JP2011091889A - Charging device - Google Patents

Abstract

A charging device that accurately determines full charge and efficiently has a small physique.
A transistor, which is a switching element for charging a battery by converting AC power to DC power, is switched at a small frequency SF1 and large power Wb1 until the storage capacity SOC reaches a threshold Sref near full charge. Then, after the battery capacity SOC reaches the threshold value Sref or more, the transistor is switched with a large frequency SF2 and the battery is charged with a small electric power Wb2. As a result, the charging current Ib has a relatively large current pulsation (ripple) until the storage capacity SOC reaches the threshold value Sref or more, but the power conversion efficiency can be increased, and the storage capacity SOC reaches the threshold value Sref or more. After that, although the power conversion efficiency is low, only a small current pulsation (ripple) is generated in the charging current Ib, so that full charge can be more appropriately determined.
[Selection] Figure 3

Description

  The present invention relates to a charging device, and more particularly, to a charging device that charges a secondary battery using AC power.

  Conventionally, as this type of charging device, one that gradually reduces the charging current as the secondary battery approaches full charge, one that reduces the charging power when the cell voltage exceeds a preset maximum set voltage, etc. Has been proposed (see, for example, Patent Document 1 and Patent Document 2). These charging devices suppress overcharging of the secondary battery by the above-described control and attempt to make the charging of the secondary battery as close to full charge as possible.

Japanese Patent Laid-Open No. 10-241746 JP 2009-44946 A

  In a charging device that charges a secondary battery by converting AC power to DC power by switching the switching element, current pulsation (ripple) is generated due to switching of the switching element, so that the secondary battery is fully charged properly. In this case, it is necessary to use a filter that is charged at a high switching frequency or has a large effect of reducing current pulsation. However, if charging is performed using a high switching frequency, switching loss increases, and the effect of reducing current pulsation is obtained. If a big filter is used, the weight and physique of a charging device will become large.

  The main purpose of the charging device of the present invention is to accurately determine full charge and to efficiently make the device small in size.

  The charging device of the present invention employs the following means in order to achieve the main object described above.

A charging device for charging a secondary battery using AC power,
Power conversion supply means for converting alternating current power into direct current power by switching the switching element and supplying the secondary battery;
Charging current detecting means for detecting a charging current when charging the secondary battery;
Voltage detection means for detecting a voltage when charging the secondary battery;
When it is determined based on the detected charging current and / or the detected voltage that the state of the secondary battery has not reached a predetermined state set in advance as a state near full charge, the frequency is equal to or lower than the first frequency. AC power is converted into DC power by switching the switching element according to frequency, and the power conversion supply means is controlled so that the secondary battery is charged with power equal to or higher than the first power, and the state of the secondary battery Is determined to have reached the predetermined state, AC power is converted to DC power by switching the switching element at a frequency equal to or higher than a second frequency greater than the first frequency, and less than the first power. Control means for controlling the power conversion supply means so that the secondary battery is charged with electric power;
It is a summary to provide.

  In the charging device of the present invention, the state of the secondary battery is set to a predetermined state set in advance as a state near full charge based on the charging current when charging the secondary battery and the voltage when charging the secondary battery. When it is determined that the power does not reach, the AC power is converted to DC power by switching of the switching element at a frequency equal to or lower than the first frequency, and the secondary battery is charged with power equal to or higher than the first power. And when it is determined that the state of the secondary battery has reached a predetermined state, AC power is converted into DC power by switching the switching element at a frequency equal to or higher than a second frequency that is greater than the first frequency. The power conversion supply means is controlled so that the secondary battery is charged with power less than one power. That is, by charging the secondary battery using a relatively low frequency equal to or lower than the first frequency until the secondary battery reaches a predetermined state near full charge, the secondary battery is efficiently reduced with reduced switching loss. After the secondary battery reaches a predetermined state in the vicinity of full charge, the secondary battery is charged using a relatively high frequency equal to or higher than the second frequency, thereby suppressing current pulsation. The full charge of the secondary battery can be accurately determined. In addition, since only the switching frequency is changed, the weight and size of the device do not increase. As a result, it is possible to accurately determine full charge and to efficiently make the apparatus small in size.

