Hot plug circuit for analog display interface

Abstract

The utility model relates to the field of domestic display chip, concretely is hot plug circuit of analog display interface. Including pull -up resistance, display in -place detection circuit and switch, with the short -circuit end of the connector between display chip and display to ground as detection pin, detection pin one way passes through pull -up resistance and connects to high voltage, and detection pin another way connects to the input end of display in -place detection circuit, and the output end of display in -place detection circuit is connected switch, and the switch is connected on the signal passage between display chip and display card equipment. The utility model can solve the problem that part domestic analog display interface chip cannot identify display hot plug action, realizes the real -time update of display information under operating system.

Description

Technical Field

[0001] This utility model relates to the field of domestic display chips, specifically a hot-swappable circuit for an analog display interface. Background Technology

[0002] Currently, some domestically produced analog display interface chips lack the ability to detect monitor insertion and removal. As a result, they can only identify the monitor's presence status and EDID information such as the monitor model when it is first powered on. When the analog display chip is powered on, the chip cannot detect the change when the analog interface monitor is inserted, removed, or replaced. This causes the system's monitor identification to fail to update in a timely manner. In particular, if the analog display chip detects the analog interface monitor during power-on detection and removes the monitor after detection, the system will consider the monitor to be in place. This can lead to display abnormalities when the operating system performs display copying, expansion, or other operations, affecting usability.

[0003] For example, the domestically produced HDMI to VGA display chip MS9292, its VGA analog display interface lacks dedicated hot-plug signals such as HPD, and it only reads the monitor status once after power-on. When MS9292 is powered on and the monitor is not in use, MS9292 cannot obtain EDID information such as the monitor model through the EDID path. MS9292 will report its internal default EDID information to the operating system, at which point the operating system will recognize a monitor with fixed EDID information. When MS9292 is powered on and the monitor is in use, if MS9292 can obtain EDID information such as the monitor model through the EDID path, MS9292 will report the read monitor EDID information to the operating system, at which point the operating system will recognize a monitor with fixed EDID information. Therefore, regardless of whether the monitor is in use when MS9292 is powered on, the operating system can recognize a monitor with fixed EDID information, and this information does not change with the plugging or unplugging of the monitor. Utility Model Content

[0004] To address the shortcomings of existing technologies, this utility model provides a hot-swappable circuit for an analog display interface, which can solve the problem that some domestically produced analog display interface chips cannot recognize the hot-swappable action of the display, and realize real-time updates of display information under the operating system.

[0005] To solve the aforementioned technical problem, the present invention adopts the following technical solution: a hot-swappable circuit for an analog display interface, comprising a pull-up resistor, a display presence detection circuit, and a switch. The ground-short-circuited end of the connector between the display chip and the display is used as a detection pin. One path of the detection pin is connected to a high voltage through the pull-up resistor, and the other path of the detection pin is connected to the input terminal of the display presence detection circuit. The output terminal of the display presence detection circuit is connected to the switch, and the switch is connected to the signal path between the display chip and the graphics card device.

[0006] Furthermore, the connector between the display chip and the display is a DB15 connector. Pins 4, 9, and 11 of the DB15 connector are shorted to ground and extended outwards as detection pins.

[0007] Furthermore, the display presence detection circuit is an AND gate chip 74HC08. The two inputs of the first AND gate in the AND gate chip 74HC08 are connected to pin4 and pin9. The two inputs of the second AND gate in the AND gate chip 74HC08 are connected to the output of the first AND gate and pin11. The output of the second AND gate in the AND gate chip 74HC08 is the output of the display presence detection circuit.

[0008] Furthermore, two switches are provided: one switch is located on the EDID path between the display chip and the graphics card device, and the other switch is located on the HPD path between the display chip and the graphics card device.

[0009] Furthermore, the switches are implemented based on analog switches, with the EDID path using a dual-channel analog switch and the HPD path using a single-channel analog switch.

[0010] Furthermore, the display chip is the MS9292 HDMI to VGA display chip.

[0011] Furthermore, the high voltage is +5V.

[0012] The beneficial effects of this utility model are as follows: This utility model designs a display presence detection circuit, using the ground-short terminal on the DB15 connector as the detection point for the display's presence status. The display's presence is determined by the change in its voltage level when the display is present and absent. A switch is set up to control the upstream HDMI interface EDID and HPD signal paths, enabling the operating system to update the downstream display status. The control of the signal paths is implemented by the display presence detection circuit. Based on pre-designed control logic, a hot-swapping design for the VGA display is achieved without the user's awareness. Attached Figure Description

[0013] Figure 1 This is the schematic diagram of a hot-swappable circuit. Figure 2 This is a schematic diagram of the hot-swappable circuitry in the entire display system. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0015] Example 1 This embodiment discloses a hot-plug circuit for an analog display sub-interface, such as... Figure 1 , 2As shown, it includes a pull-up resistor, a display presence detection circuit, and a switch. The ground-short-to-ground terminal of the connector between the display chip and the display is used as the detection pin. One path of the detection pin is connected to a high voltage through the pull-up resistor, and the other path of the detection pin is connected to the input terminal of the display presence detection circuit. The output terminal of the display presence detection circuit is connected to the switch, and the switch is connected to the signal path between the display chip and the graphics card device.

