JP2017140888A - On-vehicle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to contribute for elongation of a time of drive by a backup power source of an on-vehicle device comprising the backup power source.SOLUTION: An on-vehicle device M1 comprises: a converter for transforming an external power source B; a first load circuit 2a and a second load circuit 2b to which electric power source is supplied from the converter; and a backup power source 3 which supplies an electric power source to the converter in the place of the external power source B when the external power source B is blocked. In the on-vehicle device, detection means 4 which detects changeover of a power source supply source of the converter, and blocking means 5 which blocks power source supply to the second load circuit 2b when changeover from the external power source B to the backup power source 3 is detected by the detection means 4 are provided. Because of such a configuration, electrical connection of the second load circuit 2b is blocked when changing to the backup power source 3, whereby electric charges reserved by the backup power source 3 are not consumed by the second load circuit 2b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an in-vehicle device provided with a backup power source.

  As a conventional in-vehicle device, there is one disclosed in Patent Document 1. This vehicle-mounted device drives the booster circuit when the voltage supplied to the load circuit becomes less than a predetermined value in order to lengthen the drive time during which the load circuit is supplied with the backup power supply.

JP, 2014-210511, A

  However, the in-vehicle device disclosed in Patent Document 1 has a problem that when the size of the load circuit to be driven by the backup power source increases, the time that can be driven by the backup power source is shortened.

  An object of the present invention is to contribute to a longer driving time of a vehicle-mounted device provided with a backup power source.

The in-vehicle device according to the present invention is
A converter that transforms an external power supply;
A first load circuit and a second load circuit supplied with power from the converter;
A backup power supply that supplies power to the converter instead of the external power supply when the external power supply is shut off,
Detecting means for detecting switching of a power supply source of the converter;
And a means for shutting off the power supply to the second load circuit when switching from the external power source to the backup power source is detected by the detecting means.

The on-vehicle device according to the present invention is
The first load circuit has the detection means;
It is preferable to configure as described above.

Further, the detection means of the in-vehicle device according to the present invention detects switching to the backup power source by a voltage drop of the external power supply or a voltage drop of another power supply different from the external power supply.
It is preferable to configure as described above.

Further, the backup power source of the in-vehicle device according to the present invention is an electrolytic capacitor that is provided between the external power source and the converter and stores electricity by the external power source,
The backup power source has a predetermined capacitance for driving the first load circuit for a period of less than 150 milliseconds,
It is preferable to configure as described above.

  ADVANTAGE OF THE INVENTION According to this invention, it contributes to the prolongation of the drive time by the backup power supply of the vehicle-mounted apparatus provided with the backup power supply.

The figure which shows the electrical constitution of 1st Embodiment of this invention. The figure which shows the electrical constitution of 2nd Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
A vehicle-mounted device M1 according to the first embodiment of the present invention will be described below with reference to FIG.

  The in-vehicle device M1 is supplied with power from the battery power source (external power source) B, and detects that the ignition switch is turned on by the voltage of the ignition power source (other power source) IG supplied in conjunction with the ignition switch. It is an instrument mounted on the instrument panel of the vehicle that displays various vehicle information such as the traveling speed of the vehicle and the engine speed.

  The in-vehicle device M1 includes a converter 1, load circuits 2a and 2b, a backup power supply 3, an NPN transistor (detection means) 4, and a field effect transistor (cut-off means) 5.

  The converter 1 is a DC / DC converter that transforms an input DC power supply to a predetermined voltage and supplies a stable DC power supply. The converter 1 is configured by a switching regulator that is driven by, for example, a PWM (pulse width modulation) method or a PFM (pulse period modulation) method.

  The converter 1 transforms the 8 to 16V power supplied from the battery power source B to 5V and supplies the power to the load circuit (first load circuit) 2a and the load circuit (second load circuit) 2b.

  The load circuit 2a includes, for example, a CPU, a ROM (nonvolatile memory) that stores a program operated by the CPU, a RAM (volatile memory) that stores a result calculated by the CPU, a timer that measures time, Control means for controlling an in-vehicle device such as a microcontroller having an input / output port. The load circuit 2a includes a CAN transceiver IC circuit connected to an in-vehicle LAN such as a controller area network (CAN) (not shown), and inputs various types of vehicle information such as a vehicle traveling speed and an engine speed. The load circuit 2a displays various vehicle information on the load circuit 2b while the ignition power supply IG is input and the ignition switch is turned on.

