JP2002014662A - Backlight control device and its program recoding medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optimal backlight control by effective power saving and good quality display, by controlling the turning-on and turning-off of backlight synchronously with the period of a scanning signal for scanning a light-receiving type display screen. SOLUTION: A synchronous signal control circuit 1-1 selectively outputs one frame start signal FM/one line signal LN according to frame/line selecting information. A counter 1 control circuit 1-3 and a counter 2 control circuit 1-4 start count operation at the time when the signal becomes active, and inputs the count value to a PWM signal generating circuit 1-5. The PWM signal generating circuit 1-5 decodes the frame/line selecting information, offset set value information, and duty set value information, and generates and outputs a PWM signal according to the information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight control device for controlling the turning on and off of a backlight for illuminating a light-receiving display screen, and a program recording medium therefor.

[0002]

2. Description of the Related Art Conventionally, for example, in a mobile information processing terminal, always turning on a backlight for illuminating a liquid crystal display screen of a light receiving type is a method of controlling driving of the backlight to shorten battery life. An optical circuit is provided. This kind of dimming circuit generates a pulse signal which becomes a high level and a low level in a predetermined cycle, and controls the lighting and extinguishing of the backlight at a certain timing according to the pulse signal. That is, the brightness of illumination is controlled by PWM control for adjusting the pulse width of the backlight drive signal.

[0003]

However, in this type of backlight control device, which controls the turning on and off of the backlight at regular intervals, a frame signal and a line for scanning the liquid crystal display screen to rewrite the screen are provided. The screen may "flicker" in relation to the signal,
It was a power saving measure that sacrificed display quality. An object of the present invention is to control the turning on and off of a backlight in synchronization with the cycle of a scanning signal for scanning a light-receiving display screen, thereby enabling effective power saving and obtaining a high quality display. Is to be able to realize the backlight control that is possible.

[0004] The means of the present invention are as follows. According to a first aspect of the present invention, there is provided a backlight control device for controlling lighting and extinguishing of a backlight for illuminating a light-receiving display screen, wherein the predetermined period of time is controlled based on a scanning signal for scanning the light-receiving display screen. A pulse generating means for generating a periodic pulse signal, and a drive control means for controlling turning on and off of the backlight based on the pulse signal generated by the pulse generating means.

[0005] The present invention may be as follows. (1) The pulse generation means generates the pulse signal of the predetermined cycle by synchronizing the cycle of the pulse signal with the cycle of one line signal for scanning the light-receiving display screen. In this case, the pulse generation means synchronizes the cycle of the pulse signal with the cycle of one line signal for scanning the light-receiving display screen, and alternately inverts the high-level position and the low-level position of the pulse signal. Thereby, the pulse signal of the predetermined cycle is generated. (2) The pulse generating means generates the pulse signal of the predetermined cycle by synchronizing the cycle of the pulse signal with the cycle of a plurality of line signals for scanning the light-receiving display screen. In this case, the pulse generation unit synchronizes the cycle of the pulse signal with the cycle of one frame signal for scanning the light-receiving display screen, and alternately inverts the high-level position and the low-level position of the pulse signal. Thereby, the pulse signal of the predetermined cycle is generated. Also,
The pulse generation means generates the pulse signal of the predetermined cycle by synchronizing the cycle of the pulse signal with the cycle of one frame signal for scanning the light-receiving display screen and sequentially changing the number of pulses in one frame. I do. (3) The pulse generation means generates the pulse signal of the predetermined cycle by synchronizing the cycle of the pulse signal with the cycle of a plurality of frame signals for scanning the light-receiving display screen. Therefore, according to the first aspect of the present invention, by controlling the turning on and off of the backlight in synchronization with the cycle of the scanning signal for scanning the light receiving type display screen, effective power saving can be achieved. Display is possible,
Optimal backlight control can be realized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a circuit configuration of a backlight control device according to this embodiment. The backlight control device 1 controls turning on and off of a backlight in synchronization with a cycle of a scanning signal for scanning a light-receiving display screen. Here, one frame start signal FM and one line signal LN are
A display control unit 3 for controlling the driving of the light receiving type liquid crystal display device 2
, And also to the synchronization signal control circuit 1-1 in the backlight control device 1. The one-frame start signal FM and the one-line signal LN are scanning signals for scanning the liquid crystal display screen and rewriting the screen. The synchronization signal control circuit 1-1 outputs a one-frame start signal F
M, a selector for selecting one of the one-line signals LN, and is configured to perform the frame / line selection information supplied from the PWM register 1-2 according to the selection operation.

