CN119200885A - Fully isolated touch screen USB interface circuit and method - Google Patents

Abstract

The invention discloses a fully isolated touch screen USB interface circuit and a method, which relate to the technical field of isolation and comprise the following steps: the upper isolation control module receives the USB bus data positive and negative signals sent by the computer module, 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 LSO# pin of the isolation control chip is a USB transmission speed selection input pin, the LSO# pin is a USB transmission speed automatic detection result output pin, automatic identification of the USB speed is realized, the pure hardware solution is completely real-time and transparent to the USB protocol, no additional filtering or signal conditioning circuit is needed to reduce the influence of the USB protocol, and the transmission path of common mode and differential mode interference in the device through the USB interface is effectively isolated from the signal and the power supply.

Description

Fully isolated touch screen USB interface circuit and method

Technical Field

The invention relates to the technical field of isolation, in particular to a fully-isolated touch screen USB interface circuit and a fully-isolated touch screen USB interface method.

Background

The fully isolated touch screen USB interface circuit aims to improve the safety and stability of equipment, especially in industrial control, medical equipment and military applications. Through electrical isolation, ground circulation, noise interference and voltage impact can be effectively prevented, and sensitive electronic elements are protected. The technology not only prolongs the service life of equipment, but also reduces the fault risk and ensures the reliability of data transmission. Along with the popularization of intelligent equipment, the isolation technology has more remarkable significance in guaranteeing the safety of man-machine interaction, provides a safer operation environment for users, and promotes the wide application of the touch screen technology.

In some special working environments, the conventional touch screen USB interface circuit and method are easy to be interfered by electromagnetic fields, so that the touch screen can erroneously identify the position of a finger, and misoperation is caused, and in some touch screen USB interface circuits, the influence is reduced through additional filtering or signal conditioning circuits, but the real-time and transparency of a USB protocol are difficult to ensure, even the isolation is incomplete, so that the touch screen USB interface circuit and method are needed to be provided for solving the problems.

Disclosure of Invention

In order to solve the technical problems, the technical scheme provides a fully isolated touch screen USB interface circuit and a fully isolated touch screen USB interface method, and solves the problems that in the prior art, the existing touch screen USB interface circuit and the existing touch screen USB interface method are easy to be interfered by electromagnetic fields in some special working environments, so that the touch screen can erroneously identify the positions of fingers, misoperation is caused, the influence on some touch screen USB interface circuits can be reduced through additional filtering or signal conditioning circuits, but the real-time and transparency of USB protocols are difficult to ensure, and even the isolation is incomplete.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a fully isolated touch screen USB interface circuit, comprising:

The computer module sends out positive and negative signals of USB bus data;

The upper isolation control module receives positive and negative data signals of USB bus data sent by the computer module, 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 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 signals and logic negative signals and is electrically connected with a lower isolation control module, and the lower isolation control module outputs USB bus data positive signals and USB bus data negative signals to the touch screen control module.

In an alternative embodiment, the touch screen control module outputs positive and negative signals of the USB bus data and transmits the positive and negative signals to the lower isolation control module, the lower isolation control module outputs two paths of 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 the logic positive signal and the logic negative signal to the upper isolation control module, and the upper isolation control module outputs the positive and negative signals of the USB bus data to the computer module after receiving the logic positive signal and the logic negative signal.

In an alternative embodiment, the power anode and the power ground of the computer module are input into the upper isolation control module, and the computer module is electrically connected with the input end of the isolation power module, and the isolation power module outputs the isolated power anode and the power ground and is electrically connected with the lower isolation control module, and the isolation power module is electrically connected with the touch screen control module.

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, a first pin and a second pin of the upper isolation control chip are respectively and electrically connected with a second voltage transient suppression diode and a first voltage transient suppression diode, the first voltage transient suppression diode and the second voltage transient suppression diode are used for protecting a communication circuit and are respectively connected in parallel between a USB bus data positive pole, a USB bus data negative pole and a power supply ground pole, a third pin of the upper isolation control chip is electrically connected with a third capacitor, a fourth pin of the first connector is electrically connected with a first capacitor and a second capacitor, and the first capacitor, the second capacitor and the third capacitor are all power supply decoupling capacitors.

