Fully-isolated touch screen USB interface circuit and method

Abstract

The invention discloses a fully-isolated touch screen USB interface circuit and method, and relates to the technical field of isolation, the fully-isolated touch screen USB interface circuit comprises a computer module, an upper isolation control module, a USB bus data positive signal, a USB bus data negative signal, a USB bus data positive signal, a USB bus data negative signal, a USB bus data positive signal, a USB bus data negative signal, a USB bus data positive signal, a USB bus data negative signal and a USB bus data negative signal, a first photoelectric coupling unit is arranged in the upper isolation control module, and the upper isolation control module outputs two paths of signals to drive the first photoelectric coupling unit. The device has the advantages that the LSI # pin of the isolation control chip in the isolation control module is the USB transmission speed selection input pin, and the LSO # pin is the USB transmission speed automatic detection result output pin, so that the automatic identification of the USB speed and a pure hardware solution are realized, the device is completely real-time and transparent to a USB protocol, an additional filtering or signal conditioning circuit is not needed, the influence is reduced, and the reliability of the device is improved. And common-mode and differential-mode interference in equipment is effectively isolated from a signal and a power supply, so that a transmission path through the USB interface is effectively isolated.

Description

Technical Field

[0001] The present invention relates to the field of isolation technology, and in particular to a fully isolated touch screen USB interface circuit and method. Background Art

[0002] The fully isolated touch screen USB interface circuit is designed to improve the safety and stability of the device, especially in industrial control, medical equipment and military applications. Through electrical isolation, ground loops, noise interference and voltage shocks can be effectively prevented to protect sensitive electronic components. This technology not only extends the life of the device, but also reduces the risk of failure and ensures the reliability of data transmission. With the popularization of smart devices, the significance of isolation technology in ensuring the safety of human-computer interaction has become increasingly prominent, providing users with a safer operating environment and promoting the widespread application of touch screen technology.

[0003] Existing touch screen USB interface circuits and methods are susceptible to interference from electromagnetic fields in some special working environments, which may cause the touch screen to misidentify the position of the finger, thereby causing erroneous operation. In some touch screen USB interface circuits, additional filtering or signal conditioning circuits are used to reduce the impact, but it is difficult to ensure the real-time and transparency of the USB protocol, and even lead to incomplete isolation. Therefore, it is necessary to provide a touch screen USB interface circuit and method to solve the above-mentioned problems. Summary of the invention

[0004] In order to solve the above technical problems, a fully isolated touch screen USB interface circuit and method are provided. The technical solution solves the problem that the existing touch screen USB interface circuit and method proposed in the above background technology are susceptible to interference from electromagnetic fields in some special working environments, which may cause the touch screen to incorrectly identify the position of the finger, thereby causing erroneous operation. In some touch screen USB interface circuits, additional filtering or signal conditioning circuits may be used to reduce the impact, but it is difficult to ensure the real-time and transparency of the USB protocol, and even lead to the problem of incomplete isolation.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: Fully isolated touch screen USB interface circuit, including: A computer module, wherein the computer module sends out USB bus data positive and data negative signals; An upper isolation control module, wherein the upper isolation control module receives a USB bus data positive signal and a data negative signal sent by the computer module, the upper isolation control module has a built-in first photoelectric coupling unit, and the upper isolation control module outputs two signals to drive the first photoelectric coupling unit; Among them, the first photoelectric coupling unit is composed of an infrared light-emitting diode and a photosensitive detection integrated circuit. The first photoelectric coupling unit outputs the isolated logic positive signal and the logic negative signal, and is electrically connected to the lower isolation control module. The lower isolation control module outputs the USB bus data positive and data negative signals to the touch screen control module.

