Display control circuit of airborne display

Abstract

The invention provides a display control circuit of an airborne display, and relates to the technical field of display, the display control circuit comprises a logic device and a watchdog, the logic device sends a dog feeding signal to the watchdog regularly, and the watchdog is used for sending a reset signal to the logic device; the RC oscillating circuit is used for providing a reference sine wave clock signal, and the Schmitt trigger is used for generating a PWM (Pulse Width Modulation) signal; the first input end of the switch is used for receiving a PWM signal output by the trigger, the second input end of the switch is used for receiving a PWM signal output by the logic device, the third input end of the switch is used for receiving a PWM switching signal output by the watchdog, and the output end of the switch is connected with the LED driver so as to drive the LED driver according to the switching signal output by the watchdog. And the connection channels of the switch are switched, so that the normal operation of the LED driver is ensured. According to the method, the phenomena of black screen, splash screen and the like of the airborne display can be avoided, a clear prompt is provided when a fault occurs, and normal reading of messages is ensured.

Description

Technical Field

[0001] The present invention relates to the field of display technology, and in particular to a display control circuit of an airborne display. Background Art

[0002] With the development of aviation technology, more and more information needs to be carried by onboard instruments. The mechanical instruments of the past are gradually replaced by electronic integrated display instruments. Currently, most of the electronic integrated display instruments on board are liquid crystal instruments (LCD). Due to the special application scenarios of onboard instruments, there are extremely high requirements for their availability and safety, which are as follows: try not to have black screen flashing and other phenomena that affect the pilot's reading of information during operation; there should be clear prompts when a fault occurs to prevent the pilot from reading the wrong information.

[0003] In the context of aviation applications, the failure probability of many electronic devices will be greatly increased, especially for complex devices. However, the failure probability requirements that affect safety are more stringent than other applications, so it is often necessary to add some redundancy strategies in the design to prevent the onboard display from black screen flashing, and to have clear prompts when a failure occurs to ensure that the message can be read normally. Summary of the invention

[0004] In view of this, an embodiment of the present application provides an airborne display control circuit, which implements a redundant design for backlight control so that the backlight always works when a logic device fails. At the same time, in conjunction with the BIST screen of the TCON chip, a warning screen can be output when a video link is abnormal, so as to achieve the purpose of not having a black screen on the airborne display.

[0005] The embodiment of the present application provides the following technical solution: an onboard display control circuit, comprising:

[0006] A display main circuit, wherein the display main circuit includes a logic device and a watchdog, wherein the logic device is connected to an input end of the watchdog and is used to periodically send a dog feeding signal to the watchdog, and a first output end of the watchdog is connected to an RST end of the logic device and is used to send a reset signal to the logic device when the dog feeding signal is not received within a set time;

[0007] A display standby circuit, the display standby circuit comprising an RC oscillator circuit and a Schmitt trigger, the output end of the RC oscillator circuit is connected to the input end of the Schmitt trigger, the RC oscillator circuit is used to provide a low-frequency reference sinusoidal clock signal, and the Schmitt trigger is used to generate a PWM signal with an adjustable duty cycle according to the reference sinusoidal clock signal;

[0008] It also includes a two-choice switch and an LCD liquid crystal display, wherein the first input port of the two-choice switch is connected to the output end of the Schmitt trigger, for receiving the PWM signal output by the Schmitt trigger, the second input port of the two-choice switch is connected to the PWM signal output end of the logic device, for receiving the PWM signal output by the logic device, the third input port of the two-choice switch is connected to the second output end of the watchdog, for receiving the PWM channel switching signal output by the watchdog, and the output port of the two-choice switch is connected to the LED driver in the LCD liquid crystal display, so as to switch the switch between the display main circuit and the display standby circuit according to the PWM channel switching signal output by the watchdog, so as to ensure the normal operation of the LED driver.

[0009] According to an embodiment of the present application, a codec is further included, wherein an output end of the codec is connected to a TCON chip in the LCD liquid crystal display, and is used to convert an input video signal and then output it to the TCON chip.

[0010] According to an embodiment of the present application, a BIST circuit is provided in the TCON chip so as to output a warning through a BIST screen display when an abnormality occurs in the video link.

[0011] According to an embodiment of the present application, when the circuit is in a normal state, the two-select-one switch connects to the display main circuit by default. When the circuit is in an abnormal state, the dog feeding signal is lost, a reset signal is sent to the logic device through the watchdog, and a PWM channel switching signal is sent to the two-select-one switch at the same time, so as to connect the display backup circuit through the two-select-one switch.

