Battery charging device

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a battery charging device.

【0002】

[Conventional technology]

For example, an electric vehicle needs to be charged with a battery after traveling a certain distance. As a battery charger of this type, for example, Japanese Patent Application Laid-Open No. 6-343203 discloses a charger for an electric vehicle that automatically sets and charges a charging voltage and a current according to the type of battery. ing.

【0003】

Conventional battery chargers of this type, including the techniques described in the known literature described above, only include one charger. Therefore, the battery charging device must be operated in the entire span from the large output power (charging power) region required immediately after the start of charging to the region where charging progresses and the output power injected into the battery becomes small. ..

【0004】

However, battery chargers are generally designed for maximum efficiency at rated power output. This maximum efficiency cannot be maintained from the rated power output region to the low output power region of about 10% of the rated power output. Efficiency usually decreases in the low output power region.

【0005】

For this reason, in the conventional method that must be operated in the entire span from the high output power region to the low output power region, the charging efficiency deteriorates in the low output power region, and it takes a long time to charge. There was a problem that it would end up.

【0006】

[Problems to be Solved by the Invention]

An object of the present invention is to provide a battery charging device capable of improving charging efficiency and shortening charging time.

【0007】

[Means for solving problems]

In order to solve the above-mentioned problems, the battery charging device according to the present invention includes a plurality of chargers, and the output ends of the plurality of chargers are commonly connected.

【0008】

According to the battery charging device having the above configuration, it is possible to select and operate a charger having characteristics suitable for the type of battery or the charging state, so that the charging efficiency can be improved. For example, the first charger and the second charger are included, the first charger is operated in the low output power region, and the first charger and the second charger are operated in the high output power region. By operating the chargers in the above, the efficiency in the low output power region can be increased as compared with the case where a plurality of chargers are operated simultaneously in the entire output region.

【0009】

In addition, the first charger operates with higher efficiency than the second charger in the low output power region, and the second charger is more efficient than the first charger in the high output power region. It can also be selected to work.

【0010】

According to this configuration, the first charger can be operated in the low output power region, and the efficiency in the low output power region can be improved. In the high output power region, the first charger and the second charger are operated at the same time. As a result, it is possible to charge with high efficiency and shorten the charging time in the entire span from the large output power region required immediately after the start of charging to the region where charging progresses and the output power injected into the battery becomes small. It will be possible.

【0011】

Other objects, configurations and effects of the present invention will be described in more detail with reference to the accompanying drawings. The figure is just an example.

【0012】

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram of a battery charging device according to the present invention. The illustrated battery charger includes a plurality of n chargers 101-10n. The output ends of the chargers 101 to 10n are commonly connected. The commonly connected output end is connected to the output terminal 15. The output terminal 15 is guided to the battery 7 to be charged via the switch 11 and the like. The battery 7 is, for example, a main battery of an electric vehicle or the like. The main battery powers the wheel drive motor.

【0013】

The input side of each of the chargers 101 to 10n is connected in common, and power is supplied from the AC power supply 9 or the like via the input terminal 13. The chargers 101 to 10n generally have a function of converting AC power supplied from the AC power supply 9 into DC, and further converting it into DC having different voltage values by a DC-DC converter or the like and outputting the chargers 101 to 10n. In addition, it includes a control circuit that controls a DC-DC converter, an overvoltage protection circuit, and the like. As the charging method using the chargers 101 to 10n, either a constant current charging mode or a constant voltage charging mode may be adopted.

【0014】

According to the battery charger having the above configuration, it is possible to select and operate a charger having characteristics suitable for the type of battery 7 or the charging state from a plurality of n chargers 101 to 10n. Therefore, the charging efficiency can be improved.

【0015】

The number n of the chargers 101 to 10n is arbitrary, but for the sake of simplification of explanation and comprehension, two specific examples, the first charger 101 and the second charger 102, are used. The case where the above is provided will be described.

