Charging device

Abstract

The present specification provides a charging device that can adjust the output in accordance with the performance of the power source. [Solution] The charging device disclosed in this specification is connected between a power source and a battery. The charging device (1) increases the output current at or below the upper limit of the current increase rate that the power source can output. Furthermore, the charging device (2) limits the output current to or below the upper limit of the current that the power source can output. The charging device disclosed in this specification can adjust the output in accordance with the performance of the power source (upper limit of the current increase rate and upper limit of the current).

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a charging device connected between a power source and a battery. [Background technology]

[0002] There is known an electric vehicle that uses a circuit of an inverter's switching elements and an electric motor's stator coil as a voltage converter to step up or step down the voltage of a power supply and output it to a battery (see, for example, Patent Document 1). In this electric vehicle, the inverter (switching elements) and electric motor (stator coil) function as a charging device. In the following, for ease of explanation, the "electric motor" may be simply referred to as the "motor."

[0003] Furthermore, Patent Document 2 discloses an electric vehicle having a first battery and a second battery. When driving the motor, the first battery and the second battery are connected in series. When charging the battery with a power source external to the electric vehicle, the first battery and the second battery are connected in parallel. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-184947 [Patent Document 2] Japanese Patent Application Publication No. 2019-118221 Summary of the Invention [Problem to be solved by the invention]

[0005] A charging device sets a target voltage or current suitable for charging a battery and adjusts the output of the charging device to match the target value. However, if the target value is set to exceed the performance of the power supply, the output of the charging device may not be able to match the target value. This specification provides a charging device that can adjust the output to match the performance of the power supply. [Means for solving the problem]

[0006] The charging device disclosed in this specification is connected between a power source and a battery. The charging device increases the output current at a rate equal to or less than the upper limit of the current increase rate that the power source can output. Furthermore, the charging device limits the output current to be equal to or less than the upper limit of the current that the power source can output. The charging device disclosed in this specification can adjust the output to match the performance of the power source.

[0007] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a circuit diagram of the charging device according to the embodiment. [Figure 2] 4 is a flowchart of charging control executed by the charging device. DETAILED DESCRIPTION OF THE INVENTION

[0009] A charging device 2 according to an embodiment will be described with reference to the drawings. Fig. 1 is a circuit diagram of the charging device 2. The positive electrode of a power source 70 is connected to an input terminal 2a of the charging device 2, and the positive electrode of a battery 3 is connected to an output terminal 2b. The charging device 2 is provided with a ground 9, and the negative electrode of the power source 70 and the negative electrode of the battery 3 are connected to the ground 9. The charging device 2 can adjust the output current of the power source 70 and output it from the output terminal 2b to charge the battery 3.

[0010] The charging device 2 is a step-up / step-down converter that can make the voltage (output voltage) at the output terminal 2b higher or lower than the voltage (input voltage) at the input terminal 2a. The charging device 2 includes a first switching element 12, a second switching element 22, diodes 13, 14, 23, 24, a reactor 31, capacitors 15, 25, voltage sensors 5, 6, a current sensor 4, and a controller 7. For convenience, the "switching element" will be referred to as the "SW element" below.

[0011] A first SW element 12 is connected between the input terminal 2a and one end 31a of the reactor 31, and a diode 13 is connected in anti-parallel to the first SW element 12. A diode 14 is connected between one end 31a of the reactor 31 and ground 9. When the first SW element 12 is turned on, it passes current from the input terminal 2a to the reactor 31, and when it is turned off, it does not pass current. Diodes 13 and 14 always pass current from ground 9 to the input terminal 2a, but do not pass current in the reverse direction. A capacitor 15 is connected between the input terminal 2a and ground 9.

[0012] A second SW element 22 is connected between the ground 9 and the other end 31b of the reactor 31, and a diode 23 is connected in anti-parallel to the second SW element 22. A diode 24 is connected between the other end 31b of the reactor 31 and the output end 2b. When the second SW element 22 is turned on, it passes current from the reactor 31 to the ground 9, and when it is turned off, it does not pass current. The diodes 23 and 24 always pass current from the ground 9 to the output end 2b, but do not pass current in the reverse direction. A capacitor 25 is connected between the output end 2b and the ground 9.

[0013] The charging device 2 is equipped with voltage sensors 5 and 6 and a current sensor 4. Measurement values ​​of these sensors are sent to a controller 7. The voltage sensor 5 measures the voltage (input voltage) applied to the input terminal 2a, the voltage sensor 6 measures the voltage (output voltage) output from the output terminal 2b, and the current sensor 4 measures the current (output current) output from the output terminal 2b. In other words, the controller 7 can know the input voltage, output voltage, and output current.

[0014] 1 is well known, and when the second switching element 22 is fixed to OFF and the first switching element 12 is turned on and off by a PWM signal with an appropriate duty ratio, the output voltage drops relative to the input voltage. Also, when the first switching element 12 is fixed to ON and the second switching element 12 is turned on and off by a PWM signal with another appropriate duty ratio, the output voltage rises relative to the input voltage. In other words, the charging device 2 is a buck-boost converter that can raise and lower the output voltage relative to the input voltage.

