JP2003237501A - Power supply device for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device for automobile capable of constructing light and small structure and establishing an enhanced efficiency while the impression of the supply voltage to the prescribed load is secured stably. <P>SOLUTION: The power supply device for automobile includes a DC-DC converter 7, which is driven for boosting the voltage in the case the battery voltage is considered as dropped so that a current feed is made from a battery 1 to a second load 3, and the current feed is made in such a way as skipping the DC-DC converter 7 using a switch means 8 in the case the battery voltage can impress a sufficiently large supply voltage on a second load 3. Thereby a comparatively light and small DC-DC converter 7 can be used, and the loss in power transmission can be reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an automobile, and preferably to a power supply device for an idle stop automobile.

[0002]

2. Description of the Related Art In an idle-stop type vehicle in which the engine is stopped when stopped at an intersection or the like, the engine is frequently started in city driving. In this case, there is a possibility that the battery voltage may be lowered and the electronic device or the headlamp may be disturbed, especially at low temperatures or when the battery is deteriorated.

In order to solve this problem, DC is transferred from a battery (also called a starting battery) that is charged by a generated current to start the engine, to a battery (also called a stabilizing battery) that supplies a load that requires voltage stabilization. -DC
A method of constantly supplying power through a converter has been proposed. However, this system (DC-DC converter system) requires a large DC-DC converter in order to constantly supply power from the starting battery side to the stabilizing battery side. There is also a problem that the fuel efficiency is lowered because the power transmission efficiency of the DC-DC converter is usually less than 85%.

Further, since the voltage of the starting battery drops during and immediately after the engine is started, the charging of the stabilizing battery by the DC-DC converter becomes unsatisfactory, so that the voltage of the stabilizing battery is prevented from dropping during this period. In addition, it is necessary to secure a considerable capacity as a stabilizing battery, which causes a problem that the entire device becomes large.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a power supply device for an automobile, which is small in size and light in weight and improved in efficiency while ensuring stable application of a power supply voltage to a predetermined load. Has an aim.

[0006]

SUMMARY OF THE INVENTION An automobile power supply device of the present invention includes a battery that includes an engine starter and supplies power to a first load having a large voltage drop allowance ratio, and a voltage drop allowance ratio that is supplied from the battery side. DC-DC converter for transmitting power to a second load, a switch means for transmitting power from the battery to the second load without passing through the DC-DC converter, and a voltage drop detection for detecting information on the voltage drop of the battery Means for permitting the power transmission through the switch means when the voltage drop of the battery is not detected, and stopping the power transmission through the switch means when the voltage drop of the battery is detected, and the DC-D
And a power transmission control unit that permits the power transmission through the C converter.

That is, in the present invention, the DC-DC converter supplies power from the battery to the second load by step-up driving the DC-DC converter when it is assumed that the battery voltage is lowered, and When a sufficient power supply voltage can be applied to the second load, power is supplied through the switch means without passing through the DC-DC converter.

As a result, the DC-DC converter need only be supplied with power for a short time, and a relatively small and lightweight one can be used. In particular, since the DC-DC converter is used only for a short time as a total, a simple circuit form can be adopted even if the efficiency is low.

Further, since power transmission loss can be reduced when power is supplied to the second load through the overwhelmingly long switch means, the fuel consumption as a whole can be improved. Further, compared to the above-mentioned two-battery system, a battery is not always required on the second load side, or a small-capacity power storage means is sufficient, so that the power supply device as a whole can be reduced in size and weight. After all, according to the present invention,
It is possible to realize a power supply device for an automobile that is small and lightweight and has improved efficiency while ensuring stable application of a power supply voltage to a predetermined load.

[0010] In a preferred mode, a storage unit having a smaller capacity than the battery is provided in parallel with the second load. With this configuration, it is possible to reduce the fluctuation of the power supply voltage due to the drive control of the switch means and the DC-DC converter.

[0011] In a preferred mode, the power transmission control means is the DC-DC when the voltage drop of the battery is not detected.
Stop converter operation. By doing this, DC
-Wasteful power consumption of the DC converter can be reduced.

In a preferred mode, the switch means comprises a diode. By doing so, control of the switch means can be omitted, and the circuit configuration can be simplified.

In a preferred mode, the potential drop detecting means compares the potential of the battery with a predetermined potential corresponding to the predetermined level and outputs a comparison result to the power transmission control means. By doing so, it is possible to reliably carry out the necessary operation.

