Liquid crystal display device and control method thereof
阅读说明:本技术 液晶显示装置及其控制方法 (Liquid crystal display device and control method thereof ) 是由 西原康友 藤堂英男 大原幸一 半田卓也 道林浩司 于 2019-06-18 设计创作,主要内容包括:本发明提供一种液晶显示装置及其控制方法,所述液晶显示装置具备:显示部、由多个光源构成的背光源、基于显示同步信号以光源间歇地点亮的方式输出PWM信号(LED控制信号)的LED控制电路、以及基于PWM信号控制向光源供给的驱动电流的LED驱动器,在所述液晶显示装置中设置有以PWM信号、驱动电流、以及显示同步信号中的至少一个为监视对象进行监视的监视控制部。监视控制部在检测到监视对象的异常时,控制PWM信号的波形,以使被供给至背光源内的光源的驱动电流为零。(The invention provides a liquid crystal display device and a control method thereof, the liquid crystal display device comprises: the liquid crystal display device includes a display unit, a backlight including a plurality of light sources, an LED control circuit that outputs a PWM signal (LED control signal) so that the light sources are intermittently turned on based on a display synchronization signal, and an LED driver that controls a drive current supplied to the light sources based on the PWM signal. When an abnormality of a monitoring target is detected, a monitoring control unit controls the waveform of a PWM signal so that a drive current supplied to a light source in a backlight is zero.)
1. A liquid crystal display device is characterized by comprising:
a display unit that displays an image;
a light source that irradiates the display unit with light;
a light source control unit that outputs a PWM signal having a constant duty ratio so that the light source is intermittently turned on based on a display synchronization signal;
a light source driving unit that controls a driving current supplied to the light source based on a PWM signal output from the light source control unit; and
and a monitoring control unit that monitors at least one of the PWM signal, the drive current, and the display synchronization signal as a monitoring target, and controls a waveform of the PWM signal so that the drive current supplied to the light source becomes zero when an abnormality of the monitoring target is detected.
2. The liquid crystal display device according to claim 1,
a display driving unit for driving the display unit based on an image signal and the display synchronization signal,
the light source control section is provided in the display drive section.
3. The liquid crystal display device according to claim 2,
the display device includes a host that supplies the image signal and the display synchronization signal to the display driving unit.
4. The liquid crystal display device according to claim 3,
the monitoring control unit is provided in the host.
5. The liquid crystal display device according to claim 4,
the monitoring control unit initializes the display driving unit and the light source driving unit when an abnormality of the monitoring target is detected.
6. The liquid crystal display device according to claim 3,
the monitor control unit is provided in the display driving unit.
7. The liquid crystal display device according to claim 6,
the monitoring control unit initializes the display driving unit, the light source driving unit, and the host computer when detecting an abnormality of the monitoring target.
8. The liquid crystal display device according to claim 3,
the monitoring control unit is provided in the light source driving unit.
9. The liquid crystal display device according to claim 8,
the monitoring control unit initializes the display driving unit, the light source driving unit, and the host computer when detecting an abnormality of the monitoring target.
10. The liquid crystal display device according to claim 2,
the monitoring control unit initializes the display driving unit and the light source driving unit when an abnormality of the monitoring target is detected.
11. The liquid crystal display device according to any one of claims 1 to 10,
the monitoring control unit determines that an abnormality has occurred in the monitoring target when the on period of the PWM signal is longer than a predetermined period.
12. The liquid crystal display device according to any one of claims 1 to 10,
the monitoring control unit determines that an abnormality has occurred in the monitoring target when the driving current is used as the monitoring target and the state where the magnitude of the driving current is equal to or greater than a predetermined magnitude continues for longer than a predetermined period.