[0015] If the output voltage is made slightly higher than the voltage of the battery 3, current will flow from the power supply 70 to the battery 3. If the output voltage is further increased, more current will be supplied to the battery 3. If the output voltage is decreased, less current will be supplied to the battery 3. The controller 7 adjusts the output voltage so that the current supplied to the battery 3 (i.e., the output current of the charging device 2) follows the target current value. As mentioned above, the controller 7 can adjust the output voltage by the duty ratio of the PWM signal provided to the first switching element 12 or the second switching element 22.

[0016] The controller 7 and the power supply 70 can communicate and exchange information with each other via a communication line 40. The communication line 40 may be wireless. The communication line 40 may be the Internet. The controller 7 acquires the current increase rate upper limit and the current upper limit from the power supply 70 via the communication line 40. The current increase rate upper limit means the upper limit of the current increase speed that the power supply 70 can output. The current upper limit means the upper limit of the current that the power supply 70 can output.

[0017] FIG. 2 shows a flowchart of the charging process executed by the controller 7. As described above, the controller 7 first acquires information on the upper limit of the current increase rate and the upper limit of the current from the power supply 70 (step S2). Next, the controller 7 determines the target value of the output current (step S3). The controller 7 sets the current target value with reference to the previous target value so that the output current gradually increases from zero over time. The target value of the output current at the start of charging is zero. In step S3, the controller 7 sets the current target value so that the output current increases as quickly as possible, without taking into account the upper limit of the current increase rate of the power supply 70. Here, "this time" and "previous time" refer to "this time" and "previous time" in the control cycle of the controller 7.

[0018] Next, the controller 7 compares the current target value with the current upper limit value (step S4). If the current target value is equal to the current upper limit value, the controller 7 adjusts the output voltage so that the output current follows the target value (step S4: YES, S7). As mentioned above, increasing the output voltage increases the output current, and decreasing the output voltage decreases the output current.

[0019] If the current target value is not equal to the current upper limit (in other words, if the current target value has not reached the current upper limit), the controller 7 compares the difference (current increment) between the current target value and the previous target value with the current increase rate upper limit (step S5). If the current increment does not exceed the current increase rate upper limit, the controller 7 adjusts the output voltage so that the output current follows the target value (step S5: NO, S7).

[0020] If the current increment exceeds the upper limit of the current increase rate, the controller 7 changes the current target value to "the previous target value + the upper limit of the current increase rate" and controls the output voltage so that the output current follows the target value (steps S5: YES, S6, S7).

[0021] In the process of step S5, more precisely, the controller 7 compares the value obtained by dividing the current increment by the control period of the controller 7 with the current increase rate upper limit. If the value obtained by dividing the current increment by the control period exceeds the current increase rate upper limit, the controller 7 changes the current target value to "previous target value + current increase rate upper limit × control period." This is to align the current increase rate upper limit with the time interval of the current increase.

[0022] The controller 7 repeats the processes from steps S3 to S7 until the capacity of the battery 3 reaches full charge (step S8: NO). When the capacity of the battery 3 reaches full charge, the controller 7 ends the process (step S8: YES, END). When ending the process, the controller 7 sends an output stop command to the power supply 70.

[0023] Through the above processing, the controller 7 (charging device 2) achieves the following effects: (1) The charging device 2 can increase the output current at or below the upper limit of the current increase rate that the power supply 70 can output. (2) The charging device 2 can suppress the output current to or below the upper limit of the current that the power supply 70 can output. In other words, the charging device 2 can adjust the output current in accordance with the performance of the power supply 70.

[0024] Here are some points to note regarding the technology described in the embodiments. The circuit in FIG. 1 is an example of a charging device 2. The charging device 2 may be a current regulator capable of adjusting the output current to any desired magnitude. Alternatively, a charging device may be realized using a dual inverter configuration in which one end of a stator coil of an electric motor is connected to the AC terminal of a first inverter, and the other end is connected to the AC terminal of a second inverter. It is known that a circuit combining an inverter's switching element and a stator coil can be used as a voltage converter. A configuration in which an inverter is connected to each end of a stator coil is equivalent to a device in which three buck-boost converters shown in FIG. 1 are connected in parallel.

[0025] The expression "fixing an SW element on" is equivalent to the expression "closing an SW element," which means electrically connecting a device connected to each end of the SW element. The expression "fixing an SW element off" is equivalent to the expression "opening an SW element," which means electrically disconnecting a device connected to each end of the SW element.

[0026] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0027] 2: Charging device 3: Battery 4: Current sensor 5, 6: Voltage sensor 7: Controller 9: Ground 12, 22: Switching element 13, 14, 23, 24: Diode 15, 25: Capacitor 40: Communication line 70: Power supply

Claims

[Claim 1] A charging device connected between a power source and a battery, which increases an output current at a rate equal to or less than an upper limit of the current increase rate that the power source can output, and which keeps the output current equal to or less than the upper limit of the current that the power source can output.

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