[0016] In this embodiment, the display chip is an HDMI to VGA display chip MS9292, and the connector between the display chip and the monitor is a DB15 connector. After testing multiple monitors, it was found that pins 4, 9, and 11 are all shorted to the GND signal. Therefore, pins 4, 9, and 11 of the DB15 connector were selected as the detection pins. In the circuit design, these three pins are pulled up to 5V using pull-up resistors. When the monitor is not in place, the actual voltage level of these three pins is 5V due to the presence of the pull-up resistors. When the monitor is inserted, since these three pins are all shorted to the GND signal, the actual voltage level of these three pins becomes 0V. This achieves the detection of hot-plugging of the VGA monitor.

[0017] In this embodiment, the display presence detection circuit is an AND gate chip 74HC08. Since there are three input signals, two stages of AND operations are required, necessitating the use of two AND gates from the 74HC08 chip. Specifically, the two inputs of the first AND gate in the 74HC08 chip are connected to pins 4 and 9, and the two inputs of the second AND gate are connected to the output of the first AND gate and pin 11. The output of the second AND gate in the 74HC08 chip is the output of the display presence detection circuit. The output of the second stage of the AND gate is the final detection result. The final output is low only when all three inputs are low.

[0018] This embodiment has two switches: one switch is located on the EDID path between the display chip and the graphics card device, and the other switch is located on the HPD path between the display chip and the graphics card device.

[0019] Specifically, the switch is implemented using an analog switch. An analog switch chip is an integrated circuit that uses MOSFET transistors to conduct signals. When a high (or low) level is applied to the control pin (EN), the internal switch closes, and the signal is transmitted from the input to the output. When the control pin level is reversed, the switch opens, and the signal path is isolated by a high-impedance state. For the SCL (clock) and SDA (data) signal lines of EDID, a dual-channel analog switch chip (such as TI's TS3A24157) can be selected. Similarly, the HPD signal can use a single-channel analog switch. The control terminals of these switches can be connected in parallel and uniformly controlled by the signal output from the display presence detection circuit. When the display is detected to be present, the HDMI uplink EDID and HPD paths are opened; when the display is not detected to be present, the HDMI uplink EDID and HPD paths are closed.

[0020] This invention enables hot-swapping of VGA monitors without the user's awareness, thus addressing some shortcomings in the design of domestically produced analog display chips.

[0021] The above description is only the basic principle and preferred embodiment of this utility model. Any improvements and substitutions made by those skilled in the art based on this utility model shall fall within the protection scope of this utility model.

Claims

1. A hot-swappable circuit for an analog display interface, characterized in that: It includes a pull-up resistor, a display presence detection circuit, and a switch. The ground-short end of the connector between the display chip and the display is used as the detection pin. One path of the detection pin is connected to a high voltage through the pull-up resistor, and the other path of the detection pin is connected to the input of the display presence detection circuit. The output of the display presence detection circuit is connected to the switch, and the switch is connected to the signal path between the display chip and the graphics card device.

2. The hot-swappable circuit for the analog display interface according to claim 1, characterized in that: The connector between the display chip and the display is a DB15 connector. Pins 4, 9, and 11 of the DB15 connector are shorted to ground and extended outwards as detection pins.

3. The hot-swappable circuit for the analog display interface according to claim 1, characterized in that: The display presence detection circuit is an AND gate chip 74HC08. The two inputs of the first AND gate in the 74HC08 are connected to pin 4 and pin 9. The two inputs of the second AND gate in the 74HC08 are connected to the output of the first AND gate and pin 11. The output of the second AND gate in the 74HC08 is the output of the display presence detection circuit.

4. The hot-swappable circuit for the analog display interface according to claim 1, characterized in that: It is equipped with two switches: one switch is located on the EDID path between the display chip and the graphics card device, and the other switch is located on the HPD path between the display chip and the graphics card device.

5. The hot-swappable circuit for the analog display interface according to claim 4, characterized in that: The switches are implemented based on analog switches. The EDID path uses a dual-channel analog switch, while the HPD path uses a single-channel analog switch.

6. The hot-swappable circuit for the analog display interface according to claim 1, characterized in that: The display chip is the MS9292 HDMI to VGA display chip.

7. The hot-swappable circuit for the analog display interface according to claim 1, characterized in that: The high voltage is +5V.

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