JP4907068B2 - Image display device - Google Patents

Description

  The present invention relates to improvement of display quality of moving images of an image display device, particularly an active matrix type LCD (liquid crystal display device).

  In recent years, the use of LCD (Liquid Crystal Display) has been expanded from PC monitors to TVs due to the increase in screen size and brightness.

  The LCD is a so-called hold-type light emission display device, and the display luminance does not change sharply within one frame. For this reason, there is little flicker (flicker) and it is suitable for displaying still images. On the other hand, with respect to the display of moving images, as described in Non-Patent Document 1, an impulse-type light emission display device is more suitable.

  In the hold type light emitting display device, the moving image is displayed as a photograph of a moving subject taken with a long exposure. This is called moving image blur (blurring, blurring, tailing, blurring, dragging, Blur).

  Several prior applications related to impulse-type light emission are listed. In the technique disclosed in Patent Document 1, light from the lamp is intermittently blocked using a shutter. In the technique disclosed in Patent Document 2, a plurality of lamps are caused to emit light sequentially in synchronization with scanning of the gate line. The technique disclosed in Patent Document 3 emits pulsed light synchronized with the vertical synchronizing signal vs twice or more in one frame.

[Hold type display device]
FIG. 33 is a block diagram of a transmissive LCD having a hold-type light emission backlight. Here, as an example of the resolution, the resolution of the LCD is assumed to be 11 × 8 in width. In FIG. 33, a thin wiring represents a signal line or a bus line, and a thick wiring represents a power line.

  As shown in FIG. 33, the hold-type light emission display device includes a video signal input terminal 1, a control circuit 2, a source driver 3, a gate driver 4, and a liquid crystal panel 5. In addition, source lines s0, s1, s2,..., S10 are connected to the source driver 3, and gate lines g0, g1, g2,. A liquid crystal cell (not shown) is formed at each intersection of the source line and the gate line. Each time the liquid crystal cell is scanned, the light transmittance is changed according to the video signal.

  Further, the hold type light emitting display device includes a light emission power input terminal 6, a power supply circuit 7, a lamp 8 h, and a light guide plate 9. A fluorescent lamp or the like is suitable for hold-type light emission.

  FIG. 34 is a diagram qualitatively explaining the motion blur caused by hold-type light emission. This FIG. 34 schematically shows a state in which a white object of arbitrary vertical size moves in a black background from top to bottom at a speed of one pixel per frame. Yes.

  Part A of FIG. 34 shows the light emission waveform of the backlight. The horizontal axis is time (unit is vertical cycle, frame), and the vertical axis is emission luminance (unit is arbitrary). When displaying an interlaced video signal, the unit of the horizontal axis may be a field. Two fields correspond to one frame.

  In A part of FIG. 34, the light emission luminance is always constant.

  A portion B in FIG. 34 shows an object to be displayed on the display device. The horizontal axis is space (unit is picture element, pixel), and the vertical axis is transmittance of each picture element (unit is arbitrary). In the class of black and white display devices used in a three-plate projector, dots may be used as the unit of the horizontal axis. One pixel corresponds to three dots of RGB color or three subpixels.

  In part B of FIG. 34, the contour of the object is sharply cut. A part C in FIG. 34 represents a state in which an object moves on the screen (the horizontal axis is time, and the vertical axis is space). Each picture element is updated at a frequency of once per frame. As the object moves, the oblique hatched area emits light. When the movement of this object is followed with eyes, the luminance change is integrated (averaged) on the retina of the eye along the direction of the black arrow in the figure, and is reflected in the user's eyes as shown by D part in FIG. In this figure, the response time of the liquid crystal molecules and the scanning time of the gate are ignored.

  The portion E in FIG. 34 is the density of the object actually reflected on the retina. The horizontal axis is space (unit is a pixel), and the vertical axis is display luminance (unit is arbitrary). Comparing part E in FIG. 34 with part B, it can be seen that the object shown in part E in FIG. 34 is duller than the contour of the object shown in part B in FIG. This blurring of the contour is a moving image blur.

[Impulse type light emitting display]
FIG. 35 to FIG. 39 are explanatory diagrams of impulse-type light emission display devices. FIG. 35 is an example of a block diagram of an LCD having an impulse-type light emission backlight. Hereinafter, an LCD having an impulse-type light emission backlight will be described focusing on differences from a hold-type light emission display device.

  As shown in FIG. 35, an LCD having an impulse-type light emission backlight includes a lighting signal generation circuit 10, a switch 11, a lamp 8i, and a light guide plate 9a. Note that members having the same functions and configurations as those in FIG. 33 are denoted by the same reference numerals in FIG.

  35 outputs the vertical synchronization signal vs to the lighting signal generation circuit 10, and the lighting signal generation circuit 10 outputs the lighting signals p0 to p3 to the switch 11. The switch 11 passes or blocks the power flowing from the power supply circuit 7 to the lamp 8i according to the signal level of the lighting signals p0 to p3. A lamp such as an LED (light emitting diode) is suitable for impulse light emission.

  The light guide plate 9a is divided into a plurality of rectangular regions in parallel with the gate lines g0 to g7. In the configuration shown in FIG. 35, the light guide plate 9a is divided into four regions L0 to L3. The region L0 illuminates the picture elements scanned by the gate lines g0 and g1. Similarly, the region L1 illuminates the pixels scanned by the gate lines g2 and g3, the region L2 the gate lines g4 and g5, and the region L3 the gate lines g6 and g7. The lighting and extinguishing of the areas L0 to L3 are independently controlled by the corresponding lighting signals p0 to p3.

  Further, the number of regions into which the light guide plate is divided is not necessarily the same as the number of gate lines. For example, in the configuration of FIG. 35, the light guide plate is divided into four, but there are eight gate lines. Further, the number of lamps that illuminate one area is not limited to one. In the configuration of FIG. 35, two lamps illuminate one area.

  FIG. 36 shows an example in which the lighting signal generation circuit 10 of FIG. 35 is realized by a digital circuit. As shown in FIG. 36, the lighting signal generating circuit 10 includes an input terminal 101 for a vertical synchronizing signal vs, a counter 102, a lighting time setting means 103r, a turn-off time setting means 103f, and a coincidence comparator (Equality Comparator) 104r. 104f, SR flip-flop 105, output terminals 106 for lighting signals p0 to p3,... Setting means 107 for holding the time of a quarter frame, and delay circuit 108. In FIG. 36, a dotted line denoted by reference numeral 109 indicates that the circuit block is the same in the range surrounded by the dotted line.

  In FIG. 36, the setting means 103r, 103f, and 107 are hatched. In FIG. 36, a thin wiring represents one signal line, and a thick wiring represents a bus line having a width of 1 bit or more. Further, the vertical synchronization signal vs is negative logic (the High period is longer than the Low period), and the lighting signals p0 to p3 are positive logic (lights on High and lights off on Low). In FIG. 36, the power source, the GND terminal, and the clock line are omitted.

  The counter 102 is cleared by the pulse of the vertical synchronization signal vs. That is, the counter 102 operates in synchronization with the vertical synchronization signal vs. The circles at the input terminals of the counter 102 indicate that the circuit operates with negative logic.

  The setting means 103r and 103f each have a function of holding the lighting timing and extinguishing timing of the lamp 8i. The two coincidence comparators 104r and 104f output a pulse to the SR flip-flop 105 when the output value of the counter 102 coincides with a predetermined set value. The light emission luminance of the lamp is determined by the duty of the output signal of the SR flip-flop 105.

  There are a total of four circuit blocks 109. The setting means 107 and the delay circuit 108 have a function for determining the operation timing of each system. The four circuit blocks 109 operate in parallel while maintaining a phase difference of a quarter frame.

  36 can be realized by a jumper resistor, a DIP switch, a ROM, a register, or the like. Further, these setting means are not shown in FIG. Display device designers, production personnel, installers, or viewers can change the parameters held by these setting means according to the application, video signal source, viewer preference, etc. Can be adjusted to the desired image quality.

  FIG. 37 is a diagram illustrating operation waveforms of the respective units in FIG. A pulse signal synchronized with the vertical synchronization signal vs is output to the gate lines g0 to g7 and the lines of the lighting signals p0 to p3. For convenience of illustration, only four g0, g2, g4, and g6 are drawn out of the eight gate lines g0 to g7. The ON / OFF timing of the lighting signals p0 to p3 is determined in consideration of the response time of liquid crystal molecules and the gate scanning time.

  FIG. 38 is a diagram showing light emission waveforms in the regions L0 to L3 of the light guide plate 9a in FIG. As shown in FIG. 38, the regions L0 to L3 of the light guide plate 9a sequentially emit light in the same direction as the scanning of the gate (from the top to the bottom of the screen in FIG. 38) in synchronization with the vertical synchronization signal vs.

  FIG. 39 is a diagram for explaining motion blur of an LCD having an impulse-type light emission backlight. Note that the notation in FIG. 39 is the same as that in FIG. Further, the region L0 in FIG. 38 and the portion A in FIG. 39 show waveforms having the same luminance, but for the convenience of description in the drawing, the scale of the horizontal axis (time axis) is different.

Comparing the E portion of FIG. 39 with the E portion of FIG. 34, it can be seen that the former, that is, the impulse-type light emission, has sharper contours and improved motion blur.
Japanese Laid-Open Patent Publication No. 3-284791 (released on December 16, 1991) JP-A-11-202285 (published July 30, 1999) JP 2000-322029 A (published on November 24, 2000) “Liquid crystal improves video display, PDP competes with low power consumption”, Nikkei Electronics, 2002, 11-18, 110 pages.

  By the way, it has been said that the blinking of light 50 to 60 times per second exceeds the critical fusion frequency (hereinafter referred to as CFF) and cannot be perceived by human eyes and flicker does not occur. For this reason, the vertical frequency of the TV is also set to about 50 to 60 Hz.

  In recent years, however, LCDs have increased in screen size and brightness, and CFF has increased. This is due to the difference in characteristics between the cones and rods of photoreceptor cells and the Ferry-Porter law. As a result, even with an impulse type light emission of 50-60 Hz, flicker interference comes out. However, the vertical frequency of TV broadcasting cannot be easily changed because it is defined by NTSC (National Television Standards Committee), PAL (Phase Alternation by Line) and other standards.

  In addition, the use of TV has expanded, and LCDs have been adopted for EPG (Electronic Program Guide), WEB browsers, still photo images, store sales promotion demonstrations, various facility guidance, and other displays. For this reason, the LCD is increasingly used for displaying still images, and the display quality is becoming more and more important.

  Conventionally, flicker has been thought to be only one of display disturbances. However, after that, it was pointed out that flicker caused eye fatigue and reduced work efficiency, leading to an increase in the refresh rate of the PC. And today, Flicker is suspected of being at risk of dizziness, malaise, vomiting, and epilepsy. In the future, flicker may even turn into a safety issue rather than a display quality issue.

  For this reason, it can be said that the negative effect of flicker is greater than the effect of reducing moving image blur at present for impulse-type light emission.

  FIG. 40 is a diagram for explaining the effect of reducing motion blur by the technique described in Patent Document 3. Note that the notation in FIG. 40 is the same as that in FIG. Flicker is improved by impulse emission twice per frame as shown in part A of FIG. However, as in the E part of FIG. 40, the flat portion 2 appears between the slope 1 and the slope 3 of the contour of the moving image, and the shading slope is broken into two. That is, a side effect in which the outline of the moving image appears doubled appears.

  Thus, until now, there has been no effective countermeasure against flicker interference of impulse light emission. The present invention has been made in view of the above-described conventional problems, and provides an image display device that can improve motion blur and flicker interference.

  To explain in a word, the present invention improves the luminance change (see the E portion in FIG. 39) of the contour portion of the moving image to the luminance change as shown in the E portion in FIG. This is an application of the principle of “examination of video image quality improvement method of AMLCD” published at the Institute of Image Information and Television Engineers on March 22, 2004.

  Specifically, the image display device of the present invention includes an image display unit that modulates light based on a video signal, and a light source body that illuminates the image display unit. Is characterized in that the image display means is illuminated by light in which a pulse component i emitted once per frame of the video signal and a pulse component h emitted at a frequency higher than the frame frequency are mixed. .

