JP4053447B2 - Vehicle power supply circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply circuit for supplying electric power from a battery to an in-vehicle electric load such as an electric steering device or an electric brake device in a vehicle such as an automobile.
[0002]
[Prior art]
In recent years, the digitization of vehicles such as automobiles has been remarkable, and a wide variety of electric devices have been installed in vehicles. Here, when a device such as an electric steering device or an electric brake device is mounted, a reliable operation of the device is required in order to ensure safety. For this purpose, even if an in-vehicle battery or the battery is connected to the device. There is an urgent need to develop a system that can maintain power supply to the equipment even if a failure occurs in the power supply system.
[0003]
Conventionally, as such a system, a backup battery (auxiliary power supply) is installed separately from the main battery, and power supply from the backup battery is maintained when a failure occurs in the power supply system on the main battery side. ing.
[0004]
For example, in Patent Document 1 below, switching means for switching a power feeding path between a main battery (main power source) and a backup battery (auxiliary power source) and specific electrical components is interposed, and during normal operation, from the main battery to the electrical components. In addition to supplying power to the backup battery and charging power to the backup battery, the power supply path is switched so that power is supplied from the backup battery to the electrical component when the power supply system of the main battery fails. Is disclosed.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-46928
[Problems to be solved by the invention]
In the circuit shown in Patent Document 1, in addition to both batteries, a switching means for switching a power feeding path and its control means must be mounted, and the entire circuit becomes complicated and the switching means itself fails. There is a risk that proper power supply will not be possible.
[0007]
As a means for avoiding such inconvenience, it is conceivable to connect the main battery and the backup battery in parallel as they are (not via the switching means) to a common electrical component (on-vehicle electric load). However, in this case, since both batteries have almost the same potential, power is supplied not only from the main battery but also from the backup battery even during normal times, and there is a risk that sufficient capacity of the backup battery cannot be secured in an emergency. There is.
[0008]
FIG. 2 (a) shows an example of the relationship between the supply voltage to the in-vehicle electric load by each battery and the remaining capacity when the main battery and the backup battery are connected to the common in-vehicle electric load. The voltage is substantially equal to the terminal voltage of each battery except for a slight voltage drop due to wire resistance or the like. In the example in the figure, the main battery is a normal liquid type (open type), and the backup battery is a seal type (sealed type) often used as a backup power source, and fully charged (when the remaining capacity is 100%) Supply voltage (≈ terminal voltage) is higher for the backup battery (dotted line in the figure) than the main battery (solid line in the figure), and the drop in supply voltage due to the decrease in remaining capacity is also backup battery than the main battery Has higher characteristics.
[0009]
In this example, when the use is started from a state in which both the batteries are fully charged, the backup battery has a higher supply voltage than the main battery at the beginning, and thus the backup battery is discharged first. The batteries are discharged in parallel from the time when the supply voltage of the backup battery drops to the supply voltage V1 of the fully charged main battery. Specifically, both batteries are almost evenly consumed so that the supply voltages of both batteries maintain a balanced state. For example, when the terminal voltage of both batteries drops to V2, the remaining capacity of the main battery is C2, the backup battery The remaining capacity is C2 '.
[0010]
In other words, in this example, the backup battery is consumed almost at the same level as the main battery even during normal times, and when the main battery or its power supply system fails (for example, when the power supply line is disconnected or short-circuited) Even if power is supplied from the beginning, there may be a situation where the remaining capacity is not sufficiently secured. In particular, when the potentials of both batteries are in phase equilibrium as shown in the figure, charging / discharging between the batteries is frequently performed, which may lead to an undesirably shortened battery life.
[0011]
In view of such circumstances, an object of the present invention is to prevent discharge of a backup battery and secure its remaining capacity in a power supply circuit of a vehicle with a simple configuration that does not require battery switching means.