【0016】

In this case, for example, the first charger 101 is assumed to have a characteristic of operating with higher efficiency than the second charger 102 in the low output power region. The second charger 102 shall have characteristics such that it operates with higher efficiency than the first charger 101 in the high output power region.

【0017】

FIG. 2 is a diagram showing output characteristics when the first charger 101 and the second charger 102 are set as described above. The horizontal axis represents the charging time (h), and the vertical axis represents the output power (kW). The output power (kW) is the power output from the first charger 101 or the second charger 102, and is equivalent to the charging power received by the battery 7. The curve L11 shows the output characteristics (charging characteristics) of the battery charging device according to the present invention, and the curve L21 shows the output characteristics of the conventional battery charging device using one charger.

【0018】

First, when charging the battery 7, the first charger 101 and the second charger 102 are operated at the same time in a certain time region after the start of charging, which requires a large output power. In the case of FIG. 2, the first charger 101 and the second charger 102 are operated at the same time until the output power, which was 4 (kW) at t0 when charging is started, becomes 2 (kW) at t1. As a result, the battery 7 can be charged rapidly.

【0019】

Next, in the low output power region where the charging of the battery 7 has progressed, only the first charger 101 is operated. The second charger 102 stops the operation. In the case of FIG. 2, only the first charger 101 is operated and the second charger 102 is stopped from t1 when the output power becomes 2 (kW). Since the first charger 101 has good efficiency in the low output power region, it is possible to improve the charging efficiency in the low output power region. As a result, it is possible to charge with high efficiency and shorten the charging time in the entire span from the large output power region required immediately after the start of charging to the region where charging progresses and the output power injected into the battery becomes small. It will be possible. In the case of Fig. 2, the charging time that used to take up to t3 o'clock can be completed at t2 o'clock, which is shorter than that.

【0020】

Figure 3 is a graph showing the relationship between output power and efficiency. In the figure, the horizontal axis represents the output power (kW) and the vertical axis represents the efficiency (%). The curve L12 causes the first charger 101 and the second charger 102 to operate simultaneously in the high output power region of 2 (kW) or more, and the first charge in the low output power region of less than 2 (kW). This is a characteristic when only the device 101 is operated. The curve L22 is a characteristic when the first charger 101 and the second charger 102 are operated at the same time in the total output power region.

【0021】

As shown in the characteristic L12 of FIG. 3, when only the first charger 101 is operated in the low output power region of less than 2 (kW), the first charge that operates with high efficiency in the low output power region. It is possible to effectively demonstrate the characteristics of the device 101 and ensure high charging efficiency.

【0022】

On the other hand, even in the low output power region of less than 2 (kW), when the first charger 101 and the second charger 102 are operated at the same time, the characteristics of the first charger 101 are effectively exhibited. It cannot be made to do so, and the charging efficiency deteriorates.

【0023】

The battery charging device illustrated in FIG. 1 further includes a control circuit 3. The control circuit 3 controls the operation of the chargers 101 to 10n. More specifically, it includes a current detection detecting means 5 for detecting the output current I0 and an output voltage detecting means (not shown) connected to the output terminal 15. The control circuit 3 monitors the charging state of the battery 7 based on the detection signals supplied from the output current detecting means 13 and the output voltage detecting means. Then, the chargers 101 and 102 are controlled. For example, when the output current I0 is larger than a certain value and the output voltage V0 is low, a large output power is required, so the chargers 101 and 102 are controlled to operate at the same time.

【0024】

When the output current I0 is small and the output voltage V0 is low, the battery 7 has been charged, so only the first charger 101 is operated and the second charger 102 is controlled to stop the operation. To do.

【0025】

[Effect of the invention]

As described above, according to the present invention, it is possible to provide a battery charging device capable of improving charging efficiency and shortening charging time.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram of the battery charging device which concerns on this invention.

[Figure 2]

It is a figure which shows the output characteristic of the battery charging device which concerns on this invention in comparison with the output characteristic of the conventional battery charging device.

[Fig. 3]

It is a graph which shows the relationship between output power and efficiency.

[Explanation of symbols]

101 ~ 10n charger 7 battery