JP2004359005A - Vehicular power source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an inexpensive vehicular power source device by simplifying the circuit constitution. <P>SOLUTION: The voltage Vs of a subsidiary battery 13 is set to be lower than the voltage Vm of a main battery 11 by regulating the concentration of an electrolyte liquid in the batteries or providing a pressure reducing element and so forth. Thus, when the voltage having passed through a first filter 21 in a DC/DC converter 17a and a step-down converting section 25 from the main battery 11 is provided for charging the subsidiary battery 13, the increasing of the voltage is not required. Then, a step-up converting section 27 in the DC/DC converter 17a is omitted. Thus, the circuit constitution of the DC/DC converter 17a is simplified, and this inexpensive vehicular power source device is realized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-vehicle power supply device having a sub-battery serving as a backup power supply in addition to a main battery.
[0002]
[Prior art]
A vehicle is generally equipped with a battery, and the voltage from the battery is supplied not only to basic functions such as power steering and an electronically controlled suspension, which are essential for driving the vehicle, but also to various electronic devices such as audio and car navigation. It is also supplied to the control unit.
[0003]
FIG. 4 is a block diagram showing a general in-vehicle power supply device. The on-vehicle power supply device includes a main battery 11 for supplying power to the load 1 and various electronic control units (ECUs) 3, and a temporary emergency backup power supply when the voltage Vm of the main battery 11 decreases. A sub-battery 13 used as a power source; a generator (AG) 15 for converting the power of rotational driving of the wheels into electric energy when the vehicle is running to provide a regenerative voltage to the main battery 11; A DC / DC converter 17 for stabilizing voltages from the battery 13 and the generator 15; and two contacts for switching the voltage applied to the load 1 between Vm from the main battery 11 and Vs from the sub-battery 13 Type switch 19.
[0004]
Here, as shown in FIG. 5, the DC / DC converter 17 includes first and second noise removal filters 21 and 23 for removing noise in the voltages of the batteries 11 and 13 and each voltage Vm of the main battery 11. It includes a step-down converter 25 for stepping down a voltage and a step-up converter 27 for stepping up and stabilizing when the voltage Vm from the main battery 11 drops.
[0005]
In the above configuration, the step-down converter 25 steps down the voltage Vm (eg, about 14 volts) of the main battery 11 and converts it to a predetermined voltage (eg, 12 to 13 volts). In the case where the voltage of the device decreases, the voltage is boosted for the purpose of stabilizing the voltage. The voltage given from the main battery 11 through the step-down converter 25 and the step-up converter 27 is applied to the sub-battery 13 through the second filter 23 and used for charging the sub-battery 13.
[0006]
Then, the ECU 3 detects the state of the voltage applied from the main battery 11 to the sub-battery 13 via the first filter 21, the step-down converter 25, the step-up converter 27, and the second filter 23. That is, the voltage from the main battery 11 that has passed through the second filter 23 is compared with a predetermined reference voltage 31 by the comparing unit 33, and it is determined whether the voltage of the main battery 11 is normal. Then, in accordance with the result of the determination by the comparison unit 33, the switching control unit 35 controls the operations of the step-down conversion unit 25 and the step-up conversion unit 27 on and off to stabilize the voltage from the main battery 11. When the charge capacity of the main battery 11 decreases and the voltage Vm decreases constantly, the switch 19 is switched to switch the power supply to the load 1 from the main battery 11 to the sub-battery 13. As a result, even if the voltage Vm of the main battery 11 decreases, it is possible to appropriately control the step-down converter 25 and the step-up converter 27 to perform appropriate power management.
[0007]
Reference numerals D1 and D2 in FIG. 4 denote diodes for preventing a backflow of a current flowing through the load 1.
[0008]
No prior art document relating to the above content has been found.
[0009]
[Problems to be solved by the invention]
Since the DC / DC converter 17 shown in FIG. 5 includes both the step-down converter 25 and the step-up converter 27, the circuit is complicated and expensive.
[0010]
Therefore, an object of the present invention is to provide a low-cost in-vehicle power supply device with a simplified circuit configuration.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 includes a main battery for supplying a normal power supply for driving a load, and a temporary emergency backup power supply when a power supply voltage of the main battery is reduced. And a DC / DC converter for stabilizing the voltages of the main battery and the sub-battery to a predetermined voltage level, wherein the voltage of the sub-battery is set lower than the voltage of the main battery. The DC / DC converter is a step-down converter.
[0012]
The invention according to claim 2 is the vehicle-mounted power supply device according to claim 1, wherein charge and discharge are performed in each of the main battery and the sub-battery by a chemical reaction between the electrolyte and the electrolyte. An electrode plate made of an active material to be performed, wherein the concentration of the electrolyte of the sub-battery is set lower than the concentration of the electrolyte of the main battery so that the voltage of the sub-battery is lower than the voltage of the main battery. It was done.
