCD handwriting board driver chip;

[0027] The liquid crystal handwriting board driving chip is also connected to the liquid crystal handwriting board.

[0028] In a possible implementation, the boost module includes a first capacitor, a first inductor, and a first diode; one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor, and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded;

[0029] The filtering unit includes a second capacitor, one end of the second capacitor is connected to the other end of the first inductor and the VDD pin of the liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to the GND pin of the liquid crystal handwriting board driver chip and grounded;

[0030] The output control unit includes a first resistor, one end of the first resistor is connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the FB pin of the liquid crystal handwriting board driver chip;

[0031] The key module includes a first key, one end of which is connected to a KEY pin of a liquid crystal handwriting board driving chip, and the other end of which is grounded.

[0032] In a possible implementation, the boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded;

[0033] The filtering unit includes a second capacitor, one end of the second capacitor is connected to the other end of the first inductor and the VDD pin of the liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to the GND pin of the liquid crystal handwriting board driver chip and grounded;

[0034] The output control unit includes a first resistor, one end of the first resistor is connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the FB pin of the liquid crystal handwriting board driver chip;

[0035] The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

[0036] In a possible implementation, the application circuit further includes a first indicator light, and the first indicator light is connected to an LED pin of the liquid crystal handwriting board;

[0037] The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded;

[0038] The filtering unit includes a second capacitor, one end of the second capacitor is connected to the other end of the first inductor and the VDD pin of the liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to the GND pin of the liquid crystal handwriting board driver chip and grounded;

[0039] The output control unit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to the FB1 pin of the liquid crystal handwriting board driver chip, one end of the second resistor is connected to the FB2 pin of the liquid crystal handwriting board driver chip, the other end of the first resistor and the other end of the second resistor are both connected to one end of the third resistor and the MFB pin of the liquid crystal handwriting board driver chip, and the other end of the third resistor is connected to the VOUT pin of the liquid crystal handwriting board driver chip;

[0040] The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

[0041] In a possible implementation, the boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded;

[0042] The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded;

[0043] The key module includes a first key, a second key, and a first resistor, one end of the first key is connected to a KEY1 pin of a liquid crystal handwriting board driver chip, the other end of the first key is grounded, one end of the second key is connected to one end of a first resistor, the other end of the first resistor is connected to a KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded;

[0044] The application circuit also includes a first indicator light and a second resistor, the input end of the first indicator light is connected to a power supply, the output end of the first indicator light is connected to one end of the second resistor, and the second resistor is connected to a KEY2 pin of the liquid crystal handwriting board.

[0045] In a possible implementation, the boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded;

[0046] The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded;

[0047] The output control unit includes a first resistor and a second resistor, one end of the first resistor and one end of the second resistor are both connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, the other end of the first resistor is connected to the FB pin of the liquid crystal handwriting board driver chip, and the other end of the second resistor is connected to the LFB pin of the liquid crystal handwriting board driver chip;

[0048] The key module includes a first key, a second key, and a third resistor, one end of the first key is connected to a KEY1 pin of a liquid crystal handwriting board driver chip, the other end of the first key is grounded, one end of the second key is connected to one end of a third resistor, the other end of the third resistor is connected to a KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded;

[0049] The application circuit also includes a first indicator light and a fourth resistor, the input end of the first indicator light is connected to a power supply, the output end of the first indicator light is connected to one end of a fourth resistor, and the fourth resistor is connected to a KEY2 pin of the liquid crystal handwriting board.

[0050] A liquid crystal handwriting tablet comprises the liquid crystal handwriting tablet driver chip as described above.

[0051] Compared with the prior art, the present invention provides a liquid crystal handwriting board driver chip and its application circuit, as well as a liquid crystal handwriting board, wherein the liquid crystal handwriting board driver chip includes: a detection circuit connected to a key for detecting a key trigger signal and outputting a corresponding working mode signal; an erasing signal generating circuit connected to the detection circuit for generating an erasing signal according to the working mode; a voltage shifter connected to the erasing signal generating circuit for converting and outputting the erasing signal; a driving circuit connected to the voltage shifter and a boost module outside the liquid crystal handwriting board driver chip for current amplification of the signal output by the voltage shifter and outputting a driving signal to the liquid crystal handwriting board; a clock generating circuit connected to the detection circuit for generating a reference clock according to the key trigger signal; a boost switch tube for boosting the input voltage; and a boost control circuit connected to the clock generating circuit and the boost switch tube for controlling the boost switch tube. The present invention integrates the driving circuit into the driving chip, directly drives the liquid crystal handwriting board through the chip, reduces the volume of peripheral devices and circuits, and reduces the complexity of processing and assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a structural block diagram of the liquid crystal handwriting tablet driver chip provided by the present invention;

[0053] Figure 2 A circuit diagram of the first embodiment of the application circuit of the liquid crystal handwriting board driver chip provided by the present invention;

[0054] Figure 3 A circuit diagram of a second application circuit embodiment of a liquid crystal handwriting board driver chip provided by the present invention;

[0055] Figure 4 A circuit diagram of a third embodiment of a liquid crystal handwriting tablet driver chip provided by the present invention;

[0056] Figure 5 A circuit diagram of a fourth embodiment of a liquid crystal handwriting board driver chip provided by the present invention;

[0057] Figure 6 This is a circuit diagram of Embodiment 5 of the liquid crystal handwriting board driver chip provided by the present invention. DETAILED DESCRIPTION

[0058] The present invention provides a liquid crystal handwriting board driving chip and its application circuit, and a liquid crystal handwriting board, which integrates the driving circuit into the driving chip, directly drives the liquid crystal handwriting board through the chip, reduces the volume of peripheral devices and circuits, and reduces the complexity of processing and assembly.

