Vehicle display device

Abstract

To provide a display device for vehicle, which can suppress capacitance or the number of capacitors.SOLUTION: A display device for vehicle 1 includes: a main component group 3; a non-main component group 4; a surge protection circuit 2 which is electrically connected between a power supply input terminal BAT, and the main component group 3 and the non-main component group 4, and stops supply of surge current to the main component group 3 and the non-main component group 4 when surge current is generated; capacitors 5a and 5b which are electrically connected between the protection circuit 2 and the main component group 3 and hold power supply to the main component group 3 on the basis of accumulated charge when power supply from the power supply input terminal BAT is interrupted; a reverse connection protection diode 10 having an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to ground; and a reverse connection protection diode 20 having the anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the main component group 3 and the capacitors 5a and 5b.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a display device for a vehicle.

Background Art

[0002] For example, the surge protection circuit of the vehicle instrument described in Patent Document 1 includes a diode for protecting against reverse connection of the battery, switch means that turns off when an overcurrent is detected to stop power supply to the load, and a capacitor for holding power when the power supply is cut off.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration described in Patent Document 1 above, the capacitor needs to hold the power supply to the load when the power supply is temporarily cut off. For this reason, it was necessary to increase the capacitance of the capacitor or provide a large number of capacitors.

[0005] The present disclosure has been made in view of the above actual situation, and an object thereof is to provide a display device for a vehicle that can suppress the capacitance or the number of capacitors.

Means for Solving the Problems

[0006] To achieve the above objective, the vehicle display device according to this disclosure comprises: a first load; a second load; a surge protection circuit electrically connected between a power input terminal and the first and second loads, which stops or limits the supply of surge current or surge voltage to the first and second loads when a surge current or surge voltage occurs; a capacitor electrically connected between the surge protection circuit and the first load, which stores charge by the current passing through the surge protection circuit, and maintains power supply to the first load based on the stored charge when the power supply from the power input terminal is momentarily interrupted; a first reverse protection diode having an anode terminal connected to the surge protection circuit and a cathode terminal connected to ground; and a second reverse protection diode having an anode terminal connected to the surge protection circuit and a cathode terminal connected to the first load and the capacitor, respectively. [Effects of the Invention]

[0007] According to this disclosure, the capacitance or number of capacitors in a vehicle display device can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a circuit diagram of a vehicle display device according to one embodiment of the present disclosure. [Figure 2] This is a circuit diagram of a vehicle display device relating to a modified example of the present disclosure. [Modes for carrying out the invention]

[0009] A vehicle display device according to one embodiment of this disclosure will be described with reference to the drawings. In this embodiment, the vehicle display device is mounted on a vehicle including automobiles, construction machinery, agricultural machinery, and motorcycles.

[0010] As shown in Figure 1, the vehicle display device 1 comprises a main component group 3, a non-main component group 4, a surge protection circuit 2, capacitors 5a and 5b, a switch circuit 6, reverse protection diodes 10, 20, 30, and 40, a power input terminal BAT, a ground terminal GND, and an accessory terminal ACC.

[0011] The main component group 3 is a group of components that are preferably able to operate even when there is a momentary voltage drop, such as when the vehicle is cranking. The main component group 3 is a group of components that take longer to recover when the power supply is momentarily interrupted than the non-main component group 4. The main component group 3 is composed of multiple first loads. The main component group 3 includes, for example, a microcontroller 3a, a display driver 3b that drives a TFT (Thin Film Transistor) type liquid crystal panel, a touch panel driver 3c, a communication IC (Integrated Circuit) 3d for communication with the vehicle ECU (Electronic Control Unit), and a non-volatile memory 3e. The communication IC 3d is a deserializer or a CAN (Control Area Network) transceiver, etc.

[0012] The non-main component group 4 consists of components that do not immediately deteriorate in function even if there is a momentary voltage drop, such as a momentary power interruption, during vehicle cranking or other similar events. The non-main component group 4 is composed of multiple second loads. The non-main component group 4 includes, for example, a speaker 4a that emits sound, a backlight circuit 4b, and a light source driver 4c that drives an LED (Light Emitting Diode) to illuminate the liquid crystal panel.