  According to the said structure, the moving image displayed on an image display means is illuminated with the light with which the pulse component i emitted from the light source body and the pulse component h were mixed. Therefore, with regard to the luminance of the contour portion of the moving image, there are a portion that changes corresponding to the light in which the pulse component i and the pulse component h are mixed, and a portion that changes corresponding to the pulse component h.

  Here, since the pulse component h is emitted at a frequency higher than the frame frequency, that is, at a frequency higher than that of the pulse component i, the portion whose luminance changes corresponding to the pulse component h in the contour portion of the moving image is a human moving object. It cannot be discriminated by visual acuity. Thereby, the outline of a moving image does not become double. In addition, the portion where the luminance changes corresponding to the light in which the pulse component i and the pulse component h are mixed in the contour portion of the moving image emits light longer than the other portions by the amount of the pulse component i. It is easy to discriminate based on human moving vision. Thereby, moving image blur does not occur.

  Furthermore, since the frequency of the pulse component h is set higher than the frame frequency, flicker due to the pulse component h is not perceived by humans. Further, since the luminance due to the pulse component i can be reduced by the amount of light emission luminance contributed by the pulse component h, flicker can be reduced as a whole while keeping the display luminance constant.

  Thus, according to the image display apparatus of the present invention, it is possible to reduce flicker while moving image blur is improved.

  Furthermore, in the image display device of the present invention, it is preferable that the emission duration of the pulse component i is longer than the emission duration of the pulse component h.

  As described above, the portion whose luminance changes corresponding to the light in which the pulse component i and the pulse component h are mixed in the contour portion of the moving image emits light for a longer time than the other portions by the amount of the pulse component i. Therefore, as the light emission time of the pulse component i is increased as in the above configuration, it becomes easier to discriminate the inclination by the human visual acuity. That is, moving image blur can be more reliably prevented.

  Furthermore, in the image display device of the present invention, it is preferable that the light emission start time of the pulse component h is not synchronized with the light emission start time of the pulse component i.

  According to the above configuration, since the light emission start time always shifts between the pulse component h and the pulse component i, the luminance changes in correspondence with the pulse component h with respect to the contour portion of the moving image displayed on the image display means. The portion can be made more indistinguishable with human visual acuity more reliably. In addition, in the contour portion of the moving image, the portion where the luminance changes corresponding to the light in which the pulse component i and the pulse component h are mixed can be more easily discriminated, and the moving image blur can be more reliably prevented.

  Furthermore, in the image display device of the present invention, it is preferable that the pulse component h is emitted twice or more for each frame of the video signal.

  According to the above configuration, the magnitude of the first harmonic component can be reduced with respect to the luminance of light in which the pulse component h and the pulse component i are mixed. This makes it possible to reduce flicker more reliably.

  Furthermore, in the image display device of the present invention, it is preferable that the pulse component h is emitted at a frequency higher than the critical fusion frequency.

  According to the above configuration, since the pulse component h is emitted at a frequency higher than the critical fusion frequency, the pulse component h does not cause flicker. As a result, flicker interference can be reliably reduced.

  Furthermore, in the image display device of the present invention, it is preferable that the pulse component i and the pulse component h are generated by supplying the same power to the light source body.

  According to the above configuration, the pulse component i and the pulse component h are emitted with the same power. The generation of the pulse component i and the pulse component h with the same power in this way can be easily realized by switching the power from the power source with a switch controlled by a digital circuit, for example. Therefore, power consumption in the image display apparatus can be reduced.

  Furthermore, in the image display device of the present invention, it is preferable that the light source body emits both the pulse component i and the pulse component h.

  According to the above configuration, since both the pulse component i and the pulse component h are emitted by the light source body, it is not necessary to mix the pulse component i and the pulse component h using an optical system such as a light guide plate. Therefore, luminance unevenness and chromaticity unevenness in the image display means can be reduced.

  Furthermore, the image display device of the present invention preferably includes a logic circuit that synthesizes the signal for generating the pulse component i and the signal for generating the pulse component h.

  According to the above configuration, the pulse component i and the pulse component h can be mixed by a logic circuit without using a power circuit or an optical system. Further, since no power circuit is used, the cost increase by adopting the above-described configuration is minimal, and since no optical system is used, luminance unevenness and chromaticity unevenness in the image display means can be reduced.

  Furthermore, in the image display device of the present invention, the circuit for generating the pulse component i and the circuit for generating the pulse component h are both constituted by digital circuits, and the circuit for generating the pulse component h. Is preferably shorter than the bit length of the circuit for generating the pulse component i.

  According to the above configuration, since the bit length of the circuit that generates the pulse component h is shorter than the bit length of the circuit that generates the pulse component i, the scale of the circuit that generates the pulse component h can be reduced. Can do. Thereby, it is possible to suppress an increase in the circuit scale for achieving the effect of improving the motion blur and the effect of reducing the flicker interference.

  Furthermore, the image display device of the present invention generates the pulse component i by generating a signal having a frequency higher than the frequency of the pulse component i and the pulse component h, as described in Example 3 described later. Preferably, the signal to be generated and the signal for generating the pulse component h are supplied to a synthesized signal.

  According to the above configuration, the luminance of the light in which the pulse component h and the pulse component i are mixed is adjusted by reducing the duty of the signal (signal d) having a frequency higher than that of the pulse component i and the pulse component h. It becomes possible. Further, since the frequency of the signal d is set higher than the frequencies of the pulse component h and the pulse component i, the relationship between the pulse component h and the pulse component i is maintained before and after the signal d is supplied. Therefore, the image display quality in the image display means does not deteriorate.

  Note that the frequency order of the signal d is preferably higher by three digits or more than the frequency order of the pulse component i and the pulse component h. As a result, the light emitted by the signal d is not discriminated by humans, and the light can be prevented from causing flicker.

  Furthermore, the image display device of the present invention is an image quality adjusting means for fixing the light emission duration of the pulse component h and increasing or decreasing the frequency of the pulse component h as described in Example 1 of Example 2 above. It is preferable to provide.

  The image display means may display a moving image or a still image. For each of the case where a moving image is displayed and the case where a still image is displayed, an appropriate frequency of the pulse component h and an emission duration of the pulse component h exist.

  According to the above configuration, since the frequency of the pulse component h can be increased or decreased by the image quality adjusting means, the frequency of the pulse component h can be set to a frequency suitable for the image displayed on the image display means. Thereby, the image quality can be adjusted according to the use of the image display device, the source of the video signal, the preference of the viewer, and the like.

  Further, since the image quality adjusting means fixes the light emission duration of the pulse component h, it is not necessary to extremely shorten the pulse component h in order to adjust the image quality. Therefore, switching noise countermeasures are easy.

  Furthermore, the image display device of the present invention, as described in Example 2 2 described later, fixes the frequency of the pulse component h, while increasing or decreasing the emission duration of the pulse component h. It is preferable to provide.

  Further, according to the above configuration, the light emission duration of the pulse component h can be increased or decreased by the image quality adjusting means, so that the pulse component h can be set to the light emission duration suitable for the image displayed on the image display means. Thereby, the image quality can be adjusted according to the use of the image display device, the source of the video signal, the preference of the viewer, and the like.

  Further, since the image quality adjusting means fixes the frequency of the pulse component h, it is possible to easily take measures against beats due to interference with the horizontal scanning frequency and the like.

  In addition, as described in Example 3 described later, the image display device of the present invention is configured such that all of the plurality of lamps constituting the light source body are displayed while an image is displayed on the image display means. It is preferable that there is no time for lighting at the same time.

  According to the above configuration, since there is no time for all the lamps constituting the light source body to be turned on simultaneously, the instantaneous maximum rating of the power source circuit of the light source body can be reduced. Therefore, a small and inexpensive power supply circuit can be used. Further, harmonics flowing in the power supply circuit can be reduced.

  Further, as described in 1 of Example 3, in the image display device of the present invention, all the lamps constituting the light source body are turned off simultaneously while a valid image is displayed on the image display device. It is preferred that there is no time to do.

  According to the above configuration, since all the lamps constituting the light source body do not have time to turn off simultaneously, the switching operation of the power supply circuit can be stabilized.

  The image display device of the present invention includes image display means for modulating light based on a video signal, and K (K ≧ 2, K is an integer) light source bodies for illuminating the image display means. The light source bodies are grouped into N systems (2 ≦ N ≦ K, where N is an integer) whose light emission is controlled independently from each other, and one light source body is provided for each frame of the video signal from each system. Illuminating the image display means by emitting light in which the pulse component i emitted once and the pulse component h emitted at a frequency higher than the frame frequency are mixed, and the emission start time of the pulse component i is The image display means may be configured to be controlled for each of the N systems in accordance with the timing at which the video is scanned.

  According to the above configuration, since the image display unit is illuminated with the light in which the pulse component i and the pulse component h are mixed, flicker can be reduced in a state where the moving image blur is improved.

  Further, in the image display device of the present invention, as described in 1 of Example 3 to be described later, the pulse component h is controlled so that the light emission start times are shifted from each other with respect to the N systems. It is preferable.

  According to the above configuration, the light source bodies composed of the N systems are controlled so that the light emission start times are shifted from each other, so that the instantaneous maximum rating of the power supply circuit used for the light source body can be reduced.

  Furthermore, the image display apparatus of the present invention relates to a system in which the number of the pulse components h is M (2 ≦ M ≦ N ≦ K, M is an integer) as described in 2 of Example 3 described later. It is preferable that the light emission start times are controlled so as to deviate from each other.

  According to the above configuration, since the number of systems of the pulse component h that is controlled so that the light emission start time is shifted is less than the number of systems for controlling the light emission start time of the pulse component i, the circuit that generates the pulse component h The gate scale can be reduced.

  Furthermore, the image display device of the present invention does not have time for all of the light source bodies to be turned on simultaneously while an image is displayed on the image display means, as described in Example 3 described later. It is preferable.

  According to the above configuration, there is no time for all of the light source bodies to be turned on simultaneously, so the instantaneous maximum rating of the power supply circuit of the light source body can be reduced. Therefore, a small and inexpensive power supply circuit can be used.

  Furthermore, the image display device of the present invention has a time during which all of the light source bodies are simultaneously turned off while a valid video is displayed on the image display device, as described in Example 3 described later. It is preferable that there is no.

  According to the above configuration, since all the light source bodies do not have time to be turned off at the same time, the switching operation of the power supply circuit can be stabilized.

  Furthermore, the image display device of the present invention includes a generation circuit for the pulse component i and the pulse component h, and a switch for controlling the light emission of the light source body, as described in Example 4 described later. A generation circuit that outputs a lighting signal including a plurality of systems to the protection circuit so that the light source body emits light, and the protection circuit is the same with respect to the lighting signals including the plurality of systems. When the number of systems in the logical state is counted and the number of systems exceeds a predetermined allowable value, part or all of the light source body is preferably turned off.

  According to the above configuration, the protection circuit counts the number of systems in the same logical state with respect to the lighting signal, that is, the number of switches that are simultaneously turned on. If the number of systems exceeds an allowable value, the light source bodies are forcibly turned off by the protection circuit, so that it is possible to prevent an accident in which a number of light source bodies exceeding the allowable limit number emit light simultaneously. . Thereby, for example, it is possible to prevent the viewer from being exposed to a powerful flash for a moment.

  The image display apparatus of the present invention includes an image display unit that modulates light based on a video signal and K pieces (K ≧≧) that illuminate the image display unit, as described in Example 2 described later. 2 and K are integers), and the K light source bodies are N (2 ≦ N ≦ K, N is an integer) system in which light emission is controlled independently of each other. And illuminating the image display means by emitting light comprising a pulse component i emitted once per frame of the video signal from each system, The light emission start time is controlled for each of the N systems in accordance with the timing at which the image is scanned in the image display means, and includes a generation circuit for the pulse component i and a switch for controlling the light emission of the light source body. With protection circuit between The generation circuit outputs a lighting signal composed of a plurality of systems to cause the light source body to emit light to the protection circuit, and the protection circuit counts the number of systems in the same logical state with respect to the lighting signals composed of the plurality of systems. If the number of the systems exceeds a predetermined allowable value, a part or all of the light source body may be turned off.

  According to the above configuration, the protection circuit counts the number of systems in the same logical state with respect to the lighting signal, that is, the number of switches that are simultaneously turned on. If the number of systems exceeds an allowable value, the light source bodies are forcibly turned off by the protection circuit, so that it is possible to prevent an accident in which a number of light source bodies exceeding the allowable limit number emit light simultaneously. . Thereby, for example, it is possible to prevent the viewer from being exposed to a powerful flash for a moment.