[0006] In an optional embodiment, the touch screen control module outputs USB bus data positive and data negative signals and transmits them to the lower isolation control module. The lower isolation control module outputs two signals to drive the second photoelectric coupling unit. The second photoelectric coupling unit outputs a logic positive signal and a logic negative signal and transmits them to the upper isolation control module. After receiving the logic positive signal and the logic negative signal, the upper isolation control module outputs the USB bus data positive and negative signals to the computer module.

[0007] In an optional embodiment, the positive power pole and the power ground pole of the computer module are input into the upper isolation control module, and the computer module is electrically connected to the input end of the isolation power module. The isolation power module outputs the isolated positive power pole and the power ground pole, and is electrically connected to the lower isolation control module, and the isolation power module is electrically connected to the touch screen control module.

[0008] In an optional embodiment, the upper isolation control module includes an upper isolation control chip and a first connector, the first connector is provided with an open port for connecting a computer and a computer module, the upper isolation control chip shares a power supply with the computer through the first connector, the first pin and the second pin of the upper isolation control chip are electrically connected to a second voltage transient suppression diode and a first voltage transient suppression diode, respectively, and the first voltage transient suppression diode and the second voltage transient suppression diode are used for protection of communication lines, and are respectively connected in parallel between the USB bus data positive, data negative and the power ground, the third pin of the upper isolation control chip is electrically connected to a third capacitor, the fourth pin of the first connector is electrically connected to a first capacitor and a second capacitor, and the first capacitor, the second capacitor and the third capacitor are all power decoupling capacitors.

[0009] In an optional embodiment, the lower isolation control module includes a lower isolation control chip and a second connector, the second connector opens a port for connecting the touch screen control module, the first pin and the second pin of the lower isolation control chip are electrically connected to a fourth voltage transient suppression diode and a third voltage transient suppression diode, respectively, the fourth voltage transient suppression diode and the third voltage transient suppression diode are used for protection of communication lines, and the third voltage transient suppression diode and the fourth voltage transient suppression diode are respectively connected in parallel between the USB bus data positive, data negative and power ground, the third pin of the lower isolation control chip is electrically connected to the twentieth capacitor, the second pin of the lower isolation control chip is electrically connected to the eighteenth capacitor and the nineteenth capacitor, and the eighteenth capacitor, the nineteenth capacitor and the twentieth capacitor are all power decoupling capacitors, and the eleventh pin of the lower isolation control chip is electrically connected to the anode of the first light-emitting diode through the ninth resistor.

[0010] In an optional embodiment, a first photoelectric coupling unit and a second photoelectric coupling unit are provided between the upper isolation control module and the lower isolation control module, the first photoelectric coupling unit includes a sixth isolation chip and a fifth isolation chip, a thirteenth capacitor is electrically connected between the second pin and the third pin of the fifth isolation chip, and the third pin of the fifth isolation chip is connected in series with a fifth resistor, the fifth pin and the sixth pin of the fifth isolation chip are electrically connected with a fourteenth capacitor and a sixth resistor, respectively, the second pin and the third pin of the sixth isolation chip are electrically connected with a thirteenth capacitor, and the third pin of the sixth isolation chip is connected in series with a seventh resistor, and the fifth pin and the sixth pin of the sixth isolation chip are electrically connected with a sixteenth capacitor and an eighth resistor, respectively.

[0011] In an optional embodiment, the second photoelectric coupling unit includes a third isolation chip and a second isolation chip, a fourth capacitor is electrically connected between the second pin and the third pin of the second isolation chip, and the third pin of the second isolation chip is connected in series with a first resistor, the fifth pin and the sixth pin of the second isolation chip are electrically connected to a fifth capacitor and a second resistor, respectively, a sixth capacitor is electrically connected between the second pin and the third pin of the third isolation chip, and the third pin of the third isolation chip is connected in series with a third resistor, and the fifth pin and the sixth pin of the third isolation chip are electrically connected to a seventh capacitor and a fourth resistor, respectively.