In a preferred mode, the potential drop detecting means, based on the input information about the operation of the engine starter, outputs information about a period during which a potential drop of a predetermined level or more of the battery occurs when the engine is started. Then, the power transmission control means operates the DC-DC converter and stops the power transmission of the switch means during the period. With this configuration, a circuit including a comparator for voltage comparison is not required, so that the circuit configuration can be simplified.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The preferred embodiments of the present invention will be described with reference to the following examples.

[0016]

[Embodiment 1] A power supply device for an automobile of Embodiment 1 will be described below with reference to the circuit diagram shown in FIG.

(Circuit configuration) 1 is a battery, 2 is an electric double layer capacitor (hereinafter, simply referred to as a capacitor), 3 is an electric load (second load) such as headlight, 4 is a control device, 5 is an engine starting device ( First load), 6 is an electric load (first load) such as a pump, 7 is a DC-DC converter, 8 is switch means, and 9 is the voltage of the battery 1 A / D.
It is a voltage detection device that converts and transmits to the control device 4, and may be built in the control device 4.

The positive terminal of the battery 1 supplies power to the engine starter 5 and the electric load 6 and is supplied from a power generator (not shown).

The DC-DC converter 7 transmits the electric power of the battery 1 to the electric load 3 and the capacitor 2 at a predetermined step-up ratio or a desired step-up ratio controlled by the controller.

The switch means 8 comprises a two-terminal switch or a three-terminal switch for intermittently controlling the connection between the high level terminal of the battery 1 and the high level terminals of the electric load 3 and the capacitor 2.

The control unit 4 comprises a power management electronic control unit for controlling the automobile power supply unit shown in FIG. 1, and based on a command from a vehicle electronic control unit (not shown), an engine starting unit 5 and a DC-DC converter. 7, switch means 8
Are in control.

The electric loads 3 and 6 are set to the same rated voltage. Further, the voltage detection device 9 may be configured to output the average voltage of the immediately preceding predetermined period to the control device 4. (Operation) The basic control operation of the vehicle power supply device performed by the control device 4 will be described below.

When the voltage of the battery 1 input from the voltage detection device 9 drops below a predetermined value, the control device 4 turns off the switch means 8 and activates the DC-DC converter 7, so that the voltage of the battery 1 becomes a predetermined value. When it recovers to the value or more, the switch means 8 is turned on and the DC-DC converter 7 is stopped. In this embodiment, the step-up ratio of the DC-DC converter 7 is set to a value that can drive the electric load 3 at the rated voltage despite the voltage drop of the battery 1.

Although the step-up ratio of the DC-DC converter 7 is set to a constant value in this embodiment, the terminal voltage of the capacitor 2 is monitored to monitor the terminal voltage of the capacitor 2 to the rated value of the electric load 3. The feedback control may be performed at a constant level set near the voltage.

In this way, the DC voltage is applied only during the period when the terminal voltage of the battery 1 is greatly reduced due to engine start or the like.
Since it is sufficient to drive the DC converter 7, DC-DC
It is not necessary to design the DC-DC converter 7 to have a large size and large capacity in order to prevent the converter 7 from operating for a long time and gradually increasing its temperature.
Can be made smaller and lighter to reduce the manufacturing cost.

Further, even if the terminal voltage of the battery 1 is greatly reduced, the electric load 3 is supplied with electric power through the DC-DC converter 7 that operates in a step-up manner.
The capacity of the capacitor 2 may be sufficient to reduce the voltage fluctuation due to the switching of the power transmission path between the DC converter 7 and the switch means 8, and it is possible to realize the reduction in size and weight of the capacitor 2 that increases the space and weight. Of course, a small capacity battery may be used instead of the capacitor 2.

Further, since the operating time of the DC-DC converter 7 which generally has a large internal loss and low power transmission efficiency can be shortened, it is possible to improve the fuel consumption and simplify the cooling system of the DC-DC converter 7. Becomes

The above control operation is shown in the flow chart of FIG. Since the flow chart in Figure 5 is clear,
Detailed description thereof will be omitted. (Modification) Modifications are shown in FIGS.

In FIG. 2, a diode as a two-terminal switch is used as the switch means 8. The loss due to the forward voltage drop of the diode 8 is DC-D in the power supply device for the vehicle which is normally operated at the rated voltage of 12 V or more.
It is smaller than the C converter 7, and as a result, it is possible to improve fuel efficiency as compared with the case where the DC-DC converter 7 is always operated without providing the switch means 8. Also, the control becomes simple.