  Furthermore, the image display apparatus of the present invention includes a current limiting element between the light source body and the switch for controlling the lighting of the light source body, as described in Example 5 of 1 described later. It is preferable. Alternatively, as described in Example 5-2, which will be described later, a current limiting element is provided between the switch that controls the lighting of the light source body and the power supply circuit that supplies the lighting power of the light source body. May be.

  According to the above configuration, since the inrush current flowing through the light source body can be reduced by the current limiting element, the power line in the image display device can be protected from a short circuit accident.

  Furthermore, the current limiting element is preferably a passive element that consumes reactive power.

  According to the above configuration, since the passive element that consumes reactive power is used as the current limiting element, it is possible to protect the power line in the image display apparatus from a short circuit accident without increasing the power consumption of the image display apparatus.

  Further, as described in Example 6-2, which will be described later, the image display device of the present invention includes an image display unit that modulates light based on a video signal and K pieces (K ≧≧) that illuminate the image display unit. 2 and K are integers), and the K light source bodies are N (2 ≦ N ≦ K, N is an integer) system in which light emission is controlled independently of each other. And illuminating the image display means by emitting light comprising a pulse component h emitted from each system at a frequency higher than the frame frequency. It is preferable that the light emission start times of the individual systems are controlled so as to deviate from each other.

  When the image display device is for guidance display of various facilities or for mobile devices, moving image blur hardly poses a problem. Therefore, the pulse component i is not necessarily irradiated from the light source body to the image display means.

  Further, since the pulse components h are controlled so that the light emission start times are shifted from each other, the load applied to the power source circuit of the light source body can be reduced.

  Furthermore, the image display apparatus of the present invention includes a protection circuit between the generation circuit of the pulse component h and the switch that controls the light emission of the light source body, as described in Example 6 of 1 described later. The generation circuit outputs a lighting signal composed of a plurality of systems to the protection circuit to cause the light source body to emit light, and the protection circuit is in the same logic state with respect to the lighting signals composed of the plurality of systems. When the number of systems is counted and the number of systems exceeds a predetermined allowable value, it is preferable to turn off part or all of the light source body.

  According to the above configuration, the protection circuit counts the number of systems in the same logical state with respect to the lighting signal, that is, the number of switches that are simultaneously turned on. If the number of systems exceeds an allowable value, the light source bodies are forcibly turned off by the protection circuit, so that it is possible to prevent an accident in which a number of light source bodies exceeding the allowable limit number emit light simultaneously. . Thereby, for example, it is possible to prevent the viewer from being exposed to a powerful flash for a moment.

  Further, the image display apparatus having the above-described configuration does not have time for all of the light source bodies to be turned on simultaneously while an image is displayed on the image display means, as described in Example 6 described later. It is preferable.

  According to the above configuration, since there is no time for all of the lamps constituting the light source body to be turned on simultaneously, the instantaneous maximum rating of the power source circuit of the light source body can be reduced. Therefore, a small and inexpensive power supply circuit can be used. Further, harmonics flowing in the power supply circuit can be reduced.

  Furthermore, it is preferable that the image display device having the above-described configuration does not have time to turn off all the light source bodies at the same time while a valid video is displayed on the image display device.

  According to the above configuration, since all the lamps constituting the light source body do not have time to turn off simultaneously, the switching operation of the power supply circuit can be stabilized.

  Moreover, it is preferable that the light source body in the image display apparatus of this invention is a semiconductor light-emitting device.

  According to the above configuration, since the semiconductor light emitting element, for example, the light emitting diode is used as the light source body, the pulse component h and the pulse component i can be appropriately emitted from the light source body.

  The image display means in the image display device of the present invention is preferably a liquid crystal panel.

  According to the said structure, the effect which concerns on the image display apparatus of this invention can be acquired about the liquid crystal display device using a liquid crystal panel.

  In the image display device of the image display device of the present invention, it is preferable that the liquid crystal panel is a transmissive liquid crystal panel and the light source body constitutes a backlight of the transmissive liquid crystal panel.

  According to the said structure, the effect which concerns on the image display apparatus of this invention can be acquired about a direct view type liquid crystal display device.

  Further, a plurality of gate lines connected to the liquid crystal panel may be sequentially scanned by an active element provided in the liquid crystal panel.

  According to the above configuration, the effect of the image display device of the present invention can be obtained for the active matrix liquid crystal display device.

  Further, the liquid crystal panel is a transmissive liquid crystal panel, and a plurality of gate lines connected to the transmissive liquid crystal panel are sequentially scanned by active elements provided in the transmissive liquid crystal panel, and the light source body includes: You may comprise the backlight of the said transmissive liquid crystal panel.

  According to the above configuration, the effect of the image display device of the present invention can be obtained for the active matrix transmission type liquid crystal display device.

  According to the present invention, it is possible to improve the display quality of an image display device having a hold-type electro-optical conversion characteristic represented by a liquid crystal display device. Furthermore, it is possible to improve the tailing of moving images and reduce flicker interference.

[First invention]
FIGS. 1-11 is a figure for demonstrating the 1st invention concerning this application. First, the principle of the LCD according to the first invention will be described with reference to FIGS. 1 to 6, focusing on the differences from FIGS. 35 to 40 of the conventional example. Next, modified examples of the LCD according to the first invention will be described with reference to FIGS.

[Principle of the first invention]
FIG. 1 is a block diagram showing an example of the configuration of an LCD according to the first invention. As shown in FIG. 1, the LCD according to the first invention is obtained by replacing the lighting signal generation circuit 10 of FIG. 35 with a lighting signal generation circuit 10a. In FIG. 1, members having the same functions and configurations as those in FIG.

  FIG. 2 is a configuration example (referred to as “1 of Example 1”) of the lighting signal generation circuit 10a (see FIG. 1) in the LCD of the first invention. In FIG. 2, members having the same functions and configurations as those in FIG. 36 are denoted by the same reference numerals. Further, the lighting signal generation circuit 10a shown in FIG. 2 generates impulse signals i0 to i3 synchronized with the vertical synchronization signal vs.

  Further, as shown in FIG. 2, the lighting signal generation circuit 10a includes a counter 202p, a count period setting means 203a of the counter 202p, a lighting time setting means 203r, a turn-off time setting means 203f, and a coincidence comparator 204a. 204r and 204f, an SR flip-flop 205, an OR gate 110, and output terminals 106 for lighting signals p0 to p3.

  The counter 202p is not cleared by the vertical synchronization signal vs. Instead, it is cleared by the output signal of the coincidence comparator 204a. Although the counter 102 operates with negative logic and the counter 202p operates with positive logic, the first invention is not limited to such logic polarity.

  Furthermore, the frequency at which the counter 202p is cleared, that is, the count frequency, needs to be set higher than the critical fusion frequency CFF at which flicker is not visible. The count frequency may be an integer multiple of the vertical frequency or a non-integer multiple, and may be determined so as not to cause a beat due to interference with the horizontal scanning frequency and others. The setting means 203a holds parameters for setting the frequency.

  As described above, the CFF is currently higher than the vertical frequency. For this reason, the count cycle of the counter 202 p in FIG. 2 is shorter than the cycle of the counter 102. Therefore, the bit length of the counter 202p may be shorter than the bit length of the counter 102. As a result, an increase in circuit scale accompanying the implementation of the first invention can be suppressed.

  In addition, the setting unit 203r and the coincidence comparator 204r in FIG. 2 generate the lamp lighting timing, while the setting unit 203f and the coincidence comparator 204f create the lamp extinguishing timing. The lighting / extinguishing timing created in this way is sent to the SR flip-flop 205. The output signal h of the SR flip-flop 205 is output to the OR gates 110.

  Since the counter 202 is not cleared by the vertical synchronization signal vs, the output signal h is not output with a fixed phase difference (time difference) from the impulse signals i0 to i3. That is, the output signal h and the impulse signals i0 to i3 are not synchronized.

  OR gates 110... OR the impulse signals i0 to i3 synchronized with the vertical synchronization signal vs and the high frequency signal h exceeding the CFF, and output them to the output terminals 106 of the lighting signals p0 to p3.

  FIG. 3 is a diagram illustrating operation waveforms of the vertical synchronization signal vs, the impulse signals i0 to i3, the high frequency signal h, and the lamp lighting signals p0 to p3. Since the scanning waveform of the gate line is the same as the conventional example of FIG. 37, the description in FIG. 3 is omitted.

  As shown in FIG. 3, the impulse signals i0 to i3 are emitted once in one vertical cycle, and the high frequency signal h is emitted a plurality of times in one vertical cycle. The lamp lighting signal p0 is a signal obtained by synthesizing the impulse signal i0 and the high-frequency signal h. Similarly, the lighting signal p1 is a signal obtained by combining the impulse signal i1 and the high frequency signal h, the lighting signal p2 is a signal obtained by combining the impulse signal i2 and the high frequency signal h, and the lighting signal p3 is This is a signal obtained by synthesizing the impulse signal i3 and the high frequency signal h.

  FIG. 4 is a diagram showing a light emission waveform of the regions L0 to L3 in the light guide plate 9a of FIG. 1 and a waveform of the power P flowing from the light emission power input terminal 6 to the power supply circuit 7. FIG. 38 is a diagram of a conventional example corresponding to FIG.

  In FIG. 4, the portion hatched with a thick line represents light emission corresponding to the impulse signals i0 to i3 in FIG. 3, and the portion hatched in FIG. 4 represents light emission corresponding to the high-frequency signal h in FIG. To express. As shown in FIG. 4, the light emission time (pulse width) by the impulse signals i0 to i3 is usually longer than the light emission time (pulse width) by the high frequency signal h.

  By the way, the light emission luminance of the backlight unit with the liquid crystal panel removed, that is, the luminance of light emitted from the light guide plate (regions L0 to L3 in FIG. 4) is proportional to the average value of the light emission waveform. In this embodiment, the average value of the light emission waveform is proportional to the duty (lighting time). Therefore, if the luminance specification value of the display device is the same, the duty of the impulse signals i0 to i3 (see FIG. 3) can be reduced by the amount added with the high frequency signal h (see FIG. 3) according to the first invention. it can.

  FIG. 5 is a diagram for explaining the contour density of a moving image according to the first invention. FIG. 32, FIG. 39, and FIG. 40 are explanatory diagrams of the conventional example corresponding to FIG.

  A pulse having a long time interval in the portion A in FIG. 5 is a portion emitting light corresponding to the impulse signals i0 to i3 in FIG. 3, and a thin pulse in the portion A in FIG. 5 is added to the high-frequency signal h in FIG. This is the part that emits light.

  The step 1 and the step 3 in the portion E in FIG. 5 are not recognized as moving image blur because they are difficult to identify with human moving vision. Such details of the image are indistinguishable with dynamic visual acuity. Eventually, only the steep slope 2 is recognized as the outline of the moving image. Note that if the object is stationary, the step 1 and the step 3 disappear, so that the step is not perceived even with static vision. Therefore, even after the object stops, the backlight may continue to be lit with the same light emission waveform as before the stop.

  In the first invention, the influence of the high-frequency signal h appears at both ends of the contour (step 1 and step 3 at portion E in FIG. 5). On the other hand, with the technique described in Patent Document 3, a problem of moving image blur appears at the center of the contour (flat portion 2 in the E portion of FIG. 40). The former shows that the display quality of the outline of the moving image is improved than the latter.

  FIG. 6 shows the Fourier series calculation results of the light emission waveform in the region L0 according to the first invention (see FIG. 4) and the light emission waveform in the region L0 in the prior art (see FIG. 38). 6 is the same as the emission waveform in the region L0 shown in FIG. 4, and the II portion in FIG. 6 is the same as the emission waveform in the region L0 shown in FIG. Part III in FIG. 6 is a harmonic component of the light emission waveform in the region L0 in each of the first invention and the conventional example.

  By the way, the largest cause of flicker is a first harmonic, that is, a component having the same frequency as the vertical frequency. The direct current component does not cause flicker. Second-order and higher-order harmonic components can also be ignored as a cause of flicker.

  Since the degree of flicker interference depends on the display luminance, the average value of the waveform is the same in the III part of FIG. 6 between the first invention and the conventional example. What is necessary is just to compare the magnitude | size of both the 1st harmonics on these conditions.

