JPH05336611A - Electrical system for electric automobile - Google Patents

Abstract

PURPOSE:To realize downsizing and cost reduction of an electrical system for electric automobile by eliminating charger for capacitor in an inverter. CONSTITUTION:The electric system for electric automobile comprises an inverter 4 for driving a wheel driving AC motor 5 with a main battery 1 as power supply, a current smoothing capacitor 41 connected to DC side of the inverter 4, and a DC-DC converter 300 for charging an auxiliary battery 100 with the main battery 1 as power supply, wherein initial charging of the smoothing capacitor 41 is carried out through the DC-DC converter 300 at the time of starting the inverter 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric system of an electric vehicle in which an AC motor for driving a wheel is driven by an inverter using a battery as a power source.

[0002]

2. Description of the Related Art FIG. 3 shows an electric system of a known electric vehicle which uses a battery as a power source. In the figure, 1 is the main battery,
Reference numeral 2 is a main switch, 3 is a fuse, 4 is an inverter, and 5 is an AC motor for driving wheels. In an electric vehicle, wheels (not shown) are connected to the electric motor 5 via a speed reducer or the like. Now, the input current (DC current) of the inverter 4 becomes a current containing many harmonics. Since this harmonic current cannot flow in the main battery 1, it is necessary to connect a smoothing capacitor 41 in the immediate vicinity of the inverter 4 to absorb the harmonic current.

The problem here is when the inverter 4 is started. If the main switch 2 is closed at the time of start-up and the capacitor 41 is directly charged by the main battery 1, an excessive rush current may flow, and the fuse 3 may be blown or the main battery 1 or the capacitor 41 may be damaged. Therefore, the capacitor 41
To charge the charging resistor 22 and the switch 2 shown.
The parallel circuit 1 is connected to the main switch 2 in series and used. That is, the capacitor 41 is charged through the charging resistor 22 by closing the main switch 2 when the inverter 4 is started. Since this charging current has a value limited by the resistor 22, the above-mentioned influence on the device is eliminated. Then, after charging is completed, the switch 21 is closed to short-circuit the resistor 22 and the inverter 4 is operated.

Further, in FIG. 3, 110 is an auxiliary battery 1.
00 is a DC-DC converter that charges 00. In general, 12V is often used as the voltage value of the auxiliary battery 100, while the voltage value of the main battery 1 is generally 100V or more, and therefore DC-DC conversion by a converter is required. In addition, 200 is a DC load such as an illumination lamp connected to the auxiliary battery 100, and 120 is an auxiliary switch for the converter 110.

FIG. 4 shows a known example of the DC-DC converter 110. Reference numeral 111 is an inverter, the AC output of which is applied to the primary side of the insulating transformer 112, and the secondary side output of the insulating transformer 112 is input to the rectifier 113.
The DC output of the rectifier 113 is applied to the filter circuit 114, and the output thereof charges the auxiliary battery 100. When starting the electric vehicle, first, the auxiliary switch 120 is closed and the DC-DC converter 110 is operated to charge the auxiliary battery 100.

In the above-described known electric vehicle electric system, the input current of the inverter 4 reaches several hundred amperes. For this reason, not only the main switch 2 but also the switch 21 inserted in the main circuit is required to have a large current type capable of passing the above current. As described above, the charging resistor 2
It can be said that the switch 2 and the switch 21 in the main circuit are charging devices required only for initial charging of the capacitor 41. On the other hand, as is well known, since the electric system of an electric vehicle is equipped with an electric device mounted on a vehicle, it is strongly demanded that the electric system be a system with a small number of devices and that the electric device be small, lightweight and highly efficient. From this point of view, conventionally, charging devices such as the charging resistor 22 and the switch 21 inserted in the main circuit have been a cause of hindering the downsizing and cost reduction of the electric system.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a DC-DC converter for charging an auxiliary battery and an initial charging function of a smoothing capacitor of an inverter. The purpose of the present invention is to provide an electric system for an electric vehicle, which is capable of significantly reducing the size and weight of a charging device as well as reducing the price by providing the above.