13. A method for controlling a liquid crystal display device, the liquid crystal display device comprising:
a display unit that displays an image;
a light source that irradiates the display unit with light;
a light source control unit that outputs a PWM signal having a constant duty ratio so that the light source is intermittently turned on based on a display synchronization signal; and
a light source driving section that controls a driving current supplied to the light source based on a PWM signal output from the light source control section,
the method for controlling a liquid crystal display device is characterized by comprising the following steps:
a monitoring step of monitoring at least one of the PWM signal, the drive current, and the display synchronization signal as a monitoring target; and
and a control step of controlling a waveform of the PWM signal so that a drive current supplied to the light source becomes zero when an abnormality of the monitoring target is detected.
Technical Field
The following disclosure relates to a liquid crystal display device and a control method thereof.
Background
In a liquid crystal display device, color display is performed by additive color mixing of three primary colors. Therefore, in the projection type liquid crystal display device, a backlight capable of irradiating white light including a red component, a green component, and a blue component to the liquid crystal panel is required. In the backlight source, a cold cathode tube called CCFL has been widely used. However, in recent years, from the viewpoints of reduction in power consumption, ease of luminance control, and the like, the use of LEDs (Light Emitting diodes) has been increasing.
In such a liquid crystal display device, in order to suppress occurrence of motion blur (a phenomenon of image blur when displaying a motion image), a driving method (hereinafter, referred to as "pulse backlight driving") of intermittently lighting an LED as a backlight light source is sometimes employed. According to the impulse backlight drive, a black screen is inserted by turning off the LED, and thus generation of a moving image blur is suppressed.
In connection with the present application, the following prior art documents are known. Japanese patent application laid-open No. 2016-129098 discloses a technique for preventing ringing in an LED driving device that performs PWM control of an LED using a boost chopper circuit. In the monograph of international publication No. 2015/041012, a technique for dynamically controlling the luminance of a backlight in accordance with image data is disclosed. Japanese patent application laid-open publication No. 2011-216876 discloses a technique for suppressing flickering of a screen of a liquid crystal display device including an LED driving device that performs PWM control of LEDs.
However, in a liquid crystal display device using the pulse backlight driving, abnormal heat generation of the LED may occur. Abnormal heat generation of the LED may cause deformation and ignition of various sheets (optical sheets and the like) constituting the backlight and the plastic frame, for example. This will be explained below.
In a liquid Crystal display device using the pulse backlight drive, an
Under the above-described premise, the display synchronization signal SY may not be normally input to the
However, when dimming of the LED is performed by PWM control by a configuration not employing pulse backlight driving, the magnitude of the driving current is fixed to a constant magnitude during the period in which the driving current is supplied to the LED. That is, the brightness of the LED is adjusted with the duty ratio of the PWM signal. Here, the magnitude of the drive current is equal to or less than the magnitude of the LED allowable forward current at a duty ratio of 100%. Therefore, even if the duty ratio becomes an unexpected value, a drive current exceeding the absolute rating of the LED does not flow through the LED.
In contrast, when the pulsed backlight driving is adopted, the duty ratio of the PWM signal (the LED control signal Lctl) is constant, and a driving current having the magnitude of the allowable forward current under the duty ratio condition is supplied to the LED. For example, when the relationship between the duty ratio of the PWM signal and the allowable forward current is as shown in fig. 15, the drive current of only 35mA can be supplied to the LED when the duty ratio is 100%, but the drive current of 100mA can be supplied to the LED when the duty ratio is 10%. On the premise as described above, when a drive current of 100mA is supplied to the LED at a duty ratio of 10%, if the PWM signal is fixed at a high level due to any abnormality, the drive current of 100mA is continuously supplied to the LED. As a result, abnormal heat generation of the LEDs occurs as described above, and as a result, deformation and ignition of the components of the backlight occur.
Disclosure of Invention
Technical problem to be solved by the invention
Therefore, it is desirable to prevent abnormal heat generation of the LED in the liquid crystal display device employing the pulsed backlight driving.
