JP6164463B2 - Power supply circuit for vehicle display device - Google Patents

Description

  The present invention relates to a power supply circuit for a display device for a vehicle, and is particularly suitable for a power supply circuit for a display device for a vehicle that supplies power for driving a load circuit from a battery.

  As a conventional vehicle display device, in order to display time and maintenance information, there is one that is subjected to arithmetic processing such as counting time of various conditions such as time, vehicle operating time, and parts replacement time. It is disclosed in Patent Document 1.

  In addition, in a vehicle display device, even when power is not supplied from an in-vehicle battery or the like, a backup battery is used to perform operations such as timekeeping or to retain the storage contents of a storage medium. Is disclosed in, for example, Patent Document 2.

JP-A-5-319139 Japanese Patent Laid-Open No. 10-239086

  In such a vehicle display device, the voltage output from the battery may decrease due to the low temperature environment as well as the consumption of the battery. Therefore, the voltage for driving the load circuit cannot be secured. Since necessary processing of the vehicle display device may not be performed, a power supply circuit that drives the load circuit for as long as possible even at low temperatures has been desired.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power supply circuit for a vehicle display device capable of extending the driving time of a load circuit using a battery, paying attention to the above-described problems.

The power supply circuit of the vehicle display device of the present invention is
A battery serving as a power source for the load circuit;
A backup capacitor connected in a chargeable / dischargeable manner between the load circuit and the battery;
Boosting means for boosting the voltage of the battery and charging the capacitor;
Control means for detecting a voltage supplied to the load circuit and controlling the boosting means to perform a boosting operation when the voltage is less than a predetermined threshold;
A constant voltage power supply unit that steps down and outputs power supplied from the vehicle battery;
Switch means for connecting the battery and the boosting means having a higher potential to the backup capacitor when a predetermined voltage is not generated in the constant voltage power supply section when connected to the constant voltage power supply section ,
It is characterized by providing.

In addition, when the vehicle is operating, power is supplied from the in-vehicle battery to the load circuit, and when the vehicle is not operating, power is supplied from the battery to the load circuit.

The load circuit is a circuit for calculating time or maintenance information of the vehicle, and includes a display unit that performs display based on the maintenance information when the vehicle is in operation.

  The present invention relates to a power supply circuit for a display device for a vehicle, and can increase the drive time of a load circuit using a battery.

The figure which shows the circuit structure in embodiment of this invention. The figure shown about the operation example based on the various signals of embodiment same as the above. The figure which shows the other example of the circuit structure in embodiment of this invention. The figure shown about the operation example based on the various signals of embodiment same as the above (another example).

  Hereinafter, as an embodiment of the present invention, an example applied to a vehicle instrument will be described with reference to the drawings.

  The vehicle meter M notifies a vehicle user of a measured value (vehicle state) detected by various sensors using a vehicle battery and a battery as a driving power source. For example, a vehicle speed meter, a fuel fuel gauge, and the like are used. I have. Further, in this case, the vehicle meter M has a function of notifying maintenance means such as replacement time of each part such as engine oil and filter of the vehicle on a display means (not shown) such as a liquid crystal display panel or a clock notifying the time. I have.

  As shown in FIG. 1, the vehicle meter M includes a constant voltage power source unit 1, a battery 2, a switch unit 3, a booster circuit unit (boost unit) 4, a low voltage detector unit (control unit) 5, A backup capacitor circuit unit 6 and a backed up circuit unit (load circuit) 7 are provided, and are connected to the vehicle-mounted battery V via a start switch (ignition switch) S.

  The constant voltage power supply unit 1 is connected to the switch means 3, and when an in-vehicle battery (for example, 8 to 14V) V is connected, the power supplied from the in-vehicle battery V is stepped down, and the backed up circuit unit 7 A predetermined voltage (for example, 3 V) corresponding to the operating voltage of the current can be generated and output to the backed up circuit unit 7 via the switch means 3. The constant voltage power supply unit 1 and the in-vehicle battery V are connected via a start switch S.

  The battery 2 is a primary battery such as a lithium battery, and is connected to the backup capacitor circuit unit 6 via the booster circuit unit 4 and supplies electric charges so that the backup capacitor circuit unit 6 maintains a potential higher than a certain level. Note that the battery 2 is provided with an output voltage and a capacity selected to operate the backed-up circuit unit 7 serving as a load circuit for several years even when the vehicle-mounted battery V is not connected.

  The switch means 3 connects the constant voltage power supply unit 1 and the backup capacitor circuit unit 6 when a predetermined voltage is generated in the constant voltage power supply unit 1, and the predetermined voltage is generated in the constant voltage power supply unit 1. If not, the higher one of the potential of the battery 2 and the boosted potential of the booster circuit unit 4 is connected to the backup capacitor circuit unit 6.

  The switch means 3 can be configured by a logic circuit using transistors or FETs, but simply sets the output voltage of the constant voltage power supply unit 1 higher than the normal potential of the battery 2 using a diode circuit. Thus, priority can be given to connection from the constant voltage power supply unit 1 to the backup capacitor circuit unit 6, and consumption of the battery 2 can be reduced.