  As shown in the III part of FIG. 6, the first harmonics of the emission waveforms of the first invention and the conventional example are 0.820 and 1.277, respectively. This means that the former, ie, the first invention, has reduced flicker compared to the latter, ie, the conventional example.

  In addition, since the influence on the flicker of the second or higher order harmonic component is almost negligible, the frequency of the high frequency signal h is preferably at least twice the vertical frequency.

  In the first invention, the light emission component corresponding to the high-frequency signal h blinks at a frequency higher than the critical fusion frequency CFF, and therefore does not cause flicker. However, the high frequency signal h contributes to the light emission luminance of the backlight.

  That is, the light emission by the high frequency signal h is easily perceived. Accordingly, the light emission luminance corresponding to the impulse signals i0 to i3 is lowered. This suppresses flicker interference. This is the effect obtained by replacing the lighting signal generation circuit 10 of FIG. 35 with the lighting signal generation circuit 10a in the first invention.

  The light emission by the high-frequency signal h can be said to be a pseudo hold type light emission. Therefore, hereinafter, a control signal such as the high-frequency signal h or a light emission waveform by the signal is referred to as a pseudo hold pulse.

  In addition, according to the first invention, it is not necessary to mix a plurality of types of lamps, that is, impulse-type light emission lamps and hold-type light emission output light inside the light guide plate 9a (FIG. 1). For this reason, according to the first aspect of the invention, there is an advantage that uneven luminance and uneven chromaticity are not easily caused.

  Furthermore, the switch is easy to control with a digital circuit, and the switch itself does not consume power whether it is ON or OFF. For example, when switching is performed using a bipolar transistor, a large collector loss does not occur in either the saturation region or the cutoff region. Therefore, according to the first invention, not only a heat radiation design such as a heat sink becomes unnecessary, but also it can contribute to low power consumption.

  This is due to the same reason that the efficiency of the class D amplifier circuit is high. However, the present invention relates to a light source control method that takes advantage of the features of class D amplification, rather than dimming the light source of the display device by class D amplification.

  Further, since the first invention is merely modified to the lighting signal generation circuit 10 of FIG. 35, the cost increase with respect to the conventional example is slight. Furthermore, large members such as the light guide plate 9a divided along the gate line and power circuit peripheral members such as the switch 11 are costly members, but the members in the conventional LCD shown in FIG. Can be diverted.

  The first invention does not prevent the light guide plate from being divided. That is, in the first invention, as in the conventional example, the light guide plate may be divided into a plurality of regions, and each region may be illuminated with a lamp of a different system.

  That is, as in the LCD shown in FIG. 35, the plurality of lamps 8i are divided into four systems to illuminate the regions L0 to L3 of the light guide plate 9a, and lighting / extinguishing in each region L0 to L3 is a lighting signal. You may comprise so that it may be controlled independently by p0-p3. Furthermore, the rising timing of each of the impulse signals i0 to i3 may be controlled independently according to the timing at which the image is scanned in the liquid crystal panel 5.

  The number of systems for dividing the light guide plate 9a is not limited to four. Also, the number of lamps that illuminate one area is not limited to two.

[Another embodiment of the first invention]
FIG. 7 shows another example of the configuration of the lighting signal generation circuit 10a shown in FIG. The difference from FIG. 2 is that two setting means 203a and 203r are integrated into one setting means 203, and two coincidence comparators 204a and 204r are integrated into one coincidence comparator 204. The counter 202p in FIG. 7 is cleared by the positive logic output signal of the coincidence comparator 204. However, its function is the same as in FIG. In FIG. 7, members having the same functions and configurations as those in FIG. 2 are denoted by the same reference numerals.

  In Example 1-2, the period and the duty of the pseudo hold pulse signal h can be adjusted by the setting means 203 and 203f, respectively. Note that the phase of the pseudo hold pulse signal h cannot be adjusted. However, since the pseudo hold pulse signal h is a high-frequency signal generated asynchronously with the vertical synchronization signal vs, there is no problem because the image quality does not change depending on the phase.

  According to 2 of Example 1 shown in FIG. 7, the scale of the lighting signal generation circuit 10a can be suppressed from 1 (FIG. 2) of Example 1. In other words, according to the second embodiment, the setting unit 203a and the coincidence comparators 204a and 204r in the first embodiment 1 can be omitted.

  FIG. 8 shows still another configuration example of the lighting signal generation circuit 10a of FIG. 1 (referred to as “3 of Example 1”). The difference from the lighting signal generation circuit 10a shown in FIG. 7 is that a PWM (pulse width modulation) type dimming function is added.

  If the image is too bright, reducing the amplitude of the image signal may cause blackout or increased quantization noise. In order to prevent this, the output of the lamp provided in the display device is generally reduced. Unless the image quality improvement and the light control function are compatible, the commercial value of the display device is impaired. Therefore, in Example 1-3, image quality improvement and dimming function are compatible.

  As shown in FIG. 8, the third lighting signal generation circuit 10a of the first embodiment is identical to the counter 302p, the count cycle and lighting time setting means 303 that are cleared by a positive logic signal, and the extinguishing time setting means 303f. A comparator 304 and an SR flip-flop 305 are provided. Further, the lighting signal generation circuit 10 a includes AND gates 111. In FIG. 8, members having the same functions and configurations as those in FIG.

  The SR flip-flop 305 outputs the PWM dimming signal d to the AND gates 111. AND gates 111 ... take the logical product of the output signals of the PWM dimming signal d and the OR gates 110 ..., and output the result to the output terminals 106 of the lighting signals p0 to p3.

  The generation circuit of the PWM dimming signal d is similar to the generation circuit of the impulse signals i0 to i3 and the pseudo hold pulse signal h. However, the frequency and function of each signal is quite different.

  That is, the impulse signals i0 to i3 are signals having the same frequency as the vertical synchronization signal vs, for example, 60 Hz. On the other hand, the pseudo hold pulse signal h is a signal having a frequency exceeding the critical fusion frequency CFF, for example, 600 Hz. The PWM dimming signal d is a signal having a frequency sufficiently higher than the pseudo hold pulse signal h, for example, 600 kHz. For this reason, the bit length of the counter 302 may be shorter than the bit length of the counter 102 or the counter 202p.

  FIG. 9 is a diagram showing operation waveforms of each part of the circuit of FIG. 8, that is, the vertical synchronization signal vs, the impulse signal i0, the pseudo hold pulse signal h, the PWM dimming signal d, and the lamp lighting signal p0. Note that a part of the PWM dimming signal d and the lamp lighting signal p0 is extracted and the time axis is enlarged.

  If the duty of the PWM dimming signal d is reduced by using the setting means 303 and 303f, the relationship between the impulse signals i0 to i3 and the pseudo hold pulse signal h is maintained, that is, the display quality is maintained, Dimming can be reduced.

  Further, if the frequency of the PWM dimming signal d is made, for example, three orders of magnitude higher than the frequency of the pseudo hold pulse signal h, the dimming error is 0.1% (1) without managing the phase of the PWM dimming signal d. / 1000) or less. That is, the influence of the phase of the PWM dimming signal d cannot be identified by human visual acuity. Of course, the light emission by the PWM dimming signal d does not cause flicker.

  For example, if a PWM dimming signal d generating circuit is supplied with, for example, a clock of 100 times the frequency of the PWM dimming signal d, that is, a 60 MHz clock, dimming in 100 steps is possible and fine dimming is possible.

  The frequency of each signal mentioned above is only an example. However, both frequencies are values that can be realized at a reasonable cost using today's technology.

  As described above, according to 3 of the first embodiment, it is possible to simultaneously realize the improvement of the image quality and the improvement of the dimming function. Moreover, it is easier than individually adjusting the duty of the impulse signals i0 to i3 and the pseudo hold pulse signal h.

  FIG. 10 shows still another configuration example of the lighting signal generation circuit 10a shown in FIG. The difference from FIG. 7 is that a logic gate 212 is added between the input terminal 101 of the vertical synchronization signal vs and the coincidence comparator 204 and the counter 202p. With this change, the counter 202p is cleared by both the pulse of the vertical synchronization signal vs and the output of the coincidence comparator 204. In FIG. 8, the same reference numerals are assigned to members having the same functions and configurations as those in FIG.

  The signal polarity does not limit the present invention. An appropriate logic gate 212 may be selected in accordance with the polarity of each signal.

  In 4 of the first embodiment, the counter 202p is cleared in synchronization with the pulse of the vertical synchronization signal vs. This facilitates circuit debugging. Further, it is possible to reduce the labor required for creating a pattern (test bench) used in IC shipping inspection. Further, even if the lighting signal generation circuit 10a malfunctions due to an instantaneous power failure or the like, the normal operation can be reliably restored within one frame. Thereby, the time for which the viewer waits until the normal operation is restored after the malfunction occurs is reduced.

  In the fourth embodiment, if the period of the pseudo hold pulse signal h is sufficiently short with respect to the vertical period, the influence of the insertion of the logic gate 212 on the image quality can be substantially ignored. If the frequency at which the coincidence comparator 204 outputs pulses is sufficiently higher than the pulse frequency (= vertical frequency) of the vertical synchronization signal vs, 2 in FIG. 1 (FIG. 7) and 4 in FIG. 1 (FIG. 10) There is almost no difference in image quality.

  FIG. 11 shows still another configuration example (referred to as “5 of Example 1”) of the lighting signal generation circuit 10a of FIG. This is obtained by replacing the delay circuit 108 (see FIG. 7) according to 2 of the first embodiment with an adder 113. Further, in the lighting signal generation circuit 10a according to 5 of the first embodiment, the counter 102 is one regardless of the number of systems (the number of circuit blocks 109). The function and output waveform of the lighting signal generation circuit 10a according to 5 of the first embodiment are the same as those of the lighting signal generation circuit 10a according to 2 of the first embodiment.

  If the configuration of Example 5 is adopted, for example, when the delay time is a constant, the number of the counters 102 is only one, so that the circuit scale can be reduced from FIG.

  As described above, according to the first invention, it is possible to reduce flicker while suppressing interference with the outline of a moving image. If flicker can be reduced, one of the barriers that hinder the increase in size and brightness of the display device is eliminated. In addition, according to the first aspect of the present invention, there is little increase in cost associated with realizing flicker reduction. Although the scale of the signal circuit is slightly increased, the conventional large members and power circuits can be used almost as they are. In addition, taking advantage of Class D amplification, it is highly efficient. Further, the first invention does not hinder the mounting of the dimming function.

[Second invention]
The second invention relates to a light emission waveform adjusting method and a display device having an adjusting function for more effectively realizing the first invention.

  FIG. 12 shows the waveform of the light emission intensity of the display device according to the first configuration example (1 of Example 2) of the second invention. Waveforms (1) to (7) shown in FIG. 12 are examples of light emission waveforms that can be output by adjusting various setting values (parameters) held in the setting means 103r, 103f, 203, and 203f in FIG.

  Moreover, the hatched portions in the waveforms (2) to (7) in FIG. 12 are portions that emit light corresponding to the impulse signals i0 to i3. Also, the hatched portions in the waveforms (1) to (6) in FIG. 12 are portions that emit light corresponding to the pseudo hold pulse signal h.

  Here, the impulse signals i0 to i3 are generated in synchronization with the vertical synchronization signal vs, and have at most one pulse per frame. The frequency of the impulse signals i0 to i3 is about 60 Hz when displaying an NTSC video signal, for example.

  On the other hand, the pseudo hold pulse light emission signal h is emitted at a frequency exceeding the vertical frequency or the critical fusion frequency CFF, and may have two or more pulses per frame. Further, the pseudo hold pulse light emission signal h is not necessarily synchronized with the vertical synchronization signal vs.

  Further, the waveform (1) in FIG. 12 does not include any impulse light emission component, but includes only a pseudo hold pulse light emission component. In order to prevent flicker, the frequency of the pseudo hold pulse emission component may be set higher than the critical fusion frequency CFF. The image quality at that time is almost the same as that of the hold type light emitting display device shown in FIG. Note that lighting the lamp with this waveform (1) is a known technique.

  Furthermore, the waveform (7) in FIG. 12 does not include any pseudo hold pulse emission component. This is the same as the impulse-type light emission waveform described in Non-Patent Document 1 and the like. That is, it is also well known that the lamp is turned on using the waveform (7).