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

In an alternative embodiment, a first photoelectric coupling unit and a second photoelectric coupling unit are disposed 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 a second pin and a third pin of the fifth isolation chip, a fifth resistor is serially connected to the third pin of the fifth isolation chip, a fourteenth capacitor and a sixth resistor are respectively electrically connected to the fifth pin and the sixth pin of the fifth isolation chip, a thirteenth capacitor is electrically connected between the second pin and the third pin of the sixth isolation chip, a seventh resistor is serially connected to the third pin of the sixth isolation chip, and a sixteenth capacitor and an eighth resistor are respectively electrically connected to the fifth pin and the sixth pin of the sixth isolation chip.

In an alternative embodiment, the second optocoupler unit includes a third isolation chip and a second isolation chip, a fourth capacitor is electrically connected between a second pin and a third pin of the second isolation chip, and the third pin of the second isolation chip is connected in series with a first resistor, a fifth pin and a sixth pin of the second isolation chip are respectively connected in electrical connection with a fifth capacitor and a second resistor, 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 respectively connected in electrical connection with a seventh capacitor and a fourth resistor.

In an alternative embodiment, the first optocoupler unit and the second optocoupler unit optimize symmetry between rising edges and falling edges of the optocoupler output signals by adjusting a fifth resistor, a thirteenth capacitor, a seventh resistor, a fifteenth capacitor, a first resistor, a fourth capacitor, a third resistor and a sixth capacitor, wherein the fifth capacitor, the seventh capacitor, the fourteenth capacitor and the sixteenth capacitor are decoupling capacitors, and the second resistor, the fourth resistor, the sixth resistor and the eighth resistor are pull-up resistors at the output ends of the optocoupler.

In an alternative embodiment, the fourth pin of the first connector in the upper isolation control module is connected to the isolation power module through a pi-type filter circuit, the isolation power module includes an isolation power chip, the first pin of the isolation power chip is electrically connected with the fourth pin of the first connector in the upper isolation control module, the pi-type filter 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 a power ground of the computer module, the fifth pin of the isolation power chip is electrically connected to a power ground of the touch control module, the second pin and the fifth pin of the isolation power chip are electrically connected with a seventeenth capacitor, the seventh pin of the isolation power chip outputs an isolated power, and the first pin of the isolation power chip is electrically connected with an eleventh capacitor and a twelfth capacitor.

Furthermore, a fully isolated touch screen USB interface method is provided, which is used for realizing the interface circuit, and comprises the following steps:

The signal isolation between the upper isolation control module and the lower isolation control module is realized through the first photoelectric coupling unit and the second photoelectric coupling unit, and the USB signal of the upper isolation control module is transmitted to the lower isolation control module after being converted by the first photoelectric coupling unit, and vice versa;

The USB signals are transmitted in two directions between the upper isolation control module and the lower isolation control module, and the signals are isolated and converted by using the first photoelectric coupling unit and the second photoelectric coupling unit in each direction;

The power supply of the upper isolation control module is isolated through the isolation power supply module and then supplied to the lower isolation control module and the touch screen controller, so that the independence of the power supply and signals is ensured;

The first photoelectric coupling unit and the second photoelectric coupling unit are used for improving the resistance of the circuit to electromagnetic interference and ensuring the stability of signal transmission.

Compared with the prior art, the invention has the beneficial effects that:

According to the fully-isolated touch screen USB interface circuit and the fully-isolated touch screen USB interface method, the influence of electromagnetic field interference in a working environment is reduced through the photoelectric couplers in the first photoelectric coupling unit and the second photoelectric coupling unit, and the influence of speed and speed symmetry of the photoelectric coupling on signal hysteresis and balance is reduced by adjusting parameters of the first resistor/fourth capacitor, the third resistor/sixth capacitor, the fifth resistor/thirteenth capacitor and the seventh resistor/fifteenth capacitor;

According to the fully-isolated touch screen USB interface circuit and the fully-isolated touch screen USB interface method, the LSI# pin of the isolation control chip is used for selecting the input pin for USB transmission speed, the input low level is 1.5Mbps of USB low speed, the input high level is 12Mbps of USB full speed, the LSO# pin of the isolation control chip is used for outputting the result of automatic detection of the USB transmission speed, the output low level is 1.5Mbps of USB low speed, the high level is 12Mbps of USB full speed, automatic identification of the USB speed is achieved, a pure hardware solution is realized, the USB protocol is fully real-time and transparent, no additional filtering or signal conditioning circuit is needed for reducing the influence of the USB interface circuit, and the path of internal common mode and differential mode interference of equipment through the USB interface is effectively isolated from signals and power sources.