[0059] The specific embodiments of the present invention are intended to facilitate a more detailed description of the technical concept of the present invention, the technical problems solved, the technical features constituting the technical solution, and the technical effects brought about. It should be noted that the explanation of these embodiments does not constitute a limitation on the protection scope of the present invention. In addition, the technical features involved in the embodiments described below can be combined with each other as long as they do not conflict with each other.

[0060] See also Figure 1 The present invention provides a liquid crystal handwriting board driver chip, including: a detection circuit 10 connected to a key, used to detect a key trigger signal and output a corresponding working mode signal; an erasing signal generating circuit 30 connected to the detection circuit 10, used to generate an erasing signal according to the working mode; a voltage shifter 40 connected to the erasing signal generating circuit 30, used to convert and output the erasing signal; a driving circuit 50 connected to the voltage shifter 40 and a boost module on the periphery of the liquid crystal handwriting board driver chip, used to amplify the current of the signal output by the voltage shifter 40 and output a driving signal to the liquid crystal handwriting board; a clock generating circuit 60 connected to the detection circuit 10, used to generate a reference clock according to the key trigger signal; a boost switch tube 70 used to boost the input voltage; a boost control circuit 80 connected to the clock generating circuit 60 and the boost switch tube 70, used to control the boost switch tube 70.

[0061] In the specific implementation, in this embodiment, the present invention adopts high-voltage integrated circuit technology for design, and the detection circuit 10, the erase signal generating circuit 30, the voltage shifter 40, the driving circuit 50, the clock generating circuit 60, the boost switch tube 70 and the boost control circuit 80 are integrated and packaged into a driving chip. As is known to all, the volume of the chip is basically very small, which is greatly reduced compared with the volume of the discrete circuit. Moreover, since each discrete circuit is integrated into the chip, the peripheral components are also greatly reduced. Due to the reduction of peripheral components, the complexity of circuit board processing, component mounting, etc. is also greatly reduced.

[0062] Specifically, in this embodiment, the detection circuit 10 is connected to an external button; after power-on, the liquid crystal handwriting board driver chip (hereinafter referred to as the driver chip) is in a dormant state with no current input; when a button is pressed, a pulse signal is triggered, and the detection circuit 10 receives the pulse signal and transmits it to the clock generation circuit 60, and the clock generation circuit 60 starts to work and generate a clock signal. The detection circuit 10 continuously detects the pulse signal. If the duration of the pulse signal does not reach the effective key press time, the pulse signal is judged to be an invalid signal, the clock generation circuit 60 is turned off, and the chip enters the dormant state again, realizing the anti-jitter function to avoid false triggering. If the duration of the pulse signal reaches the effective key press time, the pulse signal is judged to be a valid signal, and the chip enters the working state. It can be understood that the button needs to be pressed for a certain period of time to trigger the chip to start, and the effective key press time can be set as needed.

[0063] Specifically, when the chip is in working state, the clock generation circuit 60 generates a clock signal to the detection circuit 10, the erase signal generation circuit 30 and the boost control circuit 80. The number of external buttons connected to the detection circuit 10 can be one or two.

[0064] When only one button is connected to the detection circuit 10, that is, the first button S1, there are two button trigger modes, one is single-click button trigger, and the other is double-click button trigger; pressing the first button S1 once is single-click button trigger, and pressing the first button S2 twice is double-click button trigger. Press the first button S1 according to the corresponding operations of the two trigger modes, and the first button S1 sends a corresponding pulse signal. The detection circuit 10 selects an erase cycle according to the detected pulse signal; specifically, single-click button trigger is defined as a partial erase mode, and the erase cycle is 10 to 60 seconds; double-click button trigger is defined as a full-screen erase mode, and the erase cycle is 0.5 to 2 seconds.

[0065] The detection circuit 10 selects the working mode (partial erasing mode or full-screen erasing mode) according to the erasing cycle, and transmits the working mode signal to the erasing signal generating circuit 30; the erasing signal generating circuit 30 generates a low-voltage erasing signal to the voltage shifter 40, and the voltage shifter 40 converts the low-voltage signal into a high-voltage signal, and transmits it to the driving circuit 50, which outputs the driving signal to the liquid crystal writing board for driving; after the circuit works for an erasing cycle, the clock generating circuit 60 is turned off, the chip enters a dormant state, no current passes, and the detection circuit 10 continues to monitor the keys. Specifically, by connecting the driving signal between the two electrodes of the liquid crystal writing board membrane, the contents of the liquid crystal writing board membrane can be erased. According to the needs, different electrical signals are added to the two poles of the liquid crystal writing board membrane (that is, different working modes have different electrical signals), which can realize full-screen erasing or partial erasing.

[0066] Furthermore, when the interval between pressing the first button twice is within a preset time, it is identified as a double-click button trigger, and the detection circuit 10 identifies it as a full-screen erase mode; otherwise, it is a single-click button trigger, and the detection circuit 10 identifies it as a partial erase mode. The preset time may be 600ms.

[0067] It should be noted that the working mode in the driver chip may also be only the full-screen erasing mode, and correspondingly there is only one key triggering situation.