[0012] In an optional embodiment, the first photoelectric coupling unit and the second photoelectric coupling unit optimize the symmetry between the rising edge and the falling edge of the optocoupler output signal by adjusting the fifth resistor, the thirteenth capacitor, the seventh resistor, the fifteenth capacitor, the first resistor, the fourth capacitor, the third resistor and the sixth capacitor, the fifth capacitor, the seventh capacitor, the fourteenth capacitor and the sixteenth capacitor are all decoupling capacitors, and the second resistor, the fourth resistor, the sixth resistor and the eighth resistor are all pull-up resistors at the optocoupler output end.

[0013] In an optional embodiment, the fourth pin of the first connector in the upper isolation control module is connected to the isolation power module through a π-type filtering circuit, the isolation power module includes an isolation power chip, the first pin of the isolation power chip is electrically connected to the fourth pin of the first connector in the upper isolation control module, the π-type filtering circuit is composed of an eighth capacitor, a ninth capacitor, a tenth capacitor and a first inductor, the second pin of the isolation power chip is electrically connected to the power ground of the computer module, the fifth pin of the isolation power chip is electrically connected to the power ground of the touch control module, and the second pin and the fifth pin of the isolation power chip are electrically connected to the seventeenth capacitor, the seventh pin of the isolation power chip outputs isolated power, and the first pin of the isolation power chip is electrically connected to the eleventh capacitor and the twelfth capacitor.

[0014] Furthermore, a fully isolated touch screen USB interface method is proposed, which is used to implement the interface circuit as described above, including: The signal isolation between the upper isolation control module and the lower isolation control module is realized by the first photoelectric coupling unit and the second photoelectric coupling unit. The USB signal of the upper isolation control module is converted by the first photoelectric coupling unit and then transmitted to the lower isolation control module, and vice versa. The USB signal is bidirectionally transmitted between the upper isolation control module and the lower isolation control module, and the first photoelectric coupling unit and the second photoelectric coupling unit are used in each direction to isolate and convert the signal; Through the isolation power module, the power supply of the upper isolation control module is isolated and supplied to the lower isolation control module and touch screen controller to ensure the independence of power supply and signal; The first photoelectric coupling unit and the second photoelectric coupling unit are used to improve the circuit's resistance to electromagnetic interference and ensure the stability of signal transmission.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The fully isolated touch screen USB interface circuit and method proposed in this scheme reduce the influence of electromagnetic field interference in the working environment through the photoelectric coupler in the first photoelectric coupling unit and the second photoelectric coupling unit, and optimize the symmetry between the rising edge and the falling edge of the photocoupler output signal by adjusting the parameters of the first resistor / fourth capacitor, the third resistor / sixth capacitor, the fifth resistor / thirteenth capacitor, and the seventh resistor / fifteenth capacitor, thereby reducing the influence of the speed and speed symmetry of the photocoupler on the signal hysteresis and balance; The fully isolated touch screen USB interface circuit and method proposed in this scheme uses the LSI# pin of the isolation control chip as the USB transmission speed selection input pin, the input low level is USB low speed 1.5Mbps, and the input high level is USB full speed 12Mbps. The LSO# pin of the isolation control chip is the USB transmission speed automatic detection result output pin, the output low level is USB low speed 1.5Mbps, and the high level is USB full speed 12Mbps, thereby realizing automatic identification of USB speed. It is a pure hardware solution, which is completely real-time and transparent to the USB protocol, does not require additional filtering or signal conditioning circuits to reduce its impact, and effectively isolates the path of common mode and differential mode interference inside the device from the signal and power supply through the USB interface.

