Display control device

Abstract

The purpose is to prevent the backlight from accidentally illuminating due to the power plug being unplugged and then plugged back in while in power-saving mode. [Solution] The display control device comprises an ASIC that starts a startup process when power is turned on and outputs a Wake_up signal after the startup process is completed, a first transistor Q1 that applies voltage to the backlight when it is turned ON by the Wake_up signal transmitted from the ASIC, and a second transistor Q2 that energizes the backlight when it is turned ON by the LED_PWM signal.

Description

Technical Field

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[0001] The present invention relates to a display control device.

Background Art

[0002] There is known an image forming apparatus capable of setting a power saving mode (which may also be called by names such as a low power mode, a power off mode, etc.). The power saving mode is a mode in which power supply to some components of the image forming apparatus is stopped to reduce power consumption compared to the normal mode. When a standby state in which an image forming job is not executed in the normal mode continues for a predetermined time, it switches to the power saving mode. In the power saving mode, for example, power supply to the backlight of the liquid crystal panel is stopped and the backlight is turned off. Therefore, there is a case where a user may mistakenly think that the power switch of the image forming apparatus is turned off and pull out the power plug from the outlet. After that, when the power cord is plugged into the outlet, since the power switch is not turned off, the backlight lights up and startles the user. In addition, there is a possibility that malfunctions or failures of the image forming apparatus may occur.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, technologies have been considered to prevent malfunctions caused by changes in the power supply state to the liquid crystal panel (for example, Patent Documents 1 and 2). However, the configuration disclosed in Patent Document 1 is a measure to prevent malfunctions of the display device due to noise when the host device is powered on or reset, in a configuration where the power switch of the display device is turned on and the power of the display device is also linked to the operation of the power supply of the host device. Furthermore, the configuration disclosed in Patent Document 2 is a measure to prevent malfunctions when touch input is made on any of the touch panel displays in a multi-display system in which multiple touch panel displays are connected to one computer.Therefore, the configurations disclosed in Patent Documents 1 and 2 cannot prevent the backlight from turning on when the power plug is unplugged and then plugged back in while in power-saving mode.

[0005] Considering the above circumstances, the present invention aims to prevent the backlight from illuminating incorrectly due to the unplugging and subsequent plugging of the power cord while in power-saving mode. [Means for solving the problem]

[0006] To solve the above problems, the display control device according to the present invention comprises an ASIC that starts a startup process when power is turned on and outputs a Wake_up signal after the startup process is completed; a first transistor that applies a voltage to the backlight when it is turned ON by the Wake_up signal transmitted from the ASIC; and a second transistor that energizes the backlight when it is turned ON by the LED_PWM signal.

[0007] The ASIC may include a liquid crystal panel CPU that outputs the aforementioned LED_PWM signal, and after the startup process is completed, the ASIC may transmit mode information indicating whether it is in normal mode or power-saving mode to the liquid crystal panel CPU. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent the backlight from illuminating incorrectly due to the power plug being unplugged and then plugged back in while in power-saving mode. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing the external appearance of a printing apparatus according to one embodiment of the present invention. [Figure 2] This is a schematic right-side view showing the internal configuration of a printing apparatus according to one embodiment of the present invention. [Figure 3] This is a circuit diagram of a display control device according to one embodiment of the present invention. [Figure 4] This is a circuit diagram of a false illumination prevention circuit according to one embodiment of the present invention. [Figure 5] This is a timing diagram of control by a display control device according to one embodiment of the present invention. [Figure 6] This is a timing diagram of control by a display control device according to one embodiment of the present invention. [Figure 7] This is a flowchart illustrating the control mechanism of a display control device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] The following describes a printing apparatus 1 according to one embodiment of the present invention, with reference to the drawings.

[0011] Figure 1 is a perspective view showing the external appearance of the printing device 1. Figure 2 is a schematic right side view showing the internal configuration of the printing device 1. In each figure, U, Lo, L, R, Fr, and Rr indicate top, bottom, left, right, front, and back, respectively. Note that these directions are defined only for the sake of explanation.