[0013]
The invention according to claim 3 is the on-vehicle power supply device according to claim 1, wherein the second load voltage is lower than the first load voltage between the sub-battery and the load. Are connected.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing an in-vehicle power supply device according to one embodiment of the present invention. In this embodiment, the same reference numerals are given to components having the same functions as those of the conventional example shown in FIGS.
[0015]
This in-vehicle power supply device is mounted on an automobile, and its basic configuration is the same as the general known circuit described with reference to FIG. That is, a main battery 11 that supplies a normal power supply for driving the various loads 1 and the ECU 3, and a sub-battery 13 that is used as a temporary emergency backup power supply when the power supply voltage of the main battery 11 decreases, for example. And a generator (AG) 15 that converts the rotational driving power of the wheels into electric energy when the vehicle is running to provide a regenerative voltage to the main battery 11, and sets the voltages of the main battery 11 and the sub-battery 13 to a predetermined value. A DC / DC converter 17a for stabilizing to a voltage level; and a two-contact type switch 19 for switching the voltage applied to the load 1 between Vm from the main battery 11 and Vs from the sub-battery 13 side. In this configuration, the voltage Vs of the sub-battery 13 is set lower than the voltage Vm from the main battery 11.
[0016]
The main battery 11 and the sub-battery 13 are, for example, a general paste-type lead battery which is charged and discharged by a chemical reaction between an electrode plate using lead as an active material and dilute sulfuric acid as a paste-like electrolyte. Etc. are used.
[0017]
Then, the voltage Vs of the sub-battery 13 is set to be lower than the voltage Vm from the main battery 11 by making the concentration of the diluted sulfuric acid, which is the electrolytic solution of the sub-battery 13, different between the main battery 11 and the sub-battery 13. ing. Thus, for example, when the voltage of the main battery 11 is, for example, 14 volts, the voltage of the sub-battery 13 is set to a predetermined value of about 12 to 13 volts. This is set so that the sub-battery 13 does not easily supply power even when the charging capacity of the main battery 11 is reduced and the voltage is reduced. Thus, regardless of the voltage fluctuation of the main battery 11, , The charging capacity of the sub-battery 13 can be maintained as much as possible.
[0018]
FIG. 2 is a schematic diagram showing the internal configuration of a general battery. Generally, inside the battery, an anode plate 41 and a cathode plate 43 using lead as an active material are opposed to each other with a separator 45 interposed therebetween, and they are immersed in dilute sulfuric acid 47 which is a paste-like electrolyte. Have been. Note that, specifically, the anode plate 41 is made of lead peroxide, and the cathode plate 43 is made of spongy lead.
[0019]
When the load 1 is connected to this battery and discharge is performed, the lead peroxide of the anode plate 41 and the spongy lead of the cathode plate 43 respectively react with sulfuric acid in the dilute sulfuric acid 47 to be converted to lead sulfate, and Turns into water. In this case, the higher the concentration of sulfuric acid in the dilute sulfuric acid 47, the more the chemical reaction of the anode plate 41 and the cathode plate 43 is activated, so that the voltage taken out becomes higher. On the other hand, when the concentration of sulfuric acid in the diluted sulfuric acid 47 is low, the voltage taken out of the battery becomes low.
[0020]
By utilizing this fact, the concentration of the dilute sulfuric acid 47 (FIG. 2), which is the electrolytic solution in the sub-battery 13, is set lower than the concentration of dilute sulfuric acid (the electrolytic solution) in the main battery 11, so that the sub-battery Voltage Vs applied to load 1 from 13 is set lower than voltage Vm from main battery 11.
[0021]
As shown in FIG. 1, the DC / DC converter 17a includes first and second noise removal filters 21 and 23 for removing noise in the voltages of the batteries 11 and 13, and each voltage Vm of the main battery 11. And a step-down converter 25 for omitting the step-up converter 27 from the conventional example shown in FIG.
[0022]
This is because the voltage Vs of the sub-battery 13 is set lower than the voltage Vm of the main battery 11 as described above. This is because there is no need to boost the voltage to correspond to Vs.
[0023]
The function of the ECU 3 is the same as that of the conventional example described with reference to FIG.
[0024]
A power supply method of the vehicle-mounted power supply device having the above configuration will be described.
[0025]
First, the step-down converter 25 steps down the voltage Vm (for example, about 14 volts) of the main battery 11 and converts it to a predetermined voltage (for example, 12 to 13 volts).
[0026]
Next, the voltage provided from the main battery 11 via the step-down converter 25 is applied to the sub-battery 13 through the second filter 23 and is used for charging the sub-battery 13.
