A switching circuit and KVM switch

Abstract

The utility model relates to switching circuit technical field, concretely relates to a switching circuit and switch. The circuit includes multichannel video input module, video processing module and video output module, and video processing module includes video processing chip, and the input of video processing chip is connected with multichannel video input module to receive multichannel video signal, and the output is connected with video output module, and video processing chip is built -in with the multiple storage units corresponding setting of multichannel video input module, and each storage unit is preloaded with the same preset expansion display identification data and multiple preset resolution templates, and video processing chip is used to receive multichannel and preset expansion display identification data matching video signal, and according to the resolution of the display device connected with video output module, calls preset resolution template and processes video signal, and the video signal after processing is output through video output module. The present application can avoid the black screen in the process of switching signal source, and improve user experience.

Description

Technical Field

[0001] This utility model relates to the field of switching circuit technology, and in particular to a switching circuit and a KVM switch. Background Technology

[0002] A KVM switch is a practical device that can easily switch and transmit signals from multiple signal source devices. It can control multiple signal source devices through a set of keyboard, monitor and mouse, and is suitable for various scenarios such as home, office, and laboratory.

[0003] When switching signal sources, KVM switches on the market need to renegotiate EDID (Extended Display Identification Data), which may cause a brief black screen on the display device. The time to display the image after switching is about 3 to 10 seconds or even longer, which will significantly affect the user experience. Especially in real-time interactive scenarios (such as games, meetings, and multi-screen collaboration), the delay will cause problems such as the disconnect between operation commands and screen feedback, and the lag in operation feedback, resulting in a poor user experience. Utility Model Content

[0004] This utility model provides a switching circuit and a KVM switch to solve the problem of a black screen appearing when the KVM switch switches the signal source, resulting in a poor user experience.

[0005] This utility model discloses a switching circuit, including a multi-channel video input module, a video processing module, and a video output module, wherein,

[0006] The multi-channel video input module is used to receive multiple video signals;

[0007] The video processing module includes a video processing chip. The input end of the video processing chip is connected to multiple video input modules to receive multiple video signals, and the output end is connected to the video output module. The video processing chip has multiple storage units corresponding to the multiple video input modules. Each storage unit is pre-loaded with the same preset extended display recognition data and multiple preset resolution templates. The video processing chip is used to receive multiple video signals that match the preset extended display recognition data, and to process the video signals according to the resolution of the display device connected to the video output module by calling the preset resolution templates, and then output the processed video signals through the video output module.

[0008] Optionally, the switching circuit further includes a main control module, a multi-channel USB input module, a first USB switching processing module, a multi-channel first USB expansion module, a KVM control module, and a multi-channel first USB output module. The multiple USB input modules are configured one-to-one with the multiple video input modules and connected to the first USB switching processing module to receive and transmit USB signals from the corresponding signal source devices. The multiple first USB expansion modules are configured one-to-one with the multiple USB input modules. The KVM control module is connected to the multiple first USB output modules and the multiple first USB expansion modules respectively. The main control module is connected to the video processing chip and the first USB switching processing module to control the switching state of the video processing chip and the first USB switching processing module.

[0009] Optionally, the switching circuit further includes a second USB expansion module, a second USB switching processing module, and a multi-channel second USB output module. The input terminal of the second USB expansion module is connected to the first USB switching processing module, and the output terminal is connected to the multi-channel second USB output module. The second USB switching processing module is also connected to the multi-channel first USB expansion module.

[0010] Optionally, the video input module includes an HDMI input interface, a first DDC processing circuit, an HPD output level conversion circuit, and a first electrostatic discharge (ESD) protection circuit. Both the first DDC processing circuit and the HPD output level conversion circuit are disposed between the HDMI input interface and the video processing chip. The first DDC processing circuit is used to communicate with an external signal source device through the HDMI input interface. The HPD output level conversion circuit is used to convert the first level signal output by the video processing chip into a second level signal and output it through the HDMI input interface. The HDMI input interface is also connected to the video processing chip to transmit the received video signal to the video processing chip. The first ESD protection circuit is disposed between the HDMI input interface and the video processing chip to absorb electrostatic current.

