JPH05244704A - Auxiliary power supply for motor vehicle - Google Patents

Abstract

PURPOSE:To make it possible to utilize non-traveling interval for charging an auxiliary battery by feeding a part of charging power main battery through a voltage converting circuit to the auxiliary battery during charging interval of the main battery. CONSTITUTION:Upon drop of terminal voltage of an auxiliary battery 2 below a rated value, a controller 5 controls a junction box 4 to connect a main battery 1 with a DC-DC down converter 3 and to set the output voltage of the main battery 1 at a level substantially equal to the level when the main battery 1 is charged through a charger BC thus starting operation for charging the auxiliary battery 2 through the main battery 1. When the terminal voltage of the auxiliary battery 2 is recovered through the charging operation to a preset level higher than a rated level, the controller 5 controls the junction box 4 to disconnect the DC-DC down converter 3 from the main battery 1 thus finishing the charging operation of the auxiliary battery 2. According to the constitution, non-traveling interval can be utilized for charging of the auxiliary battery 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary power supply device for an electric vehicle mounted on an electric vehicle or the like.

[0002]

2. Description of the Related Art In a conventional passenger car that runs on a gasoline engine, DC power is supplied to various motors and control microcomputers from a storage battery of 12 to 24 volts. Power supply to 1
It is performed from a high voltage storage battery of 00 volt to 300 volt.

In this type of electric vehicle, the existing 12volt
High voltage (eg 100 volt) whose main purpose is to supply high voltage to the motor in order to achieve consistency with the 24 volt power supply system.
In addition to the main storage battery for power supply, an auxiliary storage battery for 12 volt or 24 volt power supply is installed, and a DC-DC down converter is installed between these main storage battery and auxiliary storage battery. A configuration for charging the battery is considered.

Conventionally, the auxiliary storage battery is charged by the main storage battery, whether the main storage battery is being discharged for traveling of the vehicle,
Alternatively, it is configured to automatically start as soon as the terminal voltage of the auxiliary storage battery becomes equal to or lower than a predetermined threshold, regardless of whether the auxiliary storage battery is being charged in the garage or the like.

[0005]

In the above conventional power supply configuration, charging from the main storage battery is started as soon as the voltage value of the auxiliary storage battery reaches a predetermined threshold value regardless of the charge / discharge state of the main storage battery. Therefore, there is a case where the auxiliary storage battery is not charged even though the main storage battery is being charged in the garage or the like. In this case, there is an inconvenience that the non-traveling period reserved for charging cannot be used for charging the auxiliary storage battery. Along with this, there also arises a disadvantage that charging of the auxiliary storage battery must be started during a traveling period when it is desired to limit the discharge power from the main storage battery for traveling.

[0006]

In the auxiliary power supply device for an electric vehicle according to the present invention, a part of the charging power supplied to the main storage battery is supplied to the auxiliary storage battery via the voltage conversion circuit during the charging period of the main storage battery. Is also provided with a control means for supplying.

[0007]

According to the auxiliary power supply device of the present invention, regardless of whether the terminal voltage of the auxiliary storage battery becomes equal to or lower than a predetermined threshold value during the charging period of the main storage battery, that is, the auxiliary storage battery is forcibly passed through the voltage conversion circuit. As a result, the auxiliary storage battery is charged, and the above-mentioned conventional drawbacks are effectively solved.

In order to more reliably charge the auxiliary storage battery, the charging voltage for the auxiliary storage battery is set to a value higher than the rated value of the terminal voltage by controlling the output voltage of the voltage conversion circuit. do it. If the charging voltage during running is suppressed by lowering the supply voltage to the auxiliary storage battery near the rated value during running, the degree of consumption of the main storage battery and the degree of consumption of the auxiliary storage battery will be close to each other. , The above-mentioned forced charging becomes more reliable. Hereinafter, further details of the present invention will be described together with the following examples.

[0009]

1 is a block diagram showing the structure of an auxiliary power supply device according to an embodiment of the present invention together with related devices. This auxiliary power supply device comprises a main storage battery 1 having a high terminal voltage, an auxiliary storage battery 2 having a low terminal voltage, a DC-DC down converter 3, a junction box 4, and a controller 5.

The main storage battery 1 having a terminal voltage of about 100 volts is
While supplying power to the high voltage load LH such as an electric motor, D
Power is supplied to the auxiliary storage battery 2 having a terminal voltage of 12 volt and the low-voltage load LL connected in parallel with the auxiliary storage battery 2 via the C-DC down converter 3.