Means for solving the problems
(1) A liquid crystal display device according to some embodiments of the present invention includes:
a display unit that displays an image;
a light source that irradiates the display unit with light;
a light source control unit that outputs a PWM signal having a constant duty ratio so that the light source is intermittently turned on based on a display synchronization signal;
a light source driving unit that controls a driving current supplied to the light source based on a PWM signal output from the light source control unit; and
and a monitoring control unit that monitors at least one of the PWM signal, the drive current, and the display synchronization signal as a monitoring target, and controls a waveform of the PWM signal so that the drive current supplied to the light source becomes zero when an abnormality of the monitoring target is detected.
According to such a configuration, the monitoring control unit monitors and controls at least one of the PWM signal of the light source, the drive current supplied to the light source, and the display synchronization signal. When an abnormality of the monitoring target is detected, the waveform of the PWM signal is controlled so that the drive current supplied to the light source becomes zero. Therefore, even if the PWM signal is fixed at the on level due to any abnormality, the PWM signal is immediately fixed at the off level. Therefore, a large current does not flow through the light source for a long time, thereby preventing abnormal heat generation of the light source. Here, the light source control unit outputs a PWM signal having a constant duty ratio so as to intermittently light the light source. Namely, pulsed backlight driving is employed. In the above, abnormal heat generation of the light source in the liquid crystal display device employing the pulsed backlight driving is prevented.
(2) In addition, the liquid crystal display device according to some embodiments of the present invention includes a display driving unit that drives the display unit based on an image signal and the display synchronization signal in addition to the configuration of the above (1),
the light source control unit is provided in the display driving unit.
(3) In addition to the configuration of (2), the liquid crystal display device according to some embodiments of the present invention includes a host computer that supplies the image signal and the display synchronization signal to the display driving unit.
(4) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure (3) above,
the monitoring control unit is provided in the host.
(5) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure of (4) above,
the monitoring control unit initializes the display driving unit and the light source driving unit when an abnormality of the monitoring target is detected.
(6) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure (3) above,
the monitor control unit is provided in the display driving unit.
(7) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure of (6) above,
the monitoring control unit initializes the display driving unit, the light source driving unit, and the host computer when detecting an abnormality of the monitoring target.
(8) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure (3) above,
the monitoring control unit is provided in the light source driving unit.
(9) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure of (8) above,
the monitoring control unit initializes the display driving unit, the light source driving unit, and the host computer when detecting an abnormality of the monitoring target.
(10) Further, the liquid crystal display device according to some embodiments of the present invention includes the structure (2) described above,
the monitoring control unit initializes the display driving unit and the light source driving unit when an abnormality of the monitoring target is detected.
(11) Further, a liquid crystal display device according to some embodiments of the present invention includes the structure according to any one of the above (1) to (10),
the monitoring control unit determines that an abnormality has occurred in the monitoring target when the on period of the PWM signal is longer than a predetermined period, with the PWM signal being the monitoring target.
(12) Further, a liquid crystal display device according to some embodiments of the present invention includes the structure according to any one of the above (1) to (10),
the monitoring control unit determines that an abnormality has occurred in the object to be monitored when the driving current is applied to the object to be monitored and the state where the magnitude of the driving current is equal to or greater than a predetermined magnitude continues for longer than a predetermined period.
(13) A method for controlling a liquid crystal display device according to some embodiments of the present invention includes: a display unit that displays an image; a light source that irradiates the display unit with light; a light source control unit that outputs a PWM signal having a constant duty ratio so that the light source is intermittently turned on based on a display synchronization signal; and a light source driving unit that controls a driving current supplied to the light source based on a PWM signal output from the light source control unit, the method of controlling the liquid crystal display device including:
a monitoring step of monitoring at least one of the PWM signal, the drive current, and the display synchronization signal as a monitoring target; and
and a control step of controlling a waveform of the PWM signal so that a drive current supplied to the light source becomes zero when the abnormality of the monitoring target is detected.
Effects of the invention
The above and other objects, features, aspects and effects of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.
Drawings
Fig. 1 is a block diagram showing the overall configuration of a liquid crystal display device according to a first embodiment.
Fig. 2 is a block diagram showing the overall configuration of the liquid crystal display device in all the embodiments.
Fig. 3 is a diagram for explaining the structure of the display unit in all the embodiments.