[0013] The microcontroller 3a comprises a CPU (Central Processing Unit) and a GDC (Graphics Display Controller) and controls the entire vehicle display device 1. The microcontroller 3a displays an image on the liquid crystal panel via the display driver 3b, and then illuminates an LED via the light source driver 4c, thereby emitting light onto the liquid crystal panel. In addition, the microcontroller 3a emits a beep sound or voice via the speaker 4a in conjunction with the image display on the liquid crystal panel.

[0014] As shown in Figure 1, the power input terminal BAT is the terminal that receives voltage from the vehicle's battery. The ground terminal GND is connected to ground. The accessory terminal ACC is the terminal that receives the accessory signal Sacc. The accessory signal Sacc is a signal supplied from the ignition switch (not shown) installed in the vehicle.

[0015] The surge protection circuit 2 is electrically connected to the power input terminal BAT, the accessory terminal ACC, ground, the main component group 3, and the non-main component group 4. When the surge protection circuit 2 receives a drive current Ia from the battery via the power input terminal BAT to drive the components, it supplies the drive current Ia to the main component group 3 and the non-main component group 4. When the surge protection circuit 2 receives a surge current Isg from the battery via the power input terminal BAT, it directs the surge current Isg to ground via the reverse-connection protection diode 10 and the switch circuit 6. This stops or limits the supply of the surge current Isg to the main component group 3 and the non-main component group 4. The surge protection circuit 2 includes, for example, a Zener diode, a FET (Field Effect Transistor), and a transistor (none of which are shown in the diagram). When a surge voltage exceeding the Zener voltage is applied from the power input terminal BAT, the FET is turned off, causing the surge current Isg to flow to ground via the reverse-connection protection diode 10 and the switch circuit 6.

[0016] Switch circuit 6 is connected to the accessory terminal ACC, surge protection circuit 2, and ground. Switch circuit 6 includes a transistor that conducts or blocks the current path between surge protection circuit 2 and ground. Switch circuit 6 is in the ON state when the accessory signal Sacc is ON, and in the OFF state when the accessory signal Sacc is OFF. When switch circuit 6 is ON, the current path from surge protection circuit 2 to ground is open, and surge protection circuit 2 becomes operational. On the other hand, when the switch circuit 6 is in the off state, the current path flowing from the surge protection circuit 2 to the ground is interrupted. As a result, when the accessory signal Sacc is off, the leakage current flowing from the surge protection circuit 2 to the ground is interrupted.

[0017] The microcontroller 3a has an on-holding unit that maintains the switch circuit 6 in the on state for a certain period of time after the accessory signal Sacc switches from on to off, and switches the switch circuit 6 from the on state to the off state after the elapse of this certain period of time. This certain period of time is set to the period during which a surge current Isg may occur after the accessory signal Sacc switches from on to off.

[0018] The reverse connection protection diode 10 includes an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the ground via the switch circuit 6. The reverse connection protection diode 10 interrupts the current flowing backward from the switch circuit 6 when the battery is reversely connected to the power supply and the ground.

[0019] The reverse connection protection diode 20 includes an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the main component group 3 and the capacitors 5a and 5b. The reverse connection protection diode 20 interrupts the current flowing backward from the main component group 3 and the capacitors 5a and 5b when the battery is reversely connected. The reverse connection protection diode 20 is an ideal diode with a forward voltage of zero, which is composed of a circuit using an FET or an IC. Thereby, the voltage drop caused by the reverse connection protection diode 20 can be suppressed.

[0020] The reverse connection protection diode 30 includes an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the non-main component group 4. The reverse connection protection diode 30 interrupts the current flowing backward from the non-main component group 4 when the battery is reversely connected. The reverse connection protection diode 30 is an ideal diode with a forward voltage of zero, which is composed of a circuit using an FET or an IC. Thereby, the voltage drop caused by the reverse connection protection diode 30 can be suppressed.

[0021] The reverse connection protection diode 40 includes an anode terminal connected to the accessory terminal ACC and a cathode terminal connected to the switch circuit 6. The reverse connection protection diode 40 blocks the current flowing backward from the switch circuit 6 when the battery is reversely connected.