The one-frame start signal FM / 1 line signal LN selectively output from the synchronization signal control circuit 1-1 is:
Counter 1 control circuit 1-3, counter 2 control circuit 1-4
Respectively. The counter 1 control circuit 1-3 includes:
Each time the one-frame start signal FM / 1 line signal LN becomes active (high level), it controls a counter that starts clearing. By executing a counting operation for counting a reference clock, one cycle of the signal is performed. Are counted. In the counter 2 control circuit 1-4, the one-frame start signal FM / 1 line signal LN is active (HI
(GH level), the counter controls “plus 1”, and counts the number of the current frame / line. Then, the count value (counter value 1) of the counter 1 control circuit 1-3 and the count value (counter value 2) of the counter 2 control circuit 1-4 are given to the PWM signal generation circuit 1-5.

The PWM signal generation circuit 1-5 generates a PWM signal for controlling turning on and off of a backlight in synchronization with a cycle of a scanning signal for scanning a liquid crystal display screen of a light receiving type. The circuit 1-5 is supplied with offset set value information and duty set value information in addition to frame / line selection information from the PWM register 1-2. Here, the PWM register 1-2 stores and holds frame / line selection information, offset set value information, and duty set value information supplied from the CPU. The frame / line selection information includes a synchronization signal. Supplied to the control circuit 1-1 and the PWM signal generation circuit 1-5,
The offset set value information and the duty set value information are supplied to the PWM signal generation circuit 1-5.

The frame / line selection information is information for selectively specifying whether to synchronize a PWM signal with a frame signal or with a line signal. The offset set value information includes a one-frame start signal FM / 1 line signal LN
Is information for instructing the number of the pulse to generate one pulse of the PWM signal. The duty set value information is information for instructing the duty ratio of the PWM signal. The PWM signal generated by the PWM signal generation circuit 1-5 is input to a backlight control circuit 1-6, which controls turning on and off of a backlight 4 for a liquid crystal display screen.

In this case, the PWM signal generation circuit 1-5
When generating a PWM signal based on frame / line selection information, offset set value information, and duty set value information, the following control is performed. That is, (1) the period of the PWM signal is synchronized with the period of the one-line signal LN. (2) Synchronize with the cycle of one line signal of the PWM signal, and alternately invert the high level position and the low level position of the pulse. (3) Synchronize the cycle of the PWM signal with the cycle of a plurality of line signals. (4) The period of the PWM signal is synchronized with the period of the one-frame signal, and the high-level position and the low-level position of the pulse are alternately inverted. (5) The period of the PWM signal is synchronized with the period of one frame signal, and the number of pulses in one frame is sequentially changed. (6) Synchronize the cycle of the PWM signal with the cycle of a plurality of frame signals.

FIG. 2 is a block diagram showing a mobile information terminal provided with the above-described backlight control device 1 and light receiving type liquid crystal display device 2. The CPU 11 is a storage device 2
It is a central processing unit that controls the overall operation of this information terminal in accordance with an operating system and various application software inside. The storage device 12 stores an operating system, various application software, and the like, and has a recording medium 13 composed of a magnetic, optical, semiconductor memory, and the like, and a drive system therefor. The recording medium 13 is a fixed medium such as a hard disk or a portable medium such as a CD-ROM, a floppy desk, a RAM card, and a magnetic card which can be detachably mounted. The programs and data in the recording medium 13 are loaded into a RAM (for example, a static RAM) 14 under the control of the CPU 11 as necessary,
The data in 14 is saved on the recording medium 13. Furthermore,
The recording medium may be provided on an external device such as a server, and the CPU 11 may directly access and use the program / data in the recording medium via a transmission medium. Further, the CPU 11 takes in part or all of the data stored in the recording medium 13 from another device via a transmission medium (transmission control unit 5), and reads the recording medium 1
3 can be newly registered or additionally registered. Furthermore, the program / data may be stored and managed on the external device side such as a server, and the CPU 11 may directly access and use the program / data on the external device side via a transmission medium. On the other hand, the display device 2, the transmission control unit 15, and the input unit 16, which are input / output peripheral devices, are connected to the CPU 11 via a bus line, and the CPU 11 controls the operation according to an input / output program.

FIG. 3 shows the contents of a setting table 20 in which frame / line selection information, offset set value information, and duty set value information are set. That is,
When the PWM signal generation circuit 1-5 generates the PWM signal based on the frame / line selection information, the offset setting value information, and the duty setting value information, the above-described (1) to (1).
The control of (6) is performed, and the setting table 20 stores “frame / line selection information”, “offset set value information”, and “duty set value information” for each type in association with the type of the PWM signal. Is stored and managed.