[0012]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, the present invention provides a plurality of in-vehicle electric loads, a main battery having a main battery terminal that is branched and connected to each of the in-vehicle electric loads, and a branch connection to the in-vehicle electric loads. A vehicle power supply circuit comprising a backup battery terminal and a backup battery connected in parallel to the main battery with respect to each of the in-vehicle electric loads, the battery terminal of the backup battery and the in-vehicle electric load interposed, the backup battery voltage dropping diode to be larger than the voltage drop from the battery terminal until the voltage drop up to the vehicle electrical loads from the battery terminals of the main battery to the vehicle electrical loads between the And the main battery terminal and each vehicle-mounted electric negative And a backflow prevention diode interposed between the backup battery terminal and each on-vehicle electric load, and each backflow prevention diode is connected from the main battery terminal to each on-vehicle electric load. The voltage drop diode is provided at a position closer to the in-vehicle electric load than the branch point and a position closer to the in-vehicle electric load than a branch point from the backup battery terminal to each of the in-vehicle electric loads. It is provided only at a position closer to the backup battery terminal than a branch point from the battery terminal to each of the on-vehicle electric loads .
[0013]
According to this circuit, even if the terminal voltage of the backup battery is high, the voltage actually supplied from the backup battery to the in-vehicle electric load by the voltage drop diode interposed between the battery terminal and the in-vehicle electric load is Therefore, the power supply by the main battery can be preceded by the power supply by the backup battery.
[0014]
For example, even if the terminal voltage at the time of full charge of the backup battery is higher than the terminal voltage at the time of full charge of the main battery, the voltage drop diode is connected to the terminal voltage at the time of full charge of the backup battery and the main voltage. By causing a voltage drop larger than the difference from the terminal voltage when the battery is fully charged, the power supply voltage of the backup battery to the in-vehicle electric load can be lowered to the power supply voltage of the main battery at the start of use. As a result, power feeding by the main battery can be preceded.
[0015]
When using the voltage resistance element normal to the circuit elements for the descent, while the degree of fluctuation in the voltage drop due to the current change is large, because of the use of diode to the circuit elements, due to the current change The degree of fluctuation of the voltage drop is small, and the reliability of the circuit can be further increased.
[0016]
Moreover, the attempt to backflow prevention circuit, between the vehicle-mounted electric load and the main Battery pin, and, between the vehicle-mounted electric load and the backup battery over pin, each diode for preventing reverse current Although means to be interposed is valid, further said backup during battery pin and said vehicle-mounted electric load only, by disposing a separate voltage dropping diode to this the reverse current blocking diode in series are so enabled by the voltage drop is greater than said voltage drop from the main battery over pin up to the vehicle electrical loads consumption of the backup battery between the backup battery over pin and the vehicle electrical loads Can be suppressed.
[0017]
Furthermore, in the present invention, in the circuit the main battery and the backup battery are respectively branched and connected to a plurality of vehicle-mounted electrical loads, while from the backup battery over pin and the terminal of the branch point to each vehicle-mounted electric load Only, that is, the voltage drop diode is provided only at a position closer to the backup battery terminal than the branch point, so that the voltage drop diode can be shared for each in-vehicle electric load, and the circuit configuration is further improved. It can be simplified.
[0018]
In particular, the backup battery is housed in a common housing together with its peripheral devices to form a backup module, and an output terminal is provided on the housing of the backup module. with the configuration in which the terminals of the terminal and the backup battery are connected through the voltage dropping diodes, in addition to facilitating its handling by the inclusion of the voltage drop diode in the backup module, By simply connecting each on-vehicle electric load and the output terminal, the voltage drop diode can be interposed between each on-vehicle electric load and the backup battery.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to FIG.
[0020]
In FIG. 1, the positive terminal of the main battery 10 has the first joint box 12 as a branch point. (1) The second joint box 14, (2) Alternator 24, (3) Ignition switch 25, and (4) It is branched and connected to a backup module 30 (details will be described later) including the backup battery 20. When the alternator 24 is operated, the electric power generated by the alternator 24 is connected to the electric brake device 16 and the electric steering device 22 via the joint boxes 12 and 14, and surplus electric power is supplied to the main battery 10 and the backup. The battery 20 is charged.
[0021]
The backup module 30 includes peripheral devices such as the charging control circuit 36 in addition to the backup battery 20, and is stored in a common housing 31. The housing 31 has an external connection terminal connected to the ignition switch 25. An ignition terminal 31I to be connected, a power supply terminal 31B to be connected to the first joint box 12, an output terminal 31O to be connected to the third joint box 18, an earth terminal 31G to be connected to body ground, and the like are provided. .