It is a block diagram which shows the outline of a structure of the charging device 20 as one Example of this invention. It is a flowchart which shows an example of the charge control routine performed by the electronic control unit 30 of an Example. It is explanatory drawing which shows an example of the time change of electrical storage capacity SOC, charging electric power Wb, switching frequency SF, charging current Ib, and charging loss when charging the battery.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of a charging device 20 as an embodiment of the present invention. The charging device 20 according to the embodiment is mounted on, for example, an electric vehicle or a hybrid vehicle, and converts the electric power from an external power source (for example, a household power source (AC100V)) 10 into a direct current to supply electric power for traveling. Is configured as a charging device for charging a battery 14 (for example, a lithium ion secondary battery), and converts the AC power from the plug 22 connected to the socket 12 of the external power supply 10 and the external power supply 10 into DC power. AC / DC converter 24, smoothing capacitor C1 for smoothing DC power from AC / DC converter 24, voltage transformer 26 for transforming the voltage of DC power from AC / DC converter 24, and DC power after transformation The voltage Vb between the terminals of the battery 14 and the smoothing capacitor C2 for smoothing, the relay 28 for connecting and disconnecting the battery 14 and the terminal of the battery 14 is detected. It includes a voltage sensor 40, a current sensor 42 for detecting a charging current Ib of the battery 14, the electronic control unit 30 for controlling the charging device 20, the.

  The AC / DC converter 24 is configured as a well-known AC / DC converter, and includes four diodes D1 to D4 connected in series to the positive electrode bus 23a and the negative electrode bus 23b of the power line 23 in pairs. The diodes D1 to D4 connected in series and the external power supply 10 are connected in parallel to the two coils L1 and L2 and the diodes D2 and D4 on the negative electrode bus 23b side in parallel. This is constituted by two transistors T2 and T4.

  The voltage transformer 26 is configured as a well-known DC / DC converter, and transistors T5 to T8 are connected in series in pairs so that they are on the source side and the sink side with respect to the positive electrode bus 23a and the negative electrode bus 23b. Four diodes D5 to D8 connected in parallel in the opposite direction to the transistors T5 to T8, a transformer TR having a primary terminal connected to a connection point of each pair of the transistors T5 to T8, and a secondary of the transformer TR The four diodes D9 to D12 are connected to the terminal on the side and rectify AC power transformed by the transformer TR.

  The electronic control unit 30 is configured as a microprocessor centered on the CPU 32. In addition to the CPU 32, a ROM 34 for storing a processing program, a RAM 36 for temporarily storing data, an input / output port and a communication port (not shown), Is provided. The voltage Vb between the terminals of the battery 14 from the voltage sensor 40 and the charging current Ib of the battery 14 from the current sensor 42 are input to the electronic control unit 30 via the input port. The drive signal to the relay 28, the switching signals to the transistors T2 and T4 of the AC / DC converter 24, the switching signals to the transistors T5 to T8 of the voltage transformer 26 are output via the output port.

  Next, operation | movement of the charging device 20 of the Example comprised in this way is demonstrated. FIG. 2 is a flowchart illustrating an example of a charging control routine executed by the electronic control unit 30 when the battery 14 is charged by the charging device 20 of the embodiment. This routine is executed when the plug 22 is connected to the socket 12 of the external power source 10 and the relay 28 is turned on to start charging the battery 14.

  When the charging control routine is executed, the electronic control unit 30 first inputs the charging current Ib of the battery 14 from the current sensor 42 and the voltage Vb between the terminals of the battery 14 from the voltage sensor 40 (step S100). Based on the charging current Ib and the voltage Vb, the storage capacity SOC as a percentage of the capacity stored in the battery 14 is calculated (step S110). Here, the storage capacity SOC is calculated by accumulating the charging current Ib with the storage capacity SOC at the start of charging, or converted by the voltage Vb between the terminals of the battery 14, and so on. It can be calculated by a technique.