[0008]

In order to achieve the above object, the present invention relates to a DC-to-DC converter from a main battery in an electric vehicle.
This was done paying attention to the fact that the auxiliary battery is charged by the DC converter. That is, the present invention is a DC
In the DC converter, in addition to the first charging circuit that charges the auxiliary battery, a second charging circuit that charges the smoothing capacitor only when the inverter is started is provided.

[0009]

When the electric vehicle is started, the DC-DC converter for charging the auxiliary battery first operates. As a result, the second charging circuit in the DC-DC converter also operates to charge the smoothing capacitor of the inverter. If charging of the smoothing capacitor is completed, the second charging circuit becomes unnecessary,
Completion of charging is detected by an appropriate means to stop the function of the second charging circuit.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of this embodiment, and the same components as those in FIG. 3 are designated by the same reference numerals. In FIG. 1, 300 is a DC-D for charging the auxiliary battery 100.
The converter 300 has a charging circuit that charges the smoothing capacitor 41 when the inverter 4 is started, and the output side of the charging circuit is the smoothing capacitor 41.
Connected to both ends of.

FIG. 2 shows the DC-DC converter 300.
The same components as those in FIG. 4 are designated by the same reference numerals. In FIG. 2, 301 is an inverter similar to the inverter 111, and the AC output side of this inverter 301 is connected to the primary side of the insulation transformer 302. The secondary side of the isolation transformer 302 is a rectifier 303
The DC output side of the rectifier 303 is connected to the filter circuit 304. Then, the filter circuit 304
The output side of is connected to the smoothing capacitor 41 to form a second charging circuit 305. The configuration of the first charging circuit 115 for charging the auxiliary battery 100 is the same as that in FIG.

Next, the starting of the electric vehicle according to this embodiment will be described. Similarly to the conventional case, when starting the inverter 4, first, the auxiliary switch 120 is closed. When the auxiliary switch 120 is closed, the first charging circuit 115 operates to charge the auxiliary battery 100. Similarly, the inverter 4
Inverter 30 of second charging circuit 305 only when starting
Activate 1. When the inverter 301 operates, the insulation transformer 302, the rectifier 303, and the filter circuit 304 operate to charge the smoothing capacitor 41. When the smoothing capacitor 41 is completely charged, the operation of the inverter 301 is stopped. Although the charging of the smoothing capacitor 41 is not shown, the voltage of the smoothing capacitor 41 is detected by a voltage detection circuit, or it is measured that a certain time has elapsed from the start of charging based on the charging time constant. Just go.

In the above embodiment, the case where the input of the second charging circuit 305 is taken from the main battery 1 has been described, but this input can also be taken from the output of the first charging circuit 115. In this case, the inverter 3 of the second charging circuit 305
01 and the isolation transformer 302 are rated for the first charging circuit 11
5 output may be matched.

[0014]

As described above, according to the present invention, the DC-DC converter for charging the auxiliary battery is provided with the initial charging function of the smoothing capacitor of the inverter. The required main circuit switch and charging resistor are no longer required. Therefore, it is possible to reduce the number of main circuit devices of the electric vehicle, and it is possible to reduce the size and weight of the vehicle-mounted device or the electrical equipment and the cost thereof.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a DC-DC converter in the embodiment of FIG.

FIG. 3 is a block diagram showing a conventional technique.

4 is a configuration diagram of a DC-DC converter in FIG.

[Explanation of symbols]

 1 Main Battery 2 Main Switch 3 Fuse 4 Inverter 5 Wheel Drive AC Motor 41 Smoothing Capacitor 100 Auxiliary Battery 120 Auxiliary Switch 200 DC Load 300 DC-DC Converter 301 Inverter 302 Insulation Transformer 303 Rectifier 304 Filter Circuit 305 Second Charging circuit

Claims (3)

[Claims] 1. An inverter for driving an AC motor for driving a wheel using a main battery as a power source, a current smoothing capacitor connected to the DC side of the inverter, and a DC-DC converter for charging an auxiliary battery using the main battery as a power source. An electric system of an electric vehicle, comprising: the DC-DC converter for initial charging of the capacitor when the inverter is started. 2. The electric system for an electric vehicle according to claim 1, wherein the DC-DC converter has a first charging circuit for charging the auxiliary battery and a second charging circuit for charging the current smoothing capacitor. 3. The electric system of the electric vehicle according to claim 2, wherein the second charging circuit is operated only when the inverter is started.