[0022]
In the backup module 30, the negative terminal of the backup battery 20 is connected to the ground terminal 31G, while the positive terminal is branched and connected to the output terminal 31O and the output part of the charge control circuit 36. An input portion of the control circuit 36 is connected to the power supply terminal 31B.
[0023]
The backup battery 20 is charged from the alternator 24 and the main battery 10 through the first joint box 12 and the charge control circuit 36, and the backup terminal 20 is connected to the output terminal 31O and the branch point. Electric power can be supplied to each electric brake device 16 and electric steering device 22 through the three joint box 18.
[0024]
In this circuit, each electric brake device 16 includes a backflow prevention diode 17 that is individually interposed between an electric load portion (actually driven portion) and the second joint box 14 and the third joint box 16. Is provided. Similarly, the electric steering device 22 is also provided with backflow prevention diodes 23 individually interposed between the electric load portion and the second joint box 14 and the third joint box 16.
[0025]
Further, as a feature of this circuit, a voltage drop diode 38 different from the backflow prevention diodes 17 and 23 is interposed between the positive terminal of the backup battery 20 and the output terminal 31O in the backup module 30. . That is, the voltage drop diode 38 is provided in series with the backflow prevention diodes 17 and 23 only between the backup battery 20 and the electric load portions of the electric brake devices 16 and the electric steering device 22. Therefore, the voltage drop from the positive terminal to the electric load portion of each electric brake device 16 or electric steering device 22 is reduced from the positive terminal of the main battery 10 to the electric load of each electric brake device 16 or electric steering device 22. It is larger than the voltage drop to the part.
[0026]
The voltage drop diode 38 may be any diode that generates a stable voltage drop by its forward bias, and is generally a pn junction diode.
[0027]
Next, the operation of this circuit will be described.
[0028]
In the circuit shown in FIG. 1, when the alternator 24 is activated, the electric power generated by the alternator 24 passes through the first joint box 12 and the second joint box 14 to each electric brake device 16, electric steering device 22, and the like. While the electric component is supplied, surplus power is charged in the main battery 10 and the backup battery 20.
[0029]
On the other hand, when the alternator 24 is stopped, power is supplied from the main battery 10 to each electric brake device 16, the electric steering device 22, and other electric components. Since the positive terminal of the backup battery 20 is also connected to the device 22, there is a possibility that power is supplied from the backup battery 20 to the electric brake device 16 and the electric steering device 22.
[0030]
However, in this circuit, a voltage drop diode 38 different from the backflow prevention diodes 17 and 23 is interposed between the positive terminal of the backup battery 20 and the electric brake device 16 and the electric steering device 22. When the main battery 10 and the power supply system of the battery are normal, the consumption of the backup battery 20 is effectively suppressed.
[0031]
For example, assuming that the relationship between the remaining capacity of both the batteries 10 and 20 and the terminal voltage is equivalent to that shown in FIG. 2A, if the voltage drop diode 38 does not exist, the remaining capacity-supply The voltage characteristics are as shown in FIG. Therefore, in this case, as described above, the backup battery 20 is consumed prior to the main battery 10, and a sufficient remaining capacity of the backup battery 20 is ensured when the main battery 10 or its power supply system fails. There is a risk that this will not happen.
[0032]
On the other hand, if the voltage drop from the backup battery 20 to each electric load portion increases by 0.6 V due to the voltage drop diode 38, the remaining capacity of the batteries 10 and 20 (the actual electric load portion) The relationship with the supply voltage is as shown in FIG. In other words, even if the terminal voltage of the backup battery 20 is high, the voltage actually supplied from the battery 20 to each electric load unit drops by 0.6 V, which is larger than the terminal voltage difference between the two batteries at the time of full charge. Initially, power feeding by the main battery 10 precedes, and power feeding by the backup battery 20 starts only when the supply voltage drops to V3 (point B in the figure).
[0033]
Accordingly, it is possible to effectively save the remaining capacity of the backup battery 20 with a simple configuration in which only the voltage drop diode 38 is disposed, and to have a surplus capacity in the event of an emergency in which the main battery 10 or its power supply system fails. Emergency power can be supplied from the backup battery 20.