The junction box 4 is a power distribution circuit containing a relay group that is opened and closed by the controller 5, and connects / disconnects the main storage battery 1 and the high voltage load LH, and connects the main storage battery 1 and the DC-DC down converter 3. Connection / disconnection, connection / disconnection between the charger BC outside the vehicle and the main storage battery 1, or connection / disconnection between the charger BC and the DC-DC down converter 3. The controller 5 determines whether or not the electric vehicle is traveling, whether the charger BC outside the vehicle is operating, and whether or not the auxiliary storage battery 2 is used.
The operation in the main power supply system and the operation in the auxiliary power supply system are controlled by opening and closing the relays in the junction box 4 according to various situations such as whether the terminal voltage of is less than or equal to the threshold value.

While the electric vehicle is running, both the high voltage load LH and the DC-DC down converter 3 are connected to the main storage battery 1 through the junction box 4. While the electric vehicle is running, the output voltage of the DC-DC down converter 3 is the rated value (1) of the terminal voltage of the auxiliary storage battery 2 under the control of the controller 5 as illustrated in the upper part of FIG.
It is set to a value slightly higher than 2 volt). The terminal voltage of the auxiliary storage battery 2 changes according to the progress of charging time or charging voltage and charging current at the end of charging during charging, and changes (decreases) according to the progress of discharging during discharging.
To do. Therefore, when the auxiliary storage battery is used alone, the expected value of the terminal voltage averaged over the entire operation period including the charge / discharge cycle is referred to as the rated value of the terminal voltage here. Therefore, the electric power consumed by the low-voltage load LL while the vehicle is traveling is covered by the discharged electric power from the main storage battery 1 and the discharged electric power from the auxiliary storage battery 2, and the amount of electricity stored in the auxiliary storage battery 2 changes as the discharging time elapses. It gradually decreases as illustrated in the lower part of FIG.

During the charging period of the main storage battery 1, the charger BC is connected via the junction box 4 to both the main storage battery 1 and the DC-DC down converter 3. This connection control is performed by the controller 5 which detects that the charger BC is connected to the corresponding input terminal of the junction box 4.
Done by The controller 5 controls the connection by the junction box 4 and controls the DC-DC down-converter 3 so that its output voltage is lower than the rated value (12 volt) of the terminal voltage of the auxiliary storage battery 2 as illustrated in FIG. Also, set it to a value of about 14.5 volt, which is about 20% higher. As this charging progresses, the auxiliary storage battery 2
The amount of electricity stored in the battery is an appropriate value below the fully charged state, for example 80%
Rise to a degree.

The reason why the auxiliary storage battery 2 is not fully charged is that if the output voltage of the DC-DC down converter 3 is further increased for complete charging, the battery life is deteriorated. With termination of charging, the terminal voltage of the auxiliary storage battery 2 drops (recovers) to a value slightly higher than the rated value of the terminal voltage in a short time.

After this charging is completed, the DC-DC down converter 3 is disconnected from the charger BC and the main storage battery 1. When the electric vehicle is left for a long time after the end of this charging, the amount of electricity stored in the auxiliary storage battery 2 is as shown in FIG.
As shown in, it gradually decreases due to self-discharge. Normally, the main storage battery 1 is configured by connecting a storage battery of the same type as the auxiliary storage battery 2 (for example, a lead storage battery) in multiple stages in series than the auxiliary storage battery 2, so that the rate of decrease in the amount of stored electricity due to self-discharge is the same for both. It is often a degree. However, while a high voltage load mainly consisting of an electric motor is kept in a completely stopped state, a low voltage load including a micro computer for control etc. is in a partial operating state for monitoring operation. Since power is consumed accordingly, the auxiliary storage battery 2 tends to have a larger rate of reduction in the amount of stored electricity than the main storage battery 1.

When the terminal voltage of the auxiliary storage battery 2 drops to a threshold value which is set to a predetermined value lower than the rated value, the controller 5 which detects this decreases the main storage battery 1 to a DC voltage by controlling the junction box 4. The operation is started by connecting to the DC down converter 3, and the output voltage thereof is about the same as 1 during charging from the charger BC.
The value is set to about 4.5 volt, and the main storage battery 1 starts charging the auxiliary storage battery 2. When the terminal voltage of the auxiliary storage battery 2 recovers to a predetermined value set higher than the rated value as the charging progresses, the controller 5 that detects this
Controls the junction box 4 to disconnect the DC-DC down converter 3 from the main storage battery 1 to terminate the charging of the auxiliary storage battery 2.

FIG. 3 is a circuit diagram showing an example of the simplest configuration of the DC-DC down converter 3 of FIG. This DC-DC down converter 2 turns on / off a DC voltage of about 100 volt supplied from the junction box 4 of FIG. 4 to the input terminals (I ₁ , I ₂ ) on the primary side by a switching transistor (Q) to generate an alternating current. Output to the secondary side through the transformer T, rectified by the rectifier (REC), smoothed by the smoothing circuit (S), and then connected to the auxiliary storage battery 2 and the low voltage load (O) It is configured to output to.