[0012] According to an embodiment of the present application, the RC oscillation circuit is used to provide a sinusoidal wave clock signal lower than 100KHz.

[0013] According to an embodiment of the present application, the logic device is an MCU.

[0014] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0015] The display control method for an airborne display described in an embodiment of the present invention has the advantage that the circuit of the redundant design part uses simple electronic devices, which can adapt to more complex operating environments and has higher reliability compared to complex electronic devices.

[0016] The display control method for an airborne display described in an embodiment of the present invention has the advantage of adopting a partial redundant design. In a relatively complex airborne operating environment, it can meet the requirement of not having a black screen when complex electronic hardware fails, and more simply meet the availability and safety of airborne instruments.

[0017] The display control method for an airborne display described in the embodiment of the present invention has the advantage that the two types of LED drive controls are independent of each other and do not affect the control in a normal working state.

[0018] The display control method for an airborne display described in an embodiment of the present invention has the advantage that the preset PWM duty cycle controlled by simple electronic hardware is adjustable, and dimming when a logic device fails can be fully realized in conjunction with an external knob or the like.

[0019] The airborne display control method described in the embodiment of the present invention has the advantage that different failure states can clearly prompt the pilot, making it easier for the pilot to judge the state and for maintenance personnel to troubleshoot. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a schematic diagram of the design structure of the airborne display display control method according to an embodiment of the present invention;

[0022] Figure 2 It is a schematic diagram of PWM signals in the display control method of an airborne display according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0025] like Figure 1 As shown, an embodiment of the present invention provides an onboard display control circuit, including:

[0026] A display main circuit, wherein the display main circuit includes a logic device and a watchdog, wherein the logic device is connected to an input end of the watchdog and is used to periodically send a dog feeding signal to the watchdog, and a first output end of the watchdog is connected to an RST end of the logic device and is used to send a reset signal to the logic device when the dog feeding signal is not received within a set time;

[0027] A display standby circuit, the display standby circuit comprising an RC oscillator circuit and a Schmitt trigger, the output end of the RC oscillator circuit is connected to the input end of the Schmitt trigger, the RC oscillator circuit is used to provide a low-frequency reference sinusoidal clock signal, and the Schmitt trigger is used to generate a PWM signal with an adjustable duty cycle according to the reference sinusoidal clock signal;

[0028] It also includes a two-choice switch and an LCD liquid crystal display, wherein the first input port of the two-choice switch is connected to the output end of the Schmitt trigger, for receiving the PWM signal output by the Schmitt trigger, the second input port of the two-choice switch is connected to the PWM signal output end of the logic device, for receiving the PWM signal output by the logic device, the third input port of the two-choice switch is connected to the second output end of the watchdog, for receiving the PWM channel switching signal output by the watchdog, and the output port of the two-choice switch is connected to the LED driver in the LCD liquid crystal display, so as to switch the switch between the display main circuit and the display standby circuit according to the PWM channel switching signal output by the watchdog, so as to ensure the normal operation of the LED driver.

[0029] The necessary conditions for the LCD instrument display are backlight and video signals. The embodiment of the present invention performs redundant design on the backlight control signal PWM input, and the RC oscillator circuit provides a low-frequency reference sine wave clock. The LED driver does not require high PWM input accuracy, and the RC oscillator circuit is fully competent; then the Schmitt trigger generates PWM with adjustable duty cycle. Under normal conditions, the MCU provides PWM to control the LED driver. When the MCU fails, the watchdog feeding signal is lost, and a reset signal is generated. On the one hand, it is used to reset the MCU, and at the same time, the PWM channel is switched to the PWM channel generated by simple electronic hardware to ensure that the LED driver is still working normally.

[0030] In an implementation manner of the embodiment of the present invention, a codec is further included, wherein the output end of the codec is connected to the TCON chip in the LCD liquid crystal display, and is used to convert the input video signal and then output it to the TCON chip.

[0031] In order to enable the LCD instrument display product to still provide information prompts or warnings when the logic device fails and meet the requirements of high-security level equipment, in one implementation of the embodiment of the present invention, a BIST circuit is set in the TCON chip to output a warning through the BIST screen display when an abnormality occurs in the video link.

[0032] In an embodiment of the present invention, when the circuit is in a normal state, the two-select-one switch connects the display main circuit by default. When the circuit is in an abnormal state, the dog feeding signal is lost, a reset signal is sent to the logic device through the watchdog, and a PWM channel switching signal is sent to the two-select-one switch at the same time, so as to connect the display standby circuit through the two-select-one switch.