[0034]
In particular, in the illustrated circuit, the backup battery 20 is stored in a common housing 31 together with its peripheral devices to form a backup module 30, and the output terminal 31O provided in the backup module housing 31 and the backup battery 20 are provided. Since the voltage drop diode 38 is interposed between the output terminal 31O and the positive terminal of the output terminal 31O, in addition to facilitating handling by including the diode 38 in the backup module 30, the output terminal 31O is connected to the third joint. By simply connecting to the box 18, a common voltage drop diode 38 can be interposed between each on-vehicle electric load and the backup battery 20.
[0035]
In addition, the present invention can take the following embodiments, for example.
[0038]
The arrangement position of the voltage drop circuit elements including the diode 38 can also be set as appropriate, for example, incorporated in each electrical component having an electric load (in the illustrated example, the electric brake device 16 and the electric steering device 22). Alternatively, it may be incorporated in the second joint box 14 or the third joint box 18. However, by providing a voltage drop circuit element between the backup battery 20 and the third joint box 18 that is a branch point to a plurality of electric loads (in the backup module 30 in the illustrated example), the voltage drop circuit element is provided. Can be shared for each in-vehicle electric load, and the circuit configuration can be further simplified.
[0039]
【The invention's effect】
As described above, according to the present invention, it is possible to perform emergency power feeding when a main battery or the like fails with a simple configuration in which a main battery and a backup battery are connected in parallel to a common in-vehicle electric load, and the backup battery The voltage drop from the battery terminal of the backup battery to the vehicle electric load is less than the voltage drop from the battery terminal of the main battery to the vehicle electric load between the battery terminal of the battery and the vehicle electric load. By interposing the voltage drop circuit element to be increased, there is an effect that the backup battery can be prevented from being discharged in a normal state and the remaining capacity can be secured.
[Brief description of the drawings]
FIG. 1 is a power supply circuit diagram of a vehicle according to an embodiment of the present invention.
FIG. 2A is a graph showing an example of the relationship between the remaining capacity of each battery and the supply voltage to each electric load when no voltage drop circuit element is interposed between the backup battery and the electric load; b) is a graph showing an example of the relationship between the remaining capacity of each battery and the supply voltage to each electric load when a voltage drop circuit element is interposed between the backup battery and the electric load.
[Explanation of symbols]
10 Main battery 16 Electric brake device (including in-vehicle electric load)
17, 23 Backflow prevention diode 20 Backup battery 22 Electric steering device (including in-vehicle electric load)
30 Backup module 38 Voltage drop diode

Claims (3)

Multiple in-vehicle electrical loads;
A main battery having a main battery terminal branchedly connected to each of the on-vehicle electric loads;
In a power feeding circuit for a vehicle, including a backup battery terminal branchedly connected to each on-vehicle electric load, and a backup battery connected in parallel to the main battery for each on-vehicle electric load ,
Interposed between the vehicle-mounted electric load and battery terminals of the backup battery, the voltage drop from the battery terminal of the backup battery up to the vehicle electrical loads from the battery terminals of the main battery up to the vehicle electrical loads A voltage drop diode that causes the voltage drop to be greater than
A backflow prevention diode interposed between the main battery terminal and each on-vehicle electric load, and between the backup battery terminal and each on-vehicle electric load,
Each of the backflow prevention diodes is closer to the in-vehicle electric load than a branch point from the main battery terminal to each in-vehicle electric load, and more in-vehicle than a branch point from the backup battery terminal to each in-vehicle electric load. Provided at a position close to the electrical load,
The power supply circuit for a vehicle, wherein the voltage drop diode is provided only at a position closer to the backup battery terminal than a branch point from the backup battery terminal to each on-vehicle electric load . The vehicle power supply circuit according to claim 1,
The backup battery is a battery whose terminal voltage at the time of full charge is higher than that of the main battery, and the diode for voltage drop is the terminal voltage at the time of full charge of the backup battery and the terminal voltage at the time of full charge of the main battery. A power supply circuit for a vehicle, which causes a voltage drop larger than a difference from a terminal voltage. In the vehicle power supply circuit according to claim 1 or 2,
The backup battery is housed in a common housing together with its peripheral devices to form a backup module, and the backup module housing is provided with an output terminal that is branchedly connected to each of the in-vehicle electric loads. A power supply circuit for a vehicle, wherein the backup battery terminal is connected to the voltage drop diode via the voltage drop diode .

Images