[0011] Optionally, the HPD output level conversion circuit includes a PNP transistor, an NPN transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The first resistor is connected in series between the collector of the PNP transistor and the HDMI input interface. One end of the second resistor is connected to the HDMI input interface, and the other end is grounded. The third resistor is connected in series between the emitter of the PNP transistor and the collector of the NPN transistor. The fourth resistor is connected in series between the base of the PNP transistor and the collector of the NPN transistor. One end of the fifth resistor is connected to the base of the NPN transistor, and the other end is used to receive a drive signal. The emitter of the PNP transistor is also connected to the video processing chip.

[0012] Optionally, the video output module includes an HDMI output interface, a second DDC processing circuit, an HPD input level conversion circuit, and a second electrostatic discharge (ESD) protection circuit. The HDMI output interface is connected to the video processing chip. The second ESD protection circuit and the HPD input level conversion circuit are both disposed between the HDMI output interface and the video processing chip. The second DDC processing circuit is used to communicate with an external display device through the HDMI output interface. The HPD input level conversion circuit is used to convert the third-level signal output by the video processing chip into a fourth-level signal and output it through the HDMI output interface. The second ESD protection circuit is used to absorb electrostatic current.

[0013] Optionally, the video output module further includes a current limiting protection circuit, which is disposed between the video processing chip and the HDMI output interface. The current limiting protection circuit is used to limit the current output through the HDMI output interface.

[0014] Optionally, the current limiting protection circuit includes a power switch chip, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a capacitor. The sixth resistor is connected in series between the video processing chip and the driving terminal of the power switch chip. One end of the seventh resistor is connected to the power supply, and the other end is connected to the driving terminal of the power switch chip. The eighth resistor is connected in series between the driving terminal of the power switch chip and the ground terminal. The ninth resistor is connected in series between the fault indication terminals of the power switch chip. The tenth resistor is connected in parallel with the capacitor. The first parallel node is connected to the output terminal of the power switch chip and the HDMI output interface.

[0015] Optionally, the USB input module includes a USB interface, a common-mode suppression circuit, a surge protection circuit, and a third electrostatic discharge (ESD) protection circuit. The USB interface is used to receive USB signals from external signal source devices. The third ESD protection circuit is disposed between the USB interface and the common-mode suppression circuit. The surge protection circuit is connected to the USB interface and is used to absorb surge current. The output terminal of the common-mode suppression circuit is connected to the video processing chip.

[0016] This utility model also discloses a KVM switch, including the switching circuit described in any of the above claims.

[0017] The beneficial effects of the switching circuit and KVM switch provided in this embodiment of the present invention are as follows: By setting up a multi-channel video input module, a video processing module, and a video output module, the video processing chip of the video processing module has built-in multiple storage units corresponding to the multi-channel video input module. Each storage unit is preloaded with the same preset extended display recognition data and multiple preset resolution templates. In this way, after the multi-channel video input module is connected to the corresponding signal source device, multiple signal source devices will output video signals that match the preset extended display recognition data. When switching signal source devices, there is no need to re-negotiate the extended display recognition data, and the preset resolution template can be directly used to quickly output video signals that match the devices connected to the video output module, avoiding black screens and improving user experience. Attached Figure Description

[0018] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0019] Figure 1 This is a structural block diagram of the switching circuit according to an embodiment of the present invention;

[0020] Figure 2 This is a structural block diagram of the video input module according to an embodiment of the present invention;

[0021] Figure 3 This is a structural block diagram of the video output module according to an embodiment of the present invention;

[0022] Figure 4 This is a structural block diagram of the USB input module according to an embodiment of the present invention;

[0023] Figure 5 This is a circuit diagram of the HDMI input interface according to an embodiment of the present invention;

[0024] Figure 6 This is a circuit diagram of the first electrostatic protection circuit according to an embodiment of the present invention;

[0025] Figure 7This is a circuit diagram of the first DDC processing circuit according to an embodiment of the present invention;

[0026] Figure 8 This is a circuit diagram of the HDP output level conversion circuit according to an embodiment of the present invention;

[0027] Figure 9 This is a circuit diagram of the current limiting protection circuit according to an embodiment of the present utility model;

[0028] Figure 10 This is a circuit diagram of the USB interface according to an embodiment of the present invention;

[0029] Figure 11 This is a circuit diagram of the third electrostatic protection circuit according to an embodiment of the present invention;

[0030] Figure 12 This is a circuit diagram of the surge protection circuit according to an embodiment of the present invention;

[0031] Figure 13 This is a circuit diagram of the common-mode suppression circuit according to an embodiment of the present invention.