  The booster circuit unit 4 is composed of a charge pump power supply circuit that can operate at a low voltage, and repeats operation / non-operation intermittently according to the ON / OFF state of the enable signal b of the low voltage detection unit 5, and the enable signal b is in the ON state. In this case, a predetermined boosted potential is applied to the backup capacitor circuit unit 6.

  The low voltage detection unit 5 is configured by a low current consumption reset IC or the like, and when the low potential of the backup capacitor circuit unit 6 is detected, the enable signal b is turned on for a certain time with respect to the boost circuit unit 4. .

  Therefore, the low voltage detection unit 5 determines that the potential a of the backup capacitor circuit unit 6 is lower than that of the backed up circuit unit 7 because, for example, the potential c of the battery 2 cannot be sufficiently obtained when the battery 2 is cold. When the operating voltage (for example, 2 V) or higher, current is supplied from the battery 2 to the backup capacitor circuit unit 6, and the potential a of the backup capacitor circuit unit 6 becomes less than the minimum operating voltage of the backed up circuit unit 7. In this case, the booster circuit unit 4 is controlled so that a current is supplied from the booster circuit unit 4 to the backup capacitor circuit unit 6.

  The backup capacitor circuit unit 6 includes a capacitor 61 for temporarily storing electric charge and a current limiting resistor 62 arranged in series with the capacitor 61, and gives a backup potential to the backed up circuit unit 7. Therefore, even if the power supply from the booster circuit unit 4 is intermittent due to charging / discharging of the capacitor 61, a voltage sufficient for driving the backed up circuit unit 7 can be supplied. Further, since the booster circuit unit 4 does not have to be continuously driven, the current consumption of the booster circuit unit 4 can be suppressed.

  The backed-up circuit unit 7 is connected to the backup capacitor circuit unit 6 and can be applied with a storage unit for storing maintenance information or a time measuring unit for counting time. Even if it is not, it is possible to perform storage maintenance of information or timing processing. In this case, it is configured so that it can be calculated as a separate process from the normal display process.

  Such a vehicle meter M includes a battery 2 serving as a power source for the backed up circuit unit 7, a backup capacitor 61 connected between the backed up circuit unit 7 and the battery 2 in a chargeable / dischargeable manner, The boosting circuit unit 4 that boosts the voltage to charge the capacitor 61 and the voltage supplied to the backed up circuit unit 7 are detected, and when the voltage is less than a predetermined threshold (for example, less than 2V), the boosting circuit unit 4 A low-voltage detector 5 that controls to perform a boosting operation.

Therefore, for example, even when the voltage output from the battery 2 is reduced due to the consumption of the battery 2 or the low temperature environment, the boosted circuit unit 4 operates the backed up circuit unit 7 serving as a load circuit with an appropriate driving voltage. it can. Further, by intermittently operating the booster circuit unit 4 , current consumption can be reduced, and a power supply circuit for driving the backed up circuit unit 7 for as long as possible is obtained. That is, it becomes a power supply circuit of the display device for vehicles which can lengthen the drive time of the load circuit by the battery 2 .

Further, when the vehicle is operating, power is supplied from the in-vehicle battery V to the backed-up circuit unit 7, and when the vehicle is not operating, power is supplied from the battery 2 to the backed-up circuit unit 7. Thus, the battery 2 can be prevented from always consuming power, and the load circuit can be driven by the battery 2 for a longer period.

  In addition, although the power supply circuit of the vehicle display device of the present invention has been described as an example in the configuration of the above-described embodiment, the present invention is not limited to this, and the present invention is also applied to other configurations. It goes without saying that various improvements and display changes can be made without departing from the gist of the invention.

  The present invention can be applied to a power supply circuit of a display device for a vehicle mounted on a moving object including an automobile, a motorcycle, an agricultural machine, or a construction machine, for example, regarding the display device for a vehicle.

DESCRIPTION OF SYMBOLS 1 Constant voltage power supply part 2 Battery 3 Switch means 4 Booster circuit part (boost means)
5 Low voltage detector (control means)
6 Backup capacitor circuit part 61 Capacitor 7 Backed up circuit part (load circuit)
M Vehicle instrument S Start switch V Car battery

Claims (3)

A battery serving as a power source for the load circuit;
A backup capacitor connected in a chargeable / dischargeable manner between the load circuit and the battery;
Boosting means for boosting the voltage of the battery and charging the capacitor;
Control means for detecting a voltage supplied to the load circuit and controlling the boosting means to perform a boosting operation when the voltage is less than a predetermined threshold;
A constant voltage power supply unit that steps down and outputs power supplied from the vehicle battery;
Switch means for connecting the battery and the boosting means having a higher potential to the backup capacitor when a predetermined voltage is not generated in the constant voltage power supply section when connected to the constant voltage power supply section ,
A power supply circuit for a vehicle display device. The power is supplied from the in-vehicle battery to the load circuit when the vehicle is operating, and the power is supplied from the battery to the load circuit when the vehicle is not operating. The power supply circuit of the display apparatus for vehicles as described. The load circuit is a circuit for computing time or vehicle maintenance information, and includes a display means for performing display based on the maintenance information when the vehicle is in operation. The power supply circuit of the display apparatus for vehicles of 2.

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