According to the fully-isolated touch screen USB interface circuit and the method, protection of a USB communication line is achieved through the voltage transient suppression diodes in the upper computer isolation control circuit and the lower computer isolation control circuit, and meanwhile electromagnetic interference caused by voltage spikes is reduced through suppression of transient voltages.

Drawings

FIG. 1 is a block diagram of a proposed fully isolated touch screen USB interface circuit of the present invention;

FIG. 2 is a schematic diagram of an upper computer isolation control circuit according to the present invention;

FIG. 3 is a schematic diagram of a lower computer isolation control circuit according to the present invention;

FIG. 4 is a schematic diagram of a first photo-coupling unit according to the present invention;

FIG. 5 is a schematic diagram of a second photo-coupling unit according to the present invention;

fig. 6 is a schematic diagram of an isolated power module in the present invention.

Detailed Description

The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art.

Referring to fig. 1-6, a fully isolated touch screen USB interface circuit, comprising:

the computer module sends out a USB bus data positive and negative signal;

the upper isolation control module receives positive and negative signals (USB_D+ and USB_D-) of USB bus data sent by the computer module, a first photoelectric coupling unit is arranged in the upper isolation control module, and the upper isolation control module outputs two paths of signals (OPOP _PC and OPON_PC) to drive the first photoelectric coupling unit;

the first photoelectric coupling unit is composed of an infrared light emitting diode and a photosensitive detection integrated circuit, outputs the isolated logic positive signals and logic negative signals and is electrically connected with the lower isolation control module, and the lower isolation control module outputs USB bus data positive and data negative signals to the touch screen control module.

Specifically, the upper isolation control module is internally provided with a current driving circuit of the first photoelectric coupling unit, and outputs two paths of signals (OPOP _PC and OPON_PC) to drive the first photoelectric coupling unit. The first photoelectric coupling unit consists of a GaAsP infrared light emitting diode with high emission intensity and a high-speed high-gain photosensitive detection integrated circuit, and the first photoelectric coupling unit and the second photoelectric coupling unit can be 2 single-path or 1 double-path photoelectric couplers, and the optical couplers cannot be affected by electromagnetic field interference in a working environment.

Further, the touch screen control module outputs positive and negative signals of USB bus data and transmits the positive and negative signals to the lower isolation control module, the lower isolation control module outputs two paths of 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 the logic positive signal and the logic negative signal to the upper isolation control module, and the upper isolation control module outputs the positive and negative signals of the USB bus data to the computer module after receiving the logic positive signal and the logic negative signal.

Specifically, a fully-isolated touch screen USB interface circuit is arranged in the touch screen control module, 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 or USB Low-Speed and provides USB transmission status indication. The pure hardware solution is completely real-time and transparent to the USB protocol, and does not need to additionally install any driver. And the transmission path of common mode and differential mode interference in the equipment through the USB interface is effectively isolated. The touch control integrated machine device is provided with a solution for solving the problem of touch jumping.

Further, the positive power pole and the ground power pole of the computer module are input into the upper isolation control module, meanwhile, the computer module is electrically connected with the input end of the isolation power module, the isolation power module outputs the isolated positive power pole and the isolated ground power pole and is electrically connected with the lower isolation control module, and meanwhile, the isolation power module is electrically connected with the touch screen control module.

Further, the upper isolation control module includes an upper isolation control chip U1 and a first connector J1, where 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, a first pin and a second pin of the upper isolation control chip U1 are respectively electrically connected with a second voltage transient suppression diode TVS2 and a first voltage transient suppression diode TVS1, the first voltage transient suppression diode TVS1 and the second voltage transient suppression diode TVS2 are used for protecting a communication line, and are respectively connected in parallel between a USB bus data positive electrode, a USB data negative electrode and a power supply ground electrode, a third pin of the upper isolation control chip U1 is electrically connected with a third capacitor C3, a fourth pin of the first connector J1 is electrically connected with a first capacitor C1 and a second capacitor C2, and the first capacitor C1 and the third capacitor C2 are power supply decoupling capacitors.