[0012] The printing device 1 (see Figures 1 and 2) comprises a rectangular parallelepiped main body housing 3. Inside the lower part of the main body housing 3, there is a paper feed cassette 4 in which sheets S are stored, and a paper feed roller 5 that feeds the sheets S backward from the paper feed cassette 4. Above the paper feed cassette 4, there is an imaging device 6 that forms a toner image using an electrophotographic method, and above and behind the imaging device 6, there is a fixing device 7 that fixes the toner image onto the sheet S. Above the fixing device 7, there is an discharge roller 8 that discharges the sheet S with the toner image fixed on it, and an discharge tray 9 on which the discharged sheets S are stacked.

[0013] Inside the main housing 3, a transport path 10 is provided, which runs from the paper feed roller 5 through the image creation device 6 and the fixing device 7 to the discharge roller 8. The transport path 10 is mainly formed of plate-shaped members that face each other with gaps between them to allow the sheet S to pass through, and transport rollers 17 that grip and transport the sheet S are provided at multiple locations in the transport direction Y. A registration roller 18 is provided upstream of the image creation device 6 in the transport direction Y. Behind the fixing device 7, a reversal transport path 10R is provided. The reversal transport path 10R branches off from the transport path 10 at a branching point located downstream of the fixing device 7 in the transport direction Y, and rejoins the transport path 10 at a confluence point located upstream of the registration roller 18 in the transport direction Y.

[0014] The imaging device 6 comprises four sets of imaging units 6U and an intermediate transfer unit 15. Each imaging unit 6U includes a photoreceptor drum 11 whose potential changes upon irradiation with light, a charging device 12 that charges the photoreceptor drum 11, an exposure device 13 that emits laser light corresponding to the image data, a developing device 14 that supplies toner to the photoreceptor drum 11, and a cleaning device 16 that removes toner remaining on the photoreceptor drum 11. The intermediate transfer unit 15 includes an endless intermediate transfer belt 15B wrapped around a drive roller 15D and a driven roller 15N, a primary transfer roller 151 that faces the inner surface of the intermediate transfer belt 15B at a position corresponding to the photoreceptor drum 11 and generates a primary transfer bias, and a secondary transfer roller 152 that faces the outer surface of the intermediate transfer belt 15B at a position corresponding to the drive roller 15D and generates a secondary transfer bias. A toner container 20 that supplies toner to the developing device 14 is connected to the developing device 14. The imaging device 6 forms a color image by superimposing four-color toner images onto the intermediate transfer belt 15B. The printing device 1 may be equipped with two, three, or five or more imaging units 6U.

[0015] The control unit 2 comprises an arithmetic unit and a memory unit (not shown). The arithmetic unit is, for example, a CPU (Central Processing Unit). The memory unit includes a storage medium such as ROM (Read Only Memory), RAM (Random Access Memory), or EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing the control program stored in the memory unit. Note that the control unit 2 may be implemented using only integrated circuits without the use of software.

[0016] The display operation unit 19 includes a liquid crystal panel 19A and a touch panel 19B superimposed on the display surface of the liquid crystal panel 19A. The control unit 2 displays a screen on the liquid crystal panel 19A showing the operation menu and status of the printing device 1, and controls each part of the printing device 1 in accordance with the operation detected by the touch panel 19B.

[0017] When a print job is input to the printing apparatus 1, the paper feed roller 5 feeds the sheet S from the paper feed cassette 4 into the conveyance path 10, the registration roller 18 whose rotation has been stopped corrects the posture of the sheet S, and the registration roller 18 feeds the sheet S to the image forming apparatus 6 at a predetermined timing. In the image forming apparatus 6, the charging device 12 charges the photosensitive drum 11 to a predetermined potential, the exposure device 13 writes a latent image on the photosensitive drum 11, and the developing device 14 develops the latent image using the toner supplied from the toner container 20 to form a toner image. The primary transfer roller 151 transfers the toner image to the intermediate transfer belt 15B, and the secondary transfer roller 152 transfers the toner image to the sheet S.

[0018] Subsequently, the fixing device 7 sandwiches and conveys the sheet S and melts the toner image to fix the toner image on the sheet S, and the discharge roller 8 discharges the sheet S to the discharge tray 9. In the case of double-sided printing, the sheet S with the toner image fixed on the first side is fed into the conveyance path 10 via the reverse conveyance path 10R, and the toner image is transferred to the second side.

[0019] FIG. 3 is a circuit diagram of the display control device 30. FIG. 4 is a circuit diagram of the malfunction prevention circuit 55. FIGS. 5 and 6 are timing diagrams of the control by the display control device 30. FIG. 7 is a flowchart of the control by the display control device 30.