[0068] When there are two buttons connected to the detection circuit 10, namely the first button S1 and the second button S2, when the first button S1 is pressed, it is in full-screen erasing mode, and when the second button S2 is pressed, it is in partial erasing mode; the erasing period of full-screen erasing is 0.5 to 2 seconds, and the erasing period of partial erasing is 10 to 60 seconds.

[0069] When the detection circuit 10 detects the pulse signal of the first key S1 or the second key S2, the clock generation circuit 60 works, and the detection circuit 10 continuously detects the pulse signal of the first key S1 or the second key S2. If the duration of the pulse signal of the first key S1 or the second key S2 does not reach the effective key time, it is judged as an invalid signal, the clock generation circuit 60 is turned off, the chip enters a dormant state, no current passes, and the detection circuit 10 continues to monitor the key; if the duration of the pulse signal of the first key S1 or the second key S2 reaches the effective key time, it is judged as a valid signal, and the chip enters a working state, the detection circuit 10 selects a mode according to the key signal, and then the erase signal generation circuit 30 generates an erase signal, which is output to the membrane of the liquid crystal handwriting board through the voltage shifter 40 and the drive circuit 50 for an erase operation; after the circuit works for an erase cycle, the clock generation circuit 60 is turned off, the chip enters a dormant state, no current passes, and the detection circuit 10 continues to monitor the key. Specifically, by connecting a drive signal between the two electrodes of the liquid crystal handwriting board membrane, the content of the liquid crystal handwriting board membrane can be erased. According to the needs, different electrical signals are added to the two poles of the liquid crystal handwriting board membrane (that is, different working modes have different electrical signals), so that full screen erasing or partial erasing can be achieved.

[0070] In this embodiment, a voltage shifter 40 is used to isolate high and low voltage circuits, and a reset circuit 94 is integrated to perform anti-interference optimization processing on the clock circuit, thereby improving the anti-interference performance of the driver chip.

[0071] Optionally, the driver chip further includes: an overcurrent protection circuit 91 for detecting the current of the boost switch tube 70 and shutting down the switch tube when the current exceeds a preset current value; the overcurrent protection circuit is connected to the boost control circuit 80 and the peripheral boost module.

[0072] Specifically, the boost control circuit 80 receives the clock signal sent by the clock generation circuit 60, and transmits it to the boost switch tube 70. The boost switch tube 70 cooperates with the peripheral boost module to boost the VCC voltage to the required diaphragm erase voltage, and then transmits it back to the voltage shifter 40 and the drive circuit 50 to provide voltage for the voltage shifter 40 and the drive circuit 50.

[0073] The overcurrent protection circuit 91 detects the current of the boost switch tube 70. When the switch tube current exceeds the preset current value, the overcurrent protection circuit 91 sends a first shutdown signal to the boost control circuit 80. The boost control circuit 80 stops transmitting the clock signal to the boost switch tube 70 according to the first shutdown signal. The boost control circuit 80 is turned off to prevent the switch tube from being damaged by overcurrent, thereby playing a role of overcurrent protection. The boost control circuit 80 is started again until the next erase cycle to continue the boost work.

[0074] Particularly, the preset current value is the current value of the rated current of the boost switch tube 70 .

[0075] Optionally, the driver chip also includes: an overvoltage protection circuit 90 for detecting the voltage boosted by the boost module (i.e., the boost value) and shutting down the switch tube when the voltage exceeds a first voltage preset value; the overvoltage protection circuit is connected to the boost control circuit and the boost module outside the chip.

[0076] Specifically, the overvoltage protection circuit 90 detects the voltage boosted by the boost module (i.e., the boost value). When the boost value exceeds the first voltage preset value, the overvoltage protection circuit 90 sends a second shutdown signal to shut down the boost control circuit 80 to prevent damage to the switch tube and play a role in overvoltage protection; until the next erase cycle, the boost control circuit 80 is turned on again to continue the boost work.

[0077] Particularly, the first preset voltage value is a voltage value of a rated voltage of the switching tube.

[0078] Optionally, the driver chip also includes: a voltage detection circuit 92 for detecting the voltage boosted by the boost module and shutting down the boost control circuit 80 when the output voltage is higher than a second voltage preset value; the voltage detection circuit is connected to the boost control circuit, the detection circuit and the boost module outside the chip.

[0079] Specifically, the voltage detection circuit 92 detects the boost voltage value fed back after the boost module outside the driving chip boosts the voltage. When the boost voltage value is lower than the second voltage preset value, the boost control circuit 80 is controlled to increase the output voltage so that the boost voltage value is equal to the second voltage preset value; when the boost voltage value is higher than the second voltage preset value, the boost control circuit 80 is controlled to be turned off so that the boost voltage value is stable.

[0080] Particularly, the second preset voltage value is a voltage value of a local erasing voltage or a full-screen erasing voltage.

[0081] Specifically, the driving chip further includes: a voltage reference circuit 93 connected to the voltage detection circuit 92 for providing a reference voltage; a reset circuit 94 for providing a reset signal; and the reset circuit is respectively connected to each circuit in the liquid crystal handwriting board driving chip.

[0082] The voltage reference circuit 93 provides a reference voltage for the voltage detection circuit 92. The voltage reference circuit 93 can work in a low voltage environment. The logic processing circuit in the reference voltage uses low threshold and high withstand voltage devices, which broadens the voltage working range. The reset circuit 94 provides a reset signal for each circuit in the driver chip.