  Then, from the waveform (1) to the waveform (7) in FIG. 12, the light emission time of the impulse component gradually increases, that is, the pulse becomes thicker, and the number of pseudo hold pulses decreases. Of these, the waveform (1) in FIG. 12 is optimal for displaying a still image, and the waveform (7) is optimal for displaying a moving image. However, still images and moving images are mixed in general video signals. Therefore, a preferable waveform may be selected between the waveform (1) and the waveform (7).

  That is, in the display device according to the second invention, the designer of the display device, the production personnel, the installation contractor, or the viewer can select the display device shown in FIG. 12 according to the use, the source of the video signal, the viewer's preference, or the like. An appropriate waveform can be selected between the waveform (1) and the waveform (7). In particular, 1 of the second embodiment is to adjust the width of the impulse component and the number of pseudo hold pulse components. That is, in 1 of Example 2, while fixing the light emission time (pulse width) of the pseudo hold pulse light emission component, the frequency (frequency of light emission) of the pseudo hold pulse component is adjusted. As the image quality adjustment means for such adjustment, a DIP switch, a variable resistance knob, an infrared remote controller, or other configurations can be employed.

  Further, a desired light emission waveform may be selected for each input terminal of the video signal. For example, while the video input from the RCA connector is displayed based on the light emission waveform (6) of FIG. 12, the video input from the high-density D-SUB 15 pin (hereinafter referred to as D-SUB) connector is displayed. ) May be displayed based on. This is because the RCA connector often connects video sources with many moving images such as VCRs, DVD players, and game machines, and the D-SUB connector often connects video sources with many still images such as PCs. is there.

  Here, when the viewer switches the video input from the RCA input to the D-SUB input, if the light emission waveform is instantaneously switched from the waveform (6) to the waveform (2), the image quality may suddenly change and the viewer may be confused. There is. Therefore, if the light emission waveform (6) → (5) → (4) → (3) → (2) is gradually switched, it is not necessary for the viewer to notice that the light emission waveform has been switched.

  Also, if the light emission waveform is suddenly switched from the waveform (1) to the waveform (7) (or vice versa), the image quality suddenly changes, which may surprise the viewer. According to the second invention, the intermediate state between the waveform (1) and the waveform (7), that is, the waveform (2) to the waveform (6) are sequentially output, so that the picture quality suddenly changes and the viewer is You can eliminate the fear of surprise.

  FIG. 13 is a diagram showing a light emission waveform of the display device according to the second configuration example (referred to as “second example 2”) of the second invention. In Example 2 described above, the light emission waveform and the image quality are adjusted by changing the number of pseudo hold pulses per frame (see FIG. 12). On the other hand, the second example 2 adjusts the light emission waveform and the image quality by adjusting the duty of the pseudo hold pulse. That is, in Example 2-2, the frequency of the pseudo hold pulse component (light emission frequency) is fixed, while the light emission time (pulse width) of the pseudo hold pulse component is adjusted. Other than that, the same configuration as 1 in the second embodiment is also adopted in the second embodiment.

  In Example 2 (FIG. 12), since it is not necessary to output an extremely thin pulse, it is easy to take measures against switching noise. On the other hand, in the second example 2 (FIG. 13), since it is not necessary to change the frequency of the pseudo hold pulse, it is easy to take measures against beats due to interference with the horizontal scanning frequency. Which one of the first embodiment 2 and the second embodiment 2 is employed is within the discretion of the designer.

  According to the second aspect of the present invention, the image quality can be adjusted more finely than before according to the use of the display device, the source of the video signal, the preference of the viewer, and the like. In addition, the light emission waveform, for example, the waveform (1) to the waveform (7) (see FIG. 12 or FIG. 13) can be switched smoothly only by controlling the switch 11 (FIG. 1) of one kind of lamp 8i (FIG. 1). Can do.

[Third invention]
A third invention according to the present application will be described with reference to FIGS.

  1 and the display device of FIG. 35 (conventional example) have the same luminance specification value, the average power capacity of the power supply circuit 7 of FIG. 1 and FIG. 35 is the same. Good. However, in the first invention, there are moments when the switches 11 of all systems are turned on at the same time, all the lamps 8i are turned on simultaneously, and all the regions L0 to L3 of the light guide plate 9a emit light. In this case, the instantaneous maximum power capacity of the power supply circuit 7 of FIG. 1 exceeds that of the power supply circuit 7 of FIG. This is because even if the average value of the load (power consumption of the lamp) is the same, the instantaneous value is exceeded. Also, the rated performance of the power supply circuit is directly related to the cost increase unlike the gate scale of the digital circuit.

  In general, a power circuit requires more time and effort to verify safety and reliability than a signal processing circuit, particularly a digital signal processing circuit. For this reason, in order to put a product in a market with a short product life, it is a customary practice to customize only software and digital circuits, and to use general-purpose circuits whose operation has been verified for analog circuits and power circuits. Moreover, if a design change is made unnecessarily, there is a risk of losing business opportunities and holding inventory.

  The third invention has been made in view of the above problems. That is, the third aspect of the invention aims to suppress the cost increase around the power supply circuit.

  According to a third aspect of the present invention, in a display device in which the lamp is divided into a plurality of systems and each circuit system can be controlled individually, the light emission timing of the pseudo hold pulse signal h is shifted for each system. is there.

  FIG. 14 is a block diagram showing a configuration of an LCD according to the third invention. As shown in FIG. 14, the LCD according to the third invention is obtained by replacing the lighting signal generation circuit 10a (FIG. 1) according to the first invention with a lighting signal generation circuit 10b. In FIG. 14, members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals.

  FIG. 15 is a diagram showing a configuration example (referred to as “1 of Example 3”) of the lighting signal generation circuit 10b of FIG. In FIG. 15, the operations of the members denoted by reference numerals 101, 102, 103r, 103f, 104r, 104f, 105, 107, 108, 109 are the same as the operations of the members denoted by the same numbers in FIG. The same. These generate impulse signals i0 to i3 synchronized with the vertical synchronization signal vs.

  As shown in FIG. 15, the lighting signal generation circuit 10b includes a counter 202p, setting means 203, coincidence comparators 203f, 204, and 204f, and an SR flip-flop 205, and the number of members constituting the circuit is the same. More than the lighting signal generation circuit 10a shown in FIG. However, the operation and function of the lighting signal generation circuit 10b are the same as those of the lighting signal generation circuit 10b of FIG. These generate a pseudo hold pulse signal having a frequency higher than the critical fusion frequency CFF.

  Hereinafter, the lighting signal generation circuit 10b according to the third invention will be described more specifically. As shown in FIG. 15, the lighting signal generation circuit 10 b includes a time difference setting unit 207 and a delay circuit 208. In FIG. 15, the same circuit block 209 is indicated by a dotted line. Further, the lighting signal generation circuit 10b includes OR gates 110, and output terminals 106 for the lighting signals p0 to p3.

  The time difference setting means 207 holds the deviation of the light emission time between the pseudo hold pulse systems. The setting means 107 holds one-quarter time of one frame. However, in the third invention, the setting means 107 does not necessarily have to be a quarter of the period of the pseudo hold pulse. For example, it may be 3/4.

  Further, the lighting signal generation circuit 10b according to 1 of the third embodiment has four circuit blocks 209. Each of the four system circuit blocks 209 operates simultaneously while maintaining a predetermined time difference by the time difference setting means 207 and the delay circuit 208. For this reason, four pseudo hold pulse signals h0 to h3 having a phase shift for each system can be generated. This is the difference between the third invention (see FIG. 15) and the first invention (see FIG. 7).

  Each of the OR gates 110 performs a logical sum of the impulse signals i0 to i3 synchronized with the vertical synchronization signal vs and the pseudo hold pulse signals h0 to h3, and outputs the lighting signals p0 to p3. Output to each of. The purpose of synthesizing the impulse signal and the pseudo hold pulse signal is the same as that of the first invention (FIG. 7).

  FIG. 16 is a diagram illustrating waveforms of the vertical synchronization signal vs, the impulse signals i0 to i3, the pseudo hold pulse signals h0 to h3, and the lamp lighting signals p0 to p3. In FIG. 16, waveforms are represented by the same method as in FIG. Note that the number of pseudo hold pulse signals has increased with the use of the lighting signal generation circuit 10b according to the third invention.

  FIG. 17 is a diagram illustrating a light emission waveform of the regions L0 to L3 (see FIG. 14) of the light guide plate 9a and a waveform of the power P flowing from the light emission power input terminal 6 to the power supply circuit 7. Note that FIG. 17 shows the light emission waveform and the power by the same notation as in FIG. In FIG. 17, the portion hatched with thick lines is the portion emitting light corresponding to the impulse signals i0 to i3, and the portion hatched with thin lines corresponds to the pseudo hold pulse signals h0 to h3. This is the part that emits light.

  When the total lighting power P in FIG. 17 is compared with the total lighting power P in FIG. 4, the instantaneous maximum power consumption is reduced from 8.0 to 6.0. This is because the switches 11 (see FIG. 1 and FIG. 14) that conduct simultaneously are reduced from four systems to three systems. Accordingly, the maximum value of the number of lamps that are turned on at the same time is reduced from eight to six.

  As described above, according to the third invention, the total lighting power P can be reduced as compared with the first invention. Therefore, the power supply circuit 7 (FIG. 14) is lower in performance than the power supply circuit used in the first invention. A power supply circuit that is sufficient, small and inexpensive can be employed. This is an effect obtained by adopting the third invention, that is, the lighting signal generation circuit 10b.

  FIG. 18 is a diagram for explaining the effect of the third invention. That is, according to the third invention, there is an effect that not only the instantaneous maximum power consumption but also harmonics flowing in the power supply circuit can be reduced. More specific description will be given below.

  The part (I) in FIG. 18 has the same waveform as the total lighting power P (see FIG. 4) in the first invention. The part (II) in FIG. 18 has the same waveform as the total lighting power P (see FIG. 17) in the third invention. Furthermore, the (III) part of FIG. 18 is a figure which shows the result of having calculated the harmonic component regarding the waveform shown to the (I) part, and the waveform shown to the (II) part.

  Unlike the calculation result of FIG. 6, in the calculation result shown in part (III) of FIG. 18, attention should be paid to higher-order harmonics. That is, it can be seen that the harmonics of 2.667 at the maximum in the first invention are reduced to 1.106 at the maximum of the third invention. From this, it can be seen that if the third invention is applied, higher harmonics flowing in the power supply circuit can be suppressed than the first invention.

  If the harmonics flowing through the power supply circuit 7 (see FIG. 14) are reduced, noise is reduced, and other circuits are less likely to malfunction. For example, the noise picked up by the TV tuner is reduced, and the display quality is improved. In addition, the ripple current flowing in an electrolytic capacitor (not shown), which is an indispensable component of the power supply circuit, is reduced, and heat generation in the capacitor is reduced, so that the life of the power supply circuit is extended.

  In particular, when an LED is used for the lamp 8i in FIG. 14, the life of the power supply circuit 7 becomes a serious problem. This is because the lifetime of an LED is generally longer than that of an incandescent lamp or a fluorescent lamp, and the commercial value is impaired if the lifetime of the power supply circuit is exhausted before the LED. Therefore, it is particularly effective to apply the third invention to extend the life of the power supply circuit 7 when an LED is used as the lamp 8i.

  In addition, in order to shift the light emission timing based on the impulse synchronized with the vertical synchronization signal vs in accordance with the scanning of the gate line, in the conventional example (see FIG. 35), the lamp lighting circuit is divided into a plurality of systems. And according to 3rd invention (refer FIG. 14), the cost increase from a prior art example (FIG. 35) can be only small by using a conventional circuit structure as it is, and making it a lighting circuit.

  Further, when a DC / DC converter is employed in the power supply circuit 7 (FIG. 14), that is, when the third invention and the DC / DC converter are combined, the following effects are produced.

  Again, the total lighting power P in FIG. 17 is compared with the total lighting power P in FIG. In either case, the instantaneous minimum power consumption is 2.0. However, in the former case (third invention), the power is minimized for a moment. On the other hand, in the latter (first invention), the state in which the power is minimized continues for a longer time. This means that when the power supply circuit whose efficiency is reduced when the load becomes smaller than the rating, that is, the DC / DC converter is adopted, the former can realize power saving than the latter.