[0016] The fully isolated touch screen USB interface circuit and method proposed in this scheme protects the USB communication line through multiple voltage transient suppression diodes in the upper computer isolation control circuit and the lower computer isolation control circuit, and reduces the electromagnetic interference caused by voltage spikes by suppressing transient voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The module block diagram of the fully isolated touch screen USB interface circuit proposed by the present invention; Figure 2 It is a schematic diagram of the host computer isolation control circuit in the present invention; Figure 3 It is a schematic diagram of the isolation control circuit of the lower computer in the present invention; Figure 4 is a schematic diagram of a first photoelectric coupling unit in the present invention; Figure 5 is a schematic diagram of the second photoelectric coupling unit in the present invention; Figure 6 It is a schematic diagram of the isolated power supply module in the present invention. DETAILED DESCRIPTION

[0018] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0019] Reference Figure 1 - Figure 6 As shown, the fully isolated touch screen USB interface circuit includes: Computer module, the computer module sends out USB bus data positive and data negative signals; The upper isolation control module receives the USB bus data positive and data negative signals (USB_D+, USB_D-) sent by the computer module, and the upper isolation control module has a built-in first photoelectric coupling unit, and the upper isolation control module outputs two signals (OPOP_PC, OPON_PC) to drive the first photoelectric coupling unit; Among them, the first photoelectric coupling unit is composed of an infrared light emitting diode and a photosensitive detection integrated circuit. The first photoelectric coupling unit outputs the isolated logic positive signal and logic negative signal, and is electrically connected to the lower isolation control module. The lower isolation control module outputs the USB bus data positive and data negative signals to the touch screen control module.

[0020] Specifically, the upper isolation control module has a built-in current driving circuit of the first photoelectric coupling unit, and outputs two signals (OPOP_PC, OPON_PC) to drive the first photoelectric coupling unit. The first photoelectric coupling unit consists of a high-intensity GaAsP infrared light-emitting diode and a high-speed, high-gain photosensitive detection integrated circuit. The first photoelectric coupling unit and the second photoelectric coupling unit can be two single-channel or one dual-channel photoelectric couplers, and the photocouplers will not be affected by electromagnetic field interference in the working environment.

[0021] Furthermore, the touch screen control module outputs USB bus data positive and negative signals, and transmits them to the lower isolation control module. The lower isolation control module outputs two signals to drive the second photoelectric coupling unit. The second photoelectric coupling unit outputs logic positive and logic negative signals, and transmits them to the upper isolation control module. After receiving the logic positive and logic negative signals, the upper isolation control module outputs USB bus data positive and negative signals to the computer module.

[0022] Specifically, the touch screen control module is equipped with a fully isolated touch screen USB interface circuit, which supports 12Mbps full-speed USB transmission and 1.5Mbps low-speed USB transmission, is compatible with USB V2.0, can automatically identify USB full-speed Full-Speed ​​or USB low-speed Low-Speed, and provide USB transmission status indication. It is a pure hardware solution that is completely real-time and transparent to the USB protocol and does not require any additional driver installation. It effectively isolates the path of common-mode and differential-mode interference inside the device transmitted through the USB interface. It provides a solution to solve the touch jump point problem for reinforced touch-screen all-in-one devices.

[0023] Furthermore, the positive power pole and the power ground pole of the computer module are input into the upper isolation control module, and the computer module is electrically connected to the input end of the isolation power module. The isolation power module outputs the isolated positive power pole and the power ground pole, and is electrically connected to the lower isolation control module, and the isolation power module is electrically connected to the touch screen control module.

[0024] Furthermore, the upper isolation control module includes an upper isolation control chip U1 and a first connector J1. The first connector J1 is provided with an open port for connecting a computer and a computer module. The upper isolation control chip U1 shares a power supply with the computer through the first connector J1. The first pin and the second pin of the upper isolation control chip U1 are electrically connected to the second voltage transient suppression diode TVS2 and the first voltage transient suppression diode TVS1, respectively. The first voltage transient suppression diode TVS1 and the second voltage transient suppression diode TVS2 are used for protection of communication lines and are respectively connected in parallel between the USB bus data positive, data negative and the power ground. The third pin of the upper isolation control chip U1 is electrically connected to the third capacitor C3, and the fourth pin of the first connector J1 is electrically connected to the first capacitor C1 and the second capacitor C2. The first capacitor C1, the second capacitor C2 and the third capacitor C3 are all power decoupling capacitors.