[0032] The labels for the attached figures are as follows:

[0033] 10. Video input module; 11. First DDC processing circuit; 12. HPD output level conversion circuit; 13. First electrostatic discharge (ESD) protection circuit; 20. Video processing module; 30. Video output module; 31. Second DDC processing circuit; 32. HPD input level conversion circuit; 33. Second ESD protection circuit; 34. Current limiting protection circuit; 40. Main control module; 50. USB input module; 51. Common-mode rejection circuit; 52. Surge protection circuit; 53. Third ESD protection circuit; 60. First USB switching processing module; 70. First USB expansion module; 80. KVM control module; 90. First USB output module; 110. Second USB expansion module; 120. Second USB switching processing module; 130. Second USB output module;

[0034] U1, Video processing chip; J1, USB interface; P1, HDMI input interface; P2, HDMI output interface; Q1, PNP transistor; Q2, NPN transistor; R1, First resistor; R2, Second resistor; R3, Third resistor; R4, Fourth resistor; R5, Fifth resistor; U2, Power switch chip; R6, Sixth resistor; R7, Seventh resistor; R8, Eighth resistor; R9, Ninth resistor; R10, Tenth resistor; C1, Capacitor. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The preferred embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0036] This utility model embodiment provides a switching circuit, such as Figure 1 As shown, the switching circuit includes a multi-channel video input module 10, a video processing module 20, and a video output module 30.

[0037] The multi-channel video input module 10 is used to receive multiple video signals. Each video input module 10 can be connected to a corresponding signal source device to obtain video signals from the signal source device.

[0038] The video processing module 20 includes a video processing chip U1. The input terminal of the video processing chip U1 is connected to the multi-channel video input module 10 to receive multiple video signals, and the output terminal is connected to the video output module 30. The video processing chip U1 has multiple storage units corresponding to the multi-channel video input module 10. Each storage unit is preloaded with the same preset extended display recognition data and multiple preset resolution templates. The video processing chip U1 is used to receive multiple video signals that match the preset extended display recognition data, and to process the video signals by calling the preset resolution templates according to the resolution of the display device connected to the video output module 30, and then output the processed video signals through the video output module 30.

[0039] The switching circuit of this embodiment comprises a multi-channel video input module 10, a video processing module 20, and a video output module 30. The video processing chip U1 of the video processing module 20 has multiple built-in storage units corresponding to the multi-channel video input module 10. Each storage unit is pre-loaded with the same preset extended display recognition data and multiple preset resolution templates. Thus, when the multi-channel video input module 10 is connected to a corresponding signal source device, multiple signal source devices will output video signals matching the preset extended display recognition data. When switching signal source devices, there is no need to renegotiate the extended display recognition data, and the preset resolution templates can be directly used to quickly output video signals matching the devices connected to the video output module 30, avoiding black screens and improving user experience. This switching circuit is applicable to data centers, multimedia production, and multi-host collaborative work scenarios.

[0040] Specifically, multiple storage units in the video processing chip U1 are pre-loaded with the same preset extended display recognition data. When the multi-channel video input module 10 is connected to the corresponding signal source device, the signal source device will output a matching video signal according to the preset extended display recognition data. The video processing chip U1 also identifies the resolution of the display device connected to the video output module 30, directly calls the preset resolution template corresponding to that resolution to process the acquired video signal, obtains a video signal matching the resolution of the display device, achieves fast output, and eliminates black screen. Furthermore, the solution of this embodiment can also be applied to different display devices.

[0041] Optionally, the preset extended display recognition data can be the extended display recognition data corresponding to the highest resolution, such as the extended display recognition data corresponding to 4K resolution, to dynamically disguise it as a virtual 4K display device, so that the signal source device outputs a 4K resolution video signal. It can be backward compatible with different resolutions through various preset resolution templates, thereby avoiding problems such as image blurring and aspect ratio distortion.