[0020] The liquid crystal panel 19A mainly has a structure in which a backlight 53, a liquid crystal layer (not shown), an electrode group 54 (common electrode, array electrode), and a color filter (not shown) are laminated. Hereinafter, the configuration in which the display control device 30 controls the liquid crystal panel 19A will be described. The display control device 30 includes a main board 31 and a liquid crystal panel board 51.

[0021] The main board 31 includes an ASIC 32 (Application Specific Integrated Circuit), a PMIC 33 (Power Management integrated circuit), an RTC 34 (Real-time Clock), and DC-DC converters 35, 36, and 37. The ASIC 32 controls the entire printing device 1. The PMIC 33 controls the power supply to each part of the printing device 1. The RTC 34 continues to keep time even when the power is cut off. The RTC 34 also holds mode information indicating whether the printing device 1 is in normal mode or power-saving mode. The RTC 34 continues to hold mode information even when the power is cut off. The DC-DC converters 35, 36, and 37 convert the voltage of the DC power.

[0022] The LVU41 (Low Voltage Unit) converts the 100V AC power supplied from the commercial power supply to 24V DC and supplies it to the main board 31. The power switch 42 is a switch that can select either to supply or stop power via the PMIC 33.

[0023] The liquid crystal panel substrate 51 includes a liquid crystal panel CPU 52 (Central Processing Unit), a backlight 53, an electrode group 54, and a false illumination prevention circuit 55. The liquid crystal panel CPU 52 controls the backlight 53 and the electrode group 54. The backlight 53 is formed by arranging white LEDs, for example, and its brightness is controlled by pulse width modulation. The electrode group 54 includes common electrodes and array electrodes that face each other across the liquid crystal layer (not shown).

[0024] The operation of the display control device 30 will be described (see Figures 5, 6, and 7). Here, Figure 5 shows the case where the time Tr required for the startup process of ASIC32 is less than 200ms, and Figure 6 shows the case where the time Tr required for the startup process of ASIC32 is 200ms or more.

[0025] When the power plug of the printing device 1 is plugged into an outlet, the LVU 41 generates 24V0, the DC-DC converter 35 converts 24V0 to 3.3V0, and supplies 3.3V0 to the ASIC 32 and PMIC 33 (step S01). Next, the PMIC 33 starts up (step S02) and sends a reset signal to the ASIC 32 (step S03). Upon receiving the reset signal, the ASIC 32 starts the startup process. The PMIC 33 also outputs an EN5V signal to the DC-DC converter 36 and an EN3.3V signal to the DC-DC converter 37 (step S11). The DC-DC converter 36 then generates 5.0V1C and supplies 5.0V1C to a predetermined load circuit (step S12). Furthermore, the DC-DC converter 37 generates 3.3V1C and supplies 3.3V1C to a predetermined load circuit including the LCD panel CPU 52 (step S12).

[0026] The LCD panel CPU 52, supplied with 3.3V1C, begins the reset process (step S13). For the LCD panel CPU 52 to complete the reset process, it must receive a reset signal from the ASIC 32. However, the ASIC 32 will not send the reset signal to the LCD panel CPU 52 until its startup process is complete. The time Tr required for the ASIC 32 startup process is not constant and varies.

[0027] If the ASIC32 startup process takes a long time, the following may occur: When the printer 1 switches from normal mode to power-saving mode, power is stopped to the backlight 53 of the LCD panel 19A, and the backlight 53 turns off. As a result, the user may mistakenly think that the power switch 42 of the printer 1 is turned off and unplug the power cord from the outlet. Mode information indicating whether the printer was in normal mode (Ready) or power-saving mode (Sleep) before the power was cut off is retained in the RTC34 even after the power is cut off. When the power cord is plugged back into the outlet, the power switch 42 is not turned off, and the ASIC32 startup process begins.

[0028] Here, if the time Tr required for the ASIC32 startup process is less than 200ms (see Figure 5), the ASIC32 sends mode information to the LCD panel CPU52. The LCD panel CPU52 can then recognize that the printer 1 was in power-saving mode before the power was turned off and outputs the LED_PWM signal at a low level.