  The load circuit 2b includes, for example, a light source such as an LED, and a liquid crystal display panel in which polarizing plates are attached to both front and rear surfaces of a liquid crystal cell in which a liquid crystal layer is sealed in a pair of translucent substrates on which a transparent electrode film is formed. It is a display means such as an integrated thin film transistor type color liquid crystal module. The load circuit 2b is controlled by the load circuit 2a and displays various vehicle information as images.

  Backup power supply 3 supplies power to converter 1 instead of battery power supply B when battery power supply B is cut off. The backup power source 3 is, for example, an electrolytic capacitor provided between the converter 1 and the battery power source B, stores a predetermined electrostatic charge while the battery power source B is supplied, and the battery power source B is cut off. Then, the stored charge is discharged to the converter 1. The backup power supply 3 has a predetermined capacitance that can hold the contents held in the RAM (volatile memory) of the load circuit 2a when the battery power supply B is momentarily interrupted. The predetermined electrostatic capacity is, for example, an electrostatic capacity that can drive the load circuit 2a for 50 to 150 milliseconds.

  The detection means 4 is a detector that detects switching of the power supply source of the converter 1. The detecting means 4 is, for example, an NPN transistor having an ignition power source IG connected to the base terminal and an emitter terminal connected to the ground. In the detection means 4, a current flows through the collector terminal while the ignition power supply IG is on. Since the voltage of the ignition power supply IG drops with the interruption of the battery power supply B, when the power supply source of the converter 1 is switched from the battery power supply B to the backup power supply 3, no current flows through the collector terminal. Thus, the detection means 4 detects the switching of the power supply source of the converter 1 by the voltage change of the ignition power supply IG.

  The shut-off means 5 is a shut-off circuit that turns on / off the power supply from the converter 1 to the load circuit 2b according to the result of the detection means 4 detecting the switching of the power supply source of the converter 1. The blocking means 5 is, for example, a field effect transistor having the source 1 connected to the converter 1, the drain terminal connected to the load circuit 2 b, and the gate terminal connected to the collector terminal of the detection means 4. While the current from the collector terminal of the detection means 4 flows to the gate terminal of the cutoff means 5, power is supplied from the converter 1 to the load circuit 2 b, and the gate terminal of the cutoff means 5 is connected to the gate terminal of the detection means 4. When the current no longer flows, the power supply from the converter 1 to the load circuit 2b is cut off. The blocking means 5 is not limited to a field effect transistor, and can be composed of various switching circuits.

As described above, the in-vehicle apparatus M1 according to the first embodiment includes the converter 1 that transforms the external power supply B, the first load circuit 2a and the second load circuit 2b that are supplied with power from the converter 1, and the external power supply B. And a backup power source 3 that supplies power to the converter 1 instead of the external power source B when the power source is shut off, and a detection means 4 that detects switching of the power supply source of the converter 1, and a detection When the switching from the external power source B to the backup power source 3 is detected by the unit 4, a blocking unit 5 is provided for blocking the power supply to the second load circuit 2b.
With this configuration, since the electrical connection of the second load circuit 2b is interrupted when switching to the backup power supply 3, the charge stored in the backup power supply 3 is not consumed by the second load circuit 2b. Therefore, it is possible to contribute to a longer driving time of the in-vehicle device by the backup power source 3.
In particular, when the battery power supply B is momentarily interrupted or when the voltage of the battery power supply B drops when the vehicle is cranked, the backup power supply 3 having a small capacitance and the RAM (volatile memory) of the first load circuit 2a Since the contents can be held, the electrical robustness of the system of the in-vehicle device M1 can be enhanced with an inexpensive configuration.

(Second Embodiment)
Next, the in-vehicle device M2 of the second embodiment will be described below with reference to FIG. In the following description, differences from the in-vehicle device M1 of the first embodiment will be described.