[0083] Furthermore, the embodiment of the present invention adopts a full sleep mode, wakes up when working, and has zero power consumption in sleep mode; the boost switch tube 70 and the external boost module form a boost circuit, and through structural optimization and process optimization, the internal resistance of the switch tube is greatly reduced, which greatly improves the working efficiency; all current paths have control switches and are all closed in sleep mode, further reducing power consumption.

[0084] The present invention also adopts a closed-loop control boost circuit structure, which integrates a high-precision voltage reference internally and is less affected by voltage and temperature changes, thereby achieving precise voltage control.

[0085] See also Figures 2 to 4 Based on the above-mentioned liquid crystal handwriting board driver chip, the present invention also provides an application circuit of a liquid crystal handwriting board driver chip, including the liquid crystal handwriting board driver chip as described above; a boost module connected to the liquid crystal handwriting board driver chip and used to achieve boost in combination with the liquid crystal handwriting board driver chip; a key module connected to the liquid crystal handwriting board driver chip and used to send key pulses; a filtering unit connected to the liquid crystal handwriting board driver chip and used for filtering; an output control unit connected to the liquid crystal handwriting board driver chip and the boost module and used to determine the output voltage of the boost circuit; the liquid crystal handwriting board driver chip is also connected to the liquid crystal handwriting board.

[0086] In specific implementation, in this embodiment, the driver chip can freely set the number of pins according to the number of connected buttons (for example, if only one button needs to be connected, eight pins are set; if two buttons need to be set, ten pins or twelve pins can be set).

[0087] Embodiment 1

[0088] See also Figure 2 The key module includes a first key, one end of which is connected to the KEY pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded.

[0089] When only the first key S1 is connected, the fourth pin (KEY pin) of the driver chip is connected to the key detection module, and the first key S1 is connected to the fourth pin of the driver chip for key detection. The first pin of the driver chip is connected to VCC to provide power for the entire chip. The second pin of the driver chip is connected to the boost switch tube 70, and the boost module is connected to the second pin (Lx pin) of the driver chip to achieve the boost of VCC. The third pin of the driver chip is the boost feedback pin (FB pin), which provides input voltage for the voltage detection circuit 92 and provides an erase voltage for the driver circuit. The fifth pin of the driver chip is the boost voltage input port (VOUT pin), and the boost switch tube 70 and the boost module are connected from the fifth pin of the driver chip through the boosted voltage to provide the corresponding erase voltage for the driver circuit 50. The sixth pin (VB pin) and the seventh pin (VA pin) of the driver chip are both output ports of the driver circuit 50, which are connected to the two poles of the liquid crystal handwriting board membrane to drive the liquid crystal handwriting board membrane to perform the corresponding erase operation. The eighth pin (GND pin) of the driver chip is the ground terminal of the chip. The first pin (VDD pin) of the driver chip is used to access the chip driving voltage to enable the chip to work normally.

[0090] Specifically, the specific connection relationship of the application circuit connected to only one button is:

[0091] The boost module includes a first capacitor, a first inductor and a first diode; one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded.

[0092] The filtering unit includes a second capacitor, one end of which is connected to the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded.

[0093] The output control unit includes a first resistor, one end of the first resistor is connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the FB pin of the liquid crystal handwriting board driver chip.

[0094] Embodiment 2

[0095] Please continue reading Figure 3In this embodiment, the driver chip U1 is provided with ten pins, and the first pin ( Figure 3 The VDD pin in the chip is used to connect the chip drive voltage to enable the chip to work normally. The second pin of the driver chip U1 is connected to the boost switch tube 70, and the boost module is connected to the second pin of the driver chip U1 ( Figure 3 The third pin of the driver chip U1 is the boost feedback pin ( Figure 3 The FB pin in the drive chip U1 provides an input voltage for the voltage detection circuit 92 and an erase voltage for the drive circuit. Figure 3 KEY1 pin) and the fifth pin ( Figure 3 The KEY2 pin of the driver chip U1 is connected to the key detection module, which is connected to the fourth and fifth pins of the driver chip U1 for key detection. The seventh pin of the driver chip U1 is the boost voltage input port ( Figure 3 The boost switch tube 70 and the boost module receive the boosted voltage from the seventh pin of the driver chip U1 to provide the corresponding erase voltage for the driver circuit 50. Figure 3 VB pin) and the ninth pin ( Figure 3 The VA pins of the driver chip U1 are all output ports of the driver circuit 50, which are connected to the two electrodes of the liquid crystal handwriting board membrane to drive the liquid crystal handwriting board membrane to perform the corresponding erasing operation. Figure 3 The GND pin of the driver chip U1 is the ground terminal of the chip. The sixth pin of the driver chip U1 is a reserved pin.

[0096] The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

[0097] When the first button S1 and the second button S2 are connected, the driving chip has ten pins, and two pins are used to connect the first button S1 and the second button S2. The first button S1 and the second button S2 are both connected to the detection circuit 10, and other connection methods are the same as the case where only the first button S1 is connected.

[0098] The boost module includes a first capacitor C1, a first inductor L1 and a first diode D1; one end of the first inductor L1 is connected to the input end of the first diode D1 and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor L1 is connected to the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode D1 is connected to the output control unit, one end of the first capacitor C1 and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor C1 is grounded.