[0042] Optionally, the video processing chip U1 in this embodiment can be implemented using existing chips, such as the MS1826. Using the MS1826 chip also enables the segmentation of the displayed image on the same display device, that is, displaying different numbers of images such as four, two, or a single image on the same display device, to display video signals from different signal sources simultaneously. Therefore, this application can also achieve ultra-low latency image segmentation. The MS1826 chip also supports cable equalizer gain control, adaptive gain adjustment, and downscaler (resolution reduction) functions, enabling gain control, dynamic phase compensation, and intelligent frame interpolation detection to generate transition frames and avoid image jumps.

[0043] Optionally, the number of video input modules 10 can be two, three, four, or more, and correspondingly, the video processing chip U1 has two, three, four, or more built-in storage units. For example, the switching circuit is configured with four video input modules 10, and the video processing chip U1 configures a storage unit for each video input module 10.

[0044] In an optional embodiment of this application, reference is made to Figure 1The switching circuit also includes a main control module 40, a multi-channel USB input module 50, a first USB switching processing module 60, a multi-channel first USB expansion module 70, a KVM control module 80, and a multi-channel first USB output module 90. The multi-channel USB input module 50 is configured one-to-one with the multi-channel video input module 10 and connected to the first USB switching processing module 60 to receive and transmit USB signals from the corresponding signal source device. The multi-channel first USB expansion module 70 is configured one-to-one with the multi-channel USB input module 50. The KVM control module 80 is connected to the multi-channel first USB output module 90 and the multi-channel first USB expansion module 70 respectively. The main control module 40 is connected to the video processing chip U1 and the first USB switching processing module 60 to control the switching state of the video processing chip U1 and the first USB switching processing module 60.

[0045] Specifically, the main control module 40 can control the switching state of the video processing chip U1 and the first USB switching processing module 60. Since the USB input module 50 corresponds to the video input module 10 (i.e., connected to the same signal source device), the video input module 10 can receive the video signal from the signal source device, and the USB input module 50 can receive the USB signal from the same signal source device. The first USB switching processing module 60 receives USB signals from multiple USB input modules and, according to the instructions of the main control module 40, selects one or more USB signals for output, thus realizing the USB signal switching function. Multiple first USB expansion modules 70 correspond one-to-one with multiple USB input modules, used to expand the interface of each USB input module, allowing each USB input module to connect to more devices through more first USB output modules 90. The KVM control module 80 is used to control multiple signal source devices, that is, to detect and control the USB signals input by the multi-channel USB input module 50. When multiple USB signals are switched at any time, the KVM control module 80 can detect and control multiple USB signals in real time. The mouse and keyboard connected to the KVM control module 80 through the first USB output module 90 will be maintained in real time, and can freely switch between the screens of different signal sources. Therefore, there will be no mouse drift or operation lag when switching signal sources. It supports keyboard hotkey switching, and the HDMI output status can be controlled in real time with hotkeys. It also supports hotkey wake-up after sleep.

[0046] The USB input module 50 mainly transmits USB 3.0 signals to the first USB switching processing module 60 and USB 2.0 signals to the first USB expansion module 70.

[0047] Optionally, the main control module 40 can be implemented using existing chips and their peripheral circuits, such as the GD32F303RCT6 chip and its peripheral circuits. The first USB switching processing module 60 can be implemented using existing chips and their peripheral circuits, such as the CH484 analog switch chip and its peripheral circuits, to achieve switching between multiple USB signals. The first USB expansion module 70 can be implemented using existing chips and their peripheral circuits, such as the GL850S chip and its peripheral circuits. The KVM control module 80 can also be implemented using existing chips and their peripheral circuits, such as the CH9374 chip and its peripheral circuits. The first USB output module 90 can be implemented using conventional circuitry, which will not be described in detail here.

[0048] The number of USB input modules 50 corresponds to the number of video input modules 10, and can be two, three, four, or more. The number of first USB expansion modules 70 corresponds to the number of USB input modules 50. The number of first USB output modules 90 can be two, three, or more. For example, the switching circuit is configured with four USB input modules 50, four first USB expansion modules 70, and two first USB output modules 90.