[0022] A plurality of, in this example, two capacitors 5a and 5b are electrically connected between the reverse connection protection diode 20 and the main component group 3. The capacitors 5a and 5b are electrolytic capacitors respectively. Each of the capacitors 5a and 5b is configured to be able to store a charge that can maintain the power supply to the main component group 3 during an instantaneous interruption of power associated with the cranking of the vehicle. For example, the capacitance of each of the capacitors 5a and 5b is, for example, 220 μF. The plus sides of the capacitors 5a and 5b are electrically connected to the main component group 3. The minus sides of the capacitors 5a and 5b are electrically connected to the ground. The capacitors 5a and 5b receive the current passing through the surge protection circuit 2 input via the power input terminal BAT and store the charge. The capacitors 5a and 5b maintain the power supply to the main component group 3 based on the stored charge when there is an instantaneous interruption of the input voltage applied to the power input terminal BAT. Note that the number of the capacitors 5a and 5b is not limited to two, and may be three or more or one. Also, at least one of the capacitors 5a and 5b is not limited to an electrolytic capacitor, and may be a ceramic capacitor.

[0023] Next, the operation of the vehicle display device 1 will be described. When the ignition switch (not shown) is operated and the accessory signal Sacc is switched from off to on, the switch circuit 6 is turned on, and thereby the surge protection circuit 2 is turned on. As a result, the current input from the power input terminal BAT is supplied to the main component group 3 through the surge protection circuit 2 and via the reverse connection protection diode 20, and is also supplied to the non-main component group 4 via the reverse connection protection diode 30. At this time, the capacitors 5a and 5b store the charge so that the main component group 3 can continue to operate during a temporary voltage drop such as the cranking of the vehicle.

[0024] During this temporary voltage drop, capacitors 5a and 5b supply power only to the main component group 3 and not to the non-main component group 4. In this case, the reverse-connection protection diode 20 limits the power supply to the non-main component group 4 based on the charge stored in capacitors 5a and 5b. Therefore, the consumption of the charge stored in capacitors 5a and 5b by the non-main component group 4 is suppressed.

[0025] (effect) According to the embodiment described above, the following effects are achieved. (1) The vehicle display device 1 comprises a main component group 3 which is an example of a plurality of first loads, a non-main component group 4 which is an example of a plurality of second loads, a surge protection circuit 2 which is electrically connected between the power input terminal BAT and the main component group 3 and the non-main component group 4 and stops or limits the supply of surge current Isg to the main component group 3 and the non-main component group 4 when a surge current Isg occurs, capacitors 5a and 5b which are electrically connected between the surge protection circuit 2 and the main component group 3 and store charge by the current that passes through the surge protection circuit 2, and maintain power supply to the main component group 3 based on the stored charge when the power supply from the power input terminal BAT is momentarily interrupted, a reverse protection diode 10 which is an example of a first reverse protection diode having an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to ground, and a reverse protection diode 20 which is an example of a second reverse protection diode having an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the main component group 3 and capacitors 5a and 5b respectively. In this configuration, capacitors 5a and 5b supply the stored charge as power only to the main component group 3 during a temporary voltage drop at the power input terminal BAT, and not to the non-main component group 4. In this way, power retention for the non-main component group 4 by capacitors 5a and 5b becomes unnecessary, and the capacitance or number of capacitors 5a and 5b can be reduced. Furthermore, the reverse-connection protection diode 10 is provided on the ground side of the surge protection circuit 2, rather than on the input side. Therefore, only one diode is needed to connect between the power input terminal BAT and the main component group 3. Thus, voltage drop due to the diode can be suppressed.

[0026] (2) The vehicle display device 1 includes a switch circuit 6 electrically connected between the cathode terminal of the reverse-connected protection diode 10 and ground, an accessory terminal ACC which is an example of a signal input terminal to which an accessory signal Sacc, which is an example of a power signal indicating the on / off state of the power supply of the vehicle display device 1, is input, and a reverse-connected protection diode 40 which is an example of a third reverse-connected protection diode having an anode terminal connected to the accessory terminal ACC and a cathode terminal connected to the switch circuit 6. The switch circuit 6 interrupts the current path flowing from the surge protection circuit 2 to ground when the accessory signal Sacc is off. With this configuration, the switch circuit 6 suppresses the flow of dark current from the surge protection circuit 2 to ground when the accessory signal Sacc is turned off.

[0027] (3) The vehicle display device 1 includes a reverse-connection protection diode 30, which is an example of a fourth reverse-connection protection diode having an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to the non-main component group 4. With this configuration, the reverse-connection protection diode 30 can block the current flowing back from the non-main components group 4 when the battery is connected in reverse.