[0025] Furthermore, the lower isolation control module includes a lower isolation control chip U7 and a second connector J2, the second connector J2 opens a port for connecting the touch screen control module, the first pin and the second pin of the lower isolation control chip U7 are respectively electrically connected to the fourth voltage transient suppression diode TVS4 and the third voltage transient suppression diode TVS3, the fourth voltage transient suppression diode TVS4 and the third voltage transient suppression diode TVS3 are used for protection of the communication line, and the third voltage transient suppression diode TVS3 and the fourth voltage transient suppression diode TVS4 are respectively connected in parallel between the USB bus data positive, data negative and the power ground, the third pin of the lower isolation control chip U7 is electrically connected to the twentieth capacitor C20, the second pin of the lower isolation control chip U7 is electrically connected to the eighteenth capacitor C18 and the nineteenth capacitor C19, and the eighteenth capacitor C18, the nineteenth capacitor C19 and the twentieth capacitor C20 are all power decoupling capacitors, and the eleventh pin of the lower isolation control chip U7 is electrically connected to the anode of the first light-emitting diode LED1 through the ninth resistor.

[0026] Specifically, the UP# pin of the lower isolation control chip U7 is the mode selection input, with a built-in pull-up resistor, connected to a 5V power supply (high level) for the lower machine mode. The ACT# pin of the lower isolation control chip U7 is the USB transmission status output, which is valid at low level, with a built-in pull-up resistor, connected in series with the ninth resistor R9 current limiting resistor, and then connected to the LED1 light emitting diode to indicate the USB transmission status.

[0027] Furthermore, a first photoelectric coupling unit and a second photoelectric coupling unit are provided between the upper isolation control module and the lower isolation control module, the first photoelectric coupling unit includes a sixth isolation chip U6 and a fifth isolation chip U5, a thirteenth capacitor C13 is electrically connected between the second pin and the third pin of the fifth isolation chip U5, and the third pin of the fifth isolation chip U5 is connected in series with a fifth resistor R5, the fifth pin and the sixth pin of the fifth isolation chip U5 are electrically connected to a fourteenth capacitor C14 and a sixth resistor R6, respectively, the thirteenth capacitor C13 is electrically connected between the second pin and the third pin of the sixth isolation chip U6, and the third pin of the sixth isolation chip U6 is connected in series with a seventh resistor R7, and the fifth pin and the sixth pin of the sixth isolation chip U6 are electrically connected to a sixteenth capacitor C16 and an eighth resistor R8, respectively.

[0028] Specifically, the model of the optocoupler can be selected as a single-channel or dual-channel high-speed optocoupler. Select an optocoupler with a transmission rate greater than 10Mbit for isolation of 12Mbps full-speed USB signals. Consider the impact of the speed and speed symmetry of the optocoupler on signal hysteresis and balance. By adjusting the parameters of the first resistor R1 / fourth capacitor C4, the third resistor R3 / sixth capacitor C6, the fifth resistor R5 / thirteenth capacitor C13, and the seventh resistor R7 / fifteenth capacitor C15, the symmetry between the rising edge and the falling edge of the optocoupler output signal is optimized.

[0029] Furthermore, the second optoelectronic coupling unit includes a third isolation chip U3 and a second isolation chip U2, a fourth capacitor C4 is electrically connected between the second pin and the third pin of the second isolation chip U2, and the third pin of the second isolation chip U2 is connected in series with a first resistor R1, the fifth pin and the sixth pin of the second isolation chip U2 are respectively electrically connected to a fifth capacitor C5 and a second resistor R2, a sixth capacitor C6 is electrically connected between the second pin and the third pin of the third isolation chip U3, and the third pin of the third isolation chip U3 is connected in series with a third resistor R3, and the fifth pin and the sixth pin of the third isolation chip U3 are respectively electrically connected to a seventh capacitor C7 and a fourth resistor R4.