[0049] In an optional embodiment of this application, reference is made to Figure 1 and Figure 4 The USB input module 50 includes a USB interface J1, a common-mode suppression circuit 51, a surge protection circuit 52, and a third electrostatic discharge (ESD) protection circuit 53. The USB interface J1 is used to receive USB signals from external signal source devices. The third ESD protection circuit 53 is located between the USB interface J1 and the common-mode suppression circuit 51. The surge protection circuit 52 is connected to the USB interface J1 and is used to absorb surge current. The output terminal of the common-mode suppression circuit 51 is connected to the video processing chip U1.

[0050] USB interface J1 serves as the physical connection port, directly interfacing with the USB interface J1 of the external signal source device to receive USB data signals from the source device. The third electrostatic discharge (ESD) protection circuit 53 is connected in parallel to the TMDS high-speed signal input from the HDMI port to resist ESD interference and improve the switching circuit and its application's immunity to electromagnetic field effects caused by ESD. The common-mode rejection circuit 51 filters common-mode interference in signal transmission, ensuring normal transmission of valid signals. The surge protection circuit 52 absorbs surge current, protecting the circuit from sudden high-current impacts. Therefore, by setting up the common-mode rejection circuit 51, surge protection circuit 52, and third ESD protection circuit 53, the downstream circuits can be protected from different dimensions. This improves the stability of USB signal transmission, reduces transmission errors caused by interference, resists external electrical shocks, and extends the lifespan of the interface and back-end circuits. It is particularly suitable for use in scenarios with frequent plugging and unplugging of multiple devices and complex electromagnetic environments (such as conference rooms and monitoring centers).

[0051] Optional, the circuit schematic of USB interface J1 is as follows: Figure 10 As shown. The circuit diagram of the third electrostatic protection circuit 53 is as follows. Figure 11 As shown. The circuit diagram of surge protection circuit 52 is as follows. Figure 12 As shown. The circuit schematic of the common-mode rejection circuit 51 is as follows. Figure 13 As shown.

[0052] In an optional embodiment of this application, reference is made to Figure 1 The switching circuit further includes a second USB expansion module 110, a second USB switching processing module 120, and a multi-channel second USB output module 130. The input terminal of the second USB expansion module 110 is connected to the first USB switching processing module 60 and the second USB switching processing module 120, and the output terminal is connected to the multi-channel second USB output module 130. The second USB switching processing module 120 is also connected to the multi-channel first USB expansion module 70 and the main control module 40.

[0053] The second USB expansion module 110 is used to expand a single-input USB signal into multiple outputs. The multi-channel second USB output module 130 serves as the physical output port for the expanded USB signal, providing multiple USB interfaces J1 that can be directly connected to external devices. Each second USB output module 130 can independently transmit the expanded USB signal, allowing connection to various devices and improving circuit scalability. All expanded output signals originate from the same target signal source, ensuring that multiple devices access the same USB resource, avoiding signal confusion. This is suitable for scenarios requiring simultaneous connection of multiple USB peripherals (such as conference rooms, office desktops, etc.), reducing device plugging and unplugging frequency and improving operational efficiency. The second USB switching processing module 120 mainly switches and selects the USB 2.0 signals output from the multi-channel first USB expansion module 70 before transmitting them to the second USB expansion module 110. The main control module 40 is also used to control the switching state of the second USB switching processing module 120.

[0054] Optionally, the second USB expansion module 110 may employ an expansion chip and its peripheral circuitry, such as a GL3510 chip and its peripheral circuitry, to process signals switched from the first USB switching processing module 60 and the second USB switching processing module 120. The second USB switching processing module 120 may employ existing chips and its peripheral circuitry, such as an analog switch chip CH444G and its peripheral circuitry, to switch signals output from multiple second USB expansion modules 110.

[0055] The second USB output module 130 can be configured in two, three, or more ways. For example, the switching circuit configures two second USB output modules 130.

