Method for avoiding power-off ghost shadow of liquid crystal display equipment and liquid crystal display equipment

Abstract

The embodiment of the invention relates to liquid crystal display equipment and a method for avoiding power-off ghosting of the liquid crystal display equipment. The method for avoiding the power-off ghosting of the liquid crystal display equipment comprises the following steps: providing a liquid crystal display panel; in a liquid crystal display microprocessor circuit, a liquid crystal display panel driving circuit is provided, and the liquid crystal display panel driving circuit is provided with a driving memory; when the system is powered on, an under-voltage voltage level is set; and when the power supply voltage of the liquid crystal display microprocessor circuit drops to the under-voltage voltage level, clearing the content in the driving memory.

Description

Technical Field

[0001] The present invention relates to a liquid crystal display technology, and in particular to a method for preventing residual image when a liquid crystal display device is powered off and a liquid crystal display device. Background Art

[0002] Nematic (TN) liquid crystal displays (LCDs), which are known for their low cost and high contrast, are widely used in many application fields. For example, TN LCDs can be used in the instrument panels of motorcycles and motorbikes, such as speedometers, tachometers, and oil pressure gauges. Their low cost and durability make them ideal for these applications. In addition, many portable electronic computers and calculators use TN LCDs. This technology provides clear digital and text displays and performs well in indoor environments. TN LCDs are also commonly used in home air conditioner remote controls. They can display information such as set temperature, fan speed, and mode on a small display and can work well in indoor lighting conditions.

[0003] However, TN LCDs also have some drawbacks, one of the main drawbacks is that they may produce ghosting when the power is off. In particular, when the power is suddenly interrupted or switched, the molecules of TN LCDs cannot immediately return to their original arrangement, resulting in ghosting or residual images on the screen. Summary of the invention

[0004] The present invention provides a method for preventing power-off afterimage of a liquid crystal display device and a liquid crystal display device using the method, which is used to clear the contents of a liquid crystal display driver memory when the voltage of a microprocessor reaches an undervoltage voltage level, thereby preventing power-off afterimage of the liquid crystal display device.

[0005] An embodiment of the present invention provides a method for avoiding image retention when a liquid crystal display device is powered off. The method for avoiding image retention when a liquid crystal display device is powered off includes the following steps: providing a liquid crystal display panel; providing a liquid crystal display panel driving circuit having a driving memory; setting an undervoltage voltage level when the system is powered on; and clearing the contents of the driving memory when the power supply voltage of the microprocessor drops to the undervoltage voltage level.

[0006] According to the method for avoiding power-off afterimage of a liquid crystal display device described in a preferred embodiment of the present invention, the liquid crystal display panel is a nematic (TN) liquid crystal display panel. In a preferred embodiment of the present invention, the drive memory is used to store drive data of a common (COM) drive line and a segment (Segment) drive line. In a preferred embodiment of the present invention, when the system is powered on, after setting an undervoltage voltage level, the following steps are also included: enabling an undervoltage voltage interrupt function, wherein when the power supply voltage of the microprocessor drops to the undervoltage voltage level, the undervoltage voltage interrupt function is triggered, the drive memory is cleared, and the undervoltage voltage interrupt function flag is cleared.

[0007] An embodiment of the present invention provides a liquid crystal display device. The liquid crystal display device includes a liquid crystal display panel and a liquid crystal display microprocessor circuit. The liquid crystal display microprocessor circuit is coupled to the liquid crystal display panel. The liquid crystal display microprocessor circuit includes a power supply voltage detection circuit, a liquid crystal display panel driving circuit and a liquid crystal display microcontroller. The power supply voltage detection circuit receives a power supply voltage and an undervoltage voltage level signal. When the system is powered on, it determines an undervoltage voltage level according to the undervoltage voltage level signal, and determines whether the power supply voltage is lower than the undervoltage voltage level. When the power supply voltage is lower than the undervoltage voltage level, an undervoltage signal is output. The liquid crystal display panel driving circuit has a driving memory for driving the liquid crystal display panel. The liquid crystal display microcontroller is coupled between the power supply voltage detection circuit and the liquid crystal display panel driving circuit to control the liquid crystal display panel driving circuit. When the power supply voltage drops to the undervoltage voltage level, the liquid crystal display microcontroller clears the content in the driving memory according to the undervoltage signal.

[0008] In summary, the embodiments of the present invention set an undervoltage voltage level immediately after the device is started, and continuously detect the voltage of the microprocessor. When the voltage of the microprocessor reaches the undervoltage voltage level, the contents of the LCD driver memory are cleared first, so that the LCD driver stops driving the LCD device. In this way, before shutting down, the LCD device can avoid power failure and afterimage.