[0027]
Then, the ECU 3 detects the state of the voltage applied from the main battery 11 to the sub-battery 13 via the first filter 21, the step-down converter 25, and the second filter 23. That is, the voltage from the main battery 11 that has passed through the second filter 23 is compared with a predetermined reference voltage 31 by the comparing unit 33, and it is determined whether the voltage of the main battery 11 is normal. Then, in accordance with the result of the determination by the comparison unit 33, the switching control unit 35 controls the operation of the step-down conversion unit 25 on and off, thereby stabilizing the voltage from the main battery 11.
[0028]
When the charge capacity of the main battery 11 decreases and the voltage Vm decreases constantly, the switch 19 is switched to switch the power supply to the load 1 from the main battery 11 to the sub-battery 13.
[0029]
Thus, even if the voltage Vm of the main battery 11 decreases, it is possible to appropriately control the step-down converter 25 to perform appropriate power management.
[0030]
Since the voltage Vs of the sub-battery 13 is set lower than the voltage Vm of the main battery 11, the voltage that has passed from the main battery 11 through the first filter 21 and the step-down converter 25 in the DC / DC converter 17a is When the battery 13 is provided for charging, the voltage does not need to be boosted. Therefore, as compared with the conventional example shown in FIG. 5, the step-up converter 27 can be omitted in the DC / DC converter 17a, and the circuit configuration of the DC / DC converter 17a is simplified to realize an inexpensive in-vehicle power supply device. Can be.
[0031]
In the above-described embodiment, the voltage Vs of the sub-battery 13 is set lower than the voltage Vm of the main battery 11 by setting the concentration of the electrolyte in the sub-battery 13 lower than the concentration of the electrolyte in the main battery 11. However, the same effect can be obtained by providing a step-down element 51 for lowering the voltage of the sub-battery 13 at the time of output as shown in FIG. As the step-down element 51, for example, a diode, a resistor, or the like that performs a voltage drop by a forward voltage is applied.
[0032]
【The invention's effect】
According to the first aspect of the present invention, since the voltage of the sub-battery is set lower than the voltage of the main battery, the sub-battery is charged with the voltage from the main battery through the filter in the DC / DC converter and the step-down converter. It is not necessary to boost the voltage when giving it for use. Therefore, in the DC / DC converter, the boost converter conventionally used can be omitted, and the circuit configuration of the DC / DC converter can be simplified to realize an inexpensive in-vehicle power supply device.
[0033]
In this case, for example, by setting the concentration of the electrolyte of the sub-battery lower than the concentration of the electrolyte of the main battery in advance, the voltage of the sub-battery can be easily set lower than the voltage of the main battery. .
[0034]
Alternatively, the voltage of the sub-battery can be easily set lower than the voltage of the main battery by the step-down element provided between the sub-battery and the load.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an in-vehicle power supply device according to one embodiment of the present invention.
FIG. 2 is a schematic diagram showing a structure of a general battery.
FIG. 3 is a block diagram showing a vehicle-mounted power supply device according to a modification of the present invention.
FIG. 4 is a block diagram showing a general vehicle-mounted power supply device.
FIG. 5 is a block diagram showing functions of a conventional DC / DC converter and ECU.
[Explanation of symbols]
1 Load ECU3 ECU
11 Main Battery 13 Sub Battery 17a DC / DC Converters 21 and 23 Filter 25 Step-Down Converter 31 Reference Voltage 33 Comparator 35 Switching Controller 41 Anode Plate 43 Cathode Plate 47 Dilute Sulfuric Acid 51 Step-Down Elements Vm, Vs Voltage

Claims (3)

A main battery that supplies a regular power supply for driving a load;
A sub-battery used as a temporary emergency backup power supply when the power supply voltage of the main battery drops;
A DC / DC converter for stabilizing voltages of the main battery and the sub-battery to a predetermined voltage level,
Setting the voltage of the sub-battery lower than the voltage of the main battery;
An in-vehicle power supply device, wherein the DC / DC converter is a step-down converter. The in-vehicle power supply device according to claim 1, wherein
Inside each of the main battery and the sub-battery, an electrolytic solution, comprising an electrode plate made of an active material that performs charging and discharging by a chemical reaction with the electrolytic solution,
An in-vehicle power supply device, wherein the concentration of the electrolyte in the sub-battery is set lower than the concentration of the electrolyte in the main battery such that the voltage of the sub-battery is lower than the voltage of the main battery. The in-vehicle power supply device according to claim 1, wherein
A vehicle-mounted power supply device, wherein a step-down element for lowering the second load voltage to be lower than the first load voltage is connected between the sub-battery and the load.

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