  Subsequently, the calculated storage capacity SOC is compared with a preset threshold value Sref (for example, 95%) as a value near the full charge of the battery 14 (step S120). When the storage capacity SOC is less than the threshold value Sref, a relatively small frequency SF1 is set as the switching frequency SF of the transistors T2, T4, T5 to T8 (step S130), and a relatively large power Wb1 is set as the charging power Wb ( In step S140, the transistors T2, T4, T5 to T8 are switched at the set switching frequency SF, and the transistors T2, T4, T5 to T8 are controlled to be charged by the set charging power Wb (step S170). ), The storage capacity SOC is compared with a threshold value Sfull (for example, 99%, etc.) set in advance to determine whether the battery 14 is fully charged (step S180). Now, since it is considered that the storage capacity SOC is less than the threshold Sref near full charge, it is determined that the storage capacity SOC is less than the threshold Sfull, and the process returns to the input processing of the charging current Ib and the voltage Vb in step S100. When the storage capacity SOC continues in a state of less than the threshold value Sref, the processes of steps S100 to S140, S170, and S180 described above are repeatedly executed. That is, until the storage capacity SOC reaches the threshold value Sref or more due to charging of the battery 14, the transistors T2, T4, T5 to T8 are switched with the relatively small frequency SF1 as the switching frequency SF, and the relatively large power Wb1 as the charging power Wb. 14 is charged.

  When the battery 14 is charged and the storage capacity SOC reaches the threshold value Sref or more, the switching frequency SF of the transistors T2, T4, T5 to T8 is set to a frequency SF2 larger than the frequency SF1 (step S150), and the charging power A power Wb2 smaller than the power Wb1 is set as Wb (step S160), and the transistors T2, T4, T5-T8 are switched at the set switching frequency SF so that the battery 14 is charged by the set charging power Wb. T4, T5 to T8 are subjected to switching control (step S170), the storage capacity SOC is compared with a threshold value Sfull set in advance to determine whether the battery 14 is fully charged (step S180), and the storage capacity SOC is less than the threshold value Sfull. Sometimes step S10 Returning to the input processing of the charging current Ib and the voltage Vb, when the storage capacity SOC reaches the threshold value Sfull or more, it is determined that the charging is completed, and the connection by the relay 28 is released and the transistors T2, T4, T5 to T8 are switched. A charge termination process such as stopping is performed (step S190), and this routine is terminated.

  FIG. 3 is a diagram illustrating an example of a time change of the storage capacity SOC, the charging power Wb, the switching frequency SF, the charging current Ib, and the power conversion efficiency of the battery 14 when the battery 14 is charged by the charging control routine of the embodiment. FIG. As shown in the figure, while the storage capacity SOC is less than the threshold value Sref, the transistors T2, T4, T5 to T8 are switched with a relatively small frequency SF1 and the battery 14 is charged with a relatively large power Wb1, so that the charging current Ib Has a relatively large current pulsation (ripple), but the power conversion efficiency is high. On the other hand, when the storage capacity SOC exceeds the threshold value Sref, the transistors T2, T4, T5 to T8 are switched at a relatively large frequency SF2 and the battery 14 is charged with a relatively small power Wb2, so that the power conversion efficiency is lowered. However, since only a relatively small current pulsation (ripple) occurs in the charging current Ib, the full charge of the battery 14 can be determined more appropriately.