[0009] In order to further understand the technology, means and effects of the present invention, reference may be made to the following detailed description and accompanying drawings, so that the purpose, features and concepts of the present invention can be thoroughly and specifically understood. However, the following detailed description and accompanying drawings are only used for reference and explanation of the implementation of the present invention, and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings are provided to enable those with ordinary knowledge in the technical field to which the present invention belongs to further understand the present invention, and are incorporated into and constitute a part of the specification of the present invention. The accompanying drawings illustrate exemplary embodiments of the present invention, and together with the description of the present invention, are used to explain the principles of the present invention.

[0011] Figure 1 FIG. 4 is a system block diagram of a liquid crystal display device according to a preferred embodiment of the present invention.

[0012] Figure 2 A flow chart of a method for preventing image sticking during power-off of a liquid crystal display device according to a preferred embodiment of the present invention is shown.

[0013]

Explanation of symbols

[0014] 10…LCD panel; 11…LCD microprocessor circuit; 111…Power supply voltage detection circuit; 112…LCD panel drive circuit; 113…AND gate; 114…Delay circuit; 115…LCD microcontroller; COM…Common drive signal; SEG…Segment drive signal; VCC…Power supply voltage; BODL…Undervoltage voltage level signal; BOD…Undervoltage signal; LCD_BOD…LCD display undervoltage signal; BD…Protection signal; S201~S206…Process steps of a method for avoiding power-off afterimages in a LCD device according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0015] Reference will now be made in detail to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Where possible, the same component symbols are used in the drawings and the specification to refer to the same or similar components. In addition, the exemplary embodiments are only one of the implementation methods of the design concept of the present invention, and the following examples are not intended to limit the present invention.

[0016] Figure 1 FIG. 1 is a system block diagram of a liquid crystal display device according to a preferred embodiment of the present invention. Figure 1, this liquid crystal display device includes a liquid crystal display panel 10 and a liquid crystal display microprocessor circuit 11. The liquid crystal display microprocessor circuit 11 is coupled to the liquid crystal display panel 10. This liquid crystal display microprocessor circuit 11 includes a power supply voltage detection circuit 111, a liquid crystal display panel driving circuit 112, an AND gate 113, a delay circuit 114 and a liquid crystal display microcontroller 115. The liquid crystal display panel driving circuit 112 has a driving memory (not shown) inside. In this embodiment, a nematic (TN) liquid crystal display panel is taken as an example, so this liquid crystal display microprocessor circuit 11 outputs a common driving signal COM and a segment driving signal SEG to drive the above-mentioned liquid crystal display panel 10. Therefore, the driving memory inside the liquid crystal display panel driving circuit 112 is used to store the driving data of the common (COM) driving line and the segment (Segment) driving line.

[0017] In this embodiment, the power supply voltage detection circuit 111 receives the power supply voltage VCC and the brown-out voltage level signal BODL. Generally speaking, the brown-out voltage level signal BODL is sent to the power supply voltage detection circuit 111 when the system is powered on, and is used to set a brown-out voltage level in the power supply voltage detection circuit 111. For example, assuming that the power supply voltage VDD is a battery voltage, which is about 3.2V when fully charged and about 2.6 to 1.8V when undercharged, the brown-out voltage level signal BODL will set the brown-out voltage level (Brown-out detect level) at 2.5V, for example, after the system is powered on. The power supply voltage detection circuit 111 will determine whether the power supply voltage VCC is lower than the brown-out voltage level 2.5V after the brown-out voltage level is set. When the power supply voltage is lower than the brown-out voltage level 2.5V, an brown-out signal BOD is output and enabled.

[0018] Generally, the undervoltage signal BOD is used to protect the internal register or input / output pins of the LCD display microprocessor circuit 11 from abnormality before the power supply is insufficient. In this embodiment, in addition to the above, when the undervoltage signal BOD is enabled and the LCD display undervoltage signal LCD_BOD is also enabled, it indicates that the power supply voltage VDD reaches an undervoltage voltage level, and at this time, the protection signal BD is activated. When the LCD display microcontroller 115 receives the activated protection signal BD, it will enable an undervoltage voltage interrupt function (BOD interrupt) to notify the LCD display panel driving circuit 112. Since the LCD display panel driving circuit 112 has a driving memory inside, it is used to store the COM and SEG data of driving the LCD display panel 10. When the voltage is insufficient but still operable, these data will still be used to drive the LCD display panel 10. Therefore, in this embodiment, the driving memory inside the LCD display panel driving circuit 112 will be cleared first.