[0028] (4) The main component group 3 includes the microcontroller 3a. The non-main component group 4 includes the speaker 4a. For example, if the power supply to the microcontroller 3a is momentarily interrupted, it takes time for the microcontroller 3a to recover. However, if the power supply to the speaker 4a is momentarily interrupted, the sound will only be temporarily cut off, and no recovery process is required. Therefore, it is preferable that the power supply to the microcontroller 3a is maintained more by capacitors 5a and 5b than that to the speaker 4a during a temporary voltage drop.

[0029] This disclosure is not limited to the embodiments and drawings described above. Modifications (including the deletion of components) can be made as appropriate, provided they do not alter the essence of this disclosure. An example of such a modification is described below.

[0030] (modified version) In the above embodiment, the vehicle display device 1 was equipped with a switch circuit 6, but it is not limited to this, and the switch circuit 6 may be omitted.

[0031] As shown in Figure 2, the vehicle display device 1 may, in addition to the configuration of the above embodiment, also include a component 8, which is an example of a third load, a capacitor 5c, and a reverse-connection protection diode 50. The reverse-connection protection diode 50 includes an anode terminal connected to the surge protection circuit 2 and a cathode terminal connected to component 8. The reverse-connection protection diode 50 blocks the current flowing back from component 8 when the battery is reverse-connected. The reverse-connection protection diode 50 is an ideal diode with a forward voltage of zero, consisting of a circuit using an FET or IC. Component 8 is a load that requires a constant power supply, such as a clock. The capacitor 5c supplies power to component 8 when there is a power loss, such as when replacing the battery. Capacitor 5c is set to have a slower discharge rate and a smaller discharge current than capacitors 5a and 5b.

[0032] The positions or number of reverse-connection protection diodes 10, 20, 30, and 40 in the above embodiment can be changed as appropriate. In the above embodiment, the types of loads (components) belonging to the main component group 3 and the types of loads (components) belonging to the non-main component group 4 can be changed as appropriate. For example, the light source driver 4c may belong to the main component group 3. Alternatively, for example, loads with high power consumption may belong to the main component group 3, and loads with low power consumption may belong to the non-main component group 4.

[0033] In the above embodiments and modifications, the reverse-connection protection diodes 20, 30, and 50 were all ideal diodes. However, at least one of the reverse-connection protection diodes 20, 30, and 50 may be a conventional diode, which is a discrete component rather than an ideal diode. [Explanation of symbols]

[0034] 1. Vehicle display device 2. Surge protection circuit 3 Main parts group 3a Microcontroller 3b Display driver 3c touch panel driver 3d communication IC 3e Non-volatile memory 4 Non-main parts group 4a speaker 4b Backlight Circuit 4c light source driver 5a, 5b, 5c Capacitors 6 Switch Circuits 8 parts 10, 20, 30, 40, 50 Reverse-connection protection diodes ACC accessory terminal BAT Power Input Terminal GND ground terminal Ia Drive current ISG surge current Sacc accessory signal

Claims

1. First load and, Second load and, A surge protection circuit is electrically connected between the power input terminal and the first and second loads, and stops or limits the supply of surge current or surge voltage to the first and second loads when a surge current or surge voltage occurs. A capacitor is electrically connected between the surge protection circuit and the first load, stores charge by the current passing through the surge protection circuit, and maintains power supply to the first load based on the stored charge during a momentary interruption of power supply from the power input terminal. A first reverse-connected protection diode having an anode terminal connected to the surge protection circuit and a cathode terminal connected to ground, The surge protection circuit includes a second reverse-connection protection diode having an anode terminal connected to the surge protection circuit and a cathode terminal connected to the first load and the capacitor, respectively. Vehicle display device.

2. The aforementioned vehicle display device is A switch circuit electrically connected between the cathode terminal of the first reverse protection diode and the ground, A signal input terminal to which a power signal indicating the on / off state of the vehicle display device is input, A third reverse-connection protection diode having an anode terminal connected to the signal input terminal and a cathode terminal connected to the switch circuit, The switch circuit interrupts the current path from the surge protection circuit to the ground when the power signal is turned off. The vehicle display device according to claim 1.

3. The vehicle display device includes a fourth reverse-connected protection diode having an anode terminal connected to the surge protection circuit and a cathode terminal connected to the second load. The vehicle display device according to claim 1 or 2.

4. The first load includes a microcontroller, The second load includes a speaker. The vehicle display device according to claim 1 or 2.

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