JP2010051054A - Display system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for achieving appropriate display in a display system for vehicles without complicating its circuitry even when noise occurs in a signal from an ignition switch. <P>SOLUTION: In the display system 10, noise determination is carried out with respect to a signal of an ignition switch ING(+) and based on the result of the processing, it is determined whether or not the signal level of the ignition switch ING(+) is normal ON. When the normal ON signal is determined, a control unit 20 outputs a control signal for turning on an FET 48 through an I/O terminal 26. As a result, driving voltage is supplied from a common constant voltage IC 42 to an LCD display 30. When the normal ON signal is not detected, the control unit 20 turns off the FET 48 through the I/O terminal 26 to enter a sleep mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display system, and more particularly to a display system that is mounted on a vehicle and performs display control according to on / off of an ignition switch.

  In vehicles such as current automobiles, a large number of electrical devices are mounted, and they can be roughly classified as follows with the ignition switch turned off. That is, it is classified into three types: (1) a device that does not require operation, (2) a device that stops operation after a predetermined process, and (3) a device that continues operation. A circuit and control for power supply are set according to the classification. That is, the microcomputer (CPU) that has acquired the signal related to turning off the ignition switch controls the power supply to each electrical equipment to stop immediately, stop after a predetermined period, or continue.

  When the ignition switch is off, the vehicle engine is stopped and, of course, no power is generated. Therefore, power saving control is important. For example, there are a display system such as a meter panel, a clock, and a security device as devices that continue to operate when the ignition switch is off. FIG. 1 is a functional block diagram showing the configuration of a display system 100 according to the prior art. As illustrated, the display system 100 includes an LCD display 130 that is a display panel, a control unit 120, and a power supply control circuit 140. The power control circuit 140 includes a CPU constant voltage IC 144 that supplies power to the Vcc terminal 122 of the control unit 120 with a constant voltage, and a CPU constant voltage IC 144 that supplies drive power to the Vcc terminal 132 of the LCD display 130 with a constant voltage. And an I / O unit 146 that converts the on / off state of the ignition switch into a predetermined signal and outputs the signal to the INT terminal 124 of the control unit 120. At this time, the CPU constant voltage IC 144 is directly supplied with power from the battery (B +).

  Then, the control unit 120 may be set to the sleep mode for power saving when the vehicle is stopped (engine stopped) due to the on / off state of the ignition switch ING (+) of the engine start switch system. Specifically, after a predetermined time has elapsed after the ignition switch ING (+) is turned off, the control unit 120 is set to the sleep mode. If noise occurs in the signal of the ignition switch ING (+) in the sleep mode, the LCD constant voltage IC 142 may be turned on, and the control unit 120 may be in an unstable state. Then, the LCD display 130 may cause display flickering called chattering.

  For noise countermeasures, for example, a technique in which a microcomputer performs a filtering process on the output of a power supply voltage in a software manner is disclosed (see Patent Document 1). There is also a power switch circuit that can cut off the power supply from the constant voltage power supply circuit to the meter while the ignition switch is off (see Patent Document 2).

JP-A-11-258279 JP 2004-357445 A

  By the way, with the technique disclosed in Patent Document 1, it is difficult to directly apply to a power supply device mounted on a vehicle, and a signal from an ignition switch is always subjected to filtering processing in a software manner, resulting in a relatively large processing load. Therefore, there is a demand for processing with a low processing load without reducing power consumption. In addition, the technique disclosed in Patent Document 2 has a problem that the circuit configuration becomes complicated because a switching control circuit that operates in conjunction with the signal of the ignition switch and switches the power switch circuit is required.

  This invention is made | formed in view of such a condition, and it aims at providing the technique which can solve the said subject.

One embodiment of the present invention relates to a display system. This display system is a vehicle display system comprising: a power supply unit that supplies power to the display unit; and a control unit that receives a signal from an ignition switch and controls the power supply of the display unit. Switching means disposed in a power supply path from the power supply means to the display means and controlled to be turned on / off by the control means, wherein the control means determines whether or not the signal from the ignition switch is noise. Then, when it is determined that the noise is present, the switching means is controlled to maintain the on or off state.
Further, the control means may change the operation state of the control means to a sleep mode after controlling the switching means from the on state to the off state.
The power supply means supplies power to the display means and the control means,
The switching means may be arranged at a stage after a power supply path from the power supply means branches to the display means and the control means.
Further, the control means determines that when the ignition switch is in an on state and the switching means is in an on state, the ignition switch shifts to an off state, and the signal from the ignition switch is noise. Sometimes, the switching means may be kept on.

  ADVANTAGE OF THE INVENTION According to this invention, even when noise generate | occur | produces in the signal from an ignition switch in the display system for vehicles, the technique which performs an appropriate display without having a complicated circuit structure can be provided.

  The best mode for carrying out the invention (hereinafter referred to as “embodiment”) will be described below with reference to the drawings. FIG. 2 is a functional block diagram showing a schematic configuration of the display system 10 according to the present embodiment. As illustrated, the display system 10 includes a control unit 20, an LCD display 30, and a power supply control circuit 40. The common constant voltage IC 42 of the power supply control circuit 40 is directly connected to a battery (B +) mounted on the vehicle. Then, the control unit 20 detects the on / off of the signal from the ignition switch ING (+), and controls the switching element (FET 48) with a predetermined control signal based on the detection result, whereby the power supply control circuit 40 controls the LCD display 30. The supply of the drive voltage is controlled.