[0029] However, if the time Tr required for the ASIC32 startup process is 200ms or more (see Figure 6), the ASIC32 cannot transmit mode information to the LCD panel CPU 52. As a result, the LCD panel CPU 52 cannot recognize that the printer 1 was in power-saving mode before the power was turned off, and outputs the LED_PWM signal at a high level (period Ta in Figure 6), causing the backlight 53 to light up incorrectly. After the ASIC32 startup process is completed, the ASIC32 transmits mode information to the LCD panel CPU 52, and the LCD panel CPU 52 outputs the LED_PQM signal at a low level.

[0030] Therefore, in this embodiment, the false illumination prevention circuit 55 prevents the false illumination of the backlight 53. The false illumination prevention circuit 55 includes a first circuit 56 equipped with a first transistor Q1 that is switched by a Wake_up signal, and a second circuit 57 equipped with a second transistor Q2 that is switched by an LED_PWM signal. After the startup process of the ASIC 32 is completed, the ASIC 32 sends a Wake_up signal to the liquid crystal panel CPU 52 (steps S04, S05). After receiving the Wake_up signal, the liquid crystal panel CPU 52 supplies an LED_PWM signal to the backlight 53.

[0031] The emitter of the first transistor Q1 and the collector of the second transistor Q2 are connected to the backlight 53. A diode D1 is provided between the collector of the second transistor Q2 and the backlight 53.

[0032] First, if the time Tr required for the ASIC32 startup process is less than 200ms (see Figure 5), the ASIC32 sends mode information to the LCD panel CPU52. The LCD panel CPU52 can then recognize that the printer 1 was in power-saving mode before the power was cut off and outputs the LED_PWM signal at a low level. Therefore, the backlight 53 does not light up incorrectly.

[0033] On the other hand, if the time Tr required for the ASIC32 startup process is 200ms or more (see Figure 6), the ASIC32 cannot transmit mode information to the LCD panel CPU 52. Therefore, the LCD panel CPU 52 cannot recognize that the printer 1 was in power-saving mode before the power was turned off, and outputs the LED_PWM signal at a high level (period Ta in Figure 6, step S14 in Figure 7: YES). However, because the Wakw_up signal is at a low level (step S15: NO), the first transistor Q1 turns OFF, and 5.0V 1C is not applied to the backlight 53 (step S17). Consequently, even if the LED_PWM signal is at a high level, no current flows to the backlight 53, so the backlight 53 does not light up incorrectly.

[0034] The display control device 30 according to the embodiment described above includes an ASIC 32 that starts a startup process when the power is turned on and outputs a Wake_up signal after the startup process is completed, a first transistor Q1 that applies voltage to the backlight 53 when it is turned ON by the Wake_up signal transmitted from the ASIC 32, and a second transistor Q2 that energizes the backlight 53 when it is turned ON by the LED_PWM signal. With this configuration, the mode information of the printing device 1 cannot be confirmed until the startup of the ASIC 32 is completed, but since the first transistor Q1 applies voltage to the backlight 53 based on the Wake_up signal output after the startup process of the ASIC 32 is completed, false illumination of the backlight 53 is prevented even before the mode information is confirmed.Therefore, according to this embodiment, false illumination of the backlight 53 due to unplugging and then plugging in the power plug in power saving mode can be prevented.

[0035] Furthermore, according to the display control device 30 of this embodiment, a liquid crystal panel CPU 52 that outputs an LED_PWM signal is provided, and the ASIC 32 transmits mode information indicating whether it is in normal mode or power-saving mode to the liquid crystal panel CPU 52 after the startup process is completed. With this configuration, even if the liquid crystal panel CPU 52 outputs an LED_PWM signal before receiving the mode information, it is possible to prevent the backlight 53 from lighting up incorrectly. [Explanation of symbols]

[0036] 1 Printing device 30 Display control device 32 ASIC 52 LCD panel CPU 53 Backlight Q1 First transistor Q2 Second transistor 52 LCD panel CPU

Claims

1. An ASIC that initiates a startup process when power is turned on and outputs a Wake_up signal after the startup process is completed, A first transistor that applies voltage to the backlight when it is turned ON by the Wake_up signal transmitted from the ASIC, A display control device characterized by comprising a second transistor that energizes the backlight when it is turned ON by an LED_PWM signal.

2. The system includes a liquid crystal panel CPU that outputs the aforementioned LED_PWM signal, The display control device according to claim 1, characterized in that the ASIC transmits mode information indicating whether it is in normal mode or power-saving mode to the liquid crystal panel CPU after the startup process is completed.

Images