[0030] Furthermore, the first photoelectric coupling unit and the second photoelectric coupling unit optimize the symmetry between the rising edge and the falling edge of the optocoupler output signal by adjusting the fifth resistor R5, the thirteenth capacitor C13, the seventh resistor R7, the fifteenth capacitor C15, the first resistor R1, the fourth capacitor C4, the third resistor R3 and the sixth capacitor C6. The fifth capacitor C5, the seventh capacitor C7, the fourteenth capacitor C14 and the sixteenth capacitor C16 are all decoupling capacitors, and the second resistor R2, the fourth resistor R4, the sixth resistor R6 and the eighth resistor R8 are all pull-up resistors at the output end of the optocoupler.

[0031] Furthermore, the fourth pin of the first connector J1 in the upper isolation control module is connected to the isolation power module through a π-type filtering circuit. The isolation power module includes an isolation power chip U4. The first pin of the isolation power chip U4 is electrically connected to the fourth pin of the first connector J1 in the upper isolation control module. The π-type filtering circuit is composed of an eighth capacitor C8, a ninth capacitor C9, a tenth capacitor C10 and a first inductor L1. The second pin of the isolation power chip U4 is electrically connected to the power ground of the computer module, the fifth pin of the isolation power chip U4 is electrically connected to the power ground of the touch control module, and the second pin and the fifth pin of the isolation power chip U4 are electrically connected to the seventeenth capacitor C17. The seventh pin of the isolation power chip U4 outputs isolated power, and the first pin of the isolation power chip U4 is electrically connected to the eleventh capacitor C11 and the twelfth capacitor C12.

[0032] Specifically, the LSI# pin (fourth pin) of the upper isolation control module and the upper isolation control chip U1 and the lower isolation control chip U7 in the upper isolation control module is the USB transmission speed selection input pin, the input low level is USB low speed 1.5Mbps, and the input high level is USB full speed 12Mbps. The LSO# pin (fifth pin) of the upper isolation control chip U1 and the lower isolation control chip U7 is the USB transmission speed automatic detection result output pin, the output low level is USB low speed 1.5Mbps, and the high level is USB full speed 12Mbps. In the example, the LSI# pin in the upper isolation control chip U1 and the lower isolation control chip U7 is directly connected to the LSO# pin, realizing automatic identification of USB speed. If only a certain speed needs to be supported, LSI# can be directly forced to a low or high level.

[0033] Furthermore, a fully isolated touch screen USB interface method is proposed to implement the above interface circuit, including: The signal isolation between the upper isolation control module and the lower isolation control module is realized by the first photoelectric coupling unit and the second photoelectric coupling unit. The USB signal of the upper isolation control module is converted by the first photoelectric coupling unit and then transmitted to the lower isolation control module, and vice versa. The USB signal is bidirectionally transmitted between the upper isolation control module and the lower isolation control module, and the first photoelectric coupling unit and the second photoelectric coupling unit are used in each direction to isolate and convert the signal; Through the isolation power module, the power supply of the upper isolation control module is isolated and supplied to the lower isolation control module and touch screen controller to ensure the independence of power supply and signal; The first photoelectric coupling unit and the second photoelectric coupling unit are used to improve the circuit's resistance to electromagnetic interference and ensure the stability of signal transmission.