[0099] In specific implementation, the first inductor L1, diode D1, capacitor C1, boost control circuit 80, and boost switch tube 70 jointly complete the boost function, increase the voltage of VCC to be equal to the erase voltage, and provide input voltage for the driver chip to realize the erase operation.

[0100] The filtering unit includes a second capacitor C2, one end of the second capacitor C2 is connected to the other end of the first inductor L1 and the VDD pin of the liquid crystal handwriting board driver chip, and the other end of the second capacitor C2 is connected to the GND pin of the liquid crystal handwriting board driver chip and grounded. Specifically, the second capacitor C2 is used for capacitor filtering to provide a stable voltage for the operation of the internal circuit of the driver chip.

[0101] The output control unit includes a first resistor R1, one end of the first resistor R1 is connected to one end of the first capacitor C1, the output end of the first diode D1 and the VOUT of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the FB pin of the liquid crystal handwriting board driver chip.

[0102] The first resistor R1 is used to set the output voltage of the boost circuit. Adjusting the resistance value of the first resistor R1 can change the output voltage of the boost circuit accordingly. Specifically, adjusting the external R1 resistance value can change the set voltage value to achieve erasing of liquid crystal handwriting boards with different erasing voltages. The voltage detection circuit 92 sets the output voltage of the boost circuit to a local erasing voltage or a full-screen erasing voltage according to the working mode signal transmitted by the detection circuit 10. The full-screen erasing voltage is 3 to 50V, and the local erasing voltage is 3 to 50V. The erasing voltage is selected according to the product characteristics and can be set by the resistance value of R1.

[0103] Embodiment 3

[0104] See also Figure 4 In this embodiment, the driver chip U1 is provided with 12 pins, and the first pin ( Figure 4 The VDD pin in the chip is used to connect the chip drive voltage to enable the chip to work normally. The second pin of the driver chip U1 is connected to the boost switch tube 70, and the boost module is connected to the second pin of the driver chip U1 ( Figure 4 The third pin of the driver chip U1 ( Figure 4 KEY1 pin) and the fourth pin ( Figure 4 The KEY2 pin of the driver chip U1 is connected to the key detection module, which is connected to the third and fourth pins of the driver chip U1 for key detection. Figure 4 FB1 pin), the sixth pin ( Figure 4 FB2 pin) and pin 7 ( Figure 4 The MFB pin of the drive chip U1 is the boost feedback pin, and the total feedback voltage is connected from the seventh pin to provide input voltage for the voltage detection circuit 92, and the full-screen erase feedback voltage and the local erase feedback voltage are connected from the fifth and sixth pins of the drive chip U1 to provide erase voltage for the drive circuit. Figure 4 The ninth pin of the driver chip U1 is the boost voltage input port ( Figure 4 The boost switch tube 70 and the boost module receive the boosted voltage from the ninth pin of the driver chip U1 to provide the corresponding erase voltage for the driver circuit 50. The tenth pin of the driver chip U1 ( Figure 4 VB pin) and pin 11 ( Figure 4 The VA pin of the driver chip U1 is the output port of the driver circuit 50, which is connected to the two electrodes of the liquid crystal handwriting board film to drive the liquid crystal handwriting board film to perform the corresponding erasing operation. Figure 4 The GND pin of the chip is the ground terminal.

[0105] The application circuit also includes a first indicator light, which is connected to an LED pin of the liquid crystal handwriting board.

[0106] The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the Lx pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the VDD pin of the liquid crystal handwriting board driver chip and a filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded.

[0107] The filtering unit includes a second capacitor, one end of which is connected to the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded.

[0108] The output control unit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to the FB1 pin of the liquid crystal handwriting board driver chip, one end of the second resistor is connected to the FB2 pin of the liquid crystal handwriting board driver chip, the other end of the first resistor and the other end of the second resistor are both connected to one end of the third resistor and the MFB pin of the liquid crystal handwriting board driver chip, and the other end of the third resistor is connected to the VOUT pin of the liquid crystal handwriting board driver chip.

[0109] The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

[0110] In the specific implementation, in this embodiment, the first resistor is used to set the voltage value for full-screen erasing, and the second resistor is used to set the voltage value for partial erasing. Specifically, after the boost circuit performs the boost, a total boost voltage value is obtained through the third resistor, which is transmitted to the voltage detection circuit and the first resistor and the second resistor respectively. After receiving the boost voltage value, the voltage detection circuit performs voltage detection, and when the boost voltage value is lower than the second voltage preset value, the output voltage of the boost control circuit is increased, and when the boost voltage value is higher than the second voltage preset value, the boost circuit is turned off to avoid insufficient erasing voltage or burning of the driver chip; after receiving the boost voltage value, the first resistor and the second resistor are adjusted to the corresponding erasing voltage according to the ratio, and the first resistor adjusts the boost voltage value to the voltage value for full-screen erasing and provides it to the drive circuit to drive the liquid crystal handwriting board to perform full-screen erasing, and the second resistor adjusts the boost voltage value to the voltage value for partial erasing and provides it to the drive circuit to drive the liquid crystal handwriting board to perform partial erasing.

[0111] It should be noted that, in this embodiment, the first indicator light can be used to indicate the working states such as low voltage warning, local erase, and global erase, and the specific setting method can be selected according to the needs. Specifically, the boost switch tube 70 can also be set outside the driver chip, which can also realize the scheme of the invention and expand the power output at the same time; or the external switch tube and the driver chip can be sealed together to expand the power output and simplify the application circuit.