  The control unit 20 controls the display system 10 in an integrated manner, and outputs a control signal for turning on and off a Vcc terminal 22 that receives supply of constant voltage power from the power supply control circuit 40 and an FET 48 of the control unit 20 described later. / O terminal 26 and an INT terminal 24 for obtaining an on / off signal from the ignition switch ING (+). Further, the control unit 20 determines whether or not the signal from the ignition switch ING (+) is noise, and when it is determined that the signal is noise, the control unit 20 maintains the on / off state of the FET 48 as a control signal to the FET 48. Output as follows.

  The power supply control circuit 40 includes a common constant voltage IC 42, a first I / O unit 44, a second I / O unit 46, and an FET 48.

  The common constant voltage IC 42 is directly connected to the positive terminal of the battery (B +) mounted on the vehicle, and supplies power to the control unit 20 and the LCD display 30 with a predetermined constant voltage. More specifically, the output from the common constant voltage IC 42 is branched into two systems at a branch point T1, and one system is connected to the FET 48, and the other system is connected to the Vcc terminal 22 of the control unit 20.

  The FET 48 is provided between the common constant voltage IC 42 and the LCD display 30 (Vcc terminal 32) and functions as switching means having an on / off function. In the figure, a P-channel type FET 48 is shown as the switching means, but the present invention is not limited to this, and it is sufficient that the switching means has a function as a switching function. A control signal from the I / O terminal 26 is input to the gate electrode of the FET 48 via the first I / O unit 44.

  The first I / O unit 44 adjusts the signal output from the I / O terminal 26 of the control unit 20 to a magnitude (potential) suitable for driving the FET 48. Therefore, the first I / O unit 44 may be omitted if the signal output from the I / O terminal 26 has a magnitude suitable for driving the FET 48.

  Similarly, the second I / O unit 46 converts the signal of the ignition switch ING (+) into a predetermined magnitude and outputs it to the INT terminal 24 of the control unit 20. Although the signal of the ignition switch ING (+) may be directly input to the control unit 20, the second I / O unit 46 is provided in view of conversion to a size suitable for the control unit 20 and prevention of excessive signal input. Generally provided.

  The operation of the display system 10 having the above configuration will be described. FIG. 3 is a flowchart illustrating an operation when an on-level signal is input to the INT terminal 24 of the control unit 20.

  In a state where the FET 48 is off and the drive current is not supplied to the LCD display 30, the signal from the ignition switch ING (+) becomes the on level (high level), and the signal is the second I / O unit 46. Is input to the INT terminal 24 of the control unit 20, the control unit 20 performs a noise determination process as to whether or not the on-level signal is noise (S10). For example, when the on-level period is short or over-level, the control unit 20 determines that the signal is noise.

  Then, the control unit 20 determines whether or not the signal level of the ignition switch ING (+) is a normal on signal, that is, whether the driver intends to turn on based on the result of the noise determination process (S12). If it is determined that the signal is a regular on signal (Y in S12), the control unit 20 outputs a control signal for turning on the FET 48 from the I / O terminal 26 (S14). As a result, the drive voltage is supplied from the common constant voltage IC 42 to the LCD display 30, and the LCD display 30 enters the display state.

  When it is determined that the signal is not a regular on signal, for example, when the signal is an off signal or when the signal is temporarily turned on due to noise (N in S12), the control unit 20 turns off the FET 48 from the I / O terminal 26. The control signal is output to turn off the LCD display 30 (S16), and the own processing mode is set to the sleep mode for power saving (S18). Therefore, when the control unit 20 is in the sleep mode, the drive voltage of the LCD display 30 is always turned off. As a result, chattering does not occur in the display of the LCD display 30 even when noise is applied to the signal of the ignition switch ING (+) in this state.

  As described above, according to the present embodiment, even when noise is applied to the signal from the ignition switch in the electrical device such as the display system 10, the influence can be eliminated. Further, the voltage supplied to the control unit 20 and the LCD display 30 is obtained by converting the voltage supplied directly from the battery (B +) instead of from the ignition switch ING (+) by the common constant voltage IC 42. As a result, it is possible to eliminate voltage fluctuation factors (such as the influence of noise) caused by the ignition switch ING (+) of the voltage supplied to the control unit 20 and the LCD display 30, and display flickering caused by them. Further, the circuit configuration of the power supply control circuit 40 is not complicated. Further, since the signal of the ignition switch ING (+) is not filtered, the processing load can be very small.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it is understood by those skilled in the art that various modifications can be made to each of those components and combinations thereof, and such modifications are also within the scope of the present invention.

It is a functional block diagram which shows schematic structure of the display system based on a prior art. It is a functional block diagram which shows schematic structure of the display system based on embodiment. It is the flowchart which showed the process of ON / OFF of the ignition switch in the display system based on Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display system 20 Control part 22 Vcc terminal 24 INT terminal 26 I / O terminal 30 LCD display 40 Power supply control circuit 42 Common constant voltage IC
44 1st I / O part 46 2nd I / O part 48 FET

Claims (4)

A vehicle display system comprising: a power supply unit that supplies power to the display unit; and a control unit that receives a signal from an ignition switch and controls the power supply of the display unit,
Switching means disposed in a power supply path from the power supply means to the display means and controlled on and off by the control means;
With
The control means determines whether or not the signal from the ignition switch is noise, and controls the switching means to maintain an on or off state when it is determined that the signal is noise. Display system.   The display system according to claim 1, wherein the control unit controls the switching unit from an on state to an off state, and then transitions the operation state of the control unit to a sleep mode. The power supply means supplies power to the display means and the control means,
3. The display system according to claim 1, wherein the switching unit is arranged at a subsequent stage where a power supply path from the power supply unit branches to each of the display unit and the control unit. The control means includes
When the ignition switch is on and the switching means is on,
The switching means is maintained in an on state when the ignition switch shifts to an off state and a signal from the ignition switch is determined to be noise. Display system described.

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