  According to the charging device 20 of the embodiment described above, the battery 14 is charged by switching the transistors T2, T4, T5 to T8 at a relatively small frequency SF1 until the storage capacity SOC reaches the threshold value Sref or more. Although a relatively large current pulsation (ripple) occurs in the charging current Ib, a loss in charging the battery 14 can be reduced. Further, after the storage capacity SOC reaches the threshold value Sref or more, the transistors T2, T4, T5 to T8 are switched at a relatively large frequency SF2, so that charging loss increases but the charging current Ib has a relatively small current pulsation. (Ripple) only occurs, and the full charge of the battery 14 can be determined more appropriately. Thus, full charge of the battery 14 can be more appropriately determined without increasing the mass or physique of the charging device 20. Moreover, the battery 14 is charged with a relatively large power Wb1 until the storage capacity SOC reaches the threshold value Sref or more, and the battery 14 is charged with a relatively small power Wb2 after the storage capacity SOC reaches the threshold value Sref or more. The battery 14 can be charged quickly, and overcharging of the battery 14 can be suppressed. Therefore, in the charging device 20 of the embodiment, full charging can be accurately determined and the device can be efficiently small in size.

  In the charging device 20 of the embodiment, the transistors T2, T4, T5 to T8 are switched at a relatively small frequency SF1 and the battery 14 is charged with a relatively large power Wb1 until the storage capacity SOC reaches the threshold value Sref or more. After the capacity SOC reaches the threshold value Sref or higher, the transistors T2, T4, T5 to T8 are switched at a relatively large frequency SF2 and the battery 14 is charged with a relatively small power Wb2. The thresholds of two or more levels may be provided, and the transistors T2, T4, T5 to T8 may be switched by increasing the frequency in two or more stages as the storage capacity SOC increases, or the storage capacity SOC continuously. Transistors T2, T4, T5 at a frequency that increases as It may be used as those for switching the T8.

  Although the charging device 20 of the embodiment is mounted on an electric vehicle or a hybrid vehicle, it may not be mounted on an electric vehicle or a hybrid vehicle.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the AC / DC converter 24 and the voltage transformer 26 correspond to “power conversion supply means”, the current sensor 42 corresponds to “charging current detection means”, and the voltage sensor 40 corresponds to “voltage detection means”. Correspondingly, a relatively small frequency when the storage capacity SOC calculated based on the voltage Vb detected by the voltage sensor 40 and the charging current Ib detected by the current sensor 42 is less than a preset threshold Sref as being near full charge The transistors T2, T4, T5 to T8 are switched by SF1 and the battery 14 is charged by a relatively large power Wb1. After the storage capacity SOC reaches the threshold value Sref or more, the transistors T2, T4, T5 have a relatively large frequency SF2. AC / DC converter for switching T8 and charging battery 14 with relatively small power Wb2 Transistor T2 of 4 and the voltage transformer 26, T4, the electronic control unit 30 to execute the charging control routine of FIG controlling switching T5~T8 corresponds to a "control unit".

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of charging devices.

  10 external power supply, 12 socket, 14 battery, 20 charging device, 22 plug, 23 power line, 23a positive bus, 23b negative bus, 24 AC / DC converter, 26 voltage transformer, 28 relay, 30 electronic control unit, 32 CPU 34 ROM, 36 RAM, 40 voltage sensor, 42 current sensor, C1, C2 smoothing capacitor, D1-D12 diode, T2, T4, T5-T8 transistor, TR transformer, L1, L2 coil.

Claims (1)

A charging device for charging a secondary battery using AC power,
Power conversion supply means for converting alternating current power into direct current power by switching the switching element and supplying the secondary battery;
Charging current detecting means for detecting a charging current when charging the secondary battery;
Voltage detection means for detecting a voltage when charging the secondary battery;
When it is determined based on the detected charging current and / or the detected voltage that the state of the secondary battery has not reached a predetermined state set in advance as a state near full charge, the frequency is equal to or lower than the first frequency. The secondary battery is controlled by controlling the power conversion supply means so that the alternating current power is converted into the direct current power by switching of the switching element according to the frequency, and the secondary battery is charged with a power higher than the first power. When the state is determined to have reached the predetermined state, the alternating current power is converted into the direct current power by switching the switching element at a frequency equal to or higher than a second frequency higher than the first frequency, and the first power is converted to the first power. Control means for controlling the power conversion supply means so that the secondary battery is charged with power less than
A charging device comprising:

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