In FIG. 3, a relay or a magnet switch is used as the switch means 8. Fuel consumption can be further improved as compared with a diode.

In FIG. 4, a field effect transistor (FET) is used as the switch means 8. Fuel consumption can be further improved as compared with a diode. It should be noted that an IGBT or SIT may be used as the switch means 8 instead of the field effect transistor (FET).

Although the switching means 8 and the DC-DC converter 7 are switched in the above embodiment, the discharge load of the capacitor 2 at the time of switching is made by overlapping the power transmission period or the operating period of both for a predetermined period. May be reduced, and in addition, the DC-D
The C converter 7 may be operated. In this case, since the transmission power of the DC-DC converter 7 can be reduced by the amount of the current shunted through the switch means 8, D
The total power loss of the C-DC converter 7 and the switching means 8 can be reduced, and the fuel consumption can be improved. (Modification) Each modification of the control operation will be described below with reference to FIGS. 6 to 9.

In the modification shown in FIG. 6, instead of detecting the voltage drop of the battery 1 as described above, a predetermined time T has arrived from the time when the signal for instructing the engine start or the command or signal corresponding to the start of the engine starting motor is received. Only, the switch means 8 is turned on and the DC-DC converter 7 is turned off. The predetermined time T is set to a time sufficient for the generator to charge the battery 1 and recover the terminal voltage of the battery 1 until a voltage of a magnitude allowed by the electric load 3 is applied after the engine start is completed. Has been done. By doing so, the control circuit can be simplified.

In the modification shown in FIG. 7, instead of detecting the voltage drop of the battery 1 described above, the engine start is completed from the time when the signal for instructing the engine start or the command or signal corresponding to the start of the engine starting motor is received. The switch means 8 is turned on and the DC-DC converter 7 is turned off until the arrival of the signal indicating ".

The modification shown in FIG. 8 is a modification of the embodiment shown in FIG. 6 applied to the embodiment shown in FIG. 2, and the modification shown in FIG. 9 is a modification applied to the embodiment shown in FIG. It was done and the purpose is the same.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an automobile power supply device of the present invention.

FIG. 2 is a circuit diagram showing a modification of the device of FIG.

FIG. 3 is a circuit diagram showing a modification of the device of FIG.

FIG. 4 is a circuit diagram showing a modification of the device of FIG.

5 is a flowchart showing a control operation of the apparatus of FIG.

FIG. 6 is a flowchart showing a modification of the control operation of FIG.

FIG. 7 is a flowchart showing a modification of the control operation of FIG.

8 is a flowchart showing a modification of the control operation of FIG.

9 is a flowchart showing a modification of the control operation of FIG.

[Explanation of symbols]

1 battery 2 capacitors 3 Electric load (second load) 4 Control device (power transmission control means, voltage drop detection means)) 5 Engine starter (first load) 6 Electric load (first load) 7 DC-DC converter 8 switch means 9 Voltage detector

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Claims (6)

[Claims] 1. A battery that includes an engine starter and supplies power to a first load having a large voltage drop allowance ratio; and a DC-DC converter that is supplied from the battery side and sends power to a second load that has a small voltage drop allowance ratio. Switch means for transmitting power from the battery to the second load without passing through the DC-DC converter, voltage drop detection means for detecting information on voltage drop of the battery, and the switch when the voltage drop of the battery is not detected Means for permitting the power transmission through the means, stopping the power transmission through the switch means and detecting the voltage drop of the battery, and permitting the power transmission through the DC-DC converter. Power supply for automobiles. 2. The vehicle power supply device according to claim 1, further comprising a power storage unit having a capacity smaller than that of the battery in parallel with the second load. 3. The vehicle power supply device according to claim 1, wherein the power transmission control means stops the operation of the DC-DC converter when a voltage drop of the battery is not detected. 4. The vehicle power supply device according to claim 1, wherein the switch means is a diode. 5. The power supply device for an automobile according to claim 1, wherein the potential drop detecting means compares the potential of the battery with a predetermined potential corresponding to the predetermined level, and outputs the comparison result to the power transmission control. A power supply device for an automobile, which is characterized by outputting to a means. 6. The power supply device for an automobile according to claim 1, wherein the potential drop detecting means is above a predetermined level of the battery when the engine is started, based on the inputted information on the operation of the engine starting device. A power supply device for an automobile, wherein information on a period in which a potential drop occurs is extracted, and the power transmission control unit operates the DC-DC converter and stops power transmission to the switch unit during the period.