  The load circuit 2a of the in-vehicle device M2 determines whether the power supply source of the converter 1 is the battery power supply B or the backup power supply 3 based on the input voltage of the ignition power supply IG. When the power supply source of the converter 1 is the battery power source B, the load circuit 2a controls the power to be supplied from the converter 1 to the load circuit 2b by causing a current to flow through the gate terminal of the cutoff means 5. When the power supply source of the converter 1 is the backup power supply 3, the load circuit 2 a controls the power supply from the converter 1 to the load circuit 2 b without passing a current through the gate terminal of the cutoff means 5. .

As in the in-vehicle device M2 that is the second embodiment described above, the control means that is the load circuit 2a may detect that the power supply source of the converter 1 has been switched from the battery power supply B to the backup power supply 3.
In this configuration, since the load circuit 2a also functions as the detection means 4, it contributes to a reduction in the cost of the in-vehicle device.

  The present invention is not limited to the first and second embodiments described above (including the contents of the drawings). Modifications (including deletion of constituent elements) can be added to the above-described embodiment within the scope of the gist of the present invention.

In the in-vehicle device M1 of the first embodiment and the in-vehicle device M2 of the second embodiment described above, the detection unit 4 detects the switching to the backup power source 3 due to the voltage drop of the ignition power source (other power source) IG. The detection means 4 of the present invention is not limited to this, and may be configured to detect the voltage drop of the battery power source (external power source) B.
In this case, depending on the configuration of the load circuit 2b, the dark current during the period when the ignition switch is off tends to be high, but the switching to the backup power source 3 can be accurately detected.

Further, although the load circuit 2a is a control unit that controls the vehicle-mounted device such as a microcontroller as a whole, and the load circuit 2b is a display unit such as a thin film transistor type color liquid crystal module, the present invention is not limited to this.
The load circuit 2a only needs to include at least a control unit that controls the vehicle-mounted device in an integrated manner. The larger the power consumption of the load circuit 2b, the longer the drive time of the vehicle-mounted device by the backup power supply 3 can be increased. .

  For example, the load circuit 2b in which the power supply is cut off by the shut-off means 5 is an LED that is a light source of a warning light that displays various vehicle information, a stepping motor that rotates a pointer that indicates various vehicle information, or a pointer It may be an LED serving as an illumination light source for a dial on which an index is formed, or a speaker for notifying various vehicle information by sound.

  The second load circuit may be a circuit that inputs various types of vehicle information to the first load circuit 2a. For example, it is a CAN transceiver IC circuit for inputting / outputting in-vehicle LAN signals to / from the microcontroller of the load circuit 2a.

  Moreover, when the vehicle-mounted device is a head-up display device that displays a virtual image, it is preferable that the load circuit 2b be a drive circuit for adjusting the display position of the virtual image. The drive circuit for adjusting the display position of the virtual image is, for example, a stepping motor that rotates a plane mirror or a concave mirror.

  The present invention is suitable for an in-vehicle device mounted on a vehicle.

M1, M2: On-vehicle device B: Battery power (external power)
IG: Ignition power supply (other power supplies)
1: Converter 2a: First load circuit 2b: Second load circuit 3: Backup power supply 4: Detection means 5: Shut-off means

Claims (4)

A converter that transforms an external power supply;
A first load circuit and a second load circuit supplied with power from the converter;
A backup power supply that supplies power to the converter instead of the external power supply when the external power supply is shut off,
Detecting means for detecting switching of a power supply source of the converter;
A shut-off means for shutting off the power supply to the second load circuit when the switching from the external power supply to the backup power supply is detected by the detection means;
In-vehicle device characterized by the above. The first load circuit has the detection means;
The in-vehicle device according to claim 1. The detection means detects a switch to the backup power supply by a voltage drop of the external power supply or a voltage drop of another power supply different from the external power supply;
The in-vehicle device according to claim 1 or 2, characterized by the above-mentioned. The backup power source is an electrolytic capacitor that is provided between the external power source and the converter and stores electricity by the external power source,
The backup power source has a predetermined capacitance for driving the first load circuit for a period of less than 150 milliseconds,
The in-vehicle device according to any one of claims 1 to 3, wherein

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