Fig. 4 is a circuit diagram showing the structure of a pixel formation portion in all embodiments.
Fig. 5 is a diagram showing an example of waveforms of LED control signals in all the embodiments.
Fig. 6 is a schematic diagram showing the structure of the backlight in all the embodiments.
Fig. 7 is a block diagram showing a configuration example of the LED driver in all the embodiments.
Fig. 8 is a circuit diagram for explaining a configuration for fixing the LED control signal at a low level in the first embodiment.
Fig. 9 is a diagram for explaining the effects of the first embodiment.
Fig. 10 is a diagram for explaining the effects of the first embodiment.
Fig. 11 is a block diagram showing the overall configuration of the liquid crystal display device according to the second embodiment.
Fig. 12 is a block diagram showing the overall configuration of the liquid crystal display device according to the third embodiment.
Fig. 13 is a block diagram for explaining a conventional example.
Fig. 14 is a diagram for explaining a problem of the conventional example.
Fig. 15 is a diagram showing an example of the relationship between the duty ratio of the PWM signal and the allowable forward current.
Detailed Description
Hereinafter, embodiments will be described with reference to the drawings.
< 0. first >)
< 0.1 Overall Structure >
Before each embodiment is described in detail, the common matters in all embodiments will be described. Fig. 2 is a block diagram showing the overall configuration of the liquid crystal display device in all the embodiments. As shown in fig. 2, the liquid crystal display device includes a
As shown in fig. 3, a plurality of source bus lines (video signal lines) SL and a plurality of gate bus lines (scanning signal lines) GL are arranged in the
The operation of the components shown in fig. 2 will be described below. The
The
The
As described above, the
< 0.2LCD driver architecture >
Next, details of the
The timing control circuit 211 controls the operations of the gate driver 213, the source driver 214, and the LED control circuit 215 based on the display synchronization signal SY transmitted from the
In addition, a display driving section is realized by the
< 0.3 feature >
Next, features common to all the embodiments will be explained. The liquid crystal display device in all the embodiments is provided with a monitoring control unit that monitors at least one of the LED control signal Lctl, the drive current supplied to the
< 1. first embodiment >
< 1.1 Structure >
Fig. 1 is a block diagram showing the overall configuration of a liquid crystal display device according to a first embodiment. In the present embodiment, as shown in fig. 1, the
The
When detecting an abnormality of the monitoring target, the
The
< 1.2 Effect >
According to the present embodiment, the state of the LED control signal Lctl or the supply state of the drive current to the
< 2. second embodiment >
< 2.1 Structure >
Fig. 11 is a block diagram showing the overall configuration of the liquid crystal display device according to the second embodiment. In the present embodiment, as shown in fig. 11, the
The
When detecting an abnormality of the monitoring target, the
< 2.2 Effect >
In the present embodiment, as in the first embodiment, abnormal heat generation of the LED in the liquid crystal display device driven by the pulsed backlight can be prevented.
< 3. third embodiment >
< 3.1 Structure >
Fig. 12 is a block diagram showing the overall configuration of the liquid crystal display device according to the third embodiment. In the present embodiment, as shown in fig. 12, the monitoring control unit 41 is provided in the
The monitoring control unit 41 monitors the LED control signal Lctl or the drive current supplied to the
When detecting an abnormality of the monitoring target, the monitoring control unit 41 forcibly fixes the state of the LED control signal Lctl at a low level so that the drive current supplied to the
< 3.2 Effect >
In the present embodiment, as in the first embodiment, abnormal heat generation of the LED in the liquid crystal display device driven by the pulsed backlight can be prevented.
< 4. other >)
In each of the above embodiments, a monitoring control unit is provided in any one of the
The present invention has been described in detail, but the above description is illustrative in all aspects and is not intended to limit the present invention. It is to be understood that various other adaptations and modifications may be made without departing from the scope of the invention.
- 上一篇:一种医用注射器针头装配设备
- 下一篇:区域背光的调节方法、装置和存储介质