Next, the operation of this embodiment will be described with reference to a flowchart shown in FIG. 4 and a time chart shown in FIG. A program for realizing each function described in this flowchart is stored in the form of a readable program code in the recording medium 13, and the CPU 11 sequentially executes operations according to the program code. FIG. 4 is a flowchart mainly showing a case where frame / line selection information, offset set value information, and duty set value information are set in the PWM register 1-2.

First, in a key input waiting state (step S1), when a table read key operation for reading the contents of the setting table 20 by type is performed (step S2), the key is designated by the table read key. Frame / line selection information corresponding to the type,
The offset setting value information and the duty setting value information are read from the setting table 20 and set in the PWM register 1-2 in the backlight control device 1 (step S).
3). The “OFFSE” provided in the input unit 16
When the "T variable input key" is operated (step S
4), the changed value (input value) is stored in the PWM register 1-
2 is set as offset set value information (step S5). The “DUTY” provided in the input unit 16
When the “variable input key” is operated (step S
6), the variable value (input value) is stored in the PWM register 1-
2 is set as duty set value information (step S7). When another key is operated (step S6), a key input process corresponding to the operation is performed (step S8). In the key input waiting state, it is checked whether the display data is updated, that is, whether the screen is to be rewritten (step S9).
The display data is written into the display control unit 3 (step S1).
0).

Next, the operation of the backlight control device 1 will be described. Here, the frame / data is stored in the PWM register 1-2.
In a state where the line selection information, the offset setting value information, and the duty setting value information are set, the synchronization signal control circuit 1-1 sets 1 according to the frame / line selection information.
A frame start signal FM / 1 line signal LN is selectively output. Then, the counter 1 control circuit 1-3 and the counter 2 control circuit 1-4 start the counting operation at the timing when the signal becomes active, and change the count value to PW.
The signal is supplied to the M signal generation circuit 1-5. Here, the PWM signal generation circuit 1-5 decodes frame / line selection information, offset set value information, and duty set value information, and generates and outputs a PWM signal according to the information.

FIG. 5 exemplifies a part of each of the PWM signals that can be generated by the PWM signal generation circuit 1-5. One line signal LN shown in FIG. 5A and one frame signal shown in FIG. With respect to the start signal FM, (C) synchronizes the cycle of the PWM signal with the cycle of one frame signal,
When the high level position and the low level position of the pulse are alternately inverted, (D) synchronizes the cycle of the PWM signal with the cycle of the one-line signal LN, and (E) expresses PW
FIG. 9 illustrates a part of a PWM signal waveform when the cycle of the M signal is synchronized with the cycle of two line signals. When the offset setting value information is “1 pulse” and the duty setting value information is “50%”, the PWM signal shown in (C) and (D) is the offset setting value information. Is "2 pulses" and the duty set value information is "50%". In addition, the generated PWM
The finer the signal, the more power is required. Nevertheless, the power consumption is sufficiently reduced as compared with the prior art, and the finer the signal, the better the lighting state. Further, it is clear that the power consumption is saved as the generated PWM signal is rough.

Thus, the PWM signal generating circuit 1-5
Since the PWM signal generated by the above is input to the backlight control circuit 1-6, the turning on / off of the backlight 4 for the liquid crystal display screen is synchronized with the cycle of the one frame start signal FM / 1 line signal LN. It will be. in this case,
For example, simply synchronizing the cycle of the PWM signal with the cycle of one frame signal causes a predetermined range of the screen to be a non-lighting area at all times, and a black stripe “streak” may be generated in the area, so that the high level of the pulse is generated. The level position and the low level position are alternately inverted. Also, while synchronizing the cycle of the PWM signal with the cycle of one frame signal,
By sequentially changing the number of pulses in one frame,
As described above, the black stripe-shaped “streak” can be eliminated.

As described above, in this embodiment, the turning on and off of the backlight is controlled in synchronization with the period of the scanning signal for scanning the light receiving type display screen, so that effective power saving is possible. In addition to this, it is possible to obtain a high-quality display, and it is possible to realize optimal backlight control. In this case, it is possible to synchronize the cycle of the PWM signal with the cycle of the one-line signal LN or the cycle of the one-line signal of the PWM signal, and alternately invert the high-level position and the low-level position of the pulse. In addition, the cycle of the PWM signal is synchronized with the cycle of a plurality of line signals, the cycle of the PWM signal is synchronized with the cycle of one frame signal, and the high level position and the low level position of the pulse are alternately inverted. Or the period of the PWM signal can be synchronized with the period of one frame signal. Further, the number of pulses in one frame can be sequentially changed, or the period of the PWM signal can be synchronized with the period of a plurality of frame signals. it can. Therefore, effective power saving is possible, and "flickering" of screens and "streaks" of black stripes are eliminated. Display can be obtained.

