JP2001123923A - Current supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain a voltage drop of an on-vehicle battery at the time of starting of a starter motor with a simple structure. SOLUTION: One of contacts of a contact part 61 in a relay 6 is connected to a cathode of a diode 4 and one of electrodes of a capacitor 3, and the other contact of the contact part 61 is grounded via a starter motor 5. The other electrode of the capacitor 3 is grounded and the capacitor 3 is connected to a starting motor circuit part 2 in parallel. When the relay 6 is turned ON, starter current starts flowing in the starter motor 5. At first, the starter current is supplied mainly from the capacitor 3 whose internal resistance is low. Accordingly, reduction of a battery voltage is relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current supply circuit for supplying a current from a vehicle-mounted battery to a starter motor of a starting motor circuit section via a power supply line when starting an engine of an automobile. The present invention relates to a current supply circuit that suppresses a voltage drop of a vehicle-mounted battery.

[0002]

2. Description of the Related Art Conventionally, an automobile engine is started by rotating a crankshaft by a starter motor. When the starter motor starts rotating at the start of this engine,
A large current of 200 A is flowing from the vehicle battery to the starter motor.

[0003]

As the on-vehicle battery, a lead-acid battery having excellent charge / discharge characteristics is most often used. However, since the lead-acid battery has a large internal resistance, the voltage drop is large at the time of starting the engine in which a large current flows as described above. For example,
Conventionally, when the battery voltage of the vehicle-mounted battery is 13 V, when a current of 200 A flows at the time of engine start, the battery voltage becomes 6 V.
It drops to ~ 7V. Therefore, in a conventional car,
At the time of starting the engine, it is necessary to take measures such as forcibly turning off switches of electric components such as an air conditioner that require power consumption of a predetermined level or more, thereby reducing the operability of the on-vehicle electric components. Users are inconvenienced.

An object of the present invention is to solve the above-mentioned problem and to provide a current supply circuit having a simple configuration and capable of suppressing a voltage drop of a vehicle-mounted battery when starting a starter motor.

[0005]

According to the present invention, there is provided a current supply circuit for supplying a current from a vehicle-mounted battery to a starter motor of a start motor circuit section via a power supply line at the time of engine start, and connected in parallel to the start motor circuit section. Between the connection point of the starting motor circuit unit and the capacitor and the power supply line, and does not impede the inflow of current from the power supply line to the connection point. Backflow preventing means for preventing current from flowing out to the power supply line.

According to this configuration, a current is supplied to the capacitor connected in parallel with the starting motor circuit from the vehicle-mounted battery via the power supply line and the backflow prevention means.
Power is being stored. Then, when the current is supplied to the starter motor of the starting motor circuit unit, the current is initially supplied to the starter motor mainly from a capacitor having an internal resistance lower than that of the vehicle-mounted battery. Thereafter, when the storage amount of the capacitor having a smaller storage amount than that of the vehicle-mounted battery decreases, current is mainly supplied from the vehicle-mounted battery to the starter motor.

[0007] Thus, the voltage drop of the vehicle-mounted battery at the time of starting the current supply to the starter motor is suppressed,
Even when the engine is started, the current supply from the vehicle-mounted battery to other vehicle-mounted loads becomes possible, and the operability of other vehicle-mounted loads is improved. In addition, the backflow prevention means does not cause a situation in which the current flows out of the capacitor to the power supply line, thereby reducing the amount of charge stored in the capacitor and hindering the current supply to the starter motor.

Further, the backflow prevention means uses a special switch means or control means by using a diode having an anode connected to the power supply line and a cathode connected to the starting motor circuit section. Therefore, the flow of current from the connection portion to the power supply line is prevented with a simple configuration.

If the capacitor is an electric double layer capacitor, a relatively small member can supply a large current to the starter motor.