[0056] In an optional embodiment of this application, reference is made to Figure 1 and Figure 2 The video input module 10 includes an HDMI input interface P1, a first DDC processing circuit 11, an HPD output level conversion circuit 12, and a first electrostatic discharge (ESD) protection circuit 13. The first DDC processing circuit 11 and the HPD output level conversion circuit 12 are both disposed between the HDMI input interface P1 and the video processing chip U1. The first DDC processing circuit 11 is used to communicate with an external signal source device through the HDMI input interface P1. The HPD output level conversion circuit 12 is used to convert the first level signal output by the video processing chip U1 into a second level signal and output it through the HDMI input interface P1. The HDMI input interface P1 is also connected to the video processing chip U1 to transmit the received video signal to the video processing chip U1. The first ESD protection circuit 13 is disposed between the HDMI input interface P1 and the video processing chip U1 to absorb electrostatic current.

[0057] The HDMI input interface P1 serves as the entry point for the video input module 10, directly connecting to the HDMI output of external signal source devices (such as computers, set-top boxes, cameras, etc.). It is responsible for receiving video signals (including image and audio data) output from external devices and also acts as a physical channel for communication between devices. The first DDC processing circuit 11 communicates bidirectionally with the external signal source device through the HDMI input interface P1, sending the extended display recognition data pre-stored in the video processing chip U1 to the signal source device. The HPD output level conversion circuit 12 converts the first-level signal output by the video processing chip U1 into a second-level signal, enabling the signal source device to recognize the second-level signal. This ensures the compatibility of the connection detection signal between the video processing chip U1 and the external signal source device, improving the compatibility of the switching circuit and its applied products with various signal source devices. The first electrostatic discharge (ESD) protection circuit 13 absorbs surge current, limiting the voltage entering the video processing chip U1 within a safe range, preventing chip breakdown, and protecting the downstream circuitry from ESD damage.

[0058] Optional, the circuit schematic of HDMI input interface P1 is as follows: Figure 5 As shown. The circuit diagram of the first electrostatic protection circuit 13 is as follows. Figure 6 As shown. The circuit schematic of the first DDC processing circuit 11 is as follows. Figure 7 As shown.

[0059] In an optional embodiment of this application, reference is made to Figure 2 and Figure 8 The HPD output level conversion circuit 12 includes a PNP transistor Q1, an NPN transistor Q2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The first resistor R1 is connected in series between the collector of the PNP transistor Q1 and the HDMI input interface P1. One end of the second resistor R2 is connected to the HDMI input interface P1, and the other end is grounded. The third resistor R3 is connected in series between the emitter of the PNP transistor Q1 and the collector of the NPN transistor Q2. The fourth resistor R4 is connected in series between the base of the PNP transistor Q1 and the collector of the NPN transistor Q2. One end of the fifth resistor R5 is connected to the base of the NPN transistor Q2, and the other end is used to receive the drive signal. The emitter of the PNP transistor Q1 is also connected to the video processing chip U1.

[0060] By configuring a level conversion circuit consisting of PNP transistor Q1, NPN transistor Q2, first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, and fifth resistor R5, the first level signal output by the video processing chip U1, such as 3.3V, can be converted into a 5V level signal. This allows the signal source device to recognize the 5V level signal, achieving reliable level conversion and ensuring the stable operation of the HDMI interface's hot-plug detection function. This is a crucial step in establishing communication between the video input module 10 and external devices.

[0061] In an optional embodiment of this application, reference is made to Figure 1 and Figure 3 The video output module 30 includes an HDMI output interface P2, a second DDC processing circuit 31, an HPD input level conversion circuit 32, and a second electrostatic discharge (ESD) protection circuit 33. The HDMI output interface P2 is connected to the video processing chip U1. The second ESD protection circuit 33 and the HPD input level conversion circuit 32 are both located between the HDMI output interface P2 and the video processing chip U1. The second DDC processing circuit 31 is used to communicate with an external display device through the HDMI output interface P2. The HPD input level conversion circuit 32 is used to convert the third-level signal output by the video processing chip U1 into a fourth-level signal and output it through the HDMI output interface P2. The second ESD protection circuit 33 is used to absorb electrostatic current.