  In addition, when the load is extremely reduced, the DC / DC converter may stop switching and malfunction. This phenomenon will be described with reference to FIGS. FIG. 19 is a diagram showing the luminance of the regions L0 to L3 and the waveform of the total lighting power P when only the first invention is applied. FIG. 20 is a diagram showing the luminance of the regions L0 to L3 and the waveform of the total lighting power P when the third invention is applied in addition to the first invention. When detecting the waveforms of FIGS. 19 and 20, the lighting signal generating circuit 10b is operated with a smaller duty than when detecting the waveforms of FIGS.

  The total lighting power P is the total power consumed in the areas L0 to L3. Further, the average value of the total lighting power P in FIG. 19 and the average value of the total lighting power P in FIG. 20 are described to be equal.

  As can be seen by referring to the waveform of the total lighting power P in FIG. 19, the waveform has a time during which all the regions L0 to L3 are turned off simultaneously. That is, the power load is intermittently interrupted. On the other hand, as can be seen by referring to the waveform of the total lighting power P in FIG. 20, when the lighting signal generation circuit 10b according to the third invention is used, one of the regions L0 to L3 is always lit. That is, there is always a power load.

  As described above, according to the third aspect of the invention, it is possible to avoid or reduce the influence that all the systems are turned off simultaneously, so that the power supply circuit can be operated stably. Furthermore, since the backlight can be operated even at a low load, the dimming range of the backlight can be expanded.

  FIG. 21 is a diagram illustrating another configuration example (referred to as “second example 3”) related to the lighting signal generation circuit 10b of FIG. The difference between the lighting signal generation circuit 10b in FIG. 21 and the lighting signal generation circuit 10b in FIG. 15 is that the number of pseudo hold pulse generation circuits 209 in FIG. 21 is smaller than the number of impulse light emitting circuits 109 in FIG. There is in point. That is, in the lighting signal generation circuit 10b of FIG. 21, there are two systems (h0 and h1) of the pseudo hold pulse generation circuit 209, while there are four systems (i0 to i3) of the impulse light emitting circuit 109.

  The pseudo hold pulse signal h0 is combined with the impulse signals i1 and i3, and the pseudo hold pulse signal h1 is combined with the impulse signals i0 and i2 by the OR gate 110. In FIG. 21, members having the same functions and configurations as the members in FIG. 15 are denoted by the same reference numerals.

  Also by the lighting signal generation circuit 10b of FIG. 21, a time difference is given to the light emission times of the pseudo hold pulse signals h0 and h1. In addition, the gate scale can be reduced to the extent that the number of circuit blocks 209 is smaller than that of the circuit of FIG. 15 (1 of the third embodiment). Further, as the number of systems of the impulse light emitting circuit 109, that is, (the number of divisions of the light guide plate 9a (FIG. 14)) increases, the effect of reducing the gate scale increases.

  Therefore, according to Example 3-2, although the effect of reducing the number of systems that are turned on or off at the same time or suppressing harmonics flowing through the power supply circuit is somewhat reduced, the number of divisions of the light guide plate 9a is large. In this case, since the effect of reducing the gate scale is increased, the second embodiment of the third embodiment is more practical than the first embodiment.

  Whether to select 1 of Example 3 or 2 of Example 3 may be determined after considering the gate size of the lighting signal generation circuit 10b, the instantaneous maximum rating of the power supply circuit 7, and other factors.

  As described above, according to the third aspect of the invention, it is possible to reduce the instantaneous maximum rating of the power supply circuit and reduce the harmonics accompanying the switching operation. In addition, there is an effect that the power supply circuit for lighting the lamp can be stably operated. Moreover, the cost increase associated with obtaining these effects is small.

[Fourth Invention]
A fourth invention according to the present application will be described with reference to FIGS.

  According to 1 of Embodiment 3 of the third invention (see FIG. 15), in the lighting signal generation circuit 10b of FIG. 14, the switches 11 exceeding three systems are not simultaneously turned on by design. However, it is impossible to design a product without considering the malfunction of the circuit.

  That is, when the display device is a TV, the moment when the channel is switched or when the radio wave condition is bad, when the display device is a PC display, the resolution is changed, and when the display device is a mobile device display, immediately before the battery runs out The synchronization signal vs may be disturbed, and the display device may operate unexpectedly. At the moment when such a malfunction occurs, many of the switches 11 in FIG. 14 are turned on, and a large load may be applied to the power supply circuit 7. Moreover, the frequency with which the power supply circuit 7 malfunctions is not so low even under normal usage conditions.

  Also, a lamp with a large instantaneous maximum rating is used for the impulse-type light emission backlight. For example, as can be seen by comparing portion A in FIG. 34 with portion A in FIG. 40, the instantaneous luminance of the impulse-type light emission backlight is larger than the instantaneous luminance of the hold-type light emission backlight. In this example, it reaches twice. If the light emission time of the backlight is limited to be short by adopting impulse light emission, it is necessary to increase the instantaneous luminance in order to maintain the average luminance.

  For the above reasons, if the lighting signal generation circuit 10b in FIG. 14 malfunctions and all the lamps are turned on simultaneously for one frame or more, the viewer is exposed to a powerful flash, although instantaneously. It makes viewers feel unpleasant.

  The fourth invention has been made in view of the above problems. That is, it relates to a countermeasure against malfunction of the circuit of the third invention.

  That is, according to the fourth aspect of the present invention, the number of switches that are in a conductive state is counted before actually causing the lamp to emit light, and if the number is not within a predetermined allowable range, the light emission is forcibly stopped to be inappropriate. This prevents the light from being emitted. Hereinafter, the fourth invention will be described more specifically.

FIG. 22 is a block diagram showing a configuration of an LCD according to the fourth invention. As shown in FIG. 22, the LCD according to the fourth invention is provided with a protection circuit 12 between the lighting signal generation circuit 10 b and the switch 11. In this respect, the LCD according to the fourth invention is different from the LCD according to the third invention. In FIG. 22, members having the same functions and configurations as those in FIG. 14 are given the same reference numerals. The lighting signal generation circuit 10 b in FIG. 22 converts the provisional lighting signals p0 to p3 to the protection circuit 12. Output to. The protection circuit 12 monitors the temporary lighting signals p0 to p3, and after confirming that there is no abnormality, outputs the valid lighting signals q0 to q3 to the switch 11.

  FIG. 23 is a block diagram illustrating a configuration example of the protection circuit 12 (referred to as “1 of Example 4”).

  As shown in FIG. 23, the protection circuit 12 includes an input terminal 401 for temporary lighting signals p0 to p3, a half adder (HA) 402, a full adder 403, a dummy , A setting unit 405 for the number of systems that can emit light simultaneously, a magnitude comparator 406, an AND gate 407, and an output terminal 408 for an effective lighting signal.

  The half adder 402 and the full adder 403 count the number of systems that are turned on simultaneously, in other words, the number of switches 11 (FIG. 22) that are simultaneously turned on. The buffer 404 is a dummy for changing the signal name, and may be omitted in an actual circuit.

  The setting means 405 holds the number of systems that can emit light simultaneously. For example, referring to the waveform of the total lighting power P in FIG. 17, a maximum of three systems emit light at the same time. Therefore, when adopting this light emission waveform, if “3” is held in the setting means 405 as the number of systems. Good.

  The size comparator 406 determines that the value 1 is AND gate 407 if the number A [2: 0] of systems that are simultaneously turned on is equal to or less than the number of systems that can emit light simultaneously (allowable value) B [2: 0] = 3. If not, the value 0 is output. The AND gate 407 calculates the logical product of the provisional lighting signals p0 to p3 and the output value of the magnitude comparator 406, and outputs valid lighting signals q0 to q3 to the output terminal 408.

  Thus, in the fourth aspect of the invention, instead of calculating the total sum of the power consumption values (continuous analog quantities) of each lamp, the number of lighting systems is counted. Therefore, the protection circuit 12 can be realized with a digital circuit having a small number of bits. For example, the accuracy of the magnitude comparator 406 in FIG. 23 is only 3 bits.

  In general, the smaller the protection circuit, the better. This is because the possibility of not operating due to a bug, noise, failure, etc. is reduced. Further, the fourth aspect of the invention is the maximum use of the fact that the lamp 8i (FIG. 14) is dimmed by class D amplification using the switch 11 (FIG. 14) in the third aspect of the invention. I can say that.

  The configuration and operation of the protection circuit 12 according to 1 of Example 4 are as described above. Therefore, if the number of systems that are turned on simultaneously does not exceed the allowable value, the provisional lighting signals p0 to p3 are output as valid lighting signals q0 to q3 as they are. In this case, the LCD of the fourth invention appears to be operating in the same manner as the LCD of the third invention.

  On the other hand, if the number of systems that are simultaneously turned on exceeds the allowable value, the lamp 8i (FIG. 22) is forcibly turned off. This is the effect of providing the protection circuit 12 according to the fourth invention.

  Further, the circuit example of the protection circuit 12 according to 1 of the fourth embodiment, that is, the configuration of FIG. 23 is not optimized. For this reason, even if the number of systems is not four, if the logic is changed with reference to FIG. 23, the prototype of the present invention can be easily made. Actually, optimization should be performed after the logic design is completed. If optimized, the circuit scale is reduced, which not only leads to cost reduction, but also reduces the probability that the protection circuit itself malfunctions or fails. In addition, since a well-known technique can be used for optimization, detailed description about the circuit which optimized FIG. 23 is abbreviate | omitted.

  In the present invention, the logic in the control circuit is not an essential part. For example, instead of the number of systems that are turned on, the number of systems that are turned off may be counted, and the control circuit may be designed to stop the lighting of the lamp if it does not exceed a predetermined value. In that case, the logic is the reverse of FIG.

  In the present invention, the circuit mounting form is not an essential part. For example, FIG. 22 which is a block diagram of the LCD according to the fourth invention does not mean that the control circuit 2, the lighting signal generation circuit 10b, and the protection circuit 12 are separately mounted in different IC packages. Since these circuits can all be realized by digital circuits, it is easy to realize them by one IC.

  FIG. 24 is a block diagram showing still another configuration example of the protection circuit 12 (referred to as “second example 4”).

  As illustrated in FIG. 24, the protection circuit 12 according to the second embodiment includes an AND gate 407a and a logic gate 407b including an inverter and an OR gate. In FIG. 24, the same reference numerals are assigned to members having the same functions and configurations as those in FIG.

  In the protection circuit 12 according to 2 of Example 4, the provisional lighting signals p0 to p3 are output as valid lighting signals q0 to q3 as they are unless the number of systems that are simultaneously turned on exceeds the allowable value. . This is the same as 1 in the fourth embodiment.

  On the other hand, if the number of systems that are turned on simultaneously exceeds the allowable value, the effective lighting signals q0 and q3 are forcibly set to the low level, and the lighting signals q1 and q2 are forcibly set to the high level. As a result, two of the four systems are forcibly turned off and the remaining two systems are forcibly turned on. It should be noted that the number of systems that are forcibly turned on needs to be equal to or less than an allowable value.

  Therefore, when the switching operation of the power supply circuit 7 (see FIG. 22) becomes unstable due to the forced turn-off of all the lamps 8i (see FIG. 22) according to 1 of the fourth embodiment, the embodiment The protection circuit 12 according to 4-2 is superior. This is because, according to the protection circuit 12 according to 2 of the fourth embodiment, when the number of systems that are turned on at the same time exceeds the allowable value, some lamps are forced to be turned off without turning off all the lamps. It is because it is made to light.

  Also in Example 4-2, it is not an essential part of the protection circuit 12 whether positive logic or negative logic is adopted. That is, the number of systems that are turned on or the number of systems that are turned off may be counted.

  In addition, as shown in FIG. 25, the protection circuit 12 can be applied to the LCD including the lighting signal generation circuit 10. The LCD shown in FIG. 25 is obtained by replacing the lighting signal generation circuit 10b with the lighting signal generation circuit 10 in the LCD shown in FIG. Other than that, there is no difference.

  In other words, the protection circuit 12 according to the fourth invention can be applied to the lighting signal generation circuit 10 (see FIGS. 35 and 36). Therefore, the lighting signal generation circuit 10 itself is outside the scope of the present invention, but an LCD including the protection circuit 12 is included in the present invention.