[0112] Embodiment 4

[0113] See also Figure 5 In this embodiment, the driver chip U1 is provided with 8 pins, and the first pin ( Figure 5The VDD pin in the chip is used to connect the chip drive voltage to enable the chip to work normally. The second pin of the driver chip U1 is connected to the boost switch tube 70, and the boost module is connected to the second pin of the driver chip U1 ( Figure 5 The third pin of the driver chip U1 ( Figure 5 KEY1 pin) and the fourth pin ( Figure 5 The key detection module is connected to the KEY2 pin of the driver chip U1, and the key module is connected to the third and fourth pins of the driver chip U1 for key detection. The fifth pin of the driver chip U1 is the boost voltage input port (VOUT pin), and the boost switch tube 70 and the boost module are connected from the fifth pin of the driver chip U1 after the boost voltage is boosted to provide the corresponding erase voltage for the drive circuit 50. The sixth pin (VB pin) and the seventh pin (VA pin) of the driver chip U1 are both output ports of the drive circuit 50, which are connected to the two poles of the liquid crystal handwriting board membrane to drive the liquid crystal handwriting board membrane to perform the corresponding erase operation. The eighth pin (GND pin) of the driver chip U1 is the chip grounding terminal.

[0114] The boost module includes a first capacitor C1, a first inductor L1 and a first diode D1. One end of the first inductor L1 is connected to the input end of the first diode D1 and the Lx pin of the liquid crystal handwriting board driver chip U1. The other end of the first inductor L1 is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip U1 and the filtering unit. The output end of the first diode D1 is connected to the output control unit, one end of the first capacitor C1 and the VOUT pin of the liquid crystal handwriting board driver chip U1. The other end of the first capacitor C1 is grounded.

[0115] The filtering unit includes a second capacitor C2, one end of the second capacitor C2 is connected to the power supply, the other end of the first inductor L1 and the VDD pin of the liquid crystal handwriting board driver chip U1, and the other end of the second capacitor C2 is connected to the GND pin of the liquid crystal handwriting board driver chip U1 and grounded.

[0116] The key module includes a first key S1, a second key S2, and a first resistor R1. One end of the first key S1 is connected to the KEY1 pin of the liquid crystal handwriting board driver chip U1, and the other end of the first key S1 is grounded. One end of the second key S2 is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the KEY2 pin of the liquid crystal handwriting board driver chip U1. The other end of the second key S2 is grounded.

[0117] The application circuit also includes a first indicator light LED and a second resistor R2, wherein the input end of the first indicator light LED is connected to a power supply, the output end of the first indicator light LED is connected to one end of the second resistor R2, and the second resistor R2 is connected to a KEY2 pin of the liquid crystal handwriting board.

[0118] In specific implementation, compared with other embodiments, in this embodiment, the first button S1 is configured as a global erase button, and the second button S2 is configured as a local erase button. The second button S2 is connected to the fourth pin of the driver chip U1 through the first resistor R1 to access the detection module for button detection. Since the first button S1 does not have a resistor voltage divider, the voltage generated by pressing the first button S1 is different from the voltage generated by pressing the second button S2, thereby achieving different button recognition. When the second button S2 is pressed to start local erase, the first indicator LED lights up to indicate the local erase mode.

[0119] Embodiment 5

[0120] See also Figure 6 In this embodiment, the driver chip U1 is provided with ten pins, and the first pin ( Figure 6 The VDD pin in the chip is used to connect the chip drive voltage to enable the chip to work normally. The second pin of the driver chip U1 is connected to the boost switch tube 70, and the boost module is connected to the second pin of the driver chip U1 ( Figure 6 The third pin of the driver chip U1 is the boost feedback pin ( Figure 6 The FB pin in the drive chip U1 provides an input voltage for the voltage detection circuit 92 and an erase voltage for the drive circuit. Figure 6 KEY1 pin) and the fifth pin ( Figure 6 The KEY2 pin of the driver chip U1 is connected to the key detection module, and the key module is connected to the fourth and fifth pins of the driver chip U1 for key detection. The sixth pin of the driver chip U1 is the boost feedback pin, and the full-screen erase feedback voltage and the local erase feedback voltage are connected from the sixth pin of the driver chip U1 to provide the erase voltage for the drive circuit. The seventh pin of the driver chip U1 is the boost voltage input port ( Figure 6 The boost switch tube 70 and the boost module receive the boosted voltage from the seventh pin of the driver chip U1 to provide the corresponding erase voltage for the driver circuit 50. Figure 6 VB pin) and the ninth pin ( Figure 6 The VA pins of the driver chip U1 are all output ports of the driver circuit 50, which are connected to the two electrodes of the liquid crystal handwriting board membrane to drive the liquid crystal handwriting board membrane to perform the corresponding erasing operation. Figure 6 The GND pin of the chip is the ground terminal.

[0121] The boost module includes a first capacitor C1, a first inductor L1 and a first diode D1. One end of the first inductor L1 is connected to the input end of the first diode D1 and the Lx pin of the liquid crystal handwriting board driver chip U1. The other end of the first inductor L1 is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip U1 and the filtering unit. The output end of the first diode D1 is connected to the output control unit, one end of the first capacitor C1 and the VOUT pin of the liquid crystal handwriting board driver chip U1. The other end of the first capacitor C1 is grounded.