[0010]

FIG. 1 is a circuit diagram showing an embodiment of a current supply circuit according to the present invention. This current supply circuit supplies a current from the vehicle-mounted battery 1 to the starting motor circuit unit 2 via the power supply line 10, and includes a capacitor 3 connected in parallel to the starting motor circuit unit 2, Connection point A of capacitor 3 and power line 10
And a diode 4 interposed therebetween.

The starting motor circuit section 2 includes a starter motor 5, a relay 6, an NPN transistor 7, and resistors 8,9.
It has. One contact of the contact portion 61 of the relay 6
The connection point A is connected to one electrode of the capacitor 3.
Is further connected to the cathode of the diode 4.
The other contact of the contact portion 61 of the relay 6 is grounded via the starter motor 5. The other electrode of the capacitor 3 is grounded, and the capacitor 3 is connected to the starting motor circuit unit 2 in parallel.

One end of the exciting coil 62 of the relay 6 is connected to the cathode of the diode 4, and the other end is connected to the collector of the transistor 7. The emitter of the transistor 7 is grounded, and the base is grounded via the resistor 8. A starter (ST) signal is input to the base of the transistor 7 via the resistor 9.

The anode of the diode 4 is connected to a power supply line 10 connected to the vehicle-mounted battery 1, and the power supply line 10 is configured to be connected to a vehicle-mounted load such as a lamp (not shown).

As described above, the capacitor 3 is connected to the power supply line 10 via the diode 4 and is charged from the vehicle-mounted battery 1 via the diode 4. As the capacitor 3, for example, an electric double layer capacitor or the like can be employed. In addition, the diode 4 has a function as a backflow prevention unit that prevents a current due to the charge stored in the capacitor 3 from flowing out to the power supply line 10.

In such a current supply circuit, when an ignition switch (not shown) is turned on and a starter signal is output, the transistor 7 is turned on and the relay 6 is turned on.
The excitation current is supplied to the starter motor 5 and the starter motor 5 is turned on.
, A starter current is supplied from the vehicle-mounted battery 1 and the capacitor 3.

Next, the supply of the starter current will be described with reference to FIG. FIG. 2 is a diagram showing changes in the battery voltage V1 of the vehicle-mounted battery 1, the storage voltage V3 of the capacitor 3, and the starter current I5 supplied to the starter motor 5.

In the initial state, the storage voltage V of the capacitor 3
3 is lower than the battery voltage V1 of the vehicle-mounted battery 1 by the forward bias Vf of the diode 4 (for example, Vf = 0.7 V). Then, when the relay 6 is turned on,
As shown in FIG. 2, the starter current I
5 begins to flow. In this state, the following equation (1) holds.

V1−I5 (bat) · R1−Vf = V3−I5 (capa) · R3 (1) where I5 (bat) is a current supplied from the vehicle-mounted battery 1 to the starter motor 5, and R1 is a vehicle-mounted battery. I5 (capa) is a current supplied from the capacitor 3 to the starter motor 5, R3 is an internal resistance of the capacitor 3, and I5 = I5 (bat) + I5 (capa) (2) R1> R3 ( 3).

Here, initially, since V1−Vf = V3, from the above equation (3), I5 (bat) <I5 (capa) (4) holds. That is, the starter current I5 mainly starts to be supplied from the capacitor 3 having a low internal resistance. Therefore,
As shown in FIG. 2, the battery voltage V1 decreases gradually.

However, the amount of charge stored in the capacitor 3 is sufficiently smaller than the amount of charge stored in the on-vehicle battery 1, and as shown in FIG. 2, the storage voltage V3 rapidly decreases with time, and V3 、 V1- Vf (5)

Therefore, in the above equation (1), the above equation
(3), that is, I5 (bat)> I5 (capa) (6) despite the fact that R1> R3.

Thereafter, when the starter current I5 decreases further after a lapse of time, the current from the vehicle-mounted battery 1 is also supplied to the capacitor 3, and as shown in FIG. 2, V3 ≒ V1-Vf (7) ).