Further, the lower isolation control module includes a lower isolation control chip U7 and a second connector J2, the second connector J2 is opened with a port for connecting to the touch screen control module, the first pin and the second pin of the lower isolation control chip U7 are respectively electrically connected with a fourth voltage transient suppression diode TVS4 and a third voltage transient suppression diode TVS3, the fourth voltage transient suppression diode TVS4 and the third voltage transient suppression diode TVS3 are used for protecting a communication line, 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, the data negative and the power ground, the third pin of the lower isolation control chip U7 is electrically connected with a twentieth capacitor C20, the second pin of the lower isolation control chip U7 is electrically connected with an eighteenth capacitor C18 and a nineteenth capacitor C19, and the nineteenth capacitor C19 are all power decoupling capacitors, and the eleventh capacitor C20 are electrically connected with the ninth LED1 through the eleventh pin of the lower isolation control chip U7.

Specifically, the up# pin of the lower isolation control chip U7 is a mode selection input, and a pull-UP resistor is built in the control chip to connect with a 5V power supply (high level) to be in a lower computer mode. The ACT# pin of the lower isolation control chip U7 is output in a USB transmission state, is low-level and effective, is internally provided with a pull-up resistor, is connected with a ninth resistor R9 current-limiting resistor in series, and is connected with an LED1 light-emitting diode for indicating the USB transmission state.

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

Specifically, the model of the optocoupler can be a single-channel or dual-channel high-speed optocoupler. An optocoupler with a transmission rate greater than 10Mbit is selected for isolation of 12Mbps full speed USB signals. The influence of the speed and the speed symmetry of the optocoupler on the signal hysteresis and the balance is considered. The symmetry between the rising edge and the falling edge of the output signal of the optocoupler is optimized 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.

Further, the second optocoupler unit includes a third isolation chip U3 and a second isolation chip U2, a fourth capacitor C4 is electrically connected between a second pin and a third pin of the second isolation chip U2, a first resistor R1 is connected in series with a third pin of the second isolation chip U2, a fifth capacitor C5 and a second resistor R2 are electrically connected with a fifth pin and a sixth pin of the second isolation chip U2, a sixth capacitor C6 is electrically connected between a second pin and a third pin of the third isolation chip U3, a third resistor R3 is connected in series with a third pin of the third isolation chip U3, and a seventh capacitor C7 and a fourth resistor R4 are electrically connected with a fifth pin and a sixth pin of the third isolation chip U3.

Further, the first photocoupling unit and the second photocoupling unit optimize symmetry between rising edges and falling edges of the optocoupler output signals by adjusting a fifth resistor R5, a thirteenth capacitor C13, a seventh resistor R7, a fifteenth capacitor C15, a first resistor R1, a fourth capacitor C4, a third resistor R3 and a sixth capacitor C6, the fifth capacitor C5, the seventh capacitor C7, a fourteenth capacitor C14 and the sixteenth capacitor C16 are decoupling capacitors, and the second resistor R2, the fourth resistor R4, the sixth resistor R6 and the eighth resistor R8 are pull-up resistors at the optocoupler output ends.

Further, a fourth pin of the first connector J1 in the upper isolation control module is connected to the isolation power module through a pi-type filter circuit, the isolation power module comprises an isolation power chip U4, a first pin of the isolation power chip U4 is electrically connected with a fourth pin of the first connector J1 in the upper isolation control module, the pi-type filter circuit is composed of an eighth capacitor C8, a ninth capacitor C9, a tenth capacitor C10 and a first inductor L1, a second pin of the isolation power chip U4 is electrically connected with a power ground electrode of the computer module, a fifth pin of the isolation power chip U4 is electrically connected with a power ground electrode of the touch control module, the second pin and the fifth pin of the isolation power chip U4 are electrically connected with a seventeenth capacitor C17, an isolated power is output by a seventh pin of the isolation power chip U4, and the first pin of the isolation power chip U4 is electrically connected with an eleventh capacitor C11 and a twelfth capacitor C12.