[0062] The HDMI output interface P2 serves as the output of the video output module 30, connecting to the HDMI input of an external display device (such as a monitor, projector, or TV). It transmits the video signal processed by the video processing chip U1 to the display device and also acts as the physical channel for communication with the display device. The second DDC processing circuit 31 communicates bidirectionally with the external display device through the HDMI output interface P2 to obtain the display device's capability information. It reads the EDID data built into the display device (such as supported resolution, refresh rate, and color gamut) and feeds this information back to the video processing chip U1, helping the chip select a matching preset resolution template to ensure that the output video signal format is compatible with the display device. The HPD input level conversion circuit 32 processes the HPD (hot-plug detection) signal from the display device to achieve level adaptation, allowing the video processing chip U1 to correctly identify the connection status of the display device. The second electrostatic discharge (ESD) protection circuit 33 absorbs ESD current, protecting the video processing chip U1 and the output link from ESD damage.

[0063] The second DDC processing circuit 31 can adopt a similar circuit structure to the first DDC processing circuit 11, and will not be described in detail here. The HPD input level conversion circuit 32 can adopt a similar circuit structure to the HPD output level conversion circuit 12, and will not be described in detail here. The second electrostatic protection circuit 33 can adopt a similar circuit structure to the first electrostatic protection circuit 13, and will not be described in detail here.

[0064] Further reference Figure 3 The video output module 30 also includes a current limiting protection circuit 34, which is located between the video processing chip U1 and the HDMI output interface P2. The current limiting protection circuit 34 is used to limit the current output through the HDMI output interface P2.

[0065] The current limiting protection circuit 34 is used to limit the maximum current through the HDMI output interface to prevent excessive current from damaging circuit components due to abnormal conditions (such as interface short circuit, external display device failure, cable aging, etc.), and to avoid damage to the HDMI input circuit of the display device due to overcurrent at the output end. It is especially suitable for multi-device connection scenarios (such as conference room projectors, large screen monitors and other valuable equipment).

[0066] In an optional embodiment of this application, reference is made to Figure 3 and Figure 9 The current limiting protection circuit 34 includes a power switch chip U2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and a capacitor C1. The sixth resistor R6 is connected in series between the video processing chip U1 and the driving terminal of the power switch chip U2. One end of the seventh resistor R7 is connected to the power supply, and the other end is connected to the driving terminal of the power switch chip U2. The eighth resistor R8 is connected in series between the driving terminal of the power switch chip U2 and the ground terminal. The ninth resistor R9 is connected in series between the fault indication terminals of the power switch chip U2. The tenth resistor R10 is connected in parallel with the capacitor C1. The first parallel node is connected to the output terminal of the power switch chip U2 and the HDMI output interface P2.

[0067] The current limiting protection circuit 34, composed of power switch chip U2, sixth resistor R6, seventh resistor R7, eighth resistor R8, ninth resistor R9, tenth resistor R10 and capacitor C1, achieves precise control of HDMI output current, ensuring the normal power supply needs of external display devices and quickly cutting off risks in case of abnormality.

[0068] Optionally, the power switch chip U2 can be a chip of model SY6280AAAC. Together with the external sixth resistor R6, seventh resistor R7, eighth resistor R8, ninth resistor R9, tenth resistor R10 and capacitor C1, a current threshold can be set to achieve current protection and prevent overcurrent and short circuit.

[0069] This utility model embodiment also provides a KVM switch, which includes the switching circuit described above. This KVM switch has the same structure and beneficial effects as the switching circuit in the foregoing embodiments. The structure and beneficial effects of the switching circuit have been described in detail in the foregoing embodiments and will not be repeated here.

[0070] It should be understood that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the appended claims of this utility model.

Claims

1. A switching circuit, characterized by, It includes a multi-channel video input module, a video processing module, and a video output module, among which, The multi-channel video input module is used to receive multiple video signals; The video processing module includes a video processing chip. The input end of the video processing chip is connected to multiple video input modules to receive multiple video signals, and the output end is connected to the video output module. The video processing chip has multiple storage units corresponding to the multiple video input modules. Each storage unit is pre-loaded with the same preset extended display recognition data and multiple preset resolution templates. The video processing chip is used to receive multiple video signals that match the preset extended display recognition data, and to process the video signals according to the resolution of the display device connected to the video output module by calling the preset resolution templates, and then output the processed video signals through the video output module.