  Note that the lighting signal generation circuit 10 can be easily prototyped by referring to the description in the “Background Art” column, and the protection circuit 12 can be obtained by referring to Example 4 1 or Example 4-2. Can be easily prototyped.

  As described above, when the protection circuit of the fourth invention is applied to the third invention or the conventional example, even if the circuit malfunctions, it is possible to prevent an accident in which a large number of lamps exceeding the allowable limit emit light simultaneously. Further, since the scale of the logic circuit added by the fourth invention is not large, low cost and high reliability can be obtained.

[Fifth Invention]
A fifth invention according to this application will be described with reference to FIGS.

  FIG. 26 is a block diagram showing an example of the configuration of an LCD according to the fifth aspect of the invention (referred to as “1 of Example 5”). In Example 1 of Example 5, as shown in FIG. 26, current limiting elements 13 are provided between the switches 11 and the lamp 8i. In FIG. 26, members having the same functions and configurations as those in FIG.

  The current limiting element 13 can be configured by combining, for example, an inductor or a capacitor that consumes only reactive power. Since the present invention employs intermittent pulsed light emission, it is not necessary to limit the current with a resistor that consumes active power.

  For example, an incandescent lamp or a halogen lamp has an excessive inrush current when it is lit. However, the current limiting element 13 can prevent a failure of the power supply circuit 7 due to the inrush current. Furthermore, the current limiting element 13 has the effect of consuming reactive power and preventing smoke and fire of the power line in the event of a short circuit accident due to a lamp failure, mounting failure, or the like.

  Further, the role of the current limiting element 13 is not to block harmonics, unlike the LC passive filter provided in the class D amplifier circuit. In the first place, since the frequency of the pseudo hold pulse exceeds CFF, it is not necessary to smooth the lighting waveform. In other words, the lighting waveform is smoothed on the human retina without the circuit smoothing the waveform.

  In addition, if the harmonics of the impulse waveform synchronized with the vertical synchronization signal are removed more than necessary, the effect of improving the quality of the moving image of the impulse light emission is reduced. In this sense, the present invention is different from a simple class D amplifier circuit.

  FIG. 27 shows another example of the LCD according to the fifth invention (referred to as “Example 5-2”). In the fifth invention, a current limiting element 13 is inserted between the switches 11... And the power supply circuit 7 as shown in FIG. That is, the LCD shown in FIG. 27 differs from the LCD shown in FIG. 26 only in that the order of the switch 11 and the current limiting element 13 is changed.

  In the LCD according to the fifth invention, the type of the lighting signal generation circuit is not limited. That is, as the lighting signal generation circuit, the one shown in FIG. 26, the one shown in FIG. 35, or the one shown in FIG. 36 may be used. Further, the protection circuit 12 (FIG. 26) is not necessarily provided.

  As described above, according to the fifth aspect, the inrush current flowing through the lamp can be reduced, and the power line can be protected from a short circuit accident.

[Sixth Invention]
A sixth invention according to the present application will be described with reference to FIGS.

  When the application of the display device is an application with almost no opportunity to display a moving image, for example, when the display device is used for guidance display of various facilities, the impulse type light emission is harmful and useless. The sixth invention relates to a display device suitable for such a use.

  FIG. 28 is a block diagram showing a structural example (referred to as “1 of Example 6”) of the LCD according to the sixth invention.

  The configuration of the LCD according to 1 of Example 6 will be described focusing on the difference from the configuration of the LCD according to the fourth invention (FIG. 22). In the LCD according to 1 of Example 6, the lighting signal generation circuit 10b is replaced with the lighting signal generation circuit 10c, and the vertical synchronization signal vs is not output from the control circuit 2 to the lighting signal generation circuit 10c. The light guide plate 9 is not divided into regions L0 to L3.

  Along with this, the degree of freedom further increases with respect to the connection form between the switch 11 and the lamp 8i. For example, the switch 11 at the top of the drawing need not control the lamp at the top of the light guide plate 9. That is, as shown in FIG. 28, the signal line p0 may control the lamps 8i that are first and fifth from the top. In FIG. 28, members having the same functions and configurations as those in FIG. 22 are denoted by the same reference numerals.

  FIG. 29 is a block diagram showing a configuration of a lighting signal generation circuit 10c provided in the LCD of FIG. The configuration of the lighting signal generation circuit 10c shown in FIG. 29 will be described focusing on the differences from the configuration of the lighting signal generation circuit 10b (see FIG. 15) according to the third invention.

  29, the lighting signal generation circuit 10c includes a counter 202p..., A count cycle and lighting time setting unit 203, a turn-off time setting unit 203f, coincidence comparators 204... 204f. 205, time difference setting means 207, and delay circuits 208. In FIG. 29, the same circuit block 209 is indicated by a dotted line. Further, the lighting signal generating circuit 10c includes output terminals 106 for temporary lighting signals p0 to p3.

  The operation of the above circuit is the same as that of the generation circuit (see FIG. 15) of the pseudo hold pulses h0 to h3 according to the third invention. The temporary lighting signals p0 to p3 must be set higher than the critical fusion frequency CFF. The setting method is the same as in the third invention.

  That is, the lighting signal generation circuit 10c according to the sixth aspect of the present invention has the function of generating an impulse component synchronized with the vertical synchronization signal vs, except that the lighting signal generation circuit 10b according to the third aspect of the present invention (FIG. 15). The operation is the same as (see).

  Further, according to the sixth aspect, there are a plurality of pseudo hold pulse generation circuits 209, and the light emission timing of each system is shifted by the delay circuit 208 by a predetermined time difference. For this reason, since the peak of lighting power is distributed, the rating of the power supply circuit 7 can be lowered. Furthermore, harmonics flowing through the power supply circuit are also reduced.

  Further, according to 1 of Example 6, since the protection circuit 12 is provided, even if the lighting signal generation circuit 10c malfunctions, no electrical shock is applied to the power supply circuit.

  In Example 1 of Example 6, it does not matter whether positive logic or negative logic is adopted in the lighting signal generation circuit 10c. That is, the number of systems that are turned on may be counted, or the number of systems that are turned off may be counted.

  Further, in Example 1 of Example 6, if the power consumption before and after the turn-off falls within the power capacity of the power supply circuit 7, the forcibly turned off system may be part of the power It may be a system.

  FIG. 30 is a block diagram showing another configuration example of the LCD according to the sixth invention (referred to as “Example 6-2”).

  As shown in FIG. 30, the protection circuit 12 is omitted in the LCD according to 2 of Example 6. Therefore, the lighting signals p0 to p3 are input directly to the switches 11... Without going through the protection circuit. The other functions and operations of the lighting signal generation circuit 10c are the same as those in the first embodiment.

  In the first place, LCD has appeared as a portable display device for so-called mobile devices. In such applications, motion blur is not currently a problem. Therefore, an impulse component synchronized with the vertical synchronization signal vs is not necessary for the LCD.

  Further, the output of the lamp 8i is lower than that of the stationary display device, and the number of the lamps 8i is smaller. For this reason, there is no problem even if the power supply circuit 7 has a performance capable of lighting all the lamps 8i with a duty of 100%. In this case, the protection circuit 12 can be omitted as in Example 6-2.

  Whether to adopt 1 of Example 6 or 2 of Example 6 may be determined in consideration of the application of the LCD.

  By the way, in mobile devices, a DC / DC converter (switching regulator) is often used rather than a linear regulator (series regulator) in order to extend the battery driving time.

  When the power load of the DC / DC converter is smaller than the rating, the battery utilization efficiency is lowered. That is, it is easier to increase the power conversion efficiency when there is less fluctuation in the power load. This is because the DC / DC converter can be configured in accordance with the size of the power load under typical use conditions. This means that if the power load is distributed and averaged according to the sixth aspect of the invention, power saving can be achieved.

  Further, the DC / DC converter may even malfunction when the power load is extremely reduced. This is because the switching operation of the DC / DC converter stops when there is no power load.

  FIG. 31 is an operation waveform of the conventional PWM dimming. In FIG. 31, p0 to p3 are light emission waveforms of each system, and P is the total lighting power of all systems. Referring to the waveform of the total lighting power P in FIG. 31, it can be seen that the load is frequently lost. This may cause the operation of the DC / DC converter to become unstable. If the power supply circuit becomes unstable, noise is added to the video signal, and so-called SNR (ratio of signal to noise power) is reduced.

  On the other hand, FIG. 32 shows operation waveforms of the LCD according to the sixth invention. The meaning of each graph in FIG. 32 is the same as that in FIG. As can be seen by referring to the waveform of the total lighting power P in FIG. 32, there is no moment when the load is completely absent. For this reason, the operation of the DC / DC converter is more stable than in the conventional example (FIG. 31).

  As described above, according to the sixth aspect, by dispersing the peak of the total lighting power, the harmonics of the current flowing through the power supply circuit 7 can be reduced and the load current can be made uniform. According to the present invention, a highly efficient power supply circuit can be easily designed. In addition, the operation of the power supply circuit can be stabilized.

[Configuration of liquid crystal display device]
Each time the fluorescent lamp is repeatedly turned on and off, the discharge electrode deteriorates and the life is shortened. Therefore, the lamp suitable for impulse light emission in the present invention includes a semiconductor light emitting element, for example, an LED.

  In order to implement the present invention, a non-light emitting panel in which a plurality of picture elements are formed is necessary. Currently, a liquid crystal panel is generally used as the panel. In particular, in the case of a direct-viewing type liquid crystal display device, it is easy to achieve high image quality if the transmissive liquid crystal panel is illuminated from behind. The active matrix liquid crystal display device is suitable for the present invention because it can perform analog multi-gradation display and each gate line is sequentially selected and scanned.

  As described above, according to the present invention, it is possible to improve the image quality of an active matrix transmission type liquid crystal display device.

  In the case of interlace (interlace) scanning, the frame may be replaced with a field. In a color LCD, three RGB liquid crystal cells may be regarded as one pixel (picture element). Further, a single impulse-type light emission may be narrowed down by high-frequency PWM dimming to form a plurality of light emission. Even if the impulse light emission is divided into a plurality of flashlights, there is only one impulse component.

  The image display device of the present invention includes an image display unit that modulates light based on a video signal, and a light source body that illuminates the image display unit, and the light source unit includes the video signal. The image display means is illuminated by light emission in which a pulse component (hereinafter referred to as pulse component i) emitted once per frame and a pulse component (hereinafter referred to as pulse component h) emitted at a frequency exceeding the frame frequency are mixed. It may be.

  The light emission time of the pulse component i may be longer than the light emission time of the pulse component h.

  Further, the light emission time of the pulse component h does not have to have a fixed relationship with the light emission time of the pulse component i.

  Further, the light emission frequency of the pulse component h may be two or more times per frame period.

  Further, the light emission frequency of the pulse component h may be higher than the critical fusion frequency.

  The light emission of the pulse component i and the light emission of the pulse component h may be performed by supplying the same power (work rate, energy per unit time) to the light source body.

  Further, the light emission of the pulse component i and the light emission of the pulse component h may be performed by the physically same light source.

  The pulse component i and the pulse component h may be mixed by a logic circuit.

  The pulse component i generating circuit and the pulse component h generating circuit are both constituted by digital circuits, and the bit width of the circuit for generating the latter pulse component h is a circuit for generating the former pulse component i. It may be smaller than the bit width.

  Further, a light source body having a light control function for intermittently emitting waveforms of the pulse component i and the pulse component h at a frequency sufficiently higher than the frequency of both pulse components may be provided in the image display device.

  The image display apparatus of the present invention may have a function of continuously adjusting the image quality by fixing the light emission time of the pulse component h and increasing or decreasing the light emission frequency.

  In addition, the image display device of the present invention may have a function of continuously adjusting the image quality by fixing the occurrence frequency of the pulse component h and increasing / decreasing the light emission time.

  The image display device of the present invention includes an image display unit that modulates light based on a video signal, and K (K ≧ 2, K is an integer) light source bodies that illuminate the image display unit. The K light source bodies have a light emission waveform obtained by mixing a pulse component i emitted once per frame of the video signal and a pulse component h emitted at a frequency exceeding the frame frequency. The image display means illuminates and is grouped into N (2 ≦ N ≦ K, where N is an integer) systems that can control light emission independently, and the light emission time of the pulse component i is N A configuration may be adopted in which each system is controlled according to the timing at which the video is scanned.