[0122] The filtering unit includes a second capacitor C2, one end of the second capacitor C2 is connected to the power supply, the other end of the first inductor L1 and the VDD pin of the liquid crystal handwriting board driver chip U1, and the other end of the second capacitor C2 is connected to the GND pin of the liquid crystal handwriting board driver chip U1 and grounded.

[0123] The output control unit includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 and one end of the second resistor R2 are both connected to one end of the first capacitor C1, the output end of the first diode D1 and the VOUT pin of the liquid crystal handwriting board driver chip U1, the other end of the first resistor R1 is connected to the FB pin of the liquid crystal handwriting board driver chip U1, and the other end of the second resistor R2 is connected to the LFB pin of the liquid crystal handwriting board driver chip U1.

[0124] The key module includes a first key S1, a second key S2, and a third resistor R3. One end of the first key S1 is connected to the KEY1 pin of the liquid crystal handwriting board driver chip U1, and the other end of the first key S1 is grounded. One end of the second key S2 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the KEY2 pin of the liquid crystal handwriting board driver chip U1. The other end of the second key S2 is grounded.

[0125] The application circuit also includes a first indicator light LED and a fourth resistor R4, wherein the input end of the first indicator light LED is connected to a power supply, the output end of the first indicator light LED is connected to one end of the fourth resistor R4, and the fourth resistor R4 is connected to the KEY2 pin of the liquid crystal handwriting board.

[0126] In the specific implementation, compared with other embodiments, in this embodiment, different key recognitions in embodiment four and indication of local erasing mode by indicator lights are realized at the same time; the first resistor R1 and the second resistor R2 are respectively connected to the third and sixth pins of the driver chip U1 to realize boost feedback, and the full-screen erasing feedback voltage and the local erasing feedback voltage are respectively connected from the third and sixth pins of the driver chip U1 to provide an erasing voltage for the drive circuit.

[0127] Based on the above-mentioned liquid crystal handwriting board driver chip and the application circuit of the liquid crystal handwriting board driver chip, the present invention also provides a liquid crystal handwriting board, including the liquid crystal handwriting board driver chip as described above. Since the liquid crystal handwriting board driver chip and the application circuit of the liquid crystal handwriting board driver chip have been described in detail above, they will not be repeated here.

[0128] In summary, the present invention provides a liquid crystal handwriting board driver chip and its application circuit, as well as a liquid crystal handwriting board, wherein the liquid crystal handwriting board driver chip includes: a detection circuit connected to a key for detecting a key trigger signal and outputting a corresponding working mode signal; an erasing signal generating circuit connected to the detection circuit for generating an erasing signal according to the working mode; a voltage shifter connected to the erasing signal generating circuit for converting and outputting the erasing signal; a driving circuit connected to the voltage shifter and a boost module outside the liquid crystal handwriting board driver chip for current amplifying the signal output by the voltage shifter and outputting a driving signal to the liquid crystal handwriting board; a clock generating circuit connected to the detection circuit for generating a reference clock according to the key trigger signal; a boost switch tube for boosting the input voltage; and a boost control circuit connected to the clock generating circuit and the boost switch tube for controlling the boost switch tube. The present invention integrates the driving circuit into the driving chip, directly drives the liquid crystal handwriting board through the chip, reduces the volume of peripheral devices and circuits, and reduces the complexity of processing and assembly.

[0129] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A liquid crystal handwriting tablet driver chip connected to a liquid crystal handwriting tablet diaphragm, characterized in that: include: A detection circuit connected to the key and used to detect the key trigger signal and output a corresponding working mode signal; an erasure signal generating circuit connected to the detection circuit and used to generate an erasure signal according to the working mode; A voltage shifter connected to the erase signal generating circuit and used for converting and outputting the erase signal; A driving circuit connected to the voltage shifter and the boost module outside the liquid crystal handwriting board driving chip, used for current amplifying the signal output by the voltage shifter and outputting a driving signal to the liquid crystal handwriting board; A clock generating circuit connected to the detection circuit and used for generating a reference clock according to the key trigger signal; A boost switch tube for boosting the input voltage; A boost control circuit connected to the clock generation circuit and the boost switch tube and used to control the boost switch tube, An overcurrent protection circuit for detecting the current of a boost switch tube and shutting down the boost switch tube when the current exceeds a preset current value; the overcurrent protection circuit is connected to a boost control circuit and a boost module outside the chip; the overcurrent protection circuit prevents the switch tube from being damaged by overcurrent by detecting the current of the boost switch tube; the boost control circuit receives a clock signal sent by a clock generation circuit and transmits it to the boost switch tube, and the boost switch tube cooperates with the peripheral boost module to boost the VCC voltage to the required diaphragm erase voltage, and transmits it back to a voltage shifter and a drive circuit to provide voltage for the voltage shifter and the drive circuit; the voltage shifter converts a low-voltage signal into a high-voltage signal and transmits it to the drive circuit.

2. The liquid crystal handwriting tablet driver chip according to claim 1, characterized in that: Also includes: An overvoltage protection circuit for detecting the voltage boosted by the boost module and shutting down the boost switch tube when the voltage exceeds a first voltage preset value; The overvoltage protection circuit is connected to the boost control circuit and the boost module outside the chip.

3. The liquid crystal handwriting tablet driver chip according to claim 2, characterized in that: Also includes: A voltage detection circuit is used to detect the voltage boosted by the boost module and shut down the boost control circuit when the voltage is higher than a second voltage preset value; the voltage detection circuit is connected to the boost control circuit, the detection circuit and the boost module outside the chip.