As described above, according to the present embodiment, since the capacitor 3 is connected in parallel to the starting motor circuit section 2 and the capacitor 3 is stored in the vehicle-mounted battery 1, the start of the starter motor 5 is started. At this time, the starter current I5 is mainly supplied from the capacitor 3 whose internal resistance is lower than that of the vehicle-mounted battery 1. Therefore, the burden on the vehicle-mounted battery 1 at the start of the start of the starter motor 5 is reduced, and the voltage drop of the vehicle-mounted battery 1 can be reduced.

A diode 4 is interposed between the capacitor 3 and the power supply line 10. A cathode of the diode 4 is connected to a connection point A between the starting motor circuit section 2 (relay 6) and the capacitor 3. Is connected to the anode, it is possible to prevent a current from flowing from the capacitor 3 to the power supply line 10, thereby reducing the amount of charge stored in the capacitor 3 except when the starter motor 5 is started. Can be prevented.

Also, by employing an electric double layer capacitor as the capacitor 3, a large current can be supplied to the starter motor 5 while using a relatively small capacitor.

Note that, instead of the diode 4, switch means such as a relay may be provided. In this case, the relay may be turned on only when the potential of the power supply line 10 is higher than the potential of the capacitor 3. For example, when the potential of the power supply line 10 becomes lower than the potential of the capacitor 3 due to the influence of the vehicle-mounted load, the relay may be turned off. Thus, similarly to the above embodiment, it is possible to prevent the current from flowing from the capacitor 3 to the power supply line 10.

Although one capacitor 3 is shown in FIG. 1, the present invention is not limited to this, and a capacitor in which a plurality of capacitors are connected in parallel may be used.

[0028]

As described above, according to the present invention,
Since a capacitor is connected in parallel to the starting motor circuit, the current is initially supplied to the starter motor from the capacitor whose internal resistance is lower than that of the on-board battery at the beginning of the current supply to the starter motor. In addition, it is possible to suppress the voltage drop of the vehicle-mounted battery at the time of starting the current supply to the starter motor, and as a result, it is possible to supply the current from the vehicle-mounted battery to another vehicle-mounted load even at the time of starting the engine. In addition, between the power supply line and the connection point between the starting motor circuit portion and the capacitor, it is possible to prevent the current from flowing out from the connection point to the power supply line without preventing the current from flowing from the power supply line to the connection point. Since a backflow prevention means is provided to prevent the current from flowing out from the capacitor to the power supply line, the amount of charge stored in the capacitor is reduced and the current supply to the starter motor is hindered. Can be prevented.

Further, the backflow prevention means may comprise a diode having an anode connected to the power supply line and a cathode connected to the starting motor circuit section, and a simple configuration for connecting the connection section to the power supply line. Can be prevented from flowing.

If the capacitor is an electric double layer capacitor, a relatively small member can supply a large current to the starter motor.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a current supply circuit according to the present invention.

FIG. 2 is a diagram showing changes in a battery voltage of a vehicle-mounted battery, a stored voltage of a capacitor, and a starter current supplied to a starter motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 On-board battery 2 Starting motor circuit part 3 Capacitor 4 Diode 5 Starter motor

Claims (3)

[Claims] 1. A current supply circuit for supplying a current from a vehicle-mounted battery to a starter motor of a starting motor circuit section via a power supply line when starting an engine, comprising: a capacitor connected in parallel to the starting motor circuit section; A current is flown from the connection point to the power supply line without interfering with the flow of current from the power supply line to the connection point. A current supply circuit comprising: a backflow prevention unit for preventing a current from flowing. 2. The current supply circuit according to claim 1, wherein
The current supply circuit, wherein the backflow prevention means comprises a diode having an anode connected to the power supply line and a cathode connected to the starting motor circuit section. 3. The current supply circuit according to claim 1, wherein said capacitor comprises an electric double layer capacitor.