[0034] In summary, the advantages of the present invention are that the first photoelectric coupling unit and the second photoelectric coupling unit can be two single-channel or one dual-channel photoelectric couplers, and the photoelectric couplers will not be affected by the electromagnetic field interference in the working environment. By adjusting the parameters of the first resistor / fourth capacitor, the third resistor / sixth capacitor, the fifth resistor / thirteenth capacitor, and the seventh resistor / fifteenth capacitor, the symmetry between the rising edge and the falling edge of the photocoupler output signal is optimized, and the speed and speed symmetry of the photocoupler are reduced. The influence of the signal hysteresis and balance, the touch screen control module is provided with a fully isolated touch screen USB interface circuit, which can automatically identify USB full-speed Full-Speed ​​or USB low-speed Low-Speed, and provide USB transmission status indication, a pure hardware solution, which is completely real-time and transparent to the USB protocol, does not require additional filtering or signal conditioning circuits to reduce its influence, and effectively isolates the path of the common mode and differential mode interference inside the device from the signal and power supply through the USB interface, providing a solution for strengthening the touch-control all-in-one device to solve the touch jump point problem.

[0035] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. Fully isolated touch screen USB interface circuit, characterized in that: include: A computer module, wherein the computer module sends out USB bus data positive and data negative signals; An upper isolation control module, wherein the upper isolation control module receives a USB bus data positive signal and a data negative signal sent by the computer module, the upper isolation control module has a built-in first photoelectric coupling unit, and the upper isolation control module outputs two signals to drive the first photoelectric coupling unit; Among them, the first photoelectric coupling unit is composed of an infrared light-emitting diode and a photosensitive detection integrated circuit. The first photoelectric coupling unit outputs the isolated logic positive signal and the logic negative signal, and is electrically connected to the lower isolation control module. The lower isolation control module outputs the USB bus data positive and data negative signals to the touch screen control module.

2. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The touch screen control module outputs USB bus data positive and data negative signals, and transmits them to the lower isolation control module, the lower isolation control module outputs two signals to drive the second photoelectric coupling unit, the second photoelectric coupling unit outputs a logic positive signal and a logic negative signal, and transmits them to the upper isolation control module, and the upper isolation control module outputs the USB bus data positive and negative signals to the computer module after receiving the logic positive signal and the logic negative signal.

3. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The positive power pole and the power ground pole of the computer module are input into the upper isolation control module, and the computer module is electrically connected to the input end of the isolation power module. The isolation power module outputs the isolated positive power pole and the power ground pole, and is electrically connected to the lower isolation control module, and the isolation power module is electrically connected to the touch screen control module.

4. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The upper isolation control module includes an upper isolation control chip and a first connector, wherein the first connector is provided with an open port for connecting a computer and a computer module, the upper isolation control chip shares a power supply with the computer through the first connector, the first pin and the second pin of the upper isolation control chip are electrically connected to a second voltage transient suppression diode and a first voltage transient suppression diode, respectively, and the first voltage transient suppression diode and the second voltage transient suppression diode are used for the protection of the communication line, and are respectively connected in parallel between the USB bus data positive, data negative and the power ground, the third pin of the upper isolation control chip is electrically connected to a third capacitor, the fourth pin of the first connector is electrically connected to a first capacitor and a second capacitor, and the first capacitor, the second capacitor and the third capacitor are all power decoupling capacitors.

5. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The lower isolation control module includes a lower isolation control chip and a second connector, the second connector opens a port for connecting the touch screen control module, the first pin and the second pin of the lower isolation control chip are electrically connected to a fourth voltage transient suppression diode and a third voltage transient suppression diode respectively, the fourth voltage transient suppression diode and the third voltage transient suppression diode are used for the protection of the communication line, and the third voltage transient suppression diode and the fourth voltage transient suppression diode are respectively connected in parallel between the USB bus data positive, data negative and the power ground, the third pin of the lower isolation control chip is electrically connected to the twentieth capacitor, the second pin of the lower isolation control chip is electrically connected to the eighteenth capacitor and the nineteenth capacitor, and the eighteenth capacitor, the nineteenth capacitor and the twenty-first capacitor are all power decoupling capacitors, and the eleventh pin of the lower isolation control chip is electrically connected to the anode of the first light-emitting diode through the ninth resistor.

6. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: A first photoelectric coupling unit and a second photoelectric coupling unit are provided between the upper isolation control module and the lower isolation control module, the first photoelectric coupling unit includes a sixth isolation chip and a fifth isolation chip, a thirteenth capacitor is electrically connected between the second pin and the third pin of the fifth isolation chip, and the third pin of the fifth isolation chip is connected in series with a fifth resistor, the fifth pin and the sixth pin of the fifth isolation chip are electrically connected with a fourteenth capacitor and a sixth resistor, respectively, the second pin and the third pin of the sixth isolation chip are electrically connected with a thirteenth capacitor, and the third pin of the sixth isolation chip is connected in series with a seventh resistor, and the fifth pin and the sixth pin of the sixth isolation chip are electrically connected with a sixteenth capacitor and an eighth resistor, respectively.

7. The fully isolated touch screen USB interface circuit according to claim 6, characterized in that: Specifically include: The second photoelectric coupling unit includes a third isolation chip and a second isolation chip, a fourth capacitor is electrically connected between the second pin and the third pin of the second isolation chip, and the third pin of the second isolation chip is connected in series with a first resistor, the fifth pin and the sixth pin of the second isolation chip are electrically connected to a fifth capacitor and a second resistor, respectively, a sixth capacitor is electrically connected between the second pin and the third pin of the third isolation chip, and the third pin of the third isolation chip is connected in series with a third resistor, and the fifth pin and the sixth pin of the third isolation chip are electrically connected to a seventh capacitor and a fourth resistor, respectively.

8. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The first photoelectric coupling unit and the second photoelectric coupling unit optimize the symmetry between the rising edge and the falling edge of the optocoupler output signal by adjusting the fifth resistor, the thirteenth capacitor, the seventh resistor, the fifteenth capacitor, the first resistor, the fourth capacitor, the third resistor and the sixth capacitor. The fifth capacitor, the seventh capacitor, the fourteenth capacitor and the sixteenth capacitor are all decoupling capacitors, and the second resistor, the fourth resistor, the sixth resistor and the eighth resistor are all pull-up resistors at the output end of the optocoupler.

9. The fully isolated touch screen USB interface circuit according to claim 1, characterized in that: Specifically include: The fourth pin of the first connector in the upper isolation control module is connected to the isolation power module through a π-type filtering circuit, the isolation power module includes an isolation power chip, the first pin of the isolation power chip is electrically connected to the fourth pin of the first connector in the upper isolation control module, the π-type filtering circuit is composed of an eighth capacitor, a ninth capacitor, a tenth capacitor and a first inductor, the second pin of the isolation power chip is electrically connected to the power ground of the computer module, the fifth pin of the isolation power chip is electrically connected to the power ground of the touch control module, and the second pin and the fifth pin of the isolation power chip are electrically connected to the seventeenth capacitor, the seventh pin of the isolation power chip outputs an isolated power supply, and the first pin of the isolation power chip is electrically connected to the eleventh capacitor and the twelfth capacitor.

10. A fully isolated touch screen USB interface method, used to implement the interface circuit according to any one of claims 1 to 9, characterized in that: include: The signal isolation between the upper isolation control module and the lower isolation control module is realized by the first photoelectric coupling unit and the second photoelectric coupling unit. The USB signal of the upper isolation control module is converted by the first photoelectric coupling unit and then transmitted to the lower isolation control module, and vice versa. The USB signal is bidirectionally transmitted between the upper isolation control module and the lower isolation control module, and the first photoelectric coupling unit and the second photoelectric coupling unit are used in each direction to isolate and convert the signal; Through the isolation power module, the power supply of the upper isolation control module is isolated and supplied to the lower isolation control module and touch screen controller to ensure the independence of power supply and signal; The first photoelectric coupling unit and the second photoelectric coupling unit are used to improve the circuit's resistance to electromagnetic interference and ensure the stability of signal transmission.

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