Control circuit (CONT) composed of IC
Is a differential amplifier (AMP) for generating an error signal between the output voltage appearing at the output terminal (O) and the reference voltage supplied to the input terminal (I ₃ ) from the controller 5 of FIG. An oscillator circuit (OSC) for generating a sawtooth wave and a comparator (COM) for slicing the sawtooth wave with the error voltage to output a pulse train whose duty ratio changes according to the magnitude of the error voltage. ing. The pulse train output from the control circuit (CONT) is supplied to the base terminal of the switching transistor Q via the transformer t, and the output voltage of the DC-DC down converter is controlled by its conduction time ratio. The power circuit R
The EG supplies operating power to the control circuit, and starts supplying power to the control circuit at the same time when a DC voltage appears at the input terminal I ₁ . The thyristor Th is for limiting the inrush current on the primary side together with the resistor connected in parallel.

In the above, the configuration in which the auxiliary storage battery 2 and the low-voltage load are constantly supplied with power from the main storage battery 1 via the DC-DC down converter 3 while the vehicle is traveling has been illustrated. However, while the vehicle is running, the operation of the DC-DC down converter 3 is stopped to supply power to a low voltage load only by the discharge power of the auxiliary storage battery 2, and the terminal voltage of the auxiliary storage battery 2 reaches a predetermined threshold value. When the voltage decreases, the operation of the DC-DC down converter 3 may be started to supply power to a low-voltage load and charge the auxiliary storage battery 2.

[0018]

As described in detail above, the auxiliary power supply device of the present invention is forced, regardless of whether the terminal voltage of the auxiliary storage battery is below a predetermined threshold value during the charging period of the main storage battery, that is, it is forced. Since the auxiliary storage battery is electrically charged through the voltage conversion circuit, there is an advantage that the non-traveling period that is intentionally reserved for charging the main storage battery can be used for charging the auxiliary storage battery.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an auxiliary power supply device for an electric vehicle according to an embodiment of the present invention together with related devices.

2 is a conceptual diagram exemplifying how the output voltage (upper stage) of the DC-DC down converter 3 and the amount of electricity stored in the auxiliary storage battery 2 with time (lower stage) in FIG. 1 are illustrated.

FIG. 3 is a circuit diagram showing an example of the simplest configuration of the DC-DC down converter 3 of FIG.

[Explanation of symbols]

 1 Main storage battery 2 Auxiliary storage battery 3 DC-DC down converter (voltage conversion circuit) 4 Junction box 5 Controller

Claims (5)

[Claims] 1. A main storage battery, an auxiliary storage battery having a terminal voltage lower than a terminal voltage of the main storage battery, a terminal voltage of the main storage battery converted into a low voltage, and the auxiliary storage battery and a low voltage connected in parallel therewith. In the auxiliary power supply device for an electric vehicle, which is provided with a voltage conversion circuit for supplying to the load, a part of the charging power supplied to the main storage battery during the charging period of the main storage battery is supplemented via the voltage conversion circuit. An auxiliary power supply device for an electric vehicle, comprising a control means for supplying also to a storage battery. 2. The control means according to claim 1, wherein the control means sets the output voltage of the voltage conversion circuit to a value higher than a rated value of the terminal voltage of the auxiliary storage battery during the charging period of the main storage battery. An auxiliary power supply device for an electric vehicle, comprising a control means for supplying the battery. 3. The control means according to claim 1, wherein the output voltage of the voltage conversion circuit is set to a first value higher than a rated value of the terminal voltage of the auxiliary storage battery during the charging period of the main storage battery. Is supplied to the auxiliary storage battery, and the output voltage of the voltage conversion circuit is set to a second value lower than the first value and higher than the rated value during the actual traveling period of the vehicle. An auxiliary power supply device for an electric vehicle, comprising: 4. The control means sets the output voltage of the voltage conversion circuit to a first value higher than the rated value of the terminal voltage of the auxiliary storage battery during the charging period of the main storage battery. The auxiliary storage battery is supplied, and the output voltage of the voltage conversion circuit is detected by detecting that the terminal voltage of the auxiliary storage battery has become equal to or lower than a predetermined threshold value lower than the rated value while the vehicle is not in use. First
An auxiliary power supply device for an electric vehicle, comprising means for setting to the value of and supplying to the auxiliary storage battery. 5. The control means according to claim 1, wherein the output voltage of the voltage conversion circuit is set to a first value higher than a rated value of the terminal voltage of the auxiliary storage battery during the charging period of the main storage battery. The auxiliary storage battery is supplied to the auxiliary storage battery, and the terminal voltage of the auxiliary storage battery is detected to be equal to or lower than a predetermined threshold value lower than the rated value during the period of use of the vehicle to detect the output voltage of the voltage conversion circuit as the first voltage. An auxiliary power supply device for an electric vehicle, comprising means for setting a second value lower than the value of 1 and higher than the threshold value to supply the auxiliary storage battery.