Further, "frame / line selection information", "offset set value information", and "duty set value information" are stored and managed in the setting table 20 in association with the type of the PWM signal for each type. , The contents of the setting table 20 are read out by type, and the PWM register 1-
2, and can be set to P by operating the “OFFSET variable input key” and the “DUTY variable input key”.
“Offset setting value information” in the WM register 1-2,
Since the "duty setting value information" can be changed arbitrarily, the user can obtain a desired light control.

[0020]

According to the present invention, the turning on and off of the backlight is controlled in synchronization with the period of the scanning signal for scanning the light receiving type display screen, so that effective power saving can be achieved. , It will be possible to obtain high quality display, etc.
Optimal backlight control can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a backlight control device.

FIG. 2 is a block diagram showing a mobile information terminal.

FIG. 3 is a diagram showing the contents of a setting table 20 in which frame / line selection information, offset set value information, and duty set value information are set.

FIG. 4 is a flowchart mainly showing a case where frame / line selection information, offset set value information, and duty set value information are set in a PWM register 1-2.

5A shows a one-line signal LN, FIG. 5B shows a one-frame start signal, and FIGS. 5C to 5E show PWM signals generated by a PWM signal generation circuit 1-5. FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 backlight control device 1-1 synchronization signal control circuit 1-2 PWM register 1-3 counter 1 control circuit 1-4 counter 2 control circuit 1-5 PWM signal generation circuit 1-6 backlight control circuit 2 liquid crystal display device 3 display control unit 11 CPU 12 storage device 13 recording medium 15 transmission control unit 16 input unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/34 G09G 3/34 J F-term (Reference) 2H093 NA41 NC42 NC50 ND10 ND39 5C006 AF42 AF44 AF69 BF22 EA01 FA23 FA47 5C080 AA10 DD05 DD06 DD26 JJ02 JJ04 JJ07 5G435 BB12 BB15 EE25

Claims (8)

[Claims] 1. A backlight control device for controlling lighting and extinguishing of a backlight for illuminating a light-receiving display screen, wherein a pulse signal of a predetermined cycle synchronized with the cycle based on a scanning signal for scanning the light-receiving display screen A backlight control device comprising: a pulse generation unit that generates a pulse signal; and a drive control unit that controls turning on and off of the backlight based on a pulse signal generated by the pulse generation unit. 2. The apparatus according to claim 1, wherein said pulse generation means generates said pulse signal of said predetermined period by synchronizing a period of said pulse signal with a period of one line signal for scanning a light receiving type display screen. 2. The backlight control device according to claim 1, wherein 3. The pulse generating means synchronizes a cycle of the pulse signal with a cycle of a one-line signal for scanning a light-receiving display screen, and alternates a high level position and a low level position of the pulse signal. 3. The backlight control device according to claim 2, wherein the pulse signal of the predetermined period is generated by inverting the pulse signal. 4. The apparatus according to claim 1, wherein said pulse generating means generates said pulse signal of said predetermined period by synchronizing a period of said pulse signal with a period of a plurality of line signals for scanning a light-receiving display screen. 2. The backlight control device according to claim 1, wherein: 5. The pulse generating means synchronizes a cycle of the pulse signal with a cycle of one frame signal for scanning a light-receiving display screen, and alternates a high level position and a low level position of the pulse signal. 5. The backlight control device according to claim 4, wherein the pulse signal of the predetermined cycle is generated by inverting the pulse signal. 6. The pulse generator according to claim 1, wherein the pulse generator synchronizes a cycle of the pulse signal with a cycle of one frame signal for scanning the light receiving type display screen, and sequentially changes the number of pulses in one frame. 5. The backlight control device according to claim 4, wherein the pulse signal is generated. 7. The apparatus according to claim 1, wherein said pulse generating means generates said pulse signal of said predetermined period by synchronizing a period of said pulse signal with a period of a plurality of frame signals for scanning a light-receiving display screen. 2. The backlight control device according to claim 1, wherein: 8. A recording medium having a program code readable by a computer, wherein a pulse signal of a predetermined cycle synchronized with the cycle based on a scanning signal for scanning a light receiving type display screen is turned on and off of a backlight. A recording medium having a computer-readable program code for arbitrarily setting generation control information for instructing the generation in order to generate a drive control signal for controlling the generation.