Specifically, the upper isolation control chip U1 and the lsi# pin (fourth pin) of the lower isolation control chip U7 in the upper isolation control module and the upper isolation control module are USB transmission speed selection input pins, the input low level is USB low-speed 1.5Mbps, and the input high level is USB full-speed 12Mbps. The LSO# pins (fifth pins) of the upper isolation control chip U1 and the lower isolation control chip U7 are USB transmission speed automatic detection result output pins, the output low level is USB low-speed 1.5Mbps, and the high level is USB full-speed 12Mbps. In the example, the LSO# pins in the upper isolation control chip U1 and the lower isolation control chip U7 are directly connected to the LSO# pins, so that the automatic identification of the USB speed is realized. If only a certain speed needs to be supported, lsi# may be forced directly to a low or high level.

Furthermore, a fully isolated touch screen USB interface method is provided, which is used for realizing the interface circuit, and comprises the following steps:

The signal isolation between the upper isolation control module and the lower isolation control module is realized through the first photoelectric coupling unit and the second photoelectric coupling unit, and the USB signal of the upper isolation control module is transmitted to the lower isolation control module after being converted by the first photoelectric coupling unit, and vice versa;

The USB signals are transmitted in two directions between the upper isolation control module and the lower isolation control module, and the signals are isolated and converted by using the first photoelectric coupling unit and the second photoelectric coupling unit in each direction;

The power supply of the upper isolation control module is isolated through the isolation power supply module and then supplied to the lower isolation control module and the touch screen controller, so that the independence of the power supply and signals is ensured;

The first photoelectric coupling unit and the second photoelectric coupling unit are used for improving the resistance of the circuit to electromagnetic interference and ensuring the stability of signal transmission.

In summary, the first and second photocoupling units may be 2 single-path or 1 double-path photocouplers, the photocouplers are not affected by electromagnetic interference in the working environment, the first resistor/fourth capacitor, the third resistor/sixth capacitor, the fifth resistor/thirteenth capacitor and the seventh resistor/fifteenth capacitor are adjusted to optimize symmetry between rising edges and falling edges of photocoupler output signals, influence of Speed and Speed symmetry of photocouplers on signal hysteresis and balance is reduced, a fully isolated touch screen USB interface circuit is arranged in a touch screen control module, full-Speed or Low-Speed of USB can be automatically identified, USB transmission state indication is provided, a pure hardware solution is completely real-time and transparent to USB protocol, no additional filtering or signal conditioning circuit is needed to reduce influence, common mode interference in equipment is effectively isolated from signals and power sources, and a path of differential mode interference transmitted through the USB interface is provided for strengthening touch points of touch control integrated equipment.

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention, which is defined by the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. Fully isolated touch screen USB interface circuit, its characterized in that includes:

The computer module sends out positive and negative signals of USB bus data;

The upper isolation control module receives positive and negative data signals of USB bus data sent by the computer module, 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 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 signals and logic negative signals and is electrically connected with a lower isolation control module, and the lower isolation control module outputs USB bus data positive signals and USB bus data negative signals to the touch screen control module.

2. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The touch screen control module outputs positive and negative signals of USB bus data and transmits the positive and negative signals to the lower isolation control module, the lower isolation control module outputs two paths of 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 the logic positive signal and the logic negative signal to the upper isolation control module, and the upper isolation control module outputs the positive and negative signals of the USB bus data to the computer module after receiving the logic positive signal and the logic negative signal.

3. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The power anode and the power ground electrode of the computer module are input into the upper isolation control module, the computer module is electrically connected with the input end of the isolation power module, the isolation power module outputs the isolated power anode and the power ground electrode and is electrically connected with the lower isolation control module, and the isolation power module is electrically connected with the touch screen control module.

4. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The upper isolation control module comprises an upper isolation control chip and a first connector, wherein the first connector is provided with an open port for connecting a computer and the computer module, the upper isolation control chip shares a power supply with the computer through the first connector, a first pin and a second pin of the upper isolation control chip are respectively and electrically connected with a second voltage transient suppression diode and a first voltage transient suppression diode, the first voltage transient suppression diode and the second voltage transient suppression diode are used for protecting communication lines and are respectively connected between a USB bus data positive pole, a USB bus data negative pole and a power supply ground pole in parallel, a third pin of the upper isolation control chip is electrically connected with a third capacitor, a fourth pin of the first connector is electrically connected with a first capacitor and a second capacitor, and the first capacitor, the second capacitor and the third capacitor are all power supply decoupling capacitors.

5. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The lower isolation control module comprises a lower isolation control chip and a second connector, wherein a port for connecting the touch screen control module is opened on the second connector, a first pin and a second pin of the lower isolation control chip are respectively and electrically connected with a fourth voltage transient suppression diode and a third voltage transient suppression diode, the fourth voltage transient suppression diode and the third voltage transient suppression diode are used for protecting a communication line, the third voltage transient suppression diode and the fourth voltage transient suppression diode are respectively and parallelly connected between a USB bus data positive pole, a USB data negative pole and a power ground pole, a third pin of the lower isolation control chip is electrically connected with a twentieth capacitor, a second pin of the lower isolation control chip is electrically connected with an eighteenth capacitor and a nineteenth capacitor, the eighteenth capacitor and the twentieth capacitor are all power decoupling capacitors, and an eleventh pin of the lower isolation control chip is electrically connected with an anode of the first light emitting diode through a ninth resistor.

6. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

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

7. The fully isolated touch screen USB interface circuit of claim 6, specifically comprising:

The second photoelectric coupling unit comprises a third isolation chip and a second isolation chip, a fourth capacitor is electrically connected between a second pin and a third pin of the second isolation chip, a first resistor is connected in series with the third pin of the second isolation chip, a fifth capacitor and a second resistor are respectively electrically connected with a fifth pin and a sixth pin of the second isolation chip, a sixth capacitor is electrically connected between the second pin and the third pin of the third isolation chip, a third resistor is connected in series with the third pin of the third isolation chip, and a seventh capacitor and a fourth resistor are respectively electrically connected with the fifth pin and the sixth pin of the third isolation chip.

8. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The first photoelectric coupling unit and the second photoelectric coupling unit optimize symmetry between rising edges and falling edges of the optocoupler output signals by adjusting a fifth resistor, a thirteenth capacitor, a seventh resistor, a fifteenth capacitor, a first resistor, a fourth capacitor, a third resistor and a sixth capacitor, the fifth capacitor, the seventh capacitor, the fourteenth capacitor and the sixteenth capacitor are decoupling capacitors, and the second resistor, the fourth resistor, the sixth resistor and the eighth resistor are pull-up resistors at the optocoupler output ends.

9. The fully isolated touch screen USB interface circuit of claim 1, specifically comprising:

The fourth pin of the first connector in the upper isolation control module is connected to the isolation power module through a pi-type filter circuit, the isolation power module comprises an isolation power chip, the first pin of the isolation power chip is electrically connected with the fourth pin of the first connector in the upper isolation control module, the pi-type filter 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 with a power ground electrode of the computer module, the fifth pin of the isolation power chip is electrically connected with a power ground electrode of the touch control module, the second pin and the fifth pin of the isolation power chip are electrically connected with a seventeenth capacitor, the seventh pin of the isolation power chip outputs an isolated power, and the first pin of the isolation power chip is electrically connected with an eleventh capacitor and a twelfth capacitor.

10. A fully isolated touch screen USB interface method for implementing an interface circuit according to any one of claims 1-9, comprising:

The signal isolation between the upper isolation control module and the lower isolation control module is realized through the first photoelectric coupling unit and the second photoelectric coupling unit, and the USB signal of the upper isolation control module is transmitted to the lower isolation control module after being converted by the first photoelectric coupling unit, and vice versa;

The USB signals are transmitted in two directions between the upper isolation control module and the lower isolation control module, and the signals are isolated and converted by using the first photoelectric coupling unit and the second photoelectric coupling unit in each direction;

The power supply of the upper isolation control module is isolated through the isolation power supply module and then supplied to the lower isolation control module and the touch screen controller, so that the independence of the power supply and signals is ensured;

The first photoelectric coupling unit and the second photoelectric coupling unit are used for improving the resistance of the circuit to electromagnetic interference and ensuring the stability of signal transmission.