2. The switching circuit according to claim 1, characterized in that, The switching circuit further includes a main control module, a multi-channel USB input module, a first USB switching processing module, a multi-channel first USB expansion module, a KVM control module, and a multi-channel first USB output module. The multiple USB input modules are configured one-to-one with the multiple video input modules and connected to the first USB switching processing module to receive and transmit USB signals from the corresponding signal source devices. The multiple first USB expansion modules are configured one-to-one with the multiple USB input modules. The KVM control module is connected to the multiple first USB output modules and the multiple first USB expansion modules respectively. The main control module is connected to the video processing chip and the first USB switching processing module to control the switching state of the video processing chip and the first USB switching processing module.

3. The switching circuit according to claim 2, characterized in that, The switching circuit further includes a second USB expansion module, a second USB switching processing module, and a multi-channel second USB output module. The input terminal of the second USB expansion module is connected to the first USB switching processing module, and the output terminal is connected to the multi-channel second USB output module. The second USB switching processing module is also connected to the multi-channel first USB expansion module.

4. The switching circuit according to claim 1, characterized in that, The video input module includes an HDMI input interface, a first DDC processing circuit, an HPD output level conversion circuit, and a first electrostatic discharge (ESD) protection circuit. Both the first DDC processing circuit and the HPD output level conversion circuit are disposed between the HDMI input interface and the video processing chip. The first DDC processing circuit is used to communicate with an external signal source device through the HDMI input interface. The HPD output level conversion circuit is used to convert the first level signal output by the video processing chip into a second level signal and output it through the HDMI input interface. The HDMI input interface is also connected to the video processing chip to transmit the received video signal to the video processing chip. The first ESD protection circuit is disposed between the HDMI input interface and the video processing chip to absorb electrostatic current.

5. The switching circuit according to claim 4, characterized in that, The HPD output level conversion circuit includes a PNP transistor, an NPN transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The first resistor is connected in series between the collector of the PNP transistor and the HDMI input interface. One end of the second resistor is connected to the HDMI input interface, and the other end is grounded. The third resistor is connected in series between the emitter of the PNP transistor and the collector of the NPN transistor. The fourth resistor is connected in series between the base of the PNP transistor and the collector of the NPN transistor. One end of the fifth resistor is connected to the base of the NPN transistor, and the other end is used to receive the drive signal. The emitter of the PNP transistor is also connected to the video processing chip.

6. The switching circuit according to claim 1, characterized in that, The video output module includes an HDMI output interface, a second DDC processing circuit, an HPD input level conversion circuit, and a second electrostatic discharge (ESD) protection circuit. The HDMI output interface is connected to the video processing chip. The second ESD protection circuit and the HPD input level conversion circuit are both disposed between the HDMI output interface and the video processing chip. The second DDC processing circuit is used to communicate with an external display device through the HDMI output interface. The HPD input level conversion circuit is used to convert the third-level signal output by the video processing chip into a fourth-level signal and output it through the HDMI output interface. The second ESD protection circuit is used to absorb electrostatic current.

7. The switching circuit according to claim 6, characterized in that, The video output module also includes a current limiting protection circuit, which is disposed between the video processing chip and the HDMI output interface. The current limiting protection circuit is used to limit the current output through the HDMI output interface.

8. The switching circuit according to claim 7, characterized in that, The current limiting protection circuit includes a power switch chip, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a capacitor. The sixth resistor is connected in series between the video processing chip and the driving terminal of the power switch chip. One end of the seventh resistor is connected to the power supply, and the other end is connected to the driving terminal of the power switch chip. The eighth resistor is connected in series between the driving terminal of the power switch chip and the ground terminal. The ninth resistor is connected in series between the fault indication terminals of the power switch chip. The tenth resistor is connected in parallel with the capacitor. The first parallel node is connected to the output terminal of the power switch chip and the HDMI output interface.

9. The switching circuit according to claim 2, characterized in that, The USB input module includes a USB interface, a common-mode suppression circuit, a surge protection circuit, and a third electrostatic discharge (ESD) protection circuit. The USB interface is used to receive USB signals from external signal source devices. The third ESD protection circuit is located between the USB interface and the common-mode suppression circuit. The surge protection circuit is connected to the USB interface and is used to absorb surge current. The output terminal of the common-mode suppression circuit is connected to the video processing chip.

10. A KVM switch, characterized in that, Includes the switching circuit as described in any one of claims 1-9.

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