  Further, the light emission times of the pulse components h may be controlled so that the lighting times are distributed among the N systems.

  Further, the light emission times of the pulse component h may be controlled so that the lighting times are dispersed for each of M (2 ≦ M ≦ N ≦ K, M is an integer) systems.

  Further, in the image display device of the present invention, it is not necessary to have time for all the light source bodies to be turned on simultaneously while an effective video is displayed on the image display means.

  Further, in the image display device of the present invention, it is not necessary to have time to turn off all the light source bodies provided at the same time while an effective image is displayed on the image display means.

  The image display device of the present invention further includes a protection circuit between the generation circuit for the pulse component i and the pulse component h and a switch for controlling the light emission of the light source body, and the protection circuit includes the generation circuit. Among the output signals, the number of signals in the same logic state is counted, and the number is compared with a predetermined allowable value. If the number is not within the allowable range, some or all of the light source bodies are turned off. Good.

  The image display device of the present invention includes an image display unit that modulates light based on a video signal, and K (K ≧ 2, K is an integer) light source bodies that illuminate the image display unit. The K light source bodies are image display devices that illuminate the video display means with a light emission waveform composed of a pulse component i emitted once per frame of the video signal. The light source bodies are grouped into N systems (2 ≦ N ≦ K, where N is an integer) that can control light emission independently, and the light emission time of the pulse component i is displayed for each of the N systems. A protection circuit is provided between the pulse component i generation circuit and a switch for controlling the light emission of the light source body, which is controlled according to the scanning timing, and the protection circuit includes, among the output signals of the generation circuit, Count the number of signals in the same logic state It compares the number with a predetermined allowable value, not within the acceptable range, may be configured to turn off some or all of the light source.

  Furthermore, the image display device of the present invention may have a configuration in which a current limiting element is provided between a switch that controls lighting of the light source body and the light source body.

  Furthermore, the image display device of the present invention may have a configuration in which a current limiting element is provided between a switch that controls lighting of the light source body and a power source that supplies lighting power of the light source body.

  Furthermore, the current limiting element may be a passive element that consumes reactive power.

  Furthermore, the image display device of the present invention includes an image display unit that modulates light based on a video signal, and K (K ≧ 2, K is an integer) light source bodies that illuminate the image display unit. The K light source bodies are configured to display the image display means with a light emission waveform composed of a pulse component h emitted at a frequency exceeding the frame frequency, and the light emission time of the pulse component h is N The configuration may be such that the lighting times are distributed among the individual systems.

  Furthermore, the image display device of the present invention includes a protection circuit between the generation circuit of the pulse component h and a switch that controls light emission of the light source body, and the protection circuit includes, among the output signals of the generation circuit, A configuration that counts the number of signals in the same logical state (the logic that indicates whether the light is on or off), compares that number with a predetermined tolerance, and turns off some or all of the light sources if they are not within the tolerance It may be.

  Furthermore, the image display apparatus of the present invention may have a configuration in which all the light source bodies included do not have time to be turned on simultaneously while an effective image is displayed on the image display means.

  Furthermore, the image display apparatus of the present invention may be configured such that all the light source bodies included therein do not have time to turn off simultaneously while a valid video is displayed on the image display means.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  According to the present invention, it is possible to improve the display quality of an image display device having a hold-type electro-optical conversion characteristic represented by a liquid crystal display device. Furthermore, it is possible to improve the tailing of moving images and reduce flicker interference.

It is a block diagram which shows one structural example of the image display apparatus which concerns on 1st invention. It is a block diagram which shows the structure of the lighting signal generation circuit which concerns on 1 of Example 1 of 1st invention. It is a figure which shows the operation | movement waveform of the lighting signal generation circuit which concerns on 1 of Example 1 of 1st invention. It is a figure which shows the light emission waveform and electric power waveform of the lamp | ramp which concern on Example 1 of 1st invention. It is a figure for qualitatively explaining that animation blur is improved by the 1st invention. It is a quantitative explanatory view of flicker of the image display device according to the first invention. It is a block diagram which shows the structure of the lighting signal generation circuit which concerns on 2 of Example 1 of 1st invention. It is a block diagram which shows the structure of the lighting signal generation circuit which concerns on 3 of Example 1 of 1st invention. It is a figure which shows the operation | movement waveform of the lighting signal generation circuit which concerns on 3 of Example 1 of 1st invention. It is a figure which shows the structure of the lighting signal generation circuit which concerns on 4 of Example 1 of 1st invention. It is a figure which shows the structure of the lighting signal generation circuit which concerns on 5 of Example 1 of 1st invention. It is a figure which shows the light emission waveform of the lamp | ramp which concerns on 1 of Example 2 of 2nd invention. It is a figure which shows the light emission waveform of the lamp | ramp which concerns on 2 of Example 2 of 2nd invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 3rd invention. It is a block diagram which shows the structure of the lighting signal generation circuit which concerns on 1 of Example 3 of 3rd invention. It is a figure which shows the operation | movement waveform of the lighting signal generation circuit which concerns on 1 of Example 3 of 3rd invention. It is a figure which shows the light emission waveform and electric power waveform of the lamp | ramp which concern on Example 3 of 3rd invention. It is a figure for demonstrating quantitatively the effect which concerns on 1 of Example 3 of 3rd invention. It is a figure which shows the light emission waveform and electric power waveform of a lamp | ramp at the time of restricting light control by applying 1st invention. It is a figure which shows the light emission waveform and electric power waveform of a lamp | ramp at the time of narrowing down light control by applying 3rd invention. It is a block diagram which shows the structure of the lighting signal generation circuit which concerns on 2 of Example 3 of 3rd invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 4th invention. It is a block diagram which shows the structure of the protection circuit which concerns on 1 of Example 4 of 4th invention. It is a block diagram which shows the structure of the protection circuit which concerns on 2 of Example 4 of 4th invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 3 of Example 4 of 4th invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 1 of Example 5 of 5th invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 2 of Example 5 of 5th invention. It is a block diagram which shows the structure of the image display apparatus which concerns on 1 of Example 6 of 6th invention. It is a block diagram which shows the structure of the lighting signal generation circuit based on 6th invention. It is a block diagram of the image display apparatus which concerns on 2 of Example 6 of 6th invention. It is a figure which shows the light emission waveform and electric power waveform of the lamp | ramp by the conventional PWM light control. It is a figure which shows the light emission waveform and electric power waveform of the lamp | ramp which concerns on 6th invention. It is a block diagram which shows the structure of the conventional hold | maintenance light emission display apparatus. It is a figure for qualitatively explaining the motion blur of the conventional hold type light emitting display device. It is a block diagram which shows the structure of the conventional impulse type light emission display apparatus. It is a block diagram which shows the structure of the lighting signal generation circuit of the conventional impulse type light emission display apparatus. It is a figure which shows the operation | movement waveform of the lighting signal generation circuit of the conventional impulse type light emission display apparatus. It is a figure which shows the light emission waveform of the lamp | ramp of the conventional impulse type light emission display apparatus. It is a figure for qualitatively explaining the motion blur of the conventional impulse light emitting display device. It is a figure for qualitatively explaining the motion blur of the impulse light emitting display device of Patent Document 3.

Explanation of symbols

5 Liquid crystal panel (image display means)
7 Power supply circuit 10, 10a, 10b, 10c (Pulse component i and pulse component h generating circuit)
8i lamp (light source)
11 switch 12 protection circuit 13 current limiting element 102 counter (circuit for generating pulse component i)
110 OR gate (a logic circuit that synthesizes a signal that generates a pulse component i and a signal that generates a pulse component h)
202p counter (circuit for generating pulse component h)

Claims (14)

In an image display device comprising image display means for modulating light based on a video signal and a light source body for illuminating the image display means,
The light source body illuminates the image display means with light in which a pulse component i emitted once per frame of the video signal and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The pulse component h is emitted at a frequency higher than the critical fusion frequency , and the light emission frequency is 6 times or more per frame period of the video signal,
There are K light sources (K ≧ 2, K is an integer), the K light sources illuminate the image display means,
The K light source bodies are grouped into N (2 ≦ N ≦ K, where N is an integer) systems whose light emission is controlled independently of each other, and one frame of the video signal is transmitted from each system. Illuminating the image display means by emitting light in which a pulse component i emitted once per pulse and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The light emission start time of the pulse component i is controlled for each of the N systems according to the timing at which the video is scanned in the image display means.
The pulse component h is, with respect to the N lines, the Rukoto is controlled so that the light emission start time are shifted from each other, said K of the light source emitting light of the pulse component h, with respect to the N lines, An image display device controlled to reduce the number of systems that are lit simultaneously . In an image display device comprising image display means for modulating light based on a video signal and a light source body for illuminating the image display means,
The light source body illuminates the image display means with light in which a pulse component i emitted once per frame of the video signal and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The pulse component h is emitted at a frequency higher than the critical fusion frequency , and the light emission frequency is 6 times or more per frame period of the video signal,
There are K light sources (K ≧ 2, K is an integer), the K light sources illuminate the image display means,
The K light source bodies are grouped into N (2 ≦ N ≦ K, where N is an integer) systems whose light emission is controlled independently of each other, and one frame of the video signal is transmitted from each system. Illuminating the image display means by emitting light in which a pulse component i emitted once per pulse and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The light emission start time of the pulse component i is controlled for each of the N systems according to the timing at which the video is scanned in the image display means.
The pulse component h is, M-number with respect to systems of (2 ≦ M ≦ N ≦ K , M are integers), the Rukoto is controlled such that the emission start time are shifted from each other, said K to emit light in the pulse component h The light source body is controlled so as to reduce the number of systems that are simultaneously turned on with respect to the M systems.   3. The image display device according to claim 1, wherein there is no time for all of the light source bodies to be turned on simultaneously while an image is displayed on the image display means.   3. The image display device according to claim 1, wherein there is no time for all of the light source bodies to be turned off simultaneously while a valid image is displayed on the image display device.   5. The image display device according to claim 1, further comprising a current limiting element between the switch for controlling lighting of the light source body and the light source body. 6.   The current limiting element is provided between the switch for controlling the lighting of the light source body and a power supply circuit for supplying the lighting power of the light source body. The image display device described.   The image display device according to claim 5, wherein the current limiting element is a passive element that consumes reactive power.   The image display device according to claim 1, wherein the light source body is a semiconductor light emitting element.   The image display device according to claim 8, wherein the semiconductor light emitting element is a light emitting diode.   The image display device according to claim 1, wherein the image display means is a liquid crystal panel. The liquid crystal panel is a transmissive liquid crystal panel,
The image display device according to claim 10, wherein the light source body constitutes a backlight of the transmissive liquid crystal panel.   11. The image display device according to claim 10, wherein a plurality of gate lines connected to the liquid crystal panel are sequentially scanned by an active element provided in the liquid crystal panel. The liquid crystal panel is a transmissive liquid crystal panel, and a plurality of gate lines connected to the transmissive liquid crystal panel are sequentially scanned by active elements provided in the transmissive liquid crystal panel,
The image display device according to claim 10, wherein the light source body constitutes a backlight of the transmissive liquid crystal panel. In an image display device comprising image display means for modulating light based on a video signal and a light source body for illuminating the image display means,
The light source body illuminates the image display means with light in which a pulse component i emitted once per frame of the video signal and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The pulse component h is emitted at a frequency higher than the critical fusion frequency,
There are K light sources (K ≧ 2, K is an integer), the K light sources illuminate the image display means,
The K light source bodies are grouped into N (2 ≦ N ≦ K, where N is an integer) systems whose light emission is controlled independently of each other, and one frame of the video signal is transmitted from each system. Illuminating the image display means by emitting light in which a pulse component i emitted once per pulse and a pulse component h emitted at a frequency higher than the frame frequency are mixed,
The light emission start time of the pulse component i is controlled for each of the N systems according to the timing at which the video is scanned in the image display means.
A protection circuit is provided between the generation circuit of the pulse component i and the pulse component h and a switch for controlling the light emission of the light source body,
The generation circuit outputs a lighting signal composed of a plurality of systems to cause the light source body to emit light to the protection circuit,
The protection circuit counts the number of systems in the same logical state with respect to the lighting signals composed of the plurality of systems, and if the number of systems exceeds a predetermined allowable value, a part or all of the light source body An image display device characterized by turning off the light.

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