4. The liquid crystal handwriting tablet driver chip according to claim 3, characterized in that: Also includes: A voltage reference circuit connected to the voltage detection circuit and used to provide a reference voltage; A reset circuit for providing a reset signal; the reset circuit is respectively connected to each circuit in the liquid crystal handwriting board driver chip.

5. An application circuit of a liquid crystal handwriting tablet driver chip, characterized in that: A liquid crystal handwriting tablet driver chip comprising any one of claims 1 to 4; A voltage boost module connected to the LCD handwriting board driver chip and used for boosting voltage in combination with the LCD handwriting board driver chip; A key module connected to the LCD handwriting board driver chip and used to send key pulses; A filtering unit connected to the LCD handwriting board driver chip and used for filtering; An output control unit connected to the LCD handwriting board driver chip and the boost module and used to determine the output voltage of the boost circuit composed of the boost module and the LCD handwriting board driver chip; The liquid crystal handwriting board driving chip is also connected to the liquid crystal handwriting board.

6. The application circuit of the liquid crystal handwriting board driver chip according to claim 5, characterized in that: The boost module includes a first capacitor, a first inductor and a first diode; one end of the first inductor is connected to the input end of the first diode and the second pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded; The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded; The output control unit includes a first resistor, one end of the first resistor is connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the third pin of the liquid crystal handwriting board driver chip; The key module includes a first key, one end of which is connected to a KEY pin of a liquid crystal handwriting board driving chip, and the other end of which is grounded.

7. The application circuit of the liquid crystal handwriting board driver chip according to claim 5, characterized in that: The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the second pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded; The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded; The output control unit includes a first resistor, one end of the first resistor is connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first resistor is connected to the third pin of the liquid crystal handwriting board driver chip; The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

8. The application circuit of the liquid crystal handwriting board driver chip according to claim 5, characterized in that: The application circuit further includes a first indicator light, wherein an input end of the first indicator light is connected to an LED pin of the liquid crystal handwriting board, and an output end of the first indicator light is grounded; The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the second pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded; The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded; The output control unit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is connected to the fifth pin of the liquid crystal handwriting board driver chip, one end of the second resistor is connected to the sixth pin of the liquid crystal handwriting board driver chip, the other end of the first resistor and the other end of the second resistor are both connected to one end of the third resistor and the seventh pin of the liquid crystal handwriting board driver chip, and the other end of the third resistor is connected to the VOUT pin of the liquid crystal handwriting board driver chip; The key module includes a first key and a second key, one end of the first key is connected to the KEY1 pin of the liquid crystal handwriting board driver chip, and the other end of the first key is grounded, one end of the second key is connected to the KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded.

9. The application circuit of the liquid crystal handwriting board driver chip according to claim 5, characterized in that: The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the second pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded; The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded; The key module includes a first key, a second key, and a first resistor, one end of the first key is connected to a KEY1 pin of a liquid crystal handwriting board driver chip, the other end of the first key is grounded, one end of the second key is connected to one end of a first resistor, the other end of the first resistor is connected to a KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded; The application circuit also includes a first indicator light and a second resistor, the input end of the first indicator light is connected to a power supply, the output end of the first indicator light is connected to one end of the second resistor, and the second resistor is connected to a KEY2 pin of the liquid crystal handwriting board.

10. The application circuit of the liquid crystal handwriting board driver chip according to claim 5, characterized in that: The boost module includes a first capacitor, a first inductor and a first diode, one end of the first inductor is connected to the input end of the first diode and the second pin of the liquid crystal handwriting board driver chip, the other end of the first inductor is connected to the power supply, the VDD pin of the liquid crystal handwriting board driver chip and the filter unit, the output end of the first diode is connected to the output control unit, one end of the first capacitor and the VOUT pin of the liquid crystal handwriting board driver chip, and the other end of the first capacitor is grounded; The filtering unit includes a second capacitor, one end of the second capacitor is connected to a power supply, the other end of the first inductor and a VDD pin of a liquid crystal handwriting board driver chip, and the other end of the second capacitor is connected to a GND pin of the liquid crystal handwriting board driver chip and is grounded; The output control unit includes a first resistor and a second resistor, one end of the first resistor and one end of the second resistor are both connected to one end of the first capacitor, the output end of the first diode and the VOUT pin of the liquid crystal handwriting board driver chip, the other end of the first resistor is connected to the third pin of the liquid crystal handwriting board driver chip, and the other end of the second resistor is connected to the sixth pin of the liquid crystal handwriting board driver chip; The key module includes a first key, a second key, and a third resistor, one end of the first key is connected to a KEY1 pin of a liquid crystal handwriting board driver chip, the other end of the first key is grounded, one end of the second key is connected to one end of a third resistor, the other end of the third resistor is connected to a KEY2 pin of the liquid crystal handwriting board driver chip, and the other end of the second key is grounded; The application circuit also includes a first indicator light and a fourth resistor, the input end of the first indicator light is connected to a power supply, the output end of the first indicator light is connected to one end of a fourth resistor, and the fourth resistor is connected to a KEY2 pin of the liquid crystal handwriting board.

11. A liquid crystal handwriting tablet, characterized in that: It comprises a liquid crystal handwriting tablet driver chip and an application circuit of the liquid crystal handwriting tablet driver chip as described in any one of claims 1 to 10.

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