[0019] In addition, this embodiment also includes a delay circuit 114, which delays the activated protection signal BD so that the remaining functional blocks coupled thereto can be turned off with a delay to avoid having too late to clear the driving memory inside the above-mentioned liquid crystal display panel driving circuit 112.

[0020] In the above embodiment, if there is no LCD undervoltage signal LCD_BOD, the AND gate 113 may not be used, and the present invention is not limited thereto. The delay circuit 114 may also be designed according to different requirements and may not be used. The present invention is not limited thereto.

[0021] The above embodiments can be summarized into a method for preventing image sticking when a liquid crystal display device is powered off. Figure 2 A flowchart of a method for preventing image sticking in a liquid crystal display device when power is turned off according to a preferred embodiment of the present invention is shown. Figure 2 The method for preventing residual image when a liquid crystal display device is powered off comprises the following steps:

[0022] Step S201: Start.

[0023] Step S202: providing a liquid crystal display panel.

[0024] Step S203: In a liquid crystal display microprocessor circuit, a liquid crystal display panel driving circuit having a driving memory is provided.

[0025] Step S204: When the system is powered on, an undervoltage voltage level is set.

[0026] Step S205: Determine whether the power supply voltage reaches the undervoltage voltage level. When the power supply voltage of the liquid crystal display microprocessor circuit drops to the undervoltage voltage level, proceed to step S206.

[0027] Step S206: Clear the contents of the driver memory. Figure 1 Embodiment of the invention.

[0028] In summary, the embodiment of the present invention sets an undervoltage voltage level immediately after the device is started, and continuously detects the voltage of the microprocessor. When the voltage of the microprocessor reaches the undervoltage voltage level, the contents of the LCD driver memory are cleared first, so that the LCD driver stops driving the LCD device. In this way, before shutting down, the LCD device can avoid power failure and afterimage.

[0029] It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in view thereof will be suggested to those skilled in the art and are to be included within the spirit and scope of the present application and the scope of the appended claims.

Claims

1. A method for preventing image sticking when a liquid crystal display device is powered off, characterized in that: include: Providing a liquid crystal display panel; In a liquid crystal display microprocessor circuit, a liquid crystal display panel driving circuit is provided, which has a driving memory; When the system is powered on, an undervoltage voltage level is set; as well as When the power supply voltage of the liquid crystal display microprocessor circuit drops to the undervoltage voltage level, the content in the driving memory is cleared.

2. The method for preventing image sticking during power-off of a liquid crystal display device according to claim 1, characterized in that: The liquid crystal display panel is a nematic liquid crystal display panel.

3. The method for preventing image sticking during power-off of a liquid crystal display device according to claim 2, characterized in that: The driving memory is used to store driving data of the common driving lines and the segment driving lines.

4. The method for preventing image sticking during power-off of a liquid crystal display device according to claim 1, characterized in that: When the system is powered on, an undervoltage voltage level is set, including: Enable an undervoltage interrupt function; When the power supply voltage of the microprocessor drops to the undervoltage voltage level, the undervoltage interruption function is triggered, the driving memory is cleared, and the undervoltage interruption function flag is cleared.

5. A liquid crystal display device, characterized in that: include: a liquid crystal display panel; as well as A liquid crystal display microprocessor circuit is coupled to the liquid crystal display panel, wherein the liquid crystal display microprocessor circuit comprises: a power supply voltage detection circuit, receiving a power supply voltage and an undervoltage voltage level signal, and determining an undervoltage voltage level according to the undervoltage voltage level signal when the system is powered on, and determining whether the power supply voltage is lower than the undervoltage voltage level, wherein when the power supply voltage is lower than the undervoltage voltage level, an undervoltage signal is output; a liquid crystal display panel driving circuit having a driving memory for driving the liquid crystal display panel; and a liquid crystal display microcontroller, coupled between the power supply voltage detection circuit and the liquid crystal display panel driving circuit, for controlling the liquid crystal display panel driving circuit, When the power supply voltage drops to the undervoltage voltage level, the liquid crystal display microcontroller clears the content in the driving memory according to the undervoltage signal.

6. The liquid crystal display device according to claim 5, characterized in that: The liquid crystal display microprocessor circuit further comprises: A delay circuit is coupled to the power supply voltage detection circuit to delay the time for sending the undervoltage signal to other functional blocks.

7. The liquid crystal display device according to claim 5, characterized in that: The liquid crystal display panel is a nematic liquid crystal display panel.

8. The liquid crystal display device according to claim 5, characterized in that: The driving memory is used to store driving data of the common driving lines and the segment driving lines.

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