[0033] In the embodiment of the present invention, the RC oscillator circuit is used to provide an adjustable low-frequency reference sinusoidal clock signal, which is generally a sinusoidal clock signal lower than 100 KHz.

[0034] A specific implementation of the present invention will be described in detail below. The circuit design of this embodiment specifically includes:

[0035] (1) Select an RC oscillator circuit that produces a stable 200Hz sinusoidal clock signal.

[0036] (2) Select a Schmitt trigger with adjustable threshold voltage, set different positive threshold voltages and negative threshold voltages according to the required default brightness, and generate a PWM signal with a corresponding duty cycle, such as Figure 2 shown.

[0037] (3) Normal state: The logic device (MCU for example) outputs PWM, the two-choice switch selects this path by default, the backlight driver EN (enable) is pulled high by default, the MCU controls the LED driver to work normally through EN and PWM, and the backlight displays normally. The video link is normal, and the picture is displayed normally.

[0038] (4) Normal state enters abnormal state: the logic device (taking MCU as an example) fails, the dog feeding signal is lost, the watchdog pulls down the reset signal, tries to restart the MCU, and controls the selection of the two-choice switch at the same time. The PWM channel generated by simple electronic hardware, the backlight driver enable is pulled high by default, and the LED driver works with a preset PWM duty cycle. If the video link is normal at this time, it can maintain normal display and will not affect the pilot's reading of information; if the video link also fails at this time, it will cooperate with the BIST screen of the TCON chip to display a blue screen and other logical screens to warn the pilot.

[0039] (5) Abnormal state restores to normal state: The logic device (taking MCU as an example) restores normal operation through reset, the dog feeding signal is output normally, the watchdog is reset, and the reset signal is restored. At the same time, the two-choice switch is controlled to restore the MCU output PWM path, and the MCU can control the LED driver to work normally.

[0040] The non-black screen design of the LCD instrument is an important requirement for aviation instruments. The embodiment of the present invention proposes a low-cost design solution to improve the usability and safety of the product, meeting the requirements of the display head with a higher safety level.

[0041] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An onboard display control circuit, characterized in that: include: A display main circuit, wherein the display main circuit includes a logic device and a watchdog, wherein the logic device is connected to an input end of the watchdog and is used to periodically send a dog feeding signal to the watchdog, and a first output end of the watchdog is connected to an RST end of the logic device and is used to send a reset signal to the logic device when the dog feeding signal is not received within a set time; A display standby circuit, the display standby circuit comprising an RC oscillator circuit and a Schmitt trigger, the output end of the RC oscillator circuit is connected to the input end of the Schmitt trigger, the RC oscillator circuit is used to provide a low-frequency reference sinusoidal clock signal, and the Schmitt trigger is used to generate a PWM signal with an adjustable duty cycle according to the reference sinusoidal clock signal; It also includes a two-choice switch and an LCD liquid crystal display, wherein the first input port of the two-choice switch is connected to the output end of the Schmitt trigger, for receiving the PWM signal output by the Schmitt trigger, the second input port of the two-choice switch is connected to the PWM signal output end of the logic device, for receiving the PWM signal output by the logic device, the third input port of the two-choice switch is connected to the second output end of the watchdog, for receiving the PWM channel switching signal output by the watchdog, and the output port of the two-choice switch is connected to the LED driver in the LCD liquid crystal display, so as to switch the switch between the display main circuit and the display standby circuit according to the PWM channel switching signal output by the watchdog, so as to ensure the normal operation of the LED driver.

2. The onboard display control circuit according to claim 1, characterized in that: It also includes a codec, the output end of which is connected to the TCON chip in the LCD liquid crystal display, and is used to convert the input video signal and then output it to the TCON chip.

3. The onboard display control circuit according to claim 2, characterized in that: The TCON chip is provided with a BIST circuit so as to output a warning through a BIST screen display when an abnormality occurs in the video link.

4. The onboard display control circuit according to claim 1, characterized in that: When the circuit is in a normal state, the two-select-one switch connects the display main circuit by default. When the circuit is in an abnormal state, the dog feeding signal is lost, a reset signal is sent to the logic device through the watchdog, and a PWM channel switching signal is sent to the two-select-one switch at the same time, so as to connect the display standby circuit through the two-select-one switch.

5. The onboard display control circuit according to claim 1, characterized in that: The RC oscillation circuit is used to provide a sine wave clock signal lower than 100 KHz.

6. The onboard display control circuit according to claim 